A Decadal Shift of Summer Surface Air Temperature over Northeast Asia around the Mid-1990s

This study identifies a decadal shift of summer surface air temperature （SAT） over Northeast Asia,including southeastern parts of Russia,Mongolia and northern China,around the mid-1990s.The results suggest that the SAT over the Northeast Asia experienced a significant warming after 1994 relative to that before 1993.This decadal shift also extends to northern China,and leads to a warmer summer over Northeast China and North China after the mid-1990s.The decadal warming over Northeast Asia is found to concur with the enhancement of South China rainfall around the mid-1990s.On the one hand,both the Northeast Asian SAT and South China rainfall exhibit this mid-1990s decadal shift only in summer,but not in other seasons.On the other hand,both the Northeast Asian SAT and South China rainfall exhibit this mid-1990s decadal shift not only in the summer seasonal mean,but also in each month of summer （June,July and August）.Furthermore,the decadal warming is found to result from an anticyclonic anomaly over Northeast Asia,which can be interpreted as the response to the increased precipitation over South China,according to previous numerical results.Thus,we conclude that the warming shift of summer Northeast Asian SAT around the mid-1990s was a remote response to the increased precipitation over South China.

The Interannual Variation in Monthly Temperature over Northeast China during Summer

The interannual variations of summer surface air temperature over Northeast China （NEC） were investigated through a month-to-month analysis from May to August. The results suggested that the warmer temperature over NEC is related to a local positive 500-hPa geopotential height anomaly for all four months. However, the teleconnection patterns of atmospheric circulation anomalies associated with the monthly surface air temperature over NEC behave as a distinguished subseasonal variation, although the local positive height anomaly is common from month to month. In May and June, the teleconnection pattern is characterized by a wave train in the upper and middle troposphere from the Indian Peninsula to NEC. This wave train is stronger in June than in May, possibly due to the positive feedback between the wave train and the South Asian rainfall anomaly in June, when the South Asian summer monsoon has been established. In July and August, however, the teleconnection pattern associated with the NEC temperature anomalies is characterized by an East Asia/Pacific （EAP） or Pacific/Japan （PJ） pattern, with the existence of precipitation anomalies over the Philippine Sea and the South China Sea. This pattern is much clearer in July corresponding to the stronger convection over the Philippine Sea compared to that in August.

Relation between sea surface temperature anomaly in the Atlantic and summer precipitation over the Northeast China

Based on global monthly average data set of sea surface temperature (SST) during 1950 - 1992 and global monthly average 500 hPa height during 1930- 1997 offered by NCARINCEP, the feature of SST anomaly in the Atlantic and its relation with summer precipitation over the Northeast China are analyzed. The results show that, the second eigenvector of the SST’s empirical orthogonal expanssion in winter season over the North Atlantic suggests that dist-ibution of SST anomaly has unusual meridional difference; The location of its center is basically identical to center of significant correlation region be- tween summer precipitation over the Northeast China and winter SST in the Atlantic. When winter SST in the North Atlantic is hot in south and cold in north, the blocking situation is stronger in the middle- high latitude. Correspondingly, the blocking high pressure in the northern North Pacific is also getting stronger, the westerlies circulation index in East Asia in next summer would be lower,as a result,more precipitation in the summer would be experienced over Northeast China and vice versa.

Predicting Winter Surface Air Temperature in Northeast China

The author investigates the prediction of Northeast China's winter surface air temperature (SAT),and first forecast the year to year increment in the predic-tand and then predict the predictand.Thus,in the first step,we determined the predictors for an increment in winter SAT by analyzing the atmospheric variability associated with an increment in winter SAT.Then,multi-linear re-gression was applied to establish a prediction model for an increment in winter SAT in Northeast China.The pre-diction model shows a high correlation coefficient (0.73) between the simulated and observed annual increments in winter SAT in Northeast China throughout the period 1965-2002,with a relative root mean square error of -7.9%.The prediction model makes a reasonable hindcast for 2003-08,with an average relative root mean square error of -7.2%.The prediction model can capture the in-creasing trend of winter SAT in Northeast China from 1965-2008.The results suggest that this approach to forecasting an annual increment in winter SAT in North-east China would be relevant in operational seasonal forecasts.

Influence of October Eurasian Snow on Winter Temperature over Northeast China

This paper addresses the interannual variation of winter air temperature over Northeast China and its connection to preceding Eurasian snow cover. The results show that there is a significant negative correlation between October Eurasian snow cover and following-winter air temperature over Northeast China. The snow cover located in eastern Siberia and to the northeast of Lake Baikal plays an important role in the winter air temperature anomaly. More （less） eastern Siberia snow in October can cause an atmospheric circulation anomaly pattern in which the atmospheric pressure is higher （lower） than normal in the polar region and lower （higher） in the northern mid-high latitudes. Due to the persistence of the eastern Siberia snow from October to the following winter, the winter atmospheric anomaly is favorable （unfavorable） to the widespread movement of cold air masses from the polar region toward the northern mid-high latitudes and, hence, lower （higher） temperature over Northeast China. Simultaneously, when the October snow cover is more （less）, the SST in the northwestern Pacific is continuously lower （higher） as a whole; then, the Aleutian low and the East Asia trough are reinforced （weakened）, favoring the lower （higher） temperature over Northeast China.

CLIMATIC FEATURES OF SUMMER TEMPERATURE IN NORTHEAST CHINA UNDER WARMING BACKGROUND

By using,summer temperature data in 26 stations from 1951 to 2003, the variation characteristics of summer temperature in Northeast China （NET） were analyzed based on the background of climate wanning. The results showed that the warming in summer was 0.15~C/10a in Northeast China, which was higher than that on the global, Northern Hemisphere or Northeast Asia scale in the recent 50 years. The responses of NET to global warming were shown in 3 aspects mainly. Firstly, it became warm and the average temperature increased in summer; secondly, the temperature variability increased, which displayed the increase of climatic instability; thirdly, the disaster of low temperature decreased and high temperature damage increased obviously, but the disaster of low temperature still existed in some areas under global warming background, which would be worthy of notice further.

On the relationship between convection intensity of South China Sea summer monsoon and air-sea temperature difference in the tropical oceans

The annual, interannual and inter-decadal variability of convection intensity of South China Sea (SCS) summer monsoon and air-sea temperature difference in the tropical ocean is analyzed, and their relationship is discussed using two data sets of 48-a SODA (simple ocean data assimilation) and NCEP/NCAR. Analyses show that in wintertime Indian Ocean (WIO), springtime central tropical Pacific (SCTP) and summertime South China Sea-West Pacific (SSCSWP), air-sea temperature difference is significantly associated with the convection intensity of South China Sea summer monsoon. Correlation of the inter-decadal time scale (above 10 a) is higher and more stable. There is inter-decadal variability of correlation in scales less than 10 a and it is related with the air-sea temperature difference itself for corresponding waters. The inter-decadal variability of the convection intensity during the South China Sea summer monsoon is closely related to the inter-decadal variability of the general circulation of the atmosphere. Since the late period of the 1970s, in the lower troposphere, the cross-equatorial flow from the Southern Hemisphere has intensified. At the upper troposphere layer, the South Asian high and cross-equatorial flow from the Northern Hemisphere has intensified at the same time. Then the monsoon cell has also strengthened and resulted in the reinforcing of the convection of South China Sea summer monsoon.

Impact of Autumn SST in the Japan Sea on Winter Rainfall and Air Temperature in Northeast China

We studied the impact of sea surface temperature anomaly(SSTA) in the Japan Sea and the sea area east of Japan on the winter rainfall and air temperature in Northeast(NE) China using the singular value decomposition(SVD) and empirical orthogonal function(EOF). The monthly-mean rainfall data observed at 160 stations in China, monthly-mean sea surface temperature(SST) of the Hadley Center for Climate Prediction and Research and monthly-mean air temperature from the NCEP reanalysis during 1960–2011 were used. Correlation analysis indicates that the SSTAs in the Japan Sea in September may last for three or four months and are an important index for forecasting the winter rainfall and air temperature in NE China. Positive SSTAs in the central Japan Sea and in the sea area east of Tokyo correspond to positive rainfall anomaly and negative air temperature anomaly in NE China. With the rise of SST in the Japan Sea, a weak cyclone appears over the Japan Sea. The northeasterly wind transports water vapor from the Okhotsk to NE China, resulting in more rainfall and lower air temperature. Negative SSTA years are accompanied by warmer air temperature and less snow in NE China. The 1000 h Pa geopotential height anomaly and wind anomaly fields are simulated by IAP-9L model, which supports the analysis results.

The efficacy of Kriging spatial interpolation for filling temporal gaps in daily air temperature data: A case study in northeast China

Quality-controlled and serially complete daily air temperature data are essential to evaluating and modelling the influences of climate change on the permafrost in cold regions. Due to malfunctions and location changes of observing stations, temporal gaps （i.e., missing data） are common in collected datasets. The objective of this study was to assess the efficacy of Kriging spatial interpolation for estimating missing data to fill the temporal gaps in daily air temperature data in northeast China. A cross-validation experiment was conducted. Daily air temperature series from 1960 to 2012 at each station were estimated by using the universal Kriging （UK） and Kriging with an external drift （KED）, as appropriate, as if all the ob-servations at a given station were completely missing. The temporal and spatial variation patterns of estimation uncertainties were also checked. Results showed that Kriging spatial interpolation was generally desirable for estimating missing data in daily air temperature, and in this study KED performed slightly better than UK. At most stations the correlation coefficients （R2） between the observed and estimated daily series were 〉0.98, and root mean square errors （RMSEs） of the estimated daily mean （Tmean）, maximum （Tmax）, and minimum （Tmin） of air temperature were 〈3 ℃. However, the estimation quality was strongly affected by seasonality and had spatial variation. In general, estimation uncertainties were small in summer and large in winter. On average, the RMSE in winter was approximately 1 ℃ higher than that in summer. In addition, estimation uncertainties in mountainous areas with complex terrain were significantly larger than those in plain areas.

Impacts of Polar Vortex,NPO,and SST Configurations on Unusually Cool Summers in Northeast China.Part I:Analysis and Diagnosis

This study unveils the evolution of two major early signals in the North Pacific atmosphere-ocean system that heralded abnormal high-pressure blockings and cold-vortex activities across Northeast China, based on an analysis of the configurations of major modes including the polar vortex, the North Pacific Oscillation （NPO）, and SST in the preceding winter and spring and atmospheric low-frequency disturbances in Northeast China. We analyzed these aspects to understand the atmosphere ocean physical coupling processes characterized by the two early signals, and here we explain the possible mechanisms through which dipole circulation anomalies affect the summer low-temperature processes in Northeast China. We further analyzed the interdecadal variation background and associated physical processes of the two early signals.

2021年11月7—9日辽宁省极端雨雪天气分析

选用常规气象观测资料、人工加密观测资料和NCEP/NCAR格点资料,对2021年11月7—9日辽宁省极端雨雪天气进行诊断分析。结果表明:东北冷涡和地面气旋为此次极端雨雪天气的主要影响系统,对流层中低层辐合、高层辐散以及强的冷暖气流交汇,是产生极端雨雪天气的主要原因;高低空急流耦合和高空辐散抽吸作用,配合东北冷涡动力抬升作用,暖湿低空急流沿冷垫爬升,进一步加强了上升运动。暖湿急流为此次极端雨雪天气提供了充沛的水汽条件,暖湿急流的增强对应水汽辐合作用增强,配合低层冷垫和东北冷涡的动力抬升作用,对降雪有明显增幅作用;地面辐合线沿地形分布,触发了此次极端强降雪天气。地形阻挡导致地面冷空气堆积形成冷垫,是极端降雪天气发生的重要原因。温度层结差异是鞍山、岫岩雨雪相态差异的主要原因。具有冻结层特征的低层冷垫,为鞍山极端暴雪提供了有利的温度层结条件;融化层厚度和地面温度是岫岩出现冻雨的关键因素。

Seasonal Prediction of Summer Temperature over Northeast China Using a Year-to-Year Incremental Approach

We present a model for predicting summertime surface air temperature in Northeast China（NESSAT） using a year-to-year incremental approach.The predicted value for each year＇s increase or decrease of NESSAT is added to the observed value within a particular year to yield the net forecast NESSAT.The seasonal forecast model for the year-to-year increments of NESSAT is constructed based on data from 1975- 2007.Five predictors are used：an index for sea ice cover over the East Siberian Sea,an index for central Pacific tropical sea surface temperature,two high latitude circulation indices,as well as a North American pressure index.All predictors are available by no later than March,which allows for compilation of a seasonal forecast with a two-month lead time.The prediction model accurately captures the interannual variations of NESSAT during 1977-2007 with a correlation coefficient between the predicted and observed NESSAT of 0.87（accounting for 76%of total variance） and a mean absolute error（MAE） of 0.3℃.A cross-validation test during 1977-2008 demonstrates that the model has good predictive skill,with MAE of 0.4℃and a correlation coefficient between the predicted and observed NESSAT of 0.76.

The 2009 Summer Low Temperature in Northeast China and Its Association with Prophase Changes of the Air-Sea System

Under the background of global warming, summer （JJA） low temperature events in Northeast China had not occurred for about 15 yr since 1994, but one such event took place in 2009. By using the NCEP/NCAR reanalysis data, the 100-yr station temperature data at Harbin and Changchun, and the Hadley Center sea surface temperature （SST） data, this paper intends to reveal the cause, circulation background, and influencing factors of this event. Analysis of both horizontal and vertical circulations of a low-value system over Northeast China in summer 2009 during the low temperature event shows that anomalous activities of the Northeast China cold vortex （NECV） played the most direct role. A decadal cooling trend of - 0.8℃ （10 yr）-1 over 1999-2008 at Changchun and Harbin was found, which is obviously out-of-phase with the linear warming trend （0.2℃ （10 yr）-1） over 1961-2000 for Northeast China in response to the global warming. The previous winter North Pacific polar vortex （NPPV） area index, significantly positively related to the observed summer temperatures of Harbin and Changchun, was also in a significantly declining tendency. These provide favorable decadal backgrounds for the 2009 low temperature event. Different from the average anomaly field of 500-hPa height for summer 1994-2008 in Northeast China, in the summer of 2009, the Arctic Oscillation （AO） showed a strong negative phase distribution, and significant negative height anomalies dominated Northeast Asia, Aleutian Islands, and North Atlantic. Furthermore, the negative phase of North Pacific Oscillation （NPO） in the winter of 2008 was obviously strong, and it maintained in the spring of 2009. Meanwhile, the SSTA in the equatorial eastern-central Pacific Ocean in the winter of 2008 showed a La Nina phase, but the strength of the La Nina weakened obviously in the spring of 2009. The abnormally strong activities of NECV in June and July of 2009 were related to the disturbances of stationary waves that replaced the original ultra-long waves over the North Pacific region in April and May 2009. The singular value decomposition （SVD） and harmonic analysis results suggest that the anomalous phase of NPO is an important precursor for summer temperature variations over Northeast China, and also a stable planetary-scale component that can be extracted from the atmospheric circulation in addition to the chaotic components on the synoptic scale.

January temperature anomalies over Northeast China and precursors

This paper analyzes the large-scale atmospheric circulation characteristics of anomalous cases of January temperatures that occurred in Northeast China during 1960-2008 and precursory oceanic conditions.The January monthly mean surface air temperature(SAT) anomalies and the duration of low temperature are used to define temperature anomaly cases.The anomalous cyclonic circulation over northeast Asia strengthens the northerly flow in cold Januarys,while the anomalous anticyclonic circulation weakens the northerly flow in the warm Januarys.The negative(positive) North Pacific sea surface temperature anomaly(SSTA) and increased(decreased) sea ice concentration in the Barents-Kara seas in the preceding month are probably linked to the cyclonic(anticyclonic) circulation pattern over northeast Asia in the cold(warm) cases.Further analyses indicate that the preceding oceanic conditions play distinct roles in the SAT anomalies over Northeast China on different time scales.Strong relationships exist between North Pacific SSTA and the SAT in Northeast China on the interannual time scale.On the other hand,the sea ice concentration is more closely associated with the interdecadal variations of SAT in Northeast China.

中国东北样带草原区植物δ^(13)C值及水分利用效率对环境梯度的响应

测定了中国东北森林 -草原样带草原区 15个常见植物种叶片的 δ1 3 C值 ,并以此作为植物长期水分利用效率的指示值 ,研究了不同植物种的水分利用效率对年均降水量、年均大气温度和海拔高度等环境梯度变化的响应。结果表明 :有相当一部分植物种的 δ1 3 C值和水分利用效率均随年均降水量和年均温增加而呈不同程度的降低趋势(如羊草 (L eymus chinensis(Trin.) Tzvel.)、家榆 (Ulmuspumila L.)、小叶锦鸡儿 (Caragana microphylla L am.)、直立黄芪 (Astragalus adsurgens Pall.)、地榆 (Sanguisorba officinalis L.)和菊叶委陵菜 (Potentila tanacetifolia Willd.ex Schlecht.)等 ) ,随海拔高度增高而呈不同程度的增加趋势 (如扁蓿豆 (Melissitus ruthenicus(L.) Peschkova)、羊草、家榆、小叶锦鸡儿、直立黄芪、地榆等 ) ;而少数几个种 (如达乌里胡枝子 (L espedeza davurica(L axm.)Schindl.) ,麻花头 (Serratula centauroides L.)等 )则与大多数种的情况截然相反 ,另外部分植物种则随环境因子变化不大 (达乌里黄芪 (Astragalus dahuricus(Pall.) DC.)、中间锦鸡儿 (Caragana intermedia Kuang et H.C.Fu)和狭叶锦鸡儿 (Caragana stenophylla Pojark.) ,冷蒿 (Artemisia frigida Willd.)、糙叶黄芪

中国东北地区及不同典型下垫面的气温异常变化分析

利用6个代表站1905-2001年较长时期的月平均气温,对缺测年代的数据进行了插补,建立了东北地区近百年平均季、年气温序列。对所建温度序列与同一区域内26个代表站平均温度序列的近46年同期资料做了相关分析,检验了序列的代表性。在所建序列基础上,分析了东北百年气温的年代、年和季节等不同时间尺度变化特点和地域分布特征,采用谱分析方法探讨了序列的周期性变化特征,并采用Mann-Kendall和Yamamoto方法对经过滑动平均的气温序列进行了突变分析。结果表明,东北近百年年平均温度表现为明显的增暖趋势,但为起伏式增暖;冬季增温非常强烈,夏季在1995年以前不仅没有升温,反而有明显降温趋势,但1995年以后夏季气温明显升高,春秋季的升温趋势与冬季类似,但幅度小得多;在区域内,增温强度似乎并不随纬度增大,纬度较低的沈阳增温最强;三种典型下垫面中以山地的增温幅度最强;功率谱分析表明了百年气温变化的2.3年和4.2年的主周期,其中2.3年周期比较显著。

东北夏季气温变异的区域差异及其与大气环流和海表温度的关系

利用1951～2000年中国东北地区23个台站资料,对东北夏季气温的时空分布进行了研究,发现其变化除具有整体的一致性外,东北南部和北部的夏季气温在年际和年代际时间尺度都表现出很大不同,其中北部区域的夏季气温在1987～1988年间发生了一次显著的气候突变.另外,剔除夏季气温全区一致变化的年份后,南北两区夏季气温与大气环流和海表温度的关系表明：突变前,影响北部和南部冷/热夏季的大气环流形势存在显著的不同,关键海域亦有很大差异：影响南部的为中纬度西太平洋和印度洋部分海域,影响北部的主要为ENSO事件;突变后,两区的夏季气温及相应大气环流和关键海区都趋于一致.在整个分析时段内,北部夏季气温与东亚夏季风存在显著负相关,而南部的关系则不明显.

冬季亚洲大陆的热力差异对亚洲季风活动的影响

亚洲冬季地面的热力状况与冬季风活动有关,对后期的天气气候变化也有重要的作用。作者用EOF方法分析了亚洲冬季地面气温的时空特征,发现第二模态表明东北亚和南亚地区的地面气温有反相变化的特征并具有明显的年代际变化。进一步研究发现,这种南亚东北亚的热力差特征与亚洲夏季风强弱有非常好的对应关系,籍此定义了一个大陆冬季南亚—东北亚热力差指数。分析表明热力差指数有非常明显的年代际变化,根据这一特征,进一步研究了夏季北半球大尺度环流和中国气候的年代际变化,发现其年代际变化对前冬亚洲大陆热力差指数的年代际特征敏感,相应大陆正、负热力差指数年代,东亚季风的变化特征几乎完全相反:南亚东北亚热力差正(负)指数年代,东亚夏季风较强(弱)。热力差指数对中国夏季降水的年代际变化也有重要影响,正(负)指数年代,中国夏季降水主要以第1(2)类雨型为主。同时,作者还分析了低纬度热带地区海温和对流活动对大陆冬季南亚东北亚热力差异响应的滞后性特征。

1951—2008年东北地区冬季气温变化及环流场特征

利用1951—2008年中国东北地区气温资料和NCEP高度场再分析资料,通过线性趋势分析和M-K检验方法,对东北地区冬季气温变化进行研究。结果表明:东北地区冬季变暖的时间是从20世纪80年代中期开始,突变年为1986年;冬季气温最暖年代出现在21世纪初;东北三省冬季累年气温变化趋势倾向基本是纬度越高气温趋势倾向值越大,特别是在1999—2008年黑龙江省冬季气温趋势倾向增温最显著。而在年气温变化趋势中,东北三省平均趋势倾向值没有冬季趋势倾向值大,其中吉林省气温趋势值最大。冷、暖冬年500 hPa高度距平场分布为冷冬负距平中心位于中国东北地区中部;暖冬年正距平中心位于贝加尔湖到中国东北地区中北部。低空冷冬年,东北地区受西北风、西风和东北风控制,冷空气势力强;暖冬年,东北地区仅受西北风影响,冷空气势力弱。

近50a东北地区夏季气温异常的时空变化特征

利用国家气候中心整编的1951—2000年中国160个站月平均气温资料,选出东北地区20个代表站,在分析东北气温季节—年际变化特征的基础之上,着重分析了东北夏季气温的年际、年代际变化的时空特征。发现:夏季气温20世纪50年代中期之前略偏高,50年代中期以后至70年代最低,80年代开始缓慢回升,90年代增暖程度加大,50a来有增暖的趋势;气温异常存在3a、4a、7a的年际周期和16a的年代际周期;东北地区夏季升温趋势与中国黄河以北地区是一致的,而与黄河以南—江南地区是反位相的,东北地区是我国夏季升温最显著的地区之一。