Life cycle of deep convection and rainfall simulated in cloud-resolving model

 

Author

Toshiro Inoue — University of Tokyo

Category

Precipitation

Description

Cloud-system-resolving model (Nonhydrostatic Icosahedral Atmospheric Model; NICAM) represented semi-diurnal peaks of surface rainfall at afternoon and early morning over southern Africa of 15E–35E and Eq-25S. We constructed mean daily variation of near-surface rain using TRMM/PR and TMI from 3G68 data and found the same afternoon peak and early morning peak, although the TMI afternoon peak was slightly behind the PR. Temporal variation of areal coverage of deep convection (DC) defined by the infrared data showed significant diurnal variation instead of semi-diurnal variation. However, we found clear semi-diurnal variation in the mean size of DC at afternoon and early morning, when we studied the temporal variation of number and mean size of DC within the area of 15E–35E and Eq-25S. Although the afternoon peak of mean size is slightly behind the peak time of near-surface rainfall by TRMM/PR, the peak time of number of DC is close to the TRMM/PR peak time. The rainfall peak over the study area corresponds to the time when the number of DC is large, with an increase in the mean size of DC. Thus the afternoon peak of rainfall can be understood as the time when a large number of DC of developing stage occurred simultaneously. This temporal variation of number and mean size of DC can be seen in DC defined by OLR simulated by NICAM. The NICAM afternoon peak in surface rainfall also corresponds to the time when a larger number of the developing stage of DC occurred.