兰州大学机构库 >大气科学学院
河西走廊地区雷暴特征及预报指标研究
Alternative Titletudy on characteristics of thunderstorm and its forecasting in Hexi Corridor
朱昌权
Thesis Advisor尚可政
2018-05-02
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name硕士
Keyword雷暴 环流分型 物理量诊断 河西走廊 军事气象保障
Abstract

河西走廊地区在军事地理上具有重要的地位,是如今国家提出“一带一路”重大战略构想的重要节点。从军事气象保障的工作实际来看,雷暴等强对流天气对于河西走廊地区的空军航空兵军事行动有重要影响。因此,从军事气象保障的业务需求出发,本文利用地面常规气象观测资料、军队观测资料、NCEP/NCAR和ECMWF再分析资料等,首先针对甘肃省全省1981-2013年雷暴的气候特征进行了分析;利用军队地面观测资料,对河西走廊三个军用机场(酒泉、张掖和武威)1981-2013年雷暴气候特征进行了系统分析;同时对地方台站和军用机场的雷暴气候特征进行了对比分析。进一步地,对甘肃省全省雷暴年际变化和“东西反向”型主导的大气环流特征进行了研究,同时,对河西走廊大范围雷暴进行了环流分型。最后,对1981-2013年河西走廊地区非雷暴降水和雷暴降水主要的物理量特征进行了诊断分析。主要结论如下:(1)、甘肃省1981-2013年雷暴气候特征显示,年平均雷暴日数从东南至西北递减,年均雷暴日数整体呈现显著下降趋势;年内变化则呈现7月最多, 6月和8月次之的特征。对甘肃省年均雷暴日做EOF分析,第一典型场为“全区一致型”,占69.5%,第二典型场为“东西反向型”,占11.6%。雷暴初、终日的空间分布特征与年均雷暴日数的分布特征一致,甘南高原的初雷暴日出现最早,终雷暴日最迟;而河西走廊西北部地区初雷暴日出现最晚,终雷暴日最早。周期分析显示雷暴年际变化主要周期存在于1985-1990年间,为3a左右;而年内周期主要体现为3d和4-7d的“单周震荡”。(2)、对比分析1981-2013年地方和军队观测站点的雷暴气候特征发现,两类资料统计得到的雷暴日数,无论是在年代际、年际还是年内气候变化上,均存在较大差异,尤其是在河西走廊西部的酒泉地区,但雷暴日线性减少趋势在两类资料上都能体现。年内分布上,酒泉地区地方观测站点的雷暴日数在各个月份均多于军队观测站点,尤其在雷暴发生最多的7月份,地方观测结果是军队观测的2倍多;张掖地区,在雷暴发生较多的6-7月份地方观测结果较军队多,尤其是在6月份,地方观测是军队的1.6倍;武威地区各个月份差异均较小,地方观测与军队观测的差异少于20%。(3)、利用河西走廊三个军用机场代表站的雷暴观测资料,统计发现:河西走廊地区的雷暴在1990年代前较多,之后较少。年际变化特征上,河西走廊地区年雷暴日数随时间呈明显的线性减少趋势。年内变化上,雷暴出现在3-10月,夏季(6-8月)雷暴发生率最高,占年雷暴总数的81.0%,其中7月最多,占全年总数的29.6%。周期分析显示,三个机场仅酒泉在1995-2005年间有3a左右周期;年内周期均在6-8月存在3d和4-7d的单周震荡周期。日变化特征显示:13-24时为雷暴多发时段,约占全天发生频率的90.0%,其中又以17-19时发生频率最高,占31.5%。河西走廊地区74%以上的雷暴持续时间为1-2小时。平均初雷日出现在5月中下旬,终雷日在8月底至9月初。河西走廊雷暴的发生往往伴随着其他天气现象,包括阵雨、大风、扬沙、沙暴和冰雹等,最多伴随的天气现象为阵雨,概率超过55%,其次是大风和扬沙。(4)、甘肃省年均雷暴日数具有年际变化特征的环流成因主要为,在雷暴日高值年,中高纬度经向环流、西风带以及东亚夏季风较气候平均态均偏强,且甘肃大部分地区水汽辐合加强,使得冷暖空气在甘肃地区交绥,有利于雷暴的发生;而在低值年形势则相反。甘肃省年均雷暴日数呈“东西反相”空间分布特征的环流成因与影响西北地区降水的环流成因相似,即影响甘肃西部的大气环流系统与东部不同,因此具有相异的水汽输送条件,且由于受到夏季风的影响,西北地区西部的水汽通量散度与东部地区变化相反。此外,青藏高原对西北地区动力、热力作用的影响也是重要原因。(5)、遴选了14次河西走廊地区大范围雷暴天气过程,对其进行环流分型,可以将河西走廊地区大范围雷暴环流形势分为:高空冷槽型、蒙古冷涡型、高空槽后西北气流型和横切变线型等4种类型。通过环流特征总结和个例分析发现,河西走廊地区发生大范围雷暴必须满足大气层结不稳定、较好的中低空水汽条件、较明显的冷空气入侵和适当的触发机制等条件。(6)、利用探空资料对河西走廊地区雷暴发生时的物理量特征进行诊断显示,沙氏指数SI和。均能够较好表现雷暴过程相较于非雷暴降水对流不稳定较强的特征,大范围雷暴发生时武威地区的SI阈值为3.32K~-5.73K,阈值为4.21K~-7.28K;酒泉地区SI阈值为0.45K~-11.36K,阈值为0.57K~-14.04K。雷暴过程期间相对湿度较非雷暴降水要小,尤其在7月份,有明显的上干下湿的水汽分布特征。雷暴过程期间风场表现为在雷暴发生前中高层西北气流加强、低层西风显著减弱甚至转为东风的明显垂直风切变特征。

Other Abstract

As an important node under background of the country put forward the "great strategic concept The Belt and Road", the Hexi Corridor has an important position in the military geography. From aspect of the actual demand of military meteorological support, strong convective weather, such as thunderstorm, has an important impact on military activities such as aeronautical flight in the Hexi Corridor Region. Aim at practical demand for military meteorological support in Hexi Corridor Area, by combining station meteorological observation data, military observation data, and the NCEP/NCAR and ECMWF reanalysis data, this paper firstly analyzes climatological characteristics of thunderstorm in Gansu province in recent 33 years. Then the difference of thunderstorm characteristics by local station observation data and the military observation data is investigated in three military airfields (Jiuquan, Zhangye, and Wuwei) in Hexi Corridor Region. Further, climatological characteristics of thunderstorm in these three military airfields is disclosed to represent the total situation in Hexi Corridor Region. In addition, the feature of the circulation which influencing the main modes of thunderstorm days in Gansu is concluded. And atmospheric circulation is classified for large-scale thunderstorm in Hexi Corridor Region. At last, physical elements are diagnosed during thunderstorm and rainfall without thunderstorm during 1981-2013.

The main results are as follows:(1) Spatial distribution of average annual thunderstorm days present significant trend from south to north while thunderstorm days is more in the south than in the north. The area with the most and least annual thunderstorm days is in Gannan Plateau with more than forty days and Hexi Corridor with less than eight days, respectively. The thunderstorms happen in summer mostly, accounting for more than 50% of the total, and happen in the spring and autumn season the second mostly. The average annual thunderstorm days have an obviously decreasing linear trend during the recent 33 years, with the linear trend coefficient of -0.32. The results of EOF analysis show that, the first eigenvector accounts for 69.5% with decreasing tread in the all area pattern, and the area with the most obvious decreasing tread of thunderstorm days is in Gannan Plateau. The second eigenvector accounts for 11.6% with high (or low) in east and low (or high) in the west pattern, but the corresponding annual variation tendency is not obvious. The thunderstorm period decreases from south to north of Gansu province, with the longest in Gannan Plateau and the shortest in Hexi Corridor. Wavelet Analysis shows that interannual variation oscillation periods mainly exists between 1985 and 1990, with period of nearly 3a, and seasonal period of thunderstorm days is characterized as “single week oscillation”(3d and 4-7d) from June to September. (2) By comparing climatological characteristics of thunderstorm by local station observation data and the military observation data is investigated in three military airfields (Jiuquan, Zhangye, and Wuwei), it is found that no matter for decal, interannual, or inter-seasonal variation, difference is very obvious, especially in Jiuquan. However, distinct decreased linear tendency of thunderstorm days in recent 33 years can be both found by these two data. For the seasonal variation, thunderstorm days by local station observation data are all more than that by the military observation data in Jiuquan during all months, especially the former is double times of the latter in July when the thunderstorm happen the most frequently. In Zhangye, thunderstorm days by local station observation data are 1.6 times of that by the military observation data in June. The difference is comparably small in Wuwei, which is less than 20% during all months.(3) By analyzing the three-represented military airfield in Hexi Corridor region in recent 33 years, it is found thunderstorm days in Hexi Corridor region is characterized as more in decades before 1990s but less after 1990s in decals variation, as obvious decreased tendency in annual variation, and in seasonal variation as more in March-October, especially in June (29.6%) in summer (81%). Wavelet Analysis shows that only in Jiuquan interannual variation oscillation periods mainly exists during 1995-2005 with period of nearly 3a, and seasonal period of thunderstorm days is characterized as “single week oscillation”(3d and 4-7d) from June to August. During a day, 90% of the total thunderstorm happen during 13:00-24:00, and the most accounting for 31.5% happens during 17:00-19:00. The duration of more than 74% thunderstorms is 1-2 hours. The first thunder day is basically before 21st May, but the last thunder day is different in these three airfields. The occurrence of thunderstorms in the Hexi Corridor is often accompanied by weather phenomena, including rain, wind, blowing sand, sandstorm, and hail, among them the most one is rain which accounting for more than 55% of the total.(4) To research the feature of the circulation which influencing the thunderstorm days in Gansu, it is found that the meridional circulation on mid-high latitude, westerly belt and East Asian monsoon are all stronger than normal, and the convergence of the water vapor transport is also stronger in the high thunderstorm days years. But it is the reverse in the low thunderstorm days years. Besides, the circulation cause that leads to the opposite phase of average annual thunderstorm days between east and west areas in Gansu is that the western Gansu is mainly influenced by the westerly belt, but the southeast of Gansu is mainly influenced by the East Asian monsoon. So the water vapor transport over the western Gansu is very different from that over the southeast of Gansu. Moreover, the effects of dynamic and thermodynamic of Qinghai-Tibet Plateau on Northwest China also lead to the opposite phase between east and west areas in Gansu. (5) 14 large-scale thunderstorm weather process in Hexi Corridor region is selected for the corresponding atmospheric circulation classification, i.e., cold trough in upper-level, Mongolia cold vortex, the northwest flow after upper-level trough, and transverse shear line. Occurrence of thunderstorms in the Hexi corridor area must meet the requirements including unstable gas reservoir, the middle-low-level water vapor conditions, the obvious cold air invasion, and the appropriate triggering mechanism.(6) By using sounding data and reanalysis data of wind filed, physical elements during thunderstorm are diagnosed. The results show that index of SI and. can represent obvious character of stronger convective instability during thunderstorm than that during rainfall without thunderstorm, with the threshold of SI and are 3.32K~-5.73K and 4.21K~ -7.28K in Wuwei and 0.45K~-11.36K and 0.57K~-14.04K in Jiuquan, respectively. Relative humidity is smaller during thunderstorm than that during rainfall without thunderstorm, showing water vapor is characterized as “dry in upper-level and wet in lower-level” during thunderstorm in July. During thunderstorm, there is obvious wind shear in middle-lower level troposphere, i.e. little change in the middle troposphere wind field and low-level westerly wind weakened or even turned to the east wind in the afternoon. 

URL查看原文
Language中文
Document Type学位论文
Identifierhttp://ir.lzu.edu.cn/handle/262010/200243
Collection大气科学学院
Recommended Citation
GB/T 7714
朱昌权. 河西走廊地区雷暴特征及预报指标研究[D]. 兰州. 兰州大学,2018.
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