三原县近43年来气候变化特征分析

利用1972—2014年三原县气象站地面气象观测站逐日气温、降水量、平均风速、日照时数等资料,采用5年滑动平均、一元线性回归等方法,分析三原县近43年的气候变化特征。结果表明：近43年来三原县温度变化特征为明显的上升趋势,气候倾向率为0296 ℃/10 a;年降水量、日照时数,平均风速、干燥指数均呈减少趋势,气候倾向率分别为-3959 mm/10 a、-30872 h/10 a、-0048 （m/s）/10 a和-0448（10 a）-1。20世纪80年代气温较低,主要由夏季降温所致;21世纪气候变暖,四季均有贡献,以春季贡献最大。80年代降水偏多,春季贡献最大;90年代降水的减少,主要由秋季降水减少造成。春季风速变化对年平均风速变化影响较大。80年代日照时数减少,夏季贡献最大;90年代日照时数减少,春季贡献最大;21世纪日照时数增加,春季贡献最大。80年代末以前为冷湿期,80年代末到2000年为相对暖干期,2000年以后向暖湿发展。

     

2000—2009年夏季东亚热带气旋远距离暴雨统计分析及个例的数值模拟

利用2000—2009年6—8月的NCEP 1 °×1 °FNL数据、TRMM降水数据及JMA提供的《TC最佳路径集》等资料,综合考虑低层水汽通道及TC与中纬度系统相互作用的两个因素,对0 °以北150 °E以西东亚地区的远距离暴雨进行统计分析,得出这一时期共有48例远距离暴雨产生,并将其分为5种类型。将各类型合成分析后得到远距离暴雨在850 hPa、500 hPa的主要影响系统有:TC、中纬度槽、副热带高压及水汽通道,其中水汽通道多与印度季风相连接对远距离降水的影响最显著,其次是中纬度槽。形成最多的是北槽、涡-南TC型远距离暴雨占总数的68.8%,而且远距离暴雨多发生在TC路径的右侧（占总数的71%）。200 hPa上多数远距离暴雨发生在高空急流的右后方,并在TC的东西部各有一反气旋性涡旋。当TC东部无反气旋性涡旋时TC较弱。当远距离暴雨发生在TC的西北方向,且西北方向有槽存在时TC较强。利用WRF中尺度数值模式对1104号TC Haima进行敏感性试验表明,TC在此次暴雨过程中起主要作用,通过影响降水区的水汽通道导致降水增强。      

STATISTICAL ANALYSIS OF SUMMER TROPICAL CYCLONE REMOTE PRECIPITATION EVENTS IN EAST ASIA FROM 2000 TO 2009 AND NUMERICAL SIMULATION

Using 1°×1° final analysis(FNL) data from the National Centers for Environmental Prediction(NCEP),precipitation data from the Tropical Rainfall Measuring Mission(TRMM) and the best-track tropical cyclone(TC)dataset provided by the Japan Meteorological Agency(JMA) for June-August of 2000-2009, we comprehensively consider the two factors low-level moisture channel and interaction between TCs and mid-latitude systems and implement a statistical analysis of remote precipitation in East Asia to the north of 0° and to the west of 150° E. 48 cases of remote precipitation occurred in this period, which are categorized into five classes. After a composite analysis of the different classes, the main systems at 850 h Pa and 500 h Pa that impact the remote precipitation are as follows:TC, mid-latitude trough, subtropical high and water vapor channel. In particular, the water vapor channel which usually connects with Indian monsoon has the most significant impact on remote heavy rainfall. Another important factor is the mid-latitude trough. The type of north trough/vortex-south TC remote precipitation events happen most frequently,accounting for 68.8% of the total incidence. Most remote precipitation events occur on the right side of the TC path(representing 71% of the total number). At 200 h Pa, the remote precipitation events usually occur on the right rear portion of a high-altitude jet stream, and there is an anti-cyclonic vortex to the east and west of the TCs. When there is no anti-cyclonic vortex to the east of the TC, the TC is relatively weak. When the remote precipitation occurs to the northwest of the TC and there is a trough in the northwest direction, the TC is relatively strong. Numerical experiments are carried out using Weather Research and Forecast(WRF) model. The results shows that the TC plays a main role in producing the heavy precipitation and results in the enhancement of precipitation by impacting the water vapor channel.