scholarly journals Assessing baseflow index vulnerability to variation in dry spell length for a range of catchment and climate properties

2018 ◽  
Vol 32 (16) ◽  
pp. 2496-2509 ◽  
Author(s):  
Antonia Longobardi ◽  
Anne Frederike Van Loon
Keyword(s):  
Dry Spell ◽  
Spell Length

Temporal Changes in Flow Regime along the River Vistula

Water ◽  
2021 ◽  
Vol 13 (20) ◽  
pp. 2840
Author(s):  
Ewa Bogdanowicz ◽  
Emilia Karamuz ◽  
Renata Julita Romanowicz
Keyword(s):  
Flow Regime ◽  
Winter Season ◽  
Hydrological Regime ◽  
Mean Value ◽  
Social Perceptions ◽  
Annual Data ◽  
Spatial Changes ◽  
Precipitation Characteristics ◽  
Dry Spell ◽  
Spell Length

The flow regime in the River Vistula is influenced by climatic and geographical factors and human intervention. In this study, we focus on an analysis of flow and precipitation variability over time and space following the course of the River Vistula. Multi-purpose statistical analyses of a number of runoff and precipitation characteristics were performed to present a general overview of the temporal and spatial changes. Since the important feature of the hydrological regime of Polish rivers is the seasonality of runoff associated with the occurrence of cold (winter) and warm (summer) seasons within a hydrological year, a seasonal approach is applied to describe specific seasonal features that can be masked when using annual data. In general, the results confirm popular impressions about changes in winter season runoff characteristics, i.e., significantly decreasing daily maxima, increasing daily minima and a decrease in concentration, and so a bigger uniformity of winter daily flows. An interesting behaviour of minimum flows in the summer has been revealed, which is contrary to social perceptions and the alarming changes taking place in the other parts of the world. Additionally, precipitation indexes related to the formation of droughts show no trends, e.g., the mean value of the maximum dry spell length.

Projected changes in extreme precipitation intensity and dry spell length in Côte d’Ivoire under future climates

2020 ◽  
Vol 140 (3-4) ◽  
pp. 871-889 ◽  
Author(s):  
Assi Louis Martial Yapo ◽  
Adama Diawara ◽  
Benjamin K. Kouassi ◽  
Fidèle Yoroba ◽  
Mouhamadou Bamba Sylla ◽  
...  
Keyword(s):  
Cote D'ivoire ◽  
Extreme Precipitation ◽  
Côte D’Ivoire ◽  
Precipitation Intensity ◽  
Cote D’Ivoire ◽  
Côte D'ivoire ◽  
Dry Spell ◽  
Projected Changes ◽  
Spell Length

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 Future Changes in Wet and Dry Season Characteristics in CMIP5 and CMIP6 simulations

2021 ◽  
Author(s):  
Caroline M. Wainwright ◽  
Emily Black ◽  
Richard P. Allan
Keyword(s):  
Climate Change ◽  
South America ◽  
West Africa ◽  
Southern Africa ◽  
Dry Season ◽  
Maximum Temperature ◽  
Wet Season ◽  
Dry Spells ◽  
Dry Spell ◽  
Spell Length

AbstractClimate change will result in more dry days and longer dry spells, however, the resulting impacts on crop growth depend on the timing of these longer dry spells in the annual cycle. Using an ensemble of Coupled Model Intercomparison Project Phase 5 and Phase 6 (CMIP5 and CMIP6) simulations, and a range of emission scenarios, here we examine changes in wet and dry spell characteristics under future climate change across the extended tropics in wet and dry seasons separately. Delays in the wet seasons by up to two weeks are projected by 2070-2099 across South America, Southern Africa, West Africa and the Sahel. An increase in both mean and maximum dry spell length during the dry season is found across Central and South America, Southern Africa and Australia, with a reduction in dry season rainfall also found in these regions. Mean dry season dry spell lengths increase by 5-10 days over north-east South America and south-west Africa. However, changes in dry spell length during the wet season are much smaller across the tropics with limited model consensus. Mean dry season maximum temperature increases are found to be up to 3°C higher than mean wet season maximum temperature increases over South America, Southern Africa and parts of Asia. Longer dry spells, fewer wet days, and higher temperatures during the dry season may lead to increasing dry season aridity, and have detrimental consequences for perennial crops.

scholarly journals Evolution Des Indices Pluviométriques Extrêmes Par L'analyse De Modèles Climatiques Régionaux Du Programme CORDEX: Les Projections Climatiques Sur Le Sénégal

2017 ◽  
Vol 13 (17) ◽  
pp. 206 ◽  
Author(s):  
Alioune Badara Sarr ◽  
Moctar Camara
Keyword(s):  
West Africa ◽  
Greenhouse Gas Emission ◽  
Precipitation Amount ◽  
Extreme Rainfall ◽  
Climate Indices ◽  
Rainfall Events ◽  
Western Sahel ◽  
Dry Spell ◽  
Sahel Region ◽  
Spell Length

This study aims at characterizing the extreme rainfall events over West Africa particularly in the Sahel region and Senegal by 2100 (far future) under the greenhouse gas emission scenario RCP8.5 by analyzing the simulations of four (4) regional climate models (RCMs) of CORDEX (Regional COordinated climate Downscaling Experiment) program. The study of these extreme climate indices is crucial for the understanding of the impacts of climate change on some vital socio-economic sectors such as the agriculture in Sahel and Senegal. The results show that almost all the RCMs predict a decrease of the rainfall over most parts of the Sahel region particularly over the Western Sahel. The analysis of the climate indices such as the highest one day precipitation amount, the 99th percentile and the maximum dry spell length (CDD) shows that the RCMs (except CanRCM4) project an increase of these exceptional rainfall events over the Sahel (especially over the Western Sahel) by 2100. In Senegal, the RCMs (except RCA4) agree on a decrease of the precipitation and the number of wet days by 2100. When considering the evolution of rainfall events intensity, the highest one day precipitation amount and the 99th percentile, the RCMs (except CanRCM4) predict an increase of the extreme events which may translate into strong floods in Senegal. As for the dry and wet sequences, the RCMs projections (except those of RCA4) show an increase (respectively a decrease) of the maximum dry spell length (respectively of the maximum wet spell length) in Senegal. This increase in extreme rainfall indices may translate into a strengthening of natural disasters such as floods and drought. This work can be considered as a support for the policymakers in West Africa and particularly in Senegal for the better long-term planning of water resources and disaster management as wells as the build of a resilient agricultural system.

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. 

scholarly journals Variability and Trend Analysis of Temperature, Rainfall and Characteristics of Crop Growth Season in Eastern Zone of Tigray Region, Northern Ethiopia

2021 ◽  
Author(s):  
Amdom Gebremedhin Berhe ◽  
Solomon Habtu Misgna ◽  
Girmay Gebre-Samuel Abraha ◽  
Amanuel Zenebe Abraha
Keyword(s):  
Trend Analysis ◽  
Minimum Temperature ◽  
Rainy Season ◽  
General Trend ◽  
Crop Growth ◽  
Growth Season ◽  
Tigray Region ◽  
Eastern Zone ◽  
Dry Spell ◽  
Spell Length

Abstract Background: Long term weather analyses are very useful indicators in determining future directions and in making adjustments required to existing systems. And, in order to favor farmers to adjust their farming practices, seasonal climate outlooks are needed. The main purpose of this manuscript was thus to analyze the variability and trends of maximum and minimum temperature, monthly and seasonal rainfall series and characteristics of crop growth season in Eastern zone of Tigray region over the period of 1980–2009.Methods: Detail investigations were carried out using parametric (Linear regression) and nonparametric tests (Mankendall (Mk) and Sen’s slope estimator). Moreover, homogeneity test using a method developed by Van Belle and Hughes was used for general trend analysis. In addition, daily rainfall data to characterize crop growth season were analysed using R-Instat and XLSTAT software for trend analysis.Results: It was found that the general trend of monthly rainfall experienced an overall significant increasing trend. The seasonal rainfall experienced significantly increasing in summer main rainy season, June–September (Kiremt) while significantly decreasing in short rainy season, February– May (Belg). Likewise, the seasonal maximum temperature trends exhibited significant increase in each season while minimum temperature trend had inhomogeneous trend across seasons as well as stations. The trend of growing season characteristics (onset, cessation, LGP and dry spell length did not change significantly over the study period (1980–2009) in all stations. However, the coefficient of variability of LGP was (CV, >15%) and dry spell length was (CV, >25%) inassociation with short nature of LGP (68–85 days had a negative impact on the agricultural activities of the study area during the study period.Conclusions: Despite significant increase of rainfall in summer season, the variability of rainfall and dry spell length was very large. Hence, the study recommends crop production in the study area demands appropriate adaptation strategies that considers the erratic nature of the rainfall, the long dry spell length in the season and increasing trends of temperature.

scholarly journals The Climatic Analysis of Summer Monsoon Extreme Precipitation Events over West Africa in CMIP6 Simulations

2021 ◽  
Vol 5 (1) ◽  
pp. 25-41
Author(s):  
Nana Ama Browne Klutse ◽  
Kwesi Akumenyi Quagraine ◽  
Francis Nkrumah ◽  
Kwesi Twentwewa Quagraine ◽  
Rebecca Berkoh-Oforiwaa ◽  
...  
Keyword(s):  
West Africa ◽  
Extreme Precipitation ◽  
Heavy Rainfall ◽  
Extreme Rainfall ◽  
The Other ◽  
Rainfall Characteristics ◽  
Model Simulations ◽  
Dry Spell ◽  
The Mean ◽  
Spell Length

AbstractWe evaluate the capability of 21 models from the new state-of-the-art Coupled Model Intercomparison Project, Phase 6 (CMIP6) in the representation of present-day precipitation characteristics and extremes along with their statistics in simulating daily precipitation during the West African Monsoon (WAM) period (June–September). The study uses a set of standard extreme precipitation indices as defined by the Expert Team on Climate Change Detection and Indices constructed using CMIP6 models and observational datasets for comparison. Three observations; Global Precipitation Climatology Project (GPCP), Climate Hazards Group InfraRed Precipitation with Station data (CHIRPS), and Tropical Applications of Meteorology using SATellite and ground-based observation (TAMSAT) datasets are used for the validation of the model simulations. The results show that observed datasets present nearly the same spatial pattern but discrepancies in the magnitude of rainfall characteristics. The models show substantial discrepancies in comparison with the observations and among themselves. A number of the models depict the pattern of rainfall intensity as observed but some models overestimate the pattern over the coastal parts (FGOALS-f3-L and GFDL-ESM4) and western part (FGOALS-f3-L) of West Africa. All model simulations explicitly show the pattern of wet days but with large discrepancies in their frequencies. On extreme rainfall, half of the models express more intense extremes in the 95th percentiles while the other half simulate less intense extremes. All the models overestimate the mean maximum wet spell length except FGOALS-f3-L. The spatial patterns of the mean maximum dry spell length show a good general agreement across the different models, and the observations except for four models that show an overestimation in the Sahara subregion. INM-CM4-8 and INM-CM5-0 display smaller discrepancies from their long-term average rainfall characteristics, in terms of extreme rainfall estimates than the other CMIP6 datasets. For the frequency of heavy rainfall, TaiESM1 and IPSL-CMGA-LR perform better when compared with observational datasets. MIROC6 and GFDL-ESM4 displayed the largest error in representing the frequency of heavy rainfall and 95th percentile extremes, and therefore, cannot be reliable. The study has assessed how rainfall extremes are captured in both observation and the models. Though there are some discrepancies, it gives room for improvement of the models in the next version of CMIP.

scholarly journals Variability and Trend Analysis of Temperature, Rainfall and Characteristics of Crop Growth Season in Eastern Zone of Tigray Region, Northern Ethiopia

2021 ◽  
Author(s):  
Amdom Gebremedhin Berhe ◽  
Solomon Habtu Misgna ◽  
Girmay Gebre-Samuel Abraha ◽  
Amanuel Zenebe Abraha
Keyword(s):  
Trend Analysis ◽  
Rainy Season ◽  
General Trend ◽  
Crop Growth ◽  
Growth Season ◽  
Tigray Region ◽  
Eastern Zone ◽  
Dry Spell ◽  
Increasing Trend ◽  
Spell Length

Abstract To favour farmers and adjusting their farming practices, long term weather analyses is essential to determine future directions and making adjustments required to existing systems. The main purpose of this study was thus to analyze the variability and trends of climatic variables (temperature and rainfall) and characteristics of crop growth season in Eastern zone of Tigray region for the period of 1980–2009. Detail investigations were carried out using parametric (Linear regression) and non-parametric tests (Mankendall and Sen’s slope estimator). Moreover, homogeneity test was applied using a method developed by Van Belle and Hughes for the general trend analysis. Furthermore, the trend of rainfall end to characterize crop growth season using R-Instat and XLSTAT software. It was found that the general trend of monthly rainfall experienced an overall significant increasing trend. The seasonal rainfall experienced significantly increasing trend during the summer rainy season (June–September) whilst a significant decreasing trend occurred in the short rainy season (February–May). Likewise, the seasonal maximum temperature trends exhibited a significant increasing trend in all seasons whereas the minimum temperature showed inhomogeneous trend across seasons as well as stations. Despite significant increase of rainfall in summer season, the trend of growing season characteristics (onset, cessation, length of growing period and dry spell length) did not change significantly over the study period. However, the variability of rainfall and dry spell length was found to be very large. Hence, crop production in the study area demands appropriate adaptation strategies that considers the erratic nature of the rainfall, the long dry spell length in the season and increasing trends of temperature.

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