Aerosol effect on cloud cover and cloud heightAerosol effect on cloud cover and cloud height

Kaufman, Koren, Remer, Rosenfeld & MartinsKaufman, Koren, Remer, Rosenfeld & Martins

1.1. Koren, I., Y. J. Kaufman L. A. Remer and J.V. Martins, Koren, I., Y. J. Kaufman L. A. Remer and J.V. Martins, Measurement of the effect of Amazon smoke on inhibition of Measurement of the effect of Amazon smoke on inhibition of cloud formation, cloud formation, ScienceScience, 303, 1342-1344, 2004. , 303, 1342-1344, 2004. http://climate.gsfc.nasa.gov/publications/fulltext/Koren_et_al._(2004).pdf

2.2. Kaufman, Y. J., I. Koren, L. A. Remer, D. Rosenfeld and Y. Kaufman, Y. J., I. Koren, L. A. Remer, D. Rosenfeld and Y. Rudich, Rudich, The effect of smoke, dust, and pollution aerosol on The effect of smoke, dust, and pollution aerosol on shallow cloud development over the Atlantic Ocean,shallow cloud development over the Atlantic Ocean, Proc. Proc. Nat. Acad. Scie., 102, 11207-11212, Nat. Acad. Scie., 102, 11207-11212, 20052005 http://climate.gsfc.nasa.

gov/publications/fulltext/PNAS-shallow_clouds.pdf

3.3. Koren, I. Y. J. Kaufman, L. A. Remer, D. Rosenfeld and Y. Koren, I. Y. J. Kaufman, L. A. Remer, D. Rosenfeld and Y. RudichRudich Aerosol impact on the development and coveragAerosol impact on the development and coverage of e of Convective clouds, Geoph. Res. Lett. Convective clouds, Geoph. Res. Lett. 32 (14): Art. No. 32 (14): Art. No. L14828 JUL 30 2005 L14828 JUL 30 2005 http://climate.gsfc.nasa.gov/publications/fulltext/2005GL023187.pdf

1. Smoke inhibition of cloud formation over the Amazon1. Smoke inhibition of cloud formation over the Amazon

Koren et al Science, 2004; Koren et al Science, 2004; Cloud fraction as function Cloud fraction as function of aerosol optical depth of aerosol optical depth (OD). The cloud fraction (OD). The cloud fraction decreases almost linearly decreases almost linearly with increasing OD. with increasing OD.

Clouds only

Clouds only

Smoke only

Smoke only

Impacts:Impacts:

• • smoke instantaneous forcing smoke instantaneous forcing -28w/m-28w/m22 --> +8w/m --> +8w/m22

• • smoke 24hrs forcing smoke 24hrs forcing -11w/m-11w/m22 --> -5w/m --> -5w/m22 • • less radiation at the surface => less evaporationless radiation at the surface => less evaporation• • smaller boundary layer cloud fraction smaller boundary layer cloud fraction

-28w/m-28w/m22

+8w/m+8w/m22

dustdust

smokesmoke

pollutionpollution

Sea saltSea salt

stratiformstratiform

convectiveconvective

convectiveconvective

2. 2. Aerosol effects on cloud Aerosol effects on cloud cover - shallow cloudscover - shallow clouds

The Atlantic Ocean - The Atlantic Ocean - several aerosol types several aerosol types interacting with cloudsinteracting with cloudsJune-Aug 2002June-Aug 2002

Pollution zonePollution zone

Dust zoneDust zone

Smoke zoneSmoke zone

Marine aerosolMarine aerosol

Stratus Stratus and trade and trade cumuluscumulusCloudsClouds

10

12

14

16

18

20

22

-100 -80 -60 -40 -20 0

5-30N June-Aug 2002

0<AOT<0.10.1<AOT<0.20.2<AOT<0.30.3<AOT<0.4

Longitude

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

-100 -80 -60 -40 -20 0

5-30N June-Aug 2002

0<AOT<0.10.1<AOT<0.20.2<AOT<0.30.3<AOT<0.4

Longitude

DustDust

SmokeSmoke8

10

12

14

16

18

20

22

-50 -40 -30 -20 -10 0 10 20

Longitude

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

-50 -40 -30 -20 -10 0 10 20

0<AOT<0.10.1<AOT<0.20.2<AOT<0.30.3<AOT<0.4

Longitude

3. 3. Convective CloudsConvective Clouds

cleanclean hazyhazy

cleanclean hazyhazy

Cloud fractionCloud fraction Cloud fractionCloud fraction

Cloud top pressureCloud top pressure Cloud top pressureCloud top pressure

What does it mean to climate?What does it mean to climate?

The aerosol forcing corresponding to the increase in cloud The aerosol forcing corresponding to the increase in cloud cover is ~ 6w/mcover is ~ 6w/m22 in the June-Aug period over the Atlantic in the June-Aug period over the Atlantic OceanOcean

We see similar increases in other locations, depending on We see similar increases in other locations, depending on the aerosol content of black carbon.the aerosol content of black carbon.

How does it reconcile with global warming?How does it reconcile with global warming?

Takemura, Kaufman, Remer, Nakajima, submittedTakemura, Kaufman, Remer, Nakajima, submitted

x. What is the response of the cloud water path to 50 yr increase x. What is the response of the cloud water path to 50 yr increase in aerosol concentration?in aerosol concentration?

A. Fixed ocean temperatureA. Fixed ocean temperature B. feedback through ocean B. feedback through ocean temperaturetemperature

““The aerosol roadmap”The aerosol roadmap”0.1

1

10

100

1000

1960 1970 1980 1990 2000

Year

0

0.5

1

1.5

2

1960 1970 1980 1990 2000 2010

year

P(%)=6.7*10-6

(yr-1964.7)2+2.2*10

-5(yr-1964.7)

3 r=96%

• • MODIS is in unique position to measure the correlation MODIS is in unique position to measure the correlation of aerosol AOT and properties to cloud cover & heightof aerosol AOT and properties to cloud cover & height

• • We find increases in cloud cover on average of 0.05 We find increases in cloud cover on average of 0.05 →→ ~ 6 W/m~ 6 W/m22

• • We find an average increase in cloud height of ~ 400 m We find an average increase in cloud height of ~ 400 m (-40 mb)(-40 mb)

• • Model shows that long term aerosol cooling of the ocean Model shows that long term aerosol cooling of the ocean may compensate the aerosol effect on cloud cover may compensate the aerosol effect on cloud cover through impact on cloud microphysics through impact on cloud microphysics

Aerosol effect on cloud cover and cloud heightAerosol effect on cloud cover and cloud height