Implications of the differences between daytime and nighttime CloudSat observations over the tropics

Using 1 year of CloudSat level 2B Cloud Geometrical Profile product, the vertical structures, geographical distributions, and seasonal variations of cloud occurrence at the daytime (1330 LT) and the nighttime (0130 LT) overpasses and their differences over tropical land and ocean are presented separately. The differences between the cloud and precipitation occurrence at 0130 and 1330 LT and the 24 h mean are quantitatively evaluated using climatologies of diurnal variation from 9 years of TRMM observations. Then the vertical structures, geographical distributions, and seasonal variations of cloud and precipitation near the two CloudSat overpass times are generated from 9 years of TRMM observations and compared to those from CloudSat. Larger differences between cloud and precipitation occurrences at 0130 LT and those at 1330 LT were found at high altitudes because the amplitude of diurnal variation increases with height. Cloud and precipitation occurrences show day versus night differences which are opposite with respect to each other in the upper troposphere over the tropics. For example, near 1330 LT over tropical oceans, there are more clouds, but less precipitation at 13–14 km than near 0130 LT except over Panama. This may be explained with the phase lags between precipitation and clouds in the life cycles of the convective systems over land and ocean. The differences between the seasonal cycles of cloud and precipitation sampled at the 0130 and 1330 LT A-Train overpass times and the seasonal cycles generated from full day samples are shown.