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分析陕甘宁半干旱区特大降水的环流特征及其与一般大、暴雨的环流差异,指出中低纬系统相互作用和下游系统阻挡是产生特大降水的重要条件。热带气旋北上时,存在第二类间接作用,不仅在东风急流下游能出现倒槽暴雨,还有利于热带气旋下游的副热带高压另一侧产生特大降水。 相似文献
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ABSTRACTIndia has been the subject of many recent groundwater studies due to the rapid depletion of groundwater in large parts of the country. However, few if any of these studies have examined groundwater storage conditions in all of India’s river basins individually. Herein we assess groundwater storage changes in all 22 of India’s major river basins using in situ data from 3420 observation locations for the period 2003–2014. One-month and 12-month standardized precipitation index measures (SPI-1 and SPI-12) indicate fluctuations in the long-term pattern. The Ganges and Brahmaputra basins experienced long-term decreasing trends in precipitation in both 1961–2014 and the study period, 2003–2014. Indeterminate or increasing precipitation trends occurred in other basins. Satellite-based and in situ groundwater storage time series exhibited similar patterns, with increases in most of the basins. However, diminishing groundwater storage (at rates of >0.4 km3/year) was revealed in the Ganges-Brahmaputra River Basin based on in situ observations, which is particularly important due to its agricultural productivity. 相似文献
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Khouloud Gader Ahlem Gara Marnik Vanclooster Slaheddine Khlifi Mohamed Slimani 《水文科学杂志》2020,65(8):1300-1315
ABSTRACT Predicting the impacts of climate change on water resources remains a challenging task and requires a good understanding of the dynamics of the forcing terms in the past. In this study, the variability of precipitation and drought patterns is studied over the Mediterranean catchment of the Medjerda in Tunisia based on an observed rainfall dataset collected at 41 raingauges during the period 1973–2012. The standardized precipitation index and the aridity index were used to characterize drought variability. Multivariate and geostatistical techniques were further employed to identify the spatial variability of annual rainfall. The results show that the Medjerda is marked by a significant spatio-temporal variability of drought, with varying extreme wet and dry events. Four regions with distinct rainfall regimes are identified by utilizing the K-means cluster analysis. A principal component analysis identifies the variables that are responsible for the relationships between precipitation and drought variability. 相似文献
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地裂缝是西安市典型的城市地质灾害,地下水位的变化是诱发地裂缝活动的重要因素。以西安地铁六号线暗挖段施工降水为研究背景,基于有限元数值模拟计算,分析了地裂缝场地施工降水引起的地表沉降规律和地层应力变化特征。计算结果表明:当地下水位下降时,地表沉降量上盘大于下盘,地裂缝带两侧地表存在差异沉降的现象,最大差异沉降量与地下水位下降深度近似呈直线关系;不同位置处地表的横向沉降呈现出"Z"形的变化特征,差异沉降区随地裂缝位置的变动而变化,且差异沉降量与横向地表位置近似呈二次函数曲线关系;地层竖向应力随着地下水位下降而增大,地裂缝位置处地层应力存在突变现象,上下盘应力影响区与地层深度近似呈三次函数曲线关系;基于分层总和法计算了地下水位下降时地表沉降量的解析解,并与数值模拟结果进行对比,发现两种方法计算结果基本一致,得到了计算地表最大沉降量的经验公式。研究结果可为地裂缝场地地铁隧道及其他地下工程安全施工提供科学指导。 相似文献
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选取2016年1—12月GPM(Global Precipitation Measurement)卫星的IMERG月尺度降水数据为研究对象,以同时期的气象站点实测降水数据为参考,利用相关系数、标准偏差、相对误差等多种统计分析指标对其在沿海地区估测能力进行评价。结果表明:IMERG月尺度降水量与站点实测降水数据相关性较好,IMERG估测的降水与气象站点实测降水量的时空变化规律也较为一致,但是量化到具体数值而言,其对山区、海岛站的估测能力不及地势平坦的区域;同时,选取降水个例对IMERG日尺度和半小时尺度降水数据的分析表明,日尺度IMERG估测的不同等级降水量也存在偏差,半小时尺度IMERG降水数据对海岛站的降水估测偏高。总体而言,IMERG降水数据对降水的时间变化规律和空间分布格局估测较为合理,但是对山区、海岛地区,其降水估测值还存在偏差,在今后应用中需结合地形特征加以合理利用。 相似文献
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Statistical Downscaling Based on Dynamically DownscaledPredictors: Application to Monthly Precipitation in Sweden 总被引:3,自引:0,他引:3
A prerequisite of a successful statistical downscaling is that large-scale predictors simulated by the General Circulation Model (GCM) must be realistic. It is assumed here that features smaller than the GCM resolution are important in determining the realism of the large-scale predictors. It is tested whether a three-step method can improve conventional one-step statistical downscaling. The method uses predictors that are upscaled from a dynamical downscaling instead of predictors taken directly from a GCM simulation. The method is applied to downscaling of monthly precipitation in Sweden. The statistical model used is a multiple regression model that uses indices of large-scale atmospheric circulation and 850-hPa specific humidity as predictors. Data from two GCMs (HadCM2 and ECHAM4) and two RCM experiments of the Rossby Centre model (RCA1) driven by the GCMs are used. It is found that upscaled RCA1 predictors capture the seasonal cycle better than those from the GCMs, and hence increase the reliability of the downscaled precipitation. However, there are only slight improvements in the simulation of the seasonal cycle of downscaled precipitation. Due to the cost of the method and the limited improvements in the downscaling results, the three-step method is not justified to replace the one-step method for downscaling of Swedish precipitation. 相似文献