Vegetation carrying capacity of arid regions: on the fraction of rainfall sheltered from surface evaporation

2020 ◽  
Author(s):  
Dani Or ◽  
Peter Lehmann ◽  
Samuel Bickel ◽  
Simone Fatichi
Keyword(s):  
Carrying Capacity ◽  
Arid Regions ◽  
Potential Evapotranspiration ◽  
Rainfall Variability ◽  
Aridity Index ◽  
Arid Lands ◽  
Soil Water Storage ◽  
Annual Rainfall ◽  
Rainfall Events ◽  
Surface Evaporation

<p>Arid lands represent one third of terrestrial surfaces with ecosystems uniquely adapted to water limitations. Arid regions are characterized by low rainfall and sparse vegetation with potential evapotranspiration (ET<sub>0</sub>) exceeding annual rainfall (P) and surface evaporation dominating water losses. The objective was to quantify the fraction of rainwater sheltered from surface evaporation to estimate arid region vegetation carrying capacity. The surface evaporation capacitor (SEC) model was used to quantify surface evaporation from the climatic record of rainfall and potential evaporation. The SEC uses soil-specific active evaporation depth where only rainfall events that exceed its critical capacitance result in leakage into deeper layers. This “leakage” becomes protected from surface evaporation and may support vegetation or inter-annual storage. Focusing on arid regions (aridity index P/ET<sub>0</sub>< 0.2) we illustrate the strong correlation between evaporation-protected rainwater and net primary productivity (NPP) using typical values of water use efficiency. SEC-estimated NPP values were in good agreement with observations and predictions by a state-of-the art ecohydrological model (T&C). Evaporation-protected soil water storage is generated during a few large rainfall events that exceed surface capacitance. This leakage increases with increasing rainfall variability, potentially enhancing vegetation carrying capacity by diverting larger fractions of rainfall from surface evaporation to vegetation-supporting “leakage”. The potential increase in carrying capacity and resulting vegetation cover are greatly influenced by (i) the change in rainfall variability, (ii) soil type, and (iii) surface features that concentrate or divert runoff. We discuss implications of this mechanism for global greening of arid lands and woody plant encroachment.</p>

scholarly journals The role of climatic and terrain attributes in estimating baseflow recession in tropical catchments

2010 ◽  
Vol 14 (11) ◽  
pp. 2193-2205 ◽  
Author(s):  
J. L. Peña-Arancibia ◽  
A. I. J. M. van Dijk ◽  
M. Mulligan ◽  
L. A. Bruijnzeel
Keyword(s):  
Potential Evapotranspiration ◽  
Aridity Index ◽  
Global Scale ◽  
Tree Cover ◽  
Annual Rainfall ◽  
Ungauged Catchments ◽  
Ongoing Research ◽  
Daily Streamflow ◽  
Terrain Attributes ◽  
Streamflow Data

Abstract. The understanding of low flows in rivers is paramount more than ever as demand for water increases on a global scale. At the same time, limited streamflow data to investigate this phenomenon, particularly in the tropics, makes the provision of accurate estimations in ungauged areas an ongoing research need. This paper analysed the potential of climatic and terrain attributes of 167 tropical and sub-tropical unregulated catchments to predict baseflow recession rates. Daily streamflow data (m3 s–1) from the Global River Discharge Center (GRDC) and a linear reservoir model were used to obtain baseflow recession coefficients (kbf) for these catchments. Climatic attributes included annual and seasonal indicators of rainfall and potential evapotranspiration. Terrain attributes included indicators of catchment shape, morphology, land cover, soils and geology. Stepwise regression was used to identify the best predictors for baseflow recession coefficients. Mean annual rainfall (MAR) and aridity index (AI) were found to explain 49% of the spatial variation of kbf. The rest of climatic indices and the terrain indices average catchment slope (SLO) and tree cover were also good predictors, but co-correlated with MAR. Catchment elongation (CE), a measure of catchment shape, was also found to be statistically significant, although weakly correlated. An analysis of clusters of catchments of smaller size, showed that in these areas, presumably with some similarity of soils and geology due to proximity, residuals of the regression could be explained by SLO and CE. The approach used provides a potential alternative for kbf parameterisation in ungauged catchments.

scholarly journals Dominance of climate warming effects on recent drying trends over wet monsoon regions

2017 ◽  
Vol 17 (17) ◽  
pp. 10467-10476 ◽  
Author(s):  
Chang-Eui Park ◽  
Su-Jong Jeong ◽  
Chang-Hoi Ho ◽  
Hoonyoung Park ◽  
Shilong Piao ◽  
...  
Keyword(s):  
Arid Regions ◽  
Potential Evapotranspiration ◽  
Surface Air Temperature ◽  
Aridity Index ◽  
Monsoon Region ◽  
Eastern Asia ◽  
Weather Stations ◽  
Climate Parameter ◽  
Socioeconomic Consequences ◽  
Water Holding

Abstract. Understanding changes in background dryness over land is key information for adapting to climate change because of its critical socioeconomic consequences. However, causes of continental dryness changes remain uncertain because various climate parameters control dryness. Here, we verify dominant climate variables determining dryness trends over continental eastern Asia, which is characterized by diverse hydroclimate regimes ranging from arid to humid, by quantifying the relative effects of changes in precipitation, solar radiation, wind speed, surface air temperature, and relative humidity on trends in the aridity index based on observed data from 189 weather stations for the period of 1961–2010. Before the early 1980s (1961–1983), change in precipitation is a primary condition for determining aridity trends. In the later period (1984–2010), the dominant climate parameter for aridity trends varies according to the hydroclimate regime. Drying trends in arid regions are mostly explained by reduced precipitation. In contrast, the increase in potential evapotranspiration due to increased atmospheric water-holding capacity, a secondary impact of warming, works to increase aridity over the humid monsoon region despite an enhanced water supply and relatively less warming. Our results show significant drying effects of warming over the humid monsoon region in recent decades; this also supports the drying trends over warm and water-sufficient regions in future climate.

scholarly journals Evaluation and Application of Multi-Source Satellite Rainfall Product CHIRPS to Assess Spatio-Temporal Rainfall Variability on Data-Sparse Western Margins of Ethiopian Highlands

2019 ◽  
Vol 11 (22) ◽  
pp. 2688 ◽  
Author(s):  
Ashebir Sewale Belay ◽  
Ayele Almaw Fenta ◽  
Alemu Yenehun ◽  
Fenta Nigate ◽  
Seifu A. Tilahun ◽  
...  
Keyword(s):  
Rainfall Variability ◽  
Daily Rainfall ◽  
Annual Rainfall ◽  
Integration Time ◽  
Spatial And Temporal Variability ◽  
Rainfall Events ◽  
Rainfall Characteristics ◽  
Mean Annual Rainfall ◽  
Time Space ◽  
Spatio Temporal

The spatio-temporal characteristic of rainfall in the Beles Basin of Ethiopia is poorly understood, mainly due to lack of data. With recent advances in remote sensing, satellite derived rainfall products have become alternative sources of rainfall data for such poorly gauged areas. The objectives of this study were: (i) to evaluate a multi-source rainfall product (Climate Hazards Group Infrared Precipitation with Stations: CHIRPS) for the Beles Basin using gauge measurements and (ii) to assess the spatial and temporal variability of rainfall across the basin using validated CHIRPS data for the period 1981–2017. Categorical and continuous validation statistics were used to evaluate the performance, and time-space variability of rainfall was analyzed using GIS operations and statistical methods. Results showed a slight overestimation of rainfall occurrence by CHIRPS for the lowland region and underestimation for the highland region. CHIRPS underestimated the proportion of light daily rainfall events and overestimated the proportion of high intensity daily rainfall events. CHIRPS rainfall amount estimates were better in highland regions than in lowland regions, and became more accurate as the duration of the integration time increases from days to months. The annual spatio-temporal analysis result using CHIRPS revealed: a mean annual rainfall of the basin is 1490 mm (1050–2090 mm), a 50 mm increase of mean annual rainfall per 100 m elevation rise, periodical and persistent drought occurrence every 8 to 10 years, a significant increasing trend of rainfall (~5 mm year−1), high rainfall variability observed at the lowland and drier parts of the basin and high coefficient of variation of monthly rainfall in March and April (revealing occurrence of bimodal rainfall characteristics). This study shows that the performance of CHIRPS product can vary spatially within a small basin level, and CHIRPS can help for better decision making in poorly gauged areas by giving an option to understand the space-time variability of rainfall characteristics.

scholarly journals Watershed-Based Rainfall variability and trends of extreme rainfall events in South East Awash Basin, Ethiopia

2019 ◽  
Vol 6 (6) ◽  
pp. 5524-5530
Author(s):  
Yonas Tadesse Alemu
Keyword(s):  
Coefficient Of Variation ◽  
Rainy Season ◽  
Rainfall Variability ◽  
Extreme Rainfall ◽  
Annual Rainfall ◽  
Extreme Rainfall Events ◽  
Rainfall Events ◽  
Precipitation Distribution ◽  
Precipitation Concentration ◽  
Dire Dawa

This study presents analysis of Rainfall variability and trends of extreme rainfall events in the Oda Gunufeta -Cherecha -Dechatu watershed, Awash Drainage Basin, Eastern Ethiopia. The study employed the coefficient of variation and the Precipitation Concentration Index (PCI) as statistical descriptors of rainfall variability. The indices at the five stations were subjected to non-parametric Mann-Kendall test to detect the trend over the period between 1985 to 2014. The results of the study revealed that, the watershed experiences moderate inter-annual rainfall variability. The Belg rainfall shows high variability than Kiremt rainfall. Highest Belg & Kiremt rainfall variability is observed in Dire Dawa with coefficient of variation of 46% and 40% respectively. The annual PCI for the watershed in all the stations under investigation during the record periods showed that 100% of the years for which the annual PCI was estimated fell within the irregular precipitation distribution range or high precipitation concentration. The irregular precipitation distribution also extended to all the stations in short rainy season (Belg rainfall) and in two stations in the main rainy season (Kiremt season). With regard to the rainfall trend, the annual rainfall has showed a negative trend in most of the stations for the period 1985-2014. The Mann–Kendall trend test during the Kiremt season shows a positive trend in Dengego, Dire Dawa, Combolcha and Haramaya and the increasing tendency is significant at p<0.1 in Degego, p<0.05 in Dire Dawa, p <0.05 in Combolcha and p <0.01 in Haramaya. The heavy rainfall events, the 90th & 95th percentiles, in all the five stations showed an increasing pattern but except in Combolcha the trends are not statistically significant. This implies that the watershed has been under increased rainfall intensity and this in turn has the potential cause for high risk of flood occurrences.

Comparing fixed and flexible stocking as adaptations to inter-annual rainfall variability in the extensive beef industry of northern Australia

2016 ◽  
Vol 38 (1) ◽  
pp. 85 ◽  
Author(s):  
Lester Pahl ◽  
Joe Scanlan ◽  
Giselle Whish ◽  
Robyn Cowley ◽  
Neil MacLeod
Keyword(s):  
Carrying Capacity ◽  
Rainfall Variability ◽  
Full Range ◽  
Herd Size ◽  
Annual Rainfall ◽  
Northern Australia ◽  
Beef Industry ◽  
Growing Seasons ◽  
Stocking Rates

Many beef producers within the extensive cattle industry of northern Australia attempt to maintain a constant herd size from year-to-year (fixed stocking), whereas others adjust stock numbers to varying degrees annually in response to changes in forage supply. The effects of these strategies on pasture condition and cattle productivity cannot easily be assessed by grazing trials. Simulation studies, which include feedbacks of changes to pasture condition on cattle liveweight gain, can extend the results of grazing trials both spatially and temporally. They can compare a large number of strategies, over long periods of time, for a range of climate periods, at locations which differ markedly in climate. This simulation study compared the pasture condition and cattle productivity achieved by fixed stocking at the long-term carrying capacity with that of 55 flexible stocking strategies at 28 locations across Queensland and the Northern Territory. Flexible stocking strategies differed markedly in the degree they increased or decreased cattle stocking rates after good and poor pasture growing seasons, respectively. The 28 locations covered the full range in average annual rainfall and inter-annual rainfall variability experienced across northern Australia. Constrained flexibility, which limited increases in stocking rates after good growing seasons to 10% but decreased them by up to 20% after poor growing seasons, provides sustainable productivity gains for cattle producers in northern Australia. This strategy can improve pasture condition and increase cattle productivity relative to fixed stocking at the long-term carrying capacity, and its capacity to do this was greatest in the semiarid rangeland regions that contain the majority of beef cattle in northern Australia. More flexible stocking strategies, which also increased stocking rates after good growing seasons by only half as much as they decreased them after poor growing seasons, were equally sustainable and more productive than constrained flexibility, but are often impractical at property and industry scales. Strategies with the highest limits (e.g. 70%) for both annual increases and decreases in stocking rates could achieve higher cattle productivity, but this was at the expense of pasture condition and was not sustainable. Constrained flexible stocking, with a 10% limit for increases and a 20% limit for decreases in stocking rates annually, is a risk-averse adaptation to high and unpredictable rainfall variability for the extensive beef industry of northern Australia.

scholarly journals The role of climatic and terrain attributes in estimating baseflow recession in tropical catchments

2010 ◽  
Vol 7 (4) ◽  
pp. 4059-4087 ◽  
Author(s):  
J. L. Peña-Arancibia ◽  
A. I. J. M. van Dijk ◽  
M. Mulligan ◽  
L. A. Bruijnzeel
Keyword(s):  
Potential Evapotranspiration ◽  
Aridity Index ◽  
Global Scale ◽  
Tree Cover ◽  
Annual Rainfall ◽  
Ongoing Research ◽  
Terrain Attributes ◽  
Recession Rates ◽  
Potential Alternative ◽  
The Tropics

Abstract. The understanding of low flows in rivers is paramount more than ever as demand for water increases on a global scale. At the same time, limited streamflow data to investigate this phenomenon, particularly in the tropics, makes the provision of accurate estimations in ungauged areas an ongoing research need. This paper analysed the potential of climatic and terrain attributes of 167 tropical and sub-tropical unregulated catchments to predict baseflow recession rates. Climatic attributes included annual and seasonal indicators of rainfall and potential evapotranspiration. Terrain attributes included indicators of catchment shape, morphology, land cover, soils and geology. Stepwise regression was used to identify the best predictors for baseflow recession coefficients (kbf). Mean annual rainfall (MAR) and aridity index (AI) were found to explain 49% of the spatial variation of kbf. The rest of climatic indices plus average catchment slope (SLO) and tree cover were also good predictors, but co-correlated with MAR. Catchment elongation (CE), a measure of catchment shape, was also found to be statistically significant, although weakly correlated. An analysis of clusters of catchments of smaller size, showed that in these areas, presumably with some similarity of soils and geology due to proximity, residuals of the regression could be explained by SLO and CE. The approach used provides a~potential alternative for kbf parameterisation in ungauged areas.

scholarly journals Rainfall Variability and Adaptation of Tomatoes Farmers in Santa: Northwest Region of Cameroon

2021 ◽  
pp. 699-711
Author(s):  
Majoumo Christelle Malyse
Keyword(s):  
Rainfall Variability ◽  
Spatiotemporal Variability ◽  
Annual Rainfall ◽  
Crop Failure ◽  
Rainfall Events ◽  
North West ◽  
Market Gardening ◽  
The Government ◽  
Northwest Region ◽  
The Impact

AbstractThe Santa agrarian basin being one of the main market gardening basins in Cameroon and one of the producers of tomatoes in the country is vulnerable to the impact of rainfall variability. The spatiotemporal variability of rainfall through the annual, monthly, and daily fluctuations has greatly affected the market gardening sector in general and tomatoes production in particular. Thus, given rise to the research topic “Rainfall variability and adaptation of tomatoes farmers in Santa North west region of Cameroon,” its principal objective is to contribute to better understanding of the recent changes occurring in tomatoes production and productivity in Santa. To attain this objective, a principal hypothesis was formulated that rainfall variability instead of unnatural conditions or human constraints justifies changes observed in tomatoes production in Santa and resulting adaptation strategies developed by peasants and stakeholders.Our study came out with several findings, among which includes rainfall events in Santa fluctuate in time and in space with reduction in the number of rainy day and increase in the intensity of rainfall events causing soil erosion, infertility, and frequent crop diseases, insects, and pests. Extreme events such as drought and flooding have equally become frequent in the area especially during the different cycles of tomatoes production disrupting the agricultural calendar and causing crop failure and decrease in yields with Pearson’s correlation of 0.017. This positive value shows that there is a relationship between annual rainfall and tomatoes output in Santa. Tomatoes farmers in Santa are struggling to adapt locally to this situations, but their efforts are still limited especially due to their low level of education and poverty. Finally, it was seen that the output of tomatoes over the years in Santa has a strong correlation with rainfall. Based on the findings of this study, the government is called upon to assist farmers in their adaptation options.

scholarly journals Climatic Characterization and Temporal Analysis of Rainfall in the Municipality of Cruzeiro do Sul - AC, Brazil

2020 ◽  
Vol 35 (4) ◽  
pp. 577-584
Author(s):  
Ednaria Santos de Araujo ◽  
Maila Pereira de Almeida ◽  
Kelly Nascimento Leite ◽  
Jefferson Rodrigues dos Santos Silva ◽  
Edson Alves de Araújo ◽  
...  
Keyword(s):  
Potential Evapotranspiration ◽  
Temporal Distribution ◽  
Temporal Analysis ◽  
Northern Region ◽  
Soil Water Storage ◽  
Annual Rainfall ◽  
Water Deficiency ◽  
Humid Climate ◽  
Small Water ◽  
Water Surplus

Abstract The Climatological Water Budget (CWB) determined by the Thornthwaite and Matter (1955) allows the temporal visualization of the variables that compose the climate, thus allowing the climatic characterization of a region. Therefore, this work aimed at identifying and quantifying the months of water surplus and deficit through CWB to characterize the climate for the municipality of Cruzeiro do Sul - AC, Brazil, and analyze the temporal distribution of rainfall for the municipality. We used daily precipitation and temperature values and procedures to fill in the database. We calculated the potential evapotranspiration (ETP) using the Hargreaves Samani method (1985). Subsequently, we determined the periods of soil water storage (SWS), water deficiency (DEF), and water surplus (SUR) on a monthly scale. The climate of Cruzeiro do Sul, located in the northern region of Brazil, was characterized according to the Thornthwaite (1955) as B1rA'a' for a AWC of 140 mm, that is, a humid climate with annual rainfall average of 2227 mm and real evapotranspiration of 1660 mm, with small water deficiency in the months from June to October, with no thermal deficiency, and summer concentrated in three months with an average air temperature of 25 °C ranging between 18 °C and 32 °C.

scholarly journals Mechanisms Associated with Large Daily Rainfall Events in Northeast Brazil

2011 ◽  
Vol 24 (2) ◽  
pp. 376-396 ◽  
Author(s):  
Brant Liebmann ◽  
George N. Kiladis ◽  
Dave Allured ◽  
Carolina S. Vera ◽  
Charles Jones ◽  
...  
Keyword(s):  
Daily Rainfall ◽  
Annual Rainfall ◽  
Northeast Brazil ◽  
Kelvin Wave ◽  
Rainfall Events ◽  
Independent Events ◽  
Precipitation Anomalies ◽  
Wave Trains ◽  
Using Data ◽  
Forcing Mechanisms

Abstract The mechanisms resulting in large daily rainfall events in Northeast Brazil are analyzed using data filtering to exclude periods longer than 30 days. Composites of circulation fields that include all independent events do not reveal any obvious forcing mechanisms as multiple patterns contribute to Northeast Brazil precipitation variability. To isolate coherent patterns, subsets of events are selected based on anomalies that precede the Northeast Brazil precipitation events at different locations. The results indicate that at 10°S, 40°W, the area of lowest annual rainfall in Brazil, precipitation occurs mainly in association with trailing midlatitude synoptic wave trains originating in either hemisphere. Closer to the equator at 5°S, 37.5°W, an additional convection precursor is found to the west, with a spatial structure consistent with that of a Kelvin wave. Although these two sites are located within only several hundred kilometers of each other and the midlatitude patterns that induce precipitation appear to be quite similar, the dates on which large precipitation anomalies occur at each location are almost entirely independent, pointing to separate forcing mechanisms.

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