Synergy of Multiple Satellite Observations in the Study of Cloud Thermodynamics of Tropical Deep Convection.

Abstract

Tropical convection lies at the heart of atmospheric research, especially for global weather and climate predictions; satellite measurements with large spatial coverage provide valuable information to deepen and broaden our scientific understandings of this subject. This thesis is motivated to utilize satellite measurements with assistance of modeling tools in a synergistic way to study tropical deep convection. First a generic parallax correction method is proposed to remove the biases resulting from the mismatch of satellite footprints due to different sensor viewing angles targeting the same object. Second a non-blackbody correction is proposed to better estimate cloud top temperature utilizing the vertical structure within the cloud top layer probed by CloudSat and CALIPSO. The distance between the physical cloud top and the effective emission level is shown to have a linear dependence on cloud top fuzziness (CTF; difference between cloud top and 10dBz radar echo) when CTF is less than ~2km. Beyond this threshold, the effective emission level remains 0.74km below the cloud top due to the saturation of IR absorption and emission. This relationship clearly improves simulated MODIS radiances comparing with the observed counterparts. The distribution of cloud top buoyancy for tropical deep convections derived using cloud top and ambient condition indicates that convective development is sensitive to both land-ocean contrast and diurnal cycle. Under certain assumptions, vertical velocity inside the convective core is derived and the result is consistent with typical vertical velocity profiles observed by air-bone Doppler radars for tropical deep convections, such as the altitude for the maximum vertical velocity and the existence of a weak detrainment layer in the mid-troposphere. GCM simulations indicate that overshooting deep convection could be responsible for the vertical transport of black carbon into the stratosphere especially over the India subcontinent during South Asia summer monsoon, and that black carbon in the stratosphere is transported upward at as large as twice the speed of water vapor transport. To explore a possible observational strategy for such injection of black carbon into the stratosphere, a limb-view infrared detection method is proposed based on forward modeling of radiative transfer and the simulated profiles.PhDAtmospheric, Oceanic and Space SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/109016/1/cpwang_1.pd