一次黄渤海海上大风过程模拟分析

2009 年2 月13 日黄渤海海域冷锋过境，出现海上大风天气过程。为分析此次大风过程的形成机理以及物理量场的分布特征，利用WRF数值模式对此次大风过程进行数值模拟。研究发现，WRF数值模式对这次冷锋型天气过程的高、中、低空天气系统的演变和强度模拟效果较好，成功揭示了黄渤海沿海地区大气环流形势及控制天气系统演变的主要特征：此次大风过程主要是冷锋过境引起的大风降温过程，冷空气开始入侵，地面气压梯度力增强，风速开始增大，同时明显反映出冷暖气团的斜压性，锋面的斜压性增强地面风速。物理量场的模拟说明，当测站上空由上升运动转为下沉运动时，风速逐渐增大，风速的大小与下沉运动的强度呈正比。温度和相对湿度场的分布反映了锋面过境的系统演变。

Numerical Simulation of Offshore Gales over the Bohai and the Yellow Sea

Offshore gale over the Bohai and the Yellow Sea was caused by frontal passage on Feb. 13, 2009. WRF Model was employed to simulate the gale to investigate the mechanism and distributional characteristics of physical factors. Evolution and intensity of weather systems in upper-level, middle-level and lower-level for this frontal gale were well simulated by the model, which successfully reproduced the main traits of circulations and controlling synoptic system over the Bohai and the Yellow Sea. The gale was mainly caused by cold front of wind cooling process, with invading cold air and growing surface pressure gradient force, during which wind speed increased as well. This was a reflection of the warm and cold air baroclinicity and wind speed enhanced by the surface baroclinicity. Simulation of physical factors indicated that surface wind speed could increase when upward motion turns to downward motion over observation station and the speed was proportional to the intensity of downward motion. Temperature and relative humidity distribution was a reflection of weather systems development when cold front passed by.