本文關鍵詞： 土壤濕度 雪蓋 北極濤動 北大西洋濤動 可預報性　出處：《南京大學》2017年碩士論文　論文類型：學位論文

【摘要】：除海洋外,陸地表面是氣候系統(tǒng)中的另一重要下邊界,對大氣和氣候變化也有著顯著的影響。許多研究表明前期陸地下墊面狀態(tài)異常尤其是地表水狀態(tài)(土壤濕度及雪蓋)異常與后期天氣氣候異常有著顯著關聯(lián)和影響。目前,土壤濕度反饋作用研究多集中在區(qū)域?qū)用嫔?主要討論土壤濕度異常對局地氣溫和降水的影響,而較少討論土壤濕度對大尺度大氣環(huán)流的可能影響;過去已較為詳細討論秋季歐亞雪蓋異常對冬季北極濤動的顯著影響,但考慮到秋季歐亞積雪在過去幾十年中一直有增加趨勢,雪蓋對北極濤動影響的關鍵區(qū)域及關鍵時間是否發(fā)生改變是我們的關注重點之一;過去對土壤濕度和雪蓋的研究多側(cè)重兩者的單獨作用,較少檢查兩者對大尺度大氣環(huán)流的綜合作用。北極濤動(AO)和北大西洋濤動(NAO)是北半球冬季大氣環(huán)流最主要兩個模態(tài),對北半球氣候變率有顯著影響。本文主要展開以下三方面的研究(1)秋季土壤濕度對冬季AO/NAO的影響,(2)秋季歐亞雪蓋對冬季AO、NAO影響的關鍵區(qū)域及關鍵時間的變化,(3)秋季土壤濕度和雪蓋異常對冬季AO的協(xié)同可預報性。本文選用ERA-Interim再分析的土壤濕度資料、美國冰雪中心的雪蓋衛(wèi)星觀測資料及NCEP再分析的海平面氣壓場資料。研究方法如下:(1)對秋季土壤濕度或積雪兩個預報因子的異常場與北半球或北大西洋冬季海平面氣壓場進行奇異值分解(SVD),找出兩個因子影響冬季AO/NAO的關鍵區(qū)域;(2)利用上述關鍵區(qū)域預報因子的異常場和北半球或北大西洋海平面氣壓場采用交叉驗證的SVD方法建立一元及多元線性回歸模型,對冬季觀測AO及NAO指數(shù)進行單獨回報和聯(lián)合回報,計算出AO及NAO指數(shù)的預報值與實際觀測值之間的典型相關系數(shù)(ACC)。論文有以下三點主要結論:第一,1979/80-2014/15年SVD分析結果顯示秋季中西伯利亞高原和部分西西伯利亞平原地區(qū)土壤濕度的正異常與冬季DJF正位相AO以及JFM正位相NAO顯著關聯(lián);進一步SVD交叉驗證模型的結果顯示10、11月以上區(qū)域土壤濕度對DJF AO指數(shù)回報的ACC分別為0.42及0.54,而1O、11、12月以上區(qū)域的土壤濕度對JFM NAO指數(shù)回報的ACC分別為 0.35、0.46 及 0.45。第二,為了探討雪蓋趨勢變化對冬季AO及NAO環(huán)流作用的關鍵區(qū)域及關鍵時間的影響,本文分 3 個時段(1972/73-2001/02 年、1977/78-2006/07 年、1982/83-2011/12年)來計算秋季雪蓋趨勢增加對冬季AO及NAO環(huán)流影響及其可預報性的改變。SVD分析結果顯示,在這3個時段中,10月雪蓋對冬季AO及NAO環(huán)流影響的關鍵區(qū)域均在60°N左右的西伯利亞及東歐平原北部地區(qū),11月雪蓋對冬季AO及NAO環(huán)流影響的關鍵區(qū)域均在50°N左右的蒙古高原及東歐平原南部,但是關鍵區(qū)域的范圍及變率強度在3個時段有所不同。同時,在這3個時段中,10月雪蓋對冬季AO(NAO)環(huán)流影響的顯著性從100%(96%)逐漸降低至92%(84%),對應回報的ACC從0.43(0.38)逐漸降低至0.19(0.20);而11月雪蓋對冬季AO(NAO)環(huán)流影響的顯著性從92%(70%)逐漸上升至100%(100%),對應回報的ACC從0.35(0.19)逐漸上升至0.58(0.50)。因此,在1972/73-2011/12年這40年間,秋季雪蓋對冬季AO及NAO可預報性影響的最優(yōu)時間及大值變率區(qū)域均發(fā)生了改變,可預報性的最佳月份均從10月逐漸轉(zhuǎn)變?yōu)?1月,且雪蓋的大值變率區(qū)域也均從60°N左右的西伯利亞及東歐平原北部地區(qū)南移至50°N左右的蒙古高原及東歐平原南部。第三,由于秋季土壤濕度和積雪的變化具有相當?shù)莫毩⑿?同時利用秋季土壤濕度與雪蓋異常信息比考慮單獨影響因子能夠顯著提高DJF AO的回報效果。11月土壤濕度及11月雪蓋的綜合運用對1979/80-2014/15年冬季AO回報的ACC達0.67,能夠較好地反演出實際AO指數(shù)在觀測中產(chǎn)生的異常振幅及低頻變動。我們的研究一方面揭示了秋季歐亞土壤濕度異常對北半球冬季大尺度大氣環(huán)流的顯著關聯(lián)和重要的可預報性,另一方面揭示了由于秋季歐亞積雪增加導致歐亞雪蓋對北極濤動影響的關鍵區(qū)域及關鍵時間的變化,有助于掌握積雪大尺度氣候效應的規(guī)律,從而為冬季氣候提供了具有一定意義的預報新角度和理論基礎。
[Abstract]:In addition to the oceans, the land surface is another important boundary in the climate system, the atmosphere and climate change have significant effect. Many studies show that the abnormal state of land surface especially state of surface water (soil moisture and snow cover anomaly) and weather late abnormal have significant correlation and influence. At present, soil moisture feedback studies focus on the regional level, mainly discusses the influence of soil moisture anomaly on air and precipitation, and less to discuss the possible effect of soil moisture on the large scale atmospheric circulation; the past has detailed discussion of autumn Eurasian Snow Cover Anomaly had significant impact on the Arctic Oscillation, but considering the fall of Eurasia the snow in the past few decades there has been increasing trend of snow cover on the key region and key time of the Arctic Oscillation influence whether the change is one of our focus on the past; Separate effect of soil moisture and snow cover on the two, two fewer checks comprehensive effect on the large scale atmospheric circulation. The Arctic Oscillation (AO) and the North Atlantic Oscillation (NAO) is the main Winter Atmospheric Circulation in northern hemisphere two modes, on the Northern Hemisphere climate variability has a significant impact. This paper study the following three aspects (1) effects of soil moisture on the autumn winter AO/NAO, (2) the fall of Eurasia snow winter AO, change the key region and key time on NAO (3), autumn soil moisture and snow cover anomalies on the winter AO collaborative predictability. This paper selected soil moisture data analysis ERA-Interim, SLP data analysis of satellite data and NCEP snow snow America Center. The research method is as follows: (1) abnormal field and the northern hemisphere in autumn two soil moisture or snow forecast factor or the North Atlantic winter Quaternary sea-level pressure field by singular value decomposition (SVD), to identify the two key factors affecting regional winter AO/NAO; (2) the key factor prediction of regional anomalies and the northern hemisphere or the North Atlantic sea surface pressure field using cross validation method to establish a SVD element and a multiple linear regression model, separate returns and return to winter observations of AO and NAO index, calculated AO and NAO index forecast canonical correlation coefficient between the actual and observed values (ACC). This paper has three main conclusions: first, 1979/80-2014/15 SVD analysis of positive anomaly in winter and the positive phase of DJF AO and JFM NAO showed significant positive phase correlation the soil moisture in the autumn of Siberia plateau and the west part of Siberia plain; further SVD cross validation model showed that 10,11 months of regional soil moisture return on DJF AO index ACC respectively. 0.42 and 0.54, and 1O, 11,12 months of regional soil moisture returns on JFM NAO index ACC were 0.35,0.46 and 0.45. second, in order to investigate the influence of snow cover changes of winter AO NAO circulation and the role of the key areas and key time, this paper is divided into 3 periods (1972/, 73-2001/02, 1977/78-2006/07, 1982/83-2011/12 autumn snow cover years) to calculate the trend of increasing impact on the winter AO and NAO circulation and can change the results of.SVD forecast shows that in the 3 period, the northern area in key areas of October winter snow cover on the AO and NAO circulation are at about 60 DEG N in Siberia and the plains of Eastern Europe, southern key regional influence November winter snow cover on the AO and NAO circulation are at about 50 DEG N in the Mongolia plateau and the plains of Eastern Europe, but the range of key areas and the change rate of intensity in 3 different periods. At the same time, in the 3 periods In October, the winter snow cover on AO (NAO) significantly influence the circulation from 100% (96%) decreased to 92% (84%), the corresponding return from 0.43 ACC (0.38) decreased to 0.19 (0.20); and in November the winter snow cover on AO (NAO) significantly influence the circulation from 92% (70%) gradually increased to 100% (100%), the corresponding return from 0.35 ACC (0.19) gradually increased to 0.58 (0.50). Therefore, in the 40 years from 1972/73-2011/12, the optimal time of autumn snow predictability effects on winter AO and NAO and the value of the rate of regional change, can be the best month forecast are gradually from October into November, and the southern snow big value rate region were also from about 60 DEG N in Siberia and the eastern plain of northern South to about 50 DEG N in the Mongolia plateau and the plains of Eastern Europe. In third, due to changes in soil moisture and snow fall are independent phase when, at the same time the use of wet soil in autumn And the snow cover anomaly information than separately considering the impact factor can significantly improve the comprehensive use of DJF AO.11 month return effect of soil moisture and snow cover on November winter 1979/80-2014/15 AO return ACC 0.67, abnormal amplitude and low-frequency changes can better show the actual anti AO index in observation. Our study reveals a significant association between autumn Eurasian soil moisture anomaly in the northern hemisphere large scale atmospheric circulation in winter and important predictability, on the other hand it due to the increase in autumn Eurasian Snow resulting in Eurasia snow cover on the change of the Arctic Oscillation in key areas and key time effect, helps to grasp the large scale climate effects of snow rules. In order to provide a new perspective of prediction has certain significance and theoretical basis for the winter weather.

【學位授予單位】：南京大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：P461

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