Global spatiotemporal distributions of the fraction of precipitating and non-precipitating clouds during 2007–2016: Insights from the decadal observations of the CloudSat

The global climatology (spatial and temporal) of the total cloud fraction (precipitating cloud (rain cloud + snow cloud) + non-precipitating cloud) during 2007–2016 is investigated based on the observations derived from the CloudSat. It is revealed that the total cloud fraction occurs in the tropical belt (~±15° latitude) over all seasons. Among them, the mean fraction of precipitation clouds is ~12% observed in all seasons and dominates over the high-latitude oceans. The monthly mean fraction of precipitating clouds (~12%) is lower than the non-precipitating clouds (~35%) during 2007–2016. The distribution mode of rain cloud fraction is similar to that of a precipitation cloud in the mid-latitude and Intertropical Convergence Zone over the oceanic environment. In contrast, the precipitation cloud fraction has a greater snow cloud fraction in high latitudes (maximum of ~40%) over the hemispheres (north and south) during the winter season. Also, the snow cloud fraction presents a relatively inter-annual variation compared to rain clouds for all months, especially after 2011. It is attributed to the reduction of instrument detection performance, or the deviation of daytime detection data after 2011 and the sum of daytime and nighttime data before 2011. On the other hand, it may also be related to the increase of extreme precipitation under the effects of global warming, resulting in the increase of fluctuation in standard deviation year by year after 2011. The results obtained highlight the importance of cloud processes for the global hydrological cycle and may lead to an enhanced parameterization of precipitation in general circulation models.