The Research On Landslide Disasters Forecasting Based On Mesoscale Numerical Model MM5 Over Three-Gorge Reservoir

Geological hazards are one of the most serious natural hazards in China. Three-Gorge Reservoir is the most serious and frequency zone where occurs geological hazards specially landslide hazards, which causes tremendous economy loss and casualty every year. Precipitation is closely related to the occurrence of landslide hazards and heavy rainfall processes such as rainstorms are the important factors that trigger the geological disasters. Numerical weather forecast is an effective means in present-day weather forecast. It is a new way to prevent and alleviate disasters' loss of three-Gorge Reservoir by using mesoscale numerical model to forecast landslide disasters combined with forecast equation based on precipitation for them. So this work will be not only a scientific significance but also give rise to important social and economy value. Combined the project of "Research on the monitoring and forecasting geological disasters triggered by heavy rain over Three-Gorge Reservoir", the basic characters of geological disasters, forecast equation on landslides, the capability of mesoscale numerical simulation MM5V3 and its application in landslide disasters forecasting over Three-Gorge Reservoir are researched.In this paper firstly we have briefly introduced the basic characters of mountain disasters in Three-Gorge Reservoir, and then our attention is laid stress on the relationship between landslides and their antecedent rainfall in the area, at last Fisher discriminate technique has been used in order to establish a forecast equation about rainfall for the occurrence of landslides. Based on the brief introduction of mesoscale numerical model MM5V3, twenty-two heavy rainfall processes in Three-Gorge Reservoir and the cause of a typical heavy rainfall are simulated by using MM5V3. In addition, the capability of MM5V3 to stimulate precipitations and weather patterns is analyzed. At last, a test for landslide disaster which occurred on May 13 ,2002 in Yichang city has been forecasted by the results of MM5V3 and the landslide forecast equation.The results showed that in Three-Gorge Reservoir mountain disasters mainly happen in rainy season, which occur the most frequency in July. There are many kinds of mountain disasters and landslides are most serious and precipitation is the primary factor that triggers the mountain disasters. Based on the previous analysis we have found that in this areas the occurrence of landslides is closely relative to two factors of rainfall and two different rainfall patterns triggered landslides are deduced, one type is days of heavy rain and the other is precipitation of the current day of landslides and previous days, and there are two types of precipitation triggered the geological disasters. The forecast equation based on above two factors of rainfall has the ability to forecast the occurrences of landslides of Three-Gorge Reservoir, and the results will be a scientific basis for preventing geological disasters in Three-Gorge Reservoir.Mesoscale numerical model MM5V3 is capable of stimulating most heavy rainfall in Three-Gorge Reservoir. The whole TS, the accuracy of strong rainfall and the one of heavy rainfall are higher than MAPS model. To simulation of weather patterns, the capability of stimulation to 850hPa is not as good as the one to 500hPa, which may be caused by underlying surface. In addition, the capability of stimulation to 48h is also not as good as the one to 36h. By analysis of result of stimulation to heavy rainfall happened on 8 July, 2003, we have found that rain belt location and its heavy rain core amounts in sensitivity run are preferably displayed by MM5V3. Analyses indicate this event was in close relationship with the southwest low vortex moving to east from the Tibetan Plateau and low-level jet in front of vortex and shear line.The result of single test shows that it is well forecasted for the landslides on May 13,2002 in Yichang city by using the result of MM5V3 and the landslide forecast equation; Combined with forecast equation for landslides with rainfall in Three...