Relationship Between Persistent Heavy Rain Events in the Huaihe River Valley and the Distribution Pattern of Convective Activities in the Tropical Western Pacific Warm Pool

Using daily outgoing long-wave radiation （OLR） data from the National Oceanic and Atmospheric Administration （NOAA） and the National Center for Environmental Prediction/National Center for Atmospheric Research （NCEP/NCAR） reanalysis data of geopotential height fields for 1979-2006, the relationship between persistent heavy rain events （PHREs） in the Huaihe River valley （HRV） and the distribution pattern of convective activity in the tropical western Pacific warm pool （WPWP） is investigated. Based on nine cases of PHREs in the HRV, common characteristics of the West Pacific subtropical high （WPSH） show that the northern edge of the WPSH continues to lie in the HRV and is associated with the persistent ＂north weak south strong＂ distribution pattern of convective activities in the WPWP. Composite analysis of OLR leading the circulation indicates that the response of the WPSH to OLR anomaly patterns lags by about 1-2 days. In order to explain the reason for the effects of the distribution pattern of convective activities in the WPWP on the persistent northern edge of the WPSH in the HRV, four typical persistent heavy and light rain events in the Yangtze River valley （YRV） are contrasted with the PHREs in the HRV. The comparison indicates that when the distribution pattern of the convective activities anomaly behaves in a weak （strong） manner across the whole WPWP, persistent heavy （light） rain tends to occur in the YRV. When the distribution pattern of the convective activities anomaly behaves according to the ＂north weak south strong＂ pattern in the WPWP, persistent heavy rain tends to occur in the HRV. The effects of the ＂north weak south strong＂ distribution pattern of convective activities on PHREs in the HRV are not obvious over the seasonal mean timescale, perhaps due to the non-extreme status of convective activities in the WPWP.

RELATIONSHIPS BETWEEN THE POSITION VARIATION OF THE WEST PACIFIC SUBTROPICAL HIGH AND THE DIABATIC HEATING DURING PERSISTENT INTENSE RAIN EVENTS IN YANGTZE-HUAIHE RIVERS BASIN

By using NCEP/NCAR daily reanalysis data and daily precipitation data of 740 stations in China, relationships between the position variation of the West Pacific subtropical high (WPSH) and the diabatic heating during persistent and intense rains in the Yangtze-Huaihe Rivers basin are studied. The results show that the position variation of WPSH is closely associated with the diabatic heating. There are strong apparent heating sources and moisture sinks in both the basin (to the north of WPSH) and the north of Bay of Bengal (to the west of WPSH) during persistent and intense rain events. In the basin, Q 1z begins to increase 3 days ahead of intense rainfall, maximizes 2 days later and then reduces gradually, but it changes little after precipitation ends, thus preventing the WPSH from moving northward. In the north of Bay of Bengal, 2 days ahead of strong rainfall over the basin, Q 1z starts to increase and peaks 1 day after the rain occurs, leading to the westward extension of WPSH. Afterwards, Q 1z begins declining and the WPSH makes its eastward retreat accordingly. Based on the complete vertical vorticity equation, in mid-troposphere, the vertical variation of heating in the basin is favorable to the increase of cyclonic vorticity north of WPSH, which counteracts the northward movement of WPSH and favors the persistence of rainbands over the basin. The vertical variation of heating in the north of Bay of Bengal is in favor of the increase of anti-cyclonic vorticity to the west of WPSH, which induces the westward extension of WPSH.

The 10 Most Influential Heavy Rain Events in China in 2022:Selection and Evaluation

In 2022,a campaign to select and recognize 10 most influential heavy rain events(HREs)in China was initiated by the Chinese Meteorological Society and Wuhan Heavy Rain Research Institute of the China Meteorological Administration(CMA).A work flow involving both scientists and the general public for selecting major HREs over the Chinese mainland was implemented,and several evaluation indices that can represent HREs as well as associated causality and economic losses were established,based on which the top 10 most influential HREs in 2022 were recognized and announced to the public.The present paper introduces the selection and evaluation process and summarizes the main results.It is found that 38 major HREs occurred in South,North,and Northeast China in 2022,with the Pearl River basin and Songliao basin experiencing severe floods.A number of HREs occurred in Southwest China with high rainfall intensity,but small cumulative amount.Upper-level troughs,low vortices,low-level jets,low-level shear lines,the subtropical high,and typhoons are the main weather systems leading to the top 10 most influential HREs in 2022.Selection and evaluation of HREs form a quantitative record of major HREs,help concentrate limited research efforts on investigating the causes of major HREs,and promote the improvement of HRE forecasting skills.

Frontal genesis of moisture atmosphere during the early 2008 persistent freezing-rain event in southern China

From January 10 to February 2, 2008, a severe and persistent freezing-rain event occurred in southern and southwestern China. Here we use an observational analysis to compare the persistent freezing-rain event in the early 2008 with the winter precipita- tion in the late 2007 over south of the Yangtze River (Jiangnan). The persistent freezing-rain event was directly linked to the activity of quasi-stationary front. The gradient of equivalent temperature (ET) can well indicate the frontal genesis of moist atmosphere (moisture front) and its activity as well as its relationship with precipitation belt. The precipitation types (snow and freezing rains) are related to the vertical structure of moisture front. The inversion profile of ET vertical distribution is a typical synoptic condition that caused the freezing-rain event. The horizontal gradient of ET with a criterion of 10℃ / 100 km, which reflects the accumulation and release of atmospheric energy, can be applied to predict the precipitation 5-10 days in advance.

Test of newly developed conceptual hydrological model for simulation of rain-on-snow events in forested watershed

A conceptual hydrological model that links the Xin＇anjiang hydrological model and a physically based snow energy and mass balance model, described as the XINSNOBAL model, was developed in this study for simulating rain-on-snow events that commonly occur in the Pacific Northwest of the United States. The resultant model was applied to the Lookout Creek Watershed in the H. J. Andrews Experimental Forest in the western Cascade Mountains of Oregon, and its ability to simulate streamflow was evaluated. The simulation was conducted at 24-hour and one-hour time scales for the period of 1996 to 2005. The results indicated that runoffand peak discharge could be underestimated if snowpack accumulation and snowmelt under rain-on-snow conditions were not taken into account. The average deterministic coefficient of the hourly model in streamflow simulation in the calibration stage was 0.837, which was significantly improved over the value of 0.762 when the Xin＇anjiang model was used alone. Good simulation performance of the XINSNOBAL model in the WS 10 catchment, using the calibrated parameter of the Lookout Creek Watershed for proxy-basin testing, demonstrates that transplanting model parameters between similar watersheds can orovide a useful tool for discharge forecastin~, in un^au^ed basins.

Extreme Rainfall Event Analysis Using Rain Gauges in a Variety of Geographical Situations

About 30 years of measurements made by the rain gauges located in Piedmont (Italy) have been analyzed. Rain gauges have been divided into 4 datasets considering the complex orography near Turin, namely the flatlands, mountains, hills and urban areas. For each group of gauges, the Generalized Extreme Values (GEV) distributions are estimated considering both the entire dataset of available data and different sets of 3 years of data in running mode. It is shown that the GEV estimated parameters temporal series for the 3 years dataset do not present any specific trend over the entire period. The study presented here is preliminary to a future extreme rainfall event analysis using high temporal and spatial resolution X-band weather radar with a limited temporal availability of radar maps covering the same area.

X-Band Mini Radar for Observing and Monitoring Rainfall Events

Quantitative precipitation estimation and rainfall monitoring based on meteorological data, potentially provides continuous, high-resolution and large-coverage data, are of high practical use: Think of hydrogeological risk management, hydroelectric power, road and tourism. Both conventional long-range radars and rain-gauges suffer from measurement errors and difficulties in precipitation estimation. For efficient monitoring operation of localized rain events of limited extension and of small basins of interest, an unrealistic extremely dense rain gauge network should be needed. Alternatively C-band or S-band meteorological long range radars are able to monitor rain fields over wide areas, however with not enough space and time resolution, and with high purchase and maintenance costs. Short-range X-band radars for rain monitoring can be a valid compromise solution between the two more common rain measurement and observation instruments. Lots of scientific efforts have already focused on radar-gauge adjustment and quantitative precipitation estimation in order to improve the radar measurement techniques. After some considerations about long range radars and gauge network, this paper presents instead some examples of how X-band mini radars can be very useful for the observation of rainfall events and how they can integrate and supplement long range radars and rain gauge networks. Three case studies are presented: A very localized and intense event, a rainfall event with high temporal and spatial variability and the employ of X-band mini radar in a mountainous region with narrow valleys. The adaptability of such radar devoted to monitor rain is demonstrated.

贵州省不同强度区域性凝冻过程环流形势对比分析

利用贵州省84个气象站逐日观测资料以及再分析资料,对4种不同强度区域性凝冻过程进行对比分析。结果表明:500 hPa位势高度场上中高纬度的亚洲东部区域距平场呈现“+-”的分布或有切断低压分布,贝加尔湖至中国华北地区以经向环流为主;850 hPa风场上云南南部以南受偏南风和西南风控制,并且在江南至华南存在西南或西风急流,是4种不同强度凝冻过程中形势场共性特征。500 hPa高度场上中高纬度地区呈两槽一脊或一槽一脊分布;风场上850 hPa东北风回流和700 hPa西南急流形成上暖下冷的形势场,同时850 hPa形成稳定低层切变线;温度场上存在冷暖冷的夹心结构,近地面层0℃线维持在900 hPa以下,均是较强等级以上的区域性凝冻过程中形势场共性特征。而对于一般性区域性凝冻过程,500 hPa位势高度场上呈多槽脊分布,风场上是否存在东北风回流和低层切变线,温度场上是否存在冷暖冷的夹心结构以及近地面层0℃线位置等特征均不统一。温度剖面图上,当近地面层0℃线位置最低时或出现冷暖冷的夹心结构时段与凝冻过程影响范围最广、灾情最重的时间段对应。

暖干背景下的河南春季极端雨雪天气成因分析

过渡季节的春季极端雨雪天气一直以来都是预报中的难点。利用常规地面观测、探空、多普勒天气雷达等观测资料和ERA5再分析数据,对2023年3月16日发生在河南省的一次极端雨雪天气成因进行了分析,重点关注了其极端降水及复杂雨雪相态转换成因。主要结论如下:此次过程是一次发生在暖干背景下,由高空槽东移配合低涡切变线北抬造成的极端雨雪天气,具有转折性强、降雪强度大、强降雪时段长等特点,降雪时地面气温始终维持在0℃附近,雨雪相态转换复杂;异常偏强的极端动力强迫是此次过程小时降水强度大的重要因素,这与对流层低层异常偏强的低空急流所伴随的热、动力强迫有关。另外,条件对称不稳定也在一定程度上加剧了其垂直上升运动的发展,低涡移动缓慢、回波系统走向与移向夹角较小是其降水持续较长时间的关键;过程前期气温异常偏高,15日冷空气降温为雨雪相态转换提供了可能,但河南省中、东部边界层气温仍未达到雨转雪标准,过程开始阶段对流层低层存在明显干层,与此相伴随的由降水粒子蒸发等相变过程造成的降温,是其雨转雪的重要降温机制,干层的存在及降水的持续发展,成为边界层气温能否降到0℃附近的关键,大气趋于饱和之后,固态降水粒子的融化降温在降雪相态维持中也起到了十分重要的作用。

基于社交媒体数据的城市暴雨洪涝灾害风险评估——以郑州市“7·20”暴雨事件为例

近年来强降雨引发的城市洪涝灾害事件趋多,严重危害了人民的生命健康和财产安全,而客观、准确地开展城市暴雨洪涝灾害风险评估对于有效提升防灾减灾水平至关重要。但是,城市灾害点部分基础数据资料的缺失和滞后限制了城市暴雨洪涝灾害风险评估结果的准确性。随着移动互联技术的发展,民众在社交媒体上发布的相关灾害信息逐渐汇集成一种具有海量、时效性强和主题明确等特征的社交媒体数据资源,将其引入城市暴雨洪涝灾害风险评估工作对于准确刻画城市暴雨洪涝灾害的全貌无疑具有显著意义。以2021年郑州市“7·20”暴雨事件为例,首先从气象因素、基础地理信息、社会经济因素三方面选取了13个影响因子,然后基于爬虫技术获取微博数据中的内涝点信息,最后基于GBDT、XGB、RF和AdaB 4种机器学习模型对郑州市“7·20”暴雨洪涝灾害进行风险评估。结果表明:①基于上述模型得到的4组指标权重具有统计意义上的一致性,在各影响因子中,道路密度、植被覆盖指数、半小时最大降雨量和日最大降雨量在4组指标重要性排序中均位列前5,表明上述影响因子是本次暴雨洪涝灾害的主要致灾因素;②基于皮尔逊相关系数检验发现上述4种模型评估结果间的相关程度较高,所得出的极高风险区均集中在郑州市五大主城区的中心部分、中牟市东北部、新密市米村镇及城关镇、巩义市巩义站周边;③上述4种模型的AUC和ACC值均超过0.7,证实了机器学习模型在城市暴雨洪涝灾害风险评估中的有效性;相较于GBDT、XGB和RF模型,AdaB模型的评估结果精度最高,且得到的高风险与极高风险区的Rei值之和最大,表明其评估结果与实际情况相符。本研究通过将社交媒体数据引入城市暴雨洪涝灾害风险评估工作有效地提升了评估结果的准确性,可为郑州市及其他城市在类似强降水事件下的洪涝灾害风险预警和应急处置提供决策依据。

黄土高原PM_(2.5)质量浓度与微雨事件的权衡−协同关系演化

基于权衡−协同关系视角,从长时间序列和多层次空间尺度探讨1998—2017年黄土高原PM_(2.5)质量浓度与微雨事件的作用关系、时空演化及地域分异。结果表明:①黄土高原PM_(2.5)质量浓度和微雨事件均表现出以5 a或4 a为周期的“三峰三谷”波动小幅上升趋势。②PM_(2.5)质量浓度和微雨事件间的作用关系呈现出“过程上的协同性+增量上的权衡性”特征;从过程演化来看,协同关系是研究期内黄土高原PM_(2.5)质量浓度和微雨事件的主导关系,但从基于倾斜率的增量变化上看,二者以异向的权衡关系为主导,表明微雨事件的强化在黄土高原未来的雾霾治理中具有重要意义。③不同微雨事件指标与PM_(2.5)质量浓度的空间关系和演化趋势存在差异;冬春季节微雨事件,尤其是冬春微雨天数与PM_(2.5)质量浓度的作用关系明显强于年尺度。④PM_(2.5)质量浓度和微雨事件权衡−协同关系及演化在不同治理分区差异显著,城镇化和工业化水平较高的河谷平原区和土石山区是二者关系敏感区。

1991-2020年重庆水稻生育期连阴雨气候特征及成因

为掌握重庆水稻生育期连阴雨的发生规律与成因,科学指导水稻生产防灾减灾,基于1991—2020年重庆市气象资料、水稻生育期观测资料及再分析资料,研究重庆水稻不同种植区及不同生育期的连阴雨气候特征和大气环流特征。结果表明,重庆各种植区全生育期的连阴雨均呈减少趋势,其中,中部减少趋势最明显,连阴雨发生站次比气候倾向率为-0.33·(10 a)^(-1);东南部连阴雨发生站次比最高,达1.18,但减少趋势最弱;东北部连阴雨发生站次比最低,仅0.55,且预计阴雨灾害将进一步减少。水稻营养生长期的连阴雨发生频次最高,生殖生长期最低。空间分布上,水稻全生育期连阴雨发生频次东南部最高,单点最大值达1.80;东北部最低,单点最小值仅0.27;高值区分布在重庆偏南区域,不同生育期略有差异;而低值区始终位于东北部。连阴雨发生最为频繁的营养生长期,各地区均受负位势高度异常控制,南北位势高度梯度减小,冷空气南下易导致连阴雨发生。连阴雨发生频次最高的重庆东南部,水汽起源于太平洋,由副热带高压外围的东南暖湿气流提供。营养生长期的水汽输送带相比苗期更偏南,呈西南向分布。

Seasonal and Annual Variations of CO_2 Fluxes in Rain-Fed Winter Wheat Agro-Ecosystem of Loess Plateau, China

To accurately evaluate the carbon sequestration potential and better elucidate the relationship between the carbon cycle and regional climate change, using eddy covariance system, we conducted a long-term measurement of CO 2 fluxes in the rain-fed winter wheat field of the Chinese Loess Plateau. The results showed that the annual net ecosystem CO 2 exchange （NEE） was （-71.6±5.7） and （-65.3±5.3） g C m-2 y-1 for 2008-2009 and 2009-2010 crop years, respectively, suggesting that the agro-ecosystem was a carbon sink （117.4-126.2 g C m-2 yr-1）. However, after considering the harvested grain, the agro- ecosystem turned into a moderate carbon source. The variations in NEE and ecosystem respiration （R eco ） were sensitive to changes in soil water content （SWC）. When SWC ranged form 0.15 to 0.21 m3 m-3, we found a highly significant relationship between NEE and photosynthetically active radiation （PAR）, and a highly significant relationship between R eco and soil temperature （T s ）. However, the highly significant relationships were not observed when SWC was outside the range of 0.15-0.21 m3 m-3. Further, in spring, the R eco instantly responded to a rapid increase in SWC after effective rainfall events, which could induce 2 to 4-fold increase in daily R eco , whereas the R eco was also inhibited by heavy summer rainfall when soils were saturated. Accumulated R eco in summer fallow period decreased carbon fixed in growing season by 16- 25%, indicating that the period imposed negative impacts on annual carbon sequestration.

THE FEATURES OF EAST ASIAN JET STREAM IN PERSISTENT SNOWSTORM AND FREEZING RAIN PROCESSES OVER SOUTHERN CHINA IN EARLY 2008

Based on the National Centers for Environmental Prediction and National Center for Atmospheric Research(NCEP/NCAR) daily reanalysis data and the upper-level objective analysis data provided by the Meteorological Information Comprehensive Analysis and Process System(MICAPS),the feature of the spatio-temporal variation of the East Asian jet stream(EAJS) in persistent snowstorm and freezing rain processes over southern China in January 2008 have been investigated.Each of the storm events was closely linked with the extraordinarily abnormal variations of East Asian subtropical jet(EASJ) and East Asian polar front jet(EAPJ) at that time.The stronger EASJ with abnormally northward position of the jet axis corresponded to the more intense storm event with broader ranges and longer duration time.The heavy freezing-rain-and-snow event occurred over the region where a strong southerly wind of EASJ prevailed.Meanwhile,the westerly and northerly winds of the EAPJ were significantly intensified,which were also closely related to the beginning,enhancement,and ending of the heavy snowfall.The meridional component of the EAPJ was dominated by the northerly wind during the snowstorm.Thus,the intensification of the snowstorm was attributed to both the strengthening of the meridional wind of EAPJ and the southerly wind of EASJ.Further analysis indicated that wind speed and the zonal wind of the two jets exhibited precursory signals about half a month prior to this extreme event,and the precursory signals were found in the meridional components of the two jets about 20 days preceding the event.The sudden weakening of the meridional component of EASJ and the zonal component of EAPJ signified the ending of this persistent snowstorm.

Intense Rainfall in São Carlos/SP: Determination of Threshold Values Using Climate Indices and Their Spatio-Temporal Repercussion

The intense and extreme rains in southeastern Brazil are spatially and temporally dynamic, corroborating their substantial complexity regarding understanding and associations. Therefore, the present study aimed at determining threshold values for events of intense and extreme rainfall in the region of São Carlos/SP using a climatic index, as well as temporal and spatial observations. The RClimdex script, Rnn index, and the detection of outliers were employed in order to mark and establish intense and extreme rainfall thresholds for the region. Values of 10 mm and 20 mm of rain were considered typical and of greater recurrence, and their incidence over a period of 24 hours did not necessarily denote intense events. In turn, values of 35, 46, and 60 mm indicate pluviometric rates that impact on significant disasters, as verified in the IPMET/UNESP natural disasters database. It is important to emphasize that values below 60 mm of daily rainfall may also indicate disaster contexts. However, they do not exclude the necessity to verify the intensity, duration, and frequency of intense rain events, and can delineate thresholds for territorial management organizations in their planning.

The research of below-cloud scavenging of rainwater in Guilin City

Sequential samples of single precipitation event were collected by the use of specially de-signed semi-automatic sequential precipitation collector in the spring of 1988 in Guilin City. ThePH value and soluble chemical species such as SO, NO, NH, Ca￣(2+), Mg￣(2+), Na￣+, K`+, F￣- andCl￣- were analyzed. An apparent decrease in the concentration of all ions except H￣+ and NO wasobserved at the initial portion of the events. The relative acidity increased as the event progress.The concentration of H￣+ was the result of comprehensive actions of all ions. The average scavengingratio of events was calculated and it is found that SO was the major contributor for acid rain inGuilin and Ca￣(2+) was the important neutralizer.

突发洪涝灾害中考虑心理焦虑影响的多周期应急物资调度研究

在突发洪涝灾害背景下,综合考虑应急物资短缺率、动态降雨量预报,以及物资供应周期时长等因素对灾区群众心理焦虑的影响作用并建立相应的心理焦虑量化函数。在此基础上以最小化物流成本和心理焦虑成本为目标,构建突发洪涝灾害背景下的多周期应急物资调度模型,并通过快速非支配排序遗传算法对模型进行求解。最后,以2021年7月河南省暴雨事件为案例进行实例验证分析,结果表明:1)相比于基础应急物资调度模型,本文提出的考虑心理焦虑成本的模型会增加20.09%的物流成本,但焦虑成本降低了93.57%;2)对供应周期时长的敏感性分析表明,当供应周期时长由72 h降至48 h,物流成本提高29.00%,焦虑成本下降43.70%;周期时长由48 h降至24 h,物流成本增加49.81%,焦虑成本下降51.41%。研究结论有助于应急管理部门更好地制定适用于洪涝灾害的应急物资调度方案。

湖南一次雨雪天气降水相变的环境条件与双偏振雷达特征分析

基于常规气象观测资料、NCEP再分析资料以及长沙双偏振雷达、风廓线雷达资料,对湖南2021年12月下旬一次雨雪天气过程降水相态转变的大气环境条件和雷达双偏振特征进行分析,得到以下结论:(1)降雪前干层消失,湿层增厚,整层湿球温度低于0℃,逆温层下冷垫的饱和层结对雪花丛集增长有利,有利于降雪增强。(2)湘中及以北地区位于700hPa西南急流出口区,600—800hPa强烈水汽辐合和中低层强上升气流为暴雪过程提供充足水汽。(3)25日夜间长沙出现间歇性小雨(雪)和多次短波槽过境密切相关;26日上午西南风转为偏西风导致长沙降雪出现短时减弱;冷垫上西南暖湿气流增强时段、冷垫内东南风转为东北风时段,分别对应26日长沙降雪两个峰值。(4)不同相态降水时段相关系数(CC)、差分反射率(Zdr)、水平反射率因子(Zh)有一定差异,双偏振产品对本次雨雪天气过程中降水相态转变的识别有一定指示作用。(5)低层“零速度线”成直线且有风速辐合特征,西南急流核增强、向下扩展等特征预示暖湿气流在冷垫之上的动力爬升增强,降雪得以长时间维持、且强度增强;而随着径向速度风场辐散特征出现,降雪逐渐减弱。

青藏高原东部和西南地区低温冰冻雨雪事件的时空变化特征

利用国家气象信息中心1961-2020年青藏高原东部和我国西南地区157个站点逐日最低气温和降水量数据,定义了一个低温冰冻雨雪事件的标准,采用Mann-Kendall突变检验、滑动t检验和EOF等方法分析了两个地区低温冰冻雨雪事件的气候特征和时空变化特征。结果表明:(1)青藏高原东部和西南地区低温冰冻雨雪发生的频次及其降水量的年变化的气候特征有明显的不同。青藏高原呈现出明显的双周期年变化,初春3月达最大值,秋季10月达第二峰值;西南地区则是U型的单周期年变化,在冬季1月最多。(2)高原上发生频次最多的区域在青海三江源和藏北怒江源地区,西南地区发生频次最多的区域在贵州的西部。(3)EOF分解得到的前3个模态表明不同季节低温冰冻雨雪频次的时空间变化有明显的不同。青藏高原春季和秋季第一空间分布模态呈全区一致变化,时间系数具有明显年代际振荡特征,春季在20世纪70年代末到2000年发生的频次较多,经历了“偏少-偏多-偏少”的演变过程;秋季在20世纪60~70年代低温冰冻雨雪频次偏多,在1981年前后发生年代际突变,之后发生的频次偏少;冬季第一空间分布模态以西南地区冬季变化为主,表明西南地区冬季在1985年前后有明显的突变特征,经历了“偏多-偏少”的变化过程;冬季第二空间分布模态以高原地区冬季变化为主,其时间变化特征与高原春季时间变化类似,2009年左右有明显的突变特征。

基于农业水灾解析河南省雨涝事件的时空演变特征

河南省是中国重要的粮食主产区,分析雨涝事件的时空演变特征对保障区域粮食安全有着重要意义。依托研究区1978—2019年间农业水灾受灾率、成灾率以及逐日降水量等资料,运用集合经验模态分解(EEMD)探求了实际灾情与多种类型降雨涝指数的可能关系。在此基础上,分析了关键致灾因子的时空演变特征及其对大尺度海洋—大气环流指数的响应。结果表明:(1)EEMD精准地从灾情逐年序列分离出年际及年代际波动表征的雨涝强度;(2)雨涝强度与多种降水指数的相关分析表明8月连续7日最大降水量对灾情影响最为显著,其次为9月总降雨日数;(3)致灾因子的空间分布表明河南省南部及西部危险性较高,其趋势分析的结果表明夏季雨涝强度呈现一定的减弱趋势;(4)致灾因子与热带南大西洋海温等环流指数间存在着时滞6~9个月的显著相关性。该研究筛选出了河南省水灾的关键致灾因子,并为提前预判灾情提供的环流信号。