Analysis And Evaluation Of Hydrometeors Based On Satellite And Model Datasets

Cloud is an important phenomenon, and an important factor that influence climate as well. Because of the inadequacy in understanding the formations and changes of clouds, clouds and cloud feedbacks have become the major uncertainties in estimating climate change with models. Hydrometeor contents are physical quantities that describe the mass of water in clouds. Distributions and changes of hydrometeors are directly related with appearance and phase of cloud. Hydrometeors also show the composite manifestation of cloud structures and microphysical characteristics. So obtaining a comprehensive knowledge about hydrometeor contents is crucial in understanding the radiative properties of cloud, and in improving the performance of models.Using multiple satellite observations, reanalysis, climatological characteristics about the cloud water path (CWP), liquid water path (LWP) and ice water path (IWP) on both global scale and East Asia are analyzed. What is more, two meso-scale numeric models, i.e. Advanced Regional Eta-coordinate Model (AREM) and Weather Research and Forecasting (WRF) are used to simulate typhoon "Chaba". And then, the simulated hydrometeors are evaluated by using measured and retrieved products of TMI. The preliminary results are listed as follows.(1) Global climatological characteristics of hydrometeorsBased on cloud datasets from International Satellite Cloud Climatology Project (ISCCP), Special Sensor Microwave/Imager (SSM/I), Microwave Limb Sounder (MLS) as well as European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Reanalysis (ERA-Interim) and National Centers for Environmental Prediction (NCEP) Climate Forecast System Reanalysis (CFSR), climatological characteristics and trend of hydrometeors over the globe are discussed.The result from ISCCP, ERA-Interim and CFSR shows that, distributions of CWP are greatly related with the large-scale circulation patterns and distributions of water vapor. Furthermore, cloud water shows great geographical incoherence. CWP on the lands are mainly located over rain forest in Central Africa, Southeast Asia, and South America; on the oceans, CWP are concentrated in ITCZ, SPCZ and the mid-latitudes in the northern and southern hemispheres. In the time period between1995and2009, CWP data of ISCCP, ERA-Interim and CFSR all show an increasing trend. Linear trends for each of the datasets are1.05g m-2yr-1(ISCCP),0.13(ERA-Interim) and0.18g m-2yr-1(CFSR).Results indicate that, LWP of ERA-Interim, CFSR as well as SSM/I show good agreement in magnitudes and distributions over the oceans, while LWP of ISCCP is drier than others. In the terms of IWP, ISCCP, ERA-Interim and CFSR show similar distribution pattern. Compared with IWP of ISCCP, ERA-Interim underestimates the magnitude, while CFSR produces more IWP. LWP of ISCCP, ERA-Interim and CFSR show consistent increasing trend over the oceans, while the trend of SSM/I is not significant. IWP of ISCCP shows an increasing trend over both lands and oceans.By analyzing MLS data, the results reveal that the upper tropospheric cloud ice is mainly distributed in the Central Africa, Southeast Asia, the Amazon Basin of South America, as well as the ITCZ and SPCZ. The distribution of IWC shows a good correspondence with the occurrences frequency of updraft at250hPa, and shows a remarkable seasonal variety. Compared with the retrieved data of MLS, ERA-Interim underestimated the cloud ice content, while CFSR overestimate the magnitude slightly.(2) Climatic characteristics of hydrometeors in East AsiaFocusing on the hydrometeors in East Asia, cloud products of ISCCP are analyzed. Cloud water is mainly concentrated in the windward side of the Pamir Plateau, Southwest China, East China, and Japan, with the maximum above140g m-2. Liquid water path centers are located in the Sichuan Basin and the East China Sea, this distribution is related to the enrichment of stratiform cloud in these areas. Distributions of ice water path show good agreement with orographic uplifting and convective activities. Ice water path over the Pamir Plateau, the Tibetan Plateau and East China Sea is higher than other regions.CWP and LWP in East China show higher magnitudes than those over Tibetan Plateau. But ice water path between the two regions shows no significant difference. Seasonal varieties of hydrometeors of the Tibetan Plateau and East China are different, which is caused by the different types of dominant cloud. The long-term trend over the Tibetan Plateau shows a growing trend in CWP and IWP, while LWP is decreasing. In East China, CWP, LWP and IWP exhibits an increasing trend.Reanalysis (ERA-Interim and CFSR) show consistent distributions and magnitudes with ISCCP in winter. Conversely, great departures can be found among the three datasets in summer. Moreover, seasonal verities and long-term trend of hydrometeors of reanalysis datasets also show some differences.(3) Evaluations of hydrometeors of meso-scale numerical models based on microwave productsUsing the measured and retrieved products of TMI and combined with microwave radiative transfer model, simulation capability of hydrometeor variables of typhoon Chaba (0417) in AREM and WRF are verified. Results indicate that, the simulated track and rain of typhoon are consistent with the best track and retrieved rain from TMI respectively. Furthermore, hydrometeor structures and distributions are verified with retrieved data from TMI directly. Then indirect-approach evaluation of hydrometeors is applied with the measured brightness temperatures (TBs). That is, the simulated hydrometeor variables as well as the simulated atmospheric structures (temperature, humidity, sea surface status) are used as input data of microwave radiative transfer model to calculate equivalent microwave TBs. By comparing simulated and measured TBs, hydrometeors structures of AREM and WRF are verified indirectly. The results show that, there are some deficiencies in representing hydrometeors in both AREM and WRF. The two meso-scale models overestimated liquid hydrometeors, and AREM underestimated ice hydrometeors, WRF shows a relatively good skill in representing ice hydrometeors than AREM.