A STUDY ON RESPONSE OF PRECIPITATION IN CHINA TO MONSOON INTRASEASONAL OSCILLATION

Temporal and spatial evolution characteristics of the 30-60 day oscillation (intraseasonal oscillation, ISO) of summer rainfall in China and the effects of East Asian monsoon on the rainfall ISO are analyzed in this paper. Results show that the annual and decadal variations of the oscillation exist between 1960 and 2008, and the intensity is weakest in the late 1970s and early 1980s. In the typical strong years of the rainfall ISO obtained from empirical orthogonal functions (EOF mode 1), an anticyclone is in northwestern Pacific and a cyclone is in the east of China. In the typical weak years, the wind ISO is much weaker. The low-frequency zonal wind and water vapor transport from the low latitudes to mid-latitudes in the typical strong years, and the oscillation strength of diabatic heating is much stronger than that in the weak years of the rainfall ISO. The anomaly characteristics of the rainfall ISO show anti-phases between the Yangtze River basin and south of China. As for the typical strong years of the rainfall ISO in the Yangtze River basin (EOF mode 2), the main oscillation center of water vapor is in the east of China (20-30°N, 110-130°E). In the peak (break) phase of the rainfall oscillation, a low-frequency cyclone (anticyclone) is in the Yangtze River basin and an anticyclone (cyclone) is near Taiwan Island. In addition, the peak rainfall corresponds to the heat source in the Yangtze River basin and the heat sink in the Qinghai-Tibet Plateau. As for the typical strong years of the rainfall ISO in the south of China, the main oscillation center of water vapor is south of 20°N. In the peak (break) phase of the rainfall ISO, a low-frequency cyclone (anticyclone) is in the south of China and an anticyclone (cyclone) is in the Philippines. The peak rainfall corresponds to the heat source in the south of China and the South China Sea, and the heat sink in the west of Indochina.     

地下水易污染性评价的集对分析方法研究

在地下水易污染性 DRASTIC 指标体系的基础上,应用集对分析方法评价了地下水的易污染性.将 DRASTIC 的 7 个指标分为5级,利用集对分析给出了分析背景下系统的联系度表达式,通过 5 个级别联系度的比较,确定了评价区地下水易污染性的等级和差别.结果表明,将集对分析方法和 DRASTIC 评价指标体系结合评价地下水易污染性,计算简便,评价正确合理,具有较好的区分性和较强的优越性.     

单双参云微物理方案对强降水过程中云宏微观特征模拟的对比分析

将WRF3.9模式的16种云微物理方案分为单参、双参两组,分别对2016年6月30日—7月4日江淮流域的一次强降水过程进行模拟。首先利用逐小时观测降水对各组模拟降水进行评估,在此基础上利用FY-2G和CALIPSO云产品数据分别评估不同方案对降水过程中总云量、云垂直结构云水含量等宏微观特征的模拟性能。结果表明:选用不同的云微物理参数化方案均能较好地模拟出该次过程的雨带位置和中心降水强度,但不同方案对云宏微观特征的模拟结果有显著差异。分析两组试验对总云量的模拟结果发现,单参方案组除Kessler暖云方案对冰云过程描述不足导致模拟的总云量显著偏高外,其他单参方案和所有双参方案均能模拟出强降水过程中总云量的时空演变特征。从云覆盖率和云水含量的垂直分布特征来看,单参方案组对600 h Pa以下中低层暖云的模拟稳定性整体略优于双参方案组;而对200～500 h Pa的冰相云模拟结果相反,双参方案组比单参试验组模拟的固水含量更加集中。将各层云覆盖率与CALIPSO云产品的对比也发现,对于低层暖云降水过程,选择如WSM3单参云微物理方案比双参方案得到的模拟云量更加接近实况,而对于以深对流为主要运动特征的冷云降水过程,选择如WDM5或WDM6这样双参云微物理方案模拟得出的高云量值更加稳定,误差也更小。     

热带气旋低层水平流场的平面动力系统分析

利用中国气象局上海台风研究所整理的热带气旋最佳路径资料,热带气旋云图、气象雷达回波图资料,ECMWF ERA-Interim再分析风场资料;并用大气运动方程和天气学原理分析得到热带气旋低层水平流场结构,根据流场建立平面非线性自治动力系统。结果表明,TC在成熟阶段或发展很强时期,由两组二维驻定微分方程组解确定水平流场,TC眼区以内气流沿顺时针方向流动,TC眼区以外气流沿逆时针方向流动。TC眼区内外相反方向风场之间为风向切变圆环,圆环上不断有气旋形成,并存在低空急流,是狂风暴雨出现区域。结论与合成雷达回波观测结果一致。