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西北地区干湿演变及其成因分析 【作者】王鹏祥 【导师】郑有飞; 何金海

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西北地区干湿演变及其成因分析

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【作者】王鹏祥导师】郑有飞; 何金海
:Y9lwO.a0Z;i6^T{0【作者基本信息】南京信息工程大学,大气物理学与大气环境,2008年,博士水利论文/cg"B.R*XrnV,`q

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s1M {|)_ZT0【中文摘要】 本文使用中国西北地区(陕、甘、宁、青、新及内蒙西部)1960~2003年逐月平均气温、降水量、水面蒸发量等站点资料及NECP/NCAR月平均再分析高度场、风场、地面气压、比湿等资料,通过降水和蒸发这两个水分平衡最关键的分量构造了均一化干湿指数,进而研究了西北地区干湿气候转型的特征及其可能的影响机制。主要得到以下结论:(1)西北地区年降水量在西风带气候区以及高原区近44a来表现为增加趋势,而季风带气候区表现为减少趋势。西北地区的蒸发量表现出了显著的减少趋势,而蒸发量的减少因子可能主要是由日照时数、平均风速、平均最低气温、平均日较差的变化引起的。(2)通过降水—蒸发均一化干湿指数对西北地区干湿特征的研究表明,西风区、高原区干湿特征呈较为显著的变湿趋势,而西北地区东南部位于季风影响边缘的区域干湿特征呈变干趋势。当北极涛动正位相越强时,东亚夏季风一般偏弱,西北地区东南部降水减少,气候转干,西风区和高原区降水增加,气候由干向湿变化,反之亦然。(3)印度洋前期春季海温异常对预测夏季中国西北干湿特征的变化特征具有明确的指示意义,赤道印度洋是影响西北北部夏季干湿特征的关键区。在印度洋春季海温异常冷年,...更多从印度洋到我国西北地区没有异常的西南暖湿气流输送,使得我国西北地区由于没有充足的水汽输送而偏干;而在异常暖年,从孟加拉湾到我国西北地区存在明显的水汽输送带,使得我国西北地区偏湿。另外在印度洋春季海温异常冷年,从春季到后期夏季南亚高压偏弱,而且后期夏季南压高压成单峰型;在异常暖年,正好相反,从春季到后期夏季南亚高压偏强,而且后期夏季南压高压成双峰型。这可能是印度洋海温影响西北地区夏季干湿特征的可能机制。(4)前期冬季太平洋海温同中国西北地区夏季干湿指数存在着显著的相关关系。其中赤道中东太平洋是影响西北地区东部干湿特征的关键区。在冬季赤道中东太平洋异常暖年,同期冬季和后期春季赤道中东太平洋地区表现为异常上升气流,使得中东太平洋地区表现为异常强的哈得莱环流,强迫500hpa高度场表现为PNA遥相关型,而后期夏季表现为WP遥相关型,这样从冬季到后期夏季西太平洋高压强度增强,面积增大,西伸边界越西,而后期夏季我国西北地区东部容易受副热带高压边坡暖湿气流的影响,所以偏湿;而异常冷年正好相反,这可能是冬季赤道中东太平洋海温影响中国西北地区东部夏季干湿特征的重要机制。  还原水利论文0y}1Mp5F

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【英文摘要】 Applying the data of monthly temperature, precipitation, water surface evaporation in Northwest China(Shanxi, Gansu, Ningxia, Qinghai, Xinjiang and west Inner Mongolia) in 1960~2003 and NCEP/NCAR monthly mean reanalyzing height fields, wind fields, surface pressure fields, humidty fields, aridity-wetness index is defined by precipitation and water surface evaporation, then characteristics which the climate has transited from arid to wet in Northwest China and possible influence mechanism were studied. The main conclusions as follows:(1) In recent 44 years the annualy precipitation has increased in westerly zone climate region and plateau climate region of Northwest China, but it has decreased in monsoon climate region. Water surface evaporation showed marked decreased trend, and this was caused by sunlight, average wind speed, average minimum temperature, average daily change range.(2) Characterstic of aridity and wetness were studied by aridity-wetness index of precipitation and water...更多 surface evaporation, it was found that climate showed prominent change from arid to wet in westerly zone climate region and plateau climate region, but climate displayed change from wet to arid in monsoon zone climate region. In addition, when Arctic Oscillation positive(negative) phase is stronger, the East summer Monsoon is generally weaker(stronger), the precipitation of southeast of Northwest China is decreases(increases), and the climate change from wetness(aridity) to aridity(wetness), the precipitation is increases(decreases) in westerly zone climate region and plateau climate region, and the climate change from aridity(wetness) to wetness(aridity).(3) There were clear indication sense that spring SSTA of the Indian Ocean forecast to anaphase summer characterstic of aridity and wetness of north of Northwest China, and key region locate on equator Indian Ocean. If spring SST occurred cold in the Indian Ocean, there was a lack of anomaly warm and wet airflow from the Indian Ocean to Northwest China, climate prone to dry because of lack of water vapor transportation in Northwest China. If spring SST occurred warm in the Indian Ocean, there was clear water vapor transportation zone from Bengal bay to Northwest China, climate prone to wet because of lack of water vapor transportation in Northwest China. In addition, if spring SST occurred cold in the Indian Ocean, South Asia High Pressure tend to weak from spring to summer, and that South Asia High Pressure showed single apices type in anaphase summer. If spring SST occurred warm in the Indian Ocean, South Asia High Pressure prone to strong from spring to summer, and that South Asia High Pressure showed twin apices type in anaphase summer. This is likelihood mechanism of the Indian Ocean SST influence on summer aridity and wetness in Northwest China.(4) There were remarkable relation between prophase winter SSTA of the Pacfic and anaphase summer characterstic of aridity and wetness of east of Northwest China, and key region locate on equator middle-east Pacific Ocean. In anomaly warm winter years of equator middle-east Pacific ocean, the area shows anomaly updraft at corresponding phase and anaphase spring, this cause anomaly strong Hadley cell in middle-east pacific, and compel 500hpa height field to show PNA teleconnection, it displays WP teleconnection at anaphase summer, thus intensity of West Pacific Ocean Subtropical High Pressure boost up, its area augment and west boundary prone to west from winter to summer, North China is effected by warm and wet airflow of Pacific Ocean Subtropical High Pressure border slope, and climate tend to wet. Vice versa. This is likelihood mechanism of equator middle-east Pacific Ocean SST influence on summer drought and wetness in Northwest China.  还原水利论文3SH;v*DG

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【中文关键词】 西北地区; 干湿演变; 影响机制
wN;HD }z#Aud0【英文关键词】 Northwest China; Aridity-Wetness Evolution; Influence Mechanism水利论文"k/^8X%t'H/r5GV(}

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