Changes in climate variability and seasonal rainfall extremes: a case study from San Fernando (Spain), 1821–2000

Summary ?Small changes in the mean and standard deviation values can produce relatively large changes in the probability of extreme events. The seasonal precipitation record in San Fernando (SW Spain) for 1821–2000 is used to investigate how much the relative frequency of dry and wet seasons changes with changes in mean value and standard deviation. The percentiles P10, P25, P75 and P90 of the reference period 1961–1990 are used to define dry and wet seasons. The probability of extreme seasons as function of mean and standard deviation is analysed. The main conclusion is a non-linear relationship between changes in mean and standard deviation values and extreme seasons probability. With these threshold values, the main influence corresponds to changes in mean value. Results are discussed bearing in mind projections of General Circulation Models on future climate in southern Iberian Peninsula. Received June 11, 2001; Revised March 3, 2002     

江淮流域一种中间尺度暴雨系统的研究

通过一次江淮流域暴雨天气过程的分析,发现在对流层低层存在一种中间尺度扰动。它形成于对流层低层的冷锋锋区上,其流场的气旋性环流特征和结构在600—900米高度上最明显。它是产生江淮流域暴雨的主要天气系统之一。6小时雨量可达15—35毫米,一次扰动过程的总降水量约100—120毫米,水汽辐合主要集中在900米—700毫巴层。扰动的时间尺度为1—2天,计算结果表明,这类扰动的发生、发展与对流层低层锋区斜压性的位能释放有较好的关系。     

植被地表反照率动态模拟方法比较-以玉米农田为例

利用2007年锦州玉米农田生态系统野外观测站玉米生长季辐射资料,对地表反照率综合模型、半经验双层模型和简化双层模型模拟精度进行比较。结果表明：简化双层模型在玉米生育初期模拟能力较差,其他时段模拟能力都较强,尤其在玉米生育后期更为明显;半经验双层模型除在玉米叶面积指数处于最大时期模拟误差较小外,其他时段基本无法模拟。综合模型大部分时段模拟能力都较强,仅在玉米生育后期模拟能力稍差,该模型对实现玉米农田地表反照率动态参数化更为理想,可为改进陆面过程模型提供参考。     

梅雨锋气旋暴雨的 Q 矢量分析：个例研究

文中对修改的Q矢量(Q*)进行转化、处理后,所得Q矢量(记为QN矢量)与准地转Q矢量具有类似的计算表达式,但其完全用实际风场资料进行计算.结合1991年7月5日20:00-6日20:00 BST的一次典型江淮梅雨锋气旋暴雨过程比较分析表明,QN矢量诊断能力较准地转Q矢量优越,且700 hPa QN矢量散度辐合场对同时期地面降水场的水平分布特征具有较好指示作用.将QN矢量沿以等高线为参照线的自然坐标系进行分解(简称为PG分解),所得各项QNalst矢量(沿流伸展项)、QNcurv矢量(曲率项)、QNshdv矢量(切变平流项)及QNcrst矢量(穿流伸展项)具有明确物理意义.对1991年7月5日20:00-6日20:00 BST此次江淮梅雨锋气旋暴雨过程进行QN矢量PG分解研究表明,QN矢量PG分解可以揭示出天气现象过程中"总"的QN矢量(即QN矢量)难以揭示的潜在物理机制.具体地讲,在梅雨锋气旋不同阶段,QNalst矢量散度场的水平分布特征都与总QN矢量散度场相似,其散度辐合场在总QN矢量散度辐合场中都占有较大比例,对总QN矢量散度对垂直运动产生的激发与强迫作用贡献大,对梅雨锋气旋引发降水的发生始终都起着主要的促进强迫作用.QNcurv矢量在整个梅雨锋气旋暴雨演变过程中,对降水发生的促进作用逐渐减小,直至起到抑制作用.QNshdv矢量对降水发生的促进作用则随着梅雨锋气旋发生发展而明显增强,但随着梅雨锋气旋的东移衰亡,其对降水发生的促进作用迅速减弱,直至对降水的发生基本无影响.对于QNcrst矢量来讲,其在梅雨锋气旋的发生发展及强盛阶段对降水的发生基本不起作用,但在梅雨锋气旋衰亡阶段其对降水发生起着主要促进作用.另外,在梅雨锋气旋发生发展及强盛时期,QNalst矢量与QNcurv矢量、QNshdv矢量与QNcrst矢量的散度水平分布特征相似,只不过强度上存在差异,但无明显相互抵消现象,而在梅雨锋气旋衰亡阶段就不同了,QNalst矢量与QNcurv矢量、QNshdv矢量与QNcrst矢量的散度水平分布特征基本相反,且存在明显的相互抵消现象.可见,通过QN矢量PG分解可以揭示出梅雨锋气旋不同阶段降水的强迫因子是不同的.     

Comparison of instrumental and interpolated meteorological data-based summer temperature reconstructions on Mt. Taibai in the Qinling Mountains,northwestern China

Theoretical and Applied Climatology - Previous dendroclimatical studies have been based on the relationship between tree growth and instrumental climate data recorded at lower land meteorological...     

Impact of land-use changes on the genesis and evolution of extreme rainfall event: a case study over Uttarakhand,India

In recent years, hot summers (HS) have played an important role in affecting people’s health and causing natural disasters. However, it is not very clear what HS should be attributed to. In order to investigate that, the anomalous of anticyclone associated with HS in the Mediterranean and North China is examined and compared by using data during the time period 1949~2018. Statistical analysis shows that summer temperature in the Mediterranean and North China is revealing a good correlation when removing the global warming trend. The composite results indicate that the anomalous warming during HS over different regions is both dominantly controlled by an anomalous anticyclone, which enhances the subsidence adiabatic heating of the temperature. Furthermore, the subtropical high (STH) variations faithfully represent the fluctuations in summer temperature over the Mediterranean (cor = 0.78) and North China (cor = 0.80). The anticyclonic anomalies over both focus areas are associated with North Atlantic and Northwest Pacific sea surface temperature (sst), respectively. These results indicate that the total influence of the STH position anomaly should be taken into consideration in different places during HS. However, whether such atmosphere-ocean feedback can be improved by numerical experiments is worthy to be further studied.     

CN05.1气象数据在流域水文模拟中的应用——以新疆开都河流域为例

为探讨中国再分析气象数据集CN05.1在流域水文模拟中的适用性潜力,以开都河流域为研究区,分别使用CN05.1数据集和传统气象站数据驱动SWAT水文模型,采用决定系数（R ²)、纳什效率系数（NSE）和相对误差（R_e）等评价指标对二者模拟效果进行对比分析,以确定CN05.1数据的适用性;最后采用两种数据订正方法对CN05.1降水数据进行了订正,并以水文模拟效果进行评价。研究结果表明:(1) CN05.1气象数据在开都河流域的水文气象模拟中具有较强的适用性;(2) 基于SWAT模型的水文模拟显示,CN05.1数据驱动的水文模拟精度高于传统气象站数据,其率定期（1995—2005年）和验证期（2006—2016年）的R ²分别为0.81和0.73,NSE分别为0.81和0.72,R_e分别为-0.97%和0.39%;(3)两种数据订正方法均能较好地再现流域径流变化过程,但基于空间关系订正法的径流模拟效果更好,R ²和NSE均在0.72以上,|R_e|＜1.7%。由此,订正后的CN05.1降水数据一方面弥补了传统气象站数据缺失的问题,另一方面补足了未订正CN05.1降水数据在径流模拟中峰值欠佳的问题。     

A case study on the role of water vapor from Southwest China in downstream heavy rainfall

Based on the observation data analysis and numerical simulation, the development of an eastwardmoving vortex generated in Southwest China during the period 25 27 June 2003 is studied. The water vapor budget analysis indicates that water vapor in the lower troposphere over Southwest China is transported downstream to the Yangtze and Huaihe River valleys by the southwesterly winds south of the vortex center. A potential vortieity （PV） budget analysis reveals that a positive feedback between latent heat release and low-level positive vortieity plays a vital role in the sudden development and eastward movement of the vortex. Numerical simulations are consistent with these results.     

锦江河防汛决策支持系统建设思路及方法初探

洪涝灾害是我区的主要自然灾害之一，汛期又是我区洪涝灾害的多发季节，难确、及时的防汛指挥决策，对于减轻洪涝灾害造成的损失尤为重要。通过对锦江河防汛决策支持系统建设有关问题的探讨，提出了建立防汛决策支持系统的思路和方法，供有关部门参考。     

Comparison of monthly rainfall generated from dynamical and statistical downscaling methods: a case study of the Heihe River Basin in China

Theoretical and Applied Climatology - Monthly rainfall in the Heihe River Basin (HRB) was simulated by the dynamical downscaling model (DDM) and statistical downscaling model (SDM). The...     

A case study on a strong tropical disturbance and record heavy rainfall in Hat Yai, Thailand during the winter monsoon

The evolutionary process and structural characteristics of the atmospheric circulation and synoptic situation which caused the record heavy rainfall with a precipitation amount of 550 mm in Hat Yai,Thailand from 20 to 23 November 2000 is studied. In the study, the modern three dimensional observational data were collected as completely as possible, and detailed analyses were made. It is revealed that the colds urges of the Asian winter monsoon that originate from Siberia can arrive at the lower latitudes, including South Thailand, Malaysia, Indonesia, cause strong heavy rainfall there, and interact with weather systems in the near-equatorial regions of the Southern Hemisphere. This is strongly supported by Chinese scientist‘s original finding in 1930s. The strong convective cloud clusters in the above areas are generated by the direct influence of the cold surges, and are related with the South China Sea disturbances in the lowe rtroposphere. The maximum of the convergence of total moisture flux near South Thailand in the situation under study implies that the water vapour supply is abundant and very favorable to the occurrence of the heavy rainfall. The release of latent heat enhances the Hadley Circulation also. The feedback of the strong severe weather on climate indeed exists, and there are pronounced interactions between the multi-scale systems and between both hemispheres.     

Assessment of future olive crop yield by a comparative evaluation of drought indices: a case study in western Turkey

A comparative performance analysis was studied on well-known drought indices (Standardized Precipitation Index, Palmer Drought Severity Index (PDSI) and its moisture anomaly index (Orig-Z), and self-calibrated Palmer Drought Severity Index (SC-PDSI) and its moisture anomaly index (SC-Z)) to determine the most appropriate index for assessing olive (O. europaea L.) yield for oil in seven crop regions (Mu?la, Ayd?n, ?zmir, Manisa, Bal?kesir, ?anakkale, and Bursa) in western Turkey and to evaluate the vulnerability of olive yield for oil to climate change with future projections provided by the Hadley Centre for Climate Prediction and Research ENSEMBLES project (HadCM3Q0). A series of curvilinear regression-based crop yield models were developed for each of the olive-growing regions based on the drought indices. The crop yield model that performed the best was the SC-PDSI model in Mu?la, Ayd?n, ?zmir, and Manisa regions and the PDSI model in ?anakkale, Bal?kesir, and Bursa regions. The SC-PDSI index-based model described 65%, 62%, 61%, and 62% of the measured variability of olive yield in Mu?la, Ayd?n, ?zmir, and Manisa regions, respectively. The PDSI index-based model explained 59%, 58%, and 64% of the measured variability of olive yield in Bal?kesir, ?anakkale, and Bursa regions, respectively. The vulnerability of the olive yield for oil to HadCM3Q0 future climate projections was evaluated for Ayd?n and ?anakkale regions due to the resolution of the regional climate model. In terms of the future scenarios, the expected decrease in olive yield residuals was 2.5?ton (10³ trees)^?1 and 1.78?ton (10³ trees)^?1 in Ayd?n and ?anakkale regions, respectively.     

Investigating the topographic and climatic effects on vegetation using remote sensing and GIS: a case study of Kharestan region,Fars Province,Iran

Theoretical and Applied Climatology - This study seeks to investigate the effect of topographic (slope, elevation, and aspect) and climatic (precipitation and temperature) factors on vegetation in...     

风廓线雷达垂直速度与地面降雨关系研究：以济南为例

基于风廓线雷达数据产品的垂直速度资料和地面气象观测站2014年分钟降雨记录,采用多项式非线性拟合方法,探讨了各季节特征高度层垂直速度与地面降雨之间的相关关系;并根据场次降雨过程的分钟数据分析了垂直速度阈值对降雨开始、结束时间以及降雨强度的指示性。结果表明,垂直速度能够反映雨滴的下落速度特征,综合各个高度层来看,700 m高度层垂直速度与小时雨量回归方程拟合优度较为稳定,其他高度层在不同季节拟合优度差别略大;垂直速度的大小虽不能完全定量地预报降雨强度,但对于整个过程的雨强波动变化有着明显的指示性作用,700 m高度层垂直速度对于降雨的预报指示效果最为稳定。垂直速度对降水的指示性可用于灾害性天气,如暴雨、冰雹、降雪等的预警及临近预报,其阈值的确定受降水相态、降水类型、气温、湿度、湍流等影响,且并非唯一指标。     

抓住机遇深化改革加速发展--对乐山市气象业务服务体系建设的思考

乐山市气象事业在各级党委、政府的领导关心和支持下,近年来有了长足的发展.然而,面对当今世界和地方经济、科技的飞速发展,对气象工作的要求日益提高.未来的五年,乐山气象事业的发展该怎样定位?它的现状与全国乃至发达省市的事业发展水平差距又有多大?我们该做些什么?如何找准切入点来解决现实存在的问题?为此,对乐山市、县两级气象事业发展现状进行全面的调研和综合分析,尽可能客观地分析存在的问题,用详实的数据来定位我们的现状,从而有针对性的提出对策,这对制定和实施未来五年事业发展的规划和发展目标都具有重要意义.     

抓住机遇 深化改革 加速发展——对乐山市气象业务服务体系建设的思考

乐山市气象事业在各级党委、政府的领导关心和支持下 ,近年来有了长足的发展。然而 ,面对当今世界和地方经济、科技的飞速发展 ,对气象工作的要求日益提高。未来的五年 ,乐山气象事业的发展该怎样定位 ?它的现状与全国乃至发达省市的事业发展水平差距又有多大 ?我们该做些什么 ?如何找准切入点来解决现实存在的问题 ?为此 ,对乐山市、县两级气象事业发展现状进行全面的调研和综合分析 ,尽可能客观地分析存在的问题 ,用详实的数据来定位我们的现状 ,从而有针对性的提出对策 ,这对制定和实施未来五年事业发展的规划和发展目标都具有重要意义。…     

珠穆朗玛峰北坡地区河谷局地环流特征观测分析

利用中国科学院珠穆朗玛峰大气与环境综合观测研究站的大气边界层塔站数据分析了珠峰北面一处河谷中局地环流的日变化特征.发现该河谷中的局地环流主要受山谷风和冰川风的影响,后者自影响主要集中在下午和傍晚,冰川风强度较大,地面最大风速达到10 m·s-1.冰川风开始出现的时间通常是气温达到一天中最高的时刻,这表明冰川风气流温度较低,带来了降温.另外,对空气湿度变化的分析中也能发现冰川风气流的影响.     

Impact of moisture flux convergence and soil moisture on precipitation: a case study for the southern United States with implications for the globe

Interactions between soil moisture, evapotranspiration (ET), atmospheric moisture fluxes and precipitation are complex. It is difficult to attribute the variations of one variable to another. In this study, we investigate the influence of atmospheric moisture fluxes and land surface soil moisture on local precipitation, with a focus on the southern United States (U.S.), a region with a strong humidity gradient and intense moisture fluxes. Experiments with the Weather Research and Forecasting model show that the variation of moisture flux convergence (MFC) is more important than that of soil moisture for precipitation variation over the southern U.S. Further analyses decompose the precipitation change into several contributing factors and show that MFC affects precipitation both directly through changing moisture inflow (wet areas) and indirectly by changing the precipitation efficiency (transitional zones). Soil moisture affects precipitation mainly by changing the precipitation efficiency, and secondly through direct surface ET contribution. The greatest soil moisture effects are over transitional zones. MFC is more important for the probability of heavier rainfall; soil moisture has much weaker impact on rainfall probability and its roles are similar for the probability of intermediate-to-heavy rainfall (>10 mm day^?1). Although MFC is more important than soil moisture for precipitation over most regions, the impact of soil moisture could be large over certain transitional regions. At the submonthly time scale, the African Sahel appears to be the only major region where soil moisture has a greater impact than MFC on precipitation. This study provides guidance to understanding and further investigation of the roles of local land surface processes and large-scale circulations on precipitation.