遗传算法同化GPS可降水量资料的研究与应用

利用上海气象台提供的GPS可降水量资料,对2006年7月4-5日发生在江淮地区的一次大暴雨过程进行了分析和模拟研究.此次降雨过程与对流层中低层中尺度低涡的发生发展有密切联系.在高低空环流的共同作用下,高空槽后干冷气流与西南暖湿气流在江淮地区频繁交汇,使得中尺度对流系统得以持续发展.由于造成此次降雨的对流系统尺度较小,仅用常规资料难以理想地模拟出降雨过程.因此,采用遗传算法(GA)同化系统研究了GPS可降水量资料在暴雨模拟中的作用,并做了与伴随同化系统的对比试验.数值模拟结果表明:(1)使用GPS可降水量资料调整初始场后能更准确地模拟出降水的落区与强度.(2)为了进一步检验使用遗传算法同化系统后的效果,通过湿度场,风场,高度场的均方差试验,证明加入GPS可降水资料的遗传同化试验对其它要素的改善与伴随同化GPS可降水资料的试验相比,更能模拟出与实况更为接近的低层风场,湿度场结构.

Study on genetic algorithm assimilation of GPS precipitable water data and its application

GPS precipitable water data provided by Shanghai Meteorological Observatory are used for analyzing and simulating the heavy rain happened in Jianghuai district on 4-5 July, 2006. It is found that the heavy rain event was closely related to generation and development of mesoscale vortex in the mid-low troposphere. The environmental condition between the southern edge of the westerlies and northern rim of the subtropical high of the western Pacific is favorable for the development of Mesoscale Convective Systems(MCSs)and the occurrence of heavy rain. MCSs develop continuously over there, while the low-level jet transports warm and moisture air to the south of MCSs. Therefore, the genetic algorithm with the assimilation of GPS precipitable water data are performed to simulate the heavy rain process，and to carry out comparision experiment of adjoint 4DVAR model. The result indicated that (1) the effect of numerical simulation with GPS precipitable water(GPS) data is better than that without GPS; (2) it is possible to prove that the experiment adding GPS can directly improve the other elements' forecasts obviously in comparison with that adoint 4DVAR model and can simulate the structure of lower wind field and humidity field that is closer to the real fact.