Detecting inhomogeneities in Caribbean and adjacent Caribbean temperature 1

data using sea surface temperatures 2

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T. S. Stephenson1, C. M. Goodess

2, M. R. Haylock

3, A. A. Chen

1 and M. A. Taylor

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1. Climate Studies Group Mona, Physics Department, The University of the West 9

Indies, Mona, Kingston 7, Jamaica, West Indies. 10

2. Climatic Research Unit, School of Environmental Sciences, University of East 11

Anglia, Norwich, Norfolk, NR4 7TJ, United Kingdom. 12

3. PartnerRe Ltd., P.O. Box 857, Bellerivestrasse 36, CH-8034, Zurich, Switzerland. 13

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Abstract 1

This study presents a systematic evaluation of the homogeneity of daily 2

surface temperature observations for the Caribbean and neighbouring regions on a 3

monthly timescale. The reference series are developed using adjacent sea surface 4

temperatures (SSTs). This novel approach is undertaken instead of the conventional 5

use of highly correlated nearby stations, given the sparse station network for the 6

Caribbean and adjacent Caribbean. The temperature data are from the regional climate 7

change workshops held for the Caribbean, and Central and Northern South America, 8

in 2001 and 2004 respectively, complemented with data from the National Climatic 9

Data Center, Caribbean Institute for Meteorology and Hydrology and Caribbean 10

meteorological stations. Correlations are used to explore the degree of association 11

between the maximum and minimum temperatures and SSTs, and homogeneity tests 12

are performed on their individual and difference series (e.g. maximum temperature 13

minus SSTs). The results suggest SSTs as a viable option for use in evaluating 14

homogeneity in the data sparse region of the Caribbean. Common statistically 15

significant change points identified across at least three stations are investigated using 16

composite analysis to determine links to large-scale atmospheric circulation patterns. 17

The study identifies two homogeneous periods from the analyses, i.e. 1970-92 and 18

1984-98, with the former used to reanalyze some extreme temperature trends for the 19

Caribbean and adjacent Caribbean. The results are found to be consistent with those 20

obtained from the 2001 Caribbean data workshop. 21

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1. Introduction 1

Socio-economic sectors within the Caribbean such as agriculture, fisheries and 2

tourism are inextricably linked to climate variability and change and are particularly 3

vulnerable to extreme events such as droughts, floods or temperature extremes 4

(Mahlung 2001). High quality daily data are necessary to assess the changes in 5

extremes that have occurred for the Caribbean and adjacent regions, and to make 6

projections regarding their occurrence in the future using statistical downscaling 7

techniques. To this end a data workshop was hosted in Kingston Jamaica in 2001 8

where daily precipitation and maximum and minimum temperatures across 30 stations 9

within the Caribbean, Belize and Florida (c.f. Figure 1) were brought together. The 10

workshop was invaluable in analyzing changes in climate extremes for the Caribbean 11

and adjacent Caribbean (i.e. Caribbean and neighbouring countries with a Caribbean 12

coastline found in a 55o – 90

oW and 5

o – 30

oN domain) over the 1958-1999 period 13

(Peterson et al. 2002 hereafter PTD). 14

PTD employed a variety of quality control (qc) procedures on the data 15

including checks for physically unreasonable values, unreasonably long consecutive 16

occurrences of the same value, daily maximum temperatures less than minimum 17

temperatures, imperial to metric conversion problems, extreme outliers and very long 18

zero precipitation spells (Peterson et al. 1998a). No specific homogeneity tests were 19

run. Instead there was a qualitative evaluation of the calculated climate extremes 20

indices for each station and those with obvious discontinuities were excluded from 21

subsequent analyses for the given variable. Similar workshops were held for Africa 22

(Easterling et al. 2003, Mokssit 2003, New et al. 2006), Central and South America 23

(Aguilar et al. 2005 hereafter APO, Vincent et al. 2005, Haylock et al. 2006), and 24

Asia (Zhang et al. 2005, Peterson 2005, Klein Tank 2006, Sensoy et al. 2007). 25

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The exclusion of specific homogeneity tests on the Caribbean data by PTD 1

may have been the result of the data sparsity across the Caribbean region. This paper 2

aims firstly to extend the work of PTD by attempting to systematically evaluate the 3

homogeneity of Caribbean surface temperature data. The surface temperature 4

observation network is essentially that used in PTD but has been expanded to include 5

additional data that were also available to the authors. Data from the National 6

Climatic Data Center, the Caribbean Institute for Meteorology and Hydrology, local 7

meteorological services, as well as data provided for the Central and northern South 8

America workshop (APO) are also utilized (c.f. Figure 1). 9

Even with the expanded dataset, the station density is still sparse and therefore 10

an impediment to the use of conventional homogeneity techniques which exploit 11

neighbouring stations (Peterson et al. 1998b). In light of this, the opportunity is taken 12

in this study to investigate the use monthly sea surface temperatures (SSTs) from the 13

1o-grid HadISST1 dataset (Rayner et al. 2003) to obtain reference series for each 14

station. That is, a reference time series is constructed by averaging SST gridpoint 15

values in 1o proximity to a given station. The difference series is then computed with 16

respect to both the maximum and minimum temperature series, and homogeneity 17

assessments are conducted using the RHTest Software (Wang and Feng 2004). This 18

approach is considered to be particularly useful for islands/coastal areas like the 19

Caribbean with a sparse network of daily temperature observations but where adjacent 20

SST gridded data are available. Additionally the use of the HadISST1 data provides a 21

high resolution independent dataset that correlates robustly with a number of station 22

observations in the Caribbean and adjacent Caribbean as shown in Section 3. As a 23

precursor to the primary analyses, quality checks on the surface temperature data are 24

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repeated using RClimDex (Zhang and Yang 2004) and an outlier test (described in 1

detail in Section 2). 2

We note that the comparison of surface station temperature observations with 3

SSTs or other gridded temperature dataset is not new in itself. The interannual 4

variations and trends of homogenized maximum, minimum and mean temperature 5

data have been examined in relation to SST and nighttime marine air temperature data 6

for the South Pacific islands (Folland et al. 2003, Folland et al. 1997) and New 7

Zealand (Folland and Salinger 1995). Rusticucci and Kousky (2002) compare 8

temperature observations from selected stations in Argentina with National Centers 9

for Environmental Prediction-National Center for Atmospheric Research (NCEP-10

NCAR) reanalysis (Kalnay et al. 1996) to determine how well statistics relating to 11

extremes in reanalysis 2-m temperatures correlate with observations. Kushnir (1994) 12

used land-based temperature observations surrounding the North Atlantic region to 13

verify the interdecadal signal that was evident in adjacent SSTs. However, in the 14

context of assessing the homogeneity of the surface temperature data, the proposed 15

method is a novel one or is at least not well documented in the literature. A review of 16

the conventional methodologies is found in Peterson (1998b). 17

The paper secondly attempts to investigate whether statistically significant 18

change points commonly identified across a number of stations, are linked to regional 19

climate change. These change points are identified from the homogeneity tests and are 20

time points where the statistical characteristics of the station series are significantly 21

different before and after. Synoptic conditions over the Atlantic and Pacific before 22

and after the change points are examined using NCEP reanalysis. This latter approach 23

is employed given the absence of available metadata for many of the stations used in 24

the study. 25

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Finally, a third aim of this study involves investigating whether some of the 1

trends identified over the Caribbean by PTD would hold true for the homogenized 2

data. A number of the indices of PTD are reanalysed and the results for a few of them 3

(maximum and minimum temperature above the 90th

percentile and below the 10th

4

percentile) are presented. 5

Section 2 describes data and statistical analyses, section 3 results of the quality 6

control procedures and homogeneity tests, section 4 synoptic relationships, section 5 7

some results of the reanalysed trends for the Caribbean and adjacent Caribbean and 8

section 6 discusses the primary findings. No adjustments of the data are attempted but 9

a homogeneous period is identified which may be exploited in further use of the data 10

for climate change studies for the Caribbean and adjacent Caribbean. This includes 11

additional trend analysis work or statistical downscaling as performed for north-12

eastern Mexico (Cavazos 1997) and some Caribbean islands (Chen et al. 2006), 13

especially in relation to the National Communications to the United Nations 14

Framework Convention on Climate Change. 15

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2. Datasets and Methods 17

2.1 Datasets 18

Daily maximum and minimum temperature data for forty-two stations in the 19

Caribbean, Florida, Central America and northern South America are investigated 20

(c.f. Figure 1 and Table 1). The Caribbean islands include the Bahamas, Barbados, 21

Cayman Islands, Cuba, Dominican Republic, Guadeloupe, Jamaica, Puerto Rico, St. 22

Lucia, St. Vincent and Trinidad. The Central American and northern South American 23

countries comprise Belize, Costa Rica, Guatemala, Honduras, Nicaragua, Panama and 24

Venezuela – all countries with a Caribbean coastline. The data are obtained from the 25

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Caribbean, and Central and northern South America daily data workshops (PTD, 1

APO), the National Climatic Data Center, Caribbean Institute for Meteorology and 2

Hydrology and local meteorological services1. The PTD and APO data largely span 3

1958-1999 and 1961-2003 respectively, while the other datasets span 1970-2006 (c.f. 4

Table 1). The presence of at least 80% nonmissing data was required before 5

homogeneity tests were applied to the stations. All stations are located in a 55o – 6

90oW and 5

o – 30

oN area. 7

SSTs are obtained from the HadISST1 dataset2 (Rayner et al. 2003). The 8

dataset is a combination of global SST and sea ice concentration recorded monthly on 9

1o latitude-longitude grids from 1871 to 2004. HadISST1 is constructed using reduced 10

space optimal interpolation and improves upon the representation of local SSTs in 11

comparison to previous global sea ice and SST (GISST) datasets: GISST1 (Parker et 12

al. 1995), GISST2 (Rayner et al. 1996) and GISST3. HadISST1 includes individual 13

ships’ observations from the Met Office Marine Data Bank and monthly median SSTs 14

from 1871-1995 from the Comprehensive Ocean-Atmosphere Data Set (COADS) 15

(Woodruff et al. 1987, 1998). The COADS has been validated over Caribbean waters 16

using correlations with independent temperature measurements off the coast of Puerto 17

Rico (Watanabe et al. 2002). 18

The monthly 2.5o gridded NCEP-NCAR reanalysis data (Kalnay et al. 1996) is 19

used to provide air temperature, divergent wind, vorticity and pressure vertical 20

velocity data3. A 30

oS-70

oN and 180

o-355

oE domain is extracted which covers the 21

tropical Atlantic and Pacific. NCEP-NCAR reanalysis data has been used by Wang 22

1 The PTD and APO datasets can be obtained by contacting michael.taylor@uwimona.edu.jm and

probando@racsa.co.cr respectively. Data are provided only after consultation with the national

meteorological services that provided the data. CIMH data requests can be made through their website

at www.cimh.edu.bb. NCDC data can be downloaded from ftp://ftp.ncdcngov/pub/data/ghcn/daily. 2 The HadISST data can be downloaded from http://hadobs.metoffice.com/hadisst/.

3 Data are provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA from their website at

http://www.cdc.noaa.gov/.

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(2002a,b) to isolate circulation cells over the Atlantic and Pacific and by Stephenson 1

et al. (2007) to relate similar circulation patterns to Caribbean winter rainfall 2

extremes. 3

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2.2 Method 5

2.2.1 Quality Control 6

PTD and APO conducted a series of quality control (qc) checks on the daily 7

surface temperature and precipitation data as previously outlined in Section 1. For 8

quality assurance the qc tests are repeated here using the RClimDex (version 1.0) 9

Software (Zhang and Yang 2004). The RClimDex qc procedure includes checks for 10

physically unreasonable values such as daily precipitation amounts less than zero or 11

daily maximum temperatures less than minimum temperatures. Additionally, values 12

that are greater than n standard deviations from the climatological mean for the day 13

(i.e. mean of all the January 1s, 2s, etc. respectively) are flagged, where n is a user 14

defined integer. Analyses were done using n values of four and five (Boyer and 15

Levitus 1994, Alexander et al. 2006). 16

Outliers greater than five standard deviations from the climatological mean of 17

the day were also isolated following variance comparisons with temperatures of the 18

surrounding three days, i.e., before and after the day being analysed. The day being 19

tested was excluded so as not to bias the calculation of the standard deviation. The 20

identified outliers were set to missing (-99.9) and manually checked, i.e. visually 21

compared with values of the surrounding days that may have also been flagged. This 22

allows for the identification a probable spell of some extreme weather events. 23

The latter outlier identification technique was more rapidly executed than the 24

RClimDex routine. The initial execution of the RClimDex tests using five standard 25

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deviations from the mean of the day yielded a single outlier in maximum temperature 1

for the Dominican Republic station and Puerto Rico (Utuado) in all the maximum and 2

minimum timeseries assessed. However, for the same stations, the second technique 3

in a single run, flagged twenty-seven outliers in maximum temperatures and two in 4

minimum temperatures for the Dominican Republic; and sixteen outliers in the 5

maximum temperature for Puerto Rico (Utuado). Albeit an iterative application of the 6

RClimDex tests would yield the same result. 7

A monthly timeseries of maximum and minimum temperatures respectively 8

was created from the quality-controlled daily data by averaging over days in a given 9

month. This is for comparison with the monthly SST data. The SST grid values in 1-10

degree proximity to a station are averaged to obtain a reference time series. 11

Anomalies of maximum temperature, minimum temperature and SSTs are then 12

calculated by removing the respective variable’s monthly climatology. A series of 13

plots are constructed and examined. These include: 1) anomalies of SST, maximum 14

and minimum temperatures; 2) difference series between SST and maximum and 15

minimum temperatures; 3) anomalies of the difference series and 4) standardized 16

values of the difference series. Anomalies of the difference series are calculated by 17

subtracting the monthly means of the difference series. This is done to remove the 18

seasonal cycle that was evident in the difference series. Each series is also 19

standardized by dividing by its monthly standard deviation. 20

The plots initially allowed easy identification of stations with very short 21

timeseries, i.e. less than approximately fifteen years, such as Puerto Rico (Lares) - 22

which was omitted from subsequent analyses. Secondly, the plots of the anomalous 23

SST, maximum and minimum temperatures provide a visual indication of the degree 24

of covariability among the timeseries. Correlation coefficients are computed between 25

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monthly SSTs and maximum and minimum temperature to quantify their linear 1

association. The 1970-1998 period is used given the essentially good data coverage 2

across datasets for this period. Statistical significance at the 95% level is assessed 3

using the random phase method (Ebisuzaki 1997) to allow for any serial correlation in 4

the series. SST timeseries that are well correlated with station observations, i.e., 5

greater than or equal to 0.70 (Malcher and Schönwiese 1987, Sala et al. 2000, Pielke 6

et al. 2007), are employed as reference series. Malcher and Schönwiese (1987) 7

explain that the correlations greater than or equal to 0.70 indicate that at least 50% of 8

the variability in the surface observations is captured by the reference series. 9

Finally the plots of the difference series anomalies help to identify any 10

divergence or differences in the behaviour of maximum and minimum temperatures 11

with respect to SSTs. 12

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2.2.2 Homogeneity Tests 14

The homogeneity tests are applied to all the individual monthly series, i.e., for 15

SST, maximum and minimum temperature timeseries. Peterson et al. (1998b) suggest 16

that this test in itself is problematic since any common change point identified here 17

could be caused by or masked by real climatic fluctuations. The homogeneity tests are 18

therefore also applied to the difference series anomalies which should better isolate 19

the effects of station inhomogeneities versus regional climate change (Peterson 20

1998b). This is done for those station series that are well correlated with SSTs (≥ 21

0.70). 22

The tests are conducted using the RHTest (version 0.95) Software (Wang and 23

Feng 2004). The RHTest is designed to detect multiple step change points that exist in 24

a timeseries based on the comparison of a two-phase regression model with a linear 25

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trend for the entire series (Wang 2003). Change points that are significant at the 99% 1

level are highlighted for further investigation, focusing on those that are common 2

across a number of stations. The plots are re-examined and composites of atmospheric 3

variables before and after the change point are constructed to evaluate whether the 4

identified change point is associated with any significant shifts in the climate signal 5

over the Pacific and Atlantic in relation to the Caribbean. Several studies have 6

established the link between Caribbean atmospheric circulation and climate 7

variability, and conditions over the Pacific and Atlantic (Chen et al. 1997; Taylor 8

1999, Giannini et al. 2000; Chen and Taylor 2002; Taylor et al. 2002, Spence et al. 9

2004, Ashby et al. 2005, Stephenson et al. 2007). This approach is employed given 10

the absence of metadata for many of the stations. 11

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2.2.3 Composites 13

We use composites to investigate commonly identified significant change 14

points and their possible links to changes in circulation patterns over the Caribbean 15

and adjacent regions. Difference maps are constructed between 5-year composites 16

before and after the year of the identified change points, i.e. if a breakpoint is 17

identified in 1983, composites of selected variables are calculated over 1978-1982 and 18

1984-1988, and then subtracted. The variables analysed are 1000 mb air temperature, 19

500 mb pressure vertical velocity, and divergent wind and vorticity at sigma levels 20

0.995 (surface) and 0.2101 (upper troposphere). Pressure vertical velocity and 21

divergent wind are used following Wang (2002a,b) who suggests these variables are 22

prerequisite to isolating atmospheric circulation cells. The divergent component of 23

wind is identified by the second component in the equation 24

Φ∇+∇×=+= Φ ψψ kvvv where ψ is the stream function and Φ is velocity 25

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potential. The first term represents the rotational component which, though the larger 1

term, is not essential for identifying atmospheric cells (Krishnamurti 1971, Wang 2

2002a, b). The pressure vertical velocity (VV) at 500 mb indicates the mean vertical 3

motion at the mid-tropospheric level. Significant differences between the 5-year 4

composites before and after the identified change points are assessed for the 95% and 5

99% significance levels using the Student’s t-test (Panofsky and Brier 1968, Knaff 6

1997). 7

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3. Results 9

3.1 Quality Control 10

Figure 2 shows the plots of anomalies of SSTs, maximum temperatures and 11

minimum temperatures for selected stations. The stations shown are representative of 12

the good agreement evident between variations of the surface temperature timeseries 13

and adjacent SSTs for most stations. Correlation coefficients calculated between 14

monthly SSTs and maximum and minimum temperatures for 1970-1998 are shown in 15

Table 2. The temperature-SST associations are particularly strong for the Bahamas, 16

Cayman Islands, Cuba (Casa Blanca), Dominican Republic, Florida, Guadeloupe, 17

Jamaica (Sangster), Puerto Rico, St. Lucia, and St. Vincent, where correlations of 18

0.71-0.93 are obtained for both maximum and minimum temperatures. Interestingly, 19

the relationship between Central American temperatures and adjacent SSTs appears to 20

be stronger with respect to minimum temperatures, as seen for Guatemala and 21

Honduras (Table 2). The strong correlations (≥ 0.70), imply that SSTs are good 22

candidates for reference series for many of the surface temperature observations in 23

this study and these series are retained. Additionally, in cases where a correlation of 24

0.65-0.69 is obtained for one of the temperature series and is at least 0.70 for the other 25

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series, both series are retained. There are some stations where neither maximum nor 1

minimum temperatures are well correlated with adjacent SSTs. These stations are 2

located in Belize - PSWGIA, Costa Rica, Honduras - Catacamas, Panama and 3

Venezuela. 4

Figure 2 also highlights some large temporal variations in the maximum and 5

minimum temperature anomalies. These are likely due to anomalous climatic 6

influences which in some cases are evident on a regional scale. For example, the large 7

negative minimum temperature anomaly evident for the Bahamas in January 1981 8

(c.f. Figure 2a) is also seen for Honduras (Figure 2b), Belize, Cuba, the Cayman 9

Islands, Guatemala, Honduras, Nicaragua and Florida (stations not shown). This is 10

consistent with anomalously low temperatures that were evident across the eastern 11

and southern United States and the Caribbean, as a result of several polar continental 12

air masses intruding into the region (Walker et al. 1982, Snedaker 1995). The ‘spikes’ 13

in the minimum temperature anomaly timeseries are primarily evident during the 14

boreal winter months (November-March). 15

Figure 3 shows plots of the anomalies (i.e. with the monthly mean removed) of 16

the difference series between SST and maximum and minimum temperatures 17

respectively for the same stations shown in Figure 2. The plots again indicate 18

convergence, i.e., similarity in the relationship between SSTs and maximum and 19

minimum surface temperatures at the different stations. This is versus the divergence 20

evident for the 1958-60 period for Ponce, Puerto Rico (Figure 3c). 21

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3.2 Homogeneity Results 1

3.2.1 SSTs, Maximum Temperature and Minimum Temperatures 2

Table 3 shows results of the homogeneity tests conducted on the individual 3

SST, maximum and minimum temperatures (see Section 2). The assessments reveal 4

no change points for SSTs adjacent to Bahamas, Florida and Cayman. Apart from 5

Cuba, these are the northern-most countries represented in the study. SSTs adjacent to 6

thirteen of the other nineteen countries indicate steps for 1970/71 of -0.24 to -0.80 oC 7

and for 1983/84 of -0.22 to -0.83 oC. (Negative change points indicate a shift towards 8

lower temperatures.) The change points are not significant at the 99% level, except in 9

1970/71 for Barbados, Guadeloupe, Panama, St. Lucia, St. Vincent, and Venezuela 10

(Tumeremo) – essentially the easternmost or southernmost stations in the study; and 11

in 1983 for Belize and Honduras. Other change point years are identified in 1973 and 12

1981. The significant change points noted, i.e., for 1970/71, and 1983, may be 13

consistent with variations in the tropical Atlantic meridional gradient mode, 14

characterized by oppositely signed SST anomalies in the tropical North Atlantic and 15

tropical South Atlantic. The mode was mainly positive for periods pre-1970 and 1976-16

1983 and negative during 1971-75 and 1984-89 (Wang 2002b). This is explored 17

further in Section 4. 18

Homogeneity tests on the maximum and minimum temperatures (Table 3) 19

indicate no step change points for Freeport (Bahamas), Husbands (Barbados), Grand 20

Cayman (Cayman Islands), Flores (Guatemala), Key West (Florida) and St. Vincent. 21

This is also the case with regard to maximum temperatures for PSWGIA (Belize), 22

David (Panama) and GFL Charles Airport (St. Lucia), and minimum temperatures for 23

Everglades (Florida). Significant change point years commonly identified across three 24

or more surface temperature observations are noted for 1976/77, 1979 and 1983/84. 25

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The 1976/77 and 1983/84 change point years are also consistent with phases of the 1

tropical Atlantic meridional gradient mode. The 1976/77 change point also coincides 2

with the 1976-77 abrupt climate shift in Pacific circulation centred in the Tropics 3

which significantly influenced subsequent El Niño evolutions (Trenberth 1990, 4

Trenberth and Hoar 1996, Zhang et al. 1997, Guilderson and Schrag 1998, Urban et 5

al. 2000). Additionally the Pacific/North Atlantic (PNA) teleconnection pattern which 6

describes the position, strength and orientation of a trough and ridge pattern over the 7

northern Pacific Ocean and North America shifted to a positive phase in 1976 8

(Schmidt 2003). These may suggest that some of the change points identified in the 9

individual series are related to changes in the climate system (Peterson et al. 1998b). 10

The 1976/77 and 1983/84 change points are oppositely signed with the latter being 11

negative. The 1976/77 change points are obtained for La Ceiba (Honduras), San Juan 12

(Puerto Rico) and Mene Grande and Guiria (Venezuela). The 1983/84 change points 13

are evident for Grantley Adams (Barbados), Catacamas (Honduras), and San Juan 14

(Puerto Rico). The 1979 change points are positive and are obtained for Fabio (Costa 15

Rica), Maiquetia Apt. Bolivar and La Carlota (Venezuela). 16

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3.2.2 Difference Series 18

The step change points evident in the difference series anomalies are listed in 19

Table 4. Firstly, it is noted that in most cases, there is consistency in the direction of a 20

change point (i.e. positive or negative) identified for a given year (± 1 year), in a 21

station’s maximum and minimum temperature timeseries. This is evident for Cuba, 22

Dominican Republic, Guadeloupe, Florida (Key West) and Puerto Rico (Ponce and 23

San Juan), with the Bahamas (Freeport), Jamaica (Worthy Park) and St. Lucia as the 24

exceptions. Additionally, although there is consistency within most stations, this is not 25

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necessarily the case across stations in different countries. For example, whereas 1

positive change points are identified for Cuba and Puerto Rico (San Juan) for 2

1981/82, they are negative for Dominican Republic and Florida (Key West). In this 3

case, the absence of any consistent spatial pattern given the difference in signs, 4

suggests that a regional climatic influence may not be an underlying cause. A re-5

examination of the plots (not shown) confirms this, in that, while there were 6

similarities in the distribution of values before and after the negative change points 7

identified for Dominican Republic and Florida (Key West), they were very dissimilar 8

with respect to the temporal patterns surrounding 1981/82 for both Cuba and Puerto 9

Rico (San Juan). 10

Significant change point years common across three or more stations are 11

identified mainly for 1968/69, 1970/71, 1979 and 1983. The 1968/69 steps are 12

obtained for Cuba (Guantanamo Bay), Florida (Everglades), Guadeloupe (Le Raizet) 13

and Puerto Rico (Ponce and Utuado). These steps are also evident in their individual 14

series (Table 3), and are negative except for Guadeloupe – the southernmost of these 15

stations. The 1970/71 change points are positive and are evident for Cuba 16

(Guantanamo Bay), Dominican Republic, Jamaica (Worthy Park) and Puerto Rico 17

(San Juan) (though not identified in their individual series). The 1978/79 change 18

points are obtained for Barbados (Husbands), Guadeloupe, Florida (Everglades) and 19

Honduras (La Mesa). The change points are positive except for Honduras. The 1983 20

change points are negative and are obtained for Puerto Rico (Ponce and Utuado) and 21

Guatemala. Therefore these change point years (1968/69, 1970/71, 1978/79 and 1983) 22

are investigated further. 23

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4. Analysis of shifts 1

4.1 Data Issues 2

For 1968/69 and 1970/71, the plots for Cuba (Guantanamo Bay), Dominican 3

Republic, Guadeloupe and Puerto Rico (San Juan) (not shown) showed divergence in 4

the maximum and minimum temperature anomalies. This was also the case for 5

Barbados (Husbands) with respect to 1979. The plots for Puerto Rico (Ponce) (c.f. 6

Figure 2c and 3c) reveal a noticeable increase in maximum and minimum temperature 7

anomalies between 1958 and 1968 in comparison to the rest of the timeseries. These 8

inconsistencies in maximum and minimum temperature series are identifiable around 9

the years of the identified step change, but are largely absent from the rest of the 10

temperature timeseries. They are therefore more likely due to station inhomogeneities 11

than regional climate shifts. Consequently, in identifying homogenous periods for the 12

data in Section 5, the change point years identified above for Barbados (Husbands), 13

Cuba (Guantanamo Bay), Dominican Republic, Guadeloupe and Puerto Rico (San 14

Juan) are excluded. Figure 4 shows the location of these stations. There appears to be 15

no distinct regional pattern linking the stations. More detailed investigations would 16

necessitate the use of metadata. 17

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4.2 Climate shifts 19

The plots for Florida, Guadeloupe, Honduras (La Mesa) and Puerto Rico 20

(Utuado) do not reveal the divergent behaviour noted in the previous section around 21

the 1968 and 1978/79 change points This is the case as well for Guatemala and Puerto 22

Rico (San Juan and Ponce) for 1983. Therefore the 1968, 1978/79 and the 1983 23

change points are further investigated using composite analysis. As noted in the 24

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previous section, there does not appear to be a distinct spatial relationship across 1

stations. 2

Synoptic analyses are undertaken to determine whether the apparent climate 3

shifts are evident in large-scale circulation patterns. Composites of annual 1000 hPa 4

air temperature, 500 hPa pressure vertical velocity, and divergent wind and vorticity 5

at sigma levels of 0.995 (surface) and 0.2101 (upper troposphere) are constructed for 6

five years before and after the identified step changes. The difference maps are 7

produced with areas significant at the 95% and 99% levels highlighted (see Section 8

2). We note that the significance testing done here is to primarily highlight the 9

difference between periods before and after the identified change points. More 10

rigorous field significance testing, for e.g. see Ventura et al. (2004) could be done and 11

is the subject of future work. 12

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4.2.1 1968 14

Composites constructed around 1968, i.e. 1969-73 minus 1963-67, are shown 15

in Figure 5. Significant positive changes in surface air temperatures are evident over 16

the Caribbean - south of 18oN, and over Florida and Belize (Figure 5a). This indicates 17

relatively warmer surface air temperatures post-1968 and is not consistent with the 18

change point shift towards lower temperatures identified for 1968 for Florida and 19

Puerto Rico (Table 4). However, Figure 5a reveals a gradient in temperatures 20

between the North Atlantic and South Atlantic, the former (latter) associated with 21

relatively cooler (warmer) temperatures post-1968. This gradient agrees with the 22

meridional gradient mode presented by Wang (2002b) which is in its negative phase 23

during 1971-75, characterised by negative (positive) SST anomalies over the tropical 24

north (south) Atlantic. Other studies [such as Oort et al. (1987), Kushnir (1994) and 25

19

Grosfeld et al. (2007)] also suggest a relatively cooler north Atlantic during the 1970s, 1

with Levitus (1989 a,b) documenting a cooling of the first 1000m of the North 2

Atlantic ocean post-1970. 3

The relatively cooler surface temperatures of the North Atlantic post-1968, do 4

not appear to penetrate the Caribbean in the composite map shown in Figure 4a as it 5

does for the NCEP SST composite difference maps (1965-70 vs. 1971-75) shown by 6

Wang (2002b) (see author’s Figure 7). This may be as a result of the different periods 7

used for constructing the composite difference maps. Wang’s composite difference 8

maps in SST anomalies do however show: (1) oppositely signed SST anomalies 9

around Florida and northern Central America (i.e. with respect to the North Atlantic), 10

consistent with Figure 5a and (2) strong SST differences over the eastern and southern 11

Caribbean which support the significant change points evident in SSTs for 1970/71 12

over the eastern Caribbean and Panama, i.e. versus the rest of the Caribbean and 13

adjacent regions where the 1970/71 change point was not significant (c.f. Table 3). 14

Significantly stronger mid-tropospheric ascent (or lower magnitude descent) 15

post-1968 (c.f. Figure 5b) is evident over northern South America into the 16

southernmost Caribbean; over Florida and Central America. Over northern South 17

America the mid-level ascent is coupled with low level convergence (c.f. Figure 5c) 18

and upper level divergence (c.f. Figure 5d) – all of which supports the picture of 19

warmer temperatures post-1968. This is not however consistent with the anomalously 20

dry climate observed over the Central American-Caribbean region during the early 21

1970s (Hastenrath 1976, Peterson et al. 2002) which implies increased subsidence, 22

drier mid levels and increased atmospheric cooling post-1970 (Knaff 1997). 23

Other potentially relevant changes in the climate system have also been noted 24

since 1970. These include: (1) increasing positive values of the winter atmospheric 25

20

North Atlantic Oscillation (NAO) which is associated with higher than normal North 1

Atlantic high, hence stronger trade winds and cooler SSTs (Giannini et al. 2001, 2

Hurrell 1995, Higuchi et al. 1999); (2) onset of the negative phase of the oceanic 3

Atlantic multidecadal oscillation – associated with cooler than normal North Atlantic 4

SSTs (Enfield et al., 2001). A plot of annual NAO4 anomalies versus an 11-station 5

annual average temperature index (also anomalies) is shown in Figure 6. Evident is 6

the post - 1970 shift towards positive NAO, and a change towards less synchronized 7

variations of the average temperatures over the Caribbean and adjacent Caribbean 8

with the NAO. Correlation between the indices pre -1970, i.e. 1961 - 1970 (0.43) is 9

greater than post -1970, i.e. 1971 - 1990 (0.38), the latter value being statistically 10

significant. 11

The idea is that though the NCEP reanalysis does not support the negative 12

breakpoint identified in 1968, given the other evidence/studies that exist to point to its 13

climate-relatedness, this feature is not considered as an inhomogeneity. Furthermore it 14

may be useful to note that for the late 1960’s certain NCEP Reanalysis variables 15

including 2m air temperature over southern Europe into the North Atlantic have 16

shown some discontinuity (Pohlmann and Greatbatch 2006). Additionally with the 17

introduction of satellite measurements in the late 1970’s, systematic errors have been 18

evident in the tropical atmosphere observations in some reanalyses products, 19

including. NCEP and the European Centre for Medium-Range Weather Forecast 40-20

years (ERA-40) (Santer et al. 1999, Trenberth et al 2001, Sturaro 2003, Sterl 2004, 21

Kinter et al. 2004, Trenberth and Smith 2005, Greatbach and Rong 2006). This has 22

had implications for climate trend analyses in that apparent and significant shifts were 23

possibly linked to changes in the observing system and/or the data assimilation 24

4 NAO values can be downloaded from http://www.cru.uea.ac.uk/cru/data/nao.htm

21

procedures (Kinter et al. 2004). For the purpose of this study the shift towards warmer 1

post - 1970 temperatures that is evident in the NCEP Reanalysis, but absent in other 2

datasets, may be related to this issue of discontinuity. 3

4

4.2.2 1983 5

Analysis of the 1983 change point reveals relatively lower temperatures post-6

1983 but differences are weak and not significant over the Caribbean (Figure 7a). A 7

gradient in surface temperatures is again visible, but with lower (higher) temperatures 8

over the tropical North (South) Atlantic for post-1983. Stronger and significant 9

medium level descent is evident over southeastern Caribbean for post-1983 (Figure 10

7b) and is coupled with low-level divergence (Figure 7c) and upper-level convergence 11

(Figure 7d) just north of South America into the southern Caribbean. This is 12

consistent with the gradient mode pattern presented by Wang (2002b), and with the 13

anomalously dry Caribbean observed in the late 1980s (Peterson et al. 2002). The 14

1980s have also been associated with an intensified North Atlantic high (i.e. high 15

NAO index) (Drinkwater 1996, Curry et al. 1998). Therefore the negative step in 16

Puerto Rico and Guatemala temperatures for 1983 may be associated with this large-17

scale shift in circulation. It is important to note that this negative shift in temperatures 18

for 1983 is also evident in the individual temperature series for Barbados, Costa Rica, 19

Dominican Republic, Honduras and Panama (Table 3), suggesting a Caribbean – 20

Central American wide influence. 21

22

4.2.3 1979 23

Composite difference maps for 1979 indicate significantly higher air 24

temperatures post-1979 for the central to southern Caribbean but not for Florida 25

22

where a hint of slightly lower temperatures is visible (Figure 8a). Interestingly, the 1

gradient in surface temperatures between the North and South Atlantic is not evident 2

in this case. Significantly stronger low-level convergence and upper-level divergence 3

over the Caribbean post-1979 are indicated (Figures 8c-d) but are not associated with 4

significant changes in medium-level air motion over the main Caribbean (Figure 8b). 5

The implication is that the significant changes evident in the atmospheric circulation 6

do not appear to penetrate the entire troposphere. Therefore, the significant positive 7

step changes evident identified for Barbados and Trinidad for 1978/9 can be 8

associated with changes in the large-scale circulation. As noted in Section 4.2.1, the 9

1978/79 change point coincides with the introduction of satellite measurements. 10

Therefore it is plausible that the 1978/79 change point may be linked to an NCEP 11

discontinuity. 12

13

5. Reanalysis of some Caribbean and adjacent Caribbean Trends 14

The analyses described in the previous sections allow for the identification of 15

a primary common homogeneous period across the data. This period spans 1970-1992 16

for Grantley Adams (Barbados), Catie (Costa Rica), Casa Blanca (Cuba), Everglades 17

(Florida), Key West (Florida), Le Raizet (Guadeloupe), Flores (Guatemala), Santa 18

Rosa de Copan (Honduras), Ponce (Puerto Rico) and Freeport (Bahamas); with 19

maximum temperatures for Nassau Airport (Bahamas) and minimum temperatures for 20

Worthy Park (Jamaica). A secondary homogeneous period can be deduced for 1984-21

1998 for PSWGIA (Belize), Guantanamo Bay (Cuba), La Ceiba (Honduras), Tela 22

(Honduras), San Juan (Puerto Rico), Piarco (Trinidad) with maximum temperatures 23

for Grand Cayman (Cayman Islands) Santo Domingo (Dominican Republic) and 24

Worthy Park (Jamaica). Figure 9 shows the location of these stations. 25

23

1

A pertinent question to be posed is: Would the results of PTD change using the 2

homogeneous data for this period? To address this question, indices of temperature 3

extremes were reconstructed for each of stations. The indices examined include 4

percent of days maximum and minimum temperature were greater than or equal to the 5

90th

percentile, and the number of days maximum and minimum temperature were 6

less than or equal to the 10th

percentile. Following the PTD approach, the numerical 7

average of the index results from each station was calculated. Figure 10 shows the 8

averaged time series and their associated regression lines to indicate the presence of 9

any trend. The statistical significance of the trend is also tested. Although a 23-year 10

dataset can be considered too short for trend analyses, it can justifiably be used in a 11

comparative sense to investigate changes in extremes identified from the PTD work. 12

The results indicate that the percent of days at or above the 90th

percentile has 13

increased over the base period (1970-1992) while the percent of days at or below the 14

10th

percentile has decreased. All the regression slopes are significant at the 1% level. 15

The trends obtained are consistent with those presented by PTD. Interestingly the 16

annual variations in the indices also resemble the variability obtained by PTD, for e.g. 17

the peaks between 1985 and 1990 for the percent of days when maximum and 18

minimum temperatures are at or above the 90th

percentile. For other indices the trends 19

are very similar to PTD and are therefore not discussed. 20

21

6. Summary and Conclusions 22

This study provides a systematic evaluation of the homogeneity of daily 23

temperature data on a monthly timescale for the Caribbean, Florida, and countries in 24

Central America and northern South America with a Caribbean coastline. The method 25

24

uses adjacent SSTs as reference series, and presents an alternative approach for 1

islands/coastal regions that possess a low density of temperature stations, but where 2

well correlated SST data are available. In this study a strong association was observed 3

between SSTs and station maximum and minimum temperatures, primarily for the 4

Caribbean islands and Florida, and secondly for the minimum temperatures of Central 5

America (see Section 3). This provided a strong basis for the use of SSTs in 6

developing reference series for the homogeneity assessments and purports the 7

possible use of SSTs as a proxy for Caribbean and adjacent Caribbean surface 8

temperatures. 9

A reasonable question to be considered is whether the use of SSTs as a 10

reference series is comparable to the use of neighbouring stations towards the 11

development of reference series. Correlation analysis is used to investigate this 12

question. Station-based reference series were constructed using an average of those 13

stations that were deduced as homogeneous for the 1970-1992 period (see Section 5). 14

The correlation coefficients were calculated between the station average reference 15

series and the maximum and minimum temperature series for each island/country. 16

Where the station of interest was also one of the homogeneous series, it was omitted 17

from the average before calculating the correlation coefficient. The difference 18

between the correlations obtained with respect to SSTs (c.f. Table 1) and the station 19

average reference series were calculated and the significance assessed at the 99% 20

level using a t-test (Chen and Popovich 2002). 21

The results (not shown) indicate that 17 (12) of the 34 stations listed in Table 1 22

exhibited correlations that were not significantly different from correlations obtained 23

with respect to the station average reference series. In these cases the correlations 24

were minimally higher with respect to the station average series. For those cases 25

25

where the difference was statistical significant, again most of the correlations were 1

greater with respect to the station average series when compared to SSTs. These 2

results indicate that the use of SSTs towards developing reference series is at least a 3

viable option in assessing the homogeneity of station series for areas of low station 4

density and which have strong associations with SST variability. 5

The change points identified using the SST-based reference series were also 6

investigated using composite analysis, and two overlapping homogeneous periods 7

were identified across the data. They include: (1) 1970-1992: for Grantley Adams 8

(Barbados), Catie (Costa Rica), Casa Blanca (Cuba), Everglades (Florida), Key West 9

(Florida), Le Raizet (Guadeloupe), Flores (Guatemala), Santa Rosa de Copan 10

(Honduras), Ponce (Puerto Rico) and Freeport (Bahamas); with maximum 11

temperatures for Nassau Airport (Bahamas) and minimum temperatures for Worthy 12

Park (Jamaica); (2) 1984-1998: PSWGIA (Belize), Guantanamo Bay (Cuba), La 13

Ceiba (Honduras), Tela (Honduras), San Juan (Puerto Rico), Piarco (Trinidad) with 14

maximum temperatures for Grand Cayman (Cayman Islands) Santo Domingo 15

(Dominican Republic) and Worthy Park (Jamaica). It is important to note however 16

that the absence of proof of an inhomogeneity is not necessarily proof of absence. The 17

results suggest there is evidence of homogeneity but more data work is needed. 18

The 1970-92 period can be considered the more useful period for additional 19

trend analyses and statistical downscaling studies given the length of available 20

observations. This period was used to investigate whether the results of the PTD trend 21

analysis of temperature extremes would vary using the homogeneous data. The results 22

were found to be consistent for the indices characterizing percent of days maximum 23

and minimum temperature were greater than or equal to the 90th

percentile, and the 24

26

number of days maximum and minimum temperature were less than or equal to the 1

10th

percentile and offers credence to the PTD results. 2

An implicit aim of this study then was to extend the work done by PTD by 3

building upon the daily data archive available for the Caribbean. Even with the 4

possibility of SST use as proxy for surface temperatures for the Caribbean and 5

adjacent Caribbean, there is no substitute for the valuable data recovery that has been 6

done and which needs to continue to advance the trend analysis work for the region. 7

Further efforts must include (i) acquiring additional quality controlled data, and 8

metadata, and (ii) expanding the current database via the application of 9

homogenization techniques. Data adjustment is beyond the scope of the current work 10

since the approaches that could be employed depend on station density, ability to 11

create a reference series, and the availability of metadata (Vincent et al. 2002) - the 12

same critical issues that were encountered in this study. The result would be a data 13

archive for the Caribbean and adjacent Caribbean that could be used with greater 14

confidence for the analyses of trends, climate variability and climate change. 15

Reservations in sharing metadata still exist, that is, in cases where metadata are 16

present and is a challenge that must necessarily be overcome. The homogeneous data 17

isolated in this study is currently being used in statistical downscaling investigations 18

for the Caribbean and adjacent Caribbean. 19

20

21

22

23

24

25

27

Acknowledgement 1

This work was conducted by the lead author during a study visit to the Climatic 2

Research Unit funded by the Caribbean Community Climate Change Centre, Belize 3

and the Department of Physics at the University of the West Indies, Mona, Jamaica. 4

The authors thank Peterson et al. (2002) and Aguilar et al. (2005) for providing the 5

datasets used in the study. The datasets are compiled from meteorological services in 6

nine Caribbean islands, seven Central American countries, Florida and Venezuela. 7

Thanks also to the National Climatic Data Center, Caribbean Institute for 8

Meteorology and Hydrology and the Caribbean meteorological services, particularly 9

St. Vincent and St. Lucia, for data and additional assistance given. Thanks to the 10

reviewers for providing very useful comments. 11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

28

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17

18

19

20

21

22

23

24

25

40

Figure Captions 1

2

Figure 1. Location of the stations used in the study. Stations obtained from Peterson 3

et al. (2002) and Aguilar et al. (2005) are depicted by circles (14 stations) and 4

triangles (21 stations) respectively. Stations obtained from the National Climatic Data 5

Center, Caribbean Institute for Meteorology and Hydrology and Caribbean 6

meteorological services are represented by crosses (6 stations). Some stations are 7

close enough for the overlap of their symbols. 8

9

Figure 2. Plots of SST, maximum and minimum temperature anomalies (oC) for: (a) 10

Bahamas (Freeport), (b) Honduras (Tela) and (c) Puerto Rico (Ponce). SSTs, 11

maximum temperature and minimum temperature are represented by black, red and 12

blue lines respectively. 13

14

Figure 3. Plots of monthly difference anomalies (oC) for: (a) Bahamas, (b) Honduras 15

(Tela) and (c) Puerto Rico (Ponce). Differences with respect to maximum and 16

minimum temperatures are represented by red and blue lines respectively. 17

18

Figure 4. Station distribution in relation to homogeneity results. Stations where no 19

significant change points were identified are depicted by circles (4 stations). Stations 20

where change points identified may be related to data issues are represented by 21

crosses (4 stations) and where change points may be related to climate shifts are 22

represented by squares (7 stations). 23

24

41

Figure 5. Composite difference for 1968 of (a) 1000 hPa air temperature (oC), (b) 500 1

hPa vertical velocity (Pa/s), (c) divergent wind (m/s) and vorticity (m2/s) at sigma 2

level 0.995 and (d) divergent wind and vorticity at sigma level 0.2101. Broken 3

contours are negative. Differences in contoured values significant at the 1% (5%) 4

level are indicated by dark (light) shading. 5

6

Figure 6. Plot of annual North Atlantic Oscillation (NAO) anomalies (dashed line and 7

circles) versus annual average temperature anomalies over the Caribbean and adjacent 8

Caribbean (solid line and crosses). 9

10

Figure 7. Same as Figure 5 but for 1983. 11

12

Figure 8. Same as Figure 5 but for 1979. 13

14

Figure 9. Location of station for which common homogeneous periods are identified. 15

Stations with maximum and/or minimum temperatures for 1970-92 are represented by 16

squares (12 stations). Stations with maximum and/or minimum temperatures for 1984-17

98 are represented by crosses (9 stations). 18

19

Figure 10. The percent of days when the maximum (solid line) and minimum 20

(dashed line) temperatures are (a) at or above the 90th

percentile) and (b) at or below 21

the 10th

percentile. Percentiles determined by homogeneous data from 1970 though 22

1992. 23

24

25

42

Tables 1

Table 1. Temperature stations used in the study. Data are sourced from Peterson et al. 2

(2002) (PTD), Aguilar et al (2005) (APO), the National Climatic Data Center (NCDC), 3

the Caribbean Institute for Meteorology and Hydrology (CIMH) and the local 4

meteorological services. 5

6

Country Station Name Latitude Longitude Elevation

(m)

Data span Source

Bahamas FREEPORT 26.55 -78.70 11 1968-1999 PTD

Bahamas NASSAU

AIRPORT

25.05 -77.47 7 1973-2004 NCDC

Barbados GRANTLEY

ADAMS

13.07 -59.48 56 1973-2006 NCDC

Ba8rbados HUSBANDS 13.17 -59.59 -999 1969-1999 PTD

Belize PSWGIA 17.53 -88.30 5 1961-2003 APO

Belize CENTRAL FARM 17.31 -88.12 61 1966-1999 PTD

Cayman

Islands

GRAND

CAYMAN

19.17 -81.21 3 1976-1999 PTD

Costa Rica CATIE 9.90 -83.75 0 1961-2003 APO

Costa Rica FABIO BAUDRIT 10.00 -84.25 0 1961-2003 APO

Cuba CASA BLANCA 23.17 -82.35 50 1961-2003 APO

Cuba GUANTANAMO

BAY

19.90 -75.15 16 1958-1998 PTD

Dominican

Republic

SANTO

DOMINGO

18.48 -69.92 14 1958-1999 PTD

U.S.-Florida EVERGLADES 25.83 -81.38 2 1958-1999 PTD

7

43

Table 1. (continued) 1

2

Country Station Name Latitude Longitude Elevation

(m)

Data span Source

U.S.-Florida KEY WEST WSO

AIRPORT

24.55 -81.75 1 1958-1999 PTD

Guadeloupe LE RAIZET 16.27 -61.60 11 1951-2000 NCDC

Guatemala FLORES 16.51 -89.87 123 1961-2003 APO

Jamaica SANGSTER 18.50 -77.92 8 1973-2006 NCDC

Jamaica WORTHY PARK 18.15 -77.17 550 1961-1999 Met

Service

Honduras CATACAMAS 14.90 -85.93 442 1961-2003 APO

Honduras LA CEIBA 15.73 -86.87 26 1961-2003 APO

Honduras LA MESA 15.45 -87.93 31 1961-2003 APO

Honduras SANTA ROSA DE

COPAN

14.78 -88.78 1079 1961-2003 APO

Honduras TEGUCIGALPA 13.50 -87.22 1007 1961-2003 APO

Honduras TELA 15.72 -87.48 3 1961-2003 APO

Nicaragua RIVAS 11.42 -85.83 70 1961-2003 APO

Panama ANTON 8.35 -80.27 33 1961-2003 APO

Panama DAVID 8.40 -82.42 27 1961-2003 APO

U.S.-Puerto

Rico

LARES 18.27 -66.85 445 1958-1998 PTD

U.S.-Puerto

Rico

PONCE 18.02 -66.52 21 1958-1999 PTD

U.S.-Puerto

Rico

SAN JUAN WSFO 18.43 -66.00 3 1958-1999 PTD

44

Table 1. (continued) 1

2

Country Station Name Latitude Longitude Elevation

(m)

Data span Source

U.S.-Puerto

Rico

UTUADO 18.25 -66.68 159 1958-1998 PTD

St. Lucia GFL CHARLES

AIRPORT

14.02 -61.00 1982-2006 Met

Service

St. Vincent ST. VINCENT 13.13 -61.20 13 1987-2006 PTD,

CIMH,

Met

Service

Trinidad PIARCO IAP 10.37 -61.21 15 1959-1999 PTD

Venezuela GUIRIA 10.58 -62.32 14 1961-2003 APO

Venezuela LA CARLOTA 10.50 -66.88 835 1961-2003 APO

Venezuela MAIQUETIA Apt.

BOLIVAR

10.60 -66.98 48 1961-2003 APO

Venezuela MARACAY 10.25 -67.65 437 1961-2003 APO

Venezuela MENE GRANDE 9.82 -70.93 28 1961-2002 APO

Venezuela MERIDA 8.60 -71.18 1498 1961-2003 APO

Venezuela TUMEREMO 7.30 61.45 181 1961-2003 APO

3

4

5

6

7

8

45

Table 2. Correlations between sea surface temperatures and maximum and minimum 1

temperatures respectively for 1970-1998. Values in bold are significant at the 95% 2

level. 3

4

Country Station Maximum

Temperature

Minimum

Temperature

Bahamas Freeport 0.93 0.91

Bahamas Nassau Airport 0.93 0.91

Barbados Grantley Adams 0.74 0.66

Barbados Husbands 0.58 0.72

Belize PSWGIA 0.64 0.65

Belize Central Farm 0.45 0.80

Cayman Islands Grand Cayman 0.89 0.79

Costa Rica Catie 0.63 0.59

Costa Rica Fabio Baudrit 0.09 0.57

Cuba Casa Blanca 0.89 0.94

Cuba Guantanamo

Bay

0.66 0.83

Dominican Republic Santo Domingo 0.82 0.81

Florida Everglades 0.91 0.92

Florida Key West 0.92 0.91

Guadeloupe Le Raizet 0.83 0.78

Guatemala Flores 0.47 0.86

Honduras Catacamas 0.29 0.66

5

46

Table 2. (continued) 1

2

Country Station Maximum

Temperature

Minimum

Temperature

Honduras La Ceiba 0.58 0.76

Honduras La Mesa 0.44 0.77

Honduras Santa Rosa De

Copan

0.49 0.88

Honduras Tegucigalpa 0.50 0.82

Honduras Tela 0.66 0.83

Jamaica Sangster 0.77 0.85

Jamaica Worthy Park 0.67 0.74

Nicaragua Rivas 0.55 0.58

Panama Anton 0 0.38

Panama David 0.57 0.68

Puerto Rico Ponce 0.78 0.81

Puerto Rico San Juan 0.76 0.84

Puerto Rico Utuado 0.72 0.86

St. Lucia GFL Charles

Airport

0.74 0.76

St. Vincent St. Vincent 0.71 0.85

Trinidad Piarco IAP 0.41 0.66

Venezuela Guiria 0.29 0.44

Venezuela La Carlota 0.08 0.43

3

47

Table 2. (continued) 1

2

Country Station Maximum

Temperature

Minimum

Temperature

Venezuela Maiquetia Apt.

Bolivar

0.73 0.69

Venezuela Maracay -0.39 0.34

Venezuela Mene Grande -0.10 0.05

Venezuela Merida 0.29 0.53

Venezuela Tumeremo 0.51 0.49

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

48

Table 3. Change points obtained from homogeneity assessments of adjacent monthly 1

sea surface temperatures and maximum and minimum temperatures at each station. 2

Values in bold are significant at the 99% level. 3

4

Sea Surface

Temperatures

Maximum

Temperature

Minimum

Temperature

Country Station

Year Size

(oC)

Year Size

(oC)

Year Size

(oC)

Bahamas Freeport - - - - - -

Bahamas Nassau Airport - - 1995 -0.96 1987 1.08

Barbados Grantley Adams 1970

1983

-0.77

-0.44

1984

1996

-0.63

-0.54

1983 -0.92

Barbados Husbands 1970

1983

-0.77

-0.44

- - - -

Belize PSWGIA 1971

1983

-0.21

-0.83

- - 1974 -0.69

Belize Central Farm 1971

1983

-0.21

-0.83

1985 -1.90 - -

Cayman Islands Grand Cayman - - - - - -

Costa Rica Catie 1973

1984

-0.43

-0.20

1982

1993

-0.22

1.48

1983 -0.52

Costa Rica Fabio Baudrit 1973

1984

-0.56

-0.34

1981 0.54 1979

1992

1.62

1.18

Cuba Casa Blanca - - - - - -

5

49

Table 3. (continued) 1

2

Sea Surface

Temperatures

Maximum

Temperature

Minimum

Temperature

Country Station

Year Size

(oC)

Year Size

(oC)

Year Size

(oC)

Cuba Guantanamo

Bay

1970 -0.40 1968

1980

-1.07

2.22

1985 1.06

Dominican

Republic

Santo Domingo 1970

1983

-0.69

-0.31

1981 -0.73 1972

1983

0.22

-0.53

United States

(Florida)

Everglades - - 1968 -1.29 - -

United States

(Florida)

Key West - - - - - -

Guadeloupe Le Raizet 1970

1983

-0.74

-0.51

1967

1977

1990

0.72

0.74

0.69

1979 0.78

Guatemala Flores 1983 -0.52 - - - -

Honduras Catacamas 1971

1983

-0.42

-0.46

1976 0.94 1984 -1.23

Honduras La Ceiba 1971

1983

-0.26

-0.75

1990 1.3 1977 1.51

Honduras La Mesa 1971

1983

-0.24

-0.69

1975 -0.62 1973

1983

-0.22

-0.85

3

50

Table 3. (continued) 1

2

Sea Surface

Temperatures

Maximum

Temperature

Minimum

Temperature

Country Station

Year Size

(oC)

Year Size

(oC)

Year Size

(oC)

Honduras Santa Rosa De

Copan

1973 0.27 1973 -1.04 1984 -0.61

Honduras Tegucigalpa 1973

1990

0.46

0.58

1983 -0.88 1976 1.56

Honduras Tela 1971

1983

-0.24

-0.69

1975 -0.62 1973

1983

-0.22

-0.85

Jamaica Sangster 1970

1983

-0.49

-0.42

1992 0.67 1989 0.86

Jamaica Worthy Park 1970

1983

-0.49

-0.42

1986 0.68 1976

1987

1.06

1.21

Nicaragua Rivas 1973

1990

0.51

0.84

1987 0.68 1987 0.40

Panama Anton 1971

1984

-0.4

-0.31

1983 -0.75 1993 -0.56

Panama David 1971

1984

-0.33

-0.22

- - 1983 -0.54

Puerto Rico Ponce 1970

1983

-0.80

-0.36

1969

1983

-1.58

-0.83

1969

1983

-1.95

-0.88

3

51

Table 3. (continued) 1

2

Sea Surface

Temperatures

Maximum

Temperature

Minimum

Temperature

Country Station

Year Size

(oC)

Year Size

(oC)

Year Size

(oC)

Puerto Rico San Juan 1970

1983

-0.80

-0.36

1977 1.04 1973

1983

-0.42

-2.05

Puerto Rico Utuado 1970

1983

-0.80

-0.36

1972 0.85 1970

1983

-1.20

-0.50

St. Lucia GFL Charles

Airport

1970

1983

-0.78

-0.50

- - 1995 0.79

St. Vincent St. Vincent 1970

1983

-0.77

-0.47

- - - -

Trinidad Piarco IAP 1970

1981

-0.66

-0.35

1976

1987

0.71

0.89

1979 0.56

Venezuela Guiria 1971

1983

-0.61

-0.40

1976

1987

1.37

1.09

1971

1981

-0.89

-1.35

Venezuela La Carlota 1971

1983

-0.62

-0.59

1976

1986

1.06

1.36

1979 1.29

Venezuela Maiquetia Apt.

Bolivar

1971

1983

-0.62

-0.59

1976

1986

1.06

1.36

1979 1.29

Venezuela Maracay 1971

1983

-0.65

-0.52

1985 0.68 1980

1990

0.92

-0.52

3

52

Table 3. (continued) 1

2

Sea Surface

Temperatures

Maximum

Temperature

Minimum

Temperature

Country Station

Year Size

(oC)

Year Size

(oC)

Year Size

(oC)

Venezuela Mene Grande 1971

1983

-0.51

-0.36

1973

1988

-0.33

-0.91

1976

1989

0.34

1.46

Venezuela Merida 1971

1983

-0.51

-0.36

1980 0.94 1976

1989

0.50

0.82

Venezuela Tumeremo 1971 -0.51 1971

1990

-1.54

-1.66

1972

1985

-0.4

0.81

3

4

5

6

7

8

9

10

11

12

13

14

15

53

Table 4. Same as Table 3 but for monthly difference anomalies for maximum 1

temperature and SST, and minimum temperature and SST respectively. Possible only 2

for stations with correlation of greater than 0.70 with respect to SSTs. Italicized 3

values indicate stations with correlations of 0.65-0.69 for one of the temperature 4

series and greater than or equal to 0.70 for the other series. 5

6

Country Station Maximum

Temperature

Difference

Anomalies

Minimum

Temperature

Difference

Anomalies

Year Size (oC) Year Size (

oC)

Bahamas Freeport 1982 -0.41 1982 0.59

Bahamas Nassau Airport 1994 -0.95 1987 0.92

Barbados Grantley Adams 1984

1994

-0.1

-0.46

1983

1994

-0.55

-0.14

Barbados Husbands 1979 0.53

Belize Central Farm 1987 0.88

Cayman Grand Cayman - - 1986 0.55

Cuba Casa Blanca 1971

1981

0.37

0.43

1971

1993

0.29

-0.36

Cuba Guantanamo Bay 1968

1981

-0.82

2.21

1970

1982

0.53

1.23

Dominican

Republic

Santo Domingo 1971

1981

0.49

-0.64

1971

1989

0.51

-0.50

Florida Everglades 1968 -1.17 1979 0.62

54

Table 4. (continued) 1

2

Country Station Maximum

Temperature

Difference

Anomalies

Minimum

Temperature

Difference

Anomalies

Year Size Year Size

Florida Key West 1968

1984

-0.18

0.37

1968

1982

-0.08

-0.57

Guadeloupe Le Raizet 1969

1979

0.69

0.52

1967

1979

1989

-0.23

0.61

0.09

Guatemala Flores 1983 0.65

Honduras La Ceiba 1977

1989

0.96

0.03

Honduras La Mesa 1979

1991

-0.51

-1.24

Honduras Santa Rosa De

Copan

1973

1984

-0.35

-0.46

Honduras Tegucigalpa 1975

1985

1.25

-0.86

Honduras Tela 1975

1990

-1.07

-0.36

1977 -0.21

Jamaica Sangster 1991 0.39 1988 0.84

3

55

Table 4. (continued) 1

2

Country Station Maximum

Temperature

Difference

Anomalies

Minimum

Temperature

Difference

Anomalies

Year Size Year Size

Jamaica Worthy Park 1971

1982

0.15

0.78

1981 -0.59

Puerto Rico Ponce 1969

1986

-1.00

-0.59

1969

1983

-1.24

-0.51

Puerto Rico San Juan 1971

1981

1.56

0.63

1970

1983

1.32

-1.27

Puerto Rico Utuado 1973

1986

0.73

-0.27

1968 -0.70

St. Lucia GFL Charles

Airport

1992 -0.22 1993 0.47

St. Vincent St. Vincent - - - -

Venezuela Maiquetia Apt.

Bolivar

1975

1985

0.79

1.25

1978 1.21

3

4

5

6

7

56

Figures 1

Figure 1. Location of the stations used in the study. Stations obtained from Peterson et 2

al. (2002) and Aguilar et al. (2005) are depicted by circles (14 stations) and triangles 3

(21 stations) respectively. Stations obtained from the National Climatic Data Center, 4

Caribbean Institute for Meteorology and Hydrology and Caribbean meteorological 5

services are represented by crosses (6 stations). Some stations are close enough for the 6

overlap of their symbols. 7

8

9

10

11

12

13

14

15

16

17

18

57

Figure 2. Plots of SST, maximum and minimum temperature anomalies (oC) for: (a) 1

Bahamas (Freeport), (b) Honduras (Tela) and (c) Puerto Rico (Ponce). SSTs, 2

maximum temperature and minimum temperature are represented by black, red and 3

blue lines respectively. Units are oC. 4

(a) 5

6 (b) 7

8 (c) 9

10

58

Figure 3. Plots of monthly difference anomalies (oC) for: (a) Bahamas, (b) Honduras 1

(Tela) and (c) Puerto Rico (Ponce). Differences with respect to maximum and 2

minimum temperatures are represented by red and blue lines respectively. Units are 3

oC. 4

(a) 5

6

(b) 7

8

(c) 9

10

59

Figure 4. Station distribution in relation to homogeneity results. Stations where no 1

significant change points were identified are depicted by circles (4 stations). Stations 2

where change points identified may be related to data issues are represented by 3

crosses (4 stations) and where change points may be related to climate shifts are 4

represented by squares (7 stations). 5

6

7

8

9

10

11

12

13

14

15

16

17

18

60

Figure 5. Composite difference for 1968 of (a) 1000 hPa air temperature (oC), (b) 500 1

hPa vertical velocity (Pa/s), (c) divergent wind (m/s) and vorticity (m2/s) at sigma 2

level 0.995 and (d) divergent wind and vorticity at sigma level 0.2101. Broken 3

contours are negative. Differences in contoured values significant at the 1% (5%) 4

level are indicated by dark (light) shading. 5

6

(a) (b) 7

8

9

(c) (d) 10

11

12

61

Figure 6. Plot of annual North Atlantic Oscillation (NAO) anomalies (dashed line and 1

circles) versus annual average temperature anomalies over the Caribbean and adjacent 2

Caribbean (solid line and crosses). 3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

62

Figure 7. Same as Figure 5 but for 1983. 1

2

(a) (b) 3

4

5

(c) (d) 6

7

8

9

10

11

12

13

63

Figure 8. Same as Figure 5 but for 1979. 1

2

(a) (b) 3

4

5

(c) (d) 6

7

8

9

10

11

64

Figure 9. Location of station for which common homogeneous periods are identified. 1

Stations with maximum and/or minimum temperatures for 1970-92 are represented by 2

squares (12 stations). Stations with maximum and/or minimum temperatures for 1984-3

98 are represented by crosses (9 stations). 4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

65

Figure 10. The percent of days when the maximum (solid line) and minimum (dashed 1

line) temperatures are (a) at or above the 90th

percentile) and (b) at or below the 10th

2

percentile. Percentiles determined by homogeneous data from 1970 though 1992. 3

4

(a) 5

6

7

(b) 8

9