論文ID: 2021-066
The dual peak semidiurnal variation in surface rainfall rate over the tropics, simulated by a 3.5-km mesh Non-hydrostatic Icosahedral Atmospheric Model (NICAM) for 26-31 December 2006, is analyzed and compared with data from the 17-year winter precipitation climatology of Tropical Rainfall Measuring Mission (TRMM) TMI (TRMM Microwave Imager), Precipitation Radar (PR), and the same 6-day data of Global Satellite Mapping of Precipitation, as well as infrared data from geostationary satellites.
We focus on land areas including southern Africa and the Amazon. Over these land areas, the NICAM simulation captures the primary peak in the afternoon and the secondary peak in the early morning, at similar times to those captured by TRMM data. In the PR observation, the primary peak of rainfall is mainly due to convective rain, whereas the secondary peak is due to stratiform rain. In the NICAM simulation, if a simple method is used for classification of convective/stratiform rain, convective rain is dominant all day long and the rainfall rate is generally higher than in the PR observation. However, an analysis of deep convection (DC) areas indicates consistency between the observation and NICAM; the primary peak of rainfall rate occurs at the mature stage of the number of DC areas, while the secondary peak occurs when the mean size of DC areas is almost at its highest point. In the NICAM simulation, however, the relative magnitudes of the two peaks are not represented well, and the contribution of the stratiform rain is underestimated.
The present study indicates that a high-resolution global nonhydrostatic model like NICAM has the potential to overcome the limitations of coarse-resolution general circulation models by reproducing evolution of deep convection, though there is room for improvement.
