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1.
The high variability of the Mediterranean climate from year to year and within each year makes it difficult to assess changes that could be associated with a climate change. In this paper some indices, such as changes in the precipitation concentration during the year, maximum 1-day and 5-day precipitation, number of wet days (total and those with precipitation higher than the 75th and 95th percentile), magnitude and frequency of extreme events (considered as the rainfall higher than that corresponding to the 99th percentile), fraction of annual total precipitation due to events exceeding the 95th and 99th percentile, strength of the events, and length and frequency of dry period (days between consecutive rains) are evaluated for the Penedès-Anoia region (NE Spain). A 80-year daily dataset (1923–2002) and two 40-year series were used to assess possible trends. The indices indicate an increase in precipitation in winter and summer and a positive trend of concentration in autumn, with a higher number of extreme events separated by longer dry periods. The total number of wet days per year increased, although it was irregularly distributed over the year, with an increase in the extremes and in the fraction of total rainfall that these events represent in autumn and winter, and with an increase of the strength of the events in autumn. These changes in rainfall distribution have negative effects on water availability for crops and contribute to accelerate erosion processes in the area.  相似文献   

2.
The first principal component (PC1) of seasonal rainfall anomalies in central Chile during winter (June–August) is used to analyze the circulation anomalies related to wet and dry conditions, when near-normal or neutral SST anomalies are observed in the equatorial Pacific, i.e., during non-ENSO conditions. Eight wet and eight dry winter seasons were defined as the upper and lower terciles of PC1 for 24 non-ENSO winters in the period 1958–2000. Unlike the single process attributed to ENSO, during non-ENSO winter seasons, there are several sources triggering or modifying the propagation of the stationary waves that impact the rainfall regime in central Chile. Unfortunately, the multiple processes that seem to be involved in the modulation of the interannual rainfall variability in central Chile, as seen in this work, limit the predictability of rainfall during non-ENSO conditions.  相似文献   

3.
This paper presents the analysis of mean daily temperature and precipitation from 1950 to 2010 in an area with Mediterranean climate of NE Spain including some coastal areas near Barcelona and the Penedès and Camp de Tarragona Depressions located between the Coastal Mountain Range and the Mediterranean Sea. Their variability, with especial attention to the frequency of extreme events, was analysed by using 18 indexes: seven for temperature and 11 for precipitation were analysed for four meteorological observatories. A multivariate analysis was performed in order to analyse the temperature and precipitation trends. During the analysed period, an increase in mean annual maximum temperature was observed in all observatories ranging between 1.5 and 2.2°C associated with an increase in the number of days with high extreme temperatures. Minimum temperature only increased significantly in the coast observatories (about 1.4°C). By seasons, temperature trends were greater at Vilafranca del Penedès and Barcelona observatories and lower at Reus airport. Maximum spring temperature increased between 1.5 and 2.5°C, summer temperature increased between 1.6 and 2.5°C and autumn temperature increased by up to 2.2°C. Precipitation presented a high variability from year to year, without significant trends. The most significant results were related to the dry conditions observed in spring 2000s, the wet conditions recorded in summer 2000s and 1980s and the longer dry periods in autumn 2000s. The increase of temperatures determined the increase of evapotranspiration, and due to the higher irregular distribution, water deficits for crop development were recorded. An advance of phenological dates and a reduction of grape yield are associated to climate trends.  相似文献   

4.
It is proposed that, land?Catmosphere interaction around the time of monsoon onset could modulate the first episode of climatological intraseasonal oscillation (CISO) and may generate significant ??internal?? interannual variation in the Indian summer monsoon rainfall. The regional climate model RegCM3 is used over Indian monsoon domain for 27?years of control simulation. In order to prove the hypothesis, another two sets of experiment are performed using two different boundary conditions (El Ni?o year and non-ENSO year). In each of these experiments, a single year of boundary conditions are used repeatedly year after year to generate ??internal?? interannual monsoon variability. Simulation of monsoon climate in the control model run is found to be in reasonably good agreement with observation. However, large rainfall bias is seen over Arabian Sea and Bay of Bengal. The interannual monsoon rainfall variability are of the same order in two experiments, which suggest that the external influences may not be important on the generation of ??internal?? monsoon rainfall variability. It is shown that, a dry (wet) pre-onset land-surface condition increases (decreases) rainfall in June which in turn leads to an anomalous increase (decrease) in seasonal (JJAS) rainfall. The phase and amplitude of CISO are modulated during May?CJune and beyond that the modulation of CISO is quite negligible. Though the pre-onset rainfall is unpredictable, significant modulation of the post-onset monsoon rainfall by it can be exploited to improve predictive skill within the monsoon season.  相似文献   

5.
Rainfall patterns influence water usage and revenue from user payments in rural Africa. We explore these dynamics by examining monthly rainfall against 4,888 records of rural piped water revenue in Ghana, Rwanda, and Uganda and quantifying revenue changes over 635 transitions between dry and wet seasons.Results show operators experience revenue variability at regional and intra-seasonal scales. Revenues fall by an average of 30 percent during the wettest months of the year in climate regimes with consistent wet season rainfall. However, seasonally stable revenues are observed in areas where consecutive dry days are common during the wet season, potentially reflecting a dependency on reliable services. We also find changes in tariff level, waterpoint connection type, and payment approach do not consistently prevent or increase seasonal revenue variability.Local revenue generation underpins delivery of drinking water services. Where rainfall patterns remain consistent, piped water operators can expect to encounter seasonal revenue reductions regardless of whether services are provided on or off premises and of how services are paid for. Revenue projections that assume consistent volumetric demand year-round may lead to shortfalls that threaten sustainability and undermine the case for future investment. Intra-seasonal rainfall analysis can enhance rural piped water revenue planning by offering localised insight into demand dynamics and revealing where climate variability may increase dependency on reliable services.  相似文献   

6.
Summary Analysis of the fifteen years of European Centre for Medium Range Weather Forecasts (ECMWF) reanalysis suggests that the transition from dry to wet season in Southern Amazonia is initially driven by increases of surface latent heat flux. These fluxes rapidly reduce Convective Inhibition Energy (CINE) and increase Convective Available Potential Energy (CAPE), consequently providing favourable conditions for increased rainfall even before the large-scale circulation has changed. The increase of rainfall presumably initiates the reversal of the cross-equatorial flow, leading to large-scale net moisture convergence over Southern Amazonia. An analysis of early and late wet season onsets on an interannual scale shows that a longer dry season with lower rainfall reduces surface latent heat flux in the dry and earlier transition periods compared to that of a normal wet season onset. These conditions result in a higher CINE and a lower CAPE, causing a delay in the increase of local rainfall in the initiating phase of the transition and consequently in the wet season onset. Conversely, a wetter dry season leads to a higher surface latent heat flux and weaker CINE, providing a necessary condition for an earlier increase of local rainfall and an earlier wet season onset. Our results imply that if land use change in Amazonia reduces rainfall during dry and transition seasons, it could significantly delay the wet season onset and prolong the dry season.  相似文献   

7.
Summary The Southwestern Cape (SWC) region of South Africa is characterized by winter rainfall mainly via cold fronts and by substantial interannual variability. Evidence is presented that interannual variability in SWC winter rainfall is related to sea-surface temperature (SST) and sea-ice anomalies in the central South Atlantic and adjoining Southern Ocean and to large scale ocean–atmosphere interaction in this region. During wet winters, the jet is strengthened just upstream of the SWC and significant cyclonic anomalies extend from the SW Atlantic over the region. SST tends to be anomalously warm (cool) in the SW Atlantic and SE Atlantic (central South Atlantic) and sea-ice extent increased in the central South Atlantic sector of the Southern Ocean. These patterns favor increased cyclogenesis upstream, a more northward track of midlatitude depressions, local intensification near the SWC and enhanced rainfall. Roughly the reverse patterns occur during dry winters. Some preliminary results from atmospheric GCM experiments are presented which help support these findings. Received November 9, 2001 Revised December 28, 2001  相似文献   

8.
Recent studies of trends in Midwestern precipitation show marked increases over the last 50 years of the 20th Century, and most climate models project that future rainfall in the Corn Belt will be increased further. During five years, 1988–1991 and 1994, field tests were conducted on agricultural test plots in central Illinois, an area typical of the Corn Belt, to discern how corn yields reacted to varying levels of added rainfall (+10%, +25%, and +40%) during the growing season. The best treatment over the five years was a 40% rain increase, with an average yield increase of 9%. Its yield increase was up to 34% in a hot-dry year, but below that of natural rainfall in a wet year as were the yields of the other lesser increases. The average yield changes from the three treatments were not statistically significantly different. Major interannual yield differences were found in the yields for each rain treatment, reflecting how rain timing and temperatures also have major effects on yields. A 40% summer rain increase has little influence if natural rains do not occur in the high stress period of mid summer. The plots results show that only small average increases in corn yields occur from growing season rain additions in the 10% to 40% range, except in dry years. Weather-crop yield regression models incorporating the same rain increases predict greater yield increases than found in these field tests. This suggests that future yields projected for a wetter climate using yield-weather models may be over-estimated. The plot sample size is small but conditions sampled in the five years represented 43% of all past 97 growing seasons in central Illinois and extremely good and bad weather years, which resulted in large between-year yield differences. Hence, the experimental results provide useful information about how increased rainfall may affect future corn yields, especially since the sample included three of the five types of dry growing seasons found in the area's climate since 1900.  相似文献   

9.
Janicot and Sultan (Geophys Res Lett 28(3):523–526, 2001) and Sultan et al. (J Clim 16(21):3389–3406, 2003) showed evidence of an intraseasonal signal of Sahelian rainfall corresponding to wet and dry sequences of the West African Monsoon. Using NCEP/NCAR reanalysis, NOAA outgoing longwave radiation (OLR) and observed daily rainfall over West Africa from 1968 to 1990, this paper investigates the variability of 3 to 5-day African Easterly Waves (AEWs), convection and their relationship with rainfall in these wet and dry sequences. The mean daily value rainfall during wet sequences is twice the mean value during dry sequences but the number of dry or wet sequences per year is not correlated with the annual rainfall. Wet sequences account for 39% of the annual accumulated rainfall while dry sequences account for 22%. The number of 3 to 5-day AEWs increases during wet years in wet sequences and the activity tends to be larger during wet years in both wet and dry sequences. These AEWs explain 40% of the accumulated rainfall during wet sequences whereas they contribute to 26% of the accumulated rainfall observed during dry sequences. Generally, they contribute to the increase of rainfall during these sequences. Mean convection is stronger and there are twice as many low OLR days (<225W/m2) during wet than dry sequences. The mean rainfall for days with high convective activity (convective days) is also twice as great during wet sequences. Rainfall that occurs during days without low OLR (weak convection with warm cloud tops or isolated deep convection) contributes to 69% of the total rainfall during dry sequences and 45% during wet sequences. A composite study was performed from day D 0−10 to day D 0+10 in each sequence. Wet (dry) sequences of the African monsoon start with a decrease (slight increase) of the negative meridional Ertel Potential Vorticity (PV) gradient at 700 hPa, associated with an increase (decrease) of the spectral density of AEWs. During the wet sequence, the African Easterly Jet (AEJ), detected by 700 hPa zonal wind, decreases and moves northward, whereas the Tropical Easterly Jet (TEJ), detected at 200 hPa, increases and shifts southward. Convective activity increases from D 0−6 to D 0−3 and remains high for 4 days in wet sequences. The daily rainfall increases (decreases) between D 0−6 and D 0 and returns to the mean value at D 0+4 for wet (dry) sequences.  相似文献   

10.
Summary Annual and interannual variations of rainfall over Brazil are discussed. First, rainy and dry seasons for several stations of Brazil are determined using the data of 21 years (1958–1978). The progressive movement of the Intertropical Convergence Zone seems to be associated with the progresive variation of rainfall seasons in the equatorial eastern Brazil. The annual migration of deep tropical convection from Central and Southern Portion of the Amazon basin in austral summer to the northwestern sector of South America in austral winter seems to be responsible for the annual cycle of rainfall in the Amazon basin. The conncection between the interannual variation of rainfall over Brazil and the Southern Oscillation is also discussed. The correlation coefficient between the Southern Oscillation index and the rainfall is generally small over most of Brazil except over Rio Grande do Sul. The correlation between the spring rainfall of Rio Grande do Sul and the Southern Oscillation index of the same or of the previous season is significantly high and shows prospects for seasonal rainfall prediction.With 5 Figures  相似文献   

11.
Summary The interannual variability of the monthly mean upper layer thickness for the central Arabian Sea (5°N-15° N and 60° E-70° E) from a numerical model of the Indian Ocean during the period 1954–1976 is investigated in relation to Indian monsoon rainfall variability. The variability in the surface structure of the Somali Current in the western Arabian Sea is also briefly discussed. It is found that these fields show a great deal of interannual variability that is correlated with variability in Indian monsoon rainfall. Model upper layer thickness (H) is taken as a surrogate variable for thermocline depth, which is assumed to be correlated with sea surface temperature. In general, during the period 1967 to 1974, which is a period of lower than normal monsoon rainfall, the upper ocean warm water sphere is thicker (deeper thermocline which implies warmer surface water); in contrast, during the period 1954–1966, which is a period of higher than normal monsoon rainfall, the upper warm water sphere is thinner (shallower thermocline which implies cooler surface water). The filtered time series of uppper layer thickness indieates the presence of a quasi-biennial oscillation (QBO) during the wet monsoon period, but this QBO signal is conspicuously absent during the dry monsoon period.Since model H primarily responds to wind stress curl, the interannual variability of the stress curl is investigated by means of an empirical orthogonal function (EOF) analysis. The first three EOF modes represent more than 72% of the curl variance. The spatial patterns for these modes exhibit many elements of central Arabian Sea climatology. Features observed include the annual variation in the intensity of the summer monsoon ridge in the Arabian Sea and the annual zonal oscillation of the ridge during pre- and post-monsoon seasons. The time coefficients for the first EOF amplitude indicate the presence of a QBO during the wet monsoon period only, as seen in the ocean upper layer thickness.The variability in the model upper layer thickness is a passive response to variability in the wind field, or more specifically to variability in the Findlater Jet. When the winds are stronger, they drive stronger currents in the ocean and have stronger curl fields associated with them, driving stronger Ekman pumping. They transport more moisture from the southern hemisphere toward the Indian subcontinent, and they also drive a greater evaporative heat flux beneath the Findlater Jet in the Arabian Sea. It has been suggested that variability in the heat content of the Arabian Sea drives variability in Indian monsoon rainfall. The results of this study suggest that the opposite is true, that the northern Arabian Sea responds passively to variability in the monsoon system.With 10 Figures  相似文献   

12.
Climate change has affected the temperature and rainfall characteristics worldwide. However, the changes are not equal for all regions and have localized intensity and must be quantified locally to manage the natural resources. Orissa is an eastern state in India where agricultural activities mainly depends on the rainfall and thus face problems due to changing patterns of rainfall due to changing climate. In the present study, attempts were made to study temporal variation in monthly, seasonal and annual rainfall over the state during the period from 1871 to 2006. Long term changes in rainfall characteristics were determined by both parametric and non-parametric tests. The analysis revealed a long term insignificant decline trend of annual as well as monsoon rainfall, where as increasing trend in post-monsoon season over the state of Orissa. Rainfall during winter and summer seasons showed an increasing trend. Statistically monsoon rainfall can be considered as very dependable as the coefficient of variation is 14.2%. However, there is decreasing monthly rainfall trend in June, July and September, where as increasing trend in August. This trend is more predominant in last 10?year. Based on departure from mean, rainfall analysis also showed an increased number of dry years compared to wet years after 1950. This changing rainfall trend during monsoon months is major concern for the rain-fed agriculture. More over, this will affect hydro power generation and reservoir operation in the region.  相似文献   

13.
Annual precipitation for the last 2,500 years was reconstructed for northeastern Qinghai from living and archaeological juniper trees. A dominant feature of the precipitation of this area is a high degree of variability in mean rainfall at annual, decadal, and centennial scales, with many wet and dry periods that are corroborated by other paleoclimatic indicators. Reconstructed values of annual precipitation vary mostly from 100 to 300 mm and thus are no different from the modern instrumental record in Dulan. However, relatively dry years with below-average precipitation occurred more frequently in the past than in the present. Periods of relatively dry years occurred during 74–25 BC, AD 51–375, 426–500, 526–575, 626–700, 1100–1225, 1251–1325, 1451–1525, 1651–1750 and 1801–1825. Periods with a relatively wet climate occurred during AD 376–425, 576–625, 951–1050, 1351–1375, 1551–1600 and the present. This variability is probably related to latitudinal positions of winter frontal storms. Another key feature of precipitation in this area is an apparently direct relationship between interannual variability in rainfall with temperature, whereby increased warming in the future might lead to increased flooding and droughts. Such increased climatic variability might then impact human societies of the area, much as the climate has done for the past 2,500 years.  相似文献   

14.
A new methodology is proposed that allows patterns of interannual covariability, or teleconnections, between the intraseasonal and slow components of seasonal mean Australian rainfall and the corresponding components in the Southern Hemisphere atmospheric circulation to be estimated. In all seasons, the dominant rainfall–circulation teleconnections in the intraseasonal component are shown to have the characteristic features associated with well-known intraseasonal dynamical and statistical atmospheric modes and their relationship with rainfall. Thus, for example, there are patterns of interannual covariability that reflect rainfall relationships with the intraseasonal Southern Annular Mode, the Madden-Julian Oscillation and wavenumber 3 and 4 intraseasonal modes of variability. The predictive characteristics of the atmospheric circulation–rainfall relationship are shown to reside with the slow components. In all seasons, we find rainfall–circulation teleconnections in the slow components related to the El Niño-Southern Oscillation. Each season also has a coupled mode, with a statistically significant trend in the time series of the atmospheric component that appears to be related to recent observed trends in rainfall. The slow Southern Annular Mode also features in association with southern Australian rainfall, especially during austral winter and spring. There is also evidence of an influence of Indian Ocean sea surface temperature variability on rainfall in southeast Australia during austral winter and spring.  相似文献   

15.
Bolivia is located at the crossroad of the major climatic influences of Northern and Southern-South America, which turns this country into a natural laboratory to investigate the interactions between ocean-climate and fire variability. We chose two oceanic indices: MEI (multivariate ENSO Index) and AMO (Atlantic Multidecadal Oscillation) to select the three most representative years for four oceanic conditions: El Niño, La Niña, AMO, and standard years (understood as years with little ocean influences), for the period 1992–2012. We investigated how i) rainfall (dry vs wet seasons) and ii) fire responded in five Bolivian biomes (Tropical Moist Forests, Tropical Dry Forests, Tropical Grasslands, Tropical Montane, and Seasonally Flooded ecosystems) under these oceanic conditions. Bolivia showed a strong rainfall increase in El Niño years in both seasons (wet/dry), while AMO showed the strongest droughts in both seasons. La Niña showed a bipolar response with rainfall increases in the wet season and a very marked rainfall decrease in the dry season. Drought significantly increased fire numbers in AMO years, being the most significant fire condition and suggesting a larger fire influence of the Atlantic than the Pacific at the national level. Surprisingly, the amount of fire was very large under normal years (STD) and similar to fire levels under La Niña, suggesting generalized fire conditions in the country, except for El Niño years that bring rainfall excess and little fire. The most fire-affected biomes were the seasonally flooded and dry forests, followed by the grassland/savannah biome. Montane areas showed the least fire, but satellite fire omission is well known in the Andean region.  相似文献   

16.
In this paper, temperature and rainfall data series were analysed from 34 meteorological stations distributed throughout Bangladesh over a 40-year period (1971 to 2010) in order to evaluate the magnitude of these changes statistically and spatially. Linear regression, coefficient of variation, inverse distance weighted interpolation techniques and geographical information systems were performed to analyse the trends, variability and spatial patterns of temperature and rainfall. Autoregressive integrated moving average time series model was used to simulate the temperature and rainfall data. The results confirm a particularly strong and recent climate change in Bangladesh with a 0.20 °C per decade upward trend of mean temperature. The highest upward trend in minimum temperature (range of 0.80–2.4 °C) was observed in the northern, northwestern, northeastern, central and central southern parts while greatest warming in the maximum temperature (range of 1.20–2.48 °C) was found in the southern, southeastern and northeastern parts during 1971–2010. An upward trend of annual rainfall (+7.13 mm per year) and downward pre-monsoon (?0.75 mm per year) and post-monsoon rainfall (?0.55 mm per year) trends were observed during this period. Rainfall was erratic in pre-monsoon season and even more so during the post-monsoon season (variability of 44.84 and 85.25 % per year, respectively). The mean forecasted temperature exhibited an increase of 0.018 °C per year in 2011–2020, and if this trend continues, this would lead to approximately 1.0 °C warmer temperatures in Bangladesh by 2020, compared to that of 1971. A greater rise is projected for the mean minimum (0.20 °C) than the mean maximum (0.16 °C) temperature. Annual rainfall is projected to decline 153 mm from 2011 to 2020, and a drying condition will persist in the northwestern, western and southwestern parts of the country during the pre- and post-monsoonal seasons.  相似文献   

17.
Thirty years of daily rainfall data are analysed for the South Coast region of South Africa, a region which experiences substantial rainfall variability and frequent severe drought and flood events, but whose climate variability has not been much researched. It is found that El Niño–Southern Oscillation (ENSO) exerts an influence since most wet years correspond to mature phase La Niña years. ENSO also influences South Coast rainfall via increases in the number of cut-off lows in southern South Africa during mature phase La Niña years. A statistically significant correlation between the Niño 3.4 index and monthly rainfall totals, and between this index and the frequency of wet days, exists for two summer months and also for June. There are also changes in the heavy rainfall day frequencies from one decade to another. Examination of NCEP re-analyses indicates that wet (dry) years result from an equatorward (poleward) shift in the subtropical jet, cyclonic (anticyclonic) pressure anomalies over the South Atlantic and South Africa, and increased (decreased) density of mid-latitude cyclonic systems.  相似文献   

18.
A 1053-year reconstruction of spring rainfall (March-June) was developed for the southeastern United States, based on three tree-ring reconstructions of statewide rainfall from North Carolina, South Carolina, and Georgia. This regional reconstruction is highly correlated with the instrumental record of spring rainfall (r = +0.80; 1887–1982), and accurately reproduces the decade-scale departures in spring rainfall amount and variance witnessed over the Southeast during the past century. No large-magnitude centuries-long trends in spring rainfall amounts were reconstructed over the past 1053 years, but large changes in the interannual variability of spring rainfall were reconstructed during portions of the Medieval Warm Period (MWP), Little Ice Age (LIA), and the 20th century. Dry conditions persisted at the end of the 12th century, but appear to have been exceeded by a reconstructed drought in the mid-18th century. High interannual variability, including five extremely wet years were reconstructed for a 20-yr period during the late 16th and early 17th centuries, and may reflect amplified atmospheric circulation over eastern North America during what appears to have been one of the most widespread cold episodes of the Little Ice Age.  相似文献   

19.
本文利用日本气象研究所（MRI）参加第五次国际耦合模式比较计划（CMIP5）的大气环流模式在高、中、低三种分辨率下的AMIP试验结果,评估了其对华南春雨气候态和年际变率的模拟能力,比较了不同分辨率的模拟结果。结果表明,三种不同水平分辨率（120 km、60 km和20 km）的模式均能再现北半球春季位于中国东南部的降水中心。相较于120 km模式,20 km模式能够更为合理地模拟出华南春雨位于南岭—武夷山脉的降水中心。水汽收支分析表明,60 km、20 km模式高估了水汽辐合,使得华南春雨的降水强度被高估。在年际变率方面,在三种分辨率下,模式均能较好地再现观测中El Ni?o衰减年春季的西北太平洋反气旋以及华南春雨降水正异常。较之120 km模式,60 km、20 km模式模拟的降水正异常的空间分布和强度更接近观测,原因是后者模拟的El Ni?o衰减年春季华南地区的水平水汽平流异常更接近观测。本研究表明,发展高分辨率气候模式是提高华南春雨的气候态和年际变率模拟水平的有效途径之一。  相似文献   

20.
Mahlalela  P. T.  Blamey  R. C.  Hart  N. C. G.  Reason  C. J. C. 《Climate Dynamics》2020,55(9-10):2743-2759

Much of the Eastern Cape province in South Africa has been experiencing a severe drought since 2015. This drought has had major socio-economic effects particularly on the large impoverished rural population as well as on some urban areas where supplied water services have broken down in several cases. The region is influenced by both midlatitude and tropical systems leading to a complex regional meteorology that hitherto has not been much studied compared to other parts of South Africa. Here, the ongoing drought is examined in the context of long-term trends and the interannual rainfall variability of the region. Although the region has experienced drought in all seasons since 2015, focus here is placed on the spring (September–November) which shows the most consistent and robust signal. On average, this season contributes between about 25–35% of the annual rainfall total. Based on CHIRPS data, it is found that this season shows a significant decreasing trend in both rainfall totals as well as the number of rainfall days (but not heavy rainfall days) for spring over most of the province since 1981. On interannual time scales, the results indicate that dry (wet) springs over the Eastern Cape are associated with a cyclonic (anticyclonic) anomaly southeast of South Africa as part of a shift in the zonal wavenumber 3 pattern in the midlatitudes. Over the landmass, a stronger (weaker) Botswana High is also apparent with increased (decreased) subsidence over and near the Eastern Cape which is less (more) favourable for cloud band development and hence reduced (enhanced) rainfall during dry (wet) springs. Analysis of mid-century (2040–2060) CMIP5 rainfall projections suggests that there may be a flattening of the annual cycle over the Eastern Cape with the winter becoming wetter and the summer drier. For the spring season of interest here, the multi-model projections also indicate drying but less pronounced than that projected for the summer.

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