Transcript
Page 1: Some aspects on the Arctic energy budget and climatology

Some aspects on the Arctic energy budget and climatology

Nils Gunnar Kvamstø ([email protected])

Input from Asgeir Sorteberg, Igor Ezau, Vladimir Alexeev and Øyvind Byrkjedal

Page 2: Some aspects on the Arctic energy budget and climatology

OUTLINE OF THIS WEEKS LECTURES

1. Arctic Climatology 1

2. Arctic Climatology 2

3. Sea Ice – role, variability, mechanisms

4. Arctic climate variability and climate change

Page 3: Some aspects on the Arctic energy budget and climatology

2

,,2

1vLqgzTca

energystaticmoist

pE

dpvLqgzTcg

A

dpag

A

g

dpdz

dzaA

s

s

TOP

p

pE

p

EE

z

EE

0

2

0

0

2

11

1

ps

0ztop

0

FRAMEWORK

ENERGY CONTENT IN AN ATMOSPHERIC COLUMN

Hartmann (1994) Ch 6

Page 4: Some aspects on the Arctic energy budget and climatology

FQQRR

AVQQLLSSLS

t

A

sHsTOA

EsH

R

SSSS

R

TOAE

sTOA

)1(

40

RTOA

RS, QH+QS

[uAE] [uAE+d(uAE)]

dpVagt

A

y

va

x

ua

t

a

sp

EE

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)()(

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AE

CHANGE OF ENERGY WITH TIME

Page 5: Some aspects on the Arctic energy budget and climatology

sfcioioiE

EHsfcsfc

FFFSSLtt

O

QQRF

sfcETTE FFSL

tt

T

so

Li +Si

OCEANIC ENERGY BUDGET

TERRESTRIAL ENERGY BUDGET

L – Latent heat; S – sensible heat

Page 6: Some aspects on the Arctic energy budget and climatology

The Arctic energy budget

70˚N

Atmosphere:

•Net radiation at top of atmosphere

•Lateral transport

•Surface fluxes (radiation, turbulence)

Ocean:

•Surface fluxes (radiation, turbulence)

•Lateral transport (water)

•Latent heat (freezing/melting)

•Ice transport

Land Surface:

•Surface fluxes

Fresh water run off

Page 7: Some aspects on the Arctic energy budget and climatology

Annual means:dAE/dt =0,Fsfc = 11 Wm-2

Rtop=-110Wm-2

∆F = 100Wm-2

Residual 1Wm-2

∂AE/∂t <0 in autumn Rtoa decreases (SW decr) Fsfc + ∆F increases. Damp rad effect

∂AE/∂t < 0 in spring Rtoa increases (SW incr) Fsfc + ∆F decreases. Damp rad effect

When Rtoa ≈ 0 Fsfc ≈ -∆FBoth late spring and early autumn ∆F partly compensates sfc and toa fluxes

ANNUAL CYCLE

Serreze et al (2007)

ERA-40: Grided re-analysisUppala et al (2005)

Page 8: Some aspects on the Arctic energy budget and climatology

Residuals’ space and time dependency

Serreze et al (2007)

0

0

Annual cycle contd

Page 9: Some aspects on the Arctic energy budget and climatology

∆F – cosists mostly of dry static energy!

∆Fq ≈ Pr

Fsfc = Rs + QE + QH, Rs dominates

Often QH <0 due to inversion (small)

QE always positive

Serreze et al (2007)

Page 10: Some aspects on the Arctic energy budget and climatology

Assessment of ERA40 – comparison with sat.- and obs Data • ∆F well constrained (similar to NCEP)• Fsfc is in the upper range (2.5 – 11)

(1Wm-2 = 0.1m sea ice in 1 yr!!)• Fsfc too high. Inaccurate cloud properties in

ERA40• Excessive Rtop – too high content of

sensible heat• Remember satellite data are inaccurate as

well

Serreze et al (2007)

Page 11: Some aspects on the Arctic energy budget and climatology

Energy flux from surface to atmosphere during winter• Largest fluxes from open ocean QH QE

• Nearly 0 over land (QE into sfc [inversion] LW out)

Energy flux from atmosphere to surface during summer. • Largest over open ocean (SW and low albedo)• QE downward (melting ice & permafrost deepening active soil layer)

Fsfc in ERA40 are higher than in other datasets. Indication of systematic error.But, the active soil layer may have increased(tawing) over the last decades => more heat stored larger fluxes.

Serreze et al (2007)

Page 12: Some aspects on the Arctic energy budget and climatology

Serreze et al (2007)

Mean transport

Page 13: Some aspects on the Arctic energy budget and climatology

Time series of total transport

Pronounced annual cycleWeaker interannual cycleand low frequency variability.

Trends?

FQQRRt

AsHsTOA

E

2

,,2

1vLqgzTca

energystaticmoist

pE

Serreze et al (2007)

Page 14: Some aspects on the Arctic energy budget and climatology

ANNUAL ATMOSPHERIC ENERGY TRANSPORT

Andresen and Sorteberg (2009)

Page 15: Some aspects on the Arctic energy budget and climatology

Zonally averaged long term circulation – mean meridional circulation

Ferrel cell

Polar cell

EavPoleward transport by mean meridional circulation =

v

u

Deviations from mean matters as well –eddies

Wallace and Hobbs (2006)

Page 16: Some aspects on the Arctic energy budget and climatology

16

Mean height of 500 hPa surface January

Hartmann (1994) Ch 6

ATMOSPHERIC TRANSPORT BY EDDIES

Page 17: Some aspects on the Arctic energy budget and climatology

17

TvTvTvvT **

Total poleward heat tr = (tr by MMC) + (tr by qs eddies) + (tr by high freq eddies)

ATMOSPHERIC TRANSPORT

Page 18: Some aspects on the Arctic energy budget and climatology

18

Annual average northward energy flux

units in 1015 W

Page 19: Some aspects on the Arctic energy budget and climatology

19

Zonally averaged northward flux of heat by eddies

Hartmann (1994) Ch 6

Page 20: Some aspects on the Arctic energy budget and climatology

ATMOSPHERIC HEAT TRANSPORT

MMC - MEAN MERIDIONAL CIRCULATIONSE - STATIONARY EDDIESTE - TRANSIENT EDDIES

HEAT TRANSPORT ACROSS 60ºN

Largest portion below 500hPa

Max in 800-900hPa (1200-2500m)

Not much in the Atmospheric Boundary Layer

Page 21: Some aspects on the Arctic energy budget and climatology

The seasonal in/out flow of energy is longitude dependentBoth quasistationary waves and eddies contribute.Strong signatures from quasistationary waves in figure

W and E of N. American through

Transport below 3000m -> N.Atl more pronounced here

LONGITUDINAL DEPENDENCE OF ΔF

Page 22: Some aspects on the Arctic energy budget and climatology

654321

sfcioioiE

EHsfcsfc

FFFSSLtt

O

QQRF

3 neglected 2,4,5,6 -> observed => 1 residual5 – ice drift in the fram strait4 – estimated from model runs. Sum out/inflow Fram, Bering, Barents, Can Arc(may be dependent on comp method)

Ocean budget (+ atmosphere over ocean area only)

Serreze et al 2007

Page 23: Some aspects on the Arctic energy budget and climatology

S0/OE

Transport terms are steady => Annual cycle generated by Fsfc

Seasonal cycle comes mostly from Barents sea.Large heat content on Nov – due to adv – This contributes to secondary max in Li in Dec

Cycle gets lagged with depth

Page 24: Some aspects on the Arctic energy budget and climatology

ARCTIC CLIMATOLOGY

QUALITY CHECKED ARCTIC STATIONSFOR

CLIMATE STUDIES

Polyakov, 2003

START YEAR

Page 25: Some aspects on the Arctic energy budget and climatology

EXAMPLES OF SOME DRIFITING STATIONS

FRAM (1893-1896) MAUD (1922-1924) T-3 (1952-1971)

NP-STATIONS (1952-1993) RUSS. PATROL SHIPS (1952-1983) DARMS (1958-1975)

Example: Pol (1953-1959, 1972)

Example: NP-22 (1973-1982)

Arctic Climatology Atlas, 2002

Russ. Drifting Automatic Radiometeorological Stations

Page 26: Some aspects on the Arctic energy budget and climatology

2m temperature

Arctic Climatology Atlas, 2002

JANUARY APRIL

Page 27: Some aspects on the Arctic energy budget and climatology

2m temperature

Arctic Climatology Atlas, 2002

JULY OCTOBER

Page 28: Some aspects on the Arctic energy budget and climatology

TEMPERATURES AT SVALBARD

Annual

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

Te

mp

era

ture

(d

eg

C)

Bjørnøya Hopen Svalbard Airport Ny-Ålesund Jan Mayen

Page 29: Some aspects on the Arctic energy budget and climatology

Johannessen, 2003

Northern hemisphere temperature

Page 30: Some aspects on the Arctic energy budget and climatology

PRECIPITATION

Arctic Climatology Atlas, 2002

JANUARY APRIL

Page 31: Some aspects on the Arctic energy budget and climatology

PRECIPITATION

Arctic Climatology Atlas, 2002

JULY OCTOBER

Page 32: Some aspects on the Arctic energy budget and climatology

PRECIPITATION AT SVALBARDAnnual precipitation, % of 1961-1990 average

0.6

0.7

0.8

0.9

1

1.1

1.2

1.3

1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

Pre

cip

itat

ion

, % BjørnøyaHopenSvalbard AirportNy-ÅlesundJan Mayen

Page 33: Some aspects on the Arctic energy budget and climatology

PRECIPITATION GADIENTS COAST/INNLAND

Summer

0

50

100

150

200

250

300

350

Isjord Radio Barentsburg Svalbard Airport

Rati

o (

%)

to S

v.A

p.

Winter

0

50

100

150

200

250

300

350

Isjord Radio Barentsburg SvalbardAirport

Rati

o (

%)

to S

v.A

p.

Page 34: Some aspects on the Arctic energy budget and climatology

MEASURING ARCTIC PRECIPITATION

Undercatch, Norwegian gauge

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 2 4 6

Wind speed (m/s)

Co

rre

ctio

n f

acto

r

i=0.1 mm/h

i=1 mm/h

i=10 mm/h

T=0 degC

T= -5degC

T= -10degC

Ekspon. (T= -10degC)Ekspon. (T= -5degC)Ekspon. (T=0degC)Ekspon. (i=0.1mm/h)Ekspon. (i=1mm/h)Ekspon. (i=10mm/h)

Page 35: Some aspects on the Arctic energy budget and climatology

Liquid

10

15

20

25

30

35

40

45

50

1975 1980 1985 1990 1995 2000 2005

Fra

cti

on

(%

)

Solid

20

30

40

50

60

70

80

1975 1980 1985 1990 1995 2000 2005

Fra

cti

on

(%

)

Mixed

0

10

20

30

40

50

1975 1980 1985 1990 1995 2000 2005

Fra

cti

on

(%

)

Annual fractions of liquid, solid and mixed precipitation at Svalbard Airport

Page 36: Some aspects on the Arctic energy budget and climatology

SNOWDEPTH OVER THE ICE

Arctic Climatology Atlas, 2002

JANUARY APRIL

Page 37: Some aspects on the Arctic energy budget and climatology

SNOWDEPTH OVER THE ICE

Arctic Climatology Atlas, 2002

JULY OCTOBER

Page 38: Some aspects on the Arctic energy budget and climatology

SURFACE SHORTWAVE RADIATION: SW↓

Curry et al., 1996

OBSERVATIONAL BASED Curry and Ebert (1992)

SATELITE BASED (ISCCP, 1985) Rossow and Chang (1995)

JUNE

80ºN

Page 39: Some aspects on the Arctic energy budget and climatology

DOWNWARD LONGWAVE RADIATION AT SURFACE : LW↓

Curry et al., 1996

OBSERVATIONAL BASED Curry and Ebert (1992)

SATELITE BASED (ISCCP, 1985) Rossow and Chang (1995)

JUNE

80ºN

Page 40: Some aspects on the Arctic energy budget and climatology

CLOUD FRACTION

Curry et al., 1996

SATELLITE BASED (ISCCP)

60-90ºN

OBSERVATIONALLY BASED

OBSERVATIONALLY BASED(varying sky illumination corrected, Hahn et al., 1994)

SATELLITE BASED (ISCCP, new cloud detection algorithm)

Page 41: Some aspects on the Arctic energy budget and climatology

TOTAL CLOUDCOVER

APRIL

Arctic Climatology Atlas, 2002

JANUARY

LOW CLOUDCOVER

Page 42: Some aspects on the Arctic energy budget and climatology

TOTAL CLOUDCOVER

Arctic Climatology Atlas, 2002

JULY

LOW CLOUDCOVER

Page 43: Some aspects on the Arctic energy budget and climatology

CLOUDS

1. Norwegian Sea RegimeHigh cloudiness all year roundRelatively large amounts of cumulus in winter caused by warm water under cold air

2. East Siberian RegimeVery clear in winter due to anticycloneVery dryCirrus dominates

3. Polar Ocean RegimePronounced spring/summer maximum due to stratusForms over cooler ice surface

(warm advection. latent heat cooling)

Page 44: Some aspects on the Arctic energy budget and climatology

LOCAL EFFECT OF CLOUDS ON THE RADIATION BUDGET

SWLW

z

zclear

zcloud

zSW

zclear

zcloud

zLW

CRFCRFCRF

SWfSWfCRF

LWfLWfCRF

1

1

CLOUD RADIATIVE FORCING at a given level z is the difference in net radiation between cloudy and clear sky usually given in W/m2

LW longwave radiationSW shortwave radiation

f

SFCTOAATM CRFCRFCRF

Page 45: Some aspects on the Arctic energy budget and climatology

LOCAL EFFECT OF CLOUDS ON THE SURFACE RADIATION BUDGET

Curry et al., 1996

JUNE

80ºN SURFACE

OBSERVATIONALLY BASED Curry and Ebert (1992)

POSITIVE: WARMING AT SURFACE

NEGATIVE: COOLING AT SURFACE

Page 46: Some aspects on the Arctic energy budget and climatology

LOCAL EFFECT OF CLOUDS ON THE SURFACE RADIATION BUDGET

Curry et al., 1996

JUNE

80ºN SURFACE

OBSERVATIONAL BASED Curry and Ebert (1992) SATELITE BASED (ISCCP, 1985)

Rossow and Chang (1995)

NET CLOUD FORCING CRF POSITIVE: CLOUDS CAUSE WARMING AT SURFACEMOST OF THE YEAR EXCEPT SUMMER

CRF NEGATIVE: CLOUDS CAUSE COOLING AT SURFACEDURING SUMMER

Large uncertainty!

Page 47: Some aspects on the Arctic energy budget and climatology

LINKS BETWEEN ENERGY BUDGET AND CLIMATOLOGY

Nakamura and Oort, 1973

ANNUAL SUMMER WINTER

Most times of the year two big terms are:1. Heating by lateral advection 2. Cooling by longwave radiation to space

In summer:1. Heating by lateral advection2. Cooling by surface (latent heat from ice/snow melting)

REMEMBER THE TRANSTORT IS A VERTICAL AND HORIZONTAL INTEGRAL

SUMMARY:

Page 48: Some aspects on the Arctic energy budget and climatology

WINTERTIME ATMOSPHERIC CIRCULATION AND

LOW LEVEL TEMPERATURE

Page 49: Some aspects on the Arctic energy budget and climatology

LOW LEVEL ATMOSPHERIC CIRCULATION

Semipermanent Highs and Lows The Arctic is characterized by "semipermanent" patterns of high and low pressure.

These patterns are semipermanent because they appear in charts of long-term average surface pressure.

Aleutian Low This semipermanent low pressure center is located near the Aleutian

Islands. Most intense in winter, the Aleutian Low is characterized by many strong cyclones. Travelling cyclones formed in the subpolar latitudes in the North Pacific usually slow down and reach maximum intensity in the area of the Aleutian Low.

Icelandic Low This low pressure center is located near Iceland, usually between Iceland and southern Greenland. Most intense during winter, in summer, it weakens and

splits into two centers, one near Davis Strait and the other west of Iceland. Like its counterpart the Aleutian Low, it reflects the high frequency of cyclones and the

tendency for these systems to be strong. In general, migratory lows slow down and intensify in the vicinity of the Icelandic Low.

Page 50: Some aspects on the Arctic energy budget and climatology

ATMOSPHERIC LOW LEVEL CIRCULATION

Siberian High

The Siberian High is an intense, cold anticyclone that forms over eastern Siberia in winter. Prevailing from late November to early March, it is associated with frequent cold air

outbreaks over east Asia.

Beaufort High The Beaufort High is a high pressure center or ridge over the Beaufort Sea present mainly

in winter. The North American High is a relatively weak area of high pressure that covers most of North America during winter. This pressure system tends

to be centered over the Yukon, but is not as well-defined as its continental counterpart, the Siberian High.

Page 51: Some aspects on the Arctic energy budget and climatology

Low level T is not representative?

Trends in other budget terms?(sea-ice, radiation…)

A PARADOX?

Page 52: Some aspects on the Arctic energy budget and climatology

HOW WELL DO WE KNOW THE SURFACE RADIATION BUDGET?

Page 53: Some aspects on the Arctic energy budget and climatology

OBSERVATIONAL ESTIMATES THATCOVERS 70-90°N

The ECMWF (ERA40) reanalysis • 3-dimensional variational assimilation (T159L60)• Raw satellite radiances assimilated into the system• Satellite data from the Vertical Temperature Profile• Radiometer (VTPR) starting in 1973, TIROS Operational

Vertical Sounder (TOVS) data from late 1978

NCAR-NCEP reanalysis • 3-dimensional variational assimilation (T62L28)• No direct assimilation of radiative fluxes.• Estimate the vertical temperature and humidity profiles

through a series of empirical and statistical relationships• Satellite data from TIROS TOVS data from late 1978

Page 54: Some aspects on the Arctic energy budget and climatology

OBSERVATIONAL ESTIMATES THATCOVERS 70-90°N

SRB V2: Version 2 of the Surface Radiation Budget• ISCCP DX (30km res.) top of atmosphere (TOA) data and

clouds• Atmospheric water vapor: 4-D data assimilation using the

Goddard Earth Observing System model (GEOS-1).

POLAR ISCCP Version 1 polar radiation fluxes (Key et al. 1999).

• ISCCP-D1 (280km res.) data top of atmosphere (TOA) data and clouds

• Atmospheric water vapor: TOVS Pathfinder and ISCCP profiles

Advanced Very High Resolution Radiometer (AVHRR) Polar Pathfinder dataset (APP-X), Version 1 (Key, 2001).

• Extension of the standard clear sky products using the Cloud and Surface Parameter Retrieval (CASPR) system

Page 55: Some aspects on the Arctic energy budget and climatology

225 W/m2 99 W/m2

260 W/m2

45 W/m2

SW↓LW↓

SW↑

LW↑

LW↓ + SW↓ 324 W/m2

LW↑ + SW↑ 305 W/m2

SOURCE:ERA40, SRB V2, ISCCP

LW↓ 70%SW↓ 30%

Page 56: Some aspects on the Arctic energy budget and climatology

• Longwave radiation as an Arctic net energy sink ranges from 28 to 52 W/m2 • There is no consensus on the seasonal cycle of net LW radiation.• Shortwave radiation as a net energy source ranges from 43 to 50 W/m2

160

140

120

100

80

60

40

20

0

SURFACE LW↓-LW↑ SURFACE SW↓-SW↑

HOW MUCH NET ENERGY IS AVAILABEL AT THE SURFACE?

0

-10

-20

-30

-40

-50

-60

-70

W/m2 W/m2

Page 57: Some aspects on the Arctic energy budget and climatology

HOW WELL DO WE KNOW THE INCOMMINGENERGY?

• Annual downward LW radiation estimates range from 205 to 230 W/m2 • The spread in monthly values is typically 10–30 W/m2 • The amplitude of the seasonal cycle is not well constrained.• ERA40 has the largest seasonal cycle

265

300

SURFACE LW↓ DIFFERENCE IN SURFACE LW↓

320

300

280

260

240

220

200

180

160

W/m2

40

30

20

10

0

-10

-20

-30

-40

W/m2

Page 58: Some aspects on the Arctic energy budget and climatology

• The NCEP reanalyses has a strong bias in downward shortwave radiation• Annual downward SW radiation estimates range from 87 to 128 W/m2.• The monthly spread is typically 10–20 W/m2 during summer

SURFACE SW↓DIFFERENCE IN SURFACE SW↓

HOW WELL DO WE KNOW THE INCOMMINGENERGY?

300

250

200

150

100

50

0

W/m2

20

0

-20

-40

-60

-80

-100

W/m2

Page 59: Some aspects on the Arctic energy budget and climatology

• Annual downward radiation estimates range from 306 to 332 W/m2.• The monthly spread is typically 10–25 W/m2

HOW WELL DO WE KNOW THE SURFACE RADIATION BUDGET?

SURFACE LW↓ +SW↓

DIFFERENCE IN SURFACE LW↓+SW↓

600

500

400

300

200

W/m2

30

10

0

-10

-30

-50

-70

W/m2

Page 60: Some aspects on the Arctic energy budget and climatology

HOW WELL IS IT SIMULATED WITHCOUPLED GCMs?

Page 61: Some aspects on the Arctic energy budget and climatology

THE SURFACE RADIATION BUDGET IN COUPLED GCMs

INCOMING LONGWAVE ENERGY

Page 62: Some aspects on the Arctic energy budget and climatology

THE SURFACE RADIATION BUDGET IN COUPLED GCMs

INCOMING SHORWAVE ENERGY

Page 63: Some aspects on the Arctic energy budget and climatology

(IPCC AR4, 12 MODELS)

218 W/m2 ±12.0

89 W/m2 ± 8.0

307 W/m2 ±12.1

(ERA40,SRB V2, ISCCP)

LW↓ 225 W/m2

SW↓ 99 W/m2

LW↓ + SW↓ 324 W/m2

INCOMING ENERGY

LW↓ SW↓

W/m2 W/m2

IPCC ENSEMBLE MEAN

Page 64: Some aspects on the Arctic energy budget and climatology

ARCTIC CLIMATOLOGYATMOSPHERIC HEAT TRANSPORT

HOW IMPORTANT IS IT ?

ARCTIC ATM-SURFACE SYSTEM HAS A NET LOSS OF ENERGY

Hartmann, 1994

Page 65: Some aspects on the Arctic energy budget and climatology

• No Solar Radiation in Winter• Upward loss of heat from surface and atmosphere

by longwave radiation• Heat must be replaced or else temperatures would

drop to near absolute zero.

Where does the heat come from that replaces what is lost

from longwave radiation to space?

HORIZONTAL HEAT TRANSPORT

ARCTIC CLIMATOLOGY

Page 66: Some aspects on the Arctic energy budget and climatology

ARCTIC CLIMATOLOGY

ATMOSPHERIC PRESSURE SYSTEMS WINTERTIME


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