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1.
Summary An analysis, based on rain gauge observations, of the time-space variability of dry and wet periods during the last fifty years in eastern China is presented. The Standardized Precipitation Index (SPI) is used to assess the climatic conditions of the area, and principal component analysis (PCA) is applied to capture the pattern of co-variability of the index at different stations. Results suggest that the northern part of eastern China is experiencing dry conditions more frequently from the 1970s onwards indicated by a negative trend in the SPI time series. Long-term fluctuations characterize the SPI signal and contribute to the power spectrum variance at periods ranging from interdecadal to interannual time scales, that is respectively, 24 years and from 16 to 4–3.7 years. These periodic components provide a useful resource for long-term predictability of dry and wet periods in eastern China. 相似文献
2.
Estimation of the monthly precipitation predictability limit in China using the nonlinear local Lyapunov exponent 总被引：2，自引：0，他引：2 
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下载免费PDF全文 By using the nonlinear local Lyapunov exponent and nonlinear error growth dynamics, the predictability limit of monthly precipitation is quantitatively estimated based on daily observations collected from approximately 500 stations in China for the period 1960–2012. As daily precipitation data are not continuous in space and time, a transformation is first applied and a monthly standardized precipitation index (SPI) with Gaussian distribution is constructed. The monthly SPI predictability limit (MSPL) is quantitatively calculated for SPI dry, wet, and neutral phases. The results show that the annual mean MSPL varies regionally for both wet and dry phases: the MSPL in the wet (dry) phase is relatively higher (lower) in southern China than in other regions. Further, the pattern of the MSPL for the wet phase is almost opposite to that for the dry phase in both autumn and winter. The MSPL in the dry phase is higher in winter and lower in spring and autumn in southern China, while the MSPL values in the wet phase are higher in summer and winter than those in spring and autumn in southern China. The spatial distribution of the MSPL resembles that of the prediction skill of monthly precipitation from a dynamic extended-range forecast system. 相似文献
3.
Summary For assessing risk of highly unusual events extreme value statistics needs to be applied, which plays an important role in
engineering practices for water resources design and management. In hydrology, the typical application of extreme value theory
concerns floods in river basins or landslides. The present paper is, instead, focused on the analysis of extreme wet and dry
periods in a sample area (Sicily). First, we have studied monthly precipitation extremes both using the annual maximum and
partial duration methods, and return times have been estimated by standard statistical techniques. Next, we studied the extremes
of the Standardized Precipitation Index (SPI), which has been proposed as an indicator for monitoring wet and dry conditions.
We found considerable differences both in the return periods and in the time location of the extremes. From our study it appears
that the SPI better describes wet and dry periods than the precipitation does. Maps of return times for extreme conditions
in Sicily are also presented, which cluster the territory into areas of different extreme return periods. Finally, the occurrence
of extremes in Sicily has been related to large-scale atmospheric circulation. 相似文献
4.
使用LASG/IAP GOALS耦合模式中的全球大气环流模式分量AGCMR15L9的计算结果，在其他外强迫维持气候值不变的情况下，用方差分析的方法，以外部方差与总方差之比Re作为衡量标准，考察该模式关于海冰的季节和跨季节潜在可预报性的大小。结果发现，从总体上看，北半球海冰变化所造成的潜在可预报性较小，只有在大气低层的一些气候要素，如温度、湿度的结果中，才存在Re＞0.5的现象。潜在可预报性结果的局地特征比较明显，高值往往发生在海冰年际变率大的区域里。与中低纬海温在中高纬地区的影响相比，不排除海冰的作用更大的可能性。另外，如果分区域看，北半球某些区域的海冰，在若干挑选出的其区域海冰面积发生大异常年份中的潜在可预报性可能会比不做挑选的总体结果要大。这说明北半球某些区域海冰在面积发生较大异常的时候，可能对同期或（及）后期环流有着比较重要的影响。 相似文献
5.
Observed changes of drought/wetness episodes in the Pearl River basin, China, using the standardized precipitation index and aridity index 总被引：9，自引：2，他引：7
Monthly precipitation data of 42 rain stations over the Pearl River basin for 1960–2005 were analyzed to classify anomalously wet and dry conditions by using the standardized precipitation index (SPI) and aridity index (I) for the rainy season (April–September) and winter (December–February). Trends of the number of wet and dry months decided by SPI were detected with Mann-Kendall technique. Furthermore, we also investigated possible causes behind wet and dry variations by analyzing NCAR/NCEP reanalysis dataset. The results indicate that: (1) the Pearl River basin tends to be dryer in the rainy season and comes to be wetter in winter. However, different wetting and drying properties can be identified across the basin: west parts of the basin tend to be dryer; and southeast parts tend to be wetter; (2) the Pearl River basin is dominated by dry tendency in the rainy season and is further substantiated by aridity index (I) variations; and (3) water vapor flux, moisture content changes in the rainy season and winter indicate different influences of moisture changes on wet and dry conditions across the Pearl River basin. Increasing moisture content gives rise to an increasing number of wet months in winter. However, no fixed relationships can be observed between moisture content changes and number of wet months in the rainy season, indicating that more than one factor can influence the dry or wet conditions of the study region. The results of this paper will be helpful for basin-scale water resource management under the changing climate. 相似文献
6.
选择标准化降水指数(SPI)刻画旱涝特征,基于云南省1954—2014年间32个气象站点逐月降水量资料,采用经验正交函数(EOF)方法、径向基函数(RBF)空间插值法、小波分析法,分析了近61年来云南省SPI序列、旱涝情态的时间特征和空间格局。结果表明:近61年来,云南省整体呈现干旱趋势(SPI变率为-0.009 1),SPI序列在2000年之后变化更加剧烈、速率加快。旱涝等级时间序列中,偏涝至偏旱年份占88.52%,大旱占4.92%,重旱和大涝均占3.28%,且自2003年以后,发生干旱的次数和强度明显增加。旱灾易发区主要分布于2个片区:景洪-思茅-元江站片区,以及沾益站东北地区;洪涝易发区主要分布于3个片区:临沧-大理-华坪沿线的西部片区,昭通站北部区域,及云南省东南部片区。干旱与洪涝事件发生的频率具有较好的对应性,但干旱事件发生的频率要略高于洪涝事件。EOF分析的第一个模态表明云南省整体呈现一致性的变涝或变旱特征,可能受到大尺度气候特征影响,第二模态可能受到地形因素的控制,第三模态可能与季风、大气环流等多种因素的影响有关;相应的时间系数也印证了云南省整体具有干旱趋势。SPI序列存在准2 a、准6 a、准8 a、准18 a、准28 a的周期性特征,且以准28 a为主周期。 相似文献
7.
明确气候变化背景下大兴安岭林区气候干湿状况特征,揭示其对森林火灾的影响,可为该区域森林火灾管理和森林资源保护提供科学依据。基于大兴安岭林区1974—2016年标准化降水指数（SPI）,采用统计分析和对比分析方法,系统研究不同干湿情景对森林火灾发生次数及过火面积的影响,并讨论不同等级干旱对其影响的异同性。结果表明:1974—2016年,年、季尺度上大兴安岭林区气候均呈湿润化趋势。森林火灾发生次数多（少）和过火面积大（小）与气候的干湿状况（等级）基本一致,但森林火灾的发生次数与气候干湿状况相关更为密切。年尺度上,SPI与火灾次数呈负相关,与过火面积的自然对数则呈较弱的负相关;季尺度上,各季节SPI与对应的林火次数和过火面积自然对数均呈显著的负相关,但与过火面积的相关程度差异较大,以春季相关最为显著,秋季次之,夏季则相对较弱;不同季节SPI与年林火次数和过火面积自然对数呈负相关,前一年冬季SPI对当年火灾次数的贡献最大。可见,气候干湿状况对森林火灾的影响存在明显的滞后效应。SPI不仅能较好地反映区域气候的干湿状况,亦能较好地指示森林火灾发生的可能性及发生火灾的过火面积的相对变化情况,可为森林火灾预测和管理提供科学依据。 相似文献
8.
Prakki Satyamurty Claudia Priscila Wanzeler da Costa Antonio Ocimar Manzi 《Theoretical and Applied Climatology》2013,111(1-2):195-209
The regions where the divergence of vertically integrated water vapor flux, averaged over a season or a year, is positive (negative) are sources (sinks) of moisture for the atmosphere. An aerial river is defined as a stream of strong water vapor flux connecting a source and a sink. Moisture flux, its divergence, and sources and sinks over the tropics of South and Central America and the adjoining Atlantic Ocean are obtained for dry years and for wet years in the Amazon Basin. Results show that the Amazon Basin is a sink region for atmospheric moisture in all seasons and that there are two source regions for the moisture in the basin, one situated in the South Atlantic and the other in the North Atlantic, both located equator-ward of the respective subtropical high-pressure centers. The convergence of moisture increases over the Amazon Basin in austral summer, and at the same time it decreases in the Pacific and Atlantic ITCZs. Box model calculations reveal that the wet years, on the average, present about 55 % more moisture convergence than the dry years in the Amazon Basin. A reduction in the moisture inflow across the eastern and northern boundaries of the basin (at 45°W and at the Equator, respectively) and an increase in the outflow across the southern boundary (at 15°S) lead to dry conditions. The annual mean contribution of moisture convergence to the precipitation over the Amazon Basin is estimated to be 70 %. In the dry years, it lowers to around 50 %. The net convergence of water vapor flux over the basin is a good indicator of the wet or dry condition. 相似文献
9.
长江梅雨的长期变率与海洋的关系及其可预报性研究 总被引：4，自引：0，他引：4
采用最新发布的梅雨国家标准资料,以长江区域梅雨为代表,在分析区域梅雨的多时间尺度变化特征的基础上,从海洋外强迫影响因子角度探讨了梅雨的可预报性来源,进一步综合海洋背景变率和预测模型回报试验讨论梅雨异常的可预报性。结果表明:（1）长江梅雨呈现周期为3-4、6-8、12-16、32、64 a的多时间尺度变化分量和长期减少趋势。其中,3-4 a准周期变化是梅雨异常变化的主要分量。梅雨的干湿位相转变受12-16 a的准周期变化调制,极端涝年易出现在12-16 a准周期变化湿位相和3-4 a变化分量峰值位相叠加的情况。（2）长江梅雨的各准周期变化分量有不同的海洋外强迫背景,是梅雨可预报性的重要来源。与时间尺度较短的年际变化分量相关联的海温关键区主要分布于热带,而与时间尺度较长的年代际或多年代际变化分量相联系的海温关键区则来自中高纬度。3-4 a准周期变化分量的海洋外强迫强信号随季节变化由前冬的ENSO（厄尔尼诺-南方涛动）转为春末夏初的印度洋偶极子（IOD）。6-8和12-16 a年准周期变化分量的海洋强迫关键区主要位于太平洋。准32和准64 a周期振荡则受北太平洋多年代际变化（PDO）和北大西洋多年代际变化（AMO）的共同影响。梅雨的长期变化趋势则与全球变暖背景及以PDO为代表的年代际海洋外强迫因子相联系。（3）尽管梅雨异常与ENSO的正相关关系呈现减弱趋势,但20世纪70年代以后的梅雨异常年际变化分量的可预报性有所增大。（4）将梅雨各变化分量作为预测对象分别建模,进一步构建梅雨异常预测统计模型。采用该模型对近5年梅雨预测进行独立样本检验,有较好的回报效果,验证了梅雨异常年际分量可预报性的稳定性以及基于多时间尺度分离建立梅雨预测模型的优越性。 相似文献
10.
Rainfall characterisation by application of standardised precipitation index (SPI) in Peninsular Malaysia 总被引：1，自引：1，他引：0
Fadhilah Yusof Foo Hui-Mean Jamaludin Suhaila Zulkifli Yusop Kong Ching-Yee 《Theoretical and Applied Climatology》2014,115(3-4):503-516
The interpretations of trend behaviour for dry and wet events are analysed in order to verify the dryness and wetness episodes. The fitting distribution of rainfall is computed to classify the dry and wet events by applying the standardised precipitation index (SPI). The rainfall amount for each station is categorised into seven categories, namely extremely wet, severely wet, moderately wet, near normal, moderately dry, severely dry and extremely dry. The computation of the SPI is based on the monsoon periods, which include the northeast monsoon, southwest monsoon and inter-monsoon. The trends of the dry and wet periods were then detected using the Mann–Kendall trend test and the results indicate that the major parts of Peninsular Malaysia are characterised by increasing droughts rather than wet events. The annual trends of drought and wet events of the randomly selected stations from each region also yield similar results. Hence, the northwest and southwest regions are predicted to have a higher probability of drought occurrence during a dry event and not much rain during the wet event. The east and west regions, on the other hand, are going through a significant upward trend that implies lower rainfall during the drought episodes and heavy rainfall during the wet events. 相似文献
11.
May–July Standardized Precipitation Index (SPI) for the land area of most of Turkey and some adjoining regions are reconstructed
from tree rings for the period 1251–1998. The reconstruction was developed from principal components analysis (PCA) of four
Juniperus excelsa chronologies from southwestern and south-central Turkey and is based on reliable and replicable statistical relationships
between climate and tree ring growth. The SPI reconstruction shows climate variability on both interannual and interdecadal
time scales. The longest period of consecutive drought years in the reconstruction (SPI threshold ≤−1) is 2 yr. These occur
in 1607–1608, 1675–1676, and 1907–1908. There are five wet events (SPI threshold ≥+1) of two consecutive years each (1330–1331,
1428–1429, 1503–1504, 1629–1630, and 1913–1914). A 5-yr moving average of the reconstructed SPI shows that two sustained drought
periods occurred from the mid to late 1300s and the early to mid 1900s. Both episodes are characterized by low variability. 相似文献
12.
The North Atlantic is one of the few places on the globe where the atmosphere is linked to the deep ocean through air–sea
interaction. While the internal variability of the atmosphere by itself is only predictable over a period of one to two weeks,
climate variations are potentially predictable for much longer periods of months or even years because of coupling with the
ocean. This work presents details from the first study to quantify the predictability for simulated multidecadal climate variability
over the North Atlantic. The model used for this purpose is the GFDL coupled ocean-atmosphere climate model used extensively
for studies of global warming and natural climate variability. This model contains fluctuations of the North Atlantic and
high-latitude oceanic circulation with variability concentrated in the 40–60 year range. Oceanic predictability is quantified
through analysis of the time-dependent behavior of large-scale empirical orthogonal function (EOF) patterns for the meridional
stream function, dynamic topography, 170 m temperature, surface temperature and surface salinity. The results indicate that
predictability in the North Atlantic depends on three main physical mechanisms. The first involves the oceanic deep convection
in the subpolar region which acts to integrate atmospheric fluctuations, thus providing for a red noise oceanic response as
elaborated by Hasselmann. The second involves the large-scale dynamics of the thermohaline circulation, which can cause the
oceanic variations to have an oscillatory character on the multidecadal time scale. The third involves nonlocal effects on
the North Atlantic arising from periodic anomalous fresh water transport advecting southward from the polar regions in the
East Greenland Current. When the multidecadal oscillatory variations of the thermohaline circulation are active, the first
and second EOF patterns for the North Atlantic dynamic topography have predictability time scales on the order of 10–20 y,
whereas EOF-1 of SST has predictability time scales of 5–7 y. When the thermohaline variability has weak multidecadal power,
the Hasselmann mechanism is dominant and the predictability is reduced by at least a factor of two. When the third mechanism
is in an extreme phase, the North Atlantic dynamic topography patterns realize a 10–20 year predictability time scale. Additional
analysis of SST in the Greenland Sea, in a region associated with the southward propagating fresh water anomalies, indicates
the potential for decadal scale predictability for this high latitude region as well. The model calculations also allow insight
into regional variations of predictability, which might be useful information for the design of a monitoring system for the
North Atlantic. Predictability appears to break down most rapidly in regions of active convection in the high-latitude regions
of the North Atlantic.
Received: 28 October 1996 / Accepted: 21 March 1997 相似文献
13.
Comprehensive characterization of diversity in global patterns of precipitation variability and change is an important starting point for climate adaptation and resilience assessments. Capturing the nature of precipitation probability distribution functions (PDF) is critical for assessing variability and change. Conventional linear regression-based analyses assume that slope coefficients for the wet and dry tails of the PDF are consonant with the conditional mean trend. This assumption is not always borne out in the analyses of historical records. Given the relationship between sea surface temperature (SST) and precipitation, recent trends in global SST complicate interpretations of precipitation variability and risk. In this study, changes in the PDF of annual precipitation (1951–2011) at the global river basin scale were analyzed using quantile regression (QR). QR is a flexible approach allowing for the assessment of precipitation variability conditioned on the leading empirical orthogonal function (EOF) patterns of global SST that reflect El Niño–Southern Oscillation and Atlantic Multi-decadal Oscillation. To this end, the framework presented (a) offers a characterization of the entire PDF and its sensitivity to the leading modes of SST variability, (b) captures a range of responses in the PDF including asymmetries, (c) highlights regions likely to experience higher risks of precipitation excesses and deficits and inter-annual variability, and (d) offers an approach for quantifying risk across specified quantiles. Results show asymmetric responses in the PDF in all regions of the world, either in single or both tails. In one instance, QR detects a differential response to the leading patterns of SST in the Tana basin in eastern Africa, highlighting changes in variability as well as risk. 相似文献
14.
Trends in evaporation of a large subtropical lake 总被引：1，自引：0，他引：1
In order to further investigate the capability of the Standardized Precipitation Index (SPI) to identify flood/drought events, monthly precipitation data from 26 precipitation stations and monthly discharge data from four hydrological stations from 1960 to 2006 in the Minjiang River basin were used to analyze the correlations between multiple time scales of the SPI and river discharge. The SPI series that had a maximum correlation with discharge was chosen to detect flood/drought events in the basin, and the results were compared to historical flood/drought events. The results indicated the following. (1) High Pearson correlations between the SPI and discharge were identified at shorter time scales (1 to 3 months), and the maximum correlation was found on the time scale of 2 months. (2) Five floods among the six largest historical flood events in the Minjiang River basin were identified with the 2-month SPI, but the SPI does have shortcomings in identifying more general floods. The SPI also identified major drought events that were consistent with historical data. This demonstrates that the 2-month SPI is an effective indicator for the identification of major flood/drought events in the Minjiang River basin. 相似文献
15.
渭河流域干旱特征及干旱指数计算方法初探 总被引：7，自引：1，他引：7
利用游程分析、马尔可夫平稳概率、随机过程等方法分析了渭河流域的干旱特征。结果表明，近44年（1958-2001年）渭河流域降水连续多水（少水）期多持续2～3年，单独多（少）水年出现的概率比连续多水（少水）年的概率大，连少年的概率比连多年的概率大，平均连续少水年数大于平均连续多水年数；枯（丰）水与偏丰（偏枯）之间的转移突变较大，对用水可能带来不利影响；偏枯年出现的概率最大，偏丰年次之，丰水年最小；渭河流域连续少水2～3年不仅发生频率较高，而且干旱强度也较大。同时根据降水和同期气温、天然径流量资料建立了适用于渭河流域的S干旱指数。 相似文献
16.
This study presents a multitemporal climatology of water excess and shortage during the 20th century in the La Plata Basin. The climatology is based on 0.5o?×?0.5o grid across the region. We transform monthly precipitation series for each point into index series at different time scales using the Standardized Precipitation Index (SPI). A month is under water excess (shortage) conditions at different time scales (i?=?6, 9, 12, and 18 months), when SPI[i](j)?>?1.5 (SPI[i](j)?<?1.5), where j is the current month. Trends in precipitation were determined using mean regional series of average values over the entire basin. A month when more than 30% of the total basin is under water excesses (shortages) is defined as an excess (shortage) critical month. From the vulnerability point of view, we analyzed the occurrence of critical months. The number of excess critical months increase with time scale of index, and almost all the critical months occurred after 1950 as a consequence of the low-frequency precipitation pattern. That means a noticeable increase in the vulnerability to extended excesses (more than 30% of the area under water excesses) after 1950, especially over the Upper Paraná and the Uruguay basins. For shortage critical months, the behavior depends on time scales. At large time scale (18 and 12 months), almost all the shortage critical months occurred in the period 1901–1950 and only at shorter time scale (9 and 6 months), some critical months appeared after 1950. That means a noteworthy decrease in the basin vulnerability to extended water shortage after 1950 and a moderate decrease in vulnerability to generalized shortage. If we analyze the frequency and mean duration of water excess and shortage events across the basin, we can appreciate that there is a tendency to relate higher frequency regions with regions with lower mean duration events, and conversely. 相似文献
17.
Based on daily precipitation records at 75 meteorological stations in Hunan Province, central south China, the spatial and temporal variability of precipitation indices is analyzed during 1961–2010. For precipitation extremes, most of precipitation indices suggest that both the amount and the intensity of extreme precipitation are increasing, especially the mean precipitation amount on a wet day, showing a significant positive trend. Meanwhile, both of the monthly rainfall heterogeneity and the contribution of the days with the greatest rainfall show an upward trend. When it comes to rainfall erosivity, most of this province is characterized by high values of annual rainfall erosivity. Although the directions of trends in annual rainfall erosivity at most stations are upward, only 6 of the 75 stations have significant trends. Furthermore, the spatial and temporal variation of dryness/wetness has been assessed by the standardized precipitation index (SPI). The principal component analysis (PCA) was applied to the SPI series computed on 24-month time scales. The results demonstrated a noticeable spatial variability with three subregions characterized by different trends: a remarkable wet tendency prevails in the central and southern areas, while the northern areas are dominated by a remarkable dry tendency. 相似文献
18.
Potential predictability of the Asian summer monsoon on monthly and seasonal time scales 总被引：1，自引：0，他引：1
Summary ¶The potential predictability of the monthly and seasonal means during the Northern Hemisphere summer and winter is studied by estimating the signal-to-noise ratio. Based on 33 years of daily low-level wind observations and 24 years of satellite observations of outgoing long wave radiation, the predictability of the Asian summer monsoon region is contrasted with that over other tropical regions. A method of separating the contributions from slowly varying boundary forcing and internal dynamics (e.g., intraseasonal oscillations) that determine the predictability of the monthly mean tropical climate is proposed. We show that the Indian monsoon climate is only marginally predictable in monthly time scales as the contribution of the boundary forcing in this region is relatively low and that of the internal dynamics is relatively large. It is shown that excluding the Indian monsoon region, the predictable region is larger and predictability is higher in the tropics during northern summer. Even though the boundary forced variance is large during northern winter, the predictable region is smaller as the internal variance is larger and covers a larger region during northern winter (due to stronger intraseasonal activity). Consistent with the estimates of predictability of monthly means, estimates of potential predictability on seasonal time scales also indicate that predictability of seasonal mean Indian monsoon is limited.Received December 6, 2002; accepted March 16, 2003
Published online: June 12, 2003 相似文献
19.
基于昌吉地区7个气象站1961－2020年降水量资料，计算昌吉地区作物生长季标准化降水指数（SPI-7）。运用趋势分析法、M-K突变检验法和小波分析法探究了昌吉地区作物生长季SPI-7指数的年际和年代变化特征；在此基础上分析了作物生长季干旱的站次比和干旱强度的年际变化,并结合该区实际发生的旱灾对SPI进行了验证。结果表明：1961—2020年昌吉地区作物生长季标准化降水指数以0.08/10 a的速率呈微弱的正趋势（变湿），在年代变化趋势中呈现出变干-变湿-变干的变化波动, 1981年标准化降水指数由低到高突变；干旱强度呈增加趋势，干旱发生的区域面积有轻微减少的趋势；干旱强度在全区范围内主要为轻旱和中旱等级，并表现为全域性干旱和区域性干旱；空间分布上看干旱率最高区域在东部地区，轻旱主要集中在东部，中旱、重旱和特旱集中在西部地区，干旱强度大的区域大致分布在西部地区；在周期性变化方面，SPI指数存在着6年、9年、16年周期震荡；历史旱灾与SPI指数干旱评价结果吻合率较高，SPI指数在昌吉地区作物生长季的干旱监测与分析中具有较好的实用性。 相似文献
20.
Sharon E. Nicholson 《Climatic change》2001,50(3):317-353
This article describes a historical archive of proxy and actual precipitation data that extends the African climate record back to the early nineteenth century. The `proxy' archive includes verbal, documentary references which contain information related to rainfall conditions, such as references to famine, drought, agriculture or the nature of the rainy season. The precipitation archive includes all observations made in Africa during the nineteenth century. It consists of records for 60 stations in Algeria, 87 stations in South Africa and 304 stations scattered over the rest of Africa. Information is particularly plentiful for the 1880s and 1890s. The two parts have been be combined into a semi-quantitative regional data set indicating annual rainfall conditions in terms of anomaly classes (e.g., normal, dry, wet). This data set extends from the early nineteenth century to 1900 and distinguishes seven anomaly classes, using numbers ranging from –3 to +3 to represent very wet, wet, good rains, normal, dry, drought, and severe drought. The regionalization is based on 90 geographical regions shown via studies of the modern precipitation record to be climatically homogeneous with respect to the interannual variability of rainfall. The regional aggregation allows the voluminous fragmentary information available in historical sources to be used systematically to produce multi-year time series that can be directly integrated into the modern record for each region. The resultant time series can also be subjected to statistical analysis, in order to investigate nineteenth century climate over Africa. Spatial detail is added to the data set by utilizing a unique methodology based on climatic teleconnections established from studies of rainfall variability over Africa. The historical information and station records have been combined into a file containing a regional anomaly value for up to 90 geographic regions and the years 1801–1900. Gaps necessarily remain in the matrix, but as early as the 1820s over 40 regions are represented. By the 1880s generally around 70 regions or more are represented. 相似文献