Urban Flood by Extraordinary Rainfall in Small River Basin

The extraordinary rainfall occurred in the small river basin （called Asano River） of Kanazawa city, Ishikawa prefecture middle part of Japan, July 2008. The center of the city was affected by severe damages by the big flood due to the extraordinary rainfall. This study aims to make clear the probability of the extraordinary rainfall, the mechanism of the flood, the flood fighting activities etc. and to prepare to the future big flood. For this purposes, the analysis of probability of rainfall events is carried out by use of three methods. They are Gumbel method, Hazen plot and Momentum method. The return period is estimated 250 years. Next runoff analysis by use of the Tank model method was carried out. This model consists of several series of rainfall storage tanks. The upper tank corresponds to surface runoff and the lower tank corresponds to inter runoff and ground water runoff. The result shows that the observed and simulated discharge is similar. So the future flood by the extraordinary rainfall events is able to predict the amounts of the flood. Finally, the problem of the flood fighting activity is cleared for the safety of the people in the river basin.

ANALYSIS OF TYPHOON MATSA (NO.0509) AFFECTING SHANDONG PROVINCE

The characteristics of the moving course of Typhoon Matsa (No.0509), associated heavy rain and physical quantities fields have been analyzed, with the focus on the reason of the typhoon’s abrupt northeastward turn in Anhui Province and heavy rain concentrating in the northeast of typhoon center instead of near it. Meaningful conclusions are as follows. The reasons for typhoon abrupt turning are that the subtropical high pressure was moving southward and divergence fields of 200 hPa were to the right of the typhoon center; there was no obvious cold air invading Shandong after the typhoon entered the westerly belt; the southeasterly jet of typhoon and shear brought heavy rainfall to the Shandong peninsula before the typhoon entered Shandong. But after the typhoon’s movement into Shandong, the typhoon’s inverted trough brought the rainfall to the northern and central Shandong.

Features and Sources of the Anomalous Moisture Transport for the Severe Summer Rainfall over the Upper Reaches of the Yangtze River

Using the daily NCEP/NCAR reanalysis dataset and the observation rainfalldata in China for the 1980-1997 period, features of severe summer rainfall over the upper reaches ofthe Yangtze River are investigated and then sources of moisture contributing to severe rainfallover eastern and western Sichuan Province (ES and WS for short) are examined with particularreference. It turns out that the severe rainfall occurring locally dominates summer rainfall overthe upper reaches of the Yangtze River. Climatological rainfall and anomalous one constitute severerainfall, but the latter accounts much for severe rainfall. The meridional moisture transportdominates the composite moisture transport on the occurrence day for ES region, while the zonal isequivalent to the meridional for WS region. Correlation between the moisture transport fluxes overthe two regions of severe rainfall and other regions, the anomaly and variation of the moisturetransport day by day during the period of severe rainfall lend a support for the conclusion that themeeting of the moisture from the West Pacific through the South China Sea (SCS) and the one fromnorthwestern China exerts a vital effect on the occurrence of severe rainfall, which can not beneglected.

Numerical Assessing Experiments on the Individual Component Impact of the Meteorological Observation Network on the "July 2000" Torrential Rain in Beijing

In an effort to assess the impact of the individual component of meteorological observations （ground-based CPS precipitable water vapor, automatic and conventional meteorological observations） on the torrential rain event in 4-5 July 2000 in Beijing （with the 24-h accumulated precipitation reaching 240 mm）, 24-h observation system experiments are conducted numerically by using the MM5/WRF 3DVAR system and the nonhydrostatic MM5 model. Results indicate that, because the non-conventional GPS observations are directly assimilated into the initial analyses by 3DVAR system, better initial fields and 24-h simulation for the severe precipitation event are achieved than those under the MM5/Litter_R objective analysis scheme. Further analysis also shows that the individual component of meteorological observation network plays their special positive role in the improvement of initial field analysis and forecasting skills. 3DVAR scheme with or without radiosonde and pilot observation has the most significant influence on numerical simulation, and automatic and conventional surface meteorological observations rank second. After acquiring the supplement information from the other meteorological observations, the ground-based GPS precipitable water vapor data can more obviously reflect initial field assimilation and precipitation forecast. By incorporating the groundbased CPS precipitable water vapor data into the 3DVAR analyses at the initial time, the threat scores （TS） with thresholds of 1, 5, 10, and 20 mm are increased by 1%-8% for 6- and 24-h accumulated precipitation observations, respectively. This work gives one helpful example that assesses the impact of individual component of the existing meteorological observation network on the high influence weather event using 3DVAR numerical system.