Adjustment of cross-track dependence of TRMM Precipitation Radar observation

The Tropical Rainfall Measuring Mission (TRMM) is NASA´s first mission dedicated to observing and understanding tropical rainfall and its effects on global climate. The Precipitation Radar in TRMM is the first spaceborne instrument designed to obtain three-dimensional maps of precipitation reflectivity. Such measurements yield information on the intensity and distribution of rain, rain type and storm depth. An advantage of space radar is that the scattering volume has similar size at any location. However, it has been a challenge to compare data to the one that is collected from the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) for varying scan angles. Intercomparisons between ground radar and spaceborne radar on a point-by-point basis can be a difficult task. Errors result from the mismatch between ground radar and spaceborne radar resolution volume, spatial alignment, and operating frequencies as well as the limited number of the data set collected instantaneously by both instruments. Differences in viewing aspects and resolution that result from the measurement of return signals from different volumes of the precipitation medium contribute to the intercomparison error. A study of the characteristics of the region of the bright band from TRMM-PR vertical profile measurements on a global scale indicates that while bright band height varies widely, the distribution of bright band structure does not vary around the globe. The results show that the average profile of the bright band vertical profile using bright band height as a reference point around the globe has unique profile and do not changes around the globe for large data set. This unique profile can be used to adjust the radar observation error due to different parameters. The TRMM-PR vertical resolution becomes poorer with increasing distance of the TRMM-PR samples from the nadir. Studying the model profile at the nadir profile and other profiles that are off-nadir ray can be used to b- uild the statistical model that can be used to adjust the effect of the scanning cross-track at angle far from the nadir-ray, and the results are presented.