亚澳季风区内水汽汇的准两年振荡及其与大气环流的关系

利用1950-2000年大气视水汽汇资料,分析了亚澳季风区内水汽汇准两年振荡的变化特征及其与大气环流的关系.亚澳季风区内水汽汇有显著的准两年振荡,其关键区位于西太平洋暖池、孟加拉湾、东南印度洋和西南印度洋,它们对应3种遥相关型.当暖池水汽汇偏强时,我国华南为偏北风距平,东亚季风区水汽汇偏弱;印度洋水汽汇距平呈现为偶极子分布,东南印度洋附近水汽汇偏强时,东南印度洋至赤道西印度洋为偏西风距平,赤道西印度洋水汽汇偏弱;孟加拉湾水汽汇偏强时,孟加拉湾至西南印度洋为偏南风距平,西南印度洋的水汽汇偏弱.反之亦然.     

华南春旱特征及其与水汽输送的关系

利用1979-2005年华南47个基准站降水资料及由NCAR/NCEP II再分析资料计算所得的水汽输送通量资料,对华南春季降水特征及其与水汽输送的关系进行研究,结果表明:华南春季降水可以110.5°E为界划分为两个区域,以东区域为华南I区,以西区域为华南II区。I区降水具有显著的下降趋势,即干旱趋势显著;而II区降水下降趋势要弱得多,未超过信度检验。此外,I区降水在1994年发生突变,由多雨期突然跃变到干旱期。华南春季水汽主要来源于南海和西太平洋,并经中南半岛转向输送到华南,当南海中北部的偏南水汽输送偏弱(强)时,I区降水偏少(多),I区偏旱(涝),当南海西南部-中南半岛南部的偏南水汽输送偏弱(强)时,II区降水偏少(多),II区偏旱(涝)。     

1960―2020年淮河流域高温热浪时空变化特征

利用1960―2020年淮河流域40个气象站逐日最高气温资料，采用线性回归和Morlet小波分析等方法，统计分析了淮河流域高温热浪频次、持续时间和有效积温的时空变化特征.结果表明：近61年淮河流域共发生了3 444次高温热浪事件，其中轻度热浪64.26%，中度热浪22.68%，重度热浪13.06%.淮河流域高温热浪年均发生56.46次，年平均持续时间为6.79 d，年平均有效积温为11.04℃.近61年来淮河流域各等级高温热浪具有显著的阶段性特征，20世纪60年代高温热浪最多最强、80年代中期以前呈减少（弱）趋势，此后呈增多（强）趋势. 61年来淮河流域高温热浪主周期变化为20 a，次周期为27 a和9 a.高温热浪频次、持续时间和强度的空间分布特征相近，呈西多（强）东少（弱）趋势，流域西南部形成高值中心，东北部为低值中心.从变化趋势来看，流域西部热浪频次、持续时间和强度呈减少（弱）趋势、东部呈增多（强）趋势.     

亚洲-太平洋涛动与华南后汛期降水的联系机制

采用1961—2015年NCEP/NCAR再分析资料和华南地区降水资料,分析了7—9月亚洲-太平洋涛动(APO)与热带西太平洋环流系统以及垂直运动、水汽输送等条件的关系,探讨了其与华南7—9月汛期强度的联系机制.研究表明:(1)7—9月APO强度的年际变化与同期华南降水雨强存在显著负相关,即APO偏强(弱)年华南汛期少(多)雨.(2)在APO偏强(弱)年,副高偏北偏东(偏南偏西),副高南侧偏东气流减弱(加强),不(有)利于热带气旋西行影响华南,华南易少(多)雨.(3)在APO偏强(弱)年,东亚副热带夏季风偏强(弱),冷空气偏北偏弱(偏南偏强),不(有)利于华南及近海的热带气旋发展,华南易少(多)雨.(4)在APO偏强(弱)年,热带西太平洋纬向风垂直切变明显增大(减小),垂直上升运动减弱(加强),不(有)利于热带气旋的生成,且热带西太平洋水汽条件易使得热带气旋偏北偏东(偏南偏西)生成,华南易少(多)受热带气旋影响和少(多)雨.     

气候变暖背景下降水变化对中国铁路安全运营秩序的影响

通过分析气候变暖背景下中国降水量的时空分布变化、降水强度等级分布的变化以及铁路降水警戒风险时数变化等，研究了气候变暖背景下降水变化对中国铁路安全运营秩序的影响。研究发现：（1）近5年，江南南部和华南等地年降水量显著减少；西北地区东部和西南地区东北部至江淮和黄淮等地降水量显著增加。年降水量最高的中国铁路广州、南昌和南宁集团有限公司（简称路局）辖区，年降水量呈减少趋势变化；郑州、济南和西安路局年降水量呈增加趋势变化。东亚夏季风增强，副热带高压偏北是降水量变化的主要原因。（2）全国降水强度变化分布不均，其中沈阳路局降水强度增强最显著，南宁路局降水强度减弱最显著。降水强度变化主要与台风和短时强降水的变化有关。（3）从降水强度等级分布看，近5年，乌鲁木齐和兰州路局等西北地区路局的较大降水强度的出现频率有所减少；南昌和成都路局等西南至江南地区路局的较大降水强度的出现频率有所增多。（4）广东和海南、西南地区东部、华北东北部至东北东南部是铁路降水出巡风险时数最多的3个高值区；限速风险时数的高值区位于西南地区东部；封锁风险时数的高值区范围进一步缩小。综合来看，在气候变暖的背景下，中国江南南部和华南等地的...     

格尔木太阳辐射与气温的多年变化

利用格尔木１９５６～１９９４年的气温和太阳总辐射资料，分析了该地区太阳总辐射和气温的多年变化特征及其相关关系。结果表明：３０多年中该地区太阳总辐射没有明显的减少趋势；年平均气温６０年代为低值，７０年代迅速上升，比东部平原地区提前，且呈现“冬暧夏凉”的变化趋势；７０年代至９０年代年平均气温与太阳总辐射呈现滞后一年的正相关；夏季气温与同期太阳总辐射有很好的正相关，但冬季的气温变化则与太阳总辐射呈负相关     

近48年华南日照时数的变化特征

 利用1961-2008年华南110个测站年日照时数资料,通过线性趋势分析、Mann-Kendall检验、功率谱分析和计算趋势系数等统计诊断方法,分析了华南年日照时数的时空特征和气候变化。结果表明：近48 a来,华南年平均日照时数整体上呈自南向北减少的分布特点,最高中心位于广西南宁（2 552 h）,最低中心在广西金秀（1 172 h）。华南平均年日照时数以4.09 h/a的速率明显减少,高于全国平均值,并存在22 a和11 a的显著周期振荡,在1970年代后期发生突变。华南年日照时数长期趋势变化有明显的空间差异,大部分地区呈明显减少的趋势,其中有3个减少中心,分别位于广东深圳（-12.86 h/a）,海南澄迈（-12.85 h/a）和广西横县（-11.85 h/a）。华南年平均日照时数的分布与总云量分布几乎完全相同,但它们的变化趋势大部分相反。广东大部分地区总云量在明显增加,日照时数在显著减少。     

2003年东亚夏季风活动的特点

利用2003年国家气象中心提供的再分析资料以及台站降水资料，诊断分析了2003我国东部地区汛期降水和东亚夏季风的活动特点，并对二者之间的联系进行讨论。结果表明：(1)2003年南海夏季风于5月第5候在南海南部建立。6月第1候全面爆发，比常年偏晚，南海夏季风强度也比常年偏弱；(2)该年夏季，副热带高压的一个显著特点是强度强、位置偏西，其中从6月下旬至7月中旬，副热带高压的位置稳定少变，其北脊线位25oN附近，且副高位置偏西，这导致了长江以南的犬部分地区高温少雨。这个阶段副热带高压西侧的南风气流将南海地区的水汽源源不断地输送到淮河流域，是淮河流域强降水过程水汽主要来源。     

黄河流域中上游水分收支以及再分析资料可用性分析

首先以实测资料为准定量计算了黄河流域中上游水分收支各分量，包括降水、径流、蒸发、水汽辐合等，分析其季节循环、年际变化以及线性趋势变化. 结果表明，多年平均该区域是水汽汇区，主要来自天气过程造成的瞬变波辐合，蒸发所占比例远大于径流和水汽辐合，对流域水分循环至关重要；各要素季节变化和年际变化很大，20世纪70年代后降水和蒸发的年际变化幅度明显减小；1958年以来，降水显著减少，天然径流和蒸发也有所减少，但不显著. 然后同ECMWF及NCEP/NCAR再分析资料作进一步对比分析，以检验两套再分析资料对黄河流域中上游水分循环的描述能力，在论证了其适用性的同时，指出其局限性，从而为使用再分析资料进行该区域水分收支分析提供参照.     

淮河源浅层地温时空变化及其对全球增暖停滞的响应

利用1961—2017年淮河源地区10个气象站的逐月平均气温和逐月平均0～20 cm地温资料，采用线性回归、功率谱分析等方法，分析了近57年淮河源地区0～20 cm地温的时空变化特征及其对全球增暖停滞的响应。结果表明：(1)1961—2017年淮河源地区0～20 cm各层年平均地温均呈波动上升趋势；(2)淮河源0～20 cm年均地温均呈东部和西南部高、北部和西北部低的空间格局，西南部各层地温变化速率最大，中部地区变化速率最小；(3)淮河源各层年均地温变化均检测出2.29 a的周期信号，信阳、息县、新县、淮滨和商城周期信号较强，其余站点各层年均地温无明显的周期信号；(4)1998—2012年淮河源各层地温对全球增暖停滞的响应极为敏感。     

The spatial distribution of forest carbon sinks and sources in China

Forest ecosystems play an important role in the global carbon cycle.The implementation of the United Nations Framework Convention on Climate Change(UNFCCC) and the Kyoto Protocol has made the study of forest ecosystem carbon cycling a hot topic of scientific research globally.This paper utilized Chinese national forest inventory data sets(for the periods 1984-1988 and 1999-2003),the vegetation map of China(1:1000000),and the spatially explicit net primary productivity(NPP) data sets derived with the remote sensing-based light use efficiency model(CASA model).We quantitatively estimated the spatial distribution of carbon sinks and sources of forest vegetation(with a resolution of 1 km) using the spatial downscaling technique.During the period 1984 to 2003 the forest vegetation in China represented a carbon sink.The total storage of carbon increased by 0.77 PgC,with a mean of 51.0TgCa 1.The total carbon sink was 0.88PgC and carbon source was 0.11 PgC during the study period.The carbon sink and carbon source of forest vegetation in China showed a clear spatial distribution pattern.Carbon sinks were mainly located in subtropical and temperate regions,with the highest values in Hainan Province,Hengduan mountain ranges,Changbai mountain ranges in Jilin,and south and northwest of the Da Hinggan Mountains;carbon sources were mainly distributed from the northeast to southwestern areas in China,with the highest values mainly concentrated in southern Yunnan Province,central Sichuan Basin,and northern Da Hinggan Mountains.Increase in NPP was strongly correlated with carbon sink strength.The regression model showed that more than 80% of the variation in the modeled carbon sinks in Northeast,Northern,Northwest and Southern China were explained by the variation in NPP increase.There was a strong relationship between carbon sink strength and forest stand age.     

Interdecadal change of summer precipitation over Eastern China around the late-1990s and associated circulation anomalies, internal dynamical causes

Observational study indicated that the summer precipitation over Eastern China experienced a notable interdecadal change around the late-1990s. Accompanying this interdecadal change, the dominant mode of anomalous precipitation switched from a meridional triple pattern to a dipole pattern, showing a "south-flood-north-drought" structure (with the exception of the Yangtze River Valley). This interdecadal change of summer precipitation over Eastern China was associated with circulation anomalies in the middle/upper troposphere over East Asia, such as changes in winds and corresponding divergence, vertical motion and moisture transportation (divergence), which all exhibit remarkable meridional dipole structures. Furthermore, on the internal dynamic and thermodynamic aspects, the present study investigated the influence of the midtroposphere zonal and meridional flow changes over East Asia on the interdecadal change around the late-1990s. Results suggested that, during 1999-2010, the East Asia subtropical westerly jet weakened and shifted poleward, forming a meridional dipole feature in anomalous zonal flow. This anomalous zonal flow, on one hand, induced changes in three teleconnection patterns over the Eurasian continent, namely the "Silk Road" pattern along the subtropical upper troposphere westerly jet, the East Asia/Pacific (EAP) pattern along the East Asian coast, and the Eurasia (EU) pattern along the polar jet; on the other hand, it brought about cold advection over Northern China, and warm advection over Southern China in the mid-troposphere. Through these two ways, the changes in the zonal flow induced descent over Northern China and ascent over Southern China, which resulted in the anomalous "south-flood-north-drought" feature of the summer precipitation over Eastern China during 1999-2010.     

中国汛期月降水量距平场的时空综合分析

本文应用时空综合的经验正交函数分析方法，对１９５１～１９８４年中国１６０个站点的月降水量距平场进行展开，得到了能够反映我国汛期（４～９月）各月降水量距平场时空变化的特征向量场时间系数，分析结果表明，我国汛期月降水异常存在着几种典型的空间分布型并具有明显的季节变化规律和年际演变特点。     

长江中下游梅雨期热量和水汽收支研究

分别计算热量和水汽收支方程,得出1991年长江中下游梅雨期(5月18日至7月13日)降水区内面积平均的视热源Q_1和视水汽汇Q_2高度时间剖面图,由该图的垂直分布特征,可以看出梅雨期可分为三个降水时段,每个时段加热的强度和垂直分布形式互不相同,其中第三时段明显呈现典型对流性降水性质。其次对收支方程垂直积分,得出105—122°E,24—40°N区域第三时段内Q_1和Q_2高度-时间积分的水平分布图,两者水平分布形式比较一致,且与实际降水量分布较为吻合,说明加热场主要由凝结加热过程所致,同时也证实上述Q_1和Q_2的计算结果是可靠的。     

Interannual precipitation variations in the mid-latitude Asia and their association with large-scale atmospheric circulation

This study analyzed the spatial differences of the precipitation variations in the mid-latitude Asia and their possible physical mechanisms during 1960–2009. The annual precipitation showed an opposite variations between the westerlies-dominated arid Central Asia (ACA) and monsoon-dominated North China (NC) during the study period. Given the different contributions of seasonal precipitation to annual total precipitation in ACA and NC, the atmospheric circulation anomalies during the major precipitation seasons (winter in ACA/summer in NC) were analyzed. In winter, negative North Atlantic Oscillation may cause negative height anomalies over the north side and positive anomalies over the south side of the ACA. Together, the enhanced pressure gradient and anomalous westerly wind brings more water vapor to ACA, and leaves less precipitation in NC. In summer, the low-pressure anomalies in Northeast China, along with a weaker summer monsoon and negative height anomalies in Eastern Europe together contribute to reduced (excessive) summer precipitation in NC (ACA). The interactions between ENSO and NAO may result in the opposite precipitation variations between ACA and NC. A significant 2–3-year cycle is identified in ACA, which is linked to the variations of westerly circulation in the middle troposphere.     

Changes of climate extremes of temperature and precipitation in summer in eastern China associated with changes in atmospheric circulation in East Asia during 1960–2008

Climate extremes and changes in eastern China are closely related to variations of the East Asian summer monsoon and corresponding atmospheric circulations.The relationship between frequencies of temperature and precipitation extremes in China during the last half century is investigated using Singular Value Decomposition analysis.During 1980-1996,there was a typical pattern with fewer hot days and more precipitation extremes in the northern part of eastern China,and more hot days and fewer precipitation extremes in the southern part.This geographic pattern tended to reverse after 1997,with fewer hot days and more extreme precipitation days south of the Yangtze River and vice versa to the north.Differences in atmospheric circulation between the former and latter periods are presented.We conclude that a mid-level anomalous high/low,upper-level anomalous easterlies/westerlies over the north/south of eastern China,a weakened East Asian summer monsoon and associated upper-tropospheric center of cooling(30°N,110°E) are all favorable for the changes in frequencies of temperature and precipitation extremes.     

老哈河流域水文要素变化研究

对老哈河流域近50a的水文要素进行了年际变化、年代际变化和线性变化趋势的研究,结果表明:(a)年降雨量的年际变化幅度最均匀、离散度最小,而年径流深和年径流系数的年际变化不均匀、离散度大.降雨量是影响径流的主要因素,但并不是唯一因素,在某些年份径流还受到其他因素的强烈干扰.另外,年径流深不仅受年降雨总量的影响,也受降雨的年内时空分布的影响.(b)从20世纪60年代到21世纪初,各要素的年代际变化不一致:年降雨量变化为少-多-少-多-少,年径流深和年径流系数变化为多-少-少-多-少.年降雨量年代际距平变化最小,变化幅度较平缓,而年径流深和年径流系数的年代际变化都比年降雨量的年代际变化大得多.(c)降雨量没有明显的增减变化,而径流却具有显著的减少趋势,其中年径流深通过了95%的置信度检验,年径流系数通过了99%的置信度检验.分析结果表明,径流的变化除了受降雨量的影响之外,还可能受气温变化和人类活动等其他因素的影响.     

Large-scale atmospheric singularities and summer long-cycle droughts-floods abrupt alternation in the middle and lower reaches of the Yangtze River

The summer droughts and floods in the middle and lower reaches of the Yangtze River valley (MLYRV) have often been one of the basic contents of the pre- cipitation forecasting during the flooding period in China. Lots of studies suggest that summer rainfa…     

4—9月西江洪水过程水汽汇与江水流量的关系

分析了１９８０￣１９８６年４￣９月西江流域洪水过程的大气水汽汇特征及其与西江高要站水流量的关系。结果表明，洪水过程的前期大气一般连续存在较强水汽汇，时间为７￣１０多ｄ，洪水的发生是各子流域强水汽汇连续产生的径流的积累所致；用水汽汇能较好地估算和预报高要站洪水期的水流量，为洪水的预报提供一种新思路。     

Some evidence of drying trend over northern China from 1951 to 2004

The surface wetness index, Palmer drought sererity index and the retrieval of soil moisture over China were calculated using monthly precipitation and monthly mean surface air temperature. Based on the contrast analysis of the variation of the above three indices and precipitation, the dry/wet spatio-temporal pattern of northern China in the last 54 years was revealed, and the evidence of drying trend over northern China was analyzed, especially. The results show the following four facts: (1) The drying trend is the main characteristic of the eastern part of Northwest China and the central part of North China since the 1980s and it was enhanced in the last 15 years mainly due to the precipitation decrease and the temperature increase; (2) During the last 54 years, there was only one dry/wet shift at the interdecadal scale occurring in the eastern part of Northwest China and the central part of North China in the late 1970s, which was related to 1977/1978 global abrupt change, whereas there were three shifts in Northeast China, one was in the mid 1990s and the other two were in 1965 and 1983, respectively; (3) Unlike the variation trend of other subregions of northern China, the western part of Northwest China is currently located in a relatively wetting period, which is weak-ened due to the temperature increase; (4) The extreme drought frequency is obviously increasing in the eastern part of Northwest China, the central part of North China and Northeast China since the 1980s, which is closely related to the precipitation decrease and temperature increase in these subregions.