摘要
采用中国西北地区19602009年68月常规气象观测站24 h(20:0020:00)降水资料和NCEP/NCAR(2.5×2.5)19602009年再分析逐日4次的850,700,600,500 hPa位势高度、比湿q和U,V风场资料.在分析西北地区降水概况的基础上,通过NOAA HYSPLIT_4水汽轨迹模型和常规诊断分析方法,对2005年7月12日降水过程进行了分析,结果表明:中国西北地区暴雨的主要特点是降水频率低,降水频数有明显的年际变化特征;降水时间相对集中,主要集中在7月和8月;降水持续时间短,且降水时间持续2天(包括2天)以上的过程性降水次数有明显的年代分布特征.西北地区降水的环流形势主要以西低东高型和偏南气流型为主.利用HYSPLIT后向轨迹模型,对2005年7月12日降水过程向前360 h追踪水汽输送轨迹,发现水汽主要来自偏南气流;但是,不同等压面上水汽轨迹并不总是一致的,降水量越大,不同等压面上的水汽输送轨迹越趋于一致.通过物理量的诊断分析,表示水汽来源的水汽通量分布与后向轨迹模型给出的水汽来源一致.因此在本个例中,后向轨迹模型可以作为判断降水过程中水汽来源的方法之一,并且此次降水过程伴随强烈的上升运动和对流层中下层的强辐合及高层的辐散气流.
The landform of Northwest China is diversified, the underlying surface is complex and heavy rain precipitation accounts for a high proportion. Thus, heavy rain plays an important role in a study of the precipitation and drought in Northwest China. The observational precipitation data from June to August in 1960-2009, and the NCEP/NCAR （2.5°×2.5°） daily reanalysis data from 1960-2009 were used to analyze the heavy rain in Northwest China. On that basis, the precipitation process （2005.7.1-2） were analyzed using the HYSPLIT-4 model and diagnostic analysis methods. The results showed that heavy rains in this part of China were of less precipitation frequency. Precipitation frequency had obvious characteristics of decadal variety, with precipitation centred entirely on July and August. The duration of precipitation process was generally short, and the duration heavy rains reaching more than 2 days （including 2 days） showed obvious characteristics of decadal distribution. The circulation situation of precipitation in Northwest China was dominated by ow-lying west high east and southerly air. The water vapor was mainly from the south warm air, and the vapor tracks in different isobaric surfaces did not always coincide. The vapor tracks in different isobaric surfaces reached converged similarly when the precipitation was high. The source of vapor given by the distribution of vapor flux was in conformity with the pattern of backtracking. Therefore, the HYSPLIT-4 Model could be used as a new method to measure the source of vapor during precipitation process. The heavy rainfall process comes with strong upward motion, strong convergence of lower troposphere and divergent airflow of higher troposphere.
出处
《兰州大学学报（自然科学版）》
CAS
CSCD
北大核心
2013年第4期474-482,共9页
Journal of Lanzhou University(Natural Sciences)
基金
兰州大学中央高校基本科研业务费专项资金项目(LZUJBKY-2013-110)
国家科技支撑计划项目(2009BAC53B02)
