Estimating evapotranspiration over vegetated surfaces based on wet patch patterns

Abstract Evapotranspiration (ET) is a critical component of the hydrological cycle and natural water-energy nexus. The dynamics of soil water content (θ) in the top surface layer, regulated by local climate, predominates the surface energy exchange and ET behavior. In this study, we proposed a novel ET-θ relation using a physically based wet patch radius coupling the near surface turbulent transfer and soil water availability. The model is tested against the dataset from eddy covariance (EC) sites in the AmeriFlux network. The results show that ET rate is supply-driven under low soil moisture conditions since the plant controls the transpiration rate to conserve water due to water stress. While in energy-limited condition, increasing soil moisture will not promote ET rate as it is bounded by the lower atmospheric demand. The proposed method is practically designed to calculate ET using variables readily measured by standard EC towers such as soil moisture and meteorological measurements. The method can also potentially be extended to predict the spatial and physical patterns of ecosystem services under different hydroclimatic conditions.

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Using StorAge Selection functions to quantify ecohydrological controls on the time-variant age of evapotranspiration, soil water, and recharge

10.5194/hess-2018-57 ◽

2018 ◽

Cited By ~ 3

Author(s):

Aaron A. Smith ◽

Doerthe Tetzlaff ◽

Chris Soulsby

Keyword(s):

Soil Moisture ◽

Surface Water ◽

Soil Water ◽

Water Uptake ◽

Root Water Uptake ◽

Soil Evaporation ◽

Root Uptake ◽

Water Fluxes ◽

Near Surface ◽

Moisture Conditions

Abstract. Quantifying ecohydrological controls on soil water availability is essential to understand temporal variations in catchment storage. Soil water is subject to numerous time-variable fluxes (evaporation, root-uptake, and recharge), each with different water ages which in turn affect the age of water in storage. Here, we adapt StorAge Selection (SAS) function theory to investigate water flow in soils and identify soil evaporation and root-water uptake sources from depth. We use this to quantify the effects of soil-vegetation interactions on the inter-relationships between water fluxes, storage, and age. The novel modification of the SAS function framework is tested against empirical data from two contrasting soil-vegetation units in the Scottish Highlands; these are characterised by significant preferential flow, transporting younger water through the soil during high soil moisture conditions. Dominant young water fluxes, along with relatively low rainfall intensities, explain relatively stable soil water ages through time and with depth. Soil evaporation sources were more time-invariant with high preference for near-surface water, independent of soil moisture conditions, and resulting in soil evaporation water ages similar to near-surface soil waters (mean age: 50–65 days). Sources of root-water uptake were more variable: preferential near-surface water uptake occurred in wet conditions, with a deeper root-uptake source during dry soil conditions, which resulted in more variable water ages of transpiration (mean age: 56–79 days). The simple model structure provides a parsimonious means of constraining the water age of multiple fluxes from the upper part of the critical zone during time-varying conditions improving our understanding of vegetation influences on catchment scale water fluxes.

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Improvement of evapotranspiration estimates over arid and semi-arid regions with a physically based water stress constraint scheme

10.5194/egusphere-egu2020-12757 ◽

2020 ◽

Author(s):

Kun Zhang ◽

Donghai Zheng ◽

Yunquan Wang ◽

Gaofeng Zhu

Keyword(s):

Soil Moisture ◽

Water Stress ◽

Soil Water ◽

Arid Regions ◽

Bare Soil ◽

Stress Constraint ◽

Near Surface ◽

Soil Water Stress ◽

Physically Based ◽

Semi Arid

<p>In the arid and semi-arid regions, the bare soil evaporation dominates the total evapotranspiration (ET). To date, in most of the process-based ET models, the constraint on the actual evaporation from bare soil due to water stress is either related to an empirical function of near-surface humidity or represented by a water stress factor linked with surface soil moisture. However, the relative humidity (RH) shows a hysteretic effect on the ET event, and the relationship between soil water stress and soil moisture is nonlinear, usually leading to the overestimation of ET in arid and semi-arid regions. In this study, we plan to improve the ET estimates on dry land by implementing a physically-based water stress constraint method, which is developed by parameterizing the Buckingham-Darcy&#8217;s law and yielded an excellent performance with laboratory data. The physically-based water stress constraint scheme is further incorporated into two different ET models (i.e. PT-JPL, MOD16) to generate the global ET estimates, whereby the latest ERA5-land reanalysis data and MODIS NDVI\LAI is adopted as model inputs. We not only validate the simulated ET with available flux observations but also intercompare the performances of different schemes in estimating ET in the arid and semi-arid regions. This study will provide a new way to characterize the regional soil water stress on the ET estimates especially in the arid and semi-arid conditions.</p>

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Summer temperature response to extreme soil water conditions in the Mediterranean transitional climate regime

Climate Dynamics ◽

10.1007/s00382-021-05815-8 ◽

2021 ◽

Author(s):

Stefano Materia ◽

Constantin Ardilouze ◽

Chloé Prodhomme ◽

Markus G. Donat ◽

Marianna Benassi ◽

...

Keyword(s):

Boundary Layer ◽

Soil Moisture ◽

Soil Water ◽

Land Surface ◽

Heat Waves ◽

Climate Regime ◽

Seasonal Forecasts ◽

Near Surface ◽

Surface Temperatures ◽

The Mediterranean

AbstractLand surface and atmosphere are interlocked by the hydrological and energy cycles and the effects of soil water-air coupling can modulate near-surface temperatures. In this work, three paired experiments were designed to evaluate impacts of different soil moisture initial and boundary conditions on summer temperatures in the Mediterranean transitional climate regime region. In this area, evapotranspiration is not limited by solar radiation, rather by soil moisture, which therefore controls the boundary layer variability. Extremely dry, extremely wet and averagely humid ground conditions are imposed to two global climate models at the beginning of the warm and dry season. Then, sensitivity experiments, where atmosphere is alternatively interactive with and forced by land surface, are launched. The initial soil state largely affects summer near-surface temperatures: dry soils contribute to warm the lower atmosphere and exacerbate heat extremes, while wet terrains suppress thermal peaks, and both effects last for several months. Land-atmosphere coupling proves to be a fundamental ingredient to modulate the boundary layer state, through the partition between latent and sensible heat fluxes. In the coupled runs, early season heat waves are sustained by interactive dry soils, which respond to hot weather conditions with increased evaporative demand, resulting in longer-lasting extreme temperatures. On the other hand, when wet conditions are prescribed across the season, the occurrence of hot days is suppressed. The land surface prescribed by climatological precipitation forcing causes a temperature drop throughout the months, due to sustained evaporation of surface soil water. Results have implications for seasonal forecasts on both rain-fed and irrigated continental regions in transitional climate zones.

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Quantifying the effect of post-wildfire soil water repellency on runoff

10.5194/ismc2021-102 ◽

2021 ◽

Author(s):

Rose Shillito ◽

Markus Berli ◽

Ian Floyd ◽

Li Chen ◽

Teamrat Ghezzehei

Keyword(s):

Soil Water ◽

Water Repellency ◽

Silica Sand ◽

Watershed Model ◽

Soil Water Repellency ◽

Physically Based Model ◽

San Gabriel Mountains ◽

Physically Based ◽

Dry Soil ◽

Moisture Conditions

<p>Several factors are believed to contribute to post-wildfire flooding and debris flows. One contributing factor&#8212;the occurrence of post-wildfire soil water repellency&#8212;lacks a quantitative mechanism to incorporate the effects in physically-based runoff models. For this study, a physically-based model was developed linking the contact angle (degree of water repellency) to sorptivity. The model was verified in laboratory experiments using a silica sand proxy. The effects of water repellency on infiltration were illustrated. Further, the effect of water repellency on runoff was simulated using the AGWA-KINEROS2 watershed model with data from rainfall following the 2009 Station fire in the San Gabriel Mountains of southern California, USA. Results show water repellency has a quantifiable effect on runoff production, an effect enhanced by the dry soil moisture conditions common after wildfires.</p>

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Effects of Air Temperature and Precipitation on Soil Moisture on the Qinghai-Tibet Plateau during the 2015 Growing Season

Advances in Meteorology ◽

10.1155/2020/4918945 ◽

2020 ◽

Vol 2020 ◽

pp. 1-10

Author(s):

Qingyan Xie ◽

Jianping Li ◽

Yufei Zhao

Keyword(s):

Soil Moisture ◽

Air Temperature ◽

Hydrological Cycle ◽

Critical Role ◽

Growing Season ◽

Tibet Plateau ◽

Ecosystem Stability ◽

Near Surface ◽

Temperature And Precipitation ◽

Qinghai Tibet Plateau

The Qinghai-Tibet Plateau (QTP) holds massive freshwater resources and is one of the most active regions in the world with respect to the hydrological cycle. Soil moisture (SM) plays a critical role in hydrological processes and is important for plant growth and ecosystem stability. To investigate the relationship between climatic factors (air temperature and precipitation) and SM during the growing season in various climate zones on the QTP, data from three observational stations were analyzed. The results showed that the daily average (Tave) and minimum air temperatures (Tmin) significantly influenced SM levels at all depths analyzed (i.e., 10, 20, 30, 40, and 50 cm deep) at the three stations, and Tmin had a stronger effect on SM than did Tave. However, the daily maximum air temperature (Tmax) generally had little effect on SM, although it had showed some effects on SM in the middle and deeper layers at the Jiali station. Precipitation was an important factor that significantly influenced the SM at all depths at the three stations, but the influence on SM in the middle and deep layers lagged the direct effect on near-surface SM by 5–7 days. These results suggest that environment characterized by lower temperatures and higher precipitation may promote SM conservation during the growing season and in turn support ecosystem stability on the QTP.

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Diagnosing Land–Atmosphere Interaction from a Regional Climate Model Simulation over West Africa

Journal of Hydrometeorology ◽

10.1175/2009jhm1173.1 ◽

2010 ◽

Vol 11 (2) ◽

pp. 467-481 ◽

Cited By ~ 39

Author(s):

Bart J. J. M. van den Hurk ◽

Erik van Meijgaard

Keyword(s):

Soil Moisture ◽

Regional Climate Model ◽

Climate Model ◽

Hydrological Cycle ◽

Regional Climate ◽

West African ◽

The West ◽

Near Surface ◽

Monsoon Area ◽

Atmosphere Interaction

Abstract Land–atmosphere interaction at climatological time scales in a large area that includes the West African Sahel has been explicitly explored in a regional climate model (RegCM) simulation using a range of diagnostics. First, areas and seasons of strong land–atmosphere interaction were diagnosed from the requirement of a combined significant correlation between soil moisture, evaporation, and the recycling ratio. The northern edge of the West African monsoon area during June–August (JJA) and an area just north of the equator (Central African Republic) during March–May (MAM) were identified. Further analysis in these regions focused on the seasonal cycle of the lifting condensation level (LCL) and the convective triggering potential (CTP), and the sensitivity of CTP and near-surface dewpoint depressions HIlow to anomalous soil moisture. From these analyses, it is apparent that atmospheric mechanisms impose a strong constraint on the effect of soil moisture on the regional hydrological cycle.

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Modeling the Effects of Lakes in the Tibetan Plateau on Diurnal Variations of Regional Climate and Their Seasonality

Journal of Hydrometeorology ◽

10.1175/jhm-d-20-0091.1 ◽

2020 ◽

Vol 21 (11) ◽

pp. 2523-2536

Author(s):

Lingjing Zhu ◽

Jiming Jin ◽

Yimin Liu

Keyword(s):

Tibetan Plateau ◽

Regional Climate ◽

Wrf Model ◽

Surface Air Temperature ◽

Diurnal Variations ◽

The Tibetan Plateau ◽

Near Surface ◽

Local Climate ◽

Lake Model ◽

Physically Based

AbstractIn this study, we investigated the effects of lakes in the Tibetan Plateau (TP) on diurnal variations of local climate and their seasonal changes by using the Weather Research and Forecasting (WRF) Model coupled with a one-dimensional physically based lake model. We conducted WRF simulations for the TP over 2000–10, and the model showed excellent performance in simulating near-surface air temperature, precipitation, lake surface temperature, and lake-region precipitation when compared to observations. We carried out additional WRF simulations where all the TP lakes were replaced with the nearest land-use types. The differences between these two sets of simulations were analyzed to quantify the effects of the TP lakes on the local climate. Our results indicate that the strongest lake-induced cooling occurred during the spring daytime, while the most significant warming occurred during the fall nighttime. The cooling and warming effects of the lakes further inhibited precipitation during summer afternoons and evenings and motivated it during fall early mornings, respectively. This study lays a solid foundation for further exploration of the role of TP lakes in climate systems at different time scales.

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EVAPOTRANSPIRATION AND LEAF WATER STATUS OF ALFALFA GROWING UNDER ADVECTIVE CONDITIONS

Canadian Journal of Plant Science ◽

10.4141/cjps81-083 ◽

1981 ◽

Vol 61 (3) ◽

pp. 601-607 ◽

Cited By ~ 4

Author(s):

R. J. WILLIAMS ◽

DARRYL G. STOUT

Keyword(s):

Soil Moisture ◽

Potential Evapotranspiration ◽

Water Status ◽

Bowen Ratio ◽

High Rate ◽

Leaf Water Status ◽

Leaf Osmotic Potential ◽

Physically Based ◽

Environmental Demand ◽

Moisture Conditions

Actual evapotranspiration (LE) and leaf osmotic potential (ψs) were measured on a Medicago sativa L. (alfalfa, cv. Thor) field in interior British Columbia that is subject to advection. During periods of advection, LE, measured by the Bowen ratio energy balance method, exceeded both the net radiation (Q*) and the potential evapotranspiration (PE) calculated by the physically based formula of Priestley and Taylor (1972). During advection, Q* was a better approximation of LE than was PE. During nonadvection periods, LE was approximately equal to PE. It was found that the Jury and Tanner (1975) modification of PE for advective conditions gave favorable results during periods immediately following irrigation. Diurnal measurements revealed that leaf ψs reached a minimum by about 1200 h and then remained constant even though LE continued at a high rate. Leaf ψs measured at 0800 h reflected soil moisture conditions, and leaf ψs measured at 1400 h reflected both soil moisture conditions and environmental demand.

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Effects of soil‐moisture content on shallow‐seismic data

Geophysics ◽

10.1190/1.1444437 ◽

1998 ◽

Vol 63 (4) ◽

pp. 1357-1362 ◽

Cited By ~ 25

Author(s):

Robert D. Jefferson ◽

Don W. Steeples ◽

Ross A. Black ◽

Tim Carr

Keyword(s):

Soil Moisture ◽

Moisture Content ◽

Seismic Data ◽

Soil Moisture Content ◽

Soil Conditions ◽

Near Surface ◽

Surface Moisture ◽

Shallow Seismic ◽

Unconsolidated Material ◽

Moisture Conditions

Repeated shallow‐seismic experiments were conducted at a site on days with different near‐surface moisture conditions in unconsolidated material. Experimental field parameters remained constant to ensure comparability of results. Variations in the seismic data are attributed to the changes in soil‐moisture content of the unconsolidated material. Higher amplitudes of reflections and refractions were obtained under wetter near‐surface conditions. An increase in amplitude of 21 dB in the 100–300 Hz frequency range was observed when the moisture content increased from 18% to 36% in the upper 0.15 m (0.5 ft) of the subsurface. In the time‐domain records, highly saturated soil conditions caused large‐amplitude ringy wavelets that interfered with and degraded the appearance of some of the reflection information in the raw field data. This may indicate that an intermediate near‐surface moisture content is most conducive to the recording of high‐quality shallow‐seismic reflection data at this site. This study illustrates the drastic changes that can occur in shallow‐seismic data due to variations in near‐surface moisture conditions. These conditions may need to be considered to optimize the acquisition timing and parameters prior to collection of data.

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SOIL pH AND MOISTURE EFFECTS ON VEGETABLE AMARANTH PRODUCTION

HortScience ◽

10.21273/hortsci.27.6.647e ◽

1992 ◽

Vol 27 (6) ◽

pp. 647e-647

Author(s):

Bharat P. Singh ◽

Wayne F. Whitehead

Keyword(s):

Soil Moisture ◽

Soil Water ◽

Soil Ph ◽

Water Levels ◽

Plant Parts ◽

Moisture Effects ◽

Wide Range ◽

Significant Difference ◽

Plant Grown ◽

Moisture Conditions

The effect of soil moisture and pH levels on the vegetative growth of amaranth were studied in the greenhouse during 1990-91. Three soil pH levels: 4.5, 5.3, and 6.4 and four soil water levels: 3, 6, 12 and 18% (w/w) comprised the treatments of the two studies. The plants grown in pH 6.4 were significantly taller and had greater leaf area than plants grown in pH 5.3 or 4.7 soil. There was a significant decrease in all above ground plant parts with each increase in soil acidity. The top fresh weight of plants grown in 5.6 and 4.7 pH soil were 27% and 73% lower, respectively, than plant grown in 6.4 pH soil. Plant grown in 3% soil water had significantly lower leaf, stem and root fresh weights than other soil water levels. There was no significant difference in the performance of plants grown in 6, 12 or 18% soil water, suggesting that amaranth plant is adapted to a wide range of soil moisture conditions.

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