Validation analyses after the altitude change of TRMM

The altitude of the Tropical Rainfall Measuring Mission (TRMM) satellite was raised from 350km to 402.5km in August 2001 in order to extend its lifetime. The minimum detectable value of Z-factor after the boost is 1.2dB higher. We compared the actual PR products before and after the altitude increase using statistical methods in order to verify the algorithms and the Precipitation Radar (PR) rain products after the orbit was raised, and to confirm the influence of raising the orbit on PR rain products. The reflectivity factor histograms do not exhibit any significant changes after the raising of the satellite, except for a 1.2dB increase of the minimum detectable value. The results are consistent with the estimation before the raising. The monthly global average of the conditional rain rate in 3A25 product increased 0.2 mm/h after the orbit raising. This result corresponded to the simulated rainfall average estimated from the 1C21 product before the raising. Changes in monthly global rainfall average of unconditional rain, height of rainfall and height of bright band due to the orbit raising were not significant. This result shows that the orbit change had little influence on the PR estimation.