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Browsing by Author "Haynes, John M., author"

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    The near-global distribution of light precipitation from CloudSat
    (Colorado State University. Libraries, 2008) Haynes, John M., author; Stephens, Graeme L., advisor
    The W-band (94 GHz) Cloud Profiling Radar (CPR) on CloudSat is sensitive to both clouds and precipitation. A precipitation retrieval applicable to space-borne, millimeter wavelength radars is introduced. Measurements of the attenuated backscatter of the surface are used to derive the path integrated attenuation (PIA) through precipitating columns, which follows from the clear-sky scattering characteristics of the surface. Over ocean, this can be estimated as a function of near-surface wind speed and sea surface temperature. Assuming an exponential rain drop size distribution, the relationship between PIA and rain rate is derived from Mie theory for homogeneous columns of warm rain. Multiple scattering is found to be significant for rainfall rates exceeding 3 to 5 mm h-1. To correct for this effect, Monte Carlo modeling is used to simulate the relationship between rainfall and PIA for various vertical precipitation profiles. Multiple scattering is found to increase return power to the radar, acting opposite attenuation. A model of the melting layer is also incorporated to better represent attenuating characteristics near the bright band, where snow aggregates melt into rain. It is found that failure to account for extra attenuation caused by melting particles results in overestimation of precipitation rate. The retrieval algorithm is applied to near-global CloudSat observations. Precipitation in the tropics is found to prefer clouds with lowest-layer cloud tops near 2 and 15 km. A third mode, likely associated with congestus, is found to be common in the tropical western Pacific, Indian, and Atlantic basins. There are vast regions of the globe where nearly all precipitation falls from cloud with lowest-layer tops below 4.75 km. Over the tropical oceans as a whole, precipitation falls twice as often from these clouds as any other cloud type. Furthermore, multiple layered cloud systems are found to be ubiquitous globally. In the tropics, it is estimated that half the accumulated precipitation comes from multiple layered systems rather than the classic "deep convective" model. Outside the tropics, the CPR observes precipitation more often than the passive microwave AMSR-E, with greater resulting seasonal accumulations.