Aerosol effect on cloud cover and cloud height Kaufman, Koren, Remer, Rosenfeld & Martins

1.Koren, I., Y. J. Kaufman L. A. Remer and J.V. Martins, Measurement of the effect of Amazon smoke on inhibition of cloud formation, Science, 303, , Kaufman, Y. J., I. Koren, L. A. Remer, D. Rosenfeld and Y. Rudich, The effect of smoke, dust, and pollution aerosol on shallow cloud development over the Atlantic Ocean, Proc. Nat. Acad. Scie., 102, , Koren, I. Y. J. Kaufman, L. A. Remer, D. Rosenfeld and Y. Rudich Aerosol impact on the development and coverage of Convective clouds, Geoph. Res. Lett. 32 (14): Art. No. L14828 JUL

1. Smoke inhibition of cloud formation over the Amazon

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

Clouds only Smoke only Impacts: smoke instantaneous forcing -28w/m 2 --> +8w/m 2 smoke instantaneous forcing -28w/m 2 --> +8w/m 2 smoke 24hrs forcing -11w/m 2 --> -5w/m 2 smoke 24hrs forcing -11w/m 2 --> -5w/m 2 less radiation at the surface => less evaporation less radiation at the surface => less evaporation smaller boundary layer cloud fraction smaller boundary layer cloud fraction -28w/m 2 +8w/m 2

dust smoke pollution Sea salt stratiform convective convective 2. Aerosol effects on cloud cover - shallow clouds The Atlantic Ocean - several aerosol types interacting with clouds June-Aug 2002 Pollution zone Dust zone Smoke zone Marine aerosol

Stratus and trade cumulus Clouds Dust Smoke

3. Convective Clouds

cleanhazycleanhazy Cloud fraction Cloud top pressure

What does it mean to climate? The aerosol forcing corresponding to the increase in cloud cover is ~ 6w/m 2 in the June-Aug period over the Atlantic Ocean We see similar increases in other locations, depending on the aerosol content of black carbon. How does it reconcile with global warming?

Takemura, Kaufman, Remer, Nakajima, submitted x. What is the response of the cloud water path to 50 yr increase in aerosol concentration? A. Fixed ocean temperature B. feedback through ocean temperature

“The aerosol roadmap”

MODIS is in unique position to measure the correlation of aerosol AOT and properties to cloud cover & height MODIS is in unique position to measure the correlation of aerosol AOT and properties to cloud cover & height We find increases in cloud cover on average of 0.05 → ~ 6 W/m 2 We find increases in cloud cover on average of 0.05 → ~ 6 W/m 2 We find an average increase in cloud height of ~ 400 m (-40 mb) We find an average increase in cloud height of ~ 400 m (-40 mb) Model shows that long term aerosol cooling of the ocean may compensate the aerosol effect on cloud cover through impact on cloud microphysics Model shows that long term aerosol cooling of the ocean may compensate the aerosol effect on cloud cover through impact on cloud microphysics Aerosol effect on cloud cover and cloud height