scholarly journals Spatial and Temporal Analysis of Dry and Wet Spells in Upper Awash River Basin, Ethiopia

Water ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 3051
Author(s):  
Girma Berhe Adane ◽  
Birtukan Abebe Hirpa ◽  
Chul-Hee Lim ◽  
Woo-Kyun Lee
Keyword(s):  
River Basin ◽  
Management Practices ◽  
Markov Chain Model ◽  
Temporal Analysis ◽  
Chain Model ◽  
Rainfall Analysis ◽  
Dry Spells ◽  
Dry Spell ◽  
Awash River Basin ◽  
Wet Spells

This study aimed to analyze the probability of the occurrence of dry/wet spell rainfall using the Markov chain model in the Upper Awash River Basin, Ethiopia. The rainfall analysis was conducted in the short rainy (Belg) and long rainy (Kiremt) seasons on a dekadal (10–day) scale over a 30-year period. In the Belg season, continuous, three-dekad dry spells were prevalent at all stations. Persistent dry spells might result in meteorological, hydrological, and socio-economic drought (in that order) and merge with the Kiremt season. The consecutive wet dekads of the Kiremt season indicate a higher probability of wet dekads at all stations, except Metehara. This station experienced a short duration (dekads 20–23) of wet spells, in which precipitation is more than 50% likely. Nevertheless, surplus rainwater may be recorded at Debrezeit and Wonji only in the Kiremt season because of a higher probability of wet spells in most dekads (dekads 19–24). At these stations, rainfall can be harvested for better water management practices to supply irrigation during the dry season, to conserve moisture, and to reduce erosion. This reduces the vulnerability of the farmers around the river basin, particularly in areas where dry spell dekads are dominant.

scholarly journals Climatology of dry and wet spell over Vidarbha region during monsoon months

MAUSAM ◽  
2021 ◽  
Vol 52 (2) ◽  
pp. 365-370
Author(s):  
JAYANTA SARKAR ◽  
K. SEETHARAM ◽  
S. K. SHAHA
Keyword(s):  
Markov Chain Model ◽  
Monsoon Season ◽  
Daily Rainfall ◽  
Chain Model ◽  
Stationary Probability ◽  
South West ◽  
South West Monsoon ◽  
Dry Spell ◽  
West Monsoon ◽  
Wet Spells

In this investigation 10-day period-wise simple probability, 10-day period-wise  probability of consecutive dry and wet spells of different lengths, and month-wise different parameters, and properties of Markov Chain Model over Vidarbha region during south-west monsoon months have been studied.   For this purpose, daily rainfall data (1 June – 30 September) of 11 stations covering all the districts of Vidarbha for the period 1960-90 have been utilized.   The study reveals that over Vidarbha during monsoon season (June - September) probability of a day being wet and probability of consecutive wet spell of different lengths are by and large high during the last and first 10-day periods of July and August respectively when the monsoon is at its peak. During the first two 10-day periods in June and last two 10-day periods in September, the probabilities of a dry day and that of consecutive dry spell of different lengths and quite high. During July and August a maximum of 12-14 wet days are expected and wet spell, on an average, lasts for 2 days. Stationary probability of the occurrence of wet day (pi2) is found to be maximum during July making it the most humid month in the monsoon season.

scholarly journals Spatial and spatio-temporal analysis of Salmonella infection in dairy herds in England and Wales

2008 ◽  
Vol 137 (6) ◽  
pp. 847-857 ◽  
Author(s):  
S. E. FENTON ◽  
H. E. CLOUGH ◽  
P. J. DIGGLE ◽  
S. J. EVANS ◽  
H. C. DAVISON ◽  
...  
Keyword(s):  
Transition Probabilities ◽  
Spatial Clustering ◽  
Markov Chain Model ◽  
Temporal Analysis ◽  
Dairy Herds ◽  
Chain Model ◽  
Time Period ◽  
Spatio Temporal ◽  
Using Data ◽  
Residual Deviance

SUMMARYUsing data from a cohort study conducted by the Veterinary Laboratories Agency (VLA), evidence of spatial clustering at distances up to 30 km was found for S. Agama and S. Dublin (P values of 0·001) and borderline evidence was found for spatial clustering of S. Typhimurium (P=0·077). The evolution of infection status of study farms over time was modelled using a Markov Chain model with transition probabilities describing changes in status at each of four visits, allowing for the effect of sampling visit. The degree of geographical clustering of infection, having allowed for temporal effects, was assessed by comparing the residual deviance from a model including a measure of recent neighbourhood infection levels with one excluding this variable. The number of cases arising within a defined distance and time period of an index case was higher than expected. This provides evidence for spatial and spatio-temporal clustering, which suggests either a contagious process (e.g. through direct or indirect farm-to-farm transmission) or geographically localized environmental and/or farm factors which increase the risk of infection. The results emphasize the different epidemiology of the three Salmonella serovars investigated.

scholarly journals Seasonal and Interannual Variability of Wet and Dry Spells over Two Urban Regions in the Western Maritime Continent

2016 ◽  
Vol 17 (5) ◽  
pp. 1579-1600 ◽  
Author(s):  
Pradeep V. Mandapaka ◽  
Xiaosheng Qin ◽  
Edmond Yat-Man Lo
Keyword(s):  
Interannual Variability ◽  
Specific Humidity ◽  
Boreal Summer ◽  
Boreal Winter ◽  
Urban Regions ◽  
Seasonal And Interannual Variability ◽  
Dry Spells ◽  
Dry Spell ◽  
Spell Length ◽  
Wet Spells

Abstract Daily rainfall data from two urban regions in Southeast Asia are analyzed to study seasonal and interannual variability of wet and dry spells. The analysis is carried out using 35 years of data from Singapore and 23 years of data from Jakarta. The frequency distribution of wet (dry) spells and their relative contribution to the total number of wet (dry) days and to the total rainfall are studied using 15 statistical indicators. At the annual scale, Singapore has a greater number of wet spells and a larger mean wet spell length compared to Jakarta. However, both cities have equal probability of extreme wet spells. Seasonal-scale analysis shows that Singapore is drier (wetter) than Jakarta during boreal winter (summer). The probability of extreme wet spells is lower (higher) for Singapore than Jakarta during boreal winter (summer). The results show a stronger contrast between Singapore and Jakarta during boreal summer. The study also examined the time series of Singapore wet and dry spell indicators for the presence of interannual trends. The results indicate statistically significant upward trends for a majority of wet spell indicators. The wet day percentage and mean wet spell length are increasing at 2.0% decade−1 and 0.18 days decade−1, respectively. Analysis of dynamic and thermodynamic variables from ERA-Interim during the study period indicates a strengthening of low-level convergence and vertical motion and an increase in specific humidity and atmospheric instability (convective available potential energy), which explain the increasing trends observed in Singapore wet spell indicators.

scholarly journals Wet and dry spells in Senegal: comparison of detection based on satellite products, reanalysis, and in situ estimates

2021 ◽  
Vol 21 (3) ◽  
pp. 1051-1069
Author(s):  
Cheikh Modou Noreyni Fall ◽  
Christophe Lavaysse ◽  
Mamadou Simina Drame ◽  
Geremy Panthou ◽  
Amadou Thierno Gaye
Keyword(s):  
Measurement Techniques ◽  
West African Monsoon ◽  
Tropical Rainfall Measuring Mission ◽  
Early Warning Systems ◽  
Rain Gauge ◽  
Major Influence ◽  
Dry Spells ◽  
Dry Spell ◽  
Spatio Temporal ◽  
Wet Spells

Abstract. In this study, the detection and characteristics of dry/wet spells (defined as episodes when precipitation is abnormally low or high compared to usual climatology) drawn from several datasets are compared for Senegal. Here, four datasets are based on satellite data (TRMM-3B42 V7, CMORPH V1.0, TAMSAT V3, and CHIRPS V2. 0), two on reanalysis products (NCEP-CFSR and ERA5), and three on rain gauge observations (CPC Unified V1.0/RT and a 65-rain-gauge network regridded by using two kriging methods, namely ordinary kriging, OK, and block kriging, BK). All datasets were converted to the same spatio-temporal resolution: daily cumulative rainfall on a regular 0.25∘ grid. The BK dataset was used as a reference. Despite strong agreement between the datasets on the spatial variability in cumulative seasonal rainfall (correlations ranging from 0.94 to 0.99), there were significant disparities in dry/wet spells. The occurrence of dry spells is less in products using infrared measurement techniques than in products coupling infrared and microwave, pointing to more frequent dry spell events. All datasets show that dry spells appear to be more frequent at the start and end of rainy seasons. Thus, dry spell occurrences have a major influence on the duration of the rainy season, in particular through the “false onset” or “early cessation” of seasons. The amplitude of wet spells shows the greatest variation between datasets. Indeed, these major wet spells appear more intense in the OK and Tropical Rainfall Measuring Mission (TRMM) datasets than in the others. Lastly, the products indicate a similar wet spell frequency occurring at the height of the West African monsoon. Our findings provide guidance in choosing the most suitable datasets for implementing early warning systems (EWSs) using a multi-risk approach and integrating effective dry/wet spell indicators for monitoring and detecting extreme events.

scholarly journals Analysis of rainfall trend and variability for agricultural water management in Awash River Basin, Ethiopia

2016 ◽  
Vol 8 (1) ◽  
pp. 127-141 ◽  
Author(s):  
Daniel Bekele ◽  
Tena Alamirew ◽  
Asfaw Kebede ◽  
Gete Zeleke ◽  
Assefa M. Melese
Keyword(s):  
Water Management ◽  
River Basin ◽  
Rainy Season ◽  
Rainfall Variability ◽  
Agricultural Water ◽  
Agricultural Water Management ◽  
Supplementary Irrigation ◽  
Dry Spell ◽  
Awash River Basin ◽  
The Impact

The national economy and food security of many sub-Saharan countries relies on rain-fed agriculture, hence the impact of rainfall variability is highly significant. The intent of this study is to characterize rainfall variability and trend in Awash River Basin for agricultural water management using standard rainfall statistical descriptors. Long-term climate data of 12 stations were analyzed. Onset and cessation dates, length of growing period (LGP) and probability of dry spell occurrences were analysed using INSTAT Plus software. The Mann–Kendall test and the Sen's slope method were used to assess the statistical significance of the trend. The results show high variability of rainfall (38–73%), LGP (30–38 days) and high probability of dry spell occurrence (up to 100%) during the Belg season (the short rainy season from March to May) compared with the Kiremt season (the main rainy season from June to September) in all stations. Belg season showed a non-significant decline trend in most of the stations, whereas the Kiremt season indicated the contrary. The finding also revealed that supplementary irrigation is vital, especially in the Belg season to cover up to 40% of the crop water requirement deficit.

scholarly journals Droughts and the Impacts of Dry Spells in North of Iraq

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Safieh Javadinejad ◽  
David Hannah ◽  
Stefan Krause ◽  
Rebwar Dara ◽  
Forough Jafary ◽  
...  
Keyword(s):  
Temporal Analysis ◽  
Distribution Functions ◽  
Spi Index ◽  
The North ◽  
Generalized Pareto ◽  
Dry Spells ◽  
Dry Spell ◽  
Complete Series ◽  
Drought Occurrence ◽  
Spell Length

Different sets of dry spell length such as complete series, monthly maximum, seasonal maximum, and annual maximum are applied and modeled with different probability distribution functions (such as Gumbel Max, generalized extreme value, Log-Logistic, generalized logistic, inverse Gaussian, Log-Pearson 3, generalized Pareto) to recognize in which duration, dry spells cause drought. The drought situation and temporal analysis in the North of Iraq region were done using the SPI index and by software of DrinC at a time scale of 3.6 and 12 months. Because of applicability, availability of data and the aim of the study, SPI is selected to analyze the dry spells in this study. Based on the maximum length of the available statistical period, the statistics for the years 1980 to 2019 were used from nine meteorological stations for analysis. The results of the study showed the severity of drought during the study period which related to dry spells. The results of this research confirm the variation of drought occurrence with varying degrees in different time and different dry spells condition in Iraq. 

Sign in / Sign up

Export Citation Format

Share Document