1955—2014年杭州极端气温和降水指数变化特征

根据杭州市1955—2014年降水量、气温逐日资料,采用国际通用的极端天气指数和线性倾向估计、M-K检验等方法,分析了杭州市近60 a极端气温和降水的变化特征。结果表明：1）杭州市近60 a的气温呈一致升高趋势,且变化显著,表现为极端高温阈值和极端低温阈值的升高及极端高温日数的增多;极端冷事件显著减少,暖事件显著增多。2）极端降水指数中只有强降水量的增加较明显,主要贡献为夏季和冬季强降水量的增强。3）冬季平均气温、极端低温阈值、霜冻日数等极端冷事件的突变发生于20世纪80年代初中期,夏季平均气温、极端高温阈值、高温日数等极端暖事件的突变发生于20世纪末21世纪初,与全国范围内的气候增暖进程基本一致。另外,降水强度、极端降水阈值等极端降水指数的突变时间在2008年左右,即2008年后气温升高和降水强度的增加突变期叠加,尤其在夏季和冬季表现更突出,可能诱发更多的异常天气。     

Interdecadal variability of the large-scale extreme hot event frequency over the middle and lower reaches of the Yangtze River basin and its related atmospheric patterns

本文研究了长江中下游夏季大范围极端高温事件的年代际变化及其与大气环流的联系。结果表明,从1960-2013年长江中下游极端高温事件呈现出多-少-多的年代际变化特征,两次显著的年代际突变分别发生在20世纪70年代初和21世纪初。欧亚大陆高层的遥相关模态与极端高温事件在年代际尺度上存在密切联系。该遥相关模态可以通过影响东亚地区上空高层西风急流的强弱,进一步影响长江中下游地区局地的辐合辐散、垂直运动和云量的变化,从而对长江中下游地区极端高温事件产生影响。利用近百年的气温和大气环流资料也表明在更长时间尺度上该欧亚大陆高层的遥相关模态与极端高温事件的关系也是显著的。     

黑龙江省1961—2009年极端气温事件变化特征分析

选用世界气象组织公布的极端气候指数方法对1961—2009年黑龙江省8个极端气温指数进行计算和分析,得到黑龙江省极端气温事件的事实和变化特征。结果表明：黑龙江省近49年来夏日天数、极端最低气温、极端最高气温、暖夜指数和暖昼日数均呈上升趋势,而霜冻日数、冷夜指数和冷昼日数呈下降趋势。极端气温指数的变化存在明显的年际变化特征,并有突变发生。对黑龙江省气温升高来说,最低气温升高主要发生在20世纪80年代中期以后,而最高气温则在90年代以后上升明显。空间分布方面,极端气温指数在全区基本都呈一致的增大或减小分布。夜间增暖的幅度要大于白天增暖的幅度,夜间气温的上升对增暖的贡献更大。     

山东省夏季高温气候变化特征分析

对比分析山东省夏季1961～1990年和1971～2000年前后30年极端最高气温和高温日数的分布和变化，得知山东省夏季高温的气候变化存在明显的地域性差异，东部地区高温有所增多，西部地区明显减少。利用统计方法分析山东省各地高温多年变化特征，发现夏季高温日数和极端最高气温均存在明显的年代际变化，且东西部变化不尽相同；在60年代末70年代初全省夏季极端最高气温发生了一次转折性变化。     

RegCM3 CORDEX东亚试验模拟和预估的中国夏季温度变化

按照CORDEX (COordinated Regional Downscaling Experiment) 计划试验设计要求,利用中国科学院大气物理研究所全球模式FGOALS-g2的数据驱动区域气候模式RegCM3,针对1986~2005年历史气候和2010~2065年RCP8.5排放情景下气候预估,对东亚地区进行了50 km动力降尺度模拟。首先评估了RegCM3模式及驱动模式FGOALS-g2对1986~2005年夏季中国地表气温和极端高温事件的模拟能力,然后比较了两个模式在RCP8.5排放情景下对中国夏季地表气温和极端高温事件预估的变化,重点分析了动力降尺度结果的优势。结果表明,两个模式均能合理再现夏季中国地表气温和极端高温事件的大尺度气候态特征。相对于全球模式,区域模式由于水平分辨率较高,能在刻画地表气温分布的细节上体现出优势。在RCP8.5排放情景下,两个模式预估的三个地表气温指标均显著升高,到21世纪中期 (2046~2065年),两个模式预估的全国平均地表气温增幅相当,气温日较差变化均较小。在FGOALS-g2模式预估中,到21世纪中期,三个地表气温指标的增幅相当,气温日较差没有明显变化,东北和青藏高原的地表气温增幅最大。在RegCM3模式预估中,到21世纪中期,中国大部分地区日最高气温 (Tmax) 增幅大于日最低气温 (Tmin) 增幅,气温日较差增加;而在青藏高原西部,Tmax的增幅较Tmin偏低,气温日较差减小。在RCP8.5排放情景下,两个模式预估的极端高温事件到21世纪中期也显著增加,RegCM3模式预估的极端高温事件全国平均增幅略高于FGOALS-g2模式的预估。在两个模式的预估中,日最高气温最大值 (TXx)、暖昼指数 (TX90p) 和持续暖期指数 (WSDI) 变化的空间分布特征与Tmax相似;和当代相比TX90p增加了60%以上,而WSDI增加了一倍以上。     

吉林省近50年气温概率分布变化特征

本文选取了吉林省10个测站的冬、夏季气温资料,采用气候统计学分析方法,探讨了吉林省冬、夏季气温的年际、年代际变化及其概率分布变化特征。结果表明,20世纪70年代末以来,吉林省的夏、冬季气温表现为两种变化特征,一是均值的显著变化;二是方差的显著变化。吉林省夏季和冬季气温均有明显的年代际变化。在不同的年代际变化阶段,气温的总体概率分布特征差异很大,这种概率分布形式的差异与高温、低温等极端天气气候事件发生的频繁与否具有密切关系。同时,冬、夏季气温变化特征还表现为平均值的增加,因此吉林省发生暖冬及夏季高温的机率增大。     

城市化对浙江省夏季极端高温事件的影响

基于夏季逐日最高气温和卫星遥感夜间灯光数据,分析了1971—2011年浙江省夏季极端高温事件的变化及其与城市化之间的联系。结果显示,过去41年浙江省绝大多数气象站点的夏季高温日数和高温度日数都呈现出增加的趋势,其中,环杭州湾城市群、温台沿海城市带和金华-义乌三大城市群地区的夏季高温日数和度日数的增加更显著;基于逐日气温95百分位数和35 ℃阈值两种高温日定义方法的研究结果相当一致,都表明由于城市热岛效应的存在,使得城市站比农村站具有更多的高温天数和更强的高温强度;进入21世纪,浙江省城市站相对于农村站的高温日数增加更显著,这与2000年以后城市化进程的加快密切相关。      

宁波城市化进程对夏季极端气温和高温热浪的影响

利用浙江省沿海宁波鄞州站(城区)、台州洪家站(郊区)和宁波石浦站(海岛)1956-2018年夏季(6-8月)逐日最高、最低气温和1978-2017年宁波城市化进程参数资料,研究城市化进程与夏季极端气温及高温热浪之间的关系。结果表明:1)宁波城区夏季的最高、最低气温的增幅分别为0.306℃/10a、0.271℃/10a,台州郊区增幅与之接近,海岛增幅最小;城区气温的突变时间均早于郊区和海岛的;热岛效应对城区的最高、最低气温变化贡献率分别为57.8%和53.5%,不仅对气温增幅占比大,而且其突变时间要早于城区及对比站气温本身的突变时间。2)宁波是高温热浪袭击较为频繁的城市,20世纪90年代开始强高温热浪较集中,21世纪以来高温热浪尤为严重;台州郊区20世纪各级高温热浪频次变化不大,但21世纪较20世纪明显增多。3)宁波城市化发展对高温热浪影响显著,城市化对高温热浪贡献率,相对于郊区站为46.1%,相对于海岛站接近100.0%。4)宁波城市化进程参数K的突变时间与城区的夏季平均最高、最低气温的突变时间一致,与高温日数、平均及极端最高气温、高温热浪频数均显著正相关,其中与平均最高气温的相关性最高。     

武汉市10个主要极端天气气候指数变化趋势分析

根据武汉市1951—2007年逐日气温、降水量计算分析了10个极端天气气候指数的变化特征。结果表明:1)4个气温指数中,年及四季高、低温阈值均为上升趋势,并造成最长热浪天数的延长和霜冻日数的减少;低温阈值升速明显快于高温阈值,高温阈值仅在春季变化显著,最长热浪天数仅在冬季变化显著;低温阈值则为极显著上升趋势,尤其是年和冬季,造成"热春"、"暖冬"频繁;暖夜、闷热、傍晚至夜间的强对流等显著增多,暖日、高温热浪增加,霜冻日大幅减少。2)6个极端降水指数以增趋势为主,其中强降水阈值、比例、日数以及最大5日降水量在冬季增趋势最明显,仅夏季强降水阈值、比例略有减小,冬季日降水强度的增大趋势、夏季持续干期的缩短趋势显著性水平分别可达0.1、0.01。3)一些气温指数在1980—1990年代发生突变,而降水指数未现突变。     

喀什市极端气温指数长期变化及突变特征分析

利用喀什市1961—2012年逐日最高、最低、平均气温资料,采用回归分析、R/S分析、Morlet小波分析及Mann-kendall突变检验等方法,分析了喀什市极端气温长期变化趋势、持续性、周期变化及突变特征。结果表明:喀什市年平均气温呈显著上升趋势,升温率高于全球及全国水平且主要变暖从20世纪90年代开始,较全国同期增温时间滞后;极端高温、夏季日数呈显著增加趋势,极端低温、霜冻日数呈减少趋势,经R/S分析,极端气温指数及年平均气温序列具有较好的连续性,未来喀什市气温保持升高,极端高温、夏季日数增加,极端低温、霜冻日数减少;喀什市极端气温指数在时间域上包含了多个尺度的周期变化,各类极端气温指数具有不同强度的周期变化特征;近52a极端高温日数在1995年发生突变,夏季日数、极端低温、霜冻日数的突变均发生在2001年左右。     

Changes in daily climate extremes in the arid area of northwestern China

There has been a paucity of information on trends in daily climate and climate extremes, especially for the arid region. We analyzed the changes in the indices of climate extremes, on the basis of daily maximum and minimum air temperature and precipitation at 59 meteorological stations in the arid region of northwest China over the period 1960–2003. Twelve indices of extreme temperature and six indices of extreme precipitation are examined. Temperature extremes show a warming trend with a large proportion of stations having statistically significant trends for all temperature indices. The regional occurrence of extreme cool days and nights has decreased by ?0.93 and ?2.36 days/decade, respectively. Over the same period, the occurrence of extreme warm days and nights has increased by 1.25 and 2.10 days/decade, respectively. The number of frost days and ice days shows a statistically significant decrease at the rate of ?3.24 and ?2.75 days/decade, respectively. The extreme temperature indices also show the increasing trend, with larger values for the index describing variations in the lowest minimum temperature. The trends of Min Tmin (Tmax) and Max Tmin (Tmax) are 0.85 (0.61) and 0.32 (0.17)?°C/decade. Most precipitation indices exhibit increasing trends across the region. On average, regional maximum 1-day precipitation, annual total wet-day precipitation, and number of heavy precipitation days and very wet days show insignificant increases. Insignificant decreasing trends are also found for consecutive dry days. The rank-sum statistic value of most temperature indices exhibits consistent or statistically significant trends across the region. The regional medians after 1986 of Min Tmin (Tmax), Max Tmin (Tmax), warm days (nights), and warm spell duration indicator show statistically more larger than medians before 1986, but the frost days, ice days, cool days (nights), and diurnal temperature range reversed. The medians of precipitation indices show insignificant change except for consecutive dry days before and after 1986.     

Trends in extreme temperature indices in Huang-Huai-Hai River Basin of China during 1961–2014

Spatial and temporal characteristics of temperature extremes have been investigated in Huang-Huai-Hai (HHH) region based on the daily series of temperature observations from 162 meteorological stations. A total of 11 indices were used to assess the changes of temperature pattern. Linear trend analyses revealed that the daily maximum temperature (TXx) increased at α = 0.05 level with a magnitude of 0.15 °C per decade on the regional scale during the period of 1961–2014. More pronounced warming trend of the daily minimum temperature (TNn) was detected at a rate of 0.49 °C per decade (α = 0.01 level). Consequently, a decreasing trend of the temperature range of TXx and TNn (extreme temperature range) was observed. The frequency of hot days (TXf90) and annual average of warm events (warm spell duration indicator, WSDI) showed significant increasing trends, while that of cold nights (TNf10) and cold events (cold spell duration indicator, CSDI) showed opposite behaviors. Both warm winter (W-W) and hot summer (H-S) series displayed significant increasing trends at α = 0.01 confidence level. The cold winter (C-W) series showed a decreasing trend at α = 0.01 confidence level, while the cool summer (C-S) series showed a nonsignificant decreasing trend that is not passing the 90% confidence level (α = 0.1). Abrupt increments of warm­related extremes (TXx, TXf90, WSDI) have been detected since 1990s, and a steadily decreasing trend of cold related extremes (TNf10, CSDI) was found since 1970s. Ten hot summers out of 11 and nine warm winters out of 10 occurred after 1990s. Altitude has a large impact on spatial pattern of extreme temperature indices, and the urban heat island effect also has an impact on amplitude of variation in extreme temperature. Trend magnitudes are significantly larger at sites with high altitudes for warm­related indices (TXx, TXf90, WSDI), while those involving cold-related indices (TNn, TNf10) are remarkably larger for stations with low altitudes.     

近40年我国极端温度变化趋势和季节特征

利用1961—2000年我国194个测站逐日最高温度和最低温度器测资料,结合具有实际意义的季节极端温度指数,分析了我国近40年极端温度事件的年变化趋势和季节特征。对年极端气候指数的研究表明:绝对阈值定义的冷暖指数由于无法考虑南北气候差异,其结果不理想。百分比阈值所得的冷暖指数中,冷日指数和暖日指数具有不对称性,冷夜指数和暖夜指数具有较强的对称性。对季节极端温度指数研究表明:冬季极端冷指数变化趋势最为明显,夏季极端暖指数的变化趋势次之,春、秋两季极端冷指数的变化趋势不明显;年和季节尺度的极端冷暖指数均反映出增暖趋势。     

1961~2014年中国冬季极端低温变化特征分析

利用中国691个无缺测站点的经均一化处理及质量控制的逐日最高、最低气温资料,基于冷昼日数、冷夜日数、霜冻日数、冰冻日数、月最低气温极大值以及月最低气温极小值等6个由世界气象组织定义的极端气温指数,分析了1961~2014年中国冬季的极端低温变化特征。结果表明:冷昼日数、冷夜日数、霜冻日数以及冰冻日数在全国大部分地区均呈现下降的趋势,下降趋势较为明显的区域集中在东北南部、华北、西北东部、华东、华中、西南及高原地区,全国整体上下降幅度分别为-0.9 d/10 a、-1.7 d/10 a、-1.5 d/10a和-1.4 d/10 a。最低气温极大值和最低气温极小值在全国范围内则主要呈现上升的趋势,全国整体上分别为0.4℃/10 a和0.6℃/10 a;极端低温天数在20世纪60年代至70年代中后期呈现波动状,随后自20世纪70年代末80年代初至21世纪初呈明显下降趋势,从2006年左右以后其下降趋势较之前有所减缓,是对全球变暖减缓背景下的气候响应;与其他时间段相比,20世纪60年代至70年代为冬季极端低温事件较为频发的时间段,这可能与该时段陆地冷高压频繁活动有关。     

土壤湿度年际变化对中国区域极端气候事件模拟的影响研究Ⅱ.敏感性试验分析

利用NCARCAM3.1大气环流模式,设计了有、无土壤湿度年际异常的两组数值试验,探讨了土壤湿度年际异常对极端气候事件模拟的可能影响。结果表明,模式模拟的极端气候事件对土壤湿度异常十分敏感,土壤湿度异常对极端气候指标的多年平均空间分布、年际变率以及年际变化均具有重要影响。当不考虑土壤湿度的年际异常时:(1)模拟的暖夜日数、暖昼日数和热浪持续指数的发生频次在全国范围内均明显减少,而霜冻日数则明显增加。极端降水指标的响应表现出明显的空间差异,极端降水频次在江淮流域明显减小,而极端降水强度则表现为东北减弱、长江流域增强;中雨日数和持续湿期在我国大部分地区减少。(2)极端气温指标的年际变率在我国大部分地区呈减小趋势;而极端降水事件的变化则较为复杂,极端降水频次和极端降水强度的年际变率在长江以南有所增强,而北方地区则有所减弱。中雨日数和持续湿期的年际变率在我国呈现出较为一致的减少趋势。(3)模式对暖夜日数、霜冻日数的年际变化的模拟能力明显下降,并对4个极端降水指标的年际变化的模拟能力在全国多数区域均有不同程度的下降。     

我国东部三市夏季高温气候特征及原因分析

利用1961-2000年夏季（6～8月）月高温资料,探讨了石家庄、南京、福州的高温气候特征,给出了高温天气过程原因分析及东亚副热带高压（下称东亚副高）的活动特点。结果表明,石家庄测站强高温过程期间干热和闷热天气持续时间不长,极端气温高,日平均风速小,日平均相对湿度小;南京和福州测站强高温过程期间闷热天气持续时间长,极端气温不高,日平均风速小,日平均相对湿度大。我国东部地区近40年来夏季月平均日照时数在减少。东亚副高和大陆变性高压是造成我国东部地区城市夏季危害性高温的主要影响系统,强盛并持续副高和大陆变性高压控制是我国东部地区高温日数和强高温过程偏多的主要原因。     

Trends of Temperature Extremes in China and its Relationship with Global temperature anomalies Relationship with Global Temperature Anomalies

Changes of temperature extremes over China were evaluated using daily maximum and minimum temperature data from 591 stations for the period 1961--2002. A set of indices of warm extremes, cold extremes and daily temperature range (DTR) extremes was studied with a focus on trends. The results showed that the frequency of warm extremes (F_WE) increased obviously in most parts of China, and the intensity of warm extremes (I_WE) increased significantly in northern China. The opposite distribution was found in the frequency and intensity of cold extremes. The frequency of high DTR extremes was relatively uniform with that of intensity: an obvious increasing trend was located over western China and the east coast, while significant decreases occurred in central, southeastern and northeastern China; the opposite distribution was found for low DTR extreme days. Seasonal trends illustrated that both F_WE and I_WE showed significant increasing trends, especially over northeastern China and along the Yangtze Valley basin in spring and winter. A correlation technique was used to link extreme temperature anomalies over China with global temperature anomalies. Three key regions were identified, as follows: northeastern China and its coastal areas, the high-latitude regions above 40^oN, and southwestern China and the equatorial eastern Pacific.     

Changes in Mean and Extreme Temperature and Precipitation over the Arid Region of Northwestern China:Observation and Projection

This paper reports a comprehensive study on the observed and projected spatiotemporal changes in mean and extreme climate over the arid region of northwestern China, based on gridded observation data and CMIP5 simulations under the RCP4.5 and RCP8.5 scenarios. The observational results reveal an increase in annual mean temperature since 1961, largely attributable to the increase in minimum temperature. The annual mean precipitation also exhibits a significant increasing tendency. The precipitation amount in the most recent decade was greater than in any preceding decade since 1961. Seasonally,the greatest increase in temperature and precipitation appears in winter and in summer, respectively. Widespread significant changes in temperature-related extremes are consistent with warming, with decreases in cold extremes and increases in warm extremes. The warming of the coldest night is greater than that of the warmest day, and changes in cold and warm nights are more evident than for cold and warm days. Extreme precipitation and wet days exhibit an increasing trend, and the maximum number of consecutive dry days shows a tendency toward shorter duration. Multi-model ensemble mean projections indicate an overall continual increase in temperature and precipitation during the 21 st century. Decreases in cold extremes, increases in warm extremes, intensification of extreme precipitation, increases in wet days, and decreases in consecutive dry days, are expected under both emissions scenarios, with larger changes corresponding to stronger radiative forcing.     

Assessment of indices of temperature extremes simulated by multiple CMIP5 models over China

Given that climate extremes in China might have serious regional and global consequences, an increasing number of studies are examining temperature extremes in China using the Coupled Model Intercomparison Project Phase 5 (CMIP5) models. This paper investigates recent changes in temperature extremes in China using 25 state-of-the-art global climate models participating in CMIP5. Thirteen indices that represent extreme temperature events were chosen and derived by daily maximum and minimum temperatures, including those representing the intensity (absolute indices and threshold indices), duration (duration indices), and frequency (percentile indices) of extreme temperature. The overall performance of each model is summarized by a "portrait" diagram based on relative root-mean-square error, which is the RMSE relative to the median RMSE of all models, revealing the multi-model ensemble simulation to be better than individual model for most indices. Compared with observations, the models are able to capture the main features of the spatial distribution of extreme temperature during 1986-2005. Overall, the CMIP5 models are able to depict the observed indices well, and the spatial structure of the ensemble result is better for threshold indices than frequency indices. The spread amongst the CMIP5 models in different subregions for intensity indices is small and the median CMIP5 is close to observations; however, for the duration and frequency indices there can be wide disagreement regarding the change between models and observations in some regions. The model ensemble also performs well in reproducing the observational trend of temperature extremes. All absolute indices increase over China during 1961-2005.     

Recent trends in winter temperature extremes in eastern China and their relationship with the Arctic Oscillation and ENSO

Interannual variations in the number of winter extreme warm and cold days over eastern China （EC） and their relationship with the Arctic Oscillation （AO） and E1 Nifio-Southern Oscillation （ENSO） were investigated using an updated temperature dataset comprising 542 Chinese stations during the period 1961- 2011. Results showed that the number of winter extreme warm （cold） days across EC experienced a significant increase （decrease） around the mid-1980s, which could be attributed to interdecadal variation of the East Asian Winter Monsoon （EAWM）. Probability distribution functions （PDFs） of winter temperature extremes in different phases of the AO and ENSO were estimated based on Generalized Extreme Value Distribution theory. Correlation analysis and the PDF technique consistently demonstrated that interannual variation of winter extreme cold days in the northern part of EC （NEC） is closely linked to the AO, while it is most strongly related to the ENSO in the southern part （SEC）. However, the number of winter extreme warm days across EC has little correlation with both AO and ENSO. Furthermore, results indicated that, whether before or after the mid-1980s shift, a significant connection existed between winter extreme cold days in NEC and the AO. However, a significant connection between winter extreme cold days in SEC and the ENSO was only found after the mid-1980s shift. These results highlight the different roles of the AO and ENSO in influencing winter temperature extremes in different parts of EC and in different periods, thus providing important clues for improving short-term climate prediction for winter temperature extremes.