Spatial and temporal variability of reference evapotranspiration and influenced meteorological factors in the Jialing River Basin,China

Theoretical and Applied Climatology - Reference evapotranspiration (ETr) is one of the important parameters in the hydrological cycle. The spatio-temporal variation of ETr and other meteorological...     

贵州夏季大暴雨天气的时空分布特征分析

利用贵州省1998—2007年5—8月逐日降水资料,分析了贵州夏季大暴雨的时空分布特征和基本特点。贵州大暴雨站次年际变化呈波浪型起伏变化,与大暴雨天数变化趋势较为一致;大暴雨主要出现在6—7月,共出现200站次,占总站次的83％,6月上旬-7月下旬是大暴雨发生的集中期,其中6月下旬和7月上旬最为集中,出现96站次,占总次数的40％;大暴雨的地域分布受地形的影响显著,总体分布不均,位于苗岭东西两段、大娄山和武陵山的东南坡的迎风坡是贵州省的大暴雨中心;大范围大暴雨发生较少,主要在6月下旬和7月中上旬;以单日大暴雨为主,连续性大暴雨以2d居多。     

A survey of temporal and spatial reference crop evapotranspiration trends in Iran from 1960 to 2005

Reference crop evapotranspiration (ET₀) is one of the most important climatic parameters which plays a key role in estimating crop water demand and scheduling irrigation. Under global warming and climate change conditions, it is needed to survey the trend of ET₀ in Iran. In this study, ET₀ values were determined based on FAO-56 Penman-Monteith equation over 32 synoptic meteorological stations during 1960–2005; and analyzed spatially and temporally in monthly, seasonal and annual time scales. After removing the significant lag-1 serial correlation effect by pre-whitening, non-parametric statistical Mann–Kendall (MK) test was used to detect the trends. The slope of the changes was determined by Sen’s slope estimator. In order to facilitate in trend analysis, the 10 moving average low pass filter were also applied on the normalized annual ET₀ time series. Annual ET₀ time series and filtered ones were then classified by hierarchical clustering in three clusters and then mapped in order to show the patterns of different clusters. Results showed that the significant decreasing trends were more considerable than increasing ones. Among surveyed stations, and on an annual time scale, the highest and lowest annual values of Sen’s slope estimator were observed in Tabas with (+) 72.14 mm per decade and Shahrud with (?) 62.22 mm per decade, respectively. Results also indicated that the clustered map based on normalized and filtered annual ET₀ time series is in accordance with another map which showed spatial distribution of increasing, decreasing and non-significant trends of ET₀ on annually time scale. Exploratory and visual analysis of smoothed time series showed increasing trend in recent years especially after 1980 and 1995. In brief, the upward trend of ET₀ in recent years is a crucial issue with regard to the high cost of dam construction for agricultural aims in arid and semi-arid regions e.g. Iran.     

湖北省积雪时空特征分析

利用湖北省77个测站1961-2007年气象资料,分析了积雪的时空特征。结果表明,湖北省积雪年际变化振幅明显,20世纪60年代到70年代中期缓慢增加,为积雪多发期;80年代年波动较大;90年代开始明显减少。月积雪日数呈准正态分布,1月最多,2月、12月次之。积雪空间分布表现为西部多,中东部少;山地多,丘陵平原少;沿江多,内陆少。有利于湖北大范围出现积雪的大尺度背景的环流类型主要有纬向型和两槽一脊型。出现积雪时24h变压Δp24为正,24h变温Δt24和水汽压变化Δe24为负,地面气象要素的异常变化,也可以作为积雪预报的着眼点之一。     

新疆阿勒泰地区夏季短时强降水时空分布特征

利用2010—2018年夏季阿勒泰地区112个自动气象站逐时降水资料,采用常规统计方法分析了阿勒泰地区夏季短时强降水时空分布特征。结果表明,2010—2018年夏季阿勒泰地区短时强降水的空间分布极不均匀,主要发生在阿尔泰山和沙吾尔山迎风坡、地形陡升区、喇叭口地形、戈壁和乌伦古湖交界区等复杂地形附近;发生次数年际变化大,2017年出现最多达95次,2010年出现最少为10次;极大值出现在2017年6月30日15:00哈巴河县合孜勒哈克村(37.5 mm/h),极小值出现在2015年8月9日17:00福海县工业园区(22.5 mm/h)。旬、日发生频次变化均呈单峰型,旬峰值出现在7月上旬,日高峰值时段出现在午后至傍晚(19时左右);各站短时强降水持续时间为1—2 h,区域性短时强降水最长持续时间为5 h; 2017年短时强降水出现最多、持续时间最长、范围最广、强度最强。     

Sensitivity analysis of monthly reference crop evapotranspiration trends in Iran: a qualitative approach

Theoretical and Applied Climatology - The main objective of this study was to analyze the sensitivity of the monthly reference crop evapotranspiration (ETo) trends to key climatic factors (minimum...     

An analysis of yearly trends in growing degree days and the relationship between growing degree day values and reference evapotranspiration in Turpan area, China

The growth and development of crops is commonly regarded as a function of time alone. However, this approach can be inadequate due to temperatures which vary from year to year caused by global climate change. This prompted the development of the growing degree day concept, which incorporates information on both the passage of time and the temperature experienced by the crop plant during that time. Crop water requirements, which are estimated by multiplying reference evapotranspiration values by a crop-specific coefficient, play a crucial role in the management of hydrologic cycles on arable land. Consequently, it would be useful to identify the relationships between cumulative growing degree days and reference evapotranspiration, in order to develop new methods for predicting crop growth and development periods and calculating reference evapotranspiration. This paper describes annual trends in cumulative growing degree days values and their impact on grape growth. Three different methods for calculating cumulative growing degree days values were evaluated as well. Several key findings were achieved. First, for the period between 1952 and 1995, the cumulative growing degree days values for specific days of the year were normally distributed. Second, the relationship between the relative cumulative growing degree days value and the passage of time can be accurately described by using a cubic polynomial function. Third, the day-to-day change in the average relative cumulative reference evapotranspiration can be described using an exponential function of time, which can be used to calculate the relative cumulative reference evapotranspiration value for any given day of the year. Fourth, there was a significant correlation between the relative cumulative growing degree days and cumulative reference evapotranspiration values during the period between grape budding and maturity, which can be described using a cubic polynomial function. Finally, a new method for determining the ET0 value for any given day of the year was developed; this method requires only a knowledge of the CGDD-at-year-end and no sophisticated meteorological data.     

Spatial and temporal characteristics of droughts in Luanhe River basin,China

Theoretical and Applied Climatology - The spatial and temporal characteristics of drought are investigated for Luanhe River basin, using monthly precipitation data from 26 stations covering the...     

中国东北地区中尺度对流复合体的时空分布特征

普查2005年5月1日至2008年9月30日FY-2C每隔30 min一次的红外云图,根据修正的MCC（Mesoscale Convective Complexes）标准,统计分析中国东北地区出现的MCC变化。结果表明：4 a共出现了22个MCC,其中19个出现在7-8月;东北地区MCC生成源地有明显的地域特点,MCC的生成与大兴安岭的地形密切相关,而辽宁和吉林东部极少生成MCC。中国东北地区MCC平均生命史为9.3 h,比美洲及中国南方地区都短,而≤-52℃和≤-32℃冷云罩面积明显大于以上两个区域;东北地区具有明显的夜发性特征,近85 %的MCC生成于午后到傍晚,15-24时是MCC对流最旺盛的时段。     

贵州山地高分辨旅游气象舒适度时空分布特征

采用空间曲面插值方法,对省内气象台站相关气象数据进行空间插值,得到高分辨的气候要素空间分布栅格数据。然后以贵州省旅游气象舒适度标准(DB52/T556-2009)作为区划标准,对上述栅格数据进行空间分析计算,得到贵州全省四个季节1.0×1.0Km的气象舒适度时空分布。分析表明:贵州省大部分地区的最大气象优势为夏季避暑旅游,此外,还具备了将适宜旅游季节向春季和秋季延伸的有利条件,使贵州的旅游气候资源得到科学准确的定位,为贵州进行"避暑旅游气候品牌"打造提供了科技支撑。     

Spatial and temporal trends of extreme temperature and precipitation in the Daqing River Basin,North China

Theoretical and Applied Climatology - According to the daily maximum and minimum temperature and the precipitation at 40 meteorological stations in the Daqing River Basin of China during...     

Spatial patterns and temporal trends of precipitation in Iran

Spatial patterns of monthly, seasonal and annual precipitation over Iran and the corresponding long-term trends for the period 1951–2009 are investigated using the Global Precipitation Climatology Centre gridded dataset. Results suggest that the spatial patterns of annual, winter and spring precipitation and the associated coefficients of variation reflect the role of orography and latitudinal extent between central-southern arid and semi-arid regions and northern and western mountainous areas. It is also shown that precipitation occurrence is almost regularly distributed within the year in northern areas while it is more concentrated in a few months in southern Iran. The spatial distribution of Mann–Kendal trend test (Z statistics) for annual precipitation showed downward trend in north-western and south-eastern Iran, whereas western, central and north-eastern exhibited upward trend, though not statistically significant in most regions. Results for winter and autumn revealed upward trend in most parts of the country, with the exception of north-western and south-eastern where a downward trend is observed; in spring and summer, a downward trend seems to prevail in most of Iran. However, for all seasons the areas where the detected trend is statistically significant are limited to a few spot regions. The overall results suggest that the precipitation is decreasing in spring and summer and increasing in autumn and winter in most of Iran, i.e. less precipitation during the warm season with a consequent intensification of seasonality and dryness of the country. However, since the detected trends are often not statistically significant, any stringent conclusion cannot be done on the future tendencies.     

Precipitation extremes in a karst region: a case study in the Guizhou province, southwest China

The topography of hilly landscapes modifies crop environment changing the fluxes of water and energy, increasing risk in these vulnerable agriculture systems, which could become more accentuated under climate change (drought, increased variability of rainfall). In order to quantify how wheat production in hilly terrain will be affected by future climate, a newly developed and calibrated micro-meteorological model for hilly terrain was linked to a crop growth simulation model to analyse impact scenarios for different European regions. Distributions of yield and growing length of rainfed winter wheat and durum wheat were generated as probabilistic indices from baseline and low (B2) and high (A2) emission climate scenarios provided from the Hadley Centre Regional Climate Model (HadRM3). We used site-specific terrain parameters for two sample catchments in Europe, ranging from humid temperate (southeast UK) to semi-arid Mediterranean (southern Italy). Results for baseline scenario show that UK winter wheat is mainly affected by annual differences in precipitation and yield distributions do not change with terrain, whilst in the southern Mediterranean climate yield variability is significantly related to a slope × elevation index. For future climate, our simulations confirm earlier predictions of yield increase in the UK, even under the high emission scenario. In the southern Mediterranean, yield reduction is significantly related to slope × elevation index increasing crop failure in drier elevated spots but not in wet years under baseline weather. In scenarios for the future, the likelihood of crop failure rises sharply to more than 60%, and even in wet years, yields are likely to decrease in elevated spots.     

低层偏东气流对贵州梵净山东侧强降水的作用

利用2005—2018年贵州省84个国家气象站逐小时降水量资料,采用统计诊断分析方法,在区分量级前提下,结合地形特征,分析贵州1 h短时强降水和逐3 h降水的时空分布特征。结果表明：（1）14 a中短时强降水共出现5 981站次,年均427.2站次,其空间分布与地形特征密切相关,整体呈现南多北少、东多西少的特征,贵州西南部“喇叭口”地形和东南部雷公山南侧“喇叭口”地形与河谷地形重叠区域为短时强降水高发区。短时强降水分级统计显示,99%的短时强降水集中在前两个雨强较小的等级,而R_1h≥80 mm的短时强降水14 a只出现过5站次。各站点最大雨强空间分布与短时强降水的总站次数分布趋势较为一致,一般南部大于北部、中东部大于西部,局部存在差异。平均雨强整体呈现南强北弱的特征。（2）在2005—2013年期间,短时强降水站次数大多处于年均值（427.2站次）之下,2011年达到最低值275站次,2014年站次数骤然增加至564站次,2015年继续增加到最大值662站次,其后迅速回落到比年均值略高的位置小幅变化。各站点短时强降水的年际变化在高发区离散度较大,在贵州西北部低发区离散度较小;月际变化曲线呈单峰型,5—8月份是降水高发时段,6月达到峰值。短时强降水主要以单站出现的局地性降水为主,同一时次出现3站以上的情况很少,以6月最多;短时强降水最早出现旬数呈东早西晚、南早北晚的特征,结束旬数西早东晚,北早南晚;各站点短时强降水出现概率最大旬多数集中在第16—18旬（即6月）;短时强降水日变化的时间曲线呈单峰型,21时至次日07时为高发时段,中午12时前后出现较少。短时强降水日变化的空间分布特征为傍晚到前半夜主要集中在贵州西部,而后半夜多出现在东部和南部地区,中午前后全省均较少出现。（3）逐3 h降水时空分布特征与R_1h大体一致,局部存在一些差异。

     

安顺市大暴雨的时空分布特征与物理量分析

利用2009-2019年安顺市6个国家站和77个区域站的逐日和逐小时降水资料、 Micaps资料,对安顺市大暴雨的时空分布特征及物理量进行分析,结果表明：安顺市年平均大暴雨日数为10.1d,年平均影响范围为54.1站次,5-9月是大暴雨出现的集中期,6月大暴雨出现频次最高,影响范围最广,大暴雨的主要发生时段和最强影响时段出现在夜间到早晨;区域性大暴雨比局地性大暴雨出现时间晚,结束时间早,6月是区域性大暴雨和局地性大暴雨出现最多的月份,5-7月局地性大暴雨出现的频率最高;安顺主要出现单日大暴雨,持续2d以上的大暴雨只出现过16次;大暴雨总日数的空间分布有两个高频区和两个低频区,总量的空间分布与总日数基本一致,强度的空间分布呈南强北弱,总站次的空间分布呈南多北少;在5月预报大暴雨天气时要更注重分析T85和T75,6-7月产生大暴雨时对能量和中低层的水汽含量的要求高于其它月份。