西北地区大气水分特征及相关问题的初步研究
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摘要
本文用1951．1～2000．12期间NCEP／NCAR再分析格点资料，首先分析了西北地区东、西部代表站天水、乌鲁木齐上空对流层整层可降水量的演变特点，并与全球同纬度带的情况作了对比。其次分析了50年来1、4、7、10各月份西北地区大气水分和水汽平均输送的季节性气候特征。再次，对上世纪90年代西北地区重大干旱事件期间大气可降水量、水汽输送等进行了分析，并与典型湿年进行对比，从大气水分特征的角度探讨了这次重大干旱事件的可能形成原因。最后，分析了近50年来西北地区东部垂直运动强度的年代际变化特征。主要得出了如下结论：
(1)西北地区东、西部对流层整层大气可降水量在1951-2000年近50年来表现出不同的变化趋势：90年代以来，东部明显减少，而西部有所增加，且东部减少的幅度在北半球同纬度地区最大。这是上世纪九十年代中后期天水重大干旱事件发生的一个背景条件。这说明，所谓西北地区东部干旱化的趋势，不仅表现在地面降水量的长期演变方面，而且表现在对流层整层水汽含量方面。东西可降水量不同的变化趋势与各自降水量的变化趋势一致。
(2)西北地区全年水汽输送主要来自与其南面相邻的青藏高原中西部的西南暖湿气流以及陕西南部的东南暖湿气流。西北地区西部的塔里木盆地以及其南面相邻的青藏高原上空以及四川盆地北部常年维持水汽的辐合，而新疆北部没有明显的辐合辐散特征，西北地区中部及东部主要是水汽的辐散区。
(3)对比西北地区东部重大干旱事件期间和典型湿年大气水分平均特征发现：干年西北地区东部全区整层大气可降水量明显少于湿年，且水汽输送减弱，水汽辐合程度也有所减小。这些因素均对产生降水极为不利。
(4)西北地区东部垂直运动的强弱具有一定的年代际变化，90年代以来，强度趋于减弱，成为该区90年代降水减少的一个动力背景。
By utilizing the NCEP/NCAR reanalysis gridded specfic humidity data during 1951.1 to 2000.12, firstly, the evolution features of the whole troposphere over Tianshui and Wulumuqi , which are respectively in the east and west of Northwest China (NWC ) , was investigated and contrasted with what in other places in the same latitude over the North-hemisphere. Secondly, the mean seasonal climate characteristics of atmosphere water vapor and its transport flux over NWC respectively in January, April, July and October during the past 50 years was discussed. Lastly, the Precipitable Water (PV) and vapor transport flux during the great drought affair in the east of NWC in 1990s' have been analyzed and compared with what during wet years. The reason that resulted to that drought affair was studied from the point of water vapor in the atmosphere. The main results are as follows:
(1) The evolutionary features of precipitable water in the whole troposphere in Northwest China are different between over the east region and over the west region during the past 50 years from 1951-2000: in the 1990s' the PV in the east of NCW is evidently decreased , and the scope of the descent is the largest one in the same latitude over the North-hemisphere , on the contrary, which in the west regions showed increasing trend . That is to say , the so-called drought trend in the east of NWC , is not only point to the evolution of precipitation on the ground in the long term, but also to the vapor content in the whole troposphere. The different trends of PV between east region and west region are consistent with what of precipitation.
(2) The yearly vapor water transport in Northwest China is mainly consist of the west-southly air stream from the center-west of Qinghai-Xizang Plateau and the east-southly air stream from the South of Shanxi province. In the whole year, the air stream always convergent in Talimu Basin, Qinghai-Xizang Plateau and the north of Sichuan Plateau; there is no marked convergence or divergence signal in the North of Xinjiang; the air stream over the center and east of Northwest is always divergent.
(3) The mean features of vapor water in the atmosphere in the east of NWC between during the great drought affair and dry years are contrasted and shows that, the Precipitable Water in the whole troposphere is evidently reduced, and the vapor transport is also weakened, the degree of convergence of water vapor is lessened. All these facts play against the production of precipitation.
(4) The intensity of the vertical movement of the air over the east of NWC, from the 1990s', it tended to weaker, which is regarded as a dynamic background condition.
(1)西北地区东、西部对流层整层大气可降水量在1951-2000年近50年来表现出不同的变化趋势：90年代以来，东部明显减少，而西部有所增加，且东部减少的幅度在北半球同纬度地区最大。这是上世纪九十年代中后期天水重大干旱事件发生的一个背景条件。这说明，所谓西北地区东部干旱化的趋势，不仅表现在地面降水量的长期演变方面，而且表现在对流层整层水汽含量方面。东西可降水量不同的变化趋势与各自降水量的变化趋势一致。
(2)西北地区全年水汽输送主要来自与其南面相邻的青藏高原中西部的西南暖湿气流以及陕西南部的东南暖湿气流。西北地区西部的塔里木盆地以及其南面相邻的青藏高原上空以及四川盆地北部常年维持水汽的辐合，而新疆北部没有明显的辐合辐散特征，西北地区中部及东部主要是水汽的辐散区。
(3)对比西北地区东部重大干旱事件期间和典型湿年大气水分平均特征发现：干年西北地区东部全区整层大气可降水量明显少于湿年，且水汽输送减弱，水汽辐合程度也有所减小。这些因素均对产生降水极为不利。
(4)西北地区东部垂直运动的强弱具有一定的年代际变化，90年代以来，强度趋于减弱，成为该区90年代降水减少的一个动力背景。
By utilizing the NCEP/NCAR reanalysis gridded specfic humidity data during 1951.1 to 2000.12, firstly, the evolution features of the whole troposphere over Tianshui and Wulumuqi , which are respectively in the east and west of Northwest China (NWC ) , was investigated and contrasted with what in other places in the same latitude over the North-hemisphere. Secondly, the mean seasonal climate characteristics of atmosphere water vapor and its transport flux over NWC respectively in January, April, July and October during the past 50 years was discussed. Lastly, the Precipitable Water (PV) and vapor transport flux during the great drought affair in the east of NWC in 1990s' have been analyzed and compared with what during wet years. The reason that resulted to that drought affair was studied from the point of water vapor in the atmosphere. The main results are as follows:
(1) The evolutionary features of precipitable water in the whole troposphere in Northwest China are different between over the east region and over the west region during the past 50 years from 1951-2000: in the 1990s' the PV in the east of NCW is evidently decreased , and the scope of the descent is the largest one in the same latitude over the North-hemisphere , on the contrary, which in the west regions showed increasing trend . That is to say , the so-called drought trend in the east of NWC , is not only point to the evolution of precipitation on the ground in the long term, but also to the vapor content in the whole troposphere. The different trends of PV between east region and west region are consistent with what of precipitation.
(2) The yearly vapor water transport in Northwest China is mainly consist of the west-southly air stream from the center-west of Qinghai-Xizang Plateau and the east-southly air stream from the South of Shanxi province. In the whole year, the air stream always convergent in Talimu Basin, Qinghai-Xizang Plateau and the north of Sichuan Plateau; there is no marked convergence or divergence signal in the North of Xinjiang; the air stream over the center and east of Northwest is always divergent.
(3) The mean features of vapor water in the atmosphere in the east of NWC between during the great drought affair and dry years are contrasted and shows that, the Precipitable Water in the whole troposphere is evidently reduced, and the vapor transport is also weakened, the degree of convergence of water vapor is lessened. All these facts play against the production of precipitation.
(4) The intensity of the vertical movement of the air over the east of NWC, from the 1990s', it tended to weaker, which is regarded as a dynamic background condition.
引文
[1] 么枕生．1959，气候学原理．北京：科学出版社．1-510．
[2] 董安祥，郝惠铃，向军．西北地区历史上几次严重的干旱灾害及分析．甘肃气象，1997，15(3)：25-27．
[3] 谢金南，李栋梁，董安祥等．甘肃省干旱气候变化及其对西部大开发的影响．见：谢金南主编，中国西北干旱气候变化与预测研究(二)，北京：气象出版社，2000，197-206．
[4] 谢金南，周嘉陵．西北地区中、东部降水趋势的初步研究．高原气象，2001，20(4)：362-367．
[5] 马镜娴，戴彩娣．西北地区东部降水量年际和年代际变化的若干特征．高原气象，2000，19(2)：166-171．
[6] 庞文保，杨文峰，李兆元．陕西省夏季降水量的长期变化趋势．高原气象，1997，16(3)：326-330．
[7] 李艳春等．宁夏近百年来的气候变化及突变分析．见：谢金南主编，中国西部干旱气候变化与预测研究(三)，北京，气象出版社，2000，333-338
[8] 杨青，何清．塔里木河下游的气候变化与生态环境，新疆气象，2000，23(3)：11-14．
[9] 白虎志，谢金南，王宝灵等．1997年甘肃特大干旱事件的诊断分析．高原气象，1999，18(1)：55-62．
[10] 刘德祥，王宝灵，蔡忠兰等．甘肃省河东地区近4年少雨干旱的事实分析．甘肃气象，1998，16(1)：31-34．
[11] 郭铌，李栋梁，蔡晓军等．1995年中国西北东部特大干早的气候诊断与卫星监测．干旱区地理，1997，20(3)：69-74．
[12] 朱炳瑗、李栋梁．1845-1988年期间厄尔尼诺事件与我国西北旱涝．大气科学，1992，16(2)：185-192．
[13] 叶笃正，杨广基，王兴东东亚和太平洋地区上空的平均垂直环流(一)．大气科学，1979，3(1)：1-11．
[14] 杨广基，王兴东，叶笃正，东亚和太平洋地区上空的平均垂直环流(二)．大气科学，1979，3(4)：299-305．
[15] 陈彦山，秦宁生，罗哲贤，青藏高原积雪对西北地区干旱气候的影响研究．见：谢金
南主编，中国西北干旱气候变化与预测研究(三)．北京：气象出版社，2000，8—17．
[16] 徐国昌，董安祥．我国两部降水量的准3年周期．高原气象，1982，1(2)：11-17．
[17] 陆龙骅等．夏季我国副热带地区对流层上部中期振荡特征的年际变化．科学通报，1983，(3)．
[18] 徐国昌．长期天气预报的若干问题．甘肃气象，1985，(1-2)：15-21．
[19] 张佳丽，徐国昌．副高与甘肃干旱．甘肃气象，1983，(3)：12-14．
[20] 马镜娴，徐国昌．1981秋季黄河上游的特大洪水．气象，1992，(4)：7-9．
[21] 谢金南，卓嘎．台风活动对青藏高原东北侧干旱的影响．高原气象，2000，19(2)：244-252．
[22] 卓嘎等．登陆台风与我国降水的统计联系．高原气象，2000，19(2)：260—264．
[23] Manae S, Terpstra T. B. The effects of the mountains on the general circulation of the atmosphere as identified by numerical experiments. J. Atmos. Sci., 1974, 31(1),: 3-42.
[24] Manabe S, Holloway J. The seasonal variation of the hydrologic cycle as simulated by a model of the atmosphere, J. Geophys. Res., 1975, 80,1617-1649.
[25] Hahn D G, Manabe S. The role of mountains in the south Asian monsoon circulation. J. Atmos. Sci., 1975, 32,1515-1541.
[26] Broccoli A J, Manabe S. The effects of orography on Midlatitude Northem Hemisphere dry climate. J. Climat, 1992,5(11): 1181-1201.
[27] Rajagopalan B, et al. Spatiotemporal variability of ENSO and SST tele-connection to summer drought over the United States during the twentieth century. J.Climate, 2000, 13(24):4244-4255.
[28] Magana V, et al. The midsummer drought over Mexico and central American. J.Climate,1999, 12(6): 1577-1588.
[29] Nkemdirim L, et al. Comparison between the drought of the 1930s and the 1980s in the Southern Prairies of Canada. J.Climate, 1999, 12(8): 2434-2450.
[30] Garreaud R D, et al. Interarmual rainfall variability over the South American Altiplano. J.Climate, 2001,14(12): 2779-2789.
[31] Nicholson S E, et al. The relationship between EL Nino and drought over Botswana. J.Climate, 2001,14(3): 323-335.
[32] Krishinamurthy, et al. Interseasonal and interannual variability of rainfall over India. J.Climate, 2000,13(24):4366-4377.
[33] Fennessy M J, Shukla J. Seasonal prediction over North America with a regional model nested in a global model, J. Climate, 2000,13(14):2605-2627.
[34] Charney J G. Dynamics of desert and drought in the Sahel, Q. J. R. Meteorol. Soc. 1975,101,193-202.
[35] Starr, V.P. et al., Direct measurement of the hemispheric poleward flux of water vapor. J, Meteor. Res., 1955,14,217-225.
[36] Chen,T.-C., Global water vapor flux and maintenance during FGGE. Mon.Wea.Rev., 1985, 113(10): 1801-1819.
[37] 徐淑英．我国的水汽输送和水分平衡．气象学报，1958，29(1)：33-43．
[38] 谢义炳，戴武杰．中国东部地区夏季水汽输送个例计算．气象学报，1959，30，173-185．
[39] 陈隆勋，朱乾根，罗会邦等．东亚季风，北京：气象出版社，1991，49-61．
[40] 黄荣辉等．夏季东亚季风水汽输送特征及其与南亚季风区水汽输送的差别．大气科学，1998，22(4)：460-469．
[41] 张广周，马镜娴，谢金南．季风边缘区域气候变化的观测研究．见：谢金南主编，中国西北干旱气候变化与预测研究(一)．北京：气象出版社，2000，25-28．
[42] 蔡英，钱正安，宋敏红．华北和西北区干湿年间水汽场及东亚夏季风的对比分析．高原气象，2003，22(1)：14-23．
[43] 王劲松，李耀辉，康风琴，张华．西北地区东部一次暴雨的数值模拟试验．高原气象， 2000，21(3)：259-266．
[2] 董安祥，郝惠铃，向军．西北地区历史上几次严重的干旱灾害及分析．甘肃气象，1997，15(3)：25-27．
[3] 谢金南，李栋梁，董安祥等．甘肃省干旱气候变化及其对西部大开发的影响．见：谢金南主编，中国西北干旱气候变化与预测研究(二)，北京：气象出版社，2000，197-206．
[4] 谢金南，周嘉陵．西北地区中、东部降水趋势的初步研究．高原气象，2001，20(4)：362-367．
[5] 马镜娴，戴彩娣．西北地区东部降水量年际和年代际变化的若干特征．高原气象，2000，19(2)：166-171．
[6] 庞文保，杨文峰，李兆元．陕西省夏季降水量的长期变化趋势．高原气象，1997，16(3)：326-330．
[7] 李艳春等．宁夏近百年来的气候变化及突变分析．见：谢金南主编，中国西部干旱气候变化与预测研究(三)，北京，气象出版社，2000，333-338
[8] 杨青，何清．塔里木河下游的气候变化与生态环境，新疆气象，2000，23(3)：11-14．
[9] 白虎志，谢金南，王宝灵等．1997年甘肃特大干旱事件的诊断分析．高原气象，1999，18(1)：55-62．
[10] 刘德祥，王宝灵，蔡忠兰等．甘肃省河东地区近4年少雨干旱的事实分析．甘肃气象，1998，16(1)：31-34．
[11] 郭铌，李栋梁，蔡晓军等．1995年中国西北东部特大干早的气候诊断与卫星监测．干旱区地理，1997，20(3)：69-74．
[12] 朱炳瑗、李栋梁．1845-1988年期间厄尔尼诺事件与我国西北旱涝．大气科学，1992，16(2)：185-192．
[13] 叶笃正，杨广基，王兴东东亚和太平洋地区上空的平均垂直环流(一)．大气科学，1979，3(1)：1-11．
[14] 杨广基，王兴东，叶笃正，东亚和太平洋地区上空的平均垂直环流(二)．大气科学，1979，3(4)：299-305．
[15] 陈彦山，秦宁生，罗哲贤，青藏高原积雪对西北地区干旱气候的影响研究．见：谢金
南主编，中国西北干旱气候变化与预测研究(三)．北京：气象出版社，2000，8—17．
[16] 徐国昌，董安祥．我国两部降水量的准3年周期．高原气象，1982，1(2)：11-17．
[17] 陆龙骅等．夏季我国副热带地区对流层上部中期振荡特征的年际变化．科学通报，1983，(3)．
[18] 徐国昌．长期天气预报的若干问题．甘肃气象，1985，(1-2)：15-21．
[19] 张佳丽，徐国昌．副高与甘肃干旱．甘肃气象，1983，(3)：12-14．
[20] 马镜娴，徐国昌．1981秋季黄河上游的特大洪水．气象，1992，(4)：7-9．
[21] 谢金南，卓嘎．台风活动对青藏高原东北侧干旱的影响．高原气象，2000，19(2)：244-252．
[22] 卓嘎等．登陆台风与我国降水的统计联系．高原气象，2000，19(2)：260—264．
[23] Manae S, Terpstra T. B. The effects of the mountains on the general circulation of the atmosphere as identified by numerical experiments. J. Atmos. Sci., 1974, 31(1),: 3-42.
[24] Manabe S, Holloway J. The seasonal variation of the hydrologic cycle as simulated by a model of the atmosphere, J. Geophys. Res., 1975, 80,1617-1649.
[25] Hahn D G, Manabe S. The role of mountains in the south Asian monsoon circulation. J. Atmos. Sci., 1975, 32,1515-1541.
[26] Broccoli A J, Manabe S. The effects of orography on Midlatitude Northem Hemisphere dry climate. J. Climat, 1992,5(11): 1181-1201.
[27] Rajagopalan B, et al. Spatiotemporal variability of ENSO and SST tele-connection to summer drought over the United States during the twentieth century. J.Climate, 2000, 13(24):4244-4255.
[28] Magana V, et al. The midsummer drought over Mexico and central American. J.Climate,1999, 12(6): 1577-1588.
[29] Nkemdirim L, et al. Comparison between the drought of the 1930s and the 1980s in the Southern Prairies of Canada. J.Climate, 1999, 12(8): 2434-2450.
[30] Garreaud R D, et al. Interarmual rainfall variability over the South American Altiplano. J.Climate, 2001,14(12): 2779-2789.
[31] Nicholson S E, et al. The relationship between EL Nino and drought over Botswana. J.Climate, 2001,14(3): 323-335.
[32] Krishinamurthy, et al. Interseasonal and interannual variability of rainfall over India. J.Climate, 2000,13(24):4366-4377.
[33] Fennessy M J, Shukla J. Seasonal prediction over North America with a regional model nested in a global model, J. Climate, 2000,13(14):2605-2627.
[34] Charney J G. Dynamics of desert and drought in the Sahel, Q. J. R. Meteorol. Soc. 1975,101,193-202.
[35] Starr, V.P. et al., Direct measurement of the hemispheric poleward flux of water vapor. J, Meteor. Res., 1955,14,217-225.
[36] Chen,T.-C., Global water vapor flux and maintenance during FGGE. Mon.Wea.Rev., 1985, 113(10): 1801-1819.
[37] 徐淑英．我国的水汽输送和水分平衡．气象学报，1958，29(1)：33-43．
[38] 谢义炳，戴武杰．中国东部地区夏季水汽输送个例计算．气象学报，1959，30，173-185．
[39] 陈隆勋，朱乾根，罗会邦等．东亚季风，北京：气象出版社，1991，49-61．
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