BLACK CARBON (BC) AEROSOLS EMANATING FROM BIOMASS AND FOSSIL FUEL BURNING SOURCES PROVIDE SUBSTANTIAL HEATING TO THE ATMOSPHERE AND COOLING OF THE SURFACE ACROSS LARGE REGIONS OF THE TROPICS AND NORTHERN HEMISPHERE EXTRA-TROPICS BECAUSE OF AEROSOL INTERACTION WITH SOLAR RADIATION. THIS MODIFICATION OF THE DAYTIME AIR TEMPERATURE BY AEROSOLS HAS BEEN DOCUMENTED TO IMPACT CLOUD COVERAGE AND IS OFTEN CALLED THE SEMI-DIRECT EFFECT. THIS EFFECT IS HYPOTHESIZED TO REDUCE CLOUDS IN SOME LOCATIONS AND INCREASE CLOUDS IN OTHERS PARTLY DEPENDING ON THE RELATIVE VERTICAL DISTRIBUTION OF THE AEROSOL AND CLOUDS. NEVERTHELESS OBSERVATIONAL STUDIES AS WELL AS GLOBAL CLIMATE MODEL SIMULATIONS OFFER DIFFERING MAGNITUDES AND EVEN DIFFERING SIGNS FOR THE RESPONSE OF LOW CLOUDS TO ABSORBING AEROSOLS. HENCE A DEEPER PHYSICAL UNDERSTANDING OF THE CLOUD RESPONSE IS REQUIRED TO EVALUATE CLIMATE MODEL REPRESENTATIONS OF THE SEMIDIRECT EFFECT AND ITS RESULTING RADIATIVE FORCING. TOWARD THIS GOAL WE PROPOSE TO EXPLOIT ACTIVE AND PASSIVE OBSERVATIONS TOGETHER WITH PHYSICAL INTERPRETATION FROM AN ATMOSPHERIC PHYSICS AND CHEMISTRY MODEL TO EXPLORE IN A VARIETY OF REGIONS AROUND THE GLOBE THE RESPONSES OF ATMOSPHERIC TEMPERATURE STABILITY AND CLOUDS TO VARIATIONS IN BC AEROSOLS. WE WILL EVALUATE TWO HYPOTHESES: (1) THAT THE PRESENCE OF DAYTIME HEATING BY AEROSOL ABSORPTION CAN BE DIAGNOSED FROM A DEPENDENCE ON AEROSOL OPTICAL THICKNESS OF THE CONTRAST BETWEEN DAYTIME AND NIGHTTIME AIR TEMPERATURE IN SATELLITE SOUNDING DATA; AND (2) THAT LOW CLOUD THICKNESS AND COVERAGE GENERALLY INCREASE IN REGIONS OF SIGNIFICANT ABSORBING AEROSOL. WE AIM TO EXPLOIT THE DIFFERENT EQUATOR CROSSING TIMES OF THE AQUA AND METOP-2 SATELLITE TO RESOLVE THE DIURNAL SIGNAL OF BC AEROSOL ABSORPTION IN THE PROFILE OF LOWER-TROPOSPHERIC TEMPERATURE. WE WILL FURTHER RELATE THESE RESULTS TO HORIZONTAL SAMPLING OF CLOUD PROPERTIES FROM MODIS AND AMSR-E ON AQUA AS WELL AS THE VERTICAL DISTRIBUTION OF AEROSOLS AND CLOUDS FROM CLOUDSAT AND CALIPSO. KEY ELEMENTS OF THE STRATEGY INCLUDE: (1) USING RECENTLY PUBLISHED OMI AND MODIS DIAGNOSTICS FOR AEROSOL OPTICAL THICKNESS ABOVE CLOUD TO DETERMINE THE KEY REGIONS FOR SEMI-DIRECT AEROSOL FORCING; (2) DEVELOPING A SEASONALLY AND DIURNALLY RESOLVED CLIMATOLOGY OF THE VERTICAL DISTRIBUTIONS OF AEROSOL AND CLOUD FOR EACH KEY REGION; (3) UTILIZING AIRS AND IASI TEMPERATURE RETRIEVALS TO DIAGNOSE THE PROFILE OF DAY/NIGHT TEMPERATURE CONTRAST AND EVALUATING ITS MAGNITUDE COMPARED TO AEROSOL OPTICAL THICKNESS IN THE CLEAR SKY AND ABOVE CLOUD; (4) EVALUATING THE DEPENDENCE OF MICROPHYSICAL AND MACROPHYISCAL CLOUD PROPERTIES ON AEROSOL OPTICAL THICKNESS IN THE CLEAR SKY AND ABOVE CLOUD; AND (5) APPLYING A LAGRANGIAN PARCEL TRACKING SCHEME AND SENSITIVITY STUDIES WITH THE WRFCHEM MODEL TO TEST THE PHYSICAL INTERPRETATION FROM THE EMPIRICAL STUDY AS WELL AS TEST FOR CHANGES IN CLOUD THAT ARE MERELY COINCIDENTAL WITH ABSORBING AEROSOL. THIS STUDY WILL BUILD ON PRIOR RESULTS BY BROADLY APPLYING SUCCESSFUL ANALYTICAL APPROACHES THAT HAVE SO FAR BEEN APPLIED ONLY TO LIMITED GEOGRAPHICAL AREAS. WE SEEK AN EMPIRICAL DETERMINATION OF CHANGES IN STATIC STABILITY AND CLOUDS ATTRIBUTABLE TO BC AEROSOL RADIATIVE EFFECTS ACROSS A BROADER RANGE OF CLIMATE REGIMES. THE STUDY WILL DRAW ON A WIDE ARRAY OF EARTH OBSERVING SATELLITE DATA SETS INCLUDING CALIPSO CLOUDSAT AIRS IASI MODIS OMI AND AMSR-E. THIS STUDY IS RESPONSIVE TO SECTION 2.1.1 OF THE SCIENCE OF TERRA AQUA AND SOUMI NPP PROGRAM: MULTI-PLATFORM AND SENSOR DATA FUSION AND COMBINES MULTIPLE AQUA DATA PRODUCTS WITH OBSERVATIONS FROM THE IASI INSTRUMENT ON THE METOP-2 SATELLITE AND ALSO APPLIES DATA FROM THE CALIPSO CLOUDSAT AND AURA SATELLITES.