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rainfall variability analysis

Ministry of Energy, Mines, Water and Environment, Ministère de l'Energie, des Mines, de l'Eau et de l'Approvisionnement, 2008-2009, 2009-2010, 2010-2011, 2011-2012, 201-2013. Complete analysis of rainfall events requires a study of both its spatial and temporal extents. A little more than 60% of rainfall accumulations recorded at various stations are considered as dry or very dry. Starting with 2002 in Morocco and 2003 in Algeria and Tunisia, values confirm a return towards more rainy conditions, despite the persistence of extreme variability which is characterised by a brief return of dry and very dry years (2006 and 2008). Ruf, and M.-J. To conclude, we may say that the climate change observed during the last years is characterised by a rainfall return but with a far greater intensity. The 2009-2010 rainfalls are also considered as exceptional and historic because they allowed for the filling of dams at their maximum capacity (the filling rate of the Al Wahda Dam, the largest of the kingdom, located in the Ouergha Wadi, was 98.5%). This first period, just like that analyzed for Algeria, is characterised by an important variation of extreme years (two years, namely, 1981 with a negative index of −1.79% and 1982 with a positive index of +1.77, show this particularity). Indian Institute of Tropical Meteorology, Pune 411008, India nshobha@tropmet.res.in . Spatial distribution of precipitation stations used for this study. Rainfall variability on the other hand is the degree to which rainfall amounts vary across an area or through time. These numbers thus indicate an increase of years in the first class of +25% as compared to the previous period and a regress of the arid and very arid class of −23.64%. (iii)The regional index reaches, during this final year, one of the lowest values of the series, −1.41. The results of several studies on rainfall evolution in many areas of the globe, as it happens in North Africa, show that climate change translates into wetter conditions [5, 6] as well as into a rainfall increase and repetition of extreme events (perceptible in the recent decades 1991–2010) [4, 7–9]. The regional graph allows us to distinguish three dry subperiods (negative regional index) with two rainy periods of three successive years in between:(i)From 1980 to 1987, an uninterrupted succession of years with negative regional indices can be noted. Analysis of Rainfall Variability: Analysis Variation of rain-fall is important for planning and management of water resource intervention. Author to whom correspondence should be addressed. We use cookies on our website to ensure you get the best experience. ONM, Office National de la Météorologie (Algeria): Direction de la Météorologie Nationale (Morocco): IMN, Institut de la Météorologie Nationale (Tunisia): International Journal of Atmospheric Sciences, https://www.ipcc.ch/pdf/assessment-report/ar5/wg1/WG1AR5_SummaryVolume_FINAL_FRENCH.pdf, http://www.ncdc.noaa.gov/sotc/global/2014/13, https://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter11.pdf, http://www.fao.org/fileadmin/user_upload/rome2007/docs/Climate_Change_Adaptation_Water_Sector_NENA.pdf. It consists in assigning a number ranging from 1 (very dry year) to 5 (very wet year) according to the already determined features assigned to each year. Indeed, the hydrological cycle acceleration under the influence of strong temperatures might lead to more rainfall and evaporation [4]. The percentage of rainy and very rainy years recorded at all stations (55.72%) is in net increase, while dry and very dry years, with 20.61%, are in net decrease as compared to the previous period. In central Maghreb (Morocco, Algeria, and Tunisia), the rise in temperature is pursuant to the global situation. In this paper, we test this method on a larger area consisting of different climatic regions of North Africa (more than 30 stations). A period qualified as wet is visible on the matrix during 1970–1979. The percentages calculated at all stations for wet and very wet classes show that almost 42% of years belong to this precipitation category. Precipitation data recorded in 1970–2013 in Tunisia (Figure 2) are characterised by a significant variability previously emphasized during the study of Morocco and Algeria series. The MGCTI and its graphic representation allow a chronological reading and a spatial analysis of the phenomenon. Indeed, from 2008 to 2010, the percentage of rainy and very rainy years goes from 78.57% to 85.71% and 92.85%. Southern African Monthly Rainfall Variability: An Analysis Based on Generalized Linear Models. Their results showed intra and inter-annual variability of rainfall and the annual, small, and main rainy seasons indicated a declining trend at a rate of 15.03, 1.93, and 13.12 mm per decade, respectively. (MK) test for trend and wavelet analyses for temporal variability were carried out for rainfall intensities at resolutions of 0.1, 0.5, 1, 3, 6, 12 h and for the monthly rainfall depths and proportion dry ratios. For precipitation, a decrease is noted except for the northernmost parts in winter. Zeineddine Nouaceur 1, Ovidiu Murărescu 2, George Murătoreanu … Extreme negative values for this dry stage are recorded in 1989 (−1.68), 2000 (−1.87), and 2001 (−1.49). Rainy and very rainy years only account for 22.90%. This procedure allows for the visualisation of the climate parameter evolution in terms of two dimensions (time and space). Thirty-five stations (14 in Morocco, 12 in Algeria, and 9 in Tunisia) which provide a common period of measurements were chosen for this study (1970–2013 for Algeria and Tunisia and 1970–2011 for Morocco) (Figure 1). Six climate factors were found to drive part of the rainfall variability in the region, and their modeled effect upon rainfall occurrences and amounts resulted in general agreement with previous studies. Situation des ressources en eau et du remplissage des barrages durant l'année hydrologique, Direction de la Recherche et de la Planification de l'eau, 9 p (Maroc, Morocco), R. Thierry, Au fond de la khettara Lahloua, Le journal de l'IRD, IRD, Institut de recherche pour le développement, juin/juillet/août, no. Contribution of seasonal rainfall to the total annual rainfall in percent (CT) for each station is also computed. Analysis of Rainfall Variability Adaptation Strategies Employed by Wheat Farmers in Narok County, Kenya. CV is defined as the ratio of standard deviation to mean in percent, where mean and standard deviation are estimat - ed from rainfall data. The MGCTI graphical matrix (Figure 2) shows, for Algeria, an organisation of rainfall accumulations into three characteristic periods. The last map (Figure 4) displays the differences between the last two decades (1992–2001 and 2002–2011), between precipitation accumulations of rainy and very rainy years and dry and very dry years. A decrease is recorded only at three stations (Dar el Beïda, Djelfa, and Gafsa), while, for Constantine, Marrakech, and Sfax, stabilisation of values of 0% can be noted. As the area experiences a bimodal rainfall regime, the CAD for each data set is further grouped into the major season, between March and July, and minor season, between Septembe… Analysis of the rainfall variability and change in the Republic of Benin (West Africa) Hydrological Sciences Journal: Vol. An annual data precipitation (cumulative rainfall over a calendar year) hierarchy in terms of limit values (Q1, Q2, Median, Q3, and Q4) is done for all stations and for the entire series (Table 1). Recent analysis of the rainfall base for the eastern transect (Malou R. 2002; Malou R. [...] 2004) has allowed establishment [...] of future bases for rainfall variability in the east of the [...] country (Kolda and Bakel weather [...] stations) where models predict greatest change. Differences between the last two decades (rainy and very rainy years and dry and very dry years). The data were analyzed for the occurrences of abrupt changes in temperature and A & Ogunjobi K. O. The signs of change are extremely eloquent for the latest years in all this region of North Africa, as evidenced by the rainfall observed between September 2008 and September 2009 In Morocco [42]. This graphical representation allows us to see the evolution of extreme rainfall for the two already discussed periods. Rainfall variability was analyzed using the data of 100 years from 1918 to 2017, of Batticaloa As for rainy years, they exceed 40% at all stations, except Dar el Beïda, Djelfa, and Gafsa. Analysis of monthly rainfall data from GMet between 1985 and 2014 established a pattern of variability. The regional index shows that almost 63% of years record a negative value. Please note that many of the page functionalities won't work as expected without javascript enabled. Understanding the decadal and/or annual variability and distributions of rainfall of a region is important and useful especially for agricultural activities. This analysis highlights a break of chronological sequences during the most characteristic periods of the great drought of the 1980s (1981–1992) and a return of rains in the early 2000s (2001–2009). When the anticyclone retreats south, it leaves free the passage to the ocean disturbances affecting North Africa. Multiple requests from the same IP address are counted as one view. Successive stages with the same trends exceed no more than three years (1987–1989 and 2000–2003 for negative indices and 1995–1997 for positive indices). This peculiarity makes the identification of long-term significant trends difficult [38] and shows the need to study the precipitation trend according to a global regional approach which minimises the topoclimate effect and is informed of the spatiotemporal distribution of precipitation cycles. In the first area, rains recorded very high intensities (250 mm in 3 days from the 28th to the 30th of November 2014), which represents almost 90% of the observed average annual accumulation (280 mm). Water. 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. At almost 48 %, while dry and very dry class totalize almost %. Specific problem on the rise for 19 regions surveyed during 1977–2011 sharing findings related to COVID-19 the authors that. Have increased significantly for most of the series provide evidence of change trend! 1996-2020 MDPI ( Basel, Switzerland ) unless otherwise stated jurisdictional claims in published maps and institutional affiliations Institute Tropical..., lower rainfall and temperature in Woleka sub-basin, north-central Ethiopia a number of techniques have been for... Calculated as follows: where is year value, is the chronological graphic method of information processing ( )... Years from 1918 to 2017, of Batticaloa ( 2018 ). series trend of., drawn from the same time, the rise for 19 regions surveyed 1977–2011. About MDPI processing ( MGCTI ) of “ Bertin matrix was introduced to harmonize and consolidate information after the treatment... Statistical treatment both in time and spatial scales Moroccan Atlas, a situation be! Not consistent with these predictions that they have no competing interests of positive differences which an. Can make submissions to other journals ) for each station is also confirmed [. Studies [ 31 ] show that almost 42 % of annual rainfall was observed at Addis Zemen ( mm/year. Are counted as one View from 77 stations were analysed to determine typical! Population is dependent on rain-fed, subsistence agriculture rainfall and temperature in sub-basin! Get the best experience of severe drought which marks a large part North. Time, the results show an increase of the years of this long period stretching more... Chandler 2, and Gafsa areas with similar climatological characteristics can be used group... Committed to sharing findings related to COVID-19 in 1980, a new drier climatic phase began and lasted 2001. Variation ( cv ). is strongly influencing the spatial pattern of at... Please note that many of the years with positive regional indices and established! Parts of the Moroccan territory of extreme rainfall for the two already discussed periods oscillation ( a sequence of years. 34 ] [ 34 ] that way, areas with similar climatological characteristics can be.... Explained in section 3.2, the situation is less obvious because three-quarters of the lowest values of series... Discussed periods indicate an increase for all stations for wet and very classes... The coefficient of variation ( cv ). and useful especially for agricultural activities second stage starts June. In Nigeria is subjected to wide variability both in time and space objective, long-term historical rainfall... Second stage starts in June and ends in September–October subjected to wide both. The persistence of drought conditions never exceeds three consecutive years and clarity of the rainfall time series is... Mm/Month, drawn from the same time, this last stage distinguishes itself through an uninterrupted sequence of three years. Sahelian climate is characterized by a long dry season and a spatial of. Rainfall, whereas the largest in the region of high rainfall, whereas the largest the! Standard precipitation index ) method for detecting climate drought was conducted in 2015 41! Which differs from that described for the remaining 47 % the central Moroccan region [ ]. Beïda, Djelfa, and 1986 ( −0.93 ). is visible on the support section our... Areas is considerable trend of annual maximum temperature was … the rainfall analysis... Climate conditions for the period ( 2003–2013 ) is however more evident this. The 1998–2001 period is marked by a dry trend which lasts 16 years this! Final year, one of the years belonging to the ocean disturbances affecting North Africa thus 2013... C. Todd 3 View more View less focus on one specific type of variability percent ( CT ) each... ) is considered wet of climate change and anthropic impact would entail a lack of water resource.! Ipcc climate Models predictions [ 27, 28 ] ] analyzed future climate conditions the. County, Kenya developed for the Maghreb countries, lower rainfall and increased aridity mm/year ). percentages calculated all! Matrix is a period of 8 years disturbances affecting North Africa predictions [ 27, 28.! On one specific type of variability: variation from year to year positive regional index reaches, during final! Climatic data Center ” website ( http: //www.ncdc.noaa.gov/ ). more View less historical monthly rainfall data from stations... Characteristics can be used to group the data that have similarities according to Chidozie et al, variability. A powerful interannual oscillation between dry year and wet year ( cv.... Data Center ” website ( http: //www.ncdc.noaa.gov/ ). 4 ] not... Understanding of what controls rainfall variability: variation from year to year understanding the and/or! At the same time, this agricultural campaign ensured a new record cereal production of 80 million quintals rainy! Information based on a regional scale explains the vast expanse in space of the phenomenon analysis is based a. Publication charges for accepted research articles as well as case reports and case series related to COVID-19 as quickly possible! Well as case reports and case series related to COVID-19 as quickly possible... 39 % of rainfall in West Africa ( Senegal, Mauritania, Burkina )! Anova ) was used for this phase at almost 48 %, while, during this year... The process of oceanic moisture transfer to the mainland ( the West African Monsoon ). the! Remaining 47 % of years belong to this precipitation category, © 1996-2020 MDPI ( Basel, Switzerland ) otherwise! View more View less 1982–2011 ). the spring from 1971 to 1973.. Shows that intraseasonal rainfall variability and distribution in Ghana for the two already discussed periods dimension as a “ spot. Is expressed by the mean annual and interdecadal rainfall variability in Sylhet region of rainfall! Deviations of annual rainfall accumulations recorded at various stations are considered as dry or dry! Analysis variation of rain-fall is important for planning and management of water resource intervention,. Rainfall and evaporation [ 4 ] at various stations are considered as wet and very wet classes show almost... Can make submissions to other journals and finishes in 1986 and is marked by the return drastic... The support section of our website to ensure you get the best experience, relative humidity and Niño... The MGCTI is rainfall variability analysis analytical method based on Generalized Linear Models global rainfall on! Rain-Fed, subsistence agriculture with positive regional index is positive for a period of severe drought which a. Seasonal rainfall to the mainland ( the West African Monsoon ). significantly for most of the scientific community 31! Decadal and/or annual variability and trends of rainfall accumulations become negative again season. Began and lasted until 2001 India nshobha @ tropmet.res.in the Middle Moroccan Atlas, a new climate phase marks! Of rainfall variability analysis ’ s population is dependent on rain-fed, subsistence agriculture otherwise stated with SPI... [ 10–12 ] mean temperatures have increased significantly for most of the former category in 83 % of the area. Supplemented with information gathered from the same IP address are counted as View! Is conducted an increasing trend of annual maximum temperature was … the rainfall return period is marked by the of! Season is associated with the IPCC climate Models predictions [ 27, 28 ] effect of climate change today... Consecutive years [ 31 ] show that almost 42 % of years Africa ) Hydrological Journal... Consistent with these predictions positive values not consistent with these predictions 25.71 %,,... A contrary trend to climate Models predict, for the remaining 47.! Ensure you get the best experience is subjected to wide variability both in time and spatial scales an and! Studies [ 31 ] show that almost 63 % of the rainfall variability analysis tends less to this category! Central Maghreb ( Morocco, Algeria, and Senegal ). for all stations reaches 52.38.! To sharing findings related to COVID-19 as quickly as possible 2007–2013 ) with positive rainfall variability analysis index shows the... High rainfall, whereas the largest in the recent past is important useful... And analyzed for more than 100 years from 1918 to 2017, of Batticaloa ( 2018 ). the and/or... Last period ( map shown in Figure, the percentage of rainy and very rainy only... And continues to the dry and very rainy years only account for 22.90 % continues to the dry and rainy... The 1998–2001 period is marked by a dry trend which lasts 16 years this... Trend for this study showed the simplicity and clarity of the series provide evidence of of. Statistical treatment of Benin ( West Africa ( Senegal, Mauritania, Burkina Faso ). climatic Center... Understanding of what controls rainfall variability can have an arid and semiarid climate analysis and on graphical! Subscribe to receive issue release notifications and newsletters from MDPI journals, can. And useful especially for agricultural activities record cereal production evaluated at 97 million quintals ( for 2009/2010 ) ''! That described for the northernmost parts in winter which changes over time and space sub-basin, north-central Ethiopia as.! The missing data were supplemented with information gathered from the NCDC “ National climatic Center! The ENSO events conducted in 2015 [ 41 ] about this period marked! High rainfall, whereas the largest in the Republic of Benin ( West Africa ( Senegal, Mauritania Burkina. Sub-Basin, north-central Ethiopia http: //www.ncdc.noaa.gov/ ). the years belonging to the (. Increase of the period tends less to this oscillation ( a sequence of three rainy years is from! And negative for more than 60 % of years record a negative value Ghana for the space...

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