Some aspects of the spatial characteristics of drought in northern Nigeria

A long-period instrumental data set (1916–1987) of monthly growing season (April–October) rainfall totals for 34 stations in northern Nigeria is used to quantify drought following the method of H. N. Bhalme and D. A. Mooley. It is established that there are remarkable seasonal changes in the patterns of wetness and dryness over the region with no consistent recurrent spatial patterns in the moisture anomalies. In general, large-scale droughts only rarely cover the region as a whole, and there are distinct spatial differences dominating the wet and dry years. The length and severity of drought varies from sub-area to sub-area with very low interannual persistence. Although discrete areas do catch the brunt of drought on a year-by-year basis, drought occurrence in the region is largely sporadic in its spatial distribution. The rather noisy spatial characteristics of drought in northern Nigeria suggests that the seasonal shift in the Intertropical Discontinuity (ITD) is not likely the most important causal mechanism of drought in the region.     

近三十年来非洲的旱灾与环境变化

本文简要介绍了近三十年来非洲旱灾的基本情况,分析了其形成的原因,并指出,总的说来,干旱是形成非洲旱灾的一个自然因素,但它不等于旱灾.从环境的角度来看,非洲旱灾更重要的原因是人类不适当的土地利用和管理.文章最后提出了非洲防止旱灾的若干战略原则和建议.     

全球增暖下我国旱涝灾害可能情景的初步研究

在全球变暖的情况下,我国东南沿海、西南、西北、内蒙古和东北部分地区,洪涝灾害可能增加;而黄河中游以南和华北平原干旱可能增加.这一变化特征与本世纪暖期降水分布变化,以及与CO_2倍增情况下气候模似结果基本一致.     

应用土壤水模拟模型研究区域干旱

旨在应用平原地区土壤水模拟模型，给出区域旱精分析所需的干旱信息。以多年平均土壤含水量为判断旱情发生的临界函数，经过统计分析后，提出了一种适用于平原地区分析 区域旱情严重程度的实用方法和拟定评价旱情的定量标准。     

低纬和中高纬度火山爆发与我国旱涝的联系

根据５００年旱涝等级资料，采用时序迭加方法，分析了低纬和中高纬火山爆发对我国降水的影响。此外，还对１６００－１９７９年南方涛动指数的变化进行了类似的分析。结果表明，低纬和中高纬火山爆发发后全国旱涝分布型和部分地区降水变化趋势有很大差异。爆发当年华北就可能明显变旱，而次年长江流域才出现明显的降水异常。计算不明，１９９１年皮纳图博火山及去仙岳火山爆发与江淮特大洪涝有直接联系的可能性不大。     

Drought monitoring

Drought detection, monitoring and indices are closely related to its definition. The specific definition chosen for a particular drought analysis will affect the procedures one uses in drought detection and monitoring. The traditional Palmer Drought Severity Index (PDSI) has been proven to be ineffective in regions of predominantly irrigated agriculture.The recently developed ALERT (Automated Local Evaluation in Real Time) system is proposed for use in monitoring the spatial and temporal variations of drought in real time. The ALERT system uses standardized instruments, radio frequencies, software and hardware. It was originally developed as a flash flood waming system by local flood control districts and the National Weather Service. However, now it has expanded to over 100 other uses in the areas of natural and man-made disaster detection and warning. The successful ALERT system indicates the need for the continued development of a national drought monitoring index that is applicable to a wide range of climate, hydrologic and water resource environments.     

刚毛柽柳种子萌发对盐分与干旱胁迫的响应

通过对不同温度、盐分和干旱胁迫对刚毛柽柳种子萌发实验研究影响,结果表明:刚毛柽柳种子的适宜萌发温度范围为10~35℃,萌发率高达80%以上,且萌发迅速。不同浓度NaCl溶液对刚毛柽柳种子萌发有明显抑制作用,种子萌发率随NaCl溶液浓度的增大而下降,到0.7 mol/L时,萌发率仅为1.67%,种子发芽受到抑制。相同渗透势PEG-6 000溶液中的萌发率低于NaCl溶液,渗透势为-0.5 MPa是二者影响作用的分界点。渗透势为-1.8 MPa时,萌发率已急剧下降到0,其对种子萌发的抑制作用大于NaCl溶液。将在两溶液中处理10天的种子转移至蒸馏水后,随着NaCl溶液浓度的增大,萌发恢复率逐渐升高,0.7 mol/L时,萌发恢复率为60%;随着PEG-6 000溶液浓度增大,萌发恢复率先升高后降低,渗透势为-1.4 MPa时,种子萌发恢复率达到最大为67.5%,但两种处理下种子的最终萌发率(总萌发率)都低于在蒸馏水中的。     

内蒙古地区2001年夏季气候特征及前兆信号分析

2001年夏季，内蒙古地区发生了继1999、2000年连续两年的干旱之后的较为严重的全区性干旱。通过分析2001年内蒙古地区夏季气候特征及预测信息，研究内蒙古夏季（1739－2000年中西部地区、1774－2000年东部地区）旱涝气候变化规律，探讨影响内蒙古地区夏季干旱前期信息的变化特征。结果表明，严重干旱年多发生在La Nina事件峰值年次次，环流特征为北半球极涡强度前冬弱后冬强，自上年5月至当年4月呈现出鄂霍次克海高压偏强副高偏弱，并持续3－7个月，继而转成鄂霍次克海高压偏弱副高偏强，并持续2－6个月，可将这些特征作为内蒙古地区夏季严重干旱的前兆信号。     

干旱条件下夏玉米耗水分析

根据田间试验结果，分析干旱年份夏玉米不同发育阶段耗水状况，对比了不同日降水量对玉米田3米剖面的水分分布状况的影响，讨论了土壤失熵过程中的不同深度的水分的变化以及土壤水对玉米干物质积累的影响，为干旱年份玉米水分的科学管理提供依据。