Comparison of trends and frequencies of drought in central North China and sub- Saharan Africa from 1901 to 2010

This study compares the trends and frequencies of drought between central North China(CNC) and(SSA) for the periods 1901–2010 and 1951–2010. The Standardized Precipitation Evapotranspiration Index(SPEI) and Self-Calibrating Palmer Drought Severity Index(sc-PDSI) are used to assess the drought trends and frequencies. In general, the results exhibit downward trends of drought index values and upward trends of drought frequencies over CNC and SSA. A high rate of the trends' slopes for the drought index and a low rate of the frequencies' slopes is found over CNC with respect to SPEI and sc-PDSI. Furthermore, some abrupt changes are revealed after applying the sequential Mann–Kendall test to detect change points. These findings offer insight into the trends and frequencies of drought over the regions studied. Further analysis needs to be undertaken to understand the mechanisms underlying the occurrence of drought in these areas.

Simulation of Change Trend of Drought in Shaanxi Province in Future Based on PRECIS Model

[Objective] The aim was to predict the change trend of drought in Shaanxi Province in future. [Method] Based on the regional climate model PRECIS from Hadley Climate Center, British Meteorological Bureau, taking precipitation anomaly percentage as assessment index, the change trend of drought in Shaanxi Province in reference years (1971-1990) was simulated, and the change trend of drought in Shaanxi Province from 2071 to 2100 was predicted. [Result] The simulated value of drought frequency in reference years could simulate the distribution of drought well, namely drought frequency was high in the north and low in the south; annual mean frequency of drought above second grade decreased gradually from north to south in future, and it was the highest in northern Shaanxi (above 4 times) and lowest in southern Shaanxi (below 2.5 times); drought frequency in future went down in northern Shaanxi from southern Yulin to Yan’an, eastern Guanzhong (including Weibei) and the west of southern Shaanxi, while it went up in the north of northern Shaanxi, Qinling Mountains and Shangluo region in western Guanzhong. [Conclusion] The study could provide theoretical references for the research on the change trend of drought in Shaanxi Province in future.

Variation of drought over northern China during 1950-2000

Based on China's monthly precipitation data of 629 stations during 1950-2000, we calculated Z indices and separated them into seven Dryness and Wetness grades. Further, a drought area index was proposed to study changes in drought severity in northern China. The results revealed that the different severity of droughts all showed expanding trends in northern China's main agricultural area. Moreover, the area coverage of droughts in different seasons and different regions displayed different trends.

Analysis on Agricultural Drought Degree in Crop Growth Season in Recent 50 Years in Xinmin,Liaoning Province

By means of the analysis methods of linear regression,climate tendency rate,integral humidity index and dry-wet index,precipitation,agricultural water demand and drought degree were analyzed systematically.The results showed that precipitation tendency rate in crop growing season was-19.983 mm/10 a in recent 50 years,and precipitation reduced by around 100 mm.60%-70% years had basically satisfactory precipitation and the satisfaction degree of natural precipitation towards agricultural water demand decreased by 23%.Due to precipitation decrease,climatic type changed from semi-humid and relative drought to moderate drought.The average water deficit was 56 mm in growth season and 36% years were affected by drought.Spring drought was the most serious with the probability of 64%,followed by autumn drought with the probability of 58%,and summer drought was the lightest with the probability of 24%.The drought probability from planting to seedling emergence in May was 70%,which had the greatest effect on agriculture production.

Application of Drought-resistant Varieties in Urban Green Spaces

As the connotations of urban green spaces and urban eco-green spaces have been more realized,drought-resistant green spaces have become a unique development trend,and drought-resistant flowers have been more applied in green spaces.This paper summarized characteristics of drought-resistant flowers,foreign and domestic researches in this field,advantages and disadvantages of their application in urban green spaces,and proposed key directions of the future researches.

Current Situation and Evolution of Drought and Flood in Fen-wei Plain

Based on the latest results and data of drought and flood in Fen-wei Plain, current situation and evolution of drought and flood in Fen-wei Plain were analyzed. The results show that in Fen-wei Plain drought and flood are natural disasters bringing about the most serious damage, and drought risk in east central Weihe Plain is serious. In Fen-wei Plain, precipitation tended to decrease, and temperature, drought days and intensity increased over the past 50 years. There were obvious differences between two decades in drought and flood. Drought was the severest in the 1990s, and flood was the most serious in Fenhe Plain in the 1960s and in Weihe Plain from the late 1970s to the early 1980s. Over the past ten years, precipitation and flood frequency increased, and temperature, drought days and intensity decreased. In Fen-wei Plain, temperature will rise and precipitation will increase slightly in next 20 -40 years. Monitoring and early warning capability of drought and flood in Fen-wei Plain have im- proved gradually, but some issues need to be paid more attention to and solved.

Drought Monitoring and Assessment of Climate Parameters Variability in Koutiala and San Districts, Mali

In Mali, the annual temperature, rainfall, and evapotranspiration are high variables. Their distributions are unevenly spread from north to south. Climate change strengthens to increase air temperature and evapotranspiration. It also increases the intense rainstorms and the risk of drought associated heat waves. Drought is considered a natural disaster among all hydrologic extremes. It causes severe damage to the environment, agriculture, and livelihoods relying on water resources. The present study evaluated the variation of drought indices from 1989 to 2019 in Koutiala and San districts, respectively. Therefore, the Standardized Precipitation Evapotranspiration Index (SPEI) was applied. Hence, the Mann-Kendall (MK) test was used and for 12-month time-scales. Trend analysis of monthly precipitation, temperature, and evapotranspiration has been done by using the MK test. Based on the analysis result, the climate of the Koutiala and San districts has been classified as moderate to severe drought category. However, this result clearly shows SPEI pattern changes in both districts. The monthly precipitation showed a significant decreasing trend in Koutiala and San districts. In comparison, the monthly temperature and evapotranspiration displayed an increasing trend in both districts.

基于CMIP6耦合WRF的黄河上游复合干旱热浪事件演变规律

复合干旱热浪事件较传统极端气候事件破坏性更强,近年来在全球范围内发展迅速,黄河上游作为气候敏感区受其影响尤其突出,刻画其特征并分析未来可能气候条件下的演变趋势对事件防控有重要意义。本文提出了一种基于第六次国际耦合模式比较计划CMIP6耦合天气预报研究模式WRF的未来气象数据动力降尺度方法。识别了黄河上游不同情景下的复合干旱热浪事件及其特征,揭示了复合事件与单一事件的区别,分析了复合干旱热浪事件的未来演变规律。结果表明:(1)历史期、SSP245和SSP585情景下复合干旱热浪事件较单一事件的温度升高3.8%、13.1%、13.5%,干旱指数降低5.8%、2.6%、2.6%,极端特征更加显著。(2)SSP245情景下复合干旱热浪事件特征呈西南高、东北低的空间分布形式,而在SSP585情景下以北部、东部区域分布最高。(3)未来各情景下区域整体复合干旱热浪事件特征呈显著上升趋势,其中SSP585的上升趋势高于SSP245。

基于叶绿素荧光遥感的中国西南耕地干旱响应研究

在全球变暖的背景下,干旱对农业生产造成了严重影响,研究农作物产量对干旱的响应对维护粮食安全至关重要。中国西南地区地貌复杂,受降水、水汽水平和垂直输送等因素影响,干旱频发。采用太阳诱导叶绿素荧光(SIF)卫星遥感数据和自校准的帕尔默干旱严重程度指数(sc_PDSI)对2001~2022年中国西南耕地区域的干旱进行了识别,并分析了粮食产量对干旱的响应,结果显示:中国西南耕地在2003年、2006年、2007年及2009~2014年间遭受了干旱,其中2011年8月和9月干旱最为严重,sc_PDSI值分别为-2.61和-2.52;2001~2022年中国西南作物GOSIF呈显著增加趋势(+0.0026 W/m2μm·sr·yr,p<0.05);粮食产量与GOSIF、scPDSI均显著相关,但GOSIF的相关系数高于sc_PDSI,说明GOSIF能更准确地反映作物产量动态。本研究成果对于区域干旱的空间特征、演化趋势以及因干旱产生的粮食产量损失估计具有重要参考价值。

基于温度植被干旱指数的关中地区旱情监测

及时准确地进行区域尺度的干旱监测对于保障农业生产和保护粮食安全具有重要指导意义。该研究基于2001—2020年的MOD11A2地表温度8 d合成产品与MOD13A1植被指数16 d合成产品,通过地表温度(land surface temperature,LST)和归一化植被指数(normalized difference vegetation index,NDVI)数据构建NDVI-LST特征空间,获取关中地区2001—2020年20 a时间序列的温度植被干旱指数(temperature vegetation dryness index,TVDI),分析关中地区干旱时空分布演变特征和干旱影响成因,探索其未来演变趋势。结果表明:1)关中地区近20 a来TVDI平均值为0.57,干旱类型整体上属于正常的干旱状态,82.00%的地区干旱变化状况为稳定不变,渭河冲积平原干旱程度较为严重,其次是渭北旱塬地区,南部秦岭地区较为湿润;2)关中地区未来干旱情况有所缓解,7.71%的研究区将持续变湿,36.24%的地区由干变湿;3)关中地区的TVDI值与海拔、坡度、降水量呈现负相关,与气温呈现正相关关系,林地、草地覆盖对缓解干旱具有积极意义。温度植被干旱指数从区域尺度上实现了干旱状况的定量化表征,在关中地区具有较好的适用性,遥感干旱监测结果可为关中地区抗旱对策的制定提供理论基础和科学依据。

基于温度植被干旱指数的西北干旱区干旱时空变化

西北干旱区常年降雨稀少、干旱频繁,严重影响当地的生态平衡、农业生产以及经济可持续发展。为厘清西北干旱区干旱时空分布特征,基于增强型植被指数(enhanced vegetation index,EVI)和地表温度(land surface temperature,LST)构建温度植被干旱指数(temperature vegetation dryness index,TVDI)模型获得2000—2022年6—9月西北干旱区干旱时空变化特征,利用Sen+Mann-Kendall趋势分析法明确干旱趋势,分析不同土地利用类型与干旱的关系。结果表明:①西北干旱区TVDI空间分布呈现“西北低东南高”的特征,多年TVDI的均值为0.67,处于中旱的水平;②西北干旱区TVDI呈干旱加剧趋势,增加速率为8.8×10^(-4)年^(-1),显著加剧的面积约占总面积的21.04%,轻微加剧的面积约占总面积的62.33%;③未利用地TVDI值均高于其他土地类型,干旱程度越高未利用地对TVDI贡献度越大。

曼谷地区干旱灾害风险分布及变化趋势分析

基于自然灾害风险评估理论,依据致灾因子危险性、承灾体的脆弱性,综合评估曼谷节点地区的干旱灾害风险。进而分析2000—2020年曼谷干旱灾害危险性、脆弱性和风险的空间分布特征和变化趋势。结果表明:1)曼谷干旱危险性在地区间存在差异,符合“北高南低”的规律。高脆弱性地区集中在曼谷都市区中部、佛统府西北部和沙没巴干府西部,与自然条件、人口和经济分布以及城市活动有关。曼谷干旱风险较高,中等及以上干旱灾害风险土地占总面积的41.64%,佛统府西北部和巴吞他尼府中部具有最高风险,同时具有较高的脆弱性和危险性。2)曼谷的风险性、脆弱性和危险性均呈线性上升趋势。巴吞他尼府和佛统府的危险性,佛统府西北部和曼谷中部城乡居民用地的脆弱性,以及佛统府西北部和、巴吞他尼府中部和曼谷都市区中部的干旱风险程度上升较快。3)M-K检验结果显示,曼谷危险性和风险均呈现“东升西降”的空间分布特征,但变化趋势均不显著。曼谷的脆弱性在大部分地区呈极显著上升趋势,沙没沙空府的脆弱性上升趋势最为显著,达到71.23%。4)曼谷的干旱灾害风险程度由危险性和脆弱性共同决定,一元线性线性回归分析结果与M-K检验分析结果在空间分布上存在明显差异,但都表明需采取措施降低脆弱性以降低城市干旱灾害风险。利用精细尺度的空间数据进行分析可以更准确反映该地区的资源管理能力,提高风险评估的合理性,为节点城市的灾害风险管理和风险分布研究提供有价值的参考。

大连地区干旱特征及变化趋势分析

为探究气候变化背景下大连市干旱特征及变化趋势,基于2007~2023年大连市80个区域自动气象站和1964~2023年6个国家气象站的气象数据,使用相对湿润度指数探讨分析了大连市干旱的时序变化趋势、空间分布规律及概率分布特征。结果表明:(1)大连市干旱主要以轻旱为主,发生轻旱的区域主要分布于瓦房店、旅顺和大连市区。相对湿润的区域为东北部地区,相对干旱的区域为西北部地区和旅顺、市区及长海的部分地区。春季以轻旱和中旱为主,瓦房店、旅顺、市区和金普新区的部分地区为中旱,庄河、普兰店和长海大部为轻旱。秋季庄河和普兰店的部分区域为无旱,其他大部分地区以轻旱为主。(2)干旱发生频率较低的区域基本在庄河地区,干旱发生频率较高的地区基本在瓦房店西北部及大连市南部地区的大部分区域。(3)近60年大连市相对湿润度指数呈显著上升趋势,即干旱程度显著减弱。春季、秋季及冬季相对湿润度指数均出现显著上升趋势,干旱显著减弱。(4)近60年大连市的相对湿润度在2002~2003年开始了突变,在2012~2014年发生了突变。(5)近60年大连市无旱年占45%,轻旱年占52%,中旱年占3%,无重旱及特旱年。

1980—2022年我国骤旱特征及趋势分析

在气候变化背景下,骤旱事件频发,可在短期内对农业生产和生态系统功能造成巨大影响。因此全面准确掌握我国骤旱特征和变化趋势,对我国干旱风险评估和精准化农业减灾等具有重要意义。本文利用长时间序列陆面模型数据与再分析数据集,分别采用基于蒸发胁迫比和土壤水分的判别方法,对1980—2022年我国骤旱的发生频次、骤旱烈度、持续时间和时空分布等特征进行综合量化分析,并采用趋势分析方法评估不同区域的发展趋势,以全面准确分析我国骤旱特征与发展趋势。结果表明:(1)两种方法均表明我国夏季骤旱频次最高,冬季最低;(2)两种方法识别出的骤旱范围在东南地区较为一致,而在西北地区存在较大差异;(3)基于蒸散发的方法识别出的场次最高的地区为青藏高原地区,基于土壤水分的方法为四川中部地区;(4)骤旱平均持续时间多为6~10候,基于蒸散发的方法识别出西北地区较高,基于土壤水分方法识别出西北部和中部部分地区较高;(5)基于蒸散发的方法显示骤旱烈度较高的地区为东北地区、西北地区、西藏自治区和台湾地区;基于土壤水分方法显示南方地区骤旱烈度较高。两种方法结果存在明显差异,其阈值选取及区域适用性仍有待深入研究。

1976—2020年弥河流域旱涝急转特征分析

基于弥河流域13个雨量站1976—2020年的逐日降水数据,使用长周期旱涝急转指数(LDFAL)、短周期旱涝急转指数(SDFAL),通过Mann-Kendall趋势检验、Mann-Kendall突变检验、滑动T检验、重标极差分析法(R/S分析法)、小波分析法、反距离插值法对弥河流域旱涝急转的时空分布特征进行分析。结果表明:在45 a内,弥河流域长周期6—9月共发生18次旱涝急转现象,LDFAL呈现下降趋势,表明未来“旱转涝”现象将占据主导。SDFAL在6—7月和8—9月呈现上升趋势,表明未来“涝转旱”现象将占据主导;7—8月呈现下降趋势,表明未来“旱转涝”现象将占据主导。LDFAL与旱涝急转强度均未发生突变,SDFAL只在2007年6—7月发生突变,短周期旱涝急转强度在2007年的6—7月和2005年的7—8月发生突变。长周期旱涝急转现象变化存在11 a主周期,短周期6—7月、7—8月、8—9月的变化主周期分别为34、64、43 a。

陕北黄土丘陵区主要作物需水量变化趋势及其应对策略

[目的]探讨陕北黄土丘陵区干旱、降雨和主要作物需水量在过去及未来的变化趋势,以期掌握该区气象干旱变化特征及主要作物水分供需状况,为该区主要作物合理灌溉及优化种植提供参考。[方法]基于陕北黄土丘陵区1980—2017年日尺度基本气象数据,采用去趋势预置白处理的Mann-Kendall法和R/S法分析了过去及未来作物生育期内(4—10月份)的干旱、降雨及作物需水量变化趋势。[结果](1)干旱年发生频率达56.76%,干旱在4—6月呈现降低趋势,在7—10月份呈现增加趋势;有效降水量的变化趋势在不同地区的月份表现各异;作物需水量在4—8月呈增加趋势。(2)作物未来生育期内,陕北黄土丘陵区有效降水量分别在5月、7月、10月份呈现降低趋势,在8月、9月份为增加趋势;干旱及作物需水量在4—6月份延安地区分别呈现增加和降低趋势,榆林地区同期干旱及作物需水量与延安地区相反。[结论]陕北黄土丘陵区干旱频发,有效降雨量难以满足作物需水量。建议控制红枣及苹果种植面积,加大谷子产业投入,利用覆盖与集雨补灌结合的方法来满足作物对水分的需求,达到增产增收目的,助力新时代乡村振兴。

Characterizing Rainfall of the Great Kei River Catchment, Eastern Cape Province, South Africa

This study seeks to understand long-term changes of rainfall for the Great Kei River catchment (GKRc) in South Africa for water resources management and planning. Monthly and annual rainfall time series data from 1950 to 2017 for 11 rainfall gauging stations are analyzed using various statistical methods. Data obtained from South African Weather Services (SAWS) was quality controlled to enable the use of Mann-Kendall (MK), Theil Sen’s method, Precipitation Concentration Index (PCI), among others to characterise rainfall. Rainfall in the catchment is seasonal (particularly wet in spring and summer) and highly variable with a PCI of 17.2. Years which received rain above and below the mean inter-annually were 46% and 54%, respectively. Seasonality trends also confirm that the GKRc has been progressively receiving less rainfall since 1950, especially in the autumn. The methods are novel in understanding historical and existing trends, variability and characteristics that control freshwater availability in this catchment.

我国夏季降水的年代际变化及华北干旱化趋势

利用１９５１ ～１９９４ 年全国３３６ 个测站夏季（６～８ 月） 降水和太平洋海表面温度资料来分析我国夏季降水的年代际变化及华北地区干旱化趋势。分析结果表明：我国夏季降水在１９６５ 年前后发生了一次气候跃变，华北地区从１９６５ 年后夏季降水明显减少，干旱化的趋势明显，这种趋势与西非萨赫尔地区干旱化的趋势相似； 分析结果还表明我国８０ 年代的气候与７０年代的气候有较大差别，这种差别表现在长江、淮河流域从７０ 年代末起降水增多，涝灾明显增多，而华南和华北在８０ 年代降水明显比７０ 年代少， 干旱趋势加重。然而，从９０ 年代中期开始，华北地区北部的降水有增多的趋势。上述所发生的气候变化可能主要是由于６０ 年代中期和从８０ 年代到９０ 年代初赤道东、中太平洋海表温度明显增加，而在７０ 年代明显降低所造成。这种现象似如年代际的“ＥＮＳＯ 循环”现象，它对全球和我国气候变化有较大影响，特别对华北地区干旱化趋势有很大影响。然而从９０ 年代中期开始，赤道中、东太平洋海温有下降的趋势，这有利于华北降水的增多。

基于标准化降水蒸散指数的华南干旱趋势研究

最近几年华南地区干旱频发,为探讨该地区的干旱趋势,用标准化降水蒸散指数(SPEI)和1961-2010年华南地区具有代表性的50个站点的月降水及月平均气温资料,分析了该地区近50年来的干旱趋势、干旱空间分布、极端干旱事件发生频次和干旱持续时间。结果表明,华南地区普遍存在干旱事实,最近10年是干旱最严重的10年,Mann-Kendall检验表明该地区平均SPEI指数从1998年开始突变;干旱化最严重的区域是海南岛、广西南部和西部地区,广东的干旱化趋势最轻。20世纪70年代干旱和极端干旱事件较少,其后明显增多,干旱持续时间也有所延长。由于该地区降水呈现弱增加趋势而温度升高显著,因此推测温度升高导致蒸散增加可能是华南地区干旱化的主要原因。另外,降水频次的减少和集中也是导致近来极端干旱事件增多的原因之一。SPEI指数较好地体现了气候变暖导致的干旱化趋势。

基于标准化降水蒸散指数的中国干旱趋势研究

标准化降水蒸散指数(SPEI)通过标准化潜在蒸散与降水的差值表征一个地区干湿状况偏离常年的程度,是分析干旱演变趋势的新理想指标,目前已经广泛应用于干旱评估、水资源管理等领域。用SPEI和1951—2009年中国区域160个站的月降水量及月平均气温资料,对中国59年来干旱化的空间分布、四季干旱趋势变化和全国极端干旱事件发生频次进行了分析,并定性分析了干旱发生的原因。结果表明,我国普遍存在干旱化的事实,西部、华北和东北地区干旱化最为显著。我国四季均呈现干旱化趋势,其中春、秋季干旱化趋势明显,夏季最近15年都处于干旱状态,但干旱化趋势未通过0.05显著性检验;另外全国极端干旱事件发生频率明显增多。东北和华北地区的降水呈现轻微减少趋势,而温度升高趋势明显,降水和温度的共同作用导致了明显的干旱化。四川盆地温度升高趋势不显著,但降水减少显著,降水较少是导致四川盆地干旱化的主要原因。降水频率的减少和集中也导致近几年极端干旱事件明显增多。我国普遍的干旱化趋势和明显增多的极端干旱事件可能对我国经济发展产生阻碍。