新疆不同降水观测资料的比较及其差异的可能原因

利用新疆地区89个气象站和38个水文站1961~2005年的降水资料,对比分析了这两类降水观测资料在表征新疆地区降水的时间演变特征上所存在的差异,进而探究了造成这种差异的原因,并在此基础上研究了增暖背景下新疆地区降水与地形(包括海拔高度、坡度和坡向)的关系。研究发现:1)从区域平均来看,水文站观测的年降水量(221.4 mm)明显高于气象站的观测值(152.1 mm),其差值为69.3 mm,但是二者具有相同的时空变化特征;2)气象站与水文站降水均值之间的差异,主要受海拔高度的影响,坡度和坡向的影响次之。新疆地区地形地貌复杂,降水时空变化较大,观测数据分布不均匀均可导致对降水的估算存在较大差异,因此多源降水数据相互融合是客观估算该地区降水量及其变化的一个途径。

Comparison of Different Precipitation Observations in Xinjiang and Its Possible Cause Analysis

A severe dust event during 19-22 March 2002 over East Asia was simulated by using the Weather Research and Forecasting/Chemistry (WRF/Chem) model coupled with two different dust emission schemes (the GOCART and Shao04 schemes) to investigate the impact of dust emission schemes on model performance. A comparison with observational data shows that the main observed dust emission regions, the temporal variation of dust emission intensity, and the evolution of surface dust concentration are all quite well reproduced. Both near the dust source and in its downstream regions, the model-simulated temporal variation in surface dust concentration agrees closely with station observations. Generally, the WRF/Chem model with the Shao04 scheme shows better performance, especially in simulating the occurrence and intensity of dust emission and the surface dust concentration distribution. Further analysis shows that the dust emission regions simulated by the GOCART scheme are broader than those from observational data, which might be ascribed to the lower criteria value of the threshold wind velocity at the surface. In addition, the GOCART scheme could not resolve the potential dust source in the southeast of Mongolia and the middle-east of Inner Mongolia, which leads to the underestimation of dust concentration in this area and in downwind regions. However, the simulated dust emission flux in Taklimakan with the Shao04 scheme is lower compared with observations. This could be ascribed to the fact that the effect of aerodynamic lift in the dust emission is not considered in the Shao04 scheme. Moreover, the inaccurate parent soil texture for the Taklimakan Desert used in the Shao04 scheme might be another possible reason for the discrepancy.