藏北高原地区地表辐射出支和能量平衡的季节变化   总被引：15，自引：5，他引：10  

马伟强  马耀明  李茂善  Z.   《冰川冻土》2005,27(5):673-679

对青藏高原地区地表能量的研究是一个十分重要的问题.基于中日合作项目"全球协调加强观测计划之亚澳季风青藏高原试验"(CAMP/Tibet)在2001年8月至2002年9月的观测数据资料,分析研究了青藏高原藏北地区地表能量,即净辐射通量、感热通量、潜热通量和土壤热通量等的变化规律,获得了有关藏北高原地表能量的新认识.  相似文献   

山西芦芽山地区树木年轮记录的1676 AD以来5～7月温度变化   总被引：7，自引：1，他引：6  

易亮  刘禹  宋惠明  李强  蔡秋芳  杨银科  孙军艳 《冰川冻土》2006,28(3):330-336

在山西芦芽山地区采取了符合国际树轮库要求的油松样本,通过交叉定年和应用区域生长模型,建立长度为328 a的标准宽度年表.根据RCS序列所揭示的气候低频变化特征,确定1676 AD以来夏季温度可划分为两个时段:1676—1865 AD和1866—2003 AD.在1676—1865 AD时期,夏季温度变化主要表现为“冷强暖弱”,其中1710—1720s为最冷时段.1866—2003 AD时期,夏季温度呈现出“总体持续变暖,冷暖交替频繁”的变化特征.  相似文献   

Observational Subseasonal Variability of the PM_2.5 Concentration in the Beijing-Tianjin-Hebei Area during the January 2021 Sudden Stratospheric Warming     

Qian LU  Jian RAO  Chunhua SHI  Dong GUO  Ji WANG  Zhuoqi LIANG  Tian WANG 《大气科学进展》2022,39(10):1623-1636

It is still not well understood if subseasonal variability of the local PM_2.5 in the Beijing-Tianjin-Hebei (BTH) region is affected by the stratospheric state. Using PM_2.5 observations and the ERA5 reanalysis, the evolution of the air quality in BTH during the January 2021 sudden stratospheric warming (SSW) is explored. The subseasonal variability of the PM_2.5 concentration after the SSW onset is evidently enhanced. Stratospheric circumpolar easterly anomalies lasted for 53 days during the January–February 2021 SSW with two evident stratospheric pulses arriving at the ground. During the tropospheric wave weakening period and the intermittent period of dormant stratospheric pulses, the East Asian winter monsoon weakened, anomalous temperature inversion developed in the lower troposphere, anomalous surface southerlies prevailed, atmospheric moisture increased, and the boundary layer top height lowered, all of which favor the accumulation of pollutant particulates, leading to two periods of pollution processes in the BTH region. In the phase of strengthened East Asian winter monsoon around the very beginning of the SSW and another two periods when stratospheric pulses had reached the near surface, opposite-signed circulation patterns and meteorological conditions were observed, which helped to dilute and diffuse air pollutants in the BTH region. As a result, the air quality was excellent during the two periods when the stratospheric pulse had reached the near surface. The increased subseasonal variation of the regional pollutant particulates after the SSW onset highlights the important role of the stratosphere in the regional environment and provides implications for the environmental prediction.  相似文献   

The Impact of Tibetan Plateau Snow Cover on the Summer Temperature in Central Asia     

Xuke LIU  Xiaojing JIA  Min WANG  Qifeng QIAN 《大气科学进展》2022,39(7):1103-1114

The current work examines the impact of the snow cover extent (SCE) of the Tibetan Plateau (TP) on the interannual variation in the summer (June?July?August) surface air temperature (SAT) over Central Asia (CA) (SAT_CA) during the 1979?2019 period. The leading mode of the summer SAT_CA features a same-sign temperature anomalies in CA and explains 62% of the total variance in SAT_CA. The atmospheric circulation associated with a warming SAT_CA is characterized by a pronounced high-pressure system dominating CA. The high-pressure system is accompanied by warm advection as well as descending motion over CA, favoring the warming of the SAT_CA. Analysis shows that the interannual variation in the summer SAT_CA is significantly positively correlated with the April SCE over the central-eastern TP. In April, higher than normal SCE over the central-eastern TP has a pronounced cooling effect on the column of the atmosphere above the TP and can persist until the following early summer. Negative and positive height anomalies appear above and to the west of the TP. In the following months, the perturbation forcing generated by the TP SCE anomalies lies near the western center of the Asian subtropical westerly jet (SWJ), which promotes atmospheric waves in the zonal direction guided by the Asian SWJ. Associated with this atmospheric wave, in the following summer, a significant high-pressure system dominates CA, which is a favorable condition for a warm summer SAT_CA.  相似文献   

Seasonal and Diurnal Variations of Cloud Systems over the Eastern Tibetan Plateau and East China: A Cloud-resolving Model Study     

Jinghua CHEN  Xiaoqing WU  Chunsong LU  Yan YIN 《大气科学进展》2022,39(7):1034-1049

The seasonal and diurnal variations of cloud systems are profoundly affected by the large-scale and local environments. In this study, a one-year-long simulation was conducted using a two-dimensional cloud-resolving model over the Eastern Tibetan Plateau (ETP) and two subregions of Eastern China: Southern East China and Central East China. Deep convective clouds (DCCs) rarely occur in the cold season over ETP, whereas DCCs appear in Eastern China throughout the year, and the ETP DCCs are approximately 20%?30% shallower than those over Eastern China. Most strong rainfall events (precipitation intensity, PI> 2.5 mm h^?1) in Eastern China are related to warm-season DCCs with ice cloud processes. Because of the high elevation of the ETP, the warm-season freezing level is lower than in Eastern China, providing favorable conditions for ice cloud processes. DCCs are responsible for the diurnal variations of warm-season rainfall in all three regions. Warm-season DCCs over the ETP have the greatest total cloud water content and frequency in the afternoon, resulting in an afternoon rainfall peak. In addition, rainfall events in the ETP also exhibit a nocturnal peak in spring, summer, and autumn due to DCCs. Strong surface heat fluxes around noon can trigger or promote DCCs in spring, summer, and autumn over the ETP but produce only cumulus clouds in winter due to the cold and dry environment.  相似文献   

Change in Precipitation over the Tibetan Plateau Projected by Weighted CMIP6 Models     

Yin ZHAO  Tianjun ZHOU  Wenxia ZHANG  Jian LI 《大气科学进展》2022,39(7):1133-1150

Precipitation over the Tibetan Plateau (TP) is important to local and downstream ecosystems. Based on a weighting method considering model skill and independence, changes in the TP precipitation for near-term (2021–40), mid-term (2041–60) and long-term (2081–2100) under shared socio-economic pathways (SSP1-1.9, SSP1-2.6, SSP2-4.5, SSSP3-7.0, SSP5-8.5) are projected with 27 models from the latest Sixth Phase of the Couple Model Intercomparison Project. The annual mean precipitation is projected to increase by 7.4%–21.6% under five SSPs with a stronger change in the northern TP by the end of the 21st century relative to the present climatology. Changes in the TP precipitation at seasonal scales show a similar moistening trend to that of annual mean precipitation, except for the drying trend in winter precipitation along the southern edges of the TP. Weighting generally suggests a slightly stronger increase in TP precipitation with reduced model uncertainty compared to equally-weighted projections. The effect of weighting exhibits spatial and seasonal differences. Seasonally, weighting leads to a prevailing enhancement of increase in spring precipitation over the TP. Spatially, the influence of weighting is more remarkable over the northwestern TP regarding the annual, summer and autumn precipitation. Differences between weighted and original MMEs can give us more confidence in a stronger increase in precipitation over the TP, especially for the season of spring and the region of the northwestern TP, which requires additional attention in decision making.  相似文献   

Sub-seasonal Prediction of the South China Sea Summer Monsoon Onset in the NCEP Climate Forecast System Version 2     

Weiwei WANG  Song YANG  Tuantuan ZHANG  Qingquan LI  Wei WEI 《大气科学进展》2022,39(11):1969-1981

This study depicts the sub-seasonal prediction of the South China Sea summer monsoon onset (SCSSMO) and investigates the associated oceanic and atmospheric processes, utilizing the hindcasts of the National Centers for Environmental Prediction (NCEP) Climate Forecast System version 2 (CFSv2). Typically, the SCSSMO is accompanied by an eastward retreat of the western North Pacific subtropical high (WNPSH), development of the cross-equatorial flow, and an increase in the east-west sea surface temperature (SST) gradient. These features are favorable for the onset of westerlies and strengthening of convection and precipitation over the South China Sea (SCS). A more vigorous SCSSMO process shows a higher predictability, and vice versa. The NCEP CFSv2 can successfully predict the onset date and evolution of the monsoon about 4 pentads (20 days) in advance (within 1–2 pentads) for more forceful (less vigorous) SCSSMO processes. On the other hand, the climatological SCSSMO that occurs around the 27th pentad can be accurately predicted in one pentad, and the predicted SCSSMO occurs 1–2 pentads earlier than the observed with a weaker intensity at longer leadtimes. Warm SST biases appear over the western equatorial Pacific preceding the SCSSMO. These biases induce a weaker-than-observed WNPSH as a Gill-type response, leading to weakened low-level easterlies over the SCS and hence an earlier and less vigorous SCSSMO. In addition, after the SCSSMO, remarkable warm biases over the eastern Indian Ocean and the SCS and cold biases over the WNP induce weaker-than-observed westerlies over the SCS, thus also contributing to the less vigorous SCSSMO.  相似文献   

亚洲热带气候态夏季风涌传播特征及其对中国降水的影响          下载免费PDF全文

任菊章  郑彬  金燕  琚建华 《热带气象学报》2022,38(2):171-179

基于1979—2020年逐日的NOAA向外长波辐射资料、NCEP/NCAR再分析风场资料,以及全球CMAP再分析降水资料,探讨了气候态亚洲热带夏季风涌的传播过程及与我国夏季相应的降水联系。分析结果表明,主汛期亚洲热带气候态夏季风季节内振荡(CISO)活动是亚洲夏季风活动的主要特征,随时间北传的亚洲热带夏季风CISO称为亚洲热带夏季风涌,主要有南亚夏季风涌和南海夏季风涌。亚洲热带夏季风涌的传播可分为四个阶段。在亚洲热带夏季风涌的发展阶段,印度洋区域低频气旋与对流活跃,孟加拉湾和南海热带区域被低频东风控制,我国大部分地区无降水发生,降水中心位于两广地区。当进入亚洲热带夏季风涌活跃阶段,孟加拉湾和南海热带地区低频气旋和对流活跃,东亚低频“PJ”波列显著,我国降水中心北移到长江以南的附近区域。亚洲热带夏季风涌减弱阶段,孟加拉湾与南海低频气旋消亡,对流减弱,低频西风加强,日本南部附近为低频反气旋控制,我国长江中下游低频南风活跃,降水中心也北移到长江中下游地区,而华南地区已基本无降水,此阶段的大气低频环流场与亚洲热带夏季风涌发展阶段基本相反。进入亚洲热带夏季风涌间歇阶段时,孟加拉湾和南海热带地区低频反气旋活跃,对流不显著,日本南部附近的低频反气旋北移减弱,我国东部基本在低频南风的控制下,降水中心也逐步北移到华北-朝鲜半岛一带,此时的大气低频环流场与亚洲季风涌活跃阶段基本相反。   相似文献   

2020年7月西北太平洋和南海“空台”环流特征分析          下载免费PDF全文

刘达  许映龙  向纯怡  陈博宇 《热带气象学报》2022,38(6):765-778

2020年7月西北太平洋和南海出现了史无前例的“空台”事件。利用NCEP再分析数据集、中国气象局(CMA)台风最佳路径等资料研究了此次“空台”现象的大尺度环流背景及动力和热力学特征。使用台风潜在生成指数(DGPI)分析发现2020年7月大尺度环流背景不利于台风生成,环流系统的异常通过影响对流层垂直风切变和垂直运动限制了台风的活动。2020年7月马斯克林高压较常年明显偏西偏弱,导致索马里急流强度减弱,越赤道气流不活跃,菲律宾以东洋面和南海海域盛行一致的偏东气流,历史同期活跃在该区域的季风槽无法建立,从而不利于热带扰动的生成。北半球极涡主体偏向西半球一侧,影响东半球冷空气势力较弱,副热带高压位置偏西;南亚高压较历史同期偏强且偏东,其东侧强盛的偏东气流将洋中槽截断,在西北太平洋区域出现反气旋性环流,该区域下沉气流增强,导致副热带高压强度增强,对流层中层强烈的下沉气流抑制了台风的生成和发展。此外,受中高层环流系统异常的影响,7月菲律宾吕宋岛以东洋面和南海地区环境垂直风切变较常年偏高2~4 m/s,南海部分海域偏高达4~8 m/s,同时该区域内异常偏强的下沉气流导致对流层低层相对湿度偏低,大气层结处于较为稳定的状态,动力和热力条件均不利于热带扰动的进一步发展。   相似文献   

CO2浓度增加背景下季风区大气辐射加热响应的差异          下载免费PDF全文

Xia Qu  Gang Huang  Xiaocong Wang 《大气和海洋科学快报》2021,14(3):19-24

大气CO2浓度增加,大气辐射平衡调整,将影响到大气的辐射加热,对季风环流的产生影响.CMIP6结果显示,大气CO2浓度增加,可减弱季风区主雨季对流层高,低层的辐射加热,加强对流层中层的辐射加热.各季风区加热响应的峰值层次不同:亚洲季风区平均层次最高(500-775 hPa),北非,南美,澳洲季风区次之(550-600 hPa),北美(600hPa)和南非季风区(600-775 hPa)较低.各季风区水云的垂直分布及其长波辐射效应的变化是形成峰值层次差异的主因.  相似文献