scholarly journals Identification of a Representative Stationary Period for Rainfall Variability Description in the Sudano-Sahelian Zone of West Africa during the 1901–2018 Period

Atmosphere ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 716
Author(s):  
Boubacar Ibrahim ◽  
Yahaya Nazoumou ◽  
Tazen Fowe ◽  
Moussa Sidibe ◽  
Boubacar Barry ◽  
...  
Keyword(s):  
West Africa ◽  
Rainfall Variability ◽  
Baseline Period ◽  
Rainfall Amount ◽  
Annual Rainfall ◽  
Rainfall Time Series ◽  
Variability Analysis ◽  
The Mean ◽  
The Difference ◽  
Stationary Period

Many studies have been undertaken on climate variability in West Africa since the drastic drought of 1970s. These studies rely in many cases on different baseline periods chosen with regard to the reference periods defined by the World Meteorological Organization. A method is developed in this study to determine a stationary baseline period for rainfall variability analysis. The method is based on an application of three statistic tests (on deviation and trend) and a test of shifts detection in rainfall time series. The application of this method on six different gridded rainfall data and observations from 1901 to 2018 shows that the 1917–1946 period is the longest stationary period. An assessment of the significance of the difference between the mean annual rainfall amount during this baseline period and the annual rainfall amount during the other years shows that the “Normal” annual rainfall amount is defined by an interval delineated by ±the standard deviation (STD). With regard to this interval, a very wet/dry year is defined with a surplus/gap over/below the STD. Overall the 1901–2018 period, the 1950–1970 period presents the most important number of significant wet years and the 1971–1990 period presents the most important number of significant dry years.

scholarly journals Bayesian Rainfall Variability Analysis in West Africa along Cross Sections in Space–Time Grid Boxes

2004 ◽  
Vol 17 (5) ◽  
pp. 1069-1082 ◽  
Author(s):  
Dominique Tapsoba ◽  
Mario Haché ◽  
Luc Perreault ◽  
Bernard Bobée
Keyword(s):  
West Africa ◽  
Cross Sections ◽  
Rainfall Variability ◽  
Space Time ◽  
Variability Analysis ◽  
Time Grid

scholarly journals Spatial and Temporal Rainfall Variability over the Mountainous Central Pindus (Greece)

Climate ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 75 ◽  
Author(s):  
Stefanos Stefanidis ◽  
Dimitrios Stathis
Keyword(s):  
Multiple Regression ◽  
Rainfall Variability ◽  
Multiple Regression Model ◽  
Rainfall Data ◽  
Annual Rainfall ◽  
Spatial And Temporal Variability ◽  
Mountain Range ◽  
Rainfall Time Series ◽  
Distribution Maps ◽  
Mountainous Catchment

In this study, the authors evaluated the spatial and temporal variability of rainfall over the central Pindus mountain range. To accomplish this, long-term (1961–2016) monthly rainfall data from nine rain gauges were collected and analyzed. Seasonal and annual rainfall data were subjected to Mann–Kendall tests to assess the possible upward or downward statistically significant trends and to change-point analyses to detect whether a change in the rainfall time series mean had taken place. Additionally, Sen’s slope method was used to estimate the trend magnitude, whereas multiple regression models were developed to determine the relationship between rainfall and geomorphological factors. The results showed decreasing trends in annual, winter, and spring rainfalls and increasing trends in autumn and summer rainfalls, both not statistically significant, for most stations. Rainfall non-stationarity started to occur in the middle of the 1960s for the annual, autumn, spring, and summer rainfalls and in the early 1970s for the winter rainfall in most of the stations. In addition, the average magnitude trend per decade is approximately −1.9%, −3.2%, +0.7%, +0.2%, and +2.4% for annual, winter, autumn, spring, and summer rainfalls, respectively. The multiple regression model can explain 62.2% of the spatial variability in annual rainfall, 58.9% of variability in winter, 75.9% of variability in autumn, 55.1% of variability in spring, and 32.2% of variability in summer. Moreover, rainfall spatial distribution maps were produced using the ordinary kriging method, through GIS software, representing the major rainfall range within the mountainous catchment of the study area.

scholarly journals Persistent decadal-scale rainfall variability in the tropical South Pacific Convergence Zone through the past six centuries

2014 ◽  
Vol 10 (4) ◽  
pp. 1319-1332 ◽  
Author(s):  
C. R. Maupin ◽  
J. W. Partin ◽  
C.-C. Shen ◽  
T. M. Quinn ◽  
K. Lin ◽  
...  
Keyword(s):  
Climate Variability ◽  
Decadal Variability ◽  
Solomon Islands ◽  
Rainfall Variability ◽  
South Pacific ◽  
Rainfall Amount ◽  
South Pacific Convergence Zone ◽  
Annual Rainfall ◽  
Convergence Zone ◽  
Decadal Scale

Abstract. Modern Pacific decadal variability (PDV) has global impacts; hence records of PDV from the pre-instrumental period are needed to better inform models that are used to project future climate variability. We focus here on reconstructing rainfall in the western tropical Pacific (Solomon Islands; ~ 9.5° S, ~160° E), a region directly influenced by PDV, using cave deposits (stalagmite). A relationship is developed between δ18O variations in the stalagmite and local rainfall amount to produce a 600 yr record of rainfall variability from the South Pacific Convergence Zone (SPCZ). We present evidence for large (~1.5 m), abrupt, and periodic changes in total annual rainfall amount on decadal to multidecadal timescales since 1423 ± 5 CE (Common Era) in the Solomon Islands. The timing of the decadal changes in rainfall inferred from the 20th century portion of the stalagmite δ18O record coincides with previously identified decadal shifts in PDV-related Pacific ocean–atmosphere behavior (Clement et al., 2011; Deser et al., 2004). The Solomons record of PDV is not associated with variations in external forcings, but rather results from internal climate variability. The 600 yr Solomon Islands stalagmite δ18O record indicates that decadal oscillations in rainfall are a persistent characteristic of SPCZ-related climate variability.

scholarly journals Study the rainfall variability and impact of El Nino episode on rainfall and crop productivity at Parbhani

MAUSAM ◽  
2021 ◽  
Vol 71 (2) ◽  
pp. 285-290
Author(s):  
DAKHORE K K ◽  
KADAM Y E ◽  
KUMAR P VIJAYA
Keyword(s):  
El Niño ◽  
Negative Impact ◽  
El Nino ◽  
Rainfall Variability ◽  
Crop Productivity ◽  
Negative Influence ◽  
Seasonal Rainfall ◽  
Annual Rainfall ◽  
Black Gram ◽  
The Mean

The weekly rainfall data for 36 years (1981-2016) recorded at Vasantrao Naik Marathwada  Krishi Vidyapeeth, Parbhani were analyzed for mean seasonal, weekly rainfall and also weekly rainfall probabilities. The mean seasonal rainfall was 796 mm, received in 38 rainy days. The seasonal rainfall indicated that there is 53% chance of receiving less than 700 mm with variable intensities and 36% chance of getting more than normal rainfall and 11% chance of seasonal rainfall, in between 700 mm to 800 mm. The mean weekly rainfall during crop season was 45.8 mm with a CV of 116%. Highest mean weekly rainfall was recorded 71.8 mm with SD (95.3) and CV (132.7%) in 30th MW. Sowing of Kharif crops should be undertaken during 24th MW to 27th MW. Significant and positive correlation between yield and rainfall was observed for Soybean, Pigeonpea, Black gram, Green gram and rice. The predictability of productivity of crops using seasonal rainfall is 10-20% variation in productivity for all the crops at the Centre. The El Nino episode was negatively influencing Southwest monsoon and annual rainfall as well as rainfall during the months of July and September. El Nino episodes exhibit more negative influence on productivity of all the crops except rice crop. Among the different categories of El Nino, weak events exerted more negative impact on productivity of short duration crops (i.e., sorghum, soybean and Black gram)  as compared to moderate and strong El Nino events.

scholarly journals Recent Trends in the Daily Rainfall Regime in Southern West Africa

Atmosphere ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 741 ◽  
Author(s):  
Francis Nkrumah ◽  
Théo Vischel ◽  
Geremy Panthou ◽  
Nana Ama Browne Klutse ◽  
David C. Adukpo ◽  
...  
Keyword(s):  
West Africa ◽  
Rainy Season ◽  
Daily Rainfall ◽  
Annual Rainfall ◽  
Large Set ◽  
Mean Intensity ◽  
Mean Annual Rainfall ◽  
Recent Trends ◽  
The Mean ◽  
Climate Events

Extreme climate events, either being linked to dry spells or extreme precipitation, are of major concern in Africa, a region in which the economy and population are highly vulnerable to climate hazards. However, recent trends in climate events are not often documented in this poorly surveyed continent. This study makes use of a large set of daily rain gauge data covering Southern West Africa (extending from 10° W to 10° E and from 4° N to 12° N) from 1950 to 2014. The evolution of the number and the intensity of daily rainfall events, especially the most extremes, were analyzed at the annual and seasonal scales. During the first rainy season (April–July), mean annual rainfall is observed to have a minor trend due to less frequent but more intense rainfall mainly along the coast of Southern West Africa (SWA) over the last two decades. The north–south seasonal changes exhibit an increase in mean annual rainfall over the last decade during the second rainy season (September–November) linked by both an increase in the frequency of occurrence of rainy days as well as an increase in the mean intensity and extreme events over the last decade. The study also provides evidence of a disparity that exists between the west and east of SWA, with the east recording a stronger increase in the mean intensity of wet days and extreme rainfall during the second rainy season (September–November).

scholarly journals Spatial analysis of rainfall variability and rainfed rice crop using GIS Technique in West Bengal (India)

MAUSAM ◽  
2021 ◽  
Vol 68 (2) ◽  
pp. 287-298
Author(s):  
P. K. SINGH ◽  
L. S. RATHORE ◽  
D. V. BHASKAR RAO ◽  
K. K. SINGH ◽  
A. K. Baxla ◽  
...  
Keyword(s):  
West Bengal ◽  
Rainfall Variability ◽  
Crop Productivity ◽  
Rice Crop ◽  
Annual Rainfall ◽  
Mean Annual Precipitation ◽  
Growth Stages ◽  
Kharif Season ◽  
Dry Spells ◽  
The Mean

The rainfed areas receive mean annual precipitation in range of 500-1500 mm with high degree of variability and are beset with problems of mid-season drought and associated impacts on the crop productivity. In this paper, analysis of weekly, monthly, annual rainfall and weekly rainfall probabilities in relation to crop productivity has been carried out for all the stations of the study area in West Bengal where rain-fed agriculture is predominant.  However, duration of dry spells and its probabilities, climatic derivatives like commencement and cessation of rainy season, length of growing period (LGP) and estimates of water balance parameters have been carried out, in respect of all blocks in the identified three districts in West Bengal. The mean productivity during kharif season indicated that, highest productivity values of 3 to 3.5 t/ha are noticed in the block of central districts of Burdwan, Bankura, Birbhum, Hoogly districts.  Perhaps, irrigation facilities in these districts might have helped in arriving at such high productivity rates.  Low productivity of 1 to 1.5 t/ha have been noticed in two to three blocks of South 24-Paraganas and in Jalpaiguri districts. The productivity levels of northern districts, viz., Jalpaiguri, Coochbehar, West Dinajpur, South 24-Paranagas vary from 1.5 to 2.0 t/ha. The lowest productivity of 11.28 q /ha in Jaldha and 14.89 q /ha in Manbazar in 1996 can be due to heavy rainfall conditions in June and again in August. The mean productivity pattern of rice crop during kharif season in identified districts was analyzed with respect to occurrence of number of dry spells at different growth stages and average MAI values. The productivity was also related to monthly rainfall (July) and correlations have been mentioned for Jaldha block (0.22) and Manbazar block (0.64). The highest productivity of 2-3 t/ha are recorded in hot sub-humid to humid regions of West Bengal where LGP vary from 150 to 200 days. From the study of the probability of dry and wet spells and MAI during different crop phenophases, the most vulnerable phases can be identified in each region.  

scholarly journals Recent Rainfall Variability Over a Dryland Ecosystem of North Western India

2021 ◽  
Author(s):  
DIVYA SAINI ◽  
PANKAJ BHARDWAJ ◽  
Omvir Singh
Keyword(s):  
Rainfall Variability ◽  
Climatic Conditions ◽  
Annual Rainfall ◽  
Western India ◽  
Positive Trend ◽  
North West ◽  
North East ◽  
Mean Annual Rainfall ◽  
The Mean ◽  
North Western

Abstract In this study, an attempt has been made to examine the recent rainfall variability by means of daily rainfall data of 33 well spread stations over dryland ecosystem of Rajasthan in north western India during 1961-2017. For trend analysis, Mann-Kendall, Sen’s slope estimator and simple linear regression test have been used (at 95% confidence level). The results have shown a high interannual variability in rainfall occurrence varying from 277 mm (in year 2002) to 839 mm (in year 1975) with mean of 583 mm over this dryland ecosystem. Most of the rainfall deficit years have occurred with El-Nino years. The mean annual rainfall has shown a marginal non-significant upward trend over the ecosystem. The station-wise mean annual rainfall has revealed a significant rising trend over Barmer, Churu, Ganganagar, Jaisalmer and Pratapgarh stations. Interestingly, three year running average has shown a cyclic pattern of rainfall over dryland ecosystem under the changing climatic conditions. The spatial pattern has exhibited that the mean annual rainfall decreases from east and south east (more than 850 mm) to west and north west (less than 400 mm), which is mainly associated with the presence of Aravalli Mountains spreading north east to south west in central Rajasthan. Remarkably, majority of stations positioned in western parts of dryland ecosystem have shown increasing rainfall trends, whereas some stations located in eastern parts have recorded a non-significant declining trend. The magnitude of significant rising trend has varied from 5.34 mm/year (Pratapgarh station) to 2.17 mm/year (Jaisalmer station). Also, the frequency of heavy rainfall events has shown a positive trend with significant increasing trends over Bharatpur, Jaisalmer and Pratapgarh stations, whereas Bundi station has shown significant decreasing trend.

scholarly journals Dryland vegetation functional response to altered rainfall amounts and variability derived from satellite time series data

2016 ◽  
Author(s):  
Gregor Ratzmann ◽  
Ute Gangkofner ◽  
Britta Tietjen ◽  
Rasmus Fensholt
Keyword(s):  
West Africa ◽  
Functional Response ◽  
Ecosystem Functioning ◽  
Vegetation Type ◽  
Rainfall Variability ◽  
Rainfall Amount ◽  
Annual Precipitation ◽  
Mean Annual Precipitation ◽  
South West ◽  
South West Africa

Abstract. Vegetation net productivity is a key variable in ecosystem functioning. Understanding how its functional response to rainfall in drylands is affected by altered rainfall amounts and variability is therefore vitally important to understand consequences of climatic change for those water-limited ecosystems. Here, we show how this functional response is affected by below and above 30-year-average rainfall conditions in two arid to semi arid subtropical regions in West and South West Africa differing markedly in interannual rainfall variability (higher in South West Africa, lower in West Africa). Shifting linear regression models (SLRs) were used with annual precipitation (satellite derived African Rainfall Climatology 2, ARC2) as explanatory variable and annual satellite-derived vegetation productivity proxies (normalized difference vegetation index, NDVI) as response variable to estimate the gridded vegetation functional response to rainfall. From the SLRs, time series of responses were derived and analyzed along gradients of mean annual precipitation. Vegetation responses to rainfall show a unimodal response along rainfall gradients. While responses for South West Africa are higher during dry periods for mean annual precipitation < 500 mm and spatially more variable, the responses to climate for West Africa are generally low and spatially less dynamic. Those patterns follow differences in interannual rainfall amount variability (higher in South West Africa). Regional peaks of vegetation response to rainfall along mean annual precipitation are found at precipitation values with similar interannual variability in growing season length. Vegetation type (MODIS MCD12C) specific response to rainfall mostly follows observed responses along rainfall gradients leading to region specific responses for each vegetation type. We conclude that higher rainfall amount variability enhances regional-scale vegetation response to rainfall plasticity and thus dryland ecosystem resilience to dry periods. Those results apply irrespective of vegetation type and thus evidence the fundamental role of rainfall variability in ecosystem functioning. Presented results moreover imply that the Sahel region (West Africa) although currently recovering from drought might be highly susceptible to future dry periods.

scholarly journals The Relationship between Climate Change, Variability, and Food Security: Understanding the Impacts and Building Resilient Food Systems in West Pokot County, Kenya

2022 ◽  
Vol 14 (2) ◽  
pp. 765
Author(s):  
Everlyne B. Obwocha ◽  
Joshua J. Ramisch ◽  
Lalisa Duguma ◽  
Levi Orero
Keyword(s):  
Climate Change ◽  
Land Use ◽  
Food Security ◽  
Land Cover ◽  
Rainfall Variability ◽  
Early Warning Systems ◽  
Annual Rainfall ◽  
Climate Change And Variability ◽  
West Pokot ◽  
The Mean

This study integrated local and scientific knowledge to assess the impacts of climate change and variability on food security in West Pokot County, Kenya from 1980–2012. It characterized rainfall and temperature from 1980–2011 and the phenology of agricultural vegetation, assessed land use and land cover (LULC) changes, and surveyed local knowledge and perceptions of the relationships between climate change and variability, land use decisions, and food (in)security. The 124 respondents were aware of long-term changes in their environment, with 68% strongly believing that climate has become more variable. The majority of the respondents (88%) reported declining rainfall and rising temperatures, with respondents in the lowland areas reporting shortened growing seasons that affected food production. Meteorological data for 1980–2011 confirmed high inter-annual rainfall variability around the mean value of 973.4 mm/yr but with no notable trend. Temperature data showed an increasing trend between 1980 and 2012 with lowlands and highlands showing changes of +1.25 °C and +1.29 °C, respectively. Land use and land cover changes between 1984 and 2010 showed cropland area increased by +4176% (+33,138 ha), while grassland and forest areas declined by –49% (–96,988 ha) and –38% (–65,010 ha), respectively. These area changes illustrate human-mediated responses to the rainfall variability, such as increased stocking after good rainfall years and crop area expansion. The mean Normalized Difference Vegetation Index (NDVI) values ranged from 0.36–0.54 within a year, peaking in May and September. For weather-related planning, respondents relied on radio (64%) and traditional forecasters (26%) as predominant information sources. Supporting continuous climate change monitoring, intensified early warning systems, and disseminating relevant information to farmers could help farmers adopt appropriate adaptation strategies.

scholarly journals Statistical Analysis of Rainfall Variability for Tehsils of Palghar District, Maharashtra State, India

2021 ◽  
Vol 9 (VII) ◽  
pp. 2602-2618
Author(s):  
Dr. Sumit M. Dhak
Keyword(s):  
Statistical Analysis ◽  
Monsoon Season ◽  
Rainfall Variability ◽  
Daily Rainfall ◽  
Annual Rainfall ◽  
Department Of Agriculture ◽  
Average Annual Rainfall ◽  
Detailed Statistical Analysis ◽  
Annual Total ◽  
The Mean

A detailed statistical analysis of monthly, seasonal and annual rainfall for Tehsils of Palghar district were carried out using 22 years (1998-2019) daily rainfall data taken from Department of Agriculture, Maharashtra State. The mean, standard deviation and coefficient of variation for monthly, seasonal and annual rainfall were computed for tehsils of Palghar districts. The month of July received maximum monthly mean rainfall for all years (1998 to 2019) in tehsils of Palghar district. The result showed that monthly mean rainfall in month of July was maximum at Jawhar (1147.1 mm) followed by Vikramgad (1071.9 mm), Talasari (1014.3 mm), Vasai (1009.9 mm), Wada (998.5 mm), Mokhada (949.6 mm), Palghar (948.7 mm) and Dahanu (841.6) with contributes 40.4 %, 39.1 %, 38.5 %, 35.4 %, 37.3 %, 37.3 %, 36.9 % and 36.3 % of the annual mean rainfall (1998 to 2019) respectively. The result showed that contribution of rainfall during Monsoon season ranges from 95.5 % to 97.0 % of the annual total rainfall for tehsils of Palghar District. The result showed that average annual rainfall (1998 to 2019) of Vasai, Jawhar, Vikramgad, Wada, Talasari, Palghar, Mokhada and Dahanu were 2855.9 mm, 2839.1 mm, 2738.9 mm, 2674.0 mm, 2633.3 mm, 2570.8 mm, 2543.6 mm and 2318.5 mm respectively.

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