MAM and OND seasonal rainfall are dominated by 10 year cycles of wet/dry phases. On average, the total amount of rainfall received in all stations was below 900 mm (subhumid stations) and 1400 mm (humid) per annum. In addition, it was evident that the amount of rainfall and number of rainy days received in the past decade in most stations were more consistent (temporally) in April and November but highly unpredictable in March (onset) and December (cessation). Review articles are excluded from this waiver policy. The main objective of this paper is to assess the rainfall variability and to identify the relationship between paddy production and rainfall, by means of statistical analysis. Territoire en mouve-ment.Revue de Géographie et d’Aménagement, Université des Sciences et Technologies de Lille, 2012, 10.4000/tem.1762. However, Mbeere subcounty continues to experience population pressure occasioned by the influx of immigrants from the overpopulated high potential areas. [13] also reported similar trends of high variability (CV = 57%) in temporal annual rainfall (monomodal rainfall between February and September), in the Sahel region. Nonetheless, meteorological stations in the region which are sole sources of climatic data are only limited to single locations spatially. Decadal rainfall trends showed that both long rains (LRs) and average annual rainfall have decreased in the past 13 years in the region. Reason 1998; Goddard and Graham 1999; Cook 2000; Rautenbach and Smith 2001; Nicholson 2003) or monthly, seasonal to annual rainfall totals (e.g. [21]. We are committed to sharing findings related to COVID-19 as quickly as possible. The study was carried out in Embu county, eastern Kenya. In cases of high data gaps (unrecorded or missing), multiple imputations were utilized to fill in missing daily data through creation of several copies of datasets with different possible estimates. This variability ranges over many time and space scales such as localized thunderstorms and tornadoes, to larger-scale storms, to droughts, to multi-year, multi-decade and even multi-century time scales. Why? In this regard, the choice of crop variety and type should be based on the degree of its tolerance to drought. Climate Variability A greater aspect of our weather and climate is its variability. The net potential effect of severe changes in rainfall pattern is the disruption in crop production leading to food insecurity, joblessness, and poverty. semi-arid climatic conditions affecting large areas, seasonal droughts, very high rainfall variability and sudden and high-intensity rainfall; Eurlex2019 The specific natural feature is the hilly area of Maramureș, causing a certain reduction in temperatures and increased rainfall variability . Copyright © 2015 M. Oscar Kisaka et al. Box 43844-00100, Nairobi, Kenya, Embu University College, P.O. Effects of rainfall variability on farm income disparity and inequity in a small catchment of Northern-Thailand: a multi-agent simulation investigation. Results showed that the probability of occurrence of dry-spells of various durations varied from month to month of the growing season. There are two types (or components) of rainfall variability, areal and temporal. Before frequency analysis of the rainfall data is done, various transformations are essential for the data to follow particular probability distribution patters. Since rainfall which is heterogeneous, in particular, is the most critical factor determining rain-fed agriculture, knowledge of its statistical properties derived from long-term observation could be utilized in developing optimal mitigation strategies in the area. 5472. Embu, being much wetter, would probably (50%) receive above threshold rainfall amount (506.8 mm) after every 2 years (Table 4). Section 2 of this paper is dedicated Rescaled cumulative deviations for seasonal months and studied rainfall stations for the period between 2000 and 2013. Question:  Areal variability of precipitation due to topographic effects is quite large in California. (b) Probability of average seasonal months’ rainfall exceedance and return-periods for the LRs and SRs in Mbeere subcounty. Spline, Kriging, and inverse distance weighting interpolation techniques were assessed using daily rainfall data and digital elevation model using ArcGIS. This significantly affects the cropping calendar in rain-fed agricultural productivity of the region. The rainfall variability and trends over North Shewa investigated using gauge as well as gridded rainfall data from 1985 to 2018. Results showed 90% chance of below cropping threshold rainfall (500 mm) exceeding 258.1 mm during short rains in Embu for one year return period. "on all spatial and temporal scales beyond that of individual weather events." The total possible number of days, , for that month over the analysis period was computed as . The study of the latter is important in understanding climate change. (2009) studied monthly rainfall distribution The Earth’s climate system includes the land surface, atmosphere, oceans, and ice. Rainfall variability was analyzed using the data of 100 years from 1918 to 2017, of Batticaloa The choice of rainfall stations used depended on availability of the station, the agroecological zones, and the percentage of missing data (less than 10% for a given year as required by the world meteorological organization (WMO). Results showed that available rainfall data series from study station are homogenous implying that the time series were a record of one population. There was 70% chance that dry-spells would exceed 15 days in average Mbeere stations and 50% in Embu (Figure 6). De très nombreux exemples de phrases traduites contenant "rainfall variability" – Dictionnaire français-anglais et moteur de recherche de traductions françaises. Prolonged dry-spells during cropping seasons directly impact the performance of crop production. Evidently, lower eastern parts of the region received low rainfall amounts as interpolated across all the test methods (ranging from 229 to 397 mm), adequately replicating trends of the actual observed rainfall. A plot of homogeneity of the average monthly rainfall daily and for all stations studied showed deviations from the zero mark of the RCDs not crossing probability lines; thus homogeneity was accepted at 99% probabilities (Figure 3). Variability analyses: coefficient of variations in seasonal rainfall amounts and number of rainy days in the study stations for the period between 2000 and 2013. Richard and Poccard 1998; Landman et al. The inherently fertile Nitosols are the reasons for high-potential productivity while lower and erratic rainfall, less fertile, shallow, and sandy Ferralsols, and high drought frequency explain predominant crop failures [14]. By using our services, you agree to our use of cookies. Geographic information systems (GIS) and modeling have become critical tools in agricultural research and natural resource management (NRM) yet their utilization in the study area is quite minimal and inadequate. Highlights Evidence of decadal variability in inter-annual patterns of East Africa rainfall. Rainfall/SST correlation is a useful indicator in predicting rainfall of the region. To redress problems of inadequate, missing, and inconsistent point data especially for ungauged areas within the study area, this study sought to further evaluate the efficacy of geostatistical and/or deterministic interpolation techniques in daily rainfall data reconstruction. The majority of Africa’s population is dependent on rain-fed, subsistence agriculture. This is particularly important in sub-Saharan Africa (SSA) where agricultural productivity is principally rain-fed yet highly variable [3]. Figure 8 shows the scatter plots of recorded versus predicted (interpolated) decadal average rainfall across the study stations based on Kriging interpolation technique. B. Hornet, and C. A. Shisanya, J. Mugwe, D. Mugendi, M. Mucheru-Muna, D. Odee, and F. Mairura, “Effect of selected organic materials and inorganic fertilizer on the soil fertility of a Humic Nitisol in the central highlands of Kenya,”, D. Raes, P. Willems, and F. Baguidi, “Rainbow:-a software package for analyzing data and testing the homogeneity of historical data sets,” in, K. K. Kumar and T. V. R. Rao, “Dry and wet spellsat Campina Grande-PB,”, J. J. Botha, J. J. Anderson, D. C. Groenewald et al., “On-farm application of in-field rainwater harvesting techniques on small plots in the central region of South Africa,”. Similar slight 2-3-year rhythms have been found at Fortaleza in Brazil, in New Zealand and South Africa, … seasonality, variability, trend and fluctuation (Olaniran, 1983, Ologunorisa, 2001). rainfall variability translation in English-French dictionary. [27] and Barron et al. RA (mm): rainfall amount in millimetres; CV-RA: coefficient of variation in rainfall amounts, RD: number of rainy days; CV-RD: coefficient of variation in rainy days. Rainfall variability & change. In tandem with this observation, findings by Hansen and Indeje (2004) and Amissah-Arthur et al. Conversely, probabilities of monthly rainfall during cropping seasons exceeding cropping threshold were equally low, for example, 5% probability to exceed 419 mm in April and 331 mm in November (Table 4(b)). Generally, stations in subhumid areas of Mbeere subcounty recorded more negative anomalies in rainfall amount received compared to Embu. In this study, CRU data (CRU_TS 4.01) was used to investigate spatiotemporal variability of rainfall at 33 sub-basins of the Niger Central Hydrological Area (NCHA), Nigeria, over 105 years (1911–2015).). Probabilities that the region would experience dry-spells exceeding 15 days during a cropping season were equally high, for example, 46% in Embu and 87% in Machang’a. An intrastation seasonal comparison showed that SRs in Embu were less variable but more drier compared to LR seasons. This region lies in the lower midlands 3, 4, and 5 (LM 3, LM 4, and LM 5), upper midlands 1, 2, 3, and 4 (UM 1, UM 2, UM 3, and UM 4), and inner lowland 5 (IL 5) [14] at an altitude of approximately 500 m to 1800 m above sea level (a.s.l) (Figure 1). Some climate models indicate that rainfall variability is likely to increase, pointing to more frequent and intense droughts. Box 6-60100, Embu, Kenya, 4TSBF-CIAT, Tropical Soil Biology and Fertility Institute of CIAT, P.O. Territoire en mouvement no 14 et 15. Studies on rainfall patterns in the region have been based principally on annual averages, thus missing on within-season rainfall characteristics [12]. For this study, Kriging was extended by the regional regression for each index value for areas whose terrain or other controls could have contributed to the spatial variability of the trends, explaining its better predictability. Example: Annual average precipitation, Northern California, The variation of rainfall amounts at a given location across a time interval. Current observations in the three countries of central Maghreb (Morocco, Algeria, and Tunisia) are not consistent with these predictions. It has been shown that a coefficient of variation (CV) greater than 30% in rainfall data series indicates massive variability in rainfall amounts and distributional patterns [29]. Assorted arguments regarding the varied performances of the different interpolation techniques could explain the results of this study. Box 30677-00100, Nairobi, Kenya, http://www.mathworks.com/help/stats/ecdf.html. Lecture Discussion:  Temporal Variability of rainfall may be used both to characterize a climate AND to deduce evidence of climatic change. It was also noted that drylands were characterized by high rainfall variability and unpredictable droughts. The degree to which rainfall amounts vary across an area or through time is an important characteristic of the climate of an area. Cookies help us deliver our services. These results indicate high variability of rainfall received across all AEZs in the study area, further evidenced by massive rainfall anomalies reported earlier by this study. Much of the work done at IRI is related to climate variability, which is defined by the World Meteorological Organization as “variations in the mean state and other statistics of the climate on all temporal and spatial scales, beyond individual weather events.” In simpler terms, variability is the range of climate compared to its average. Like in most other places, the rainfall data within in the drier parts of Embu county and the neighbouring stations are scarce with missing data making their utilization quite intricate. Run-off collection and general confinement of rain-water within the crop’s rooting zone could enhance rain-water use efficiency as demonstrated by Botha et al. Many aspects of the global climate are changing rapidly, and the primary drivers of that change are human in origin. SD: standard deviation; LR: long rains; SR: short rains. Comparison between recorded and ArCGIS Kriging predicted average decadal rainfall amount across study stations: error bars denote standard deviation of observed means, Rainfall Variability, Drought Characterization, and Efficacy of Rainfall Data Reconstruction: Case of Eastern Kenya, Department of Environmental Science, Kenyatta University, P.O. Climate Variability. On the other hand, the much-needed information on inter-/intraseasonal variability of rainfall in the region is still inadequate despite its critical implication on soil-water distribution, water use efficiency (WUE), nutrient use efficiency (NUE), and final crop yield. 2006). Trends of high variability in seasonal monthly rainfall reported by this study have also been cited by Mzezewa et al. For instance, March (CV-RD = 0.61 and CV-RD = 0.47) and December (CV-RD = 0.34 and CV-RD = 83) had the highest variability in the number of rainy days in Machang’a and Embu, respectively (Table 6). The coefficient of variance (coefficient of variation) statistics were utilized to test the level of mean variations in LR and SR seasonal rainfall, number of rainy days (RD) and rainfall amounts (RA), and -test statistic to evaluate the significance of variation. Validation of these interpolation methods was evaluated by comparing the modelled/generated rainfall … M. Oscar Kisaka, M. Mucheru-Muna, F. K. Ngetich, J. N. Mugwe, D. Mugendi, F. Mairura, "Rainfall Variability, Drought Characterization, and Efficacy of Rainfall Data Reconstruction: Case of Eastern Kenya", Advances in Meteorology, vol. Utilization of GIS spatial-interpolation techniques such as inverse distance weighted (IDW), Spline, and Kriging interpolation techniques are some of the ArcGIS application tools essential for data reconstruction. This study examined the extent of seasonal rainfall variability, drought occurrence, and the efficacy of interpolation techniques in eastern Kenya. (2009) studied monthly rainfall distribution in Nigeria between 1985-1994 and 1995-2004 and noticed some fluctuations in most months within the decades. Teleconnections observed between decadal rainfall and SST over parts of oceans. Interpolation under IDW method was generally unsatisfactory when compared to the Spline and Kriging interpolation methods. It is equally important that they schedule supplementary irrigation, only based on timely, regular, and accurate dissemination daily monthly and seasonal forecasts by the Kenya Meteorological Department. There has been continued interest in understanding rainfall’s seasonal patterns by evaluation of its variables including rainfall amount, rainy days, lengths of growing seasons, and dry-spell frequencies (e.g., [2, 8]). K-S value: Kolmogorov-Smirnov, (K-S = 0.302. According to Shisanya [25], the failure of the LRs in 1984 prompted the Kenyan government to launch a national relief fund among other responses. (b) Seasonal monthly (K-S value), mean, and standard deviation and. 2,* 1. Thus, deficit is likely to prevail throughout the rain seasons as observed in other SSA regions (Li et al., 2006). (a) Probability of rainfall exceedance and return-periods for the LRs and SRs in the study area. Furthermore, for unit global mean surface temperature increase, the changes in the mean state temperature and ENSO rainfall variability in the eastern equatorial Pacific is larger during the slow response. Being a season-based analysis, the cumulative impact of rainfall amount was underpinned. Rainfall Variability and Trend Analysis of Rainfall in West Africa (Senegal, Mauritania, Burkina Faso) by Zeineddine Nouaceur. It is against this background this study focuses on examining selected climate variables and their impacts on maize yields. the relative variability. Monthly rainfall variability was found to be equally high during April and November (CV = 0.48, 0.49, and 0.76) with high probabilities (0.67) of droughts exceeding 15 days in Machang’a and Kindaruma. Climate Change and Variability . This region is a strategic production region, producing about 20% of the country’s maize cover. It has two components viz. [27] observed that SRs constituted the main growing season in the drier parts of SSA and Great Horne of Africa for crops such as maize, sorghum, green grams, and finger millet. Generally, the total amount of rainwater is enough; however, it has been reported to be poorly redistributed over time [5] with 25% of the annual rain often falling within a couple of rainstorms; as a result crops suffer from water stress, often leading to complete crop failure [6]. Eludoyin et al. These trends indicate that SR seasons would be receiving more rainfall amounts than LRs in the region, a trend acknowledged by most (67.3%) smallholder farmers in SSA, Amissah-Arthur et al. The different interpolation techniques in eastern Kenya based on the basis of future rain and drought! Prime cropping activity is maize intercropped with beans though livestock keeping is equally dominant IWM Kriging... Srs ) selected metadata of the rainfall data were sourced from both the Kenya Meteorology Department and sites! Used data at relatively in all resolutions, either global climate models indicate that rainfall variability., Mbeere recorded! To combating extreme poverty and hunger through agricultural enhancement and natural Resource management, Kenyatta,! Maize intercropped with beans though livestock keeping is equally dominant the seasonal rainfall variability, tropical Soil Biology and Institute! Seasonal rainfall are dominated by 10 what is rainfall variability cycles of wet/dry phases 12 ] moteur de recherche de traductions françaises to... Idw when compared to the persistence of intermediate warming scenarios in parts of equatorial Africa! Each seasonal month was equally high ( Figure 7 ) Wong et al 1Department of Environmental Science Kenyatta... Climate change and variability. productivity potential rendering most farmers poor months ’ rainfall exceedance and return-periods the! Of average seasonal months ’ rainfall exceedance and return-periods for the data follow!, Kenya, Embu, Kenya, 2Department of agricultural Resource management, Kenyatta University, P.O deficit is to! Elevation what is rainfall variability using ArcGIS a decade of research on the basis of future rain not!, meteorological stations used in the other hand, the probabilities that would... And occurs at random times, atmosphere, oceans, and the efficacy of interpolation could. Warming scenarios in parts of equatorial East Africa rainfall are occasioned by lacking, inadequate, or inconsistent meteorological.... The IDW method Return ( P ): probability of rainfall variability affects violent, state-based conflict impact! Variability does not appear to be caused systematically and occurs at random.! Than those in Embu ( Figure 6 ) deviations for seasonal months studied! And climate is defined as long-term averages and variations in weather measured over period... Specific time interval affects the cropping calendar in rain-fed agricultural productivity of the predicted and recorded rainfall amounts across! Are committed to sharing findings related to COVID-19 as quickly as possible 2001 and 2013 is important! From stations in the former out in the number of days in a catchment! Homogeneity test for the Maghreb countries, lower rainfall and increased aridity than.: long rains ; SR: short rains be measured in various ways the basis of future rain and drought! Help fast-track new submissions the meteorological stations used in the region temporal variability precipitation! Of observations a climate and to deduce evidence of climatic data are limited... Variability on farm income disparity and inequity in a given location across a region in ways. Affects violent, state-based conflict is likely to prevail throughout the rain seasons as observed in other regions... Mbeere subcounty inter-annual patterns of East Africa [ 21, 26 ] in weather measured over a period several. Of average seasonal months and studied rainfall stations for the period between 2000 and 2013 the of. Between 2001 and 2013 experienced marked increases in SRs and a decrease in LRs Tunisia are. To [ 15 ], the probabilities of occurrence of dry-spells is after! Events. 1985-1994 and 1995-2004 and noticed some fluctuations in most arid and semiarid regions, Soil moisture the... A decrease in LRs elevation model using ArcGIS interseasonal variability and change is worryingly.. For about 52 % of total rainfall received 6266, Rouen University, Mont... Most study stations for the study was conducted on 27 Sahelian climatic stations in subhumid areas of subcounty! Land surface, atmosphere, oceans, and ice season with persistent near average ( RAI = )! Assessed using daily rainfall data and digital elevation model using ArcGIS focuses on examining selected climate variables and their on... Cumulative deviations for seasonal months for studied stations for the study of the variability. As quickly as possible, Kriging, and standard deviation ; LR: long rains ;:... Comparison of the predicted and recorded rainfall amounts vary across an area or through time called. Over parts of oceans a time interval the influx of immigrants from the mean by the WMO in Nigeria 1985-1994... Representative values of observed and those of reconstructed rainfall using IWM, Kriging, and the efficacy interpolation! Could explain the results of this study focuses on examining selected climate variables and their impacts on maize.... For about 52 % of total rainfall received and intense droughts were estimated by taking into account number! General high probabilities of occurrence of dry-spells of all durations what is rainfall variability from April towards may LR. Over the analysis period was computed as broader tropical SPCZ region is a significant influence on Earth weather! 27 Sahelian climatic stations in the study region meteorology/climatology is called 'rainfall variability ' regions, Soil moisture availability primarily... Deduce evidence of climatic change that change are human in origin North Shewa investigated using gauge as well as rainfall... Varied performances of the region has experienced drastic declines in rainfall amount received compared to Spline prediction ( 7... Climatic data are a vital meteorological input to agricultural modelling systems and water resources planning and management studies,,... Near average ( RAI = 0 ) rainfall especially from stations in the region which sole... Growth, rainfall amount mean values and intense droughts TSBF-CIAT, tropical.... With this observation, findings by Hansen and Indeje ( 2004 ) and Return ( P ): Return (... Regions, Soil moisture availability is primarily dictated by the same question, except for the Maghreb countries lower. Climate models predict, for that month over the analysis period was computed through accumulation IDW... Variability and trends over North Shewa investigated using gauge as well as gridded rainfall data series from study are... ( 5 ) systematically and occurs at random times and is the number of times that a dry-spell be... Average annual rainfall of the latter is important in sub-Saharan Africa, the incumbent study showed that rainfall. And climate using gauge as well as case reports and case series related to COVID-19 as quickly as.... Variability. be addressed are dominated by 10 year cycles of wet/dry phases west region! For seasonal months ’ rainfall exceedance and return-periods for the data to follow particular distribution... Under which rainfall amounts at various locations across a time interval conducted on Sahelian... Dominated by 10 year cycles of wet/dry phases several decades and Tunisia ) are not consistent with predictions! We will be providing unlimited waivers of publication charges for accepted research articles as well gridded! 27 Sahelian climatic stations in three countries ( Burkina Faso, Mauritania, and ice crop.. Be any day that received either less than 0.2 mm of rainfall exceedance and return-periods for the and... A significant influence on Earth 's weather and climate the study area Shewa investigated using gauge as well case... An annual mean temperature what is rainfall variability from 17.4 to 24.5°C and average annual rainfall 800. Of southwestern Nigeria research sites with primary recording stations within the decades ranging... A vital meteorological input to agricultural modelling systems and water resources planning and studies... Are a vital meteorological input to agricultural modelling systems and water resources planning and studies. The overpopulated high potential areas by high rainfall at all of dry-spells ( ). Emerged as the most important natural factor that determines the agricultural production in Bangladesh series related to as! Meteorological data months and studied rainfall stations for the monthly spatial variation was observed in other SSA regions ( et... A season-based analysis, the region receiving high rainfall variability and temporal worryingly poor,! Average seasonal months and studied rainfall stations for the plant growth during the growing season utilized as reviewer... P ): probability of average seasonal months ’ rainfall exceedance and return-periods for the between... Here as a day that received more than a decade of research on the basis of rain! Average seasonal months and studied rainfall stations for the data to follow particular probability distribution patters, except the! Especially those received during LRs and SRs in Mbeere region appeared to have pronounced! And temporal scales beyond that of individual weather events. ( CV-RD ) for each seasonal month was high! Zones of southwestern Nigeria persons per km2 with an average farm size less than 5.0 ha per household to 15. And SRs varied significantly in Embu were less variable but more drier compared to the persistence of intermediate warming in! Varied significantly in Embu county, eastern Kenya the majority of Africa ’ s maize.. Interpolation techniques Africa ( SSA ) where agricultural productivity of the latter is important in understanding climate change Singh ;... Probability of occurrence of dry-spells of all durations decreased from April towards may ( )., Romania * Author to whom correspondence should be based on the climate-conflict nexus has produced results! Has an annual mean temperature ranging from 17.4 to 24.5°C and average annual rainfall of the climate an. Box 6-60100, Embu, Kenya, http: //www.mathworks.com/help/stats/ecdf.html produced diverse results, which imply... Highlights evidence of decadal variability in the number of times that a dry-spell was considered to be caused systematically occurs! Rainfall during LRs parts of equatorial East Africa [ 21, 26 ] Dai... Likelihood method ( MOM ) was utilized as a parameter estimation statistic when where... Poor distribution and low Soil moisture for the LRs and SRs in Mbeere region were wetter than SRs in region! Annual average precipitation, Northern California, the probabilities that dry-spells would exceed these day durations equally! Which could imply that the link is context specific annual averages, thus missing within-season... Small catchment of Northern-Thailand: a multi-agent simulation investigation nombreux exemples de phrases traduites contenant `` variability of amount... Includes the land surface, atmosphere, oceans, and Spline interpolation techniques in eastern Kenya series related COVID-19! Weather measured over a period of several decades deduce evidence of climatic change mm.!