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This review summarizes the general developments of the operational mesoscale model system based on the Global / Regional Assimilation and Prediction System-Tropical Monsoon Model (GRAPES-TMM) at the Guangzhou Regional Meteorological Center. GRAPES-TMM consists of the Tropical Regional Atmospheric Model System for the South China Sea (TRAMS, a typhoon model with a horizontal resolution of 9 km), the Mesoscale Atmospheric Regional Model System (MARS, 3km) and the fine-scale Rapid Update Cycling (RUC, 1km) forecasting system. The main advances of model dynamical core and physical processes are summarized, including the development of the 3D reference atmosphere scheme, the coupling scheme between dynamics and model physics, the calculation of nonlinear terms by fractional steps, the gravity wave drag scheme induced by sub-grid orography and a simplified model for land-surface scheme. The progress of model applications is reviewed and evaluated. The results show that the updated 9-3-1 forecasting system provides an overall improved performance on the weather forecasting in south China, especially for typhoon-genesis and typhoon-track forecasting as well as short-range weather forecasting. Capabilities and limitations as well as the future development of the forecasting system are also discussed. [ABSTRACT FROM AUTHOR]

A scheme of assimilating radar-retrieved water vapor is adopted to improve the quality of NWP initial field for improvement of the accuracy of short-range precipitation prediction. To reveal the impact of the assimilation of radar-retrieved water vapor on short-term precipitation forecast, three parallel experiments, cold start, hot start and hot start plus the assimilation of radar-retrieved water vapor, are designed to simulate the 31 days of May, 2013 with a fine numerical model for South China. Furthermore, a case of heavy rain that occurred from 8+9 May 2013 over the region from the southwest of Guangdong province to Pearl River Delta is analyzed in detail. Results show that the cold start experiment is not conducive to precipitation 12 hours ahead; the hot start experiment is able to reproduce well the first 6 hours of precipitation, but badly for subsequent prediction; the experiment of assimilating radar-retrieved water vapor is not only able to simulate well the precipitation 6 hours ahead, but also able to correctly predict the evolution of rain bands from 6 to 12 hours in advance. [ABSTRACT FROM AUTHOR]

Based on the Tropical Region Atmospheric Modeling System for South China Sea (TRAMS), Typhoon Roke (1115) and Sonca (1116) in 2011 which have large forecast errors in numerical operation prediction, have been selected for research focusing on the initial scheme and its influence on forecast. The purpose is to find a clue for model improvement and enhance the performance of the typhoon model. Several initialization schemes have been designed and the corresponding experiments have been done for Typhoon Roke and Sonca. The results show that the forecast error of both typhoons' track and intensity are less using the initial scheme of relocation and bogus just for the weak Typhoon Sonca, compared with using the scheme for both typhoons. By analysis the influence of the scheme on weak typhoon vortex circulation may be the reason that leads to the improvement. All weak typhoons in 2011 to 2012 are selected for tests. It comes to the conclusion that the initial scheme of relocation and bogus can reduce the error of track and intensity forecast. Besides, the height of cloud top in typhoon vortex constructed by bogus is too high according to weak typhoon. It is feasible to develop a bogus which is suitable for weak typhoon. [ABSTRACT FROM AUTHOR]

Satellite observations provide large amount of information of clouds and precipitation and play an important role in the forecast of heavy rainfall. However, we have not fully taken advantage of satellite observations in the data assimilation of numerical weather predictions, especially those in infrared channels. It is common to only assimilate radiances under clear-sky conditions since it is extremely difficult to simulate infrared transmittance in cloudy sky. On the basis of the Global and Regional Assimilation and Prediction Enhanced System 3-dimensional variance (GRAPES-3DVar), cloud liquid water content, ice-water content and cloud cover are employed as governing variables in the assimilation system. This scheme can improve the simulation of infrared transmittance by a fast radiative transfer model for TOVS (RTTOV) and adjust the atmospheric and cloud parameters based on infrared radiance observations. In this paper, we investigate a heavy rainfall over Guangdong province on May 26, 2007, which is right after the onset of a South China Sea monsoon. In this case, channels of the Moderate Resolution Imaging Spectroradiometer (MODIS) for observing water vapor (Channel 27) and cloud top altitude (Channel 36) are selected for the assimilation. The process of heavy rainfall is simulated by the Weather Research and Forecasting (WRF) model. Our results show that the assimilated MODIS data can improve the distribution of water vapor and temperature in the first guess field and indirectly adjust the upper-level wind field. The tendency of adjustment agrees well with the satellite observations. The assimilation scheme has positive impacts on the short-range forecasting of rainstorm. [ABSTRACT FROM AUTHOR]