Semi-diurnal variation of surface rainfall studied from global cloud- system resolving model and satellite observations

摘要

We studied the semi-diurnal variation of surface rainfall over southern Africa and the Amazon simulated by a global cloud system resolving model (Nonhydrostatic ICosahedral Atmospheric Model; NICAM) under realistic conditions with land-sea contrast. This semi-diurnal variation was found to be consistent with the Tropical rainfall Measuring Mission (TRMM) and Meteosat-8 observations. The timing of the primary afternoon rainfall peak by the NICAM coincides with TRMM/PR primary afternoon peak, and the secondary early morning peak by the NICAM simulation agree with the TRMM/PR observations within two hours. Mean size of deep convection (DC), defined by 213K of the Meteosat-8 infrared data shows semi-diurnal variation, although the number of DC show diurnal variation with coincident peak with TRMM/PR primary peak. The semi-diurnal variation of the mean size of DC and number of DC is simulated with small secondary peak over southern Africa by NICAM, whose DC is defined by OLR smaller than 112 W m~(-2) (corresponding to 213 K in cumulative frequency).