Ranking Regional Drought Events in China for 1960-2009

The spatiotemporal variations of the site and regional droughts in China during 1960–2009 were analyzed by applying a daily composite-drought index （CDI） to 722 stations in China's Mainland. Droughts frequently happened in a zone extended from Southwest China to the Yellow River, North China, and the southwestern part of Northeast China, with two centers of high frequency in North China and Southwest China. In Southwest and South China, droughts tend to happen during the winter. In North China and along the Yellow River, droughts mainly occur during the winter and during May–June. During the past 50 years, the geographical distribution of site drought events showed high frequencies （0.9–1.3 times per year） in the upper Yellow River basin and North China, comparing with moderate frequencies （0.6–0.9 times per year） in Southwest China and the southwestern part of Northeast China and with lower frequencies over the middle and lower Yangtze River basin. And the frequencies increased over China's Mainland except for the upper reaches of the Yangtze River. A regional drought （RD） event is a widespread and persistent event that covers at least five adjacent sites and lasts for at least 10 days. There were 252 RD events in the past 50 years—five times per year. Most RD events lasted for 100 days and covered 100 stations, but the longest and largest RD event lasted for 307 days from 6 September 1998 to 9 July 1999 and covered 327 stations from North to Southwest China.

DIAGNOSTIC ANALYSIS OF PERSISTENT DROUGHT/FLOOD EVENTS IN SUMMER OVER THE TWO-LAKE REGION OF CHINA

Based on the daily regional mean rainfall,the Z-index method is used to identify persistent flood and drought events lasting for at least 10 days over a region where Dongting Lake and Poyang Lake sit(referred to as the"two-lake region"hereafter).The National Centers for Environmental Prediction(NCEP)reanalysis data are then utilized to perform a preliminary diagnostic analysis on these events.The results indicate that the composite standardized geopotential height at 500 hPa presents two different meridional wave trains from north to south over the East Asian-Pacific region,i.e.,a"-+-"pattern for the droughts and a"+-+"pattern for the floods,respectively.The developing,maintaining and decaying phases in the drought and flood events are closely related to the intensity and location of a subtropical high and an extra-tropical blocking high.It is shown that the East Asian summer monsoon is strong(weak)with the occurrence of persistent drought(flood)events.Droughts(floods)are accompanied by a weak(strong)tropical convergent system and a strong(weak)subtropical convergent system.Furthermore,the persistent drought(flood)events are associated with a divergence(convergence)of vertically integrated water vapor flux.In the vertical profile of water vapor flux,divergence(convergence)in the mid-and lower-levels and convergence(divergence)in the higher levels are evident in the droughts(floods).Both the divergence in the droughts and the convergence in floods are strongest at 850 hPa.

Impacts of Upper Tropospheric Cooling upon the Late Spring Drought in East Asia Simulated by a Regional Climate Model

Responses of late spring （21 April 20 May） rainfall to the upper tropospheric cooling over East Asia are investigated with a regional climate model based on Laboratoire de M6t6orologie Dynamique Zoom （LMDZ4-RCM）. A control experiment is performed with two runs driven by the mean ERA-40 data during 1958-1977 and 1981 2000, respectively. The model reproduces the major decadal-scale circulation changes in late spring over East Asia, including a cooling in the upper troposphere and an anomalous meridional cell. Accordingly, the precipitation decrease is also captured in the southeast of the upper-level cooling region. To quantify the role of the upper-level cooling in the drought mechanism, a sensitivity experiment is further conducted with the cooling imposed in the upper troposphere. It is demonstrated that the upper-level cooling can generate the anomalous meridional cell and consequently the drought to the southeast of the cooling center. Therefore, upper tropospheric cooling should have played a dominant role in the observed late spring drought over Southeast China in recent decades.

Risk Regionalization of Drought for Flue-cured Tobacco Planting in Qujing City Based on GIS

The risk regionalization of drought for flue-cured tobacco planting in Qujing City was studied to provide reference for drawing on advantages and avoiding disadvantages in flue-cured tobacco planting,disaster reduction,and disaster relief services.According to the production practice of flue-cured tobacco and local climate analysis,the risk of disaster-causing factors,sensitivity of disaster-breeding environment,vulnerability of carriers,and disaster prevention and reduction capability were analyzed and evaluated quantitatively.Secondly,starting from the formation mechanism of drought,a risk assessment model of the meteorological disaster was established by GIS technology.Finally,the risk assessment and regionalization of drought in the critical periods for drought-stricken flue-cured tobacco (transplanting period,root extending stage and vigorous growth period) in Qujing City were carried out.The results showed that in Qujing City,the risk areas of drought for flue-cured tobacco planting were divided into five grades in the transplanting period and six grades in the root extending stage and vigorous growth period.

Regional Evaluations of the Meteorological Drought Characteristics across the Pearl River Basin, China

Regional evaluation of drought characteristics provides critical information for water resource management. In this case, this study attempts to analyze the probability behaviors of drought events of a given severity in the Pearl River Basin and to construct severity-area-frequency curves of drought events. Due to possible impacts of complicated topographical properties and diverse climate types within the Pearl River Basin, the entire Pearl River Basin is subdivided into different homogeneous regions. In general, the Pearl River Basin can be categorized into four homogeneous regions, and the severity-area-frequency analysis results for the short-, medium- and long-term drought episodes within each homogeneous regions indicate stressful challenge for the water resource management in the Pearl River Basin due to the fact that severe droughts usually occur over the entire Pearl River Basin. Meanwhile, the Pearl River Delta will face a higher risk of drought when compared to other regions of the Pearl River Basin in terms of the medium-term drought. The Pearl River Basin is highly economically development and is heavily populated, thus impacts of droughts and related resilience resolutions or policies should be taken into account in the formulation of regional sustainable development of water resources and socio-economy within the Pearl River Basin, China.

PRELIMINARY STUDY ON THE FLOODING AND DROUGHT CLAMITY DURING PAST 1500 YEARS IN THE HAI′AN REGION，JIANGSU PROVINCE

Collection and arrangement of the historical records of climatic changes and environment evolution,espectial-lyin the aspect of calamities,are made on the history documents of past 1500 years about Haiˊan region,Jiangsu Province.There existed two obvious flooding-drought frequently-occurring periods:one was from 1550 AD to 1850 AD and another was 100 AD to 1200AD.The period of 1550 AD to1850 AD is interrupted by two relatively arid and cold climatic periods:one was from 1630 AD to 1700 AD and another was 1750 AD to 1820 AD.The main characteristic of the calamity periods is that they occurred by turns,and sometimes,both drought and flooding occurred in the same year.The instability of the climatic changes in the Little Ice Age may be the main reason of the frequently-occurring flooding and drought in Haiˊan region.Research results also show that the frequently-occurring periods of flooding and drought is in close relationship with the solar activity,and therefore,occurrence of the flooding and drought may be in relation with the intensity of the solar activity.This hypothesis may need further study in the future.

Dryness-wetness change and regional differentiation of flood-drought disasters in Guangdong during 1480-1940AD

Based on the historical records of the drought and flood disasters during 1480-1940AD, this paper reconstructs the sequences of wetness index （WI） and drought and flood disasters. We find a good identical relationship between the fluctuation of WI sequence and the δ^18O record of the GISP2 ice core in Greenland, which shows an apparent monsoonal disposal pattern of moisture and temperature. By applying the Morlet Wavelet Transform Method to deal with the data, several apparent periodicities, such as 7-8a, 11-15a, 20-23a and ca 50a, are revealed, among which some can be attributed to the solar forcing. Based on results of Cluster Analysis of dry-wet changes, we resume the regional differentiation pattern of flood-drought disasters all over Guangdong during different climatic intervals in the LIA and, find the western and northern parts of Guangdong have undergone drastic changes in drought-flood regional differentiation, but the eastern part is relatively stable, and the area of the Pearl River Delta shows stable condition of more flood disasters.

Regional Climate Index for Floods and Droughts Using Canadian Climate Model (CGCM3.1)

The impacts of climate change on the discharge regimes in New Brunswick (Canada) were analyzed, using artificial neural network models. Future climate data were extracted from the Canadian Coupled General Climate Model (CGCM3.1) under the greenhouse gas emission scenarios B1 and A2 defined by the Intergovernmental Panel on Climate Change (IPCC). The climate change fields (temperatures and precipitation) were downscaled using the delta change approach. Using the artificial neural network, future river discharge was predicted for selected hydrometric stations. Then, a frequency analysis was carried out using the Generalized Extreme Value (GEV) distribution function, where the parameters of the distribution were estimated using L-moments method. Depending on the scenario and the time slice used, the increase in low return floods was about 30% and about 15% for higher return floods. Low flows showed increases of about 10% for low return droughts and about 20% for higher return droughts. An important part of the design process using frequency analysis is the estimation of future change in floods or droughts under climate scenarios at a given site and for specific return periods. This was carried out through the development of Regional Climate Index (RCI), linking future floods and droughts to their frequencies under climate scenarios B1 and A2.

Drought fluctuations based on dendrochronology since 1786 for the Lenglongling Mountains at the northwestern fringe of the East Asian summer monsoon region

The Lenglongling Mountains （LLM） located in northeastern part of the Tibet Plateau, belong to a marginal area of the East Asian summer monsoon （EASM） and are sensitive to monsoon dynamics. Two tree-ring width chronologies developed from six sites of Picea crassifolia in the LLM were employed to study the regional drought variability. Correlation and temporal correlation analyses showed that relationships between the two chronologies and self-calibrated Palmer Drought Severity Index （sc_PDSI） were significant and stable across time, demonstrating the strength of sc_PDSI in modeling drought conditions in this region. Based on the relationships, the mean sc_PDSI was reconstructed for the period from 1786 to 2013. Dry conditions prevailed during 1817-1819, 1829-1831, 1928-1931 and 1999-2001. Relatively wet periods were identified for 1792-1795 and 1954-1956. Spatial correlations with other fourteen precipitation/drought reconstructed series in previous studies revealed that in arid regions of Northwest China, long-term variability of moisture conditions was synchronous before the 1950s at a decadal scale （1791-1954）. In northwestern margin of the EASM, most of all selected reconstructions had better consistency in low-frequency variation, especially during dry periods, indicating similar regional moisture variations and analogous modes of climate forcing on tree growth in the region.

ANALYSIS ON EFFECT OF SOUTH ASIA HIGH ON MID-SUMMER EXTREME DROUGHT AND FLOOD IN SICHUAN-CHONGQING REGION

NCEP/NCAR data are utilized to analyze an extreme flood year(1998) and an extreme dry year(2006) in the Sichuan-Chongqing region(SCR) and the results are as follows. The positive divergence of South Asia High(SAH) is stronger in the flood year; the position of the ridge line of SAH is southward compared with the annual average; Western Pacific Subtropical High(WPSH) extends westward and its ridge line is southward. In the drought year, the positive divergence of SAH is weaker, its ridge line is northward, and the position of WPSH is also northward. As shown in the dynamics, in drought(flood) years, negative(positive) vorticity advection in the upper atmosphere can cause the atmosphere to ascend(descend), and anomalous circulation of SAH displays divergence(convergence), and anomalous circulation of the lower atmosphere shows convergence(divergence). Thermal structure of the atmosphere shows that there is warm(cold) temperature advection in the lower atmosphere, and the vertical distribution of diabetic heating causes SAH's local circulation to display convergence(divergence) and affects vertical motion of the lower atmosphere circulation eventually. To some extent, the two extreme years in the SCR is closely related to the vertical motion of atmosphere circulation and the variation of such vertical motion is caused by differences of interactions between SAH and lower atmosphere circulations.

Effectiveness analysis of the prediction of regional debris flow susceptibility in post-earthquake and drought site

Debris-flow disasters occurred frequently after the Mw 8.0 Wenchuan earthquake on 12 May 2008 in Sichuan Province, China. Based on historical accounts of debris-flow disaster events, it found that debris flow occurrence is closely related to the impact of earthquakes and droughts, because earthquakedrought activities can increase the loose solid materials, which can transform into debris flows under the effect of rainstorms. Based on the analysis of historical earthquake activity(frequency, magnitude and location), drought indexes and the trend of climate change(amount of rainfall), a prediction method was established, and the regional debris flow susceptibility was predicted. Furthermore, in a debris flow-susceptible site, effective warning and monitoring are essential not only from an economicpoint of view but are also considered as a frontline approach to alleviate hazards. The advantages of the prediction and early monitoring include(1) the acquired results being sent to the central government for policy making;(2) lives and property in mountainous areas can be protected, such as the 570 residents in the Aizi valley, who evacuated successfully before debris flows in 2012;(3) guiding the government to identify the areas of disasters and the preparation for disaster prevention and mitigation, such as predicting disasters in high-risk areas in the period 2012-2017, helping the government to recognize the development trend of disasters;(4) the quantitative prediction of regional debris-flow susceptibility, such as after the Wenchuan earthquake, can promote scientific and sustainable development and socioeconomic planning in earthquake-struck areas.

旱地小麦区试品系中抗旱高产相关基因的KASP标记检测

利用分子标记检测小麦区试品系,明确其优异等位基因组成,有利于进一步精准改良利用。分析KASP标记检测中存在的问题,有助于促进分子育种应用。以山东省2021—2022年小麦旱地区试24份参试品系为材料,利用32个抗旱高产相关基因的KASP标记,分析KASP标记检测中存在的异常结果和材料的优异等位基因利用情况。结果表明,未知基因型产生的主要原因是KASP反应失败或非特异扩增。混合DNA样品检测结果为杂合的主要原因是单株间基因型不一致,次要原因是错误分型。32个KASP标记中,14个标记的优异等位基因检出率超过83%,表明这些基因在育种中已经得到有效利用;17个标记的优异等位基因检出率低于50%,其中,WRKY51-2B、AX-95025477-7B、SnRK2.4A3、TaMoc-2433和NCED15个标记的优异等位基因未检出,表明这些基因在育种中利用较少,可通过分子标记辅助选择开展遗传改良。24份材料中,HQ04携带20个优异等位基因,是数量最多的,可作为基因供体用于育种。利用KASP标记开展辅助选择定向精准提高优异等位基因在小麦育种中的利用率仍有可为。

甘肃省河东地区气象-水文干旱时空演变特征

干旱半干旱区是气候变化和人类活动的敏感和脆弱区,研究地区干旱时空演变特征有助于成灾机理分析。甘肃省河东地区是我国典型干旱半干旱区,主要依靠自然降水维持农业生产,旱灾尤为突出。基于标准化降水指数和标准化径流指数探讨河东地区气象-水文干旱的时空演变特征,结果表明:(1)气象干旱多发生于春夏两季及陇东地区,较少发生季节型以上气象干旱;(2)水文干旱较气象干旱历时更长,多年尺度干旱时有发生;(3)不同季节气象-水文干旱滞时不同,春夏两季几乎无滞后,秋季约滞后1个月,冬季约滞后4个月;(4)陇中和陇东地区历史受灾/成灾面积较大。本研究可为干旱半干旱区的旱灾预警评估和旱灾防控工作提供参考。

西南季节性干旱区农田土壤水分对降雨的动态响应

【目的】探明西南季节性干旱区不同作物下农田土壤含水率对不同降雨事件的动态响应。【方法】基于田间原位观测,结合2023年4—10月降水和土壤含水率原位连续监测数据,对比分析水稻田和玉米地土壤含水率对不同强度降雨的响应规律。【结果】①不同强度降雨对农田土壤水分补给深度影响不同,小降雨事件(降雨强度<2mm/h)对土壤补给深度为0~20cm,强降雨事件(降雨强度>8mm/h)对土壤补给深度为0~50cm;②不同作物下农田土壤水分对降雨事件的响应存在显著差异,研究期间水稻田和玉米地的土壤水分补给速率均值分别为0.72、1.07%/h,有效补给滞后时间均值分别为0.88、5.38 h,消退速率均值分别为0.04、0.02%/h;③与玉米地相比,水稻对降雨响应更敏感且响应效应更强烈,这可能与作物的冠状叶片截留、根系保水能力有关,同时土壤初始含水率影响土壤水分对降雨事件的响应效应。【结论】强降雨事件能够有效补给农田土壤水分,雨强较小或无降雨时,应根据土壤墒情及时补充地面灌溉。

区域旱灾风险评估与诊断的动态差异度系数模糊数随机模拟方法

为更准确、稳健地进行旱灾风险动态评估、关键障碍因子的定量识别,构建了差异度系数随评价指标样本值动态变化的三角模糊数与随机模拟耦合方法,并用于宿州市2007—2017年旱灾风险评估与诊断研究中,得到宿州市置信概率为95%的旱灾风险评价值区间,结果表明:旱灾风险评价结果呈“先增加,后减小,最后趋于稳定”的变化趋势,旱灾风险综合评价结果为“轻险”;危险性、暴露性、抗旱能力三个子系统是影响研究区域旱灾风险综合评价结果趋势变化的主因;耕地率、水库调蓄率、农业人口比例评价指标被诊断为中阻碍型因子,是需要重点调控的对象;置信概率区间增加了风险评价结果的可靠性信息,可反映受多种不确定影响因素综合作用下的实际旱灾风险情况,充分体现了联系数所表征的“不确定性”这一信息。

三江源牧草气候生产力变化及对气象干旱的响应

基于1970-2020年三江源地区18个气象站点逐月地面观测资料,以不同时间尺度标准化降水蒸散指数(Standardized precipitation evapotranspiration index,SPEI)为气象干旱监测指标,采用逐步订正法计算牧草气候生产力,分析三江源地区牧草生长季气象干旱和气候生产力的时空特征,初步揭示气候生产力对气象干旱的响应状况。结果表明:近50a,三江源地区牧草生长季气象干旱呈加重态势(P<0.01),1995年左右气候由湿润逐步转变为干旱,干旱发生区域主要分布在西部、中南部和东北部地区;三江源西北部地区干旱化更明显。牧草生长季气候生产力整体以7.38kg·hm^(-2)·a^(-1)的速率减少(P<0.01);空间上由西北向东南减少,呈西部上升、东部下降的空间分布。三江源地区牧草生长季气候生产力与不同时间段前推SPEI具有较强的正相关性,且随SPEI前推时间增加,相关系数微弱增加,中西部地区牧草气候生产力对气象干旱的响应高于其他区域。

基于NDVI-LST模型的四川攀西地区近20 a干旱演变特征

随着全球变暖不断加剧,区域性干旱事件频发,我国近些年采取了诸多措施来应对干旱事件,为分析相关措施成效,以四川攀枝花、凉山州地区(简称“攀西地区”)为例,研究该区域近20 a干旱演变特征,以服务当地生产和发展。利用中分辨率成像光谱仪(Moderate Resolution Imaging Spectroradiometer,MODIS)的归一化植被指数(Normalized Difference Vegetation Index,NDVI)和地表温度(Land Surface Temperature,LST)数据计算了2003—2022年攀西地区的温度植被干旱指数(Temperature Vegetation Dryness Index,TVDI),分析TVDI在不同时间尺度上的变化及该区域过去20 a来干旱的演变特征。研究表明:(1)攀西地区干旱多发生在春季的3—5月,10月前后TVDI值最低,也是最不易发生干旱的时段。(2)攀西地区干旱逐年缓解,由TVDI监测的无旱和重旱区域所占面积变化不大;轻旱面积有所增加,2013年后比之前平均增加5.30%;而中旱面积有所减少,2013年后比之前平均减少5.67%。(3)昭觉、布拖和越西等地干旱缓解明显,而木里、米易、会理等地区干旱有加重趋势。(4)攀西地区旱情大部分区域较稳定,其面积约占总面积的82.59%,干旱重心南北方向上变化较小,但有向西迁移的趋势。

广西干旱灾害风险评估及区划

随着全球变暖的不断加剧,许多地区极端干旱事件频繁发生。为探究广西极端干旱事件发生频率及风险情况,基于1950-2022年逐日降水和气温数据计算的SPEI指数识别干旱事件并依据囊括社会经济数据和农业数据的灾害风险评估理论,使用层次分析法确定指标权重,构建广西干旱灾害风险评估模型,并绘制广西干旱灾害风险区划图。结果表明:干旱灾害危险性指数较高的地区主要分布在百色、玉林、北海等地;环境脆弱性指数以明显的北高南低特征分布,百色、河池、桂林等地脆弱性指数较高,并有向南递减趋势;承灾体易损性指数整体偏低,南宁、桂林及玉林小部分地区最高;防灾减灾能力指数呈西北高东南低的特征分布,高指数地区主要分布在南宁,玉林柳州等地也有零星分布;广西干旱灾害风险总体呈现西高东低、北高南低的特征分布,高风险地区主要在百色、桂林和南宁等地,较高风险地区主要在河池西部、玉林、钦州、来宾、崇左北部和柳州北部,较低风险地区主要分布在崇左南部到北海,贺州到梧州一带。得出了比较精确的广西干旱灾害空间分布情况,可为广西抗旱减灾提供切实依据。

2022年夏季川渝高温干旱事件对电力供需影响分析

在气候变化背景下,极端天气气候事件的多发对电力系统的影响加剧。利用川渝地区1961—2022年的气温、降水和气象干旱指数,2022年7—9月泸定、立洲和瓦屋山水电站的日入库流量和发电量,及2022年6—9月成都市和四川省的日用电量和日高峰负荷等数据,分析2022年盛夏川渝地区高温干旱事件及其对水电和电力需求的影响。结果表明,1961—2022年川渝地区气温及高温日数显著增加,高温干旱灾害风险增大。2022年盛夏(7—8月),川渝地区气温偏高幅度、降水偏少程度、高温日数、最大干旱影响范围均为1961年以来之最。降雨量和入库流量是影响水电的重要因素,水电出力对入库流量的响应呈非线性;夏季气温与用电量具有显著的正相关,日用电量和高峰负荷对日平均气温的敏感性最高。

区域农业抗旱减灾能力影响因素及指标模型构建

为了对区域农业灾害进行防控,分析了山东省旱灾相关影响因素,通过旱灾影响因素构建旱灾预警模型,并对各因素耦合关系进行分析,最后将构建的农业旱灾综合评估模型应用于具体农业生产环境。结果表明,不同农业区域在抗旱减灾能力上存在明显差异,农业旱灾综合评估排名前3的城市为烟台市、日照市、青岛市,农业旱灾综合评估值分别为2.90、2.87、2.86。山东省经济发达区域集中在沿海地区,这些地区有充足的技术、物资、人才及财政支持,农业抗旱减灾能力强。而对于雨水贫瘠、经济较弱区域,农业抗旱减灾能力较差,集中在德州市、济宁市、东营市等地区。由此可见,要提升这些地区抗旱减灾能力,需要从财政投入、农业技术、应急管理等方面入手,确保地区农业的科学化发展。