“8.26”成都区域性短时暴雨天气过程的对流指数分析     

唐钱奎  鲁燕  黄先伦 《成都信息工程学院学报》2010,25(5):518-523

利用常规探空资料以及MICAPS3.0系统软件计算的对流指数对2009年8月25~26日发生在成都的短时区域性暴雨过程进行分析,结果表明：稳定度指数与此次暴雨的发生、发展存在一定的关系。LI指数和IC指数在短时暴雨发生前达到最强,K指数和SI指数具有一定的超前性,在强降水发生前12小时达到最强;能量指数在暴雨发生前有一个明显的突变过程,峰值与强降水开始时刻对应;SSI指数与SHR有着一致的变化趋势,在强降水发生前也具有明显的突变性,这说明短时暴雨过程是强动力作用和强热力作用共同作用的结果。对流指数具有的这种突变性可作为预报短时暴雨的一种指标。  相似文献   

应用迁移学习的林火烈度初始评估研究     

郑忠  Jinfei Wang  邹滨  高阳华  杨世琦  王永前 《遥感学报》2022,26(10):2001-2013

林火发生后,开展森林生态系统烈度信息的初始评估,能够为灾后生态修复管理措施的快速实施提供定量依据。为了改善传统林火烈度评估模型的时效性,本研究利用历史过火区域的实地调查数据,构建基于迁移学习的烈度评估模型,并将其应用于2020年3月30日发生的西昌泸山森林大火烈度初始评估研究中。研究结果表明：迁移学习算法能够将源区域和目标区域的遥感影像光谱转换为多个新的特征变量,在这些新特征变量构成的投影空间中,源区域和目标区域样本具有相似的特征分布。在此基础上,基于源区域历史实地调查数据构建的烈度评估模型,能够迁移应用于目标区域的烈度评估。在本研究林火烈度的初始评估中,基于迁移学习的烈度评估模型精度较高,总体精度为71.20%,Kappa系数为0.64。与该模型对比,未进行迁移学习的支持向量回归模型精度较低,其总体精度为58.00%,Kappa系数为0.48。同时,基于dNDVI、dLST和dNBR指数的经验回归模型精度最低,其总体精度分别为：20.80%、34.8%和24.80%,Kappa系数分别为：0.01、0.19和0.06。本研究可为林火灾后管理措施的快速响应,提供一种新的思路和参考。  相似文献   

CHIMEHERB人工皮临床应用研究总结     

李绪焜 《中国海洋大学学报(自然科学版)》1989,(Z3)

CHIMEHERB人工皮是由海洋生物材料制成的烧伤创面覆盖材料,主要成分是甲壳胺(chi-tosan).经山东省13所医院在不同类型的烧伤创面,历时3年的临床应用496例表明:CHIMEHERB人工皮对烧伤创面有良好地促进愈合作用,适用于新鲜Ⅲ°创面、供皮区创面、深Ⅱ°削痂创面、脱痂创面以及部分切痂植皮创面.不适于感染严重的烧伤创面.该人工皮不致敏,无刺激,无吸收中毒之虞,虽然弹性与粘附性还不理想,但不失为我国目前较完好的一种创面覆盖物.  相似文献   

影响湛江热带气旋的风雨分型     

杨彩福  李淑君 《海洋通报》2003,22(4):15-20

利用国家气象局编制的《热带气旋年鉴》和南海舰队海洋水文气象中心的天气图1981—2000年共20a资料，对影响湛江的热带气旋进行分析得出：(1)影响湛江热带气旋按其带来的不同风雨天气可分成4种类型：强型、弱型、风型和雨型；(2)影响湛江热带气旋的42.3％为弱型，其所带来的灾害天气并不明显，有危害性的为强型、风型和雨型；(3)影响湛江热带气旋的源地、出现月份、强度及移速与其分型有一定关系；(4)湛江历史上出现的大海潮，都是移速较快的风型和强型西太平洋台风在7月和9月造成的。  相似文献   

An integrated approach to the estimation of streamflow drought quantiles / Une méthode intégrée d’estimation des quantiles de sécheresse hydrologique     

《水文科学杂志》2013,58(6)

Abstract

Abstract An approach was developed for combining streamflow drought information from synthetic (generated) data with data reconstructed based on palaeoclimatic information (tree ring widths). The tree ring data were used to reconstruct streamflow in periods when no streamflow data were collected. The reconstructed data were then used as a source of historical data for estimating drought severity quantiles. The generated data were obtained using a nearest neighbour resampling method while the tree ring reconstruction was accomplished using a regression model. The application of the approach was to data from the Athabasca River in Alberta, Canada. The results demonstrate the feasibility and the utility of the approach for obtaining more accurate and precise estimates of extreme drought severity quantiles.  相似文献   

基于GIS的汶川地震灾区小流域土壤侵蚀评价——以彭州龙门山区为例     

司渤洋  第宝锋  张斌  余波 《山地学报》2011,29(4)

汶川大地震对龙门山区造成了严重破坏.地震引发的次生山地灾害以及剧烈的土壤侵蚀仍将长期持续地影响着当地居民的生产与生活.对地震前后小流域的土壤侵蚀严重性进行评价并分析其变化,将对灾后小流域水土保持综合治理及生态恢复与重建工作具有重要的指导意义.基于GIS技术,以四川省彭州市龙门山区为研究区,以小流域作为基本单元,针对研究区地震灾区小流域土壤侵蚀,构建侵蚀严重性指数评价及分级方法,对地震前后土壤侵蚀严重性及变化特征并进行评价与分析.结果表明,地震后绝大部分小流域的土壤侵蚀趋重.震后土壤侵蚀程度不严重、较严重的小流域数量别由震前8个及21个降至5个及8个,新增严重、极严重小流域分别为12个及4个,相应面积分别为183.76 km2,52.70 km2.空间上流域土壤侵蚀严重性由西北向东南递减.地震前后小流域平均海拔、平均坡度与侵蚀严重程度正相关,且平均坡度对侵蚀严重程度加重贡献更大.  相似文献   

Application of spatial EOF and multivariate time series model for evaluating agricultural drought vulnerability in Korea     

Dae Ha Kim  Tae-Woong Kim 《Advances in water resources》2011,34(3):340-350

This study proposed a methodology using the empirical orthogonal function (EOF) and multivariate time series model for the analysis of drought both in time and space. The methodology proposed was then applied to evaluate the vulnerability of agricultural drought of major river basins in Korea. First, the three-month SPI data from 59 rain gauge stations over the Korean Peninsula were analyzed by deriving and spatially characterizing the EOFs. The shapes of major estimated EOFs were found to well reflect the observed spatial pattern of droughts. Second, the coefficient time series of estimated EOFs were then fitted by a multivariate time series model to generate the SPI data for 10,000 years, which were used to derive the annual maxima series of areal average drought severity over the Korean Peninsula. These annual maxima series were then analyzed to determine the mean drought severity for given return periods. Four typical spatial patterns of drought severity could also be selected for those return periods considered. This result shows that the southern part of the Korean Peninsula is most vulnerable to drought than the other parts. Finally, the agricultural drought vulnerability was evaluated by considering the potential water supply from dams. In an ideal case, when all the maximum dam storage was assumed to be assigned to agriculture, all river basins in Korea were found to have the potential to overcome a 30-year drought. However, under more realistic conditions considering average dam storage and water allocation priorities, most of the river basins could not overcome a 30-year drought.  相似文献   

A Note on Tree Deaths during the Current (2001–?) Drought in South-eastern Australia     

Bill Semple  Madeleine Rankin  Terry Koen  Guy Geeves 《The Australian geographer》2010,41(3):391-401

Tree deaths over large areas during droughts are uncommon. In the semi-arid zone of New South Wales (NSW) such events were last reported during the prolonged droughts of 1895–1903 and 1939–45, though whether caused solely by drought is open to question. Anecdotal and quantitative evidence during the current prolonged drought (2001–?) in NSW's sub-humid zone (where deaths are localised) and semi-arid zone (where deaths are more extensive) suggest that climatic conditions are comparable to, and perhaps more severe than, those of the earlier prolonged droughts. It is suggested that lack of access to deep soil moisture due to inherent shallow rooting, or due to site conditions, is the most likely cause; and that this may be associated with higher than optimal tree densities in cohorts of trees that arose from previous regeneration events during periods of well above average rainfall. A more thorough examination of the extent and severity of this event is warranted.  相似文献   

Modelling the effect of soil burn severity on soil erosion at hillslope scale in the first year following wildfire in NW Spain   总被引：1，自引：0，他引：1       下载免费PDF全文

Cristina Fernández  José A. Vega 《地球表面变化过程与地形》2016,41(7):928-935

Fire severity is recognized as a key factor in explaining post‐fire soil erosion. However, the relationship between soil burn severity and soil loss has not been fully established until now. Sediment availability may also affect the extent of post‐fire soil erosion. The objective of this study was to determine whether soil burn severity, estimated by an operational classification system based on visual indicators, can significantly explain soil loss in the first year after wildfire in shrubland and other areas affected by crown fires in northwest (NW) Spain. An additional aim was to establish indicators of sediment availability for use as explanatory variables for post‐fire soil loss. For these purposes, we measured hillslope‐scale sediment production rates and site characteristics during the first year after wildfire in 15 experimental sites using 65 plots. Sediment yields varied from 0.2 Mg ha^?1 to 50.1 Mg ha^?1 and soil burn severity ranged from low (1.8) to very high (4.5) in the study period. A model that included soil burn severity, annual precipitation and a land use factor (as a surrogate for sediment availability) as explanatory variables reasonably explained the erosion losses measured during the first year after fire. Model validation confirmed the usefulness of this empirical model. The proposed empirical model could be used by forest managers to help evaluate erosion risks and to plan post‐fire stabilization activities. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

On the generation of drought events using an alternating renewal-reward model   总被引：4，自引：2，他引：4  

D. R. Kendall  J. A. Dracup 《Stochastic Environmental Research and Risk Assessment (SERRA)》1992,6(1):55-68

This research study focused on the hypothesis that extreme drought and high streamflow events come from different independent populations with different probability distributions which need to be studied separately, rather than considering the streamflow population as a whole. The inability of traditional streamflow generator models to consistently reproduce the frequency of occurrence of severe droughts observed in the historical record has been questioned by many researchers. Our study focused on the development of astochastic event generator model which would be capable of doing so. This was accomplished in a two-step process by first generating the drought event, and then deriving the streamflows which comprised that event. The model considered for this analysis was an alternating renewal-reward procedure that cycles between eventon andoff times, and is representative of drought or high streamflow event duration. The reward gained while the event ison oroff represents drought severity or high streamflow surplus. Geometric and gamma distributions were considered for drought duration and deficit respectively. Model validation was performed using calculated required capacities from the sequent peak algorithm.  相似文献