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1.
Desmond Manatsa Leonard Unganai Christopher Gadzirai Swadhin K. Behera 《Natural Hazards》2012,64(2):1187-1207
Farmers?? adaptation to climate change over southern Africa may become an elusive concept if adequate attention is not rendered to the most important adaptive tool, the regional seasonal forecasting system. Uptake of the convectional seasonal rainfall forecasts issued through the southern African regional climate outlook forum process in Zimbabwe is very low, most probably due to an inherent poor forecast skill and inadequate lead time. Zimbabwe??s recurrent droughts are never in forecast, and the bias towards near normal conditions is almost perpetual. Consequently, the forecasts are poorly valued by the farmers as benefits accrued from these forecasts are minimal. The dissemination process is also very complicated, resulting in the late and distorted reception. The probabilistic nature of the forecast renders it difficult to interpret by the farmers, hence the need to review the whole system. An innovative approach to a regional seasonal forecasting system developed through a participatory process so as to offer a practically possible remedial option is described in this paper. The main added advantage over the convectional forecast is that the new forecast system carries with it, predominantly binary forecast information desperately needed by local farmers??whether a drought will occur in a given season. Hence, the tailored forecast is easier for farmers to understand and act on compared to the conventional method of using tercile probabilities. It does not only provide a better forecasting skill, but gives additional indications of the intra-seasonal distribution of the rainfall including onsets, cessations, wet spell and dry spell locations for specific terciles. The lead time is more than 3?months, which is adequate for the farmers to prepare their land well before the onset of the rains. Its simplicity renders it relatively easy to use, with model inputs only requiring the states of El Nino Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) climate modes. The developed forecast system could be one way to enhance management of risks and opportunities in rain-fed agriculture among small-holder farmers not only in Zimbabwe but also throughout the SADC region where the impact of ENSO and/or IOD on a desired station rainfall is significant. 相似文献
2.
E. Olukayode Oladipo 《Natural Hazards》1993,8(2):171-188
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. 相似文献
3.
《Geoforum》1987,18(3):321-331
Sudan has been at the centre of the debate of drought and famine issues over the last 3 or 4 years. While the ideas of a simplistic casual link between these two phenomena has been partially slain, there still remains the desire in some circles to find a scapegoat for famine. Drought remains one of the readiest to hand. Rather than being seen as a basic characteristic of the rainfall resource which requires management, drought is seen as such an abnormality that it provides too convenient an excuse for the failure of agriculture, inadequacy of water supplies, exhaustion of soils and other environmental phenomena that have afflicted Sudan within the last 3–4 years (and longer). Such an attitude is in danger of converting rainfall in Sudan from an asset to a liability. This paper examines rainfall in Sudan as a resource and hence a potential asset. Drought is recognised as an inherent characteristic of that resource and its management discussed. It is suggested that the performance of indigenous traditional adaptive strategies has contrasted favourably with those of Governmental institutions. Reasons for this are given. Some broad options for future perspectives on the effective management of rainfall are outlined. 相似文献
4.
Drought in the Sahel 总被引：3，自引：0，他引：3
The Sahel region of West Africa is well known as a region of environmental degradation. The reported incidence of desertification
has been challenged but persistent and widespread drought is still widely accepted. Drought, defined solely as a function
of rainfall, is believed to have commenced in the early 1970s and continued through to the present. It is usually defined
as a meteorological phenomenon and standardised rainfall anomalies are employed to indicate the severity of negative departures
from the ‘norm’. There are several difficulties with this approach. The period of standardising rainfall has changed from
1931–1960 to 1961–1990 but the impacts on drought occurrence have not been fully determined. The spatial aggregation of rainfall
anomalies may mask important local variation and the purely statistical approach to defining drought takes little account
of human impact. The first two issues, averaging period and spatial aggregation, are investigated through an analysis of rainfalls
in Continental Sahel (Bukina Faso, Mali and Niger). A new classification of drought classes is suggested. Despite the clear
evidence of negative rainfall anomalies for rainfalls aggregated across the Sahel region, it is found that the averaging period
has a significant impact on our perceptions of the occurrence of what can be considered to be meteorological drought according
to the definition employed and that there is significant spatial variation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
Lingbo Xiao 《地球科学进展》2020,35(5):478-487
Based on records on famine kept in historical documents, 2950 famine events counted with “county time” in North China during 1736-1911 were collected, and annual famine index series in North China was reconstructed using weighted average method according to the severity of famine. Spatio-temporal distribution of famine and its relationship with climate, disaster and harvest was analyzed. The research shows that variation of temperature and precipitation has significant negative correlation with poor harvest and famine. The drought has a more significant correlation with harvest and famine than flood. In 1736-1795 when was at the peak of the Qing dynasty, the sensitivity of poor harvest and famine to drought was significantly lower than in 1796-1911 when was in decline, because effective social response to disaster could reduce the risk of poor harvest and famine. Using the kernel density estimation method, three main high risk areas of famine were indentified: Fen River Valley in south Shanxi Province, south-central He'nan Province, and the junction of Hebei, Shandong and He'nan Province. In general, there is significant corresponding relationship between the spatial distribution of drought, poor harvest and famine, however, abnormally high probability of famine in south-central He'nan Province might be related to local special socio-economic vulnerability. This study would enhance our understanding of the nature of interactions between climate change and socioeconomic system. Further research would focus on the mechanism by which famine originated in the past, and the pathway through which climatic impacts were delivered in human society. 相似文献
6.
基于灾损评估的青海省牧草干旱风险区划研究 总被引：3，自引：1，他引：2
在全球气候变暖的大背景下, 表现出温度升高、 降水变率加大的区域响应, 造成极端天气气候事件、 气象灾害加剧. 基于青海省1961-2010年47个气象站和20个农气站的气象资料、 牧草的实际产量以及牧草的理论产量等资料, 采用相关分析、 线性回归等方法, 在分析致灾因子危险性、 牧草相对产量的基础上, 确定了青海省牧区牧草干旱风险评估的实际阈值.通过海拔、 经度、 纬度、 牧草旱灾发生频次的拟合方程, 结合GIS平台对青海省牧草干旱进行风险区划.结果表明: 青南牧区西部、 环青海湖地区、 柴达木盆地东部边缘地区、 祁连山地区为易受旱灾影响的特高风险或高风险区域;青南牧区西南部为中风险区域;低风险区域主要在青南牧区东南部, 区划结果基本上于历史旱灾的实际情况相吻合, 区划结果旨在为青海省牧区牧业良性发展提供科学依据. 相似文献
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近30年雷州半岛季节性气象干旱时空特征 总被引：1，自引：0，他引：1
为进一步分析日尺度有效干旱指数(Effective Drought Index,EDI)的适应性,基于雷州半岛1984~2013年逐日降水资料进行验证,对比EDI和月尺度标准化降水指数(Standardized Precipitation Index,SPI)的干旱识别效果,进而结合线性趋势、M-K趋势检验和空间插值方法 ,分析雷州半岛季节性气象干旱时空特征。结果表明:(1)日尺度EDI和6个月时间尺度SPI(SPI-6)适用于雷州半岛的干旱监测,但EDI对严重干旱和突发干旱的识别比SPI-6更准确;(2)1984~2013年,雷州半岛秋冬季干旱频率和干旱站次比均呈减少趋势,但春夏季干旱频率和干旱站次比略有增加趋势;(3)春旱频率从南向北递增,重旱高频地区位于西北部,而夏季重旱高频区位于西部沿海;秋旱南部重于北部,高频中心在雷中西部沿海和曾家周边;冬季重旱以西部沿海、雷州市和徐闻县交界处频率最高。 相似文献
10.
Donald A. Wilhite 《Natural Hazards》1996,13(3):229-252
Drought is a normal, recurrent feature of climate that affects virtually all countries to some degree. The number of drought-induced natural disasters has grown significantly since the 1960s, largely as a result of increasing vulnerability to extended periods of precipitation deficiency rather than because of an increase in the frequency of meteorological droughts. This increase in drought-induced natural disasters has resulted in a considerable growth of interest in drought mitigation and preparedness worldwide. The purpose of a national preparedness plan is to reduce societal vulnerability to drought through the adoption of preventive, anticipatory policies and programs. This paper describes a ten-step planning process that nations can follow to develop a drought preparedness plan. This process, originally developed in 1987, has been the basis of discussions at training seminars on drought preparedness for developing nations in Africa, Asia, and Latin America. It has also been adopted, with appropriate modifications, by state or provincial governments and by municipalities. The process is intended to be flexible so that governments can add, delete, or modify the suggested steps, as necessary.Published as Paper No. 10946, Journal Series, Nebraska Agricultural Research Division. The work reported here was conducted under Nebraska Agricultural Research Division Project 27-007. This material is based in part upon work supported by the National Science Foundation under Grant ATM-8704050. 相似文献
11.
Peasant farming is the most important economic activity in many parts of Africa’s semi-dry and dry sub-humid environment, and a key impediment to its success has remained largely the erratic rainfall regime, especially since the great Sahelian drought of 1969–1973. This variability and the response it has engendered have motivated the development of schemes for determining these phases of the rainfall regime. This paper reviews some of the existing methodologies for determining the effective onset date of the rain (the most critical to the farmer), highlights some of their drawbacks and proposes a new rainfall-only scheme (Intra-seasonal Rainfall Monitoring Index—IRMI) which seeks to address the identified gaps. Results of a test of efficacy have shown IRMI’s characterization of rainfall seasons between 1970 and 1999 completely in agreement with what has been documented in a large body of literature on this subject. In addition, results have shown that though onset dates appear to have occurred earlier in the 1990s than in the 1980s and 1970s, inter-seasonal variability actually got progressively worse from the 1970s to the 1990s underscoring the urgent need to put in place reliable forecast schemes in aid of peasant farming. Consequently, the scheme should be adopted for determining the effective onset of rains and commencement of intensive planting across the region. 相似文献
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自然界水循环中的水量平衡原理与干旱研究 总被引：1，自引：1，他引：0
概述了国际、国内干旱研究概况。指出区域多年平均降水量的多少,反映了区域中水资源对生态、经济发展承载力的大小。农业生产中把防止土壤蒸发措施叫抗旱;水利建设中拦河筑坝、引水灌溉、凿井汲水,叫兴修水利抗旱救灾。因此干旱的实质是径流消退、土壤蒸发自然衰减并达到区域内水资源对生态和经济发展的承载能力下降到某一限度或阀值的称谓,如人们感官中的小旱、大旱等。根据径流消退公式和土壤蒸发衰减曲线,参照大风、地震研究方法,输入降水、逐日蒸发观测值,即可成功实现统一干旱标准的实时旱情监测。 相似文献
14.
G. Nageswara Rao 《Journal of Earth System Science》1999,108(4):327-332
Rainfall variability over a river basin has greater impact on the water resource in that basin. With this in view, the variability
of the monsoon rainfall over the Godavari river basin has been studied on different time scales. As expected, the monsoon
rainfall in Godavari basin is more variable (17%) than the all-India monsoon rainfall (11%) during the period of study (1951–90).
Similarly, inter-annual variability of the monsoon rainfall on smaller time scales is found to be still higher and increases
while going on from seasonal to daily scales. An interesting observation is that the intra-seasonal variability of the monsoon
rainfall has a significant negative relationship (CC= −0.53) with the total seasonal rainfall in the basin. 相似文献
15.
Analysis of fifty four (1951–2004) years of daily energetics of zonal waves derived from NCEP/NCAR wind (u and υ) data and daily rainfall received over the Indian landmass (real time data) during southwest monsoon season (1 June–30 September)
indicate that energetics (momentum transport and kinetic energy) of lower tropospheric ultra-long waves (waves 1 and 2) of
low latitudes hold a key to intra-seasonal variability of monsoon rainfall over India.
Correlation coefficient between climatology of daily (122 days) energetics of ultra-long waves and climatology of daily rainfall
over Indian landmass is 0.9. The relation is not only significant but also has a predictive potential. The normalised plot
of both the series clearly indicates that the response period of rainfall to the energetics is of 5–10 days during the onset
phase and 4–7 days during the withdrawal phase of monsoon over India. During the established phase of monsoon, both the series
move hand-in-hand. Normalised plot of energetics of ultra-long waves and rainfall for individual year do not show marked deviation
with respect to climatology. These results are first of its kind and are useful for the short range forecast of rainfall over
India. 相似文献
16.
Rainfall Variability and Changes in Southern Africa during the 20th Century in the Global Warming Context 总被引：2，自引：0，他引：2
Rainfall variability and changes in Southern Africa over the 20th century areexamined and their potential links to the global warming discussed. After a shortreview of the main conclusions of various experiments with Global AtmosphericModels (GCM) forced by increased concentrations of greenhouse gases for SouthernAfrica, a study of various datasets documents the observed changes in rainfall featuresat both daily and seasonal time steps through the last century. Investigations of dailyrainfall parameters are so far limited to South Africa. They show that some regionshave experienced a shift toward more extreme rainfall events in recent decades.Investigations of cumulative rainfall anomalies over the summer season do notshow any trend to drier or moister conditions during the century. However, closeexamination reveals that rainfall variability in Southern Africa has experiencedsignificant modifications, especially in the recent decades. Interannual variabilityhas increased since the late 1960s. In particular, droughts became more intense andwidespread. More significantly, teleconnection patterns associated with SouthernAfrican rainfall variability changed from regional before the 70s to near global after,and an increased statistical association to the El Niño – Southern Oscillation (ENSO) phenomenon is observed. Numerical experiments with a French GCM indicate that these changes in teleconnections could be related to long-term variations in the Sea-Surface-Temperature background, which are part of the observed global warming signal. 相似文献
17.
基于CI指数的甘肃省黄土高原地区气象干旱的变化趋势分析 总被引：6，自引：1，他引：5
基于甘肃省黄土高原区33个气象站1962-2010年气象资料, 利用综合气象干旱指数(CI)对其近50 a的干旱频率和平均持续时间的空间分布、 干旱强度趋势变化和极端干旱事件频次进行了分析, 此基础上应用基于分型理论的R/S方法对干旱强度未来变化趋势进行了预测. 结果表明: 甘肃省黄土高原区干旱发生频率和多年平均持续天数在兰州-靖远一带和庆阳北部属于高值区, 而岷县、 渭源一带属于低值区; 106° E以西"临洮-通渭-天水"一带和庆阳东南部是干旱变幅最大的地方. 20世纪90年代以来, 干旱强度增大的较快, 四季均呈现出干旱强度变大的趋势, 其中春、 秋季干旱强度加剧的趋势明显, 夏季近10 a都处于非常严重的干旱状态, 但未通过0.01的显著性检验; 20世纪60年代至今, 极端干旱事件发生频次快速增多. 四季干旱强度Hurst指数H 均大于0.5, 同时分维数D 均小于1.5, 因此, 未来一段时间干旱强度仍然保持与过去相一致的变化趋势. 研究结果可为相关部门制定相应抗旱对策提供科学依据. 相似文献
18.
Groundwater use in India, and many developing countries, is linked to livelihood and well-being of village communities. It is, therefore, important to characterise groundwater behaviour and resilience and identify strategies that will help to improve the sustainability of groundwater supplies. The concept of Standardised Precipitation Index (SPI) has been widely used for analysing rainfall drought. In this study, we adapt SPI to understand watertable fluctuations and assess resilience of groundwater supplies vis-à-vis rainfall variability from one year to the next. The modified SPI, called Groundwater Resilience Index (GRI), represents a normalized continuous watertable elevation variability function. The index is applied to two districts, viz., Udaipur and Aravalli in Rajasthan and Gujarat, India, respectively, to assess its usefulness. To evaluate the association of rainfall variability with groundwater depth fluctuation, SPI was also calculated. The study showed that GRI varies less than SPI, indicating that groundwater availability is less variable than the rainfall in both districts. This means that groundwater increases reliability of water supply for irrigation in both districts. The estimated SPI and GRI at 6-month intervals for the study period show that even though the groundwater is not stressed (normal condition in 75% of the months observed), there is variation in resilience of the aquifer system to drought and extreme events. Overall, the study indicated that the proposed GRI can be a useful tool for understanding watertable fluctuations and assessing groundwater resilience, especially to prioritise areas for groundwater recharge when funds for recharge works are limited. 相似文献
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20.
An Analysis of Spatial and Temporal Dimension of Drought Vulnerability in Turkey Using the Standardized Precipitation Index 总被引：3，自引：1，他引：2
Drought has become a recurrent phenomenon in Turkey in the last few decades. Significant drought conditions were observed during years of late 1980s and the trend continued in the late 1990s. The countrys agricultural sector and water resources have been under severe constraints from the recurrent droughts. In this study, spatial and temporal dimensions of meteorological droughts in Turkey have been investigated from vulnerability concept. The Standardized Precipitation Index (SPI) method was used to detail geographical variations in the drought vulnerability based on frequency and severity of drought events at multiple time steps. Critical (threshold) rainfall values were derived for each station at multiple-time steps in varying drought categories to determine least amount of rainfall required to avoid from drought initiation. The study found that drought vulnerability portrays a very diverse but consistent picture with varying time steps. At regional scale, south-eastern and eastern Anatolia are characterized with moderate droughts at shorter time steps, while the occurrence of severe droughts at shorter time steps is observed at non-coastal parts of the country. A similar picture was observed with very severe droughts. The critical (threshold) values exhibited rising numbers during the growing season at 3-month step in the South-eastern Anatolia, which might have significant consequences considering presence of large irrigation projects under-development in the region. In general, rainfall amounts required for non-drought conditions decrease from the coastal parts toward the interiors with increasing time steps. 相似文献