北半球冬季平流层温度和Brewer-Dobson环流对11 a太阳循环的响应

采用北京气候中心大气辐射模式(BCC-RAD)、日本气象厅JRA-55月平均再分析资料,研究了北半球冬季低纬度平流层上、下两个温度异常区对太阳周期的响应及其机制。结果表明,太阳活动偏强年,低纬度的上平流层温度暖异常是由臭氧短波加热异常引起的,它在中纬度的上平流层激发出异常强西风,阻碍行星波正常上传,由波破碎驱动的Brewer-Dobson环流也减弱,该环流上升支减弱的动力加热作用导致了低纬度的下平流层暖异常。     

太平洋海温异常对其上空环流影响的分析及数值试验

本文首先用《逐月全球气候资料》中的实测风资料对80年代的两次El Nino。事件(1982—1983年和1986—1987年)太平洋地区上空环流的变化情况进行了分析研究,然后用一个九层原始方程模式对其进行数值模拟试验. 观测资料分析及数值模拟结果皆表明,赤道东太平洋的这两次海温异常都使其上空的环流发生明显的变化,但由于两次海温异常的强度、范围和延续时间有所不同,对环流的影响也不相同.本文将简要地介绍这两次El Nio期间太平洋上空环流的演变特征及数值试验的结果.     

海温强迫下的东亚夏季大气环流潜在可预报性特征

利用大气环流模式NCARCAM3,进行22a（1979—2000年）、每年8个初值的集合试验,并采用方差分析方法,研究了观测海温强迫下东亚夏季大气环流的潜在可预报性。结果表明,夏季东亚地区海平面气压场的潜在可预报性总体偏低,在中国区域呈东南高、西北低的分布特征;850hPa纬向风场、对流层500～200hPa平均温度场和500hPa位势高度场在低纬度地区的潜在可预报性明显高于中高纬度地区。500hPa位势高度场的潜在可预报性较高,东亚大部分地区大于0.5,尤其华南地区大于0.7。夏季东亚500hPa位势高度场的潜在可预报性具有明显的年际变化特征,并与夏季南海海温异常关系密切。与正常年份相比,在夏季南海海温偏暖或者偏冷年,东亚500hPa位势高度场的潜在可预报性较高     

中国南方地区盛夏高温类型及其对应的大尺度环流和海温异常

利用中国2374个站点的日最高气温资料、NCEP/NCAR大气环流资料以及NOAA海表温度资料,分析了中国南方盛夏高温的主要类型,比较了各类型高温对应的大尺度环流以及与海表温度异常信号的联系。结果表明:中国南方地区年高温日数有明显的增多趋势,利用聚类分析将中国南方盛夏高温分为江淮型、华南型和华中型3类。江淮型高温中心区域位于江淮地区,该类型高温空间范围大、发生频次高,典型的环流系统为高、低空呈现异常反气旋,西太平洋副热带高压(西太副高)偏强偏西,南北位置略偏北。该类型高温是西太副高直接控制下的高温类型,与前冬到夏季中部型厄尔尼诺衰减和春季赤道大西洋地区海温偏高有关。华南型高温中心区域在江南南部到华南地区,典型的环流系统是东亚副热带急流的位置偏南,西太副高偏强、偏西和脊线偏南,华南型高温也是西太副高直接控制下的高温,且伴随着西南季风的减弱,干热特征明显,该类型高温与东部型厄尔尼诺衰减及其与之相联系的印度洋"电容器"效应密切相关。华中型高温主要位于湖北和湖南两省,对应的环流型为西太副高偏弱、偏东,在中高纬度与北大西洋-欧亚遥相关型类似,是大陆高压控制下的高温,使得水汽条件比另两类高温好。北...     

Climate-Induced Variability of Sea Level in Stockholm： Influence of Air Temperature and Atmospheric Circulation

This study is focused on climate-induced variation of sea level in Stockholm during 1873-1995. After the effect of the land uplift, is removed, the residual is characterized and related to large-scale temperature and atmospheric circulation. The residual shows an overall upward trend, although this result depends on the uplift rate used. However, the seasonal distribution of the trend is uneven. There are even two months （June and August） that show a negative trend. The significant trend in August may be linked to fresh water input that is controlled by precipitation. The influence of the atmospheric conditions on the sea level is mainly manifested through zonal winds, vorticity and temperature. While the wind is important in the period January-May, the vorticity plays a main role during June and December. A successful linear multiple-regression model linking the climatic variables （zonal winds, vorticity and mean air temperature during the previous two months） and the sea level is established for each month. An independent verification of the model shows that it has considerable skill in simulating the variability.     

Contribution of tropical cyclones to abnormal sea surface temperature warming in the Yellow Sea in December 2004

Unusual sea surface temperature (SST) warming occurred over the Yellow Sea (YS) in December 2004. To identify the causes of the abnormal SST warming, we conducted an analysis on atmospheric circulation anomalies induced by tropical cyclones (TCs) and their impacts on upper ocean characteristics using multiple datasets. With the analysis of various datasets, we explored a new aspect of the relationship between TC activity and SST. The results show that there is a significant link between TC activity over the Northwest Pacific (NWP) and SST in the YS. The integrated effect of consecutive TCs activity induces a large-scale atmospheric cyclonic circulation anomaly over the NWP and consequently anomalous easterly winds over the YS and East China Sea. The mechanism of the unusually warm SST in the YS can be explained by considering TCs acting as an important source of Ekman heat transport that results in substantial intrusion of relatively warm surface water into the YS interior. Furthermore, TC-related circulation anomalies contribute to the retention of the resulting warm SST anomalies in the entire YS.     

Effect of methane emission increases in East Asia on atmospheric circulation and ozone

We used a fully coupled chemistry–climate model(version 3 of the Whole Atmosphere Community Climate Model,WACCM3) to investigate the effect of methane(CH4) emission increases,especially in East Asia and North America,on atmospheric temperature,circulation and ozone(O3). We show that CH4 emission increases strengthen westerly winds in the Northern Hemisphere midlatitudes,accelerate the Brewer–Dobson(BD) circulation,and cause an increase in the mass flux across the tropopause. However,the BD circulation in the tropics between 10?S and 10?N at 100 h Pa weakens as CH4 emissions increase in East Asia and strengthens when CH4 emissions increase in North America. When CH4 emissions are increased by 50% in East Asia and 15% globally,the stratospheric temperature cools by up to 0.15 K,and the stratospheric O3 increases by 45 ppbv and 60 ppbv,respectively. A 50% increase of CH4 emissions in North America(with an amplitude of stratospheric O3 increases by 60 ppbv) has a greater influence on the stratospheric O3 than the same CH4 emissions increase in East Asia. CH4 emission increases in East Asia and North America reduce the concentration of tropospheric hydroxyl radicals(4% and 2%,respectively) and increase the concentration of mid-tropospheric O3(5% and 4%,respectively) in the Northern Hemisphere midlatitudes. When CH4 emissions increase in East Asia,the increase in the tropospheric O3 concentration is largest in August. When CH4 emissions increase in North America,the increase in the O3 concentration is largest in July in the mid-troposphere,and in April in the upper troposphere.     

江淮梅雨对东亚副热带夏季风进程及海温异常的响应

利用1960—2020年江淮地区75个气象站逐日降水量、气温、相对湿度资料以及NCEP/NCAR再分析资料和Hadley中心海表温度资料，研究了东亚副热带夏季风进程变异对江淮梅雨的影响，揭示了不同类型梅雨期太平洋海温及大气环流异常特征。结果表明：8种江淮梅雨类型中，多雨型占45.9%，少雨型占54.1%，其中多雨型在前30 a占36.7%，后31 a占63.3%。江淮典型梅雨年（高温高湿多雨）的主要特征为安徽南部、江苏中部及湖北东部地区降水偏多，安徽南部、江西东北部及浙江西北部气温偏高，淮河流域湿度大；而在非典型梅雨年（低温低湿少雨）大部分地区雨量偏少，气温呈"东高西低"分布，低温中心区位于淮河中游，湿度呈"西大东小"分布。欧亚大陆中高纬度阻塞高压增强，脊前向南输送的西北气流加强且路径偏东，中国东北冷涡强度较强且位置偏西南，东亚大槽加深，槽后冷空气向南输送，有利于典型梅雨形成。当前期冬春季赤道东太平洋海温异常偏高，西太平洋海温异常偏低时，西太平洋副热带高压强度偏强、面积偏大、脊线位置偏南、西伸脊点偏西，东亚副热带夏季风推进到江淮地区的时间偏早，出梅偏晚，梅雨期降水量偏多。     

表层洋流对外强迫响应敏感度的数值研究

利用数值模拟研究了海表流场对外强迫（风应力和海表热通量）的响应特征,探讨了其对该类外强迫异常响应的敏感性以及较敏感区域。在确认本文所用的海洋环流模式能够较好地模拟表层海洋流场的气候状态之后,通过几个敏感性试验与控制（对照）试验结果的比较,发现海洋表层环流对海表风应力异常响应的敏感区域主要在赤道附近及大洋西边界海区;相对于热带外地区,热带海域（20°S～20°N）的风应力异常对于大洋表层环流的变化有着更重要的显著作用,它不仅会导致热带海域表层流场有较大的变化,对中高纬海区的表层流场特别是西边界流也有明显影响;海洋表层环流对海表热通量异常的响应除了在赤道附近海域明显之外,在中高纬海区也十分显著;在外强迫有同等异常幅度（20%）的情况下,大洋西边界海域对热通量的响应明显要强于对风应力的响应。此外,热通量异常还对南太平洋东海岸的洋流和南极大陆的绕极环流有较为明显的影响。     

一个诊断极区平流层温度变化的近似方程的检验及应用

根据一个诊断极区平流层温度变化的近似方程及其滑动累加计算方案,采用1980—2000年的MERRA-2再分析日资料计算了北半球极区低平流层100 hPa逐月的温度增量项、动力加热项和非绝热加热项,以及各项的线性趋势。结果表明,各月温度增量项与累积的动力和非绝热加热之和在气候平均的年循环意义上接近平衡,而且它们的趋势也近似平衡。进一步通过多元回归,得到了动力和非绝热加热作用对当前月温度趋势的分别贡献,动力作用是北极低平流层冬季温度趋势的主导因素并且在冬季内不一致,而非绝热作用在其他季节是主导因素。     

Parallel comparison of the northern winter stratospheric circulation in reanalysis and in CMIP5 models

A parallel comparison is made of the circulation climatology and the leading oscillation mode of the northern winter stratosphere among six reanalysis products and 24 CMIP5(Coupled Model Intercomparison Project Phase 5) models. The results reveal that the NCEP/NCAR, NECP/DOE, ERA40, ERA-Interim and JRA25 reanalyses are quite consistent in describing the climatology and annual cycle of the stratospheric circulation. The 20 CR reanalysis, however, exhibits a remarkable"cold pole" bias accompanied by a much stronger stratospheric polar jet, similar as in some CMIP5 models. Compared to the1–2 month seasonal drift in most coupled general circulation models(GCMs), the seasonal cycle of the stratospheric zonal wind in most earth system models(ESMs) agrees very well with reanalysis. Similar to the climatology, the amplitude of Polar Vortex Oscillation(PVO) events also varies among CMIP5 models. The PVO amplitude in most GCMs is relatively weaker than in reanalysis, while that in most of the ESMs is more realistic. In relation to the "cold pole" bias and the weaker oscillation in some CMIP5 GCMs, the frequency of PVO events is significantly underestimated by CMIP5 GCMs; while in most ESMs, it is comparable to that in reanalysis. The PVO events in reanalysis(except in 20CR) mainly occur from mid-winter to early spring(January–March); but in some of the CMIP5 models, a 1–2 month delay exists, especially in most of the CMIP5 GCMs. The long-term trend of the PVO time series does not correspond to long-term changes in the frequency of PVO events in most of the CMIP5 models.     

前期土壤湿度、海表面温度对中国夏季极端气温的预测能力评估

基于中国587站日最高、最低气温观测资料、月平均的ERA_interim土壤湿度（Soil Moisture,SM）再分析资料及扩展重建的海表面温度（Sea Surface Temperature,SST）资料（ERSST）,对极端气温指数进行了定义,利用变形的典型相关分析和集合典型相关分析方法（Ensemble Canonical Correlation,ECC）,分析了1979-2009年我国夏季极端气温与前期（春、前冬）SM、SST间的线性联系,建立了中国夏季极端气温预测模型,并对独立样本检验的效果进行了评估。结果表明：1）与中国夏季极端气温联系密切的前期SST异常的空间分布为类PDO（Pacific Decadal Oscillation）型,前期土壤湿度异常的区域为华南、青藏高原、东北和西北地区。2）交叉检验结果表明基于前冬预测因子的极端气温预测模型技巧高于春季,基于SM的极端气温预测模型技巧高于SST。3）独立样本检验表明基于前期SM、SST的ECC模型对中国东部夏季极端气温有一定的预测能力。因此,可以在夏季极端气温的预测业务中考虑前期SM、SST的影响。     

欧亚大陆夏季地表温度的气候特征及与大气环流的联系

采用1960—2010年NCEP/NCAR逐月再分析资料,利用经验正交函数(EOF)展开方法等,分析了欧亚大陆夏季地表温度变化特征及其与大气环流的关系。结果表明:欧亚大陆夏季地表温度的均方差在高纬度地区大于在低纬度地区。欧亚大陆夏季地表温度最主要的特征是全区一致变化,除了青藏高原东侧为降温趋势外,其他地区为变暖趋势,其中40~65°N增温明显;其次,高纬度地区表现出"-+-"变化特征。西风环流指数的变化与地表温度的增温密切相关,而EU指数与中高纬度地区地表温度异常的分布类型密切相关。根据欧亚大陆夏季地表温度的气候特征和时空变化特征,确定了5个关键区。各关键区指数都有增温趋势,但是变化特征不同。不同关键区指数的异常所对应的环流形势异常均不相同,与不同关键区地表温度密切联系的环流因子也不相同。     

东亚夏季风的年际到年代际变化及其与全球大气环流和海表温度的联系

The East Asian summer monsoon (EASM) underwent an interdecadal variation with interannual variations during the period from 1958 to 1997, its index tended to decline from a higher stage in the mid-1960＇s until it reached a lower stage after 1980＇s. Correlation analysis reveals that EASM is closely related with the global atmospheric circulation and sea surface temperature (SST). The differences between the weak and strong stage of EASM shows that, the summer monsoon circulation over East Asia and North Africa is sharply weakened, in the meantime, the westerlies in high latitudes and the trade--wind over the tropical ocean are also changed significantly. Over the most regions south of the northern subtropics, both air temperature in the lower troposphere and SST tended to rise compared with the strong stage of EASM. It is also revealed that the ocean-atmosphere interaction over the western Pacific and Indian Ocean plays a key role in interannual to interdecadal variation of EASM, most probably, the subtropical Indian Ocean is more important. On the other hand, the ENSO event is less related to EASM at least during the concerned period.     

Impact of increasing stratospheric water vapor on ozone depletion and temperature change

Using a detailed, fully coupled chemistry climate model (CCM), the effect of increasing stratospheric H_{2O on ozone and temperature is investigated. Different CCM time-slice runs have been performed to investigate the chemical and radiative impacts of an assumed 2 ppmv increase in H2O. The chemical effects of this H2O increase lead to an overall decrease of the total column ozone (TCO) by ～1% in the tropics and by a maximum of 12% at southern high latitudes. At northern high latitudes, the TCO is increased by only up to 5% due to stronger transport in the Arctic. A 2-ppmv H2O increase in the model's radiation scheme causes a cooling of the tropical stratosphere of no more than 2 K, but a cooling of more than 4 K at high latitudes. Consequently, the TCO is increased by about 2%--6%. Increasing stratospheric H2O, therefore, cools the stratosphere both directly and indirectly, except in the polar regions where the temperature responds differently due to feedbacks between ozone and H2O changes. The combined chemical and radiative effects of increasing H2O may give rise to more cooling in the tropics and middle latitudes but less cooling in the polar stratosphere. The combined effects of H2O increases on ozone tend to offset each other, except in the Arctic stratosphere where both the radiative and chemical impacts give rise to increased ozone. The chemical and radiative effects of increasing H2O cause dynamical responses in the stratosphere with an evident hemispheric asymmetry. In terms of ozone recovery, increasing the stratospheric H2O is likely to accelerate the recovery in the northern high latitudes and delay it in the southern high latitudes. The modeled ozone recovery is more significant between 2000--2050 than between 2050--2100, driven mainly by the larger relative change in chlorine in the earlier period.}     

湖南雨凇与大气环流和海温因子的相关分析

雨凇是冬季影响湖南的一种主要气象灾害。对湖南雨凇与大气环流特征量、海温异常的相关性进行了分析。结果表明：亚洲区极涡面积和东亚槽位置对中国湖南雨凇天气影响极为重要。当欧亚纬向环流为低指数时,有利于中国湖南雨凇的形成;当东大西洋欧洲区阻塞高压面积指数为低指数和乌拉尔山区阻塞高压面积指数为高指数时,湖南多雨凇天气发生。冬季西太平洋副热带高压面积偏大、强度偏强、西脊点偏西不利于中国湖南雨凇发展。拉尼娜事件结束年同时为厄尔尼诺开始年的年份湖南雨凇最为严重,厄尔尼诺事件起始年湖南雨凇强度最轻。     

中国东北夏季极端高温的分类及其与北大西洋海表温度异常的联系

利用层次聚类方法对1979-2016年中国东北夏季259次极端高温事件爆发当天的500 hPa高度场进行聚类分型,并讨论了不同类型极端高温事件的环流演变特征及其与北大西洋海表温度异常的联系.结果表明,东北夏季极端高温事件可分为3类,即西风型、阻塞型和波列型;这3类高温事件在1979-2016年分别发生了 113、89和...     

关键海区海温异常的变化与中国区域降水和气温的关系

利用 １９５１年到 １９９８年的月平均海温资料及同时期中国 １６０个测站的降水和气温的月平均资料,选用海温异常的变化趋势一变温,讨论了关键海区海温异常的变化与我国降水和气温的关系,旨在探讨变温因子与我国降水和气温的关系与海温距平与降水和气温的关系有什么不同,用变温因子能否降低降水预报的不确定性。结果表明：降水异常对海温异常两种变化趋势的响应不完全相同,说明分别讨论同一种海温异常态的两种变化趋势对降水的影响比单独讨论海温距平对降水的影响更有效一些,有助于降低预报的不确定性;除西太平洋海区外,气温异常对各海区海温异常两种变化趋势的响应较一致。降水异常对变温的响应与对海温异常的响应,有一致之处,也有不同之处。     

Simulation of the Effects of the Preceding SST Anomalies over the Tropical Eastern Pacific on Precipitation to the South of the Yangtze River in June

Numerical experiments are performed to simulate the response of the atmospheric circulation and pre-cipitation over East China in June to the sea surface temperature（SST）anomalies over the tropical eastern Pacific（TEP）from preceding September to June by using an atmospheric general circulation model （AGCM）.We constructed composite positive/negative SST anomalies（P-SSTAs/N-SSTAs）based on the observational SST anomalies over the TEP from September 1997 to June 1998.The results show that：（1） the response of the precipitation in the Yangtze River basin and its southern area（YRBS）to El Nino with different durations varies with the maximum amplitude of the precipitation anomalies appearing when the imposed duration is from November to next June,and the minimum appearing when the SST anomalies is only imposed in June.The anomalies of the precipitation are reduced when the duration of the forcing SST anomalies over the TEP is shortened and the positive SST anomalies in the preceding autumn tend to cause significantly more rainfall in the YRBS.This is in agreement with previous diagnostic analysis results.（2）The simulated precipitation anomalies over the YRBS are always obviously positive under strong or weak positive SST anomalies over the TEP.The intensity of the precipitation anomalies increases with increasing intensity of the SST anomalies in the experiments.The simulation results are consistent with the observations during the warm SST events,suggesting reasonable modeling results.（3）When negative SST anomalies in the TEP are put into the model,the results are different from those of the diagnostic analysis of La Nina events.Negative precipitation anomalies in YRBS could be reproduced only when the negative SST anomalies are strong enough.     

Variation in summer surface air temperature over Northeast Asia and its associated circulation anomalies

This study investigates the interannual variation of summer surface air temperature over Northeast Asia(NEA) and its associated circulation anomalies.Two leading modes for the temperature variability over NEA are obtained by EOF analysis.The first EOF mode is characterized by a homogeneous temperature anomaly over NEA and therefore is called the NEA mode.This anomaly extends from southeast of Lake Baikal to Japan,with a central area in Northeast China.The second EOF mode is characterized by a seesaw pattern,showing a contrasting distribution between East Asia(specifically including the Changbai Mountains in Northeast China,Korea,and Japan) and north of this region.This mode is named the East Asia(EA) mode.Both modes contribute equivalently to the temperature variability in EA.The two leading modes are associated with different circulation anomalies.A warm NEA mode is associated with a positive geopotential height anomaly over NEA and thus a weakened upper-tropospheric westerly jet.On the other hand,a warm EA mode is related to a positive height anomaly over EA and a northward displaced jet.In addition,the NEA mode tends to be related to the Eurasian teleconnection pattern,while the EA mode is associated with the East Asia-Pacific/PacificJapan pattern.