Results Effect of mineral dust on cloud microphysics and precipitation of mesoscale convective systems Bing Lin 1 , Qilong Min 2 , and Rui Li 2 , Everette Joseph 3 , Yongxiang Hu 1 , Vernon Morris 3 , Shuyu Wang 2 1 NASA Langley Research Center , 2 State University of New York at Albany, 3 NOAA Center for Atmospheric Sciences Mineral dust & aerosol indirect effect As giant CCN, dusts may enhance the collision and coalescence of droplets and therefore increase warm precipitation formation and decrease cloud’s albedo. But they may also reduce ice particle sizes due to abundant ice nuclei (IN), thus increase lifetime and amount of ice clouds. Some observations show that dusts suppress clouds and precipitation. Objectives Introduction Approach Terra MODIS: Aerosol and cloud optical properties CERES: Radiation and climate forcing TRMM TMI: Cloud water and precipitation PR: Precipitation VIRS: Aerosol and cloud optical properties CERES: Radiation Aqua, GOES and METSAT Data Summary The probability density functions of rain water in convective and stratiform precipitation regions for both dusty and dust-free sectors (a), and corresponding evaporation rates (b). There are inconsistent evidences of aerosol indirect effects (AIE) on clouds and precipitation, and not enough observations of the impacts of dusts on rainfall internal structures. This study uses multi-platform and multi-sensor measurements to investigate detailed physical processes of cloud microphysics and precipitation that are affected by mineral dusts in a case of mesoscale convective systems. separation of DS and DF regions convection & stratiform precipitation dynamic variations in precip. clouds (DF, DS) changes in St. & Cu in DS regions statistics for the DS and DF regions dust indirect effects Selected case early March 2004 Sahara dust storm mesoscale convection dust-free (DF) and dusty (DS) regions (or sectors) Surface network: AMMA and AERNET Relative Humidity (%) 0 20 40 60 80 100 0 2 4 6 8 10 12 Air Temperature (k) 220 240 260 280 300 Height (km) 0 2 4 6 8 10 12 Diff_T (k) -2 -1 0 1 2 Diff_RH (%) -20 -10 0 10 20 Dust Dust-free Air temperature and relative humidity profiles in dusty and dust-free sectors derived form AQUA AIRS/AMSU on March 8 about 2:00 UTC sector: dusty (DS) dust-free (DF) convective clouds: weaker strong, variable stratiform aloft: stronger weak, variable bottom: similar more variable Log 10 ( Rain Water) -2 -1 0 1 PDF(%) 0 20 40 60 Log 10 (Rain Water) -3 -2 -1 0 1 Evaporation Rate (km -1 ) 0.0 .1 .2 .3 .4 Stratiform Convective Dust Stratiform Convective Dust-free (a) (b) -4 ~ 0 Meteosat-8 RGB composite visible image at 09:12UTC TMI precipitation image on at 09:11 UTC MODIS 03/08/04 0 ~ 4 Dusts transported up by the strong convection updraft acted as additional ice nuclei. Some of ice particles grown under this dusty condition were carried up to upper levels by the strong convective updraft and contributed to convective precipitation, and others were entered into the neighboring stratiform region and slowly settled downward in the upper layer of the cloud system until they reach the melting level. Consequences of microphysical effects of dusts were shifting precipitation size spectrum from heavy precipitation to light precipitation and suppressing precipitation. Dusts also enhanced evaporation processes, which further reduced the precipitation reaching surfaces. The microphysical processes of dust-cloud interaction had strong feedbacks to cloud thermodynamics and altered the vertical gradient of heating profiles in both convective and stratiform regions. Cloud system adjusted itself for IN changes and resulted in a weak but long lasting cloud system with increasing convective precipitation fraction and decreasing stratiform precipitation fraction.