The 2020/21 Extremely Cold Winter in China Influenced by the Synergistic Effect of La Niña and Warm Arctic

In the first half of winter 2020/21,China has experienced an extremely cold period across both northern and southern regions,with record-breaking low temperatures set in many stations of China.Meanwhile,a moderate La Niña event which exceeded both oceanic and atmospheric thresholds began in August 2020 and in a few months developed into its mature phase,just prior to the 2020/21 winter.In this report,the mid−high-latitude large-scale atmospheric circulation anomalies in the Northern Hemisphere,which were forced by the negative phase of Arctic Oscillation,a strengthened Siberian High,an intensified Ural High and a deepened East Asian Trough,are considered to be the direct reason for the frequent cold surges in winter 2020/21.At the same time,the synergistic effect of the warm Arctic and the cold tropical Pacific(La Niña)provided an indispensable background,at a hemispheric scale,to intensify the atmospheric circulation anomalies in middle-to-high latitudes.In the end,a most recent La Niña prediction is provided and the on-coming evolution of climate is discussed for the remaining part of the 2020/21 winter for the purpose of future decision-making and early warning.

Characteristics of Temperature Change in China over the Last 2000 years and Spatial Patterns of Dryness/Wetness during Cold and Warm Periods

This paper presents new high-resolution proxies and paleoclimatic reconstructions for studying climate changes in China for the past 2000 years. Multi-proxy synthesized reconstructions show that temperature variation in China has exhibited significant 50–70-yr, 100–120-yr, and 200–250-yr cycles. Results also show that the amplitudes of decadal and centennial temperature variation were 1.3℃ and 0.7℃, respectively, with the latter significantly correlated with long-term changes in solar radiation, especially cold periods, which correspond approximately to sunspot minima. The most rapid warming in China occurred over AD 1870–2000, at a rate of 0.56°± 0.42℃（100 yr）^（-1）; however, temperatures recorded in the 20 th century may not be unprecedented for the last 2000 years, as data show records for the periods AD 981–1100 and AD1201–70 are comparable to the present. The ensemble means of dryness/wetness spatial patterns in eastern China across all centennial warm periods illustrate a tripole pattern： dry south of 25°N, wet from 25°–30°N, and dry to the north of 30°N. However, for all centennial cold periods, this spatial pattern also exhibits a meridional distribution. The increase in precipitation over the monsoonal regions of China associated with the 20 th century warming can primarily be attributed to a mega El Nino–Southern Oscillation and the Atlantic Multidecadal Oscillation. In addition, a significant association between increasing numbers of locusts and dry/cold conditions is found in eastern China. Plague intensity also generally increases in concert with wetness in northern China, while more precipitation is likely to have a negative effect in southern China.

Opposing Trends of Winter Cold Extremes over Eastern Eurasia and North America under Recent Arctic Warming

Under recent Arctic warming,boreal winters have witnessed severe cold surges over both Eurasia and North America,bringing about serious social and economic impacts.Here,we investigated the changes in daily surface air temperature(SAT)variability during the rapid Arctic warming period of 1988/89–2015/16,and found the daily SAT variance,mainly contributed by the sub-seasonal component,shows an increasing and decreasing trend over eastern Eurasia and North America,respectively.Increasing cold extremes(defined as days with daily SAT anomalies below 1.5 standard deviations)dominated the increase of the daily SAT variability over eastern Eurasia,while decreasing cold extremes dominated the decrease of the daily SAT variability over North America.The circulation regime of cold extremes over eastern Eurasia(North America)is characterized by an enhanced high-pressure ridge over the Urals(Alaska)and surface Siberian(Canadian)high.The data analyses and model simulations show the recent strengthening of the high-pressure ridge over the Urals was associated with warming of the Barents–Kara seas in the Arctic region,while the high-pressure ridge over Alaska was influenced by the offset effect of Arctic warming over the East Siberian–Chukchi seas and the Pacific decadal oscillation(PDO)–like sea surface temperature(SST)anomalies over the North Pacific.The transition of the PDO-like SST anomalies from a positive to negative phase cancelled the impact of Arctic warming,reduced the occurrence of extreme cold days,and possibly resulted in the decreasing trend of daily SAT variability in North America.The multi-ensemble simulations of climate models confirmed the regional Arctic warming as the driver of the increasing SAT variance over eastern Eurasia and North America and the overwhelming effect of SST forcing on the decreasing SAT variance over North America.Therefore,the regional response of winter cold extremes at midlatitudes to the Arctic warming could be different due to the distinct impact of decadal SST anomalies.

An Isentropic Mass Circulation View on the Extreme Cold Events in the 2020/21 Winter

Three extreme cold events successively occurred across East Asia and North America in the 2020/21 winter.This study investigates the underlying mechanisms of these record-breaking persistent cold events from the isentropic mass circulation(IMC)perspective.Results show that the midlatitude cold surface temperature anomalies always co-occurred with the high-latitude warm anomalies,and this was closely related to the strengthening of the low-level equatorward cold air branch of the IMC,particularly along the climatological cold air routes over East Asia and North America.Specifically,the two cold surges over East Asia in early winter were results of intensification of cold air transport there,influenced by the Arctic sea ice loss in autumn.The weakened cold air transport over North America associated with warmer northeastern Pacific sea surface temperatures(SSTs)explained the concurrent anomalous warmth there.This enhanced a wavenumber-1 pattern and upward wave propagation,inducing a simultaneous and long-lasting stronger poleward warm air branch(WB)of the IMC in the stratosphere and hence a displacement-type Stratospheric Sudden Warming(SSW)event on 4 January.The WB-induced increase in the air mass transported into the polar stratosphere was followed by intensification of the equatorward cold branch,hence promoting the occurrence of two extreme cold events respectively over East Asia in the beginning of January and over North America in February.Results do not yield a robust direct linkage from La Niña to the SSW event,IMC changes,and cold events,though the extratropical warm SSTs are found to contribute to the February cold surge in North America.

Trends of Temperature Extreme Indices over Arusha and Kilimanjaro Regions in Tanzania

The study aimed at analyzing the trends and variability of temperature extremes over the northeastern highlands in Tanzania, specifically over Arusha and Kilimanjaro regions. Quality controlled mean monthly, daily maximum and minimum temperature data for the period 1961 to 2020, obtained from Tanzania Meteorological Authority, were used in the study. Rclimdex and the National Climate Monitoring Products (NMCP) software, developed by the World Meteorological Organization (WMO), were used for computation of the indices at a monthly, seasonal and annual time scale. The computed indices were also subjected to trend analysis to determine their direction and magnitude of change. Extraction and assessment of the top five highest and lowest maximum and minimum temperatures were also done. Increasing trends of temperature anomalies for seasonal and annual timescales were observed for both Arusha and Kilimanjaro regions. Also, the increasing trends of warm and extreme warm days and nights and relatively increasing trends of cold and extreme cold days and nights were observed for both regions. The highest ever recorded temperatures since the establishment of the two stations were 36.3?C observed on 16th February 2011 and 38.6?C observed on 22nd February 2005 for Arusha and Kilimanjaro respectively. These results indicate that The last two decades have been characterized by enhanced warming, which is consistent with overall global temperature trend patterns as depicted in recent IPCC reports and the report of the State of Climate in Africa.

辛丑年运气方治疗皮肌炎相关间质性肺疾病所致难治性咳嗽

基于五运六气理论,从整体恒动的观念出发,分析辛丑年运用五味子汤合备化汤治疗皮肌炎相关间质性肺疾病(DM-ILD)所致难治性咳嗽的疗效。辛丑全年,岁水不及,太阴湿土司天,太阳寒水在泉,整年气化以寒湿为主。寒湿为阴邪,易伤阳气,尤伤肾阳,故辛丑年防治疾病应注重扶阳温中。五味子汤和备化汤是陈无择根据辛丑年运气特点所创的运气方,二者配伍具有温肾健脾散寒、温肺化痰滋阴之效,恰合辛丑年DMILD所致难治性咳嗽的病机特点,故辛丑年以其治疗该病具有良好疗效。

基于光学工程应用的全国陆地主要地区水平消光系数情况初步分析

从光学工程应用的角度对全国陆地主要地区水平消光系数情况进行了研究。首先从总体平均情况、冷暖半年、昼夜变化等三个方面对相关历史数据进行了分析。分析结果表明:总体上水平消光系数的呈现北低南高的分布;冷暖半年水平消光系数分布略有差别,暖半年水平消光系数低于冷半年的站点区域占较大面积;昼夜变化中白天水平消光系数要比夜间的消光系数偏小。在基于总体平均情况、冷暖半年、昼夜变化讨论基础上进而讨论了全国陆地主要地区水平消光系数的区域分级情况,发现适合光学工程应用的1级区主要分布在我国北方及西部地区。研究结果有助于了解全国适于开展光学工程应用的区域,并可为进一步研究水平消光系数对光学工程应用产生的定量影响提供参考。

Winter Arctic warming and its linkage with midlatitude atmospheric circulation and associated cold extremes: The key role of meridional potential vorticity gradient

The surface air temperature over the Eurasian continent has exhibited a significant cooling trend in recent decades(1990–2013), which has occurred simultaneously with Arctic warming and Arctic sea ice loss. While many studies demonstrated that midlatitude cold extremes are linked to Arctic warming and Arctic sea ice loss, some studies suggest that they are unrelated.The causal relationship between midlatitude cold extremes and Arctic change is uncertain, and it is thus an unsolved and difficult issue. It has been widely recognized that the severity and location of midlatitude cold extremes are closely related to the persistence, location and movement of blocking systems. It might be possible that the Arctic sea ice decline or the Arctic’s warming influences midlatitude cold extremes by changing the blocking system. This paper reviews the recent research advances on the linkages between the blocking system and Arctic warming. The nonlinear multiscale interaction model of Luo et al.revealed that the magnitude of the meridional gradient(PVy) of the background potential vorticity(PV) is a key parameter that reflects changes in the dispersion and nonlinearity of the blocking system. It was found that Arctic warming played a role in reducing the dispersion of the blocking system and enhancing its nonlinearity by reducing the magnitude of PVy. A small PVyis a favorable background condition for increasing the duration of blocking events and producing midlatitude cold extremes.However, because the magnitude of PVyreflects the difference between the background PVof the Arctic high latitudes and the midlatitude continent, the occurrence of midlatitude cold extremes not only depends on an anomalous background PVover Arctic high latitudes but also on its value over the midlatitudes. Thus, Arctic warming or sea ice decline is not necessary for the occurrence of midlatitude cold extremes.

Variations of widespread extreme cold and warm days in winter over China and their possible causes

The two leading modes of winter surface air temperature(SAT) over China during 1961–2017 are a spatially consistent pattern and a north-south dipole pattern. Based on the two leading modes, the characteristics of the extreme cold and warm days in the two patterns, defined by the standard deviation larger than 1.28 or smaller than-1.28 in the time series of the two leading modes, are analyzed. With the increase of winter SAT during 1961–2017, the number of spatially consistent extreme cold days decreased and their occurrence was restricted to late December to early January, whereas the number of spatially consistent extreme warm days increased significantly in January and February. Global warming is associated with an increase in the spatially consistent extreme warm days and a decrease in spatially consistent extreme cold days, but has little relation to the sum of extreme cold and warm days of either the spatially consistent or north-south dipole pattern. The Siberian High(SH) is the main factor controlling the sum of spatially consistent extreme warm and cold days. The strong(weak) SH before(after) the1990 s corresponds to an increase(decrease) in the sum of the spatially consistent extreme warm and cold days. The occurrences of extreme south-cold-north-warm and extreme south-warm-north-cold days are related to the north-south difference of the SH.When the center of the SH is in mid-high latitudes, the extreme south-warm-north-cold(south-cold-north-warm) days occur more(less) often. During the winters of 1961–2017, the total number of extreme cold and warm days of the north-south dipole pattern changes negligibly. The North Atlantic meridional overturning circulation(AMOC) may be the main factor affecting the sum of the extreme cold and warm days of the two types of SAT pattern in China.

温阳散寒活血法治疗下肢动脉硬化闭塞症疗效及血清hsCRP、TNF-α、IL-6的影响

目的:探讨温阳散寒活血法治疗下肢动脉硬化闭塞症(ASO)疗效及血清超敏C反应蛋白(hsCRP)、肿瘤坏死因子-α(TNF-α)、白介素-6(IL-6)的影响。方法:选取2018年1月~2020年12月河北省沧州中西医结合医院收治的180例ASO患者,根据随机数字表法分为两组,对照组(n=90)接受常规西医治疗,观察组(n=90)在常规西医治疗基础上接受自拟脉管炎Ⅰ号组方熏洗治疗。比较两组患者临床疗效和治疗14d、28d后中医证候积分、间歇性跛行距离、踝肱指数、足背动脉血流量和血清hsCRP、TNF-α、IL-6水平及不良反应发生情况。结果:观察组临床治疗总有效率明显高于对照组(P<0.05)。治疗后14d、28d观察组中医证候积分和血清hsCRP、TNF-α、IL-6水平明显低于对照组,间歇性跛行距离、踝肱指数、足背动脉血流量明显高于对照组(P<0.05)。两组患者不良反应发生率比较无差异(P>0.05)。结论:自拟脉管炎Ⅰ号组方熏洗治疗ASO疗效显著,可有效改善下肢缺血症状,延长间歇性跛行距离,调节血清hsCRP、TNF-α、IL-6水平,且安全性高,值得推广。

基于光学工程应用的全国陆地主要地区云量概况初步分析

从光学工程应用的角度对全国云量情况进行了研究,重点分析了全国陆地主要地区云量总体平均情况、冷暖半年、昼夜变化等三个方面云量历史数据,研究结果表明:全国陆地主要地区总云量和低云量分布区域基本呈北少南多的情况;冷暖半年云量分布有较明显的差别,暖半年云量高于冷半年的站点区域占全国较大面积;昼夜云量分布区别主要体现在西部地区白天低云低值区会有中高云存在。在云量总体平均情况、冷暖半年、昼夜变化的分析基础上进而讨论了全国云量区域的分级情况,结果表明适合光学工程应用的1级区主要分在北方。结果有助于了解全国适于开展光学工程应用的区域,并可为进一步研究云量对光学工程应用产生的定量影响提供参考。

1961—2021年广西沿海地区极端冷暖事件时空变化

为给红树林保护修复和气象保障服务提供科学依据,基于1961—2021年大气环流指数以及北海、防城港和钦州10个国家站逐日最高、最低气温,采用RClimDex模型计算极端气温指数,采用线性趋势分析、MK突变检验和偏相关分析,研究广西沿海地区极端冷暖事件时空变化规律。结果表明,1961—2021年,霜冻日数、持续冷期指数、冷夜日数、冷昼日数和气温日较差显著下降,热带夜数、夏季日数、持续暖期指数、暖夜日数、暖昼日数、日最高气温的最大值、日最低气温的最大值和日最低气温的最小值显著上升,说明广西红树林生态区冷、暖指数都趋于变暖,与全球变暖趋势正响应,且夜间气温的上升幅度大于白天,昼夜温差变小。冷指数突变年为1988—2015年,暖指数突变年为1996—2012年,冷、暖指数突变时间段相差不大。冷夜日数、冷昼日数、暖夜日数、暖昼日数和持续暖期指数空间分布规律一致,都是除防城港市东南部偏低外,其他地方普遍高;其中暖夜日数、暖昼日数和持续暖期指数在北海市北部地区增加趋势较明显,说明冷、暖指数在研究区的空间差异不大,在北海市北部地区变暖现象较明显。西太平洋副热带高压和欧亚纬向环流增强有利于极端气温上升。

基于ETCCDI指数2017年中国极端温度和降水特征分析

利用中国1961-2017 年2419 站均一化逐日气候数据,计算了气候变化检测和指数联合专家组定义的26 个极端气候指数,分析2017 年中国极端温度和降水特征。结果表明:2017 年中国区域平均的所有极端高温指数均高于1961-1990 年30 年平均,所有极端低温指数均低于1961-1990 年30 年平均。中国区域平均的多个极端温度指数达到或者接近历史极值,其中年最小日最高气温(TXn)和年最小日最低气温(TNn)均达到历史最高值,冷夜(TN10p)、冷昼(TX10p)和持续冷日日数(CSDI)达到历史最低值。年最大日最高气温(TXx)、年最大日最低气温(TNx)、暖夜(TN90p)、霜冻(FD)、冰冻(ID)、热夜(TR)、生长期长度(GSL)排在1961 年以来的第2 或第3 位,其余极端温度指数全部排在了1961 年以来前10 位。2017 年中国区域平均的10 个极端降水指数中,有7 个指数值处于1961-2017 年1 个标准差范围内,指示2017 年的极端降水接近正常年。

吉林省敦化市乡村人群气候变化感知的偏差及群体分异研究

通过问卷调查,具体分析了吉林省敦化市乡村人群对气候变化趋势和极端冷暖年的感知偏差及人群分异。发现乡村人群对气候变化趋势的感知与科学事实比较符合,由于对变暖转折年代更敏感,因而对变暖的确认度在一些时段与科学事实在变化程度或幅度上存在比较大的偏差。乡村人群对极端冷暖年不如对趋势感知的准确度高。经验积累影响乡村人群对气候变化趋势感知准确度,成长经历影响乡村人群对极端冷暖年感知的准确度。建议政府对气候变化教育有专门投入,在应对气候趋势的变化和极端冷暖年变化方面,总结关键人群在粮食种植行为上取得的经验和教训,以教育方式为关键人群提供分享这些案例的机会,服务于提高乡村人群适应气候变化的能力建设目标。

三江源地区极端气候事件演变事实及其成因探究

利用三江源地区14个气象台站1962—2005年逐日气温、降水资料分析了该地区冷暖干湿极端气候事件的演变规律,探讨了其变化成因。研究表明:近44a来三江源地区气温等级由冷向暖转变,极端高温事件频繁发生,而极端低温事件则逐年减少,致使气温不断向着更高的均值状态持续增暖;尽管降水量干湿变化不甚显著,但降水的极端状况即严重干旱或暴雨事件均呈减少趋势,降水量的变化趋于稳定,降水变率减小;地形对极端气温、降水事件频次变幅的空间分布均有着较为显著的影响,且对后者的影响更为显著;高原季风、厄尔尼诺事件及高原积雪等因子的年际振荡是三江源地区极端气候事件发生频次波动的主要原因。

天时、气候与中国历史(Ⅰ):太阳黑子周长与中国气候

依据太阳黑子周期长度 (SCL)资料 ,将过去 2 5 0 0年分为“好天时代”(SCL <11年 )和“坏天时代”(SCL >11年 ) ,发现在“坏天时代”中国旱灾频率显著高于“好天时代”。“好 (坏 )天世纪”与气候暖(冷 )期有好的对应 ;

中国西南地区春季异常冷暖气候的相关分析及统计预测

利用1951—2006年西南地区春季4～5月温度资料和北半球500 hPa高度及北太平洋海温资料等,通过合成分析、相关分析及关联表方法,研究了西南地区春季气温的气候变化及其与北半球500hPa高度场、热带海温场和南方涛动的联系。结果表明:西南地区春季气温具有明显的年代际气候变化特征;春季异常冷暖年份,北半球500 hPa高度距平场和热带海温距平场分布具有明显不同;前期1～3月北半球诸副热带高压体强、弱变化和前期8月～2月热带海温,尤其是前期12月～1月NINO 3区海温高低变化对西南地区春季气温具有很好的预测指示性,它们之间存在着密切的正相关关系;前期8～9月南方涛动强、弱变化对西南地区春季气温也有很好的指示意义,它们之间负相关关系密切。

石家庄近53a冬季气温变化特征

利用石家庄1955年1月至2008年4月逐日气温观测资料,分析讨论了石家庄冬季平均气温、寒冷日数、冷积温的变化特征以及冬季气温的突变和周期;研究了冬季变暖的背景下,石家庄冬季时间尺度的演变、冬季极端冷(暖)日的变化特征和严重冷(暖)冬的分布。结果表明:石家庄近53 a冬季气温明显上升,最低气温的上升对冬季增温的贡献较大,寒冷日数与冷积温均呈明显减少趋势;冬季气温在20世纪90年代发生突变,存在15 a和3 a左右的周期;近53 a冬季缩短了近4个候,主要体现在冬季结束时间的提前;冬季极端冷日日数呈显著减少趋势,极端暖日日数年际变化加大;严重冷冬均出现在20世纪80年代之前,而严重暖冬均出现在上世纪末到本世纪初。

山东省三次暖切变线极强降水的对比分析

应用加密观测、常规观测、卫星云图和雷达探测的资料及NCEO/NCAR(1°×1°)再分析资料,对由东省三次极强降水天气进行了诊断和对比分析。结果表明,,低层暖式切变线和500 hPa西风槽是三次强降水的主要影响系统。强降水前低层大气高温、高湿、对流不稳定同,有较高的对流不稳定能量。低层暖式切变线辐合和暖湿平流产生的上升运动与地面辐合线附近产生的上升运动相叠加,触发对流不稳定能量释放,产生强对流,造成强降水。较强的风垂直切变使得对流有组织地发展。强降水期间,中高层弱的干冷空气侵入,使得对流不稳定加强,中高层具有高位涡的干冷空气入侵诱发低层中尺度涡旋发展,辐合上升运动加强。低层暖湿气流螺旋式辐合上升与中高层入侵的干冷空气相遇,水汽凝结率增大,降水强度增强。中高层干冷空气侵入的时段与极强降水的时段相对应。有利的地形对局地短时极强降水有重要作用。低层暖式切变线和500 hPa低槽的位置、强弱不同,中高冷空气的强度和入侵路径不同,对流云团的发生发展、内部结构和移动方向不同,造成强降水的地理位置和强度不同。

南方极端低温雨雪冰冻过程天气学特征分析

应用常规气象观测资料和NCEP 1°×1°再分析资料,对我国1961—2008年的南方极端低温冰雪典型过程进行了天气学分析。1961—2008年我国南方极端低温冰雪过程共发生了5次;这5次南方极端低温冰雪过程主要是受西风槽和南支槽、中层低涡和切变线、西南急流、地面强冷空气共同影响造成的;多股冷空气不断南下,前沿冷锋抵达黔滇地区、低层冷垫上空暖湿气流强盛、垂直结构逆温长时期维持是南方极端低温冰雪过程的重要特征;根据环流特征的不同可分为西南气流和偏西气流两种类型,前者降水和降温基本上是同时发生,形成雨雪冰冻天气,而后者一般是先降水、后降温,且后期降温剧烈,以低温冰冻天气为主。