Tropical Rainfall Measuring Mission microwave imaging capabilities for the observation of rain clouds


  • P. Bauer,

  • R. Bennartz


Brightness temperature simulations were used to assess the information loss due to the coarse spatial sampling of the Tropical Rainfall Measuring Mission (TRMM) microwave imager (TMI). While the high-resolution simulation of a three-dimensional rain cloud clearly identifies the 10.7-GHz channel to be superior for surface rainfall measurements, its comparably poor spatial resolution reduces the dynamic range of observable brightness temperatures and associated area-averaged rain rates considerably. This problem can be partly overcome by applying deconvolution techniques as demonstrated by Robinson et al. [1992]. When the sensitivity of resolution enhancement to noise amplification is investigated, an optimum configuration of key parameters was identified. Using an 11×11 matrix of neighboring pixels and noise reduction parameter of γ = 0.5° provides a 42×26 km resolution, compared with the original resolution of 63×38 km. Thus a noise amplification by a factor of 3 is introduced. Although this method does not match the resolution of the 19.35-GHz channel, the dynamic range of brightness temperatures and area-averaged rain rates could be increased by a factor of 2.7 and 2.2, respectively. Further resolution enhancement leads to noise levels which seem unacceptable with respect to the retrieval of geophysical parameters.