基于SPI的1961－2020年昌吉地区作物生长季气象干旱时空特征研究

基于昌吉地区7个气象站1961－2020年降水量资料，计算昌吉地区作物生长季标准化降水指数（SPI-7）。运用趋势分析法、M-K突变检验法和小波分析法探究了昌吉地区作物生长季SPI-7指数的年际和年代变化特征；在此基础上分析了作物生长季干旱的站次比和干旱强度的年际变化,并结合该区实际发生的旱灾对SPI进行了验证。结果表明：1961—2020年昌吉地区作物生长季标准化降水指数以0.08/10 a的速率呈微弱的正趋势（变湿），在年代变化趋势中呈现出变干-变湿-变干的变化波动, 1981年标准化降水指数由低到高突变；干旱强度呈增加趋势，干旱发生的区域面积有轻微减少的趋势；干旱强度在全区范围内主要为轻旱和中旱等级，并表现为全域性干旱和区域性干旱；空间分布上看干旱率最高区域在东部地区，轻旱主要集中在东部，中旱、重旱和特旱集中在西部地区，干旱强度大的区域大致分布在西部地区；在周期性变化方面，SPI指数存在着6年、9年、16年周期震荡；历史旱灾与SPI指数干旱评价结果吻合率较高，SPI指数在昌吉地区作物生长季的干旱监测与分析中具有较好的实用性。     

Combining the standardized precipitation index and climatic water deficit in characterizing droughts: a case study in Romania

This paper characterizes droughts in Romania using the approach of both the standardized precipitation index (SPI) and climatic water deficit (WD). The values of the main climatic factors (rainfall, temperature, reference evapotranspiration, etc.) were obtained from 192 weather stations in various regions of Romania. Penman–Monteith reference evapotranspiration (ET_o-PM) was used to calculate WD as the difference between precipitation (P) and ET_o-PM. SPI was calculated from precipitation values. There is a clear difference between drought and aridity. Drought occurrence determines higher WD values for plains and plateaus and lower climatic excess water (EW) values for high mountains in Romania, depending on the aridity of the specific region considered and drought severity. WD calculated as mean values for both normal conditions and, for all locations studied, various types of drought was correlated with mean annual precipitation and temperature, respectively. The combined approach of WD and SPI was mainly carried out for periods of 1 year, but such studies could also be done for shorter periods like months, quarters, or growing season. The most arid regions did not necessarily coincide with areas of the most severe drought, as there were no correlations between WD and SPI and no altitude-based SPI zones around the Carpathian Mountains, as is the case for other climate characteristics, soils and vegetation. Water resource problems arise where both SPI values characterize extremely droughty periods and WD values are greatly below ?200 mm/year. This combined use of SPI and WD characterizes the dryness of a region better than one factor alone and should be used for better management of water in agriculture in Romania and also other countries with similar climate characteristics.     

Short-term droughts forecast using Markov chain model in Victoria,Australia

A comprehensive risk management strategy for dealing with drought should include both short-term and long-term planning. The objective of this paper is to present an early warning method to forecast drought using the Standardised Precipitation Index (SPI) and a non-homogeneous Markov chain model. A model such as this is useful for short-term planning. The developed method has been used to forecast droughts at a number of meteorological monitoring stations that have been regionalised into six (6) homogenous clusters with similar drought characteristics based on SPI. The non-homogeneous Markov chain model was used to estimate drought probabilities and drought predictions up to 3 months ahead. The drought severity classes defined using the SPI were computed at a 12-month time scale. The drought probabilities and the predictions were computed for six clusters that depict similar drought characteristics in Victoria, Australia. Overall, the drought severity class predicted was quite similar for all the clusters, with the non-drought class probabilities ranging from 49 to 57 %. For all clusters, the near normal class had a probability of occurrence varying from 27 to 38 %. For the more moderate and severe classes, the probabilities ranged from 2 to 13 % and 3 to 1 %, respectively. The developed model predicted drought situations 1 month ahead reasonably well. However, 2 and 3 months ahead predictions should be used with caution until the models are developed further.

     

Quantile regression and clustering analysis of standardized precipitation index in the Tarim River Basin,Xinjiang, China

Because drought is a very common and widespread natural disaster, it has attracted a great deal of academic interest. Based on 12-month time scale standardized precipitation indices (SPI12) calculated from precipitation data recorded between 1960 and 2015 at 22 weather stations in the Tarim River Basin (TRB), this study aims to identify the trends of SPI and drought duration, severity, and frequency at various quantiles and to perform cluster analysis of drought events in the TRB. The results indicated that (1) both precipitation and temperature at most stations in the TRB exhibited significant positive trends during 1960–2015; (2) multiple scales of SPIs changed significantly around 1986; (3) based on quantile regression analysis of temporal drought changes, the positive SPI slopes indicated less severe and less frequent droughts at lower quantiles, but clear variation was detected in the drought frequency; and (4) significantly different trends were found in drought frequency probably between severe droughts and drought frequency.     

新疆塔城地区1961—2021年季节性干旱演变特征

利用塔城地区9个国家气象观测站1961—2021年逐月降水资料,基于标准化降水量指数(SPI)运用最小二乘法和Mann-Kendall检验等方法分析塔城地区干旱时空分布特征。结果表明：(1)年尺度上,塔城地区干旱发生频率为30.37%,轻旱发生最多,中旱次之；2/3站点SPI呈显著增大趋势,年站次比和干旱强度呈显著减小趋势,干旱程度有所减轻,在1987年之后塔城干旱程度整体偏轻。(2)季节尺度上,夏、秋、冬季在1980年代中期发生干旱减轻的突变,且秋季和冬季分别在2002年和1997年达到显著。(3)在影响范围方面,各季以局域性和全域性干旱为主,全域性干旱发生频率介于20～30%之间；在干旱强度方面,各季轻度干旱发生频率最高,中度以上干旱发生频率介于33～38%之间。(4)近60a塔城地区季节性干旱呈现影响范围缩小,强度减弱的变化趋势,尤其是冬季干旱站次比和干旱强度分别以-7.79%.(10a)-1^和-0.11.(10a)-1^的倾向率显著减小,干旱减轻趋势在四季中最为显著。     

基于标准降水指标的新疆干旱特征演变

运用标准降水指标 (Standardized Precipitation Index, SPI) 对新疆地区53个雨量站1957—2009年日降水量资料进行全面分析,研究了不同干旱等级发生概率的空间分布变化规律。同时,采用Mann-Kendall趋势检验法分析了各月份标准降水指标值、干旱强度和干旱历时的变化趋势,探讨了新疆地区干旱时空演变特征。结果表明:北疆易发生中等及以上干旱,而南疆易发生轻度干旱。总的来说,北疆干旱强度有下降的趋势,干旱历时趋于缩短,南疆南部干旱强度和干旱历时有轻微上升,东疆中部干旱情况显著恶化。具体来说,北疆冬季干旱程度有减弱趋势,而对于农业生产较重要的春、夏、秋季,西部干旱加剧;南疆夏季干旱有减弱趋势;东疆中部四季干旱程度有轻微加剧趋势。     

Long-term rainfall characteristics in the Mzingwane catchment of south-western Zimbabwe

Rainfall characteristics during the annual rainy season are explored for the Mzingwane catchment of south-western Zimbabwe, for both historic period (1886–1906) and more recent times (1950–2015), based on available daily and monthly precipitation series. Annual and seasonal rainfall trends are determined using the modified Mann-Kendall test, magnitude of trends test and Sen’s slope estimator. Rainfall variability is quantified using the coefficient of variation (CV), precipitation concentration index (PCI) and standard precipitation index (SPI). Results suggest that contemporary mean annual rainfall may not have changed from that measured during the historic period of 1886–1906. However, the number of rainy days (≥ 1 mm) has decreased by 34%, thus suggesting much more concentrated and increased rainfall intensity. A notable shift in both the onset and cessation dates of the rainy season is recorded, particularly during the twenty-first century, which has resulted in a significantly reduced (p < 0.05) length of the rainy season. The combination of a reduced number of rainy days (≥ 1 mm) and a shortened rainy season suggests that long intra-season dry spells have become more common through time and have considerable negative consequences for agriculture and wetland ecosystem in the region. In addition, high spatio-temporal rainfall variability and seasonal PCI values indicate strong seasonality in the rainy season. Based on the SPI results, the El Niño Southern Oscillation (ENSO) strongly influences rainfall variability. The results further suggest high uncertainty in rain season characteristics, which requires effective planning for water needs.     

Drought analysis in the Tons River Basin,India during 1969-2008

The primary focus of this study is the analysis of droughts in the Tons River Basin during the period 1969–2008. Precipitation data observed at four gauging stations are used to identify drought over the study area. The event of drought is derived from the standardized precipitation index (SPI) on a 3-month scale. Our results indicated that severe drought occurred in the Allahabad, Rewa, and Satna stations in the years 1973 and 1979. The droughts in this region had occurred mainly due to erratic behavior in monsoons, especially due to long breaks between monsoons. During the drought years, the deficiency of the annual rainfall in the analysis of annual rainfall departure had varied from ?26% in 1976 to ?60% in 1973 at Allahabad station in the basin. The maximum deficiency of annual and seasonal rainfall recorded in the basin is 60%. The maximum seasonal rainfall departure observed in the basin is in the order of ?60% at Allahabad station in 1973, while maximum annual rainfall departure had been recorded as ?60% during 1979 at the Satna station. Extreme dry events (z score <?2) were detected during July, August, and September. Moreover, severe dry events were observed in August, September, and October. The drought conditions in the Tons River Basin are dominantly driven by total rainfall throughout the period between June and November.     

基于多尺度SPI的中国南方大旱监测

用标准化降水指数(SPI)对2003年南方大旱发生、发展、持续、缓解进行全过程监测。2002年12月—2003年5月中国西南地区东部以及华南南部两广交界一带发生冬春连旱,其中西南地区东部冬旱最为严重,华南南部一带春旱最为严重。入夏以来南方大范围地区6—12月逐月均表现亏水,尤以7、8、10月亏水面积最广,强度最大。2003年6—12月长江以南大范围地区持续夏秋冬三季连旱,旱情极为严重,局部地区出现极端干旱,而长江以北则持续偏涝。2003年3月—2004年2月全年属于典型的"南旱北涝"型分布。基于多尺度SPI进一步统计南方地区1951—2007年历史上严重的夏秋冬季连旱事件。结果表明1980s以前发生过3次,分别是1956、1967、1978年,每11 a出现一次;1980s以后仅2003年发生1次。而这4次连旱的强度却是一次高于一次。     

Evolution of drought severity and its impact on corn in the Republic of Moldova

Droughts in Moldova were evaluated using meteorological data since 1955 and a long time series (1891?C2009). In addition, yields for corn (Zea mays L.), a crop widely grown in Moldova, were used to demonstrate drought impact. The main aim is to propose use of the S _i (S _i-a and S _i-m) drought index while discussing its potential use in studying the evolution of drought severity in Moldova. Also, a new multi-scalar drought index, the standardized precipitation?Cevapotranspiration index (SPEI), is tested for the first time in identifying drought variability in Moldova while comparing it with the commonly used standardized precipitation index (SPI). S _i-m, SPI, SPEI, and S _i-a indices show an increasing tendency toward more intensive and prolonged severely dry and extremely dry summer months. Drought frequency increased through six decades, which included long dry periods in the 1990s and 2000s. Moreover, the evolution of summer evapotranspiration recorded a positive and significant trend (+3.3?mm/year, R ²?=?0.46; p????0.05) between 1955 and 2009. A yield model based on the S _i-a agricultural index and historic corn yields explained 43% of observed variability in corn production when drought occurred in May, July, and August. Increasing severity of the 20-year drought during the critical part of the growing season is raising corn yield losses, as net losses have so far exceeded net gains.     

华北冬小麦-夏玉米两熟区干旱特征分析

研究华北冬小麦一夏玉米主要生长季的干旱时空特征,可为全球气候变暖背景下制定抗旱减灾对策提供理论依据。利用华北5省（市）64个气象台站1961-2010年逐日降水资料,以降水负距平或降水量表征的干旱指标,通过经验正交分解法提取了冬小麦、夏玉米全生育期和关键生长阶段的特征向量和时间系数,分析了干旱频率、站次比及干旱强度的变化特征,并通过构建冬小麦-夏玉米轮作期综合干旱指数,探讨了华北地区农业干旱的总体状况。结果表明：EOF分解的前4个模态提取了60％以上作物干旱的主要时空分布信息,冬小麦主要生长季收敛效果优于夏玉米;冬小麦全生育期、苗期及拔节-抽穗期干旱的高强度中心主要分布在冀中南、豫北及鲁西北地区,而灌浆-成熟期干旱则以豫东为中心;夏玉米全生育期干旱的高强度中心主要位于冀南和鲁北地区,初夏旱以冀北大部为高强度区,而卡脖旱以豫西和鲁南为高强度区。从时间系数和区域干旱强度及站次比的时间变化趋势看,冬小麦全生育期干旱、灌浆-成熟期干旱及夏玉米初夏旱、卡脖旱均表现为递减趋势,但未通过显著性检验,而冬小麦播种期、拔节-抽穗期干旱,以及夏玉米全生育期干旱为不显著的递增趋势。整个冬小麦-夏玉米轮作期干旱威胁较高的地区主要位于京津局部、冀中南、豫北和鲁北等地区。     

Analysis of drought in the region of Abruzzo (Central Italy) by the Standardized Precipitation Index

The paper presents a comprehensive analysis of drought phenomena in the Region of Abruzzo (Central Italy) using the Standardized Precipitation Index (SPI) computed at different time scales (3, 6, 12, 24 months). The study is based on monthly precipitation data collected from 1951 to 2009 at 69 climatic stations uniformly distributed over the region. According to the trend analysis, most stations are characterized by increments in both drought severity and variability, particularly at the longer time scales. A principal component analysis applied to SPI time series enabled to identify two main patterns: the first more correlated to the coastal areas, the second more correlated to the inland, mountainous areas. However, the spatial patterns become less defined as the time scale increases, making more uncertain the definition of homogenous areas to be used in drought management plans. In most cases, the identified drought patterns have similar negative overall tendencies, but different trend directions in some sub-periods. In particular, the first drought pattern is clearly characterized by a trend reversal (from decreasing to increasing) during the last decade. This temporal evolution, consistent with that observed by large-scale analyses in the corresponding (or near) grid points, was not detected for the second pattern, which is probably influenced by local topographic and/or orographic factors. The results confirm the complexity of drought phenomenon in a typical Mediterranean region and the necessity of high-resolution datasets to capture its temporal and spatial variability.     

1960-2011年洞庭湖区年降水量变化特征

以洞庭湖区24个气象站1960-2011年的降水量资料为基础数据,利用气候倾向率、Mann-Kendall突变检验法、小波分析等方法分析了洞庭湖区年降水量的变化特征,并采用正交分解函数EOF、旋转正交分解函数REOF计算了洞庭湖区年尺度的标准化降水指数（SPI）,分析了洞庭湖区的旱涝时空分布特征。结果表明：洞庭湖区年降水量空间上由北向南逐渐增加,时间上没有显著变化趋势。1963年洞庭湖年降水量发生突变。洞庭湖区年降水量存在6a、9a和16-17a振荡周期。洞庭湖区旱涝频繁,极端气候事件有增加的趋势。洞庭湖区年降水量在空间上具有较好的一致性,为普遍干旱或洪涝,但也存在南北反相变化即南部干旱北部洪涝或南部洪涝北部干旱的特点。洞庭湖区年降水量存在南部、西北部和中部3个异常气候区。     

Spatiotemporal variability of drought on a short–medium time scale in the Calabria Region (Southern Italy)

The study analyses spatial and temporal patterns of drought in an area with a wide range of precipitation characteristics (the Calabria region in southern Italy) during the period 1921?C2007. The short-time (2, 3 and 6?months) Standardised Precipitation Index (SPI) was estimated to analyse drought especially from the agricultural point of view. Principal component analysis (PCA) was applied to the SPI to assess the spatial variability of drought. During the period of observation, moderate to severe drought occurred at a frequency of almost 13?% in wet seasons (autumn and winter). Almost half of the region was affected by drought in the years 1981?C1990 when the area experienced its most severe drought. Although the spatial patterns of drought estimated by PCA were logical and consistent with precipitation distribution, very complex patterns were observed for all the time scales looked at. The high fragmentation of the maps obtained makes them of limited value, and caution is recommended in classifying the region into homogeneous areas.     

Drought in the Southern United States over the 20th century: variability and its impacts on terrestrial ecosystem productivity and carbon storage

Drought is one of the most devastating natural hazards faced by the Southern United States (SUS). Drought events and their adverse impacts on the economy, society and environment have been extensively reported during 1895?C2007. Our aim is thus to characterize drought conditions in the SUS and explore the impacts on terrestrial ecosystem function (i.e., net primary productivity (NPP) and net carbon exchange (NCE)). Standard precipitation index (SPI) was used to characterize drought intensity and duration, and a process-based ecosystem model was used to explore the relationship between drought and ecosystem function. Combining overall information on growing-season SPI, drought area and duration, we concluded there was no significant change in drought conditions for the SUS during 1895?C2007. However, increased drought intensity was found for many areas in the east, resulting in significant decreases in NPP for these areas, with the largest decrease up to 40% during extreme droughts. Changes in precipitation patterns increased C emissions of 0.16 Pg (1 Pg?=?10¹⁵?g) in the SUS during 1895?C2007. The west (dry region) acted as a C sink due to increased precipitation, while the east (water-rich region) acted as a C source due to increased drought intensity. Both NPP and NCE significantly increased along a gradient of declining drought intensity. Changes in precipitation resulted in C sources in forest, wetland, and cropland ecosystems, while C sinks in shrubland and grassland ecosystems. Changes in air temperature could either enhance or reduce drought impacts on NPP and NCE across different vegetation types.     

Trends in evaporation of a large subtropical lake

In order to further investigate the capability of the Standardized Precipitation Index (SPI) to identify flood/drought events, monthly precipitation data from 26 precipitation stations and monthly discharge data from four hydrological stations from 1960 to 2006 in the Minjiang River basin were used to analyze the correlations between multiple time scales of the SPI and river discharge. The SPI series that had a maximum correlation with discharge was chosen to detect flood/drought events in the basin, and the results were compared to historical flood/drought events. The results indicated the following. (1) High Pearson correlations between the SPI and discharge were identified at shorter time scales (1 to 3 months), and the maximum correlation was found on the time scale of 2 months. (2) Five floods among the six largest historical flood events in the Minjiang River basin were identified with the 2-month SPI, but the SPI does have shortcomings in identifying more general floods. The SPI also identified major drought events that were consistent with historical data. This demonstrates that the 2-month SPI is an effective indicator for the identification of major flood/drought events in the Minjiang River basin.     

干旱指数在山西逐日监测中的适用性研究

综合气象干旱指数(CI)和标准化降水指数(SPI)在逐日监测中往往会出现干旱突然加重的现象,这是由于某时段内每日降水量对当前干旱的发展贡献是等权重的。本文基于线性递减非等权重的方法对CI进行了修正,同时对加权降水量(WAP)进行了标准化(Standard WAP Index,SWI)。以山西为例,通过对比CI修正前后,即CI和CI_new(CI修正后),与SPI和SWI在不连续加重现象(UED)的总体分布、典型事例干旱演变特征以及与土壤湿度相关性等方面的差异,分析了4种干旱指数对山西逐日干旱演变的监测能力。结果表明:1)CI_new出现UED的次数较CI有了明显下降,SWI出现UED的次数也比SPI有了大幅的减少,且SWI在这4种指数中是出现UED次数最少的指数;2)CI_new和SWI较CI和SPI与同期土壤湿度的相关性均有所提高,表明修正后的CI_new和SWI更加符合土壤湿度的变化,更能反映土壤干旱的演变规律。针对干旱发展过程中不连续加重的现象,通过非等权重方法有效地减少了该现象的发生。     

Observed changes of drought/wetness episodes in the Pearl River basin, China, using the standardized precipitation index and aridity index

Monthly precipitation data of 42 rain stations over the Pearl River basin for 1960–2005 were analyzed to classify anomalously wet and dry conditions by using the standardized precipitation index (SPI) and aridity index (I) for the rainy season (April–September) and winter (December–February). Trends of the number of wet and dry months decided by SPI were detected with Mann-Kendall technique. Furthermore, we also investigated possible causes behind wet and dry variations by analyzing NCAR/NCEP reanalysis dataset. The results indicate that: (1) the Pearl River basin tends to be dryer in the rainy season and comes to be wetter in winter. However, different wetting and drying properties can be identified across the basin: west parts of the basin tend to be dryer; and southeast parts tend to be wetter; (2) the Pearl River basin is dominated by dry tendency in the rainy season and is further substantiated by aridity index (I) variations; and (3) water vapor flux, moisture content changes in the rainy season and winter indicate different influences of moisture changes on wet and dry conditions across the Pearl River basin. Increasing moisture content gives rise to an increasing number of wet months in winter. However, no fixed relationships can be observed between moisture content changes and number of wet months in the rainy season, indicating that more than one factor can influence the dry or wet conditions of the study region. The results of this paper will be helpful for basin-scale water resource management under the changing climate.     

基于SPI与相对湿润度指数的1961-2009年东北地区5-9月干旱趋势分析

依据东北地区1961-2009年71个气象台站月平均气温、降水资料,运用标准化降水指数（SPI）与相对湿润度指数等干旱指标分析了东北地区5-9月的干旱趋势。结果表明：1961-2009年,东北大部分地区在5-9月呈干旱化趋势,仅在黑龙江大兴安岭北部、黑龙江西南部以及黑龙江与吉林的东部交界处表现为湿润化;东北三省干湿震荡主要周期大约为22-24a,近49a发生了4次干湿交替,突变年为1976及1996年。就干旱发生范围而言,近49a东北地区干旱面积呈上升趋势,以1996年为分界线,农作物干旱受灾比在吉林增幅最大,辽宁次之,黑龙江最小,采用SPI与相对湿润度指数评价东北地区干旱较符合实际。就干旱发生频率而言,高值区主要集中在东北西部,特别是黑龙江的齐齐哈尔与大庆地区、吉林的白城地区及辽宁的朝阳地区。干旱与极端干旱的发生频率在1981-1990年较低,在2001-2009年最高,而极端干旱发生频率增加幅度明显高于一般干旱。     

Spatiotemporal patterns of drought at various time scales in Shandong Province of Eastern China

The temporal variations and spatial patterns of drought in Shandong Province of Eastern China were investigated by calculating the standardized precipitation evapotranspiration index (SPEI) at 1-, 3-, 6-, 12-, and 24-month time scales. Monthly precipitation and air temperature time series during the period 1960–2012 were collected at 23 meteorological stations uniformly distributed over the region. The non-parametric Mann-Kendall test was used to explore the temporal trends of precipitation, air temperature, and the SPEI drought index. S-mode principal component analysis (PCA) was applied to identify the spatial patterns of drought. The results showed that an insignificant decreasing trend in annual total precipitation was detected at most stations, a significant increase of annual average air temperature occurred at all the 23 stations, and a significant decreasing trend in the SPEI was mainly detected at the coastal stations for all the time scales. The frequency of occurrence of extreme and severe drought at different time scales generally increased with decades; higher frequency and larger affected area of extreme and severe droughts occurred as the time scale increased, especially for the northwest of Shandong Province and Jiaodong peninsular. The spatial pattern of drought for SPEI-1 contains three regions: eastern Jiaodong Peninsular and northwestern and southern Shandong. As the time scale increased to 3, 6, and 12 months, the order of the three regions was transformed into another as northwestern Shandong, eastern Jiaodong Peninsular, and southern Shandong. For SPEI-24, the location identified by REOF1 was slightly shifted from northwestern Shandong to western Shandong, and REOF2 and REOF3 identified another two weak patterns in the south edge and north edge of Jiaodong Peninsular, respectively. The potential causes of drought and the impact of drought on agriculture in the study area have also been discussed. The temporal variations and spatial patterns of drought obtained in this study provide valuable information for water resources planning and drought disaster prevention and mitigation in Eastern China.