Climate Change Indices

Climate Change and Water Resources (CE74.9002) Water Engineering and Management (WEM) School of Engineering and Technology (SET),

Asian institute of Technology (AIT)

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I Putu Santikayasa

Outlines

1. Introduction 2. What is climate? 3. Climate Indices Project 4. What is Climate indices? 5. R - climdex 6. Case Study

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Introduction

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Figure 1. Schematic view of the components of the climate system, their processes and interactions. (source: IPCC)

Introduction

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Please refer to the Koppen cimate classification

What is climate?

• Weather: what is happening in the atmosphere at any given time – Air temperature at 7am = 24 deg celcius

• Climate: the “average weather” • Climate is the status of the climate system

which comprises the atmosphere, the hydrosphere, the cryosphere, the surface lithosphere and the biosphere – Average air temperature on July = 24 deg Celcius

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What is climate?

• Statistical analysis: – Mean – Maximum – Minimum – Percentile

• Climate change analysis – Change in mean, max, min, etc.

• What about the changes in extremes? – Number of days where T>90th percentile, etc

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Climate indices project

• Change on the extreme climate events impacts on nature and society

• Analyze extreme events is very important • The monitoring, detection and attribution of

changes in climate extremes require daily resolution data

• However, the compilation and update of a globally daily dataset is a very difficult task

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World Meteorological Organization Commission for Climatology (CCl)

World Climate Research Programme (WCRP) project on Climate Variability and Predictability (CLIVAR) Expert Team on Climate Change Detection, Monitoring and Indices (ETCCDMI)

International coordination of the development of a suite of climate change indices which primarily focus on extremes and analysis a suite of indices so that individuals, countries, and regions can calculate the indices in exactly the same way such that their analyses will fit seamlessly into the global picture

Output: 27 indices were defined and two software packages, one written in R (RClimDex) and the other written in FORTRAN (FClimDex), were developed

What is Climate indices?

• What is Climate Indices: A climate indices is defined as a calculated value that can be used to describe the state and the changes in the climate system.

Climate indices allow a statistical study of variations of the dependent climatological aspects, such as analysis and comparison of time series, means, extremes and trends.

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Climate Indices

• 27 indices: – 16 indices related to the temperature – 11 indices related to the precipitation

• Indices are driven from: – Maximum temperature – Minimum temperature – Precipitation

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Climate Indices

• The climate indices can be categorized into 5(five) groups:

1. Percentile-based indices 2. Absolute indices 3. Threshold indices 4. Duration indices 5. Other indices

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Percentile-based indices

1. Occurrence of cold nights (TN10p) 2. Occurrence of warm nights (TN90p) 3. Occurrence of cold days (TX10p) 4. Occurrence of warm days (TX90p) 5. Very wet days (R95p) 6. Extremely wet days (R99p).

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Absolute indices

• Represent maximum or minimum values within a season or year

1. Maximum daily maximum temperature (TXx), 2. Maximum daily minimum temperature (TNx), 3. Minimum daily maximum temperature (TXn), 4. Minimum daily minimum temperature(TNn), 5. Maximum 1-day precipitation amount (RX1day) 6. Maximum 5-day precipitation amount (RX5day)

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Threshold indices

• The number of days on which a temperature or precipitation value falls above or below a fixed threshold,

1. Annual occurrence of frost days (FD) 2. Annual occurrence of ice days (ID) 3. Annual occurrence of summer days (SU) 4. Annual occurrence of tropical nights (TR) 5. Number of heavy precipitation days > 10 mm (R10) 6. Number of very heavy precipitation days > 20 mm

(R20)

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Duration indices

• Periods of excessive warm, cold, wetness or dryness or in the case of growing season length, periods of mildness.

1. Cold spell duration indicator (CSDI) 2. Warm spell duration indicator (WSDI) 3. Growing season length (GSL) 4. Consecutive dry days (CDD) 5. Consecutive wet days (CWD)

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Others indices

• The indices do not fall into any of the above categories but could have significant societal impacts.

1. Annual precipitation total (PRCPTOT) 2. Diurnal temperature range (DTR) 3. Simple daily intensity index (SDII) 4. Extreme temperature range (ETR)* 5. Annual contribution from very wet days

(R95pT)

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*) not directly calculated by RClimDex but have been defined for this study as TXx–TNn

Climate Indices ID Indicator name Definitions UNITS

FD0 Frost days Annual count when TN(daily minimum)<0ºC Days

SU25 Summer days Annual count when TX(daily maximum)>25ºC Days

ID0 Ice days Annual count when TX(daily maximum)<0ºC Days

TR20 Tropical nights Annual count when TN(daily minimum)>20ºC Days

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Climate Indices

GSL Growing season Length

Annual (1st Jan to 31st Dec in NH, 1st July to 30th June in SH) count between first span of at least 6 days with TG>5ºC and first span after July 1 (January 1 in SH) of 6 days with TG<5ºC

Days

TXx Max Tmax Monthly maximum value of daily maximum temp ºC

TNx Max Tmin Monthly maximum value of daily minimum temp ºC

TXn Min Tmax Monthly minimum value of daily maximum temp ºC

TNn Min Tmin Monthly minimum value of daily minimum temp ºC

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Climate Indices

TN10p Cool nights Percentage of days when TN<10th percentile Days

TX10p Cool days Percentage of days when TX<10th percentile Days

TN90p Warm nights Percentage of days when TN>90th percentile Days

TX90p Warm days Percentage of days when TX>90th percentile Days

WSDI Warm spell duration indicator

Annual count of days with at least 6 consecutive days when TX>90th percentile Days

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Climate Indices

CSDI Cold spell duration indicator

Annual count of days with at least 6 consecutive days when TN<10th percentile Days

DTR Diurnal temperature range Monthly mean difference between TX and TN ºC

RX1day Max 1-day precipitation amount

Monthly maximum 1-day precipitation Mm

Rx5day Max 5-day precipitation amount

Monthly maximum consecutive 5-day precipitation Mm

SDII Simple daily intensity index

Annual total precipitation divided by the number of wet days (defined as PRCP>=1.0mm) in the year

Mm/day

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Climate Indices

R10 Number of heavy precipitation days Annual count of days when PRCP>=10mm Days

R20 Number of very heavy precipitation days

Annual count of days when PRCP>=20mm Days

Rnn Number of days above nn mm

Annual count of days when PRCP>=nn mm, nn is user defined threshold Days

CDD Consecutive dry days

Maximum number of consecutive days with RR<1mm Days

CWD Consecutive wet days

Maximum number of consecutive days with RR>=1mm Days

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Climate Indices

R95p Very wet days Annual total PRCP when RR>95th percentile Mm

R99p Extremely wet days Annual total PRCP when RR>99th percentile mm

PRCPTOT Annual total wet-day precipitation

Annual total PRCP in wet days (RR>=1mm) mm

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Software for index calculation

• RClimDex: The RClimDex provides a friendly graphical user interface to compute all 27 core indices . It also conducts simple quality control on the input daily data. It has been developed and maintained by Xuebin Zhang and Yang Feng at Climate Research Division. The software was used first at the South Africa Workshop in Cape Town, South Africa, in June 2004

• FClimDex: The FClimDex is a FORTRAN program that conducts data quality control and computes all the indices. Note that a FORTRAN 90 compiler is required to use this program.

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Software for index calculation

• ClimDex: An older MicroSoft Excel based indices software ClimDex, developed by Byron Gleason of the U.S. National Climatic Data Centre is still available. This software was used at the Caribbean Regional Climate Change workshop was held in Kingston, Jamaica in January 2001. Note that this software does not include recent improvements recommended by ET and is not supported anymore.

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Climdex and RClimdex

Climdex

• Ms. Excel platform

• Running under Window

• Difficult to fix the bug

RClimdex

• R platform • Free • Powerfull for

statistical analysis

• Running under window and unix

• Relatively easy to fix the bug

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Rclimdex ver. 1.3

• Can be used to calculate 27 core indices (as recommended by the CCl/CLIVAR )

• Developed under R 1.84 or higher • Limitation:

– Simple data quality control – Not include Data homogenization

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Rclimdex ver. 1.3

1. Not all indices are calculated on a monthly basis. 2. Monthly indices are calculated if no more than 3

days are missing in a month, while annual values are calculated if no more than 15 days are missing in a year.

3. No annual value will be calculated if any one month’s data are missing.

4. For threshold indices, a threshold is calculated if at least cover of 70% of data

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• Software and user manual can be downloaded from : http://cccma.seos.uvic.ca/ETCCDMI/software.shtml

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Rclimdex Quickguide

• The R software must be installed before run Rclimdex

• R software can be downloaded from: http://www.r-project.org

Select the R software based on the OS (Microsoft Window or UNIX)

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Rclimdex Quickguide

Data Preparation: 1. Data must be formatted as ASCII text file 2. Columns as following sequences: Year, Month,

Day, PRCP, TMAX, TMIN. (NOTE: PRCP units = millimeters and Temperature units= degrees Celsius)

3. The format as described above must be space delimited

4. Missing data must be coded as -99.9; data records must be in calendar date order. (Missing dates are allowed)

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Rclimdex Quickguide

• Sample data:

Year

Month

Day

Precipitation (mm)

TMax (oC)

TMin (oC)

Missing data

Calendar date order – missing dates are allowed

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Rclimdex Quickguide

1. Load RClimdex

2. Load Data->Run QC

3. Indices Calculation

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1. Within the R consol prompt “>”, enter source(“rclimdex.r”). This will load RClimDex into R environment

Type: source (“rclimdex path”)

– source("C:\\climateindices\\rclimdex.r") – source (“http://cccma.seos.uvic.ca/ETCCDMI/RClimDex/rclimdex.r”)

2. Choose the “File” from the RGui menu, and

then select “Source R code” (recommended)

Load RClimdex Load Data->Run QC Indices Calculation

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Rclimdex Quickguide

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• Data Quality Control is a prerequisite for indices calculations

• The RClimDex QC performs the following procedure: – Replace all missing values (currently coded as -99.9) into an

internal format that R recognizes (i.e. NA, not available) – Replace all unreasonable values into NA

• Unreasonable values include s – Daily precipitation amounts less than zero – Daily maximum temperature less than daily minimum

temperature. • QC also identifies outliers in daily maximum and minimum

temperature. The outliers are daily values outside a region defined by the user

Load RClimdex Load Data->Run QC Indices Calculation

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• Select “Load Data and Run QC” from the RClimDex Menu to open a window

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QC result 1. ____tempQC.csv unreasonable temperature 2. ____prcpQC.csv unreasonable precipitation 3. ____tepstdQC.csv all possible outliers in daily

temperature with the dates on which those outliers occur 4. ____indcal.csv QC’d data and will be used for the

indices calculation

Note: The indices are computed from the QC’d data. If a user modifies the original data file to correct some of the problematic values, the Load Data and Run QC procedure needs to be performed again before continue to the next steps

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• RClimDex computes 27 core climate indices • Parameters input:

– First and last year of base period for the threshold calculation

– Station Latitude (South hemisphere (-)) – Daily precipitation threshold, P (in mm) – Upper and Limit of Day High – Upper and Limit of Day Low

Load RClimdex Load Data->Run QC Indices Calculation

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Calculation done

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• Selection of indices • Outputs are stored as the excel and jpeg files

(folder) • Jpeg file format: trends computed by linear

least square (solid line) and locally weighted linear regression (dashed line)

Load RClimdex Load Data->Run QC Indices Calculation

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linear least square

locally weighted linear regression

THANK YOU

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Hands-on Rclimdex tutorial

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Accessing climate data from NOAA data center

• Go to http://www.ncdc.noaa.gov/ • Select Data Access > Land Base station • Select Climate data Online (CDO) • Select Search Tool

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• Fill the form and click “SEARCH”

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• Select “View Full detail”

• Select “see station list below”

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• The data link will be sent by email

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