ENSO與青藏高原地表熱力關(guān)系及所引起的下游效應(yīng)
發(fā)布時間：2018-08-26 19:23
【摘要】：前期ENSO事件與青藏高原積雪異常都是影響我國夏季降水的重要因素,研究二者之間的相互聯(lián)系,對我國氣候預(yù)測、夏季降水預(yù)報及防災(zāi)減災(zāi)等工作具有積極、重要的意義。因此,本文依據(jù)雪深、雪水當量兩套不同的高原積雪資料,結(jié)合85站高原地區(qū)的地表溫度觀測值、前期太平洋海溫的擴展重建資料等,分析了近20年來ENSO事件對隨后以積雪、地表溫度要素為代表的高原地表熱力狀況的影響,及對應(yīng)的大氣環(huán)流異常和可能的物理過程,并通過數(shù)值試驗進一步探討了5-8月高原異常加熱對同期大氣環(huán)流的影響。研究工作主要分為以下幾個部分:一、根據(jù)衛(wèi)星反演的高原逐月雪深、雪水當量資料,對比分析了近20年ENSO與高原東、西部積雪的相關(guān)及持續(xù)性。研究結(jié)果如下:赤道東太平洋海溫和高原東、西部雪深的相關(guān)存在明顯的差異,高原西部雪深與前期11月130oW以東赤道太平洋海溫的正相關(guān)可通過95%置信檢驗,并持續(xù)至4月,而高原東部在赤道東太平洋則一直沒有對應(yīng)的顯著正相關(guān)區(qū)。高原東、西部雪水當量與前期11月赤道東太平洋海溫相關(guān)系數(shù)的差異沒有如此明顯,尤其體現(xiàn)在4月高原東部對應(yīng)在赤道東太平洋的顯著正相關(guān)區(qū)可擴至160°W,但前期高原東部雪水當量與4月的自相關(guān)系數(shù)小于0.05顯著性檢驗臨界值0.46。大氣環(huán)流分析結(jié)果顯示,冬季厄爾尼諾成熟期至4月以前,200hPa副熱帶西風急流活動強盛,利于赤道東太平洋在對流層上層激發(fā)的Rossby波列沿急流傳至高原上空,從而引起局地對流活動增強、雨雪增多,隨著ENSO信號及作為波導的西風急流的減弱,波列趨于消失,ENSO引起的高原積雪異常也變得不顯著。二、結(jié)合高原地區(qū)85站地表溫度的觀測值,對近20年ENSO與隨后高原東部地表溫度異常的相關(guān)做了進一步分析。結(jié)論如下:厄爾尼諾次年4、5月,高原東部地表溫度顯著偏暖,與前期Ni?o3指數(shù)的相關(guān)系數(shù)分別是0.46和0.52,通過了95%的置信檢驗水平,尤其5月對應(yīng)在赤道東太平洋的顯著正相關(guān)區(qū)甚至可伸至日界線附近。更長時間尺度上,5月高原東部75站平均地表溫度與Ni?o3指數(shù)的相關(guān)系數(shù)為0.30,仍可通過0.05的顯著性檢驗。偏暖年4-6月,高原上空200、500hPa位勢高度和氣溫的距平都為正值,以4、5月份更為強大,偏冷年不完全相反。另外,El Ni?o次年3至4月,高原及鄰近地區(qū)上空的大氣環(huán)流發(fā)生明顯的轉(zhuǎn)換,200和500hPa層的位勢高度距平由負值轉(zhuǎn)為正值,500hPa氣溫距平也發(fā)生同樣的變化,而春末高原東部地表溫度的顯著偏高,很可能與3月500hPa層位于里海以北的異常暖脊沿等高線向高原輸送暖平流有關(guān)。La Ni?a次年未出現(xiàn)類似的轉(zhuǎn)變。三、利用大氣環(huán)流模式CAM3.1,對厄爾尼諾事件發(fā)生后高原地區(qū)的雪深、地表溫度異常進行模擬分析,結(jié)果如下:1997/1998個例試驗和實測海溫試驗均顯示,CAM3.1模式無法再現(xiàn)出厄爾尼諾事件發(fā)生后高原地區(qū)冬、春季雪深的正異常現(xiàn)象,甚至與前期的統(tǒng)計診斷結(jié)果完全相反,但1997/1998個例試驗?zāi)軌蜉^好地模擬出1、2月200hPa相對渦度的Rossby波列。而不同強度海溫異常試驗顯示,隨著厄爾尼諾事件的增強,高原地區(qū)的雪深異常仍以負值為主、且無對應(yīng)的線性變化,而高原東部地表溫度異常則在0附近振蕩。四、利用區(qū)域氣候模式,通過在青藏高原范圍設(shè)置三種不同強度的大氣異常加熱率,討論了5-8月青藏高原加熱異常對同期大氣環(huán)流的影響。結(jié)果表明:5月,以4K/day的速率加熱高原大氣12天后,500hPa位勢高度異常在鄂霍次克海附近為正值區(qū)、我國東北及堪察加半島以南為負值區(qū),出現(xiàn)了疑似波列結(jié)構(gòu),但200hPa呈西正東負的二極分布。6月,這種波列結(jié)構(gòu)更加明顯,200hPa形成了完整的類Okhotsk-Japan(OKJ)波列型。但其他月份未見有類似的波列結(jié)構(gòu)。7月,蒙古至鄂霍次克海及日本以東一帶地區(qū)200和500hPa的負位勢高度異常連成一片;8月,日本以東地區(qū)轉(zhuǎn)為正值中心、鄂霍次克海附近仍維持負異常。而隨著異常加熱的增強,沿6月波列傳播路徑上的各點的位勢高度異常振幅基本成比例增加。此外,射線追蹤分析結(jié)果顯示,5、6月份的波射線路徑分布類似,模擬路徑位于緯向波數(shù)為3和4對應(yīng)的射線軌跡之間。
[Abstract]:Previous ENSO events and snow cover anomalies on the Qinghai-Tibet Plateau are both important factors affecting Summer Precipitation in China. Studying the relationship between them is of positive and important significance to China's climate prediction, summer precipitation prediction and disaster prevention and mitigation. The surface temperature observations in the plateau area and the data of the expansion and reconstruction of the Pacific SST in the previous 20 years are analyzed. The effects of ENSO events on the subsequent surface thermal conditions of the plateau, represented by snow cover and surface temperature elements, are discussed. The corresponding atmospheric circulation anomalies and possible physical processes are also discussed through numerical experiments. Based on the monthly snow depth and snow water equivalent data of the plateau retrieved by satellite, the correlation and persistence between ENSO and the snow cover in the East and west of the plateau in the past 20 years are compared and analyzed. The positive correlation between the snow depth in the western plateau and the SST in the eastern equatorial Pacific Ocean can be tested by 95% confidence test until April, while there is no significant positive correlation between the snow depth in the eastern plateau and the SST in the eastern equatorial Pacific Ocean. The difference of the coefficients is not so obvious. Especially, the significant positive correlation region corresponding to the eastern equatorial Pacific Ocean in April can be expanded to 160 degrees W, but the autocorrelation coefficient between the snow water equivalence in the eastern plateau and April is less than 0.46. The strong activity of the subtropical westerly jet at 00hPa contributes to the rapid propagation of the Rossby wave train over the plateau over the eastern equatorial Pacific Ocean over the troposphere, which results in the enhancement of local convective activity and the increase of rain and snow. With the weakening of ENSO signal and westerly jet as a waveguide, the wave train tends to disappear and the snow anomaly over the plateau caused by ENSO becomes unavoidable. The results are as follows: In April and May of the following year, the surface temperature in the eastern part of the plateau was significantly warmer, and the correlation coefficients with the Ni? O 3 index were 0.46 and 0.52 respectively, which passed 95% confidence test. On a longer time scale, the correlation coefficient between the mean surface temperature at 75 stations in the eastern part of the plateau and the Ni?O 3 index is 0.30, which can still pass the significance test of 0.05. In addition, from March to April of the following year, the atmospheric circulation over the plateau and its adjacent areas changed significantly, the geopotential height anomaly in the 200 and 500 hPa layers changed from negative to positive, and the 500 hPa temperature anomaly changed similarly, while the surface temperature in the eastern part of the plateau at the end of spring was obvious. The anomalous warm ridge located north of the Caspian Sea in the 500 hPa layer in March is probably related to the conveyance of warm advection to the plateau along the contour line. La Ni? A did not undergo a similar change in the following year. 3. Using the atmospheric circulation model CAM 3.1, the snow depth and surface temperature anomalies in the plateau area after the El Nino event were simulated and analyzed. The results are as follows: 1997/1998. The CAM 3.1 model can not reproduce the positive anomaly of snow depth in winter and spring in the plateau area after the El Nino event, even contrary to the previous statistical diagnostic results. However, the Rossby wave train with relative vorticity of 200 hPa in January and February can be well simulated by the 1997/1998 model. The anomaly experiment shows that with the increase of El Nino event, the snow depth anomaly in the plateau area is still dominated by negative value, and there is no corresponding linear change, while the surface temperature anomaly in the eastern plateau oscillates around 0. Fourthly, by using the regional climate model, three different atmospheric anomalous heating rates are set up over the Qinghai-Tibet Plateau, and the 5-8 anomaly is discussed. The results show that the 500 hPa geopotential height anomaly is positive in the vicinity of the Okhotsk Sea and negative in the northeast of China and south of the Kamchatka Peninsula after 12 days of heating the plateau atmosphere at a rate of 4K/day in May. In June, this kind of wave train structure became more obvious, and a complete Okhotsk-Japan (OKJ) wave train-like structure was formed at 200 hPa. However, no similar wave train structure was found in other months. In July, the negative potential height of 200 and 500 hPa from Mongolia to the Okhotsk Sea and the area east of Japan was anomalously connected; in August, the area east of Japan turned into a positive value center and the Okhotsk Sea became a positive value center. Negative anomalies are maintained nearby, and the anomalous amplitudes of potential heights along the June wave train propagation path increase proportionally with the increase of anomalous heating.
【學位授予單位】：中國氣象科學研究院
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P732;P461.2
本文編號：2205916
[Abstract]:Previous ENSO events and snow cover anomalies on the Qinghai-Tibet Plateau are both important factors affecting Summer Precipitation in China. Studying the relationship between them is of positive and important significance to China's climate prediction, summer precipitation prediction and disaster prevention and mitigation. The surface temperature observations in the plateau area and the data of the expansion and reconstruction of the Pacific SST in the previous 20 years are analyzed. The effects of ENSO events on the subsequent surface thermal conditions of the plateau, represented by snow cover and surface temperature elements, are discussed. The corresponding atmospheric circulation anomalies and possible physical processes are also discussed through numerical experiments. Based on the monthly snow depth and snow water equivalent data of the plateau retrieved by satellite, the correlation and persistence between ENSO and the snow cover in the East and west of the plateau in the past 20 years are compared and analyzed. The positive correlation between the snow depth in the western plateau and the SST in the eastern equatorial Pacific Ocean can be tested by 95% confidence test until April, while there is no significant positive correlation between the snow depth in the eastern plateau and the SST in the eastern equatorial Pacific Ocean. The difference of the coefficients is not so obvious. Especially, the significant positive correlation region corresponding to the eastern equatorial Pacific Ocean in April can be expanded to 160 degrees W, but the autocorrelation coefficient between the snow water equivalence in the eastern plateau and April is less than 0.46. The strong activity of the subtropical westerly jet at 00hPa contributes to the rapid propagation of the Rossby wave train over the plateau over the eastern equatorial Pacific Ocean over the troposphere, which results in the enhancement of local convective activity and the increase of rain and snow. With the weakening of ENSO signal and westerly jet as a waveguide, the wave train tends to disappear and the snow anomaly over the plateau caused by ENSO becomes unavoidable. The results are as follows: In April and May of the following year, the surface temperature in the eastern part of the plateau was significantly warmer, and the correlation coefficients with the Ni? O 3 index were 0.46 and 0.52 respectively, which passed 95% confidence test. On a longer time scale, the correlation coefficient between the mean surface temperature at 75 stations in the eastern part of the plateau and the Ni?O 3 index is 0.30, which can still pass the significance test of 0.05. In addition, from March to April of the following year, the atmospheric circulation over the plateau and its adjacent areas changed significantly, the geopotential height anomaly in the 200 and 500 hPa layers changed from negative to positive, and the 500 hPa temperature anomaly changed similarly, while the surface temperature in the eastern part of the plateau at the end of spring was obvious. The anomalous warm ridge located north of the Caspian Sea in the 500 hPa layer in March is probably related to the conveyance of warm advection to the plateau along the contour line. La Ni? A did not undergo a similar change in the following year. 3. Using the atmospheric circulation model CAM 3.1, the snow depth and surface temperature anomalies in the plateau area after the El Nino event were simulated and analyzed. The results are as follows: 1997/1998. The CAM 3.1 model can not reproduce the positive anomaly of snow depth in winter and spring in the plateau area after the El Nino event, even contrary to the previous statistical diagnostic results. However, the Rossby wave train with relative vorticity of 200 hPa in January and February can be well simulated by the 1997/1998 model. The anomaly experiment shows that with the increase of El Nino event, the snow depth anomaly in the plateau area is still dominated by negative value, and there is no corresponding linear change, while the surface temperature anomaly in the eastern plateau oscillates around 0. Fourthly, by using the regional climate model, three different atmospheric anomalous heating rates are set up over the Qinghai-Tibet Plateau, and the 5-8 anomaly is discussed. The results show that the 500 hPa geopotential height anomaly is positive in the vicinity of the Okhotsk Sea and negative in the northeast of China and south of the Kamchatka Peninsula after 12 days of heating the plateau atmosphere at a rate of 4K/day in May. In June, this kind of wave train structure became more obvious, and a complete Okhotsk-Japan (OKJ) wave train-like structure was formed at 200 hPa. However, no similar wave train structure was found in other months. In July, the negative potential height of 200 and 500 hPa from Mongolia to the Okhotsk Sea and the area east of Japan was anomalously connected; in August, the area east of Japan turned into a positive value center and the Okhotsk Sea became a positive value center. Negative anomalies are maintained nearby, and the anomalous amplitudes of potential heights along the June wave train propagation path increase proportionally with the increase of anomalous heating.
【學位授予單位】：中國氣象科學研究院
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P732;P461.2
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