Microphysical Processes of Atmospheric Convective Systems
May 14, 2013 16:46:18
Description of Problem
Global precipitation intensity change is suggested to relate to the global warming according to observed evidences and model simulations. However, the physical processes accounted for the changes are still not resolved and the magnitudes of these change are poorly simulated. Cloud-Precipitation processes are usually parameterized in large-scale models especially for global climate and regional models. How the microphysical processes of atmospheric convective systems responses with the global warming is an important scientific issue. Exact representation of cloud microphysics in global climate model is a key point to study this scientific question. Therefore, we would use the Coupled fvGCM-GCE MMF (Multi-scale Modeling Framework) to study how precipitation intensity changes under warm and cool periods of sea surface or air temperatures.
Scientific Objectives and Approach
The fvMMF that replaces the sub-grid cloud parameterization with an explicit cloud-resolving model, is superior to the Goddard fvGCM (a convectional climate model) in many aspects. Simulations for 2005 and 2006 summer seasons are carried out via using this so-called super-parameterization model and the simulated results will be analyzed in detailed.
General verifications of MMF results will be investigated through comprehensive comparisons with other reanalysis dataset e.g. MERRA and other observational datasets such as AIRS, GPCP, TRMM and so on. Different dynamical and microphysical parameters will be examined to study their differences in 2005 and 2006 and we would try to figure out the physical processes accounting for the simulated and observed difference of these two years. We could get some useful information based on this work to know the proficiency and deficiency of the fvMMF and do some further model improvements.
In addition to the verifications, we will also be focusing on studying the precipitation intensity changes associated with different SST via investigating the responses of different dynamical, thermodynamic and microphysical parameters under the warmer atmosphere. As we knew the strong precipitation intensity is frequently contributed from tropical cyclones (TC), it is interesting and important to investigate how the skills of fvMMF to simulate TC in terms of tracks, numbers and intensity and to study whether the extreme heavy precipitation will be increased under warmer atmospheric environment.
General verifications of fvMMF results are done via comparisons with many relevant parameters among different datasets including MERRA, CFSR, GPCP, CMOPRH, TRMM, AIRS and MODIS. These parameters include precipitation rate, total precipitable water, total column cloud liquid water, total column cloud ice, SST, atmospheric stability, specific humidity, air temperature, relative humidity, OLR, CAPE, and precipitation intensity spectrum etc. The preliminary results show that most of these parameters are well-simulated by fvMMF in terms of their spatial distributions over most of regions around the globe. We have noticed that the convective processes simulated by fvMMF are more intensified than those of MERRA and satellite observations. The figure shows the total column cloud liquid water distributions of three datasets and their difference between 2005 and 2006 summers. We are ongoing to figure out the physical processes behind it.
We found that the precipitation intensity spectrum simulated by fvMMF and those of other reanalysis and satellite observational datasets are not consistent in their distribution patterns between light and heavy precipitations. More works are needed to investigate how modelers treat with convective and stratiform (large-scale) precipitations in their models regarding to fvMMF itself and models used by different reanalysis datasets. These will affect the response of precipitation intensity associated with different SST or air temperature.
Preliminary comparison of intensity and tracks of tropical cyclones of the two years for the major TC basins are done via animation combined with observed tracks. Objective TC tracking method is using to get TC statistics simulated by fvMMF.
Other Publications and Conferences
Shiu, C.-J., Liu, S. C., and J.-P. Chen (2010), Changes in Precipitation Extremes over Taiwan under Global Warming, Eos Trans. AGU, 91(26), West. Pac. Geophys. Meet. Suppl., Abstract A33A-147 (WPGM 2010, Taipei, Taiwan).