Analysis of Start, End and Length of the Growing Season and Number of Rainy Days in Semi-Arid Central Refit Valley of Oromia State, Ethiopia

Edao, Agere Lupi; Kibert, Kibebew; Mamo, Girma

doi:10.4172/2329-8863.1000386

Cited by 6 publications

(13 citation statements)

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“…It was observed that in Ghèzala dam the probability to have a rainfall event starting in the fifteen days of September is 0.48 with a return period of two years [25] and continues up to 39 th meteorological weeks. The wet season at Fritissa and Sidi Abdelbasset stations ends earlier than the other stations, given their location in the driest part of the transect, This confirms the results from Mupangwa et al [27] and Edao et al [28] who showed that as aridity increases, the season starts late and ends early.…”

Section: Discussionsupporting

confidence: 88%

Comprehensive study of the wet and dry spells and their extremes in the Mediterranean climate basin Northern Tunisia

Mathlouthi¹,

Lebdi

2021

SN Appl. Sci.

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In agriculture, the characterization of dry spells is essential whether it is to calibrate the water needs of crops or the flow rates of rivers. This study seeks to develop a discretization of dry and wet spells on a monthly scale while evaluating the risk of extremes using the renewal wet-dry spell model. This model consists of defining the wet spell according a negligible precipitation threshold. The structure of the model is that all parameters of the climate cycle, including its length, are random variables. To study the trend of the parameters we use the Mann–Kendall test, while the magnitude is evaluated by the Sen’s estimation method. The approach is applied to Ichkeul Lake basin in northern Tunisia to demonstrate its capacity. This region is of great agricultural and water importance, although it holds six large dams. The results show that the duration of the dry and wet spells reach’s, respectively, 49 days and 17 days. The maximum dry spell was 49 days in 1982. The Mann–Kendall test revealed three stations with significant positive trend of the monthly extreme dry spell length (at March) located in south and east of the basin. The trend analysis of the seasonal rainfall number showed one station with significant negative trend in east and one station with significant negative trend in the center of the basin. Results indicated that no significant changes in the start and end of rainy season have occurred over the past years. But a great relation with a subsequent length exists. The results of this research assist farmers and managers in establishing drought management plans. It allow, among other things, to calibrate simulation models for a more realistic management of water reservoirs. It also makes it possible to plan irrigations on a more different basis from that of observations made at regular time intervals. Highlights We analyze the trends of the drought in Ichkeul lake basin, Northern Tunisia, characterized from the daily rainfall data of five stations. The alternating wet-dry spell model and a precipitation threshold value are used to define the rainfall/dry event. The Mann–Kendall test and the Sen’s estimation method were used to analyze the possible trends and the magnitude of variables analyzed, respectively. The results show an increasing trend of maximum monthly dry spells. No significant changes in the start and end of rainy season have occurred over the past years. These analyses provide useful information for science and society and make it possible to minimize unexpected damage due to long dry spells and to have effective and efficient planning for various stakeholders.

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Section: Discussionsupporting

confidence: 88%

Comprehensive study of the wet and dry spells and their extremes in the Mediterranean climate basin Northern Tunisia

Mathlouthi¹,

Lebdi

2021

SN Appl. Sci.

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“…, west Africa monsoon(Rauch et al, 2019), Ethiopia(Segele & Lamb, 2005), Kenya(Sattar et al, 2018), Uganda(Ocen et al, 2021)among others, whether observed dataset or models simulations to assess the pattern in the future. Our analysis revealed that14-21 days delayed onset dates during MAM season observed over coastal counties (Kwale, Mombasa, Kili and Lamu) in Kenya, southwestern Ethiopia for JJA is which is similar to(Lupi Edao et al, 2018), while 21-35 days (2-5 weeks) delayed in western Uganda during DJF season. The early onset dates anomaly of 7-21 days (1-3 weeks) observed over Somali zones in southeastern Ethiopia and central Somalia districts during MAM season.…”

supporting

confidence: 59%

“…A study by (Gordon & Fitzpatrick, 2016) shows more than 18 different methods and thresholds for determining ROD, RCD and LRS in literature. The most common methods that have been applied in different region are criteria and thresholds based on accumulated 20mm rainfall total (Lupi Edao et al, 2018, Atiah et al,2021, rainfall depth method and atmospheric dynamics (Raes et al, 2004), water balance and evapotranspiration (Mugalavai et al, 2008), number of rainy days and dry spell in coming days (Gudoshava et al, 2020). A single onset criterion applied in both wetter regions and semi-arid with longer dry spell length could lead to unreasonable onset dates ( Segele & Lamb, 2005), therefore onset criterion applied in rain-fed agriculture regions for example should combine criterion of at least 20mm rainy, how many consecutive wet days and dry-spell length not exceeding some days are well pre-de ned.…”

mentioning

confidence: 99%

Changes and Variability in rainfall onset, cessation and length of rainy season in the IGAD region of Eastern Africa

Omay

Muthama

Oludhe

et al. 2022

Preprint

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Rainfall Onset Dates (ROD), Rainfall Cessation Dates (RCD) and Length of rainy Season (LRS) are crucial for Crop production and food security in Eastern Africa yet scantily documented. This paper seeks to investigate the spatial patterns of these parameters. Data used are Climate Hazards Group InfraRed Precipitation with Station data (CHIRPS) and National Oceanic and Atmospheric Administration (NOAA) gridded temperature. Threshold of 0.1mm for rainy day, 20mm over 5 days with at least 3 rain days and dry spell not exceeding 7 days in the next 21 days were used to determine RODs, while Potential Evapotranspiration (PET) and Water Balance (WB) criteria were computed to determine RCDs then differences between ROD and RCD were used in calculating LRS. The results showed early rainfall cessation over more than 30 counties in Kenya lead to shortened rainy season by 10–20 days during MAM season. Similarly, 20–40 days early onset dates are observed in most counties in upper Nile, Unity and Jonglei states in South Sudan, while 20–40 days delayed rainfall onset was observed in Khartoum and southern parts of Nile state western Darfur, eastern and Aljazeera states in Sudan, most parts of Ethiopia and Eritrea districts during JJA season. Highlands of western and Nyanza region in Kenya, most parts of Uganda observed rainfall onset by March and no sign of cessation before November. Early cessation over northern Uganda districts was behind shortened LRS, furthermore, the early RODs over western and southwestern Uganda districts increased LRS. Prolonged dry conditions over northern Sudan, southeastern parts of South Sudan, northern Kenya, central Somalia, northern Darfour, Kordofan and northern parts of Sudan exacerbated by significant delayed onset and early cessation of rainfall. These findings are important for rain-fed agricultural planning and food security in the IGAD region of Eastern Africa.

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“…The criterion used in this study was a rainfall of 20 mm or more accumulated over three consecutive rainy days after a specified date (in this case, June 1) with no dry spell greater than 9 days in the next 21 days (Girma, 2005;Liben, 2013;Edao et al, 2018). SOS was calculated from Equation ( 15), given by;…”

Section: Analysis Of Start End and Length Of Growing Periodsmentioning

confidence: 99%

“…From the perspective of crop production, another crucial aspect of rainfall that must be taken into consideration is the level of variability observed in the length of the growing period (LGP) (Solomon et al, 2015;Edao et al, 2018) as well as the frequency of rainy days (Mugalavai et al, 2008;Wagaye and Eshetu, 2021).…”

Section: Introductionmentioning

confidence: 99%

Rainfall Variability and Trends Analysis in the Sorghum Growing Semi-Arid Rift Valley of Ethiopia

Edao,

Dechassa,

Merga

et al. 2023

Preprint

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In Ethiopia, 60% of the land is covered by sorghum, and the climate affects the major producing regions.The objective of this work was to assess variability and trends of rainfall in the semi-arid Rift Valley of Ethiopia. 40 years of rainfall data were analyzed for 11 stations. The selected parameters were analyzed for rainfall variability and trend analysis was performed following Mann–Kendall methods. The start and end of the growing season, length of the growing period, and dry spells were analyzed for the stations. The results showed in all the locations was the highest mean monthly rainfall recorded in July, and August then followed by September. Compared to the longest rainy period (52.3–70.8%), the short rainy period (19.4–33.2%) contributes less rainfall to the annual rainfall which was also associated with high inter-seasonal variability (CV ranged from 31.5 to 88%) short rain season. PCI value in studied regions in all stations showed the existence of high concentration in seasonal rainfall distribution. Sen’s slope for NRVE, ERVE, and CRV increases by 0.02-0.81, 0.05-0.71, and 0.02-0.81 mm/yr. in September. Rainfall from 0.31-2.76 mm/yr. decreases to a 0.19-5.12 mm/yr increase in the short and main seasons. Rainfall has increased in some stations (from 0.042 to 3.88 mm/yr.) but decreased in five stations (1.29 to 3.71 mm/yr.). Stations with different rainfall onset and CV (4.9%–16.6%) have varying rainy seasons (24 to 200 days), which affect crop yield. Longer periods lower the risk; it rains every 90 days for crops. Optimize management based on LGP and rainfall variations at stations. Climate change risks crop yields. Consider early crops and rainwater collection.

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Analysis of Start, End and Length of the Growing Season and Number of Rainy Days in Semi-Arid Central Refit Valley of Oromia State, Ethiopia

Cited by 6 publications

References 0 publications

Comprehensive study of the wet and dry spells and their extremes in the Mediterranean climate basin Northern Tunisia

Comprehensive study of the wet and dry spells and their extremes in the Mediterranean climate basin Northern Tunisia

Changes and Variability in rainfall onset, cessation and length of rainy season in the IGAD region of Eastern Africa

Rainfall Variability and Trends Analysis in the Sorghum Growing Semi-Arid Rift Valley of Ethiopia

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