青藏高原積雪時空變化特征及其環(huán)流背景研究
發(fā)布時間：2019-04-11 13:00
【摘要】：積雪是冰凍圈的重要組成部分,因其高反照率、低導熱率的特性,能夠顯著改變下墊面的特性,對氣候系統(tǒng)中的能量平衡和水量循環(huán)有著深遠的影響。青藏高原積雪不僅是氣候變化的敏感指示器,還能顯著影響區(qū)域乃至全球的氣候和水文條件。因此,在氣候變暖的背景下,加強對青藏高原積雪時空變化的研究,深入探討高原積雪變化的原因機理,具有重要的理論和現實意義。本文基于MODIS 8日合成積雪產品和ERA-Interim再分析資料,采用氣候統(tǒng)計診斷方法,研究了 2002-2014年青藏高原積雪的時空變化特征,并探討了高原冬季積雪年際變化主模態(tài)與大尺度環(huán)流異常的關系,結果表明:高原積雪分布空間差異明顯,主要集中分布在高原東部、西部和南部邊緣的高海拔山區(qū),而高原內部的低海拔腹地則鮮有積雪分布。高原東部的巴顏喀拉山和東南部的念青唐古拉山是積雪的大值區(qū)也是高原積雪年際變化的大值區(qū)。高原西部的喀喇昆侖山及其周邊地區(qū)為積雪大值區(qū)也是穩(wěn)定積雪區(qū)。高原積雪主要集中在冬季和春季,高原平均積雪覆蓋率年內變化曲線呈多峰型的分布特征,10月下旬至次年3月下旬,高原平均積雪覆蓋率較高,年際波動也較大,是高原積雪較為活躍的時段。高原積雪年際變化總體呈微弱的下降趨勢,而高原東部唐古拉山和西南部喜馬拉雅山沿線的積雪呈增長的年際變化趨勢。高原冬季積雪經驗正交函數(EOF)分解的第一模態(tài)EOF1在空間上表現為東-西反位相的變化特征,其時間系數PC1以年際波動為主,與高原整體冬季積雪覆蓋率(SCF)年際變化的時間序列相一致。高原冬季積雪東-西反位相的年際變化特征與北極濤動(AO)具有密切的聯系。高原積雪PC1回歸的北半球赤道外位勢高度場表現為AO正位相,AO指數(AOI)回歸的SCF場則與冬季積雪EOF1空間分布相一致,高原冬季積雪PC1與AOI顯著正相關。AO影響高原冬季積雪年際變化的可能機制是:AO正位相時,歐洲東部大槽東移且向南加深,烏拉爾山附近的高壓脊加強東移至貝加爾湖附近,使得東亞大槽相對減弱,冬季風減弱,同時南支槽加深東移,西太平洋副高加強西伸,有利于來自南海和西北太平洋的暖濕氣流抬升進入高原,與加深的南支槽配合,高原東部自近地面至平流層底層都表現為強烈的相對上升運動,造成高原東部多雪的環(huán)流背景,高原西部則受干燥下沉的西風氣流控制,不利于降雪產生,同時,高原中西部地面氣溫異常偏高,不利于積雪的維持,致使高原西部積雪減少;AO負位相時情況相反,冬季風增強使得西伯利亞冷空氣易于從西北部入侵高原,與來自阿拉伯海和孟加拉灣的暖濕氣流在高原西部交匯,有利于降雪產生,高原東部則受來自西北的干燥下沉氣流控制,不易發(fā)生降雪,導致高原積雪東部偏少,西部偏多。
[Abstract]:Snow cover is an important part of the freezing circle. Because of its characteristics of high albedo and low thermal conductivity, it can significantly change the characteristics of the underlying surface, and has a far-reaching impact on the energy balance and water cycle in the climate system. Snow cover in Qinghai-Xizang Plateau is not only a sensitive indicator of climate change, but also can significantly affect regional and even global climate and hydrological conditions. Therefore, under the background of climate warming, it is of great theoretical and practical significance to strengthen the research on the spatio-temporal variation of snow cover in the Qinghai-Tibet Plateau and to explore the causes and mechanisms of the snow change in the plateau. Based on the MODIS 8-day synthetic snow product and ERA-Interim reanalysis data, the temporal and spatial characteristics of snow cover over the Qinghai-Xizang Plateau from 2002 to 2014 are studied by using the climatic statistical diagnosis method. The relationship between the interannual variation of snow cover in winter and the large-scale circulation anomaly is discussed. The results show that the spatial difference of snow cover distribution in the plateau is obvious, mainly distributed in the high altitude mountain areas of the eastern, western and southern edge of the plateau. On the other hand, the low altitude hinterland of the plateau has little snow distribution. The Banyankala mountain in the eastern part of the plateau and the Nianqingtang Gula mountain in the southeast of the plateau are the large areas of snow cover and the interannual variation of snow cover in the plateau. The Karakoram Mountain and its surrounding areas in the western part of the plateau are snow-covered areas and stable snow-covered areas. The snow cover over the plateau is mainly concentrated in winter and spring, and the annual variation curve of the average snow cover over the plateau is a multi-peak pattern. From late October to late March of the following year, the average snow cover of the plateau is high and the annual fluctuation is also large. Is the plateau snow is more active period. The interannual variation of snow cover in the plateau generally shows a weak downward trend, while the snow cover along the Tanggula Mountains in the eastern part of the plateau and along the Himalayas in the southwest of the plateau shows an increasing interannual trend. The first mode EOF1 of the empirical orthogonal function (EOF) decomposition of snow cover in the plateau is characterized by the change of the east-west phase in space, and the time coefficient PC1 is dominated by the inter-annual fluctuation. It is consistent with the time series of the interannual variation of snow cover (SCF) in winter over the plateau. The interannual variations of the East-West inversion of snow cover in winter over the plateau are closely related to the Arctic Oscillation (AO). The height field of the equatorial potential in the Northern Hemisphere of the PC1 regression of snow cover over the plateau is AO positive phase, while the SCF field of the AO index (AOI) regression is consistent with the spatial distribution of the snow EOF1 in winter. There is a significant positive correlation between PC1 and AOI in winter snow cover over the plateau. The possible mechanism of AO effect on the interannual variation of snow cover in the plateau in winter is as follows: when the AO phase is positive, the great trough in eastern Europe moves eastward and deepens southward, and the high pressure ridge near Ural Mountain moves eastward to the vicinity of Lake Baikal. As a result, the East Asian trough is relatively weakened, and the winter monsoon weakens. At the same time, the southern branch channel deepens eastward and the western Pacific subtropical high is strengthened westward, which is conducive to the warm and wet air flow coming from the South China Sea and the northwest Pacific Ocean rising to the plateau and coordinating with the deepening southern branch trough. The eastern part of the plateau shows a strong relative upward movement from near the surface to the bottom of the stratosphere, resulting in a snowy circulation background in the eastern part of the plateau, while the western part of the plateau is controlled by dry and sinking westerly airflow, which is not conducive to snowfall, and at the same time, The surface temperature of the central and western plateau is unusually high, which is not conducive to the maintenance of snow, resulting in the reduction of snow cover in the western part of the In contrast to the negative phase of AO, the enhancement of the winter monsoon makes it easier for Siberian cold air to invade the plateau from the northwest and meet warm and wet airflow from the Arabian Sea and Bay of Bengal in the western part of the plateau, which is conducive to snow production. The eastern part of the plateau is controlled by dry downdraft from the northwest, which is not easy to cause snowfall, resulting in less snow in the eastern part of the plateau and more snow in the western part of the plateau.
【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】：P426.635;P434
本文編號：2456426
[Abstract]:Snow cover is an important part of the freezing circle. Because of its characteristics of high albedo and low thermal conductivity, it can significantly change the characteristics of the underlying surface, and has a far-reaching impact on the energy balance and water cycle in the climate system. Snow cover in Qinghai-Xizang Plateau is not only a sensitive indicator of climate change, but also can significantly affect regional and even global climate and hydrological conditions. Therefore, under the background of climate warming, it is of great theoretical and practical significance to strengthen the research on the spatio-temporal variation of snow cover in the Qinghai-Tibet Plateau and to explore the causes and mechanisms of the snow change in the plateau. Based on the MODIS 8-day synthetic snow product and ERA-Interim reanalysis data, the temporal and spatial characteristics of snow cover over the Qinghai-Xizang Plateau from 2002 to 2014 are studied by using the climatic statistical diagnosis method. The relationship between the interannual variation of snow cover in winter and the large-scale circulation anomaly is discussed. The results show that the spatial difference of snow cover distribution in the plateau is obvious, mainly distributed in the high altitude mountain areas of the eastern, western and southern edge of the plateau. On the other hand, the low altitude hinterland of the plateau has little snow distribution. The Banyankala mountain in the eastern part of the plateau and the Nianqingtang Gula mountain in the southeast of the plateau are the large areas of snow cover and the interannual variation of snow cover in the plateau. The Karakoram Mountain and its surrounding areas in the western part of the plateau are snow-covered areas and stable snow-covered areas. The snow cover over the plateau is mainly concentrated in winter and spring, and the annual variation curve of the average snow cover over the plateau is a multi-peak pattern. From late October to late March of the following year, the average snow cover of the plateau is high and the annual fluctuation is also large. Is the plateau snow is more active period. The interannual variation of snow cover in the plateau generally shows a weak downward trend, while the snow cover along the Tanggula Mountains in the eastern part of the plateau and along the Himalayas in the southwest of the plateau shows an increasing interannual trend. The first mode EOF1 of the empirical orthogonal function (EOF) decomposition of snow cover in the plateau is characterized by the change of the east-west phase in space, and the time coefficient PC1 is dominated by the inter-annual fluctuation. It is consistent with the time series of the interannual variation of snow cover (SCF) in winter over the plateau. The interannual variations of the East-West inversion of snow cover in winter over the plateau are closely related to the Arctic Oscillation (AO). The height field of the equatorial potential in the Northern Hemisphere of the PC1 regression of snow cover over the plateau is AO positive phase, while the SCF field of the AO index (AOI) regression is consistent with the spatial distribution of the snow EOF1 in winter. There is a significant positive correlation between PC1 and AOI in winter snow cover over the plateau. The possible mechanism of AO effect on the interannual variation of snow cover in the plateau in winter is as follows: when the AO phase is positive, the great trough in eastern Europe moves eastward and deepens southward, and the high pressure ridge near Ural Mountain moves eastward to the vicinity of Lake Baikal. As a result, the East Asian trough is relatively weakened, and the winter monsoon weakens. At the same time, the southern branch channel deepens eastward and the western Pacific subtropical high is strengthened westward, which is conducive to the warm and wet air flow coming from the South China Sea and the northwest Pacific Ocean rising to the plateau and coordinating with the deepening southern branch trough. The eastern part of the plateau shows a strong relative upward movement from near the surface to the bottom of the stratosphere, resulting in a snowy circulation background in the eastern part of the plateau, while the western part of the plateau is controlled by dry and sinking westerly airflow, which is not conducive to snowfall, and at the same time, The surface temperature of the central and western plateau is unusually high, which is not conducive to the maintenance of snow, resulting in the reduction of snow cover in the western part of the In contrast to the negative phase of AO, the enhancement of the winter monsoon makes it easier for Siberian cold air to invade the plateau from the northwest and meet warm and wet airflow from the Arabian Sea and Bay of Bengal in the western part of the plateau, which is conducive to snow production. The eastern part of the plateau is controlled by dry downdraft from the northwest, which is not easy to cause snowfall, resulting in less snow in the eastern part of the plateau and more snow in the western part of the plateau.
【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】：P426.635;P434
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