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

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.

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

Hydrology and Earth System Sciences ◽

10.5194/hess-14-2193-2010 ◽

2010 ◽

Vol 14 (11) ◽

pp. 2193-2205 ◽

Cited By ~ 34

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.

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Terrestrial Aridity and Its Response to Greenhouse Warming across CMIP5 Climate Models

Journal of Climate ◽

10.1175/jcli-d-14-00480.1 ◽

2015 ◽

Vol 28 (14) ◽

pp. 5583-5600 ◽

Cited By ~ 76

Author(s):

Jacob Scheff ◽

Dargan M. W. Frierson

Keyword(s):

Land Surface ◽

Large Scale ◽

Climate Models ◽

Potential Evapotranspiration ◽

Global Climate ◽

Aridity Index ◽

Global Climate Models ◽

Greenhouse Warming ◽

Dimensionless Ratio ◽

The Tropics

Abstract The aridity of a terrestrial climate is often quantified using the dimensionless ratio of annual precipitation (P) to annual potential evapotranspiration (PET). In this study, the climatological patterns and greenhouse warming responses of terrestrial P, Penman–Monteith PET, and are compared among 16 modern global climate models. The large-scale climatological values and implied biome types often disagree widely among models, with large systematic differences from observational estimates. In addition, the PET climatologies often differ by several tens of percent when computed using monthly versus 3-hourly inputs. With greenhouse warming, land P does not systematically increase or decrease, except at high latitudes. Therefore, because of moderate, ubiquitous PET increases, decreases (drying) are much more widespread than increases (wetting) in the tropics, subtropics, and midlatitudes in most models, confirming and expanding on earlier findings. The PET increases are also somewhat sensitive to the time resolution of the inputs, although not as systematically as for the PET climatologies. The changes in the balance between P and PET are also quantified using an alternative aridity index, the ratio , which has a one-to-one but nonlinear correspondence with . It is argued that the magnitudes of changes are more uniformly relevant than the magnitudes of changes, which tend to be much higher in wetter regions. The ratio and its changes are also found to be excellent statistical predictors of the land surface evaporative fraction and its changes.

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

10.5194/egusphere-egu2020-6066 ◽

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

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 (ET0) 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 &#8220;leakage&#8221; becomes protected from surface evaporation and may support vegetation or inter-annual storage. Focusing on arid regions (aridity index P/ET0< 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 &#8220;leakage&#8221;. 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.

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Snakebite Envenoming Diagnosis and Diagnostics

Frontiers in Immunology ◽

10.3389/fimmu.2021.661457 ◽

2021 ◽

Vol 12 ◽

Author(s):

Cecilie Knudsen ◽

Jonas A. Jürgensen ◽

Sofie Føns ◽

Aleksander M. Haack ◽

Rasmus U. W. Friis ◽

...

Keyword(s):

Rural Areas ◽

Global Scale ◽

Rapid Diagnostics ◽

Permanent Disability ◽

Ongoing Research ◽

Appropriate Treatment ◽

Syndromic Approach ◽

Potential Benefits ◽

Level Of Experience ◽

The Tropics

Snakebite envenoming is predominantly an occupational disease of the rural tropics, causing death or permanent disability to hundreds of thousands of victims annually. The diagnosis of snakebite envenoming is commonly based on a combination of patient history and a syndromic approach. However, the availability of auxiliary diagnostic tests at the disposal of the clinicians vary from country to country, and the level of experience within snakebite diagnosis and intervention may be quite different for clinicians from different hospitals. As such, achieving timely diagnosis, and thus treatment, is a challenge faced by treating personnel around the globe. For years, much effort has gone into developing novel diagnostics to support diagnosis of snakebite victims, especially in rural areas of the tropics. Gaining access to affordable and rapid diagnostics could potentially facilitate more favorable patient outcomes due to early and appropriate treatment. This review aims to highlight regional differences in epidemiology and clinical snakebite management on a global scale, including an overview of the past and ongoing research efforts within snakebite diagnostics. Finally, the review is rounded off with a discussion on design considerations and potential benefits of novel snakebite diagnostics.

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Global Analysis of Atmospheric Transmissivity Using Cloud Cover, Aridity and Flux Network Datasets

Remote Sensing ◽

10.3390/rs13091716 ◽

2021 ◽

Vol 13 (9) ◽

pp. 1716

Author(s):

Ankur Srivastava ◽

Jose F. Rodriguez ◽

Patricia M. Saco ◽

Nikul Kumari ◽

Omer Yetemen

Keyword(s):

Cloud Cover ◽

Climatic Factors ◽

Global Analysis ◽

Empirical Relationship ◽

Aridity Index ◽

Global Scale ◽

Empirical Models ◽

Coefficient Of Determination ◽

Crop Modeling ◽

Atmospheric Transmissivity

Atmospheric transmissivity (τ) is a critical factor in climatology, which affects surface energy balance, measured at a limited number of meteorological stations worldwide. With the limited availability of meteorological datasets in remote areas across different climatic regions, estimation of τ is becoming a challenging task for adequate hydrological, climatic, and crop modeling studies. The availability of solar radiation data is comparatively less accessible on a global scale than the temperature and precipitation datasets, which makes it necessary to develop methods to estimate τ. Most of the previous studies provided region specific datasets of τ, which usually provide local assessments. Hence, there is a necessity to give the empirical models for τ estimation on a global scale that can be easily assessed. This study presents the analysis of the τ relationship with varying geographic features and climatic factors like latitude, aridity index, cloud cover, precipitation, temperature, diurnal temperature range, and elevation. In addition to these factors, the applicability of these relationships was evaluated for different climate types. Thus, empirical models have been proposed for each climate type to estimate τ by using the most effective factors such as cloud cover and aridity index. The cloud cover is an important yet often overlooked factor that can be used to determine the global atmospheric transmissivity. The empirical relationship and statistical indicator provided the best performance in equatorial climates as the coefficient of determination (r2) was 0.88 relatively higher than the warm temperate (r2 = 0.74) and arid regions (r2 = 0.46). According to the results, it is believed that the analysis presented in this work is applicable for estimating the τ in different ecosystems across the globe.

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An Empirical Study of the Relationship between Seasonal Precipitation and Thermodynamic Environment in Puerto Rico

Weather and Forecasting ◽

10.1175/waf-d-18-0127.1 ◽

2019 ◽

Vol 34 (2) ◽

pp. 277-288 ◽

Cited By ~ 2

Author(s):

Paul W. Miller ◽

Thomas L. Mote ◽

Craig A. Ramseyer

Keyword(s):

Puerto Rico ◽

Annual Rainfall ◽

Seasonal Precipitation ◽

Surface Precipitation ◽

Precipitation Forecasting ◽

Caribbean Islands ◽

K Index ◽

Groundwater Reserves ◽

The Tropics ◽

The Relationship

Abstract With limited groundwater reserves and few reservoirs, Caribbean islands such as Puerto Rico are largely dependent on regular rainfall to meet societal and ecological water needs. Thus, the ability to anticipate seasonal rainfall shortages, such as the 2015 drought, is particularly important, yet few reliable tools exist for this purpose. Consequently, interpolated surface precipitation observations from the Daymet archive are summarized on daily, annual, and seasonal time scales and compared to the host thermodynamic environment as characterized by the Gálvez–Davison index (GDI), a convective potential parameter designed specifically for the tropics. Complementing the Daymet precipitation totals, ≥1.1 million WSR-88D volume scans between 2002 and 2016 were analyzed for echo tops ≥ 10 000 ft (~3 km) to establish a radar-inferred precipitation activity database for Puerto Rico. The 15-yr record reveals that the GDI outperforms several midlatitude-centric thermodynamic indices, explaining roughly 25% of daily 3-km echo top (ET) activity during each of Puerto Rico’s primary seasons. In contrast, neither mean-layer CAPE, the K index, nor total totals explain more than 11% during any season. When aggregated to the seasonal level, the GDI strongly relates to 3-km ET (R2 = 0.65) and Daymet precipitation totals (R2 = 0.82) during the early rainfall season (ERS; April–July), with correlations weaker outside of this period. The 4-month ERS explains 51% (41%) of the variability to Puerto Rico’s annual rainfall during exceptionally wet (dry) years. These findings are valuable for climate downscaling studies predicting Puerto Rico’s hydroclimate in future atmospheric states, and they could potentially be adapted for operational seasonal precipitation forecasting.

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Rising ecosystem water demand exacerbates the lengthening of tropical dry seasons

10.21203/rs.3.rs-218770/v1 ◽

2021 ◽

Author(s):

Hao Xu ◽

Xu Lian ◽

Ingrid Slette ◽

Hui Yang ◽

Yuan Zhang ◽

...

Keyword(s):

Water Demand ◽

Potential Evapotranspiration ◽

Central Africa ◽

Dry Season ◽

Land Area ◽

Key Factor ◽

Dry Seasons ◽

The Tropics ◽

Factor Governing

Abstract The timing and length of the dry season is a key factor governing ecosystem productivity and the carbon cycle of the tropics. Mounting evidence has suggested a lengthening of the dry season with ongoing climate change. However, this conclusion is largely based on changes in precipitation (P) compared to its long-term average (P ̅) and lacks consideration of the simultaneous changes in ecosystem water demand (measured by potential evapotranspiration, Ep, or actual evapotranspiration, E). Using several long-term (1979-2018) observational datasets, we compared changes in tropical dry season length (DSL) and timing (dry season arrival, DSA, and dry season end, DSE) among three common metrics used to define the dry season: P < P ̅, P < Ep, and P < E. We found that all three definitions show that dry seasons have lengthened in much of the tropics since 1979. Among the three definitions, P < E estimates the largest fraction (49.0%) of tropical land area likely experiencing longer dry seasons, followed by P < Ep (41.4%) and P 120 days) among the three definitions occurred in the most arid and the most humid regions of the tropics. All definitions and datasets consistently showed longer dry seasons in southern Amazon (due to delayed DSE) and central Africa (due to both earlier DSA and delayed DSE). However, definitions that account for changing water demand estimated longer DSL extension over those two regions. These results indicate that warming-enhanced evapotranspiration exacerbates dry season lengthening and ecosystem water deficit. Thus, it is necessity to account for the evolving water demand of tropical ecosystems when characterizing changes in seasonal dry periods and ecosystem water deficits in an increasingly warmer and drier climate.

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Climate and land use change impacts on water resources in Sardinia (Italy)

10.5194/egusphere-egu21-10894 ◽

2021 ◽

Author(s):

Dario Ruggiu ◽

Salvatore Urru ◽

Roberto Deidda ◽

Francesco Viola

Keyword(s):

Land Use ◽

Water Resources ◽

Land Use Change ◽

Hydrological Cycle ◽

Potential Evapotranspiration ◽

Regional Scale ◽

Annual Runoff ◽

Annual Rainfall ◽

Land Use Scenarios ◽

Near Future

The assessment of climate change and land use modifications effects on hydrological cycle is challenging. We propose an approach based on Budyko theory to investigate the relative importance of natural and anthropogenic drivers on water resources availability. As an example of application, the proposed approach is implemented in the island of Sardinia (Italy), which is affected by important processes of both climate and land use modifications. In details, the proposed methodology assumes the Fu&#8217;s equation to describe the mechanisms of water partitioning at regional scale and uses the probability distributions of annual runoff (Q) in a closed form. The latter is parametrized by considering simple long-term climatic info (namely first orders statistics of annual rainfall and potential evapotranspiration) and land use properties of basins.In order to investigate the possible near future water availability of Sardinia, several climate and land use scenarios have been considered, referring to 2006-2050 and 2051-2100 periods. Climate scenarios have been generated considering fourteen bias corrected outputs of climatic models from EUROCORDEX&#8217;s project (RCP 8.5), while three land use scenarios have been created following the last century tendencies.Results show that the distribution of annual runoff in Sardinia could be significantly affected by both climate and land use change. The near future distribution of Q generally displayed a decrease in mean and variance compared to the baseline. &#160;&#160;The reduction of&#160; Q is more critical moving from 2006-2050 to 2051-2100 period, according with climatic trends, namely due to the reduction of annual rainfall and the increase of potential evapotranspiration. The effect of LU change on Q distribution is weaker than the climatic one, but not negligible.

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Predicting photosynthesis and transpiration responses to ozone: decoupling modeled photosynthesis and stomatal conductance

Biogeosciences ◽

10.5194/bg-9-3113-2012 ◽

2012 ◽

Vol 9 (8) ◽

pp. 3113-3130 ◽

Cited By ~ 39

Author(s):

D. Lombardozzi ◽

S. Levis ◽

G. Bonan ◽

J. P. Sparks

Keyword(s):

Carbon Dioxide ◽

Stomatal Conductance ◽

Primary Productivity ◽

Environmental Conditions ◽

Water Exchange ◽

Global Scale ◽

Community Land Model ◽

Climate Regulation ◽

The Tropics ◽

Tulip Poplar

Abstract. Plants exchange greenhouse gases carbon dioxide and water with the atmosphere through the processes of photosynthesis and transpiration, making them essential in climate regulation. Carbon dioxide and water exchange are typically coupled through the control of stomatal conductance, and the parameterization in many models often predict conductance based on photosynthesis values. Some environmental conditions, like exposure to high ozone (O3) concentrations, alter photosynthesis independent of stomatal conductance, so models that couple these processes cannot accurately predict both. The goals of this study were to test direct and indirect photosynthesis and stomatal conductance modifications based on O3 damage to tulip poplar (Liriodendron tulipifera) in a coupled Farquhar/Ball-Berry model. The same modifications were then tested in the Community Land Model (CLM) to determine the impacts on gross primary productivity (GPP) and transpiration at a constant O3 concentration of 100 parts per billion (ppb). Modifying the Vcmax parameter and directly modifying stomatal conductance best predicts photosynthesis and stomatal conductance responses to chronic O3 over a range of environmental conditions. On a global scale, directly modifying conductance reduces the effect of O3 on both transpiration and GPP compared to indirectly modifying conductance, particularly in the tropics. The results of this study suggest that independently modifying stomatal conductance can improve the ability of models to predict hydrologic cycling, and therefore improve future climate predictions.

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Persistence and variability of Earth’s inter-hemispheric albedo symmetry in 19 years of CERES EBAF observations

Journal of Climate ◽

10.1175/jcli-d-20-0970.1 ◽

2021 ◽

pp. 1-62

Author(s):

Aiden Jönsson ◽

Frida A.-M. Bender

Keyword(s):

Southern Oscillation ◽

Global Scale ◽

Coupled Models ◽

Radiative Fluxes ◽

Clear Sky ◽

Data Record ◽

Aerosol Sources ◽

Mean Climate ◽

The Tropics ◽

Observational Record

AbstractDespite the unequal partitioning of land and aerosol sources between the hemispheres, Earth’s albedo is observed to be persistently symmetric about the equator. This symmetry is determined by the compensation of clouds to the clear-sky albedo. Here, the variability of this inter-hemispheric albedo symmetry is explored by decomposing observed radiative fluxes in the CERES EBAF satellite data record into components reflected by the atmosphere, clouds, and the surface. We find that the degree of inter-hemispheric albedo symmetry has not changed significantly throughout the observational record. The variability of the inter-hemispheric difference in reflected solar radiation (asymmetry) is strongly determined by tropical and subtropical cloud cover, particularly those related to non-neutral phases of the El Niño-Southern Oscillation (ENSO). As the ENSO is the most significant source of interannual variability in reflected radiation on a global scale, this underscores the inter-hemispheric albedo symmetry as a robust feature of Earth’s current annual mean climate. Comparing this feature in observations with simulations from coupled models reveals that the degree of modeled albedo symmetry is mostly dependent on biases in reflected radiation in the midlatitudes, and that models that overestimate its variability the most have larger biases in reflected radiation in the tropics. The degree of model albedo symmetry is improved when driven with historical sea surface temperatures, indicating that the degree of symmetry in Earth’s albedo is dependent on the representation of cloud responses to coupled ocean-atmosphere processes.

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