城市化进程对南京市气温变化影响的主成分分析

为揭示城市环境气象的蠕变过程,利用南京站1956—2007年逐日气温资料及南京市1995—2006年的统计年鉴数据,通过主成分分析法,研究了南京市年平均气温变化与城市化进程之间的关系。结果表明:(1)1956年以来南京市年平均气温、年平均最高、最低气温总体呈上升趋势,增温率分别为0.28℃/(10 a)、0.18℃/(10 a)、0.33℃/(10 a),特别是1990年以后,增温速率进一步加大。(2)城市化进程中影响气温变化的主导因子为:城市下垫面性质、工业排污和人口数量。(3)1990年代后南京市城市化进程与年平均气温和年平均最低气温之间存在显著的正相关关系。     

吴川气象观测站环境变化对气象观测资料的影响

通过对吴川市1963～2004年的气温、相对湿度、蒸发量等观测资料的变化显著原因分析,说明了吴川城市化进程造成了气象站观测环境的变化,影响了气象观测资料的"三性".     

上海地区城市化速度与降水空间分布变化的关系研究

采用1960-2007年上海地区11个站的逐日降水资料,基于空间标准化相对降水量,研究上海城市化进程不同阶段的降水空间分布变化.结果表明,伴随城郊城市化进程差异的显著加快,上海年降水量的空间差异增大.城市化进程的快速增长期,年降水量和暴雨以上的强降水日数呈现出明显的城市雨岛分布特征;在城市化进程的缓慢增长期,该特征则不...     

城市化对宁波地区极端气温及人体舒适度的影响

利用浙江省沿海宁波市鄞州站(城区)和石浦站(海岛)1956—2018年逐日最高气温、最低气温、相对湿度和风速资料,结合宁波1978—2017年城市化进程参数,研究城市化进程对人体舒适度气象指数(BCMI)及相关气象要素的影响。结果表明:(1)宁波沿海城市城区和海岛年平均最高气温、最低气温均呈增高趋势,城市化进程对城区最高气温、最低气温增幅的贡献率分别为32.3%、48.8%;(2)城市化导致城区年平均相对湿度呈减小趋势,海岛站相对湿度变化不明显;(3)城区和海岛年平均风速均呈减小趋势,城区风速突变年份相对更早,但风速的减小主要是气候自然变化所致,与城市化进程关系不大;(4)气温对人体舒适度指数BCMI的影响最大,城区夏季和冬季极端气温下的BCMI均表现出增大趋势,夏季往炎热不舒适方向发展,冬季则往舒适方向发展;(5)宁波城市化进程参数K与城区BCMI表现出明显的正相关性,城市化进程对城区夏季最高气温和冬季最低气温增幅的贡献率分别为57.8%和46.1%。     

城市化发展对南京城市增温的影响分析

利用层次分析法和非线性拟合法,分析了南京市1980—2006年城市化进程,并选取了年平均最高、最低气温和年平均气温为研究对象,分别探讨了城市化与城市化增温的影响关系。在此基础上,建立了城市化效应与温度变化的线性模型,进一步分析了城市化效应对城市增温的影响程度。结果表明,1980—2006年南京城市化进程对城市化增温影响关系显著,城市化与增温呈显著相关;城市化对年平均最低气温的影响最为明显,对年平均气温的影响次之,对年平均最高气温的影响最小;1981—1998年城市化效应对城市增温的影响远远小于区域气候的影响,但1998—2006年前者的影响程度大于后者,增温率将近为后者的2倍。这说明,近年来南京市人类活动造成的温度变化已超过自然因素造成的变化,城市化增温趋势呈现出的阶段性特征与南京市城市化进程的特点相吻合。     

城市化进程对重庆都市圈降水空间分布的影响

利用重庆17站逐日气象观测资料、重庆统计数据,采用降水量空间标准化方法,研究了城市化进程不同阶段对重庆都市圈降水空间分布的影响.结果表明;重庆城市化进程能够以1997年为界限被划分为城市化缓慢发展阶段和快速发展阶段,都市圈年降水量变化的空间差异与城市化进程的速度有关.比较两个阶段的差值,发现随着城市化进程的加快,核心都市圈年降水量、降水强度、中雨和暴雨日数都有所增加,呈明显的“城市雨岛”特征.从季节差异来看,夏季降水以主城区及其北侧郊区降水增加,冬季降水以主城区及其南侧郊区增加为主,可能是因为城乡温度梯度与环境风场相互作用,导致不同季节降水分布的区域差异,使得主城区及其下风方向降水增加,且以下风区增加最为显著.     

青藏高原雪盖变化对我国气候的影响

青藏高原雪盖是影响我国气候的一个重要因子,除了具有明显的季节变化之外,还有明显的年际变化和年代际变化．它通过改变高原的热力作用而影响东亚季风进程、大气环流以及我国的气温和降水．雪盖具有较为明显的持续性,且具有振幅变化大的特点,人们越来越重视雪盖的气候效应和作为季度预报因子的作用．     

重庆市城市热岛效应变化特征及减缓措施

利用1961～2016年重庆市逐日气温资料,分析讨论了重庆市主城区56年城市热岛效应的变化趋势和年变化特征,并利用2009～2016年的逐时气温资料分析讨论了城市热岛效应的日变化特征。结果表明:56年来重庆市城市热岛效应总体呈上升趋势,各季节中盛夏上升最明显;重庆市城市热岛效应存在明显的年变化特征,盛夏的热岛效应最强,初春次之,仲春至初夏的热岛效应最弱;重庆市城市热岛效应具有较明显的日变化特征,各季节热岛效应均表现为白天弱,夜间强。重庆市城市热岛效应的形成及其变化,既受到地理位置、气象条件等自然因素的影响,更由城市下垫面变化(绿地和水体的面积及分布)、大气污染、人为热排放等城市化进程因素所决定。结合重庆城市特点综合运用多种措施可以减缓重庆城市热岛效应。      

苏州城市化进程与城市气候变化关系研究

利用1970—2007年苏州城市及近郊县(市)气象站观测资料,结合Landsat 5卫星反演资料,统计分析城市化进程,对苏州区域气候变化的影响。分析结果表明:从1990s中后期开始,随着经济发展,苏州城市建设速度明显加快,城市化进程对苏州气候影响明显,城、郊气温均有明显的上升趋势,相对湿度呈现下降趋势,降水量整体上呈现上升的趋势,日照时数有明显的下降的趋势;苏州城市热岛效应显现、城市霾出现、太湖蓝藻爆发、极端气候事件增多,也与快速的城市化进程有着一定的关系。     

河西东部绿洲农作物生物量变化特征初探

利用地处干旱绿洲的河西走廊东部武威农业气象试验站1994—2001年农作物玉米生物量观测资料,分析了河西走廊东部绿洲农作物生物量年际、年内变化特征。结果表明：玉米叶面积、叶面积指数及叶、穗、株干重的年内变化呈S型曲线,叶、叶鞘、茎、穗、株鲜重及叶鞘、茎干重的年内变化表现为缓慢增长快速增长一缓慢增长一下降的趋势;各生物量数值在不同生长发育期存在不一致的年际变化,而生物量年内变化趋势在不同年份基本保持一致,但阶段变化速率有一定的年际差异。研究认为：在全球气候变化大背景下,农作物生物量变化的基本特征没有改变,但全球气候变化对农作物生物学进程及其生物量积累产生了一定的扰动．并且在不同生物量的不同生长时段产生不同的影响。     

高空西风急流东西向形态变化对梅雨期降水空间分布的影响

利用40年的NCEP/NCAR再分析候平均资料和同期长江中下游地区逐日降水资料,使用合成方法分析了梅雨期东亚副热带高空西风急流的东西位置和形态变化特征,探讨了高空西风急流对梅雨期降水空间分布的影响.分析结果表明,梅雨期东亚大陆上空西风急流强度减弱且持续维持、西太平洋上空西风急流核分裂减弱直至出梅后消失,这是梅雨期200 hPa东亚高空西风急流东西向位置变化的主要特征.梅雨期,200 hPa副热带西风急流中心呈现东西向位置变化和海陆分布形态差异,西风急流中心东西向位置变化对梅雨起讫有着较好的指示意义.梅雨期东亚副热带高空西风急流东西形态分布差异不仅影响到长江中下游地区降水空间集中区的位置而且还影响到降水中心强度.进一步分析表明,当东亚西风急流主体位于西太平洋上空时,在长江下游地区形成高低空急流耦合的环流形势,强烈的辐合上升运动加上充足的水汽条件供应,有利于在长江下游形成集中的强降水区域.当高空西风急流位于东亚大陆上空时,在长江中下游地区高低空急流无耦合形势存在,长江中下游地区也没有强的集中降水区域.因此,东亚副热带高空西风急流东西向形态变化对长江中下游地区的高低空环流结构、地面集中降水区域的空间分布具有重要的影响.     

The coherent interdecadal changes of East Asia climate in mid-summer simulated by BCC_AGCM 2.0.1

This study proposes primary diagnostic metrics to evaluate the integrated structure of interdecadal changes of East Asian climate in mid-summer (July–August) over the recent half-century (1955–2000) in numerical models. The metrics are applied to comprehensively examine the performance of BCC_AGCM (Beijing Climate Center atmospheric general circulation model) version 2.0.1. When forced by historical sea surface temperatures (SST), the ensemble simulation with the BCC_AGCM reasonably reproduced the coherent interdecadal changes of rainfall, temperature and circulation. The main feature of the “southern-flooding-and-northern-drought” rainfall change is captured by the model. Correspondingly, the tropospheric cooling in the upper and middle troposphere, the southward shift of upper level westerly jet and weakening of the low-level southwesterly monsoon flow are also reproduced, as well as their relationships with rainfall changes. One of the main deficiencies of the simulation is that the amplitudes of the changes of tropospheric cooling and large-scale circulation are both much weaker than those in reanalysis, and they are consistent with the rainfall deficiency. Also, the upper and middle troposphere cooling center and decreasing of upper-level westerly jet axis shift westward in the model simulations compared with that in the observations. Overall, although BCC_AGCM shows problems in simulating the interdecadal changes of East Asia climate, especially the amplitude and locations of change centers, it reasonably represents the observed configuration of rainfall variation and the associated coherent temperature and circulation changes. Therefore, it could be further used to discuss the mechanisms of the interdecadal variation in East Asia. Meanwhile, the reasonably reproduced configuration of rainfall and its associated large-scale circulation by SST-forced runs indicate that the interdecadal variations in East Asia could mostly arise from the regional response to the global climate change.     

Subseasonal Change in the Seesaw Pattern of Precipitation between the Yangtze River Basin and the Tropical Western North Pacific during Summer

There is a well-known seesaw pattern of precipitation between the tropical western North Pacific(WNP) and the Yangtze River basin(YRB) during summer. This study identified that this out-of-phase relationship experiences a subseasonal change;that is, the relationship is strong during early summer but much weaker during mid-summer. We investigated the large-scale circulation anomalies responsible for the YRB rainfall anomalies on the subseasonal timescale. It was found that the YRB rainfall is mainly affected by the tropical circulation anomalies during early summer, i.e., the anticyclonic or cyclonic anomaly over the subtropical WNP associated with the precipitation anomalies over the tropical WNP. During mid-summer, the YRB rainfall is mainly affected by the extratropical circulation anomalies in both the lower and upper troposphere. In the lower troposphere, the northeasterly anomaly north of the YRB favors heavier rainfall over the YRB by intensifying the meridional gradient of the equivalent potential temperature over the YRB. In the upper troposphere, the meridional displacement of the Asian westerly jet and the zonally oriented teleconnection pattern along the jet also affect the YRB rainfall. The subseasonal change in the WNP–YRB precipitation relationship illustrated by this study has important implications for the subseasonalto-seasonal forecasting of the YRB rainfall.     

1958年7月亚洲东南部西南季风区和太平洋信风区平均流场和平均经圈环流

亚洲东南部西南季风区和太平洋信风区环流特点有显著的不同。在季风区有南部下沉、北部高原地区上升的垂直季风环流,高层有东风急流,下层有达400毫巴高度的深厚的西南气流。在信风区、低纬度则存在着典型的Hadley环流,高层有夏季太平洋中部副热带西风急流,下部有东北信风,东风随高度减弱。 季风垂直环流的存在,进一步说明了季风形成的因子。     

寒潮期间高空波动与东亚急流的相互作用

本文分析了东亚寒潮爆发过程中,高空波动和高空急流的相互作用,得出如下结果:(1)高空波动的动量和热通量输送,使高空急流迅速加速并同时导致急流入口区质量环流的加强.(2)质量环流引起中高纬度对流层顶下沉并使高空锋区加强.(3)对流层顶下沉和高空锋区的加强促使平流层下层的气流沿对流层顶折叠处下伸进入对流层,造成对流层中、上部层结及位涡分布的改变.(4)位涡分布的改变制约了斜压波发展的能量源,致使高空波动减弱.     

2010年我国南方两次持续性强降水的环流特征

通过对2010年夏季我国南方两次持续性强降水期间对流层高、中、低多个大尺度关键影响系统的时空演变特征及其影响机制的分析和比较,讨论了我国南方持续性强降水的大气环流特征。结果表明:这两次持续性强降水均出现了东亚西风带沿海低槽不断快速重建或加深,且中纬度锋区位置稳定维持,低空西南急流反复加强,且其轴线左侧的南风经向强梯度带位置相对稳定,副热带高空西风急流和南亚高压脊线及西太平洋副热带高压的纬度带位置相对稳定;相应地,在强降水带上空反复出现强烈的低层水汽辐合抬升、高层辐散抽吸及垂直上升运动发展,进而形成持续性强降水。西西伯利亚低槽的不断快速重建与加深 (东移)、马斯克林高压西侧高压及马斯克林高压的不断加强东移、副热带高空西风急流的建立和维持对南方持续性强降水具有超前指示意义。强降水带位于东亚低空西南急流轴左侧南风经向强梯度辐合带、高空西风急流南侧至南亚高压脊线北侧之间的强辐散区及中层垂直上升速度大值带中。     

Upper- and Lower-tropospheric Circulation Anomalies Associated with Interannual Variation of Pakistan Rainfall during Summer

This study investigated the large-scale circulation anomalies, in both the upper and lower troposphere, associated with the interannual variation of rainfall in Pakistan during summer, using the station observation data in this country and circulation data of the NCEP?NCAR reanalysis from 1981 to 2017. Results showed that the upper- and lower-tropospheric circulation anomalies associated with monthly rainfall variability exhibit similar features from June to August, so analyses were performed on June?August circulation and Pakistan rainfall data. The analyzed results indicated that summer rainfall in Pakistan is enhanced when there is an anticyclonic anomaly to the northwest of Pakistan in the upper troposphere and easterly anomalies along the southern foothills of the Himalayas in the lower troposphere, and vice versa. These upper- and lower-tropospheric circulation anomalies were found to be related, but show unique features. The upper-tropospheric anticyclonic anomaly is closely related to the Silk Road Pattern along the Asian westerly jet, while the lower-tropospheric easterly anomalies are related to the cyclonic anomaly to the south of Pakistan, i.e., intensified South Asian monsoon trough. The results presented here suggest that the interannual variability of summer rainfall in Pakistan is a combined result of upper- and lower-tropospheric circulation anomalies, and of extratropical and tropical circulation anomalies.     

Simulation of the westerly jet axis in boreal winter by the climate system model FGOALS-g2

The major features of the westerly jets in boreal winter, consisting of the Middle East jet stream (MEJS), East Asian jet stream (EAJS) and North Atlantic jet stream (NAJS), simulated by a newly developed climate system model, were evaluated with an emphasis on the meridional location of the westerly jet axis (WJA). The model was found to exhibit fairly good performance in simulating the EAJS and NAJS, whereas the MEJS was much weaker and indistinguishable in the model. Compared with the intensity bias, the southward shift of the WJA seems to be a more remarkable deficiency. From the perspective of Ertel potential vorticity, the profiles along different westerly jet cores in the model were similar with those in the reanalysis but all shifted southward, indicating an equatorward displacement of the dynamic tropopause and associated climatology. Diagnosis of the thermodynamic equation revealed that the model produced an overall stronger heating source and the streamfunction quantifying the convection and overturning Hadley circulation shifted southward significantly in the middle and upper troposphere. The two maximum centers of eddy kinetic energy, corresponding to the EAJS and NAJS, were reproduced, whereas they all shifted southwards with a much reduced intensity. A lack of transient eddy activity will reduce the efficiency of poleward heat transport, which may partially contribute to the meridionally non-uniform cooling in the middle and upper troposphere. As the WJA is closely related to the location of the Hadley cell, tropopause and transient eddy activity, the accurate simulation of westerly jets will greatly improve the atmospheric general circulation and associated climatology in the model.     

影响东北的两个罕见气旋发展机制对比

2007年3月3—5日和2016年5月2—3日有两个气旋（简称C304和C502）在江淮流域生成后,以相似路径影响东北地区,但发展强度不同。利用常规观测资料和NCEP FNL分析资料,通过对涡度平流、温度平流、湿位势涡度及锋生函数等物理量进行诊断并结合高、低空环流形势对两个气旋发展动力机制进行对比分析,结果表明:C304低空温度平流在气旋发展初期起主要作用,高空正涡度平流为地面气旋发展提供高空辐散场,地面气旋中心上空垂直上升运动增强,对流层低层斜压性明显,气旋性涡度增加主要在对流层下层,低空斜压强迫是主要发展机制;C502低空温度平流弱,斜压性不明显,高空正涡度平流促使高空闭合环流发展,对流层上层有高湿位涡舌发展下垂并与对流层下层正湿位涡柱耦合贯通,垂直上升运动分布在地面气旋中心两侧,高空位涡下传是主要发展机制。两个气旋发生发展在对流层上层两支急流共存、急流非纬向性反气旋性弯曲环流形势下,对流层低层为气旋式环流背景。     

On the onset of the south china sea summer monsoon in 1998

1.IntroductionChinesescientistshavepointedoutsincethe1980sthattheAsiansummermonsooniscomposedoftheSouthAsian(Indian)monsoonsystemandtheEastAsianmonsoonsystem,whichhavetheirparticularcharacteristicsrespectivelybutalsointeractoneachother;andtheAsiansummermonsoonbreaksoutintheSouthChinaSea(SCS)regionatfirst,thenspreadsnorthwestwardandnorthwardrespectively,finallytheSouthAsiansummermonsoonandtheEastAsiansummermonsoonaresetup(TaoandChen,1987;JinandChen,1985;Zhuetal.,1986).Muchattentionhasbe…