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青藏高原冬春积雪对我国夏季降水分布的影响研究 【作者】朱玉祥 【导师】丁一汇

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青藏高原冬春积雪对我国夏季降水分布的影响研究水利论文N+d `8?2e2c-p

lVagl0【作者】朱玉祥导师丁一汇水利论文W `&W!lH8Mh1D X!k`
【作者基本信息】南京信息工程大学,气象学,2007年,博士水利论文'Qc4O{ I.z,j

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i*_n5Z!g&L0【中文摘要】 本文主要通过诊断分析和数值模拟方法研究了青藏高原冬春积雪的变化及其对我国降水分布的影响,并对其影响机理进行了分析。文章还探讨了青藏高原冬春积雪增加的原因。另外,做了区域气候模式中的地形处理方案改进试验。主要结论概括如下:(1)发现青藏高原冬春积雪具有年代际的变化,尤其是春季积雪,在1977年出现了由少转多的突变;同时青藏高原及附近地区春夏季大气热源持续减弱。青藏高原冬春积雪和高原春夏季大气热源呈显著负相关,高原冬春积雪的增加对高原春夏季大气热源的减弱有重要贡献。(2)观测资料的统计相关发现,无论年际还是年代际,青藏高原冬春积雪与长江流域、新疆地区夏季降水呈正相关,而与华南和华北呈反相关。并且长江流域的正相关区具有高统计显著性。(3)把包络地形引入区域气候模式,对地面降水和温度的模拟有明显改善。(4)冬季多雪的敏感性试验较好的模拟出了“南涝北旱”雨型,即长江流域多雨,华北和华南少雨。(5)本文的数值模拟和资料分析都揭示出,在年代际尺度上东亚冬季风和夏季风具有明显的的反相关关系,而青藏高原冬春积雪在这种跨季度的相关关系中起了重要的“中介”作用。东亚冬季风偏强,青藏高原冬春积雪偏多;而青藏高...更多原冬春多雪会导致东亚夏季风和南亚夏季风偏弱。(6)揭示了高原冬春积雪影响夏季风和我国夏季降水的机理。在积雪初期,地面反射率起了主要作用;在积雪融化后,“湿土壤”在延长高原积雪对天气气候的影响过程中起了重要作用。初期的反射率增加减少了太阳辐射的吸收,融雪时的融化吸热,以及后期的湿土壤与大气的长期相互作用,改变了春夏季高原热源,是高原积雪影响夏季风并进而影响我国夏季降水的主要机理。(7)对“南涝北旱”做出了合理解释。资料分析和数值模拟都表明,青藏高原冬春多雪,会导致我国降水出现“南涝北旱”分布。“亚洲冬季风偏强-青藏高原冬春积雪偏多-春夏季高原热源偏弱-东亚夏季风偏弱”可合理解释1977年后的“南涝北旱”。(8)给出了青藏高原冬春积雪增加原因的解释:蒙古高压的加强,使得低层850hPa的冬季风加强,可以影响到青藏高原南侧的孟加拉湾地区,在低层激发出气旋环流;500hPa上,蒙古高压形成的反气旋环流南侧的东风可以吹到青藏高原上,和青藏高原南侧的气旋性环流在青藏高原南边缘形成切变线;青藏高原主体东部的大范围地区,垂直上升运动加强;春季流入青藏高原的水汽增加。上述因素导致了高原冬春降水(积雪)的增加。  还原水利论文5W lg!RWY w

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【英文摘要】 By using the methods of diagnostic analysis and numerical simulation, the influence of snow over the Tibetan Plateau (TP) in winter and spring on precipitation distribution in summer in China is studied and its possible mechanism is analyzed. The paper also discusses the possible reason of snow’s increasing over the TP in winter and spring.Main results are as follows:(1) Discovering that snow over the TP in winter and spring is increasing in decadal scales, especially snow in spring has an abrupt increase. The atmospheric heat sources over the TP and its neighboring areas take on a persistent downtrend in spring and summer during the past 50 years, especially in the last 20 years. Snow in winter and spring has notable negative correlation with the atmospheric heat source in spring and summer over the TP and its neighboring areas. The increase of the former has important contribution to the decrease of the latter.(2) Statistic correlations of observation data find that snow over the TP ...更多has remarkable positive correlation with precipitation in the middle and lower Yangtze River, and reversed correlation in South China and North China not only in inter-annual scales but also in inter-decadal scales .(3) The simulations of surface rainfall and temperature are distinctly improved after adopting envelope topography.(4) In the sensitive experiments of more snow over the TP than normal by using climate model, the simulated precipitation pattern is consistent with the observed, namely, more rainfall occurs in the middle and lower Yangtze River; Less rainfall presents in South China and North China. The results accord with the pattern of“southern flood and northern drought”.(5) Both the numerical simulation and data analysis in this paper show that East Asian winter and summer monsoons have marked reversed correlation in the inter-decade scale and snow over the TP in winter and spring plays an important role. Stronger East Asian winter monsoon can bring out more snow over the TP; and then more snow over the TP could lead to stronger East Asian winter monsoon and subsequently weaker East Asian and South Asian summer monsoons.(6) Discovering possible impacting mechanism of snow over the TP in winter and summer with monsoon and rainfall distribution in summer in China. In the early stage of snow, surface reflectivity is dominant; After snow is melted,“Moist Soil”contributes to the prolonged influence process of snow on weather and climate. The reduction of absorbed solar radiation due to the increased reflectivity, the increasement of absorbed heat as snow is melted, and the long-term interaction between moist soil and atmosphere change the heat source of the TP, which are the main impacting mechanism of snow over the TP in monsoon and rainfall distribution in China.(7) Presenting the reasonable explaining of“southern flood and northern drought”. Both data analysis and numerical simulation show that, much snow over the TP is one of reasons of“southern flood and northern drought”in East China.(8) Possible reasons of more snow over the TP in winter and spring are also investigated. The enhanced winter monsoon at 850hPa caused by the strengthen of Mongolia High, influences the Bay of Bengal (BOB), and triggers cyclonic circulation in the lower troposphere; At 500hPa, shear is formed between the eastern wind in south of anti- cyclone at Mongolia (i.e., Mongolia High) and the cyclonic circulation in south of TP; The vertical ascending is reinforced in the large extent area of east TP; The water vapor entering the TP increases in spring.  还原水利论文.m,N+`1w5u(j

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【中文关键词】 青藏高原积雪; 气候模拟; 季风; 南涝北旱; 包络地形
v!J5B6G&F0【英文关键词】 Snow over Tibetan Plateau; climatic simulation; monsoon; Southern flood and northern drought; envelope topography
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TAG: 导师 青藏高原 丁一汇 朱玉祥 积雪
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