本文選題：低緯高原 + 夏季降水��； 參考：《云南大學(xué)》2016年博士論文

【摘要】：中國低緯高原位于中國西南部,南部瀕臨孟加拉灣和中國南海兩大熱帶海洋,西北部是青藏高原,同時(shí)受到印度季風(fēng)和東亞季風(fēng)的影響,區(qū)內(nèi)夏季降水的時(shí)空變化規(guī)律十分復(fù)雜,與中國其它地區(qū)存在明顯區(qū)別。近年來低緯高原地區(qū)旱澇災(zāi)害頻繁發(fā)生,給該區(qū)人民的生命財(cái)產(chǎn)造成了嚴(yán)重的影響,加強(qiáng)低緯高原地區(qū)夏季降水影響因子的研究,提高降水在短期氣候尺度上的預(yù)測(cè)能力,對(duì)于防災(zāi)減災(zāi)具有十分重要的現(xiàn)實(shí)意義。本文基于低緯高原的降水資料、MERRA再分析資料、Hadley中心海溫資料和NOAA的二十世紀(jì)再分析資料等,綜合應(yīng)用合成分析、經(jīng)驗(yàn)正交函數(shù)分解、奇異值分解、線性回歸分析方法和數(shù)值模擬方法,系統(tǒng)地研究了類副熱帶印度洋偶極子影響低緯高原夏季降水的物理機(jī)制。主要結(jié)論如下：(1)夏季為低緯高原降水的主汛期,月降水量在150mm以上。低緯高原區(qū)氣候平均夏季降水量呈西南部和東南部降水量較多,中部及西北部降水較少的分布特征。低緯高原夏季降水演變的首要模態(tài)為全區(qū)一致變化型,且全區(qū)一致型的降水有微弱的減少趨勢(shì)；次要模態(tài)為東西反向變化型,該模態(tài)在1985-2005年間存在2-5年的顯著振蕩周期。全區(qū)一致模態(tài)的合成分析表明,低緯高原附近西南風(fēng)異常是影響低緯高原夏季降水異常的重要因素,當(dāng)?shù)途暩咴髂蟼?cè)出現(xiàn)異常西南風(fēng)(東南風(fēng)),暗示著低緯高原附近氣候平均的西南風(fēng)加強(qiáng)(減弱),加強(qiáng)的西南風(fēng)將攜帶更多(更少)的水汽進(jìn)入低緯高原,造成低緯高原降水異常偏多(偏少)。(2)通過對(duì)925hPa水平風(fēng)場和海表溫度聯(lián)合場與低緯高原夏季降水的SVD分析發(fā)現(xiàn),類副熱帶印度洋偶極子型海溫異常與低緯高原夏季降水存在顯著的關(guān)系,當(dāng)副熱帶西南印度洋海表溫度偏低(高),東南印度洋海表溫度偏高(低)時(shí),對(duì)應(yīng)低緯高原夏季降水偏多(少)。進(jìn)一步對(duì)海表溫度與低緯高原區(qū)域平均夏季降水進(jìn)行相關(guān)分析發(fā)現(xiàn),在本研究中類副熱帶印度洋偶極子是影響低緯高原夏季降水的主要外部熱力強(qiáng)迫因子之一,其影響強(qiáng)于其它類型的海氣相互作用(如：ENSO)對(duì)低緯高原夏季降水的影響。(3)基于SVD分析第一模態(tài)SST和925hPa風(fēng)場的時(shí)間系數(shù),定義類副熱帶印度洋偶極子正、負(fù)異常年,通過合成分析揭示類副熱帶印度洋偶極子通過影響孟加拉灣北部的緯向風(fēng)異常進(jìn)而影響低緯高原夏季降水。當(dāng)類副熱帶印度洋偶極子為正(負(fù))異常年時(shí),即西南印度洋海溫偏高(低),東南印度洋海溫偏低(高)時(shí),會(huì)導(dǎo)致①印度半島會(huì)產(chǎn)生氣旋(反氣旋)環(huán)流,其北部為東風(fēng)(西風(fēng))異常；②熱帶印度洋低層氣流輻散(輻合),阿拉伯海至印度半島西北部低層氣流輻合(輻散),孟加拉灣東海岸的散度風(fēng)場中為東風(fēng)(西風(fēng))異常；③熱帶印度洋的輻散風(fēng)會(huì)導(dǎo)致在半球間形成異常的輻散環(huán)流：大氣在熱帶印度洋上升(下沉),而在孟加拉灣下沉(上升)。以上三個(gè)因素均會(huì)導(dǎo)致孟加拉灣北部的東風(fēng)(西風(fēng))異常,使得氣候平均場中西南風(fēng)減弱(增強(qiáng)),由西南風(fēng)攜帶進(jìn)入低緯高原區(qū)的水汽減少(增多),低緯高原區(qū)水汽輻散(輻合),從而使得低緯高原夏季降水減少(增加)。除此之外,印度半島夏季降水異常對(duì)低緯高原夏季降水也具有一定程度的影響,印度半島降水異常偏多(少),會(huì)加強(qiáng)孟加拉灣的氣旋(反氣旋)異常,使得孟加拉灣北部東風(fēng)(西風(fēng))異常,進(jìn)而影響低緯高原夏季降水偏少(多)。(4)類副熱帶印度洋偶極子的形成可追溯到前期冬季,并維持到夏季,特別是類副熱帶印度洋偶極子正異常年份。蒸發(fā)-風(fēng)-海表溫度(WES)反饋機(jī)制能夠解釋類副熱帶印度洋偶極子的維持機(jī)制,海洋的平流作用對(duì)類副熱帶印度洋偶極子的維持也有一定貢獻(xiàn)。(5)大氣環(huán)流模式的數(shù)值模擬結(jié)果表明：副熱帶西南印度洋相對(duì)暖(冷),而東南印度洋相對(duì)冷(暖)的海溫異常分布型,確能強(qiáng)迫出低緯高原夏季降水偏少(多)。數(shù)值模式結(jié)果與第四章的診斷分析結(jié)論一致,比較好地驗(yàn)證低緯高原夏季降水對(duì)類副熱帶印度洋偶極子型海溫異常的響應(yīng)。海氣耦合模式進(jìn)一步證實(shí)了類副熱帶印度洋偶極子影響低緯高原夏季降水異常的物理機(jī)制,以及類副熱帶印度洋偶極子從前期冬季至夏季的維持機(jī)制。
[Abstract]:The low latitude plateau of China is located in the southwest of China. The south is on the two major tropical oceans in the bay of Bengal and the South China Sea. The northwest is the Qinghai Tibet Plateau. It is influenced by the India monsoon and the East Asian monsoon. The temporal and spatial variation of summer precipitation in the region is very complicated and distinct from other regions in China. In recent years, the drought and flood in the low latitude plateau area have been droughts and waterlogging. Frequent disasters have caused serious impact on the life and property of the people in the area. It is of great practical significance to strengthen the study on the influence factors of summer precipitation in the low latitude plateau area and improve the prediction ability of precipitation on the short-term climate scale. This paper is based on the precipitation data of low latitude plateau, MERRA reanalysis data, Ha Dley central sea temperature data and the reanalysis data of NOAA in twentieth Century, comprehensive application of synthetic analysis, empirical orthogonal function decomposition, singular value decomposition, linear regression analysis and numerical simulation, systematically studied the physical mechanism of the influence of the subtropical India Ocean Dipole on the low latitude Gao Yuanxia seasonal precipitation. The main conclusions are as follows: (1) summer In the main flood season of low latitude plateau precipitation, the monthly precipitation is above 150mm. The average summer precipitation in the low latitude plateau region is more precipitation in the southwest and Southeast, and the precipitation is less in the middle and northwestern regions. The first mode of the Summer Precipitation Evolution in the low latitude plateau is the uniform variation in the whole region, and the uniform precipitation in the whole region is weak. The trend is reduced; the secondary mode is the East-West reverse change type. The mode has a significant oscillation period of 2-5 years in 1985-2005 years. The analysis of the uniform mode in the whole region shows that the southwest wind anomaly near the low latitude plateau is an important factor affecting the summer precipitation anomaly in the low latitude plateau, and the southwest wind (east wind) appears in the southwest side of the low latitude plateau. It is suggested that the average southwest wind near the low latitude plateau is strengthened (weakened), and the strengthened southwest wind will carry more (less) water vapor into the low latitude plateau, causing the low latitude plateau precipitation anomaly (less). (2) through the SVD analysis of the 925hPa horizontal wind field and the sea surface temperature joint field and the low latitude plateau summer precipitation, the subtropical India is found. The oceanic dipole type SEA SST anomaly has a significant relationship with the summer precipitation in low latitude plateau. When the India ocean surface temperature in the sub tropical southwest is low (high) and the sea surface temperature in the Southeast India ocean is high (low), the summer precipitation in the low latitude plateau is much more (less). Further correlation analysis is found between the sea surface temperature and the low latitude plateau region average summer precipitation. In this study, the subtropical India Ocean dipole is one of the main external thermal forcing factors affecting the summer precipitation in low latitude plateau, and its influence is stronger than that of other types of sea air interaction (such as: ENSO) on the low latitude plateau summer precipitation. (3) based on the SVD analysis of the time coefficient of the first mode SST and 925hPa wind fields, the subtropics of the class is defined. The India Ocean dipole is positive and negative. Through the synthetic analysis, it is revealed that the subtropical India Ocean Dipole affects the Low Latitude Plateau Summer Precipitation in the north of the bay of Bengal. When the subtropical India Ocean dipole is a positive (negative) anomaly, the SST of the southwest India ocean is high (low) and the Southeast India ocean temperature is low (high). It will lead to the circulation of cyclone (anticyclone) in the India Peninsula, the north east wind (westerly) anomaly, and the divergence (convergence) of the low-level air flow in the tropical India ocean, the convergence (divergence) of the Arabia sea to the northwest of the India Peninsula, the easterly wind (westerly) in the east coast of the bay of Bengal, and the divergence of the tropical India ocean. It will lead to an anomalous radiant circulation between the hemispheres: the atmosphere rises in the tropical India ocean and sinks in the bay of Bengal. The above three factors will lead to the easterly wind (westerly wind) in the north of the bay of Bengal, which reduces the southwest wind in the average climate field and reduces the water vapor from the south wind into the low latitude plateau region. In addition, the summer precipitation anomaly in India Peninsula has a certain degree of influence on the low latitude plateau summer precipitation, and the anomaly of precipitation in the India peninsula is too much (less), which will strengthen the abnormality of the cyclone (anticyclone) in the bay of Bengal and make the bay of Bengal. The northern East Wind (west wind) is abnormal, which further affects the low Summer Precipitation in the low latitude plateau. (4) the formation of the subtropical India Ocean dipole can be traced back to the early winter and maintained to the summer, especially the subtropical India Ocean Dipole positive anomaly. The evaporative wind sea surface temperature (WES) feedback mechanism can explain the subtropical India Ocean Dipole The advection of the ocean has some contribution to the maintenance of the subtropical India Ocean dipole. (5) the numerical simulation results of the atmospheric circulation model show that the India ocean in the sub tropical southwest is relatively warm (cold), and the relatively cold (warm) SST in the Southeast India ocean is abnormally distributed, and the precipitation in the low latitude plateau can be forced to be less (more). The results of the value model are in agreement with the diagnostic analysis conclusions of the fourth chapter. The response of the summer precipitation in the low latitude plateau to the subtropical India Ocean Dipole SST anomaly is well verified. The sea air coupling model further confirms the physical mechanism of the subtropical India Ocean Dipole in the low latitude plateau in summer, and the subtropical India. The maintenance mechanism of ocean dipoles from early winter to summer.
【學(xué)位授予單位】：云南大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：P461.2

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