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.

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 warming. The results showed that the warming in summer was 0.15℃/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.

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.

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.

Numerical Experiments on the Impact of Spring North Pacific SSTA on NPO and Unusually Cool Summers in Northeast China

A set of numerical experiments designed to analyze the oceanic forcing in spring show that the combined forcing of cold （warm） El Ni（n）o （La Ni（n）a） phases in the Ni（n）o4 region and sea surface temperature anomalies （SSTA） in the westerly drifts region would result in abnormally enhanced NorthEast Cold Vortex （NECV） activities in early summer.In spring,the central equatorial Pacific El Ni（n）o phase and westerly drift SSTA forcing would lead to the retreat of non-adiabatic waves,inducing elliptic low-frequency anomalies of tropical air flows.This would enhance the anomalous cyclone-anticyclonecyclone-anticyclone low-frequency wave train that propagates from the tropics to the extratropics and further to the mid-high latitudes,constituting a major physical mechanism that contributes to the early summer circulation anomalies in the subtropics and in the North Pacific mid-high latitudes.The central equatorial Pacific La Ni（n）a forcing in the spring would,on the one hand,induce teleconnection anomalies of high pressure from the Sea of Okhotsk to the Sea of Japan in early summer,and on the other hand indirectly trigger a positive low-frequency East Asia-Pacific teleconnection （EAP） wave train in the lower troposphere.

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.

辽宁花生种植的霜冻危险性分析

热量条件是我国花生北扩的限制性因素,霜冻是东北花生种植的突出问题。辽宁是我国重要的花生出口省,花生已成为第三大作物。本文从致灾角度研究霜冻对辽宁花生种植的危险性,对保障新兴产区油料作物的面积稳定和生产安全意义重大。本文利用辽宁省1961-2020年56个气象站的60年日最低气温资料,识别花生生长季内的春、秋霜日数和初、终霜日,评估花生种植的春霜危险性和秋霜危险性,分析当前播种期和收获期在降低霜冻风险上的作用。研究发现辽宁花生的秋霜危险性从西南向东北增加,春霜危险性从南向北增加。各站点日霜冻概率在秋季呈“S”型增加,在春季呈反“S”型降低,从0到首次达到100%或从最后一次出现100%到稳定达到0均需经历2个月左右时间。可将播种界限温度对应日期至初霜日之间的时段视为东北花生安全生长期。秋霜对辽宁花生的影响大于春霜,主产区中阜新、沈阳中北部和铁岭地区秋霜危险性较高,需推迟收获期以避免秋季冻害;大部分主产区可推迟播种期以避免春季冻害,但需考虑对成熟期的影响。秋收期霜冻遭遇土壤偏湿可能成为新挑战。

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.

2018: The Hottest Summer in China and Possible Causes

In 2018,China experienced the hottest summer since 1961.The maximum,mean,and minimum temperatures all reached the highest.Air temperatures in most regions were much higher than normal;in northern China especially,the temperature anomalies were above double of the standard deviations.Consistent variations of temperature anomalies appeared in the national mean and in northern China on different timescales from intraseasonal to annual,indicating that the above normal temperature in northern China contributed significantly to the record-breaking hot summer of entire China.Relationships among the high temperature in summer 2018,the tropospheric circulation,and the global sea surface temperatures(SSTs)are further analyzed.It is found that the intensified and more northward western Pacific subtropical high(WPSH),weakened Northeast China cold vortex(NECV),and positive geopotential height anomaly from northern China to the Sea of Japan resulted in the abnormally high temperature in summer 2018.From late July to mid August,the WPSH was stronger than normal,with its ridge line jumping to north of 40°N;meanwhile,the NECV was much weaker and more northward than normal;both of the two systems led to the persistent high temperature in northern China during this period.In addition,the SSTs in Kuroshio and its extension area(K–KE)in summer 2018 were also the highest since 1961 and the greatest positive SST anomaly in K–KE was favorable for the above normal geopotential height over North China–Northeast China–Japan at 500 hPa,giving rise to the exceptionally high temperature in northern China.

Quantifying extreme climatic conditions for maize production using RZWQM in Siping,Northeast China

Climate change has a great influence on agricultural production,especially under extreme climatic conditions.In this study,Root Zone Water Quality Model(RZWQM)was used to predict grain yields of maize in the Siping region,Jilin Province,Northeast China during the period from 1951 to 2015;and the response of grain yield to main climatic variables was qualitatively analyzed,especially in three special years of 1954,2000 and 2009.Results showed that 1℃ increase for minimum,maximum and mean air temperatures may produce 1224 kg/hm^(2),1860 kg/hm^(2) and 1540 kg/hm^(2) more grain yields,respectively,and seasonal rainfall amount of less than 450 mm,especially at the flowering and grain filling stages,greatly reduced grain yields.In the years of 1954,2000 and 2009,grain yields were reduced by 41%,47%and 40%compared to their mean value,respectively,correspondingly because of extra low temperature(lower by 2.1℃-2.3℃),less rainfall at the grain filling stage(36 mm)and extra high temperature(higher by 1.7℃-1.8℃),and less seasonal rainfall(252 mm).To reduce extreme climate’s effects on grain yield,it is suggested that supplementary irrigation at the flowering and grain filling stages should be provided when rainfall is much less at this stage and also appropriate maize species based on the longtime weather forecast should be selected.

2013年春季我国气候异常特征及其可能原因

2013年春季,全国平均气温较常年同期偏高1.0℃,平均降水量较常年同期偏多8.3%,但气温和降水空间分布不均,东北气温持续偏低,华北出现区域性气象干旱。分析表明:2013年冬春季北极涛动(Arctic Oscillation,AO)持续强的负位相;3和4月东北冷涡活跃,不仅频次偏多且强度偏强;同时,从2013年秋季开始东北地区积雪面积持续偏大,这些因子共同作用造成东北出现强的持续性低温。而2012年冬季以来西伯利亚高压持续偏弱,同时异常高脊控制我国北方大部地区,加之水汽输送不足,造成华北地区出现区域性气象干旱。

气候变暖对东北三省春玉米严重低温冷害及种植布局的影响

以我国对气候变化较为敏感的东北三省为例,利用1961～2007年78个气象站的资料,结合玉米生长季温度距平冷害指标,分析了气候变暖对东北三省春玉米严重低温冷害及种植布局的影响。结果表明:(1)气候变暖背景下,从20世纪60年代到21世纪初,东北三省各地区春玉米严重冷害受害程度总体表现为减少趋势,但由于不同地方温度波动幅度较大,区域性的严重冷害发生频率也随之加大;就平均发生频率空间分布而言,1961～2007年严重冷害的平均发生频率表现为东北部高于西南部,最大值出现在黑龙江北部(38%),最低值在辽宁南部(4%)。(2)气候变暖背景下,不同熟性玉米品种可种植界线明显北移东延,早熟品种逐渐被中、晚熟品种取代,中、晚熟品种可种植面积不断扩大。(3)随着不同熟性玉米品种种植区域北移东延,严重低温冷害出现频率明显增加,种植风险也在增大。

中国东北地区低温冷害研究进展与展望(英文)

Focused on the major agro-meteorological disaster in northeast China area-low temperature chilling injury,the research progresses of low temperature chilling injury in northeast China were reviewed systematically.The basic concepts which included the connotation and extension of chilling damage,the circulation characteristics and effect factors which formed summer low temperature in northeast China,the prediction,forecast and defense of low temperature chilling injury were summarized and done the outlook.

热带和中纬太平洋海温异常对东北夏季低温冷害影响的诊断分析研究

利用１９９５～１９９７ 年东北地区２３ 个测站的地面气温资料、１９５０～１９９６ 年太平洋地区月平均海温资料以及１９８０～１９９４ 年全球月平均风场资料，分析了东北夏季低温冷害的时空特征和变化规律，探讨了太平洋各区域的海温异常与低温冷害之间的可能联系及其影响机理．结果表明，用ＥＯＦ分解得到的前三个特征向量（占总方差的８４．２８％ ）基本表示了东北夏季气温的变化，用这三个特征向量重建的气温距平场，存在着３～４ 年、６～８ 年和准１６ 年的主周期，其中６～８ 年的主分量信号最强．在年代际尺度上，在１９７９ 年前后发生了由气温偏冷向偏暖的突变．热带西太平洋暖池（１４０°Ｅ～１８０°，１０°Ｓ～１０°Ｎ）是影响东北夏季气温的关键海域，那里前期冬季海表温度变化是预测东北夏季低温冷害的强信号．另一个关键海域是中纬西太平洋（１３０°Ｅ～１８０°，１０°～３０°Ｎ），前期春季的海温变化也与东北夏季低温有较密切的联系．

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.

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。

北太平洋海温异常对中国东北地区旱涝的影响

文中利用 196 1～ 2 0 0 0年中国东北地区 80个测站 4 0a的月降水和同一时期的北太平洋海温资料以及奇异值分解 (SVD)技术 ,分析了北太平洋海温异常对中国东北地区夏季旱涝的影响。结果表明 :东北地区夏季降水与北太平洋海温异常之间存在着较为密切的联系 ,当前期冬季和春季甚至是前一年夏季赤道中东太平洋海温如果处于异常偏暖 (或偏冷 )状态 ,并且西风漂流区具有较明显的SST负 (或正 )距平分布时 ,则东北大部分地区夏季降水具有整体偏多 (或偏少 )的倾向。当然 。

东北地区低温气象资料共享服务系统的技术实现

该文介绍了"东北地区低温气象资料共享服务系统"的主要实现技术,介绍了数据库技术、存储技术和Web技术在气象资料共享中的运用和实现,认为由现代网络和计算机技术构建的系统可以实现高效、可靠的专题气象资料共享服务。

东北夏季气温变化与北半球温度及极涡的关系

利用1961-2002年中国东北地区80个气象站夏季6—8月逐日气温、美国NCAR／NCEP再分析资料和国家气候中心环流因子资料，采用相关分析、SVD分解等方法，对中国东北夏季气温变化与中高纬主要环流系统的关系进行探讨。结果发现：中国东北位于东西伯利亚变温区南缘，其夏季气温年际变化规律和东西伯利亚一致；北极极涡边缘的形态变化影响东北夏季气温，不同的边缘形态对应东北不同的温度分布特征，主要是极涡边缘70°N左右的150～180°E和60～90°W两个关键区，其高度场的变化决定着东北夏季气温的变化。

欧亚和我国东北冬春季积雪对东北夏季气温的影响

根据我国东北及邻近地区123个气象站的逐日气温和积雪深度资料,欧亚大陆积雪面积以及NCEP/NCAR全球再分析月平均500hPa高度场资料,通过相关、合成分析等方法,研究了东北夏季气温异常对欧亚和我国东北冬春季积雪的响应,并从大气环流的角度出发分析了欧亚和我国东北冬春季积雪对东北夏季气温异常形成的影响机制.结果表明:东北地区夏季气温与欧亚大陆春季积雪面积以及东北冬季累积雪深的异常存在明显的关系.欧亚春季积雪面积的扩大与维持有利于8月我国东北上空500hPa位势高度的偏低,环流上表现出西欧与我国东北地区槽加深,泰梅尔阻塞高压加强的特征.由于欧亚中高纬上空的环流经向度加大,槽后脊前的西北气流加强,诱导冷空气南下,从而造成东北全区8月气温一致偏低;东北冬季累积雪深减少则有利于6月东北全区、7月东北西南部上空的位势高度偏低(负距平),造成相关区域气温偏低.研究结果对于提高东北夏季气温的短期气候预测水平具有重要意义.