This investigation focuses on developing a better understanding of the assorted mechanisms controlling the global
distribution of diurnal rainfall variability. The horizontal distributions of precipitation's diurnal cycle, based on eight
years of TRMM Microwave Imager (TMI) and TRMM Precipitation Radar (PR) measurements involving three TRMM
standard algorithms, are analyzed in detail at various spatiotemporal scales. Results demonstrate the prominence of the
late-evening to early-morning precipitation maxima over oceans and the mid- to late-afternoon maxima over continents,
but also reveal a widespread distribution of secondary maxima occurring over both oceans and continents, maxima
which generally mirror their counterpart regime's behavior. That is, many ocean regions exhibit clear-cut secondary
afternoon precipitation maxima while many continental areas exhibit just as evident secondary morning maxima.
Notably, this investigation represents the first comprehensive study of these secondary maxima and their widespread
nature when analyzed using a global precipitation dataset. The characteristics of the secondary maxima are thoroughly
mapped and described on a global grid. In addition, a Fourier harmonic decomposition scheme is used to examine
detailed amplitude and phase properties of the primary and secondary maxima -- as well as tertiary and quartern modes.
Accordingly, the advantages, ambiguities, and pitfalls resulting from using harmonic analysis are also examined.
Recent improvements in a method for remotely sensing precipitation and latent heating distributions based upon satellite-borne, passive microwave radiometer observations are summarized. In applications to synthetic data, estimated rainfall rates at sensor footprint-scale (14 km) are subject to significant random errors, but these errors are substantially reduced by spatial averaging. After spatial-averaging, rain rate and latent heating profile estimates exhibit biases that arise from a lack of specificity in the information contained in the microwave radiance data.
The retrieval method is applied to observations from the Tropical Rainfall Measuring Mission Microwave Radiometer (TMI). Retrieved instantaneous precipitation and heating distributions show general self-consistency and delineate plausible storm structures in an application to TMI observations of a mesoscale convective system over the tropical North Atlantic. Well-known climatological distributions of rainfall are reproduced by global, monthly-mean TMI precipitation estimates from July 2000. Zonal-mean heating profiles in the Tropics from the same period exhibit a primary maximum of heating near 7 km altitude and a secondary peak near 3 km, while at higher latitudes in the Southern Hemisphere, a vertical structure with heating aloft and cooling at lower altitudes is derived.
Rainfall retrieved from space-borne instruments has been accepted as reliable and accurate by a majority of the atmospheric community. One of the Tropical Rainfall Measuring Mission (TRMM) facility rain algorithms is the passive microwave-based rain retrieval algorithm (2A-12). In order to introduce latent heating as a product of 2A-12, many improvements have been made to the current Version 5 algorithm. This paper shows how these modifications impact retrieved surface rainfall rate and latent heating estimates. Comparisons indicate that the error statistics for the prototype Version 6 2A-12 are similar to those of Version 5 at footprint-scale and 30-km resolution; however, consistent latent heating vertical profiles are now obtainable. Preliminary comparisons to dual-doppler radar-based estimates show similar heating structures, but further study will be required to establish the general credibility of 2A-12 latent heating estimates.
Conference Committee Involvement (1)
Remote Sensing System Engineering IV
12 August 2012 | San Diego, California, United States
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