Evaluated Crop Evapotranspiration over a Region of Irrigated Orchards with the Improved ACASA–WRF Model

Falk, Matthias; Pyles, R. D.; Ustin, Susan L.; U, K. T. Paw; Xu, Li; Whiting, Michael L.; Sandén, B.; Brown, Patrick H.

doi:10.1175/jhm-d-12-0183.1

Cited by 24 publications

(17 citation statements)

References 54 publications

(48 reference statements)

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“…This may seem lower than expected, given that these fields are intensively managed. However, farmers need to have spacing between plants to cultivate the fields, so moderate values of LAI (less than 3) are common for key perennial crops like grapes (Johnson et al, ; Kustas et al, ), walnuts (Patton et al, ), and almonds (Falk et al, ; Zarate‐Valdez et al, ). Furthermore, the data in Figure resemble spatial patterns and magnitudes of LAI derived from an independent study based on the simple ratio and the Advanced Very High Resolution Radiometer (Nikolov & Zeller, ).…”

Section: Resultsmentioning

confidence: 99%

How Much Water Is Evaporated Across California? A Multiyear Assessment Using a Biophysical Model Forced With Satellite Remote Sensing Data

Baldocchi

Dralle

Jiang

et al. 2019

Water Resources Research

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California is expected to experience great spatial/temporal variations evaporation. These variations arise from strong north‐south, east‐west gradients in rainfall and vegetation, strong interannual variability in rainfall (±30%) and strong seasonal variability in the supply and demand for moisture. We used the Breathing Earth System Simulator to evaluate the rates and sums of evaporation across California, over the 2001–2017 period. Breathing Earth System Simulator is a bottom‐up, biophysical model that couples subroutines that calculate the surface energy balance, photosynthesis, and stomatal conductance. The model is forced with high‐resolution remote sensing data (1 km).The questions we address are as follows: How much water is evaporated across the natural and managed ecosystems of California? How much does evaporation vary during the booms and busts in annual rainfall? and Is evaporation increasing with time due to a warming climate? Mean annual evaporation, averaged over the 2001–2017 period, was relatively steady (393 ± 21 mm/year) given the high interannual variation in precipitation (519 ± 140 mm/year). No significant trend in evaporation at the statewide level was detected over this time period, despite a background of a warming climate. Irrigated agricultural crops and orchards, at 1‐km scale, use less water than inferred estimates for individual fields. This leaves the potential for sharing water, a scarce resource, more equitably among competing stakeholders, for example, farms, fish, people, and ecosystems.

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Section: Resultsmentioning

confidence: 99%

How Much Water Is Evaporated Across California? A Multiyear Assessment Using a Biophysical Model Forced With Satellite Remote Sensing Data

Baldocchi

Dralle

Jiang

et al. 2019

Water Resources Research

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“…This system includes a net radiometer, sonic anemometer, two thermocouples, and soil heat flux plates, which were assembled to measure components of surface energy fluxes [38]. A REBS Inc. Q7.2 net radiometer was mounted at about 10 m height on the flux tower to measure net radiation (R n ).…”

Section: Actual Evapotranspiration Measurementsmentioning

confidence: 99%

Evapotranspiration Estimate over an Almond Orchard Using Landsat Satellite Observations

Jin

Kandelous

et al. 2017

Remote Sensing

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California growers face challenges with water shortages and there is a strong need to use the least amount of water while optimizing yield. Timely information on evapotranspiration (ET), a dominant component of crop consumptive water use, is critical for growers to tailor irrigation management based on in-field spatial variability and in-season variations. We evaluated the performance of a remote sensing-based approach, Mapping Evapotranspiration at high Resolution with Internalized Calibration (METRIC), in mapping ET over an almond orchard in California, driven by Landsat satellite observations. Reference ET from a network of weather stations over well-watered grass (ET o ) was used for the internal calibration and for deriving ET at daily and extended time period, instead of alfalfa based reference evapotranspiration (ET r ). Our study showed that METRIC daily ET estimates during Landsat overpass dates agreed well with the field measurements. During 2009-2012, a root mean square error (RMSE) of 0.53 mm/day and a coefficient of determination (R 2 ) of 0.87 were found between METRIC versus observed daily ET. Monthly ET estimates had a higher accuracy, with a RMSE of 12.08 mm/month, a R 2 of 0.90, and a relatively small relative mean difference (RMD) of 9.68% during 2009-2012 growing seasons. Net radiation and Normalized Difference Vegetation Index (NDVI) from remote sensing observations were highly correlated with spatial and temporal ET estimates. An empirical model was developed to estimate daily ET using NDVI, net radiation (R n ), and vapor pressure deficit (VPD). The validation showed that the accuracy of this easy-to-use empirical method was slightly lower than that of METRIC but still reasonable, with a RMSE of 0.71 mm/day when compared to ground measurements. The remote sensing based ET estimate will support a variety of State and local interests in water use and irrigation management, for both planning and regulatory/compliance purposes, and it provides the farmers observation-based guidance for site-specific and time-sensitive irrigation management.

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“…Utilizing this polynomial allows for the calculation of the temperatures of these components without making substantial errors in the case of significant deviations from the ambient temperature. The model was considerably updated by the University of California, Davis (Pyles et al, 2000(Pyles et al, , 2003 and is still in use (Falk et al, 2014). For this study, the ACASA model was adapted from a version of April 2013.…”

Section: The Acasa Modelmentioning

confidence: 99%

“…In order to enable a preferably exact allocation of the energy to sensible and latent heat fluxes, a leaf energy balance equation has to be solved. Plant physiological feedback to micro-environmental conditions is incorporated by the approaches of Leuning (1990) and Collatz et al (1991) to the Ball-Berry stomatal conductance combined with photosynthetic rates calculated after an equation of Farquhar and Caemmerer (1982), whereby coupling follows the standards of Su and Paw U (1996). ACASA also includes canopy heat storage, which is mainly important for tall vegetation, and canopy interception of precipitation.…”

Section: The Acasa Modelmentioning

confidence: 99%

Footprint-weighted tile approach for a spruce forest and a nearby patchy clearing using the ACASA model

Gatzsche

Babel

Pyles³

et al. 2018

Biogeosciences

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Abstract. The ACASA (Advanced Canopy-AtmosphereSoil Algorithm) model, with a higher-order closure for tall vegetation, has already been successfully tested and validated for homogeneous spruce forests. The aim of this paper is to test the model using a footprint-weighted tile approach for a clearing with a heterogeneous structure of the underlying surface. The comparison with flux data shows a good agreement with a footprint-aggregated tile approach of the model. However, the results of a comparison with a tile approach on the basis of the mean land use classification of the clearing is not significantly different. It is assumed that the footprint model is not accurate enough to separate smallscale heterogeneities. All measured fluxes are corrected by forcing the energy balance closure of the test data either by maintaining the measured Bowen ratio or by the attribution of the residual depending on the fractions of sensible and latent heat flux to the buoyancy flux. The comparison with the model, in which the energy balance is closed, shows that the buoyancy correction for Bowen ratios > 1.5 better fits the measured data. For lower Bowen ratios, the correction probably lies between the two methods, but the amount of available data was too small to make a conclusion. With an assumption of similarity between water and carbon dioxide fluxes, no correction of the net ecosystem exchange is necessary for Bowen ratios > 1.5.

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Evaluated Crop Evapotranspiration over a Region of Irrigated Orchards with the Improved ACASA–WRF Model

Cited by 24 publications

References 54 publications

How Much Water Is Evaporated Across California? A Multiyear Assessment Using a Biophysical Model Forced With Satellite Remote Sensing Data

How Much Water Is Evaporated Across California? A Multiyear Assessment Using a Biophysical Model Forced With Satellite Remote Sensing Data

Evapotranspiration Estimate over an Almond Orchard Using Landsat Satellite Observations

Footprint-weighted tile approach for a spruce forest and a nearby patchy clearing using the ACASA model

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