Comparison of CloudSat and TRMM radar reflectivities

Abstract

Comparison of reflectivity data of radars onboard CloudSat and TRMM is performed using coincident overpasses. The contoured frequency by altitude diagrams (CFADs) are constructed for two cases: (a) only include collocated vertical profiles that are most likely to be raining and (b) include all collocated profiles along with cloudy pixels falling within a distance of about 50 km from the centre point of coincidence. Our analysis shows that for both cases, CloudSat underestimates the radar reflectivity by about 10 dBZ compared to that of TRMM radar below 15 km altitude. The difference is well outside the uncertainty value of ∼2 dBZ of each radar. Further, CloudSat reflectivity shows a decreasing trend while that of TRMM radar an increasing trend below 4 km height. Basically W-band radar that CloudSat flies suffers strong attenuation in precipitating clouds and its reflectivity value rarely exceeds 20 dBZ though its technical specification indicates the upper measurement limit to be 40 dBZ. TRMM radar, on the other hand, cannot measure values below 17 dBZ. In fact combining data from these two radars seems to give a better overall spatial structure of convective clouds.

The spatiotemporal structure of precipitation in Indian monsoon depressions

“…Repeating this analysis for Figure by comparison with the 94 GHz reflectivity CFAD composites over Africa from Young (), we build a very simlar picture: mixed with occasional convection at −10°; common convection at −4°; and common stratiform at 10°. Here we also note the strong attentuation in the higher frequency CloudSat radar reflectivity, particularly below 4 km, as also noted by Sindhu and Bhat ().…”

Importance of snow to global precipitation

“…Considerable attenuation is experienced by the 94 GHz signal due to dense ice particles and liquid water in convective clouds. Previous work has shown, through ground site and colocated spaceborne radar comparisons, that the CloudSat radar signal can be reduced by 10 dBZ or more [ Protat et al , ; Sindhu and Bhat , ]. Because the CloudSat radar reflectivity alone is unsuited to use as a direct estimate of precipitation rates in deep convective clouds, the formulation of methodologies that use the signal attenuation directly to estimate precipitation over the ocean [ Haynes et al , ] and also over the land [ Matrosov , ] has been developed.…”

Variation and Influencing Factors of Cloud Characteristics over Qinghai Lake from 2006 to 2019

“…The standardized CFAD states that the frequency of occurrence of a physical quantity at a certain height is the frequency of occurrence of the physical quantity at that height divided by the sum of samples at all heights. This method can analyze the cloud spectrum characteristics in detail [32,33]. The technology roadmap of this study is shown in Figure 2.…”