The aggregate description of semi-arid vegetation with precipitation-generated soil moisture heterogeneity

Abstract. Meteorological measurements in the Walnut Gulch catchment in Arizona were used to synthesize a distributed, hourly-average time series of data across a 26.9 by 12.5 km area with a grid resolution of 480 m for a continuous 18-month period which included two seasons of monsoonal rainfall. Coupled surface-atmosphere model runs established the acceptability (for modelling purposes) of assuming uniformity in all meteorological variables other than rainfall. Rainfall was interpolated onto the grid from an array of 82 recording rain gauges. These meteorological data were used as forcing variables for an equivalent array of stand-alone Biosphere-Atmosphere Transfer Scheme (BATS) models to describe the evolution of soil moisture and surface energy fluxes in response to the prevalent, heterogeneous pattern of convective precipitation. The calculated area-average behaviour was compared with that given by a single aggregate BATS simulation forced with area-average meteorological data. Heterogeneous rainfall gives rise to significant but partly compensating differences in the transpiration and the intercepted rainfall components of total evaporation during rain storms. However, the calculated area-average surface energy fluxes given by the two simulations in rain-free conditions with strong heterogeneity in soil moisture were always close to identical, a result which is independent of whether default or site-specific vegetation and soil parameters were used. Because the spatial variability in soil moisture throughout the catchment has the same order of magnitude as the amount of rain falling in a typical convective storm (commonly 10% of the vegetation's root zone saturation) in a semi-arid environment, non-linearity in the relationship between transpiration and the soil moisture available to the vegetation has limited influence on area-average surface fluxes.

Download Full-text

Impacts of grid resolution on surface energy fluxes simulated with an integrated surface-groundwater flow model

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-12-6437-2015 ◽

2015 ◽

Vol 12 (7) ◽

pp. 6437-6466

Author(s):

P. Shrestha ◽

M. Sulis ◽

C. Simmer ◽

S. Kollet

Keyword(s):

Soil Moisture ◽

Surface Energy ◽

Groundwater Flow ◽

Soil Temperature ◽

System Modeling ◽

Surface Fluxes ◽

Heat Fluxes ◽

Grid Resolution ◽

Energy Fluxes ◽

Surface Energy Fluxes

Abstract. The hydrological component of the Terrestrial System Modeling Platform (TerrSysMP) which includes integrated surface-groundwater flow, was used to investigate the grid resolution dependence of simulated soil moisture, soil temperature, and surface energy fluxes over a sub-catchment of the Rur, Germany. The investigation was motivated by the recent developments of new earth system models, which include 3-D physically based groundwater models for the coupling of land–atmosphere interaction and subsurface hydrodynamics. Our findings suggest that for grid resolutions between 100 and 1000 m, the non-local controls of soil moisture are highly grid resolution dependent. Local vegetation, however, strongly modulates the scaling behavior especially for surface fluxes and soil temperature, which depends on the radiative transfer property of the canopy. This study also shows that for grid-resolutions above a few 100 m, the variation of spatial and temporal pattern of sensible and latent heat fluxes may significantly affect the resulting atmospheric mesoscale circulation and boundary layer evolution in coupled runs.

Download Full-text

Impacts of grid resolution on surface energy fluxes simulated with an integrated surface-groundwater flow model

Hydrology and Earth System Sciences ◽

10.5194/hess-19-4317-2015 ◽

2015 ◽

Vol 19 (10) ◽

pp. 4317-4326 ◽

Cited By ~ 18

Author(s):

P. Shrestha ◽

M. Sulis ◽

C. Simmer ◽

S. Kollet

Keyword(s):

Soil Moisture ◽

Surface Energy ◽

Groundwater Flow ◽

Soil Temperature ◽

Surface Fluxes ◽

Heat Fluxes ◽

Grid Resolution ◽

Energy Fluxes ◽

Spatial And Temporal Patterns ◽

Surface Energy Fluxes

Abstract. The hydrological component of the Terrestrial Systems Modeling Platform (TerrSysMP), which includes integrated surface-groundwater flow, was used to investigate the grid resolution dependence of simulated soil moisture, soil temperature, and surface energy fluxes over a sub-catchment of the Rur, Germany. The investigation was motivated by the recent developments of new earth system models, which include 3-D physically based groundwater models for the coupling of land–atmosphere interaction and subsurface hydrodynamics. Our findings suggest that for grid resolutions between 100 and 1000 m, the non-local controls of soil moisture are highly grid resolution dependent. Local vegetation, however, strongly modulates the scaling behavior, especially for surface fluxes and soil temperature, which depends on the radiative transfer property of the canopy. This study also shows that for grid resolutions above a few 100 m, the variation of spatial and temporal patterns of sensible and latent heat fluxes may significantly affect the resulting atmospheric mesoscale circulation and boundary layer evolution in coupled runs.

Download Full-text

Using a thermal-based two source energy balance model with time-differencing to estimate surface energy fluxes with day–night MODIS observations

Hydrology and Earth System Sciences ◽

10.5194/hess-17-2809-2013 ◽

2013 ◽

Vol 17 (7) ◽

pp. 2809-2825 ◽

Cited By ~ 37

Author(s):

R. Guzinski ◽

M. C. Anderson ◽

W. P. Kustas ◽

H. Nieto ◽

I. Sandholt

Keyword(s):

Energy Balance ◽

Surface Energy ◽

The United States ◽

Surface Fluxes ◽

Diurnal Changes ◽

Energy Fluxes ◽

Surface Energy Fluxes ◽

Vegetation Fraction ◽

Geostationary Satellites ◽

Green Vegetation

Abstract. The Dual Temperature Difference (DTD) model, introduced by Norman et al. (2000), uses a two source energy balance modelling scheme driven by remotely sensed observations of diurnal changes in land surface temperature (LST) to estimate surface energy fluxes. By using a time-differential temperature measurement as input, the approach reduces model sensitivity to errors in absolute temperature retrieval. The original formulation of the DTD required an early morning LST observation (approximately 1 h after sunrise) when surface fluxes are minimal, limiting application to data provided by geostationary satellites at sub-hourly temporal resolution. The DTD model has been applied primarily during the active growth phase of agricultural crops and rangeland vegetation grasses, and has not been rigorously evaluated during senescence or in forested ecosystems. In this paper we present modifications to the DTD model that enable applications using thermal observations from polar orbiting satellites, such as Terra and Aqua, with day and night overpass times over the area of interest. This allows the application of the DTD model in high latitude regions where large viewing angles preclude the use of geostationary satellites, and also exploits the higher spatial resolution provided by polar orbiting satellites. A method for estimating nocturnal surface fluxes and a scheme for estimating the fraction of green vegetation are developed and evaluated. Modification for green vegetation fraction leads to significantly improved estimation of the heat fluxes from the vegetation canopy during senescence and in forests. When the modified DTD model is run with LST measurements acquired with the Moderate Resolution Imaging Spectroradiometer (MODIS) on board the Terra and Aqua satellites, generally satisfactory agreement with field measurements is obtained for a number of ecosystems in Denmark and the United States. Finally, regional maps of energy fluxes are produced for the Danish Hydrological ObsErvatory (HOBE) in western Denmark, indicating realistic patterns based on land use.

Download Full-text

Using a thermal-based two source energy balance model with time-differencing to estimate surface energy fluxes with day-night MODIS observations

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-10-1897-2013 ◽

2013 ◽

Vol 10 (2) ◽

pp. 1897-1941 ◽

Cited By ~ 2

Author(s):

R. Guzinski ◽

M. C. Anderson ◽

W. P. Kustas ◽

H. Nieto ◽

I. Sandholt

Keyword(s):

Energy Balance ◽

Surface Energy ◽

The United States ◽

Surface Fluxes ◽

Diurnal Changes ◽

Energy Fluxes ◽

Surface Energy Fluxes ◽

Vegetation Fraction ◽

Geostationary Satellites ◽

Green Vegetation

Abstract. The Dual Temperature Difference (DTD) model, introduced by Norman et al. (2000), uses a two source energy balance modelling scheme driven by remotely sensed observations of diurnal changes in land surface temperature (LST) to estimate surface energy fluxes. By using a time differential temperature measurement as input, the approach reduces model sensitivity to errors in absolute temperature retrieval. The original formulation of the DTD required an early morning LST observation (approximately 1 h after sunrise) when surface fluxes are minimal, limiting application to data provided by geostationary satellites at sub-hourly temporal resolution. The DTD model has been applied primarily during the active growth phase of agricultural crops and rangeland vegetation grasses, and has not been rigorously evaluated during senescence or in forested ecosystems. In this paper we present modifications to the DTD model that enable applications using thermal observation from polar orbiting satellites, such as Terra and Aqua, with day and night overpass times over the area of interest. This allows the application of the DTD model in high latitude regions where large viewing angles preclude the use of geostationary satellites, and also exploits the higher spatial resolution provided by polar orbiting satellites. A method for estimating nocturnal surface fluxes and a scheme for estimating the fraction of green vegetation are developed and evaluated. Modification for green vegetation fraction leads to significantly improved estimation of the heat fluxes from the vegetation canopy during senescence and in forests. Land-cover based modifications to the Priestley–Taylor scheme, used to estimate transpiration fluxes, are explored based on prior findings for conifer forests. When the modified DTD model is run with LST measurements acquired with the Moderate Resolution Imaging Spectroradiometer (MODIS) on board the Terra and Aqua satellites, generally satisfactory agreement with field measurements is obtained for a number of ecosystems in Denmark and the United States. Finally, regional maps of energy fluxes are produced for the Danish Hydrological ObsErvatory (HOBE) in western Denmark, indicating realistic patterns based on land use.

Download Full-text

Intercomparison of surface energy fluxes, soil moisture, and evapotranspiration from eddy covariance, large-aperture scintillometer, and modeling across three ecosystems in a semiarid climate

Agricultural and Forest Meteorology ◽

10.1016/j.agrformet.2017.08.025 ◽

2018 ◽

Vol 248 ◽

pp. 22-47 ◽

Cited By ~ 18

Author(s):

Prasanth Valayamkunnath ◽

Venkataramana Sridhar ◽

Wenguang Zhao ◽

Richard G. Allen

Keyword(s):

Soil Moisture ◽

Surface Energy ◽

Eddy Covariance ◽

Energy Fluxes ◽

Surface Energy Fluxes ◽

Large Aperture ◽

Large Aperture Scintillometer ◽

Semiarid Climate

Download Full-text

Assessing Intra-Urban Surface Energy Fluxes Using Remotely Sensed ASTER Imagery and Routine Meteorological Data: A Case Study in Indianapolis, U.S.A.

IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing ◽

10.1109/jstars.2013.2281776 ◽

2014 ◽

Vol 7 (10) ◽

pp. 4046-4057 ◽

Cited By ~ 29

Author(s):

Qihao Weng ◽

Xuefei Hu ◽

Dale A. Quattrochi ◽

Hua Liu

Keyword(s):

Surface Energy ◽

Meteorological Data ◽

Remotely Sensed ◽

Urban Surface ◽

Energy Fluxes ◽

Surface Energy Fluxes

Download Full-text

The role of improved soil moisture for the characteristics of surface energy fluxes in the ECMWF reanalyses

10.5194/hess-2017-619 ◽

2017 ◽

Author(s):

Wilhelm May

Keyword(s):

Heat Flux ◽

Soil Moisture ◽

Surface Energy ◽

Moisture Content ◽

Regional Differences ◽

Soil Moisture Content ◽

Sensible Heat Flux ◽

Sensible Heat ◽

Energy Fluxes ◽

Surface Energy Fluxes

Abstract. In this study, the role that more realistic soil moisture has for the characteristics of surface energy fluxes in two sets of reanalyses performed at ECMWF is investigated. These are the standard set of reanalyses ERA-Interim (ERAInt) and the ERA-Interim/Land reanalyses of the land surface conditions (ERAInt/Land). In the latter, the ECMWF's land surface model has been forced with the meteorological fields from ERAInt, including an adjustment of precipitation based on the monthly mean values from the Global Precipitation Climatology Project data set. Adjusting precipitation has a distinct impact on the soil moisture content in the two sets of reanalyses. ERAInt is characterized by a general tendency to underestimate (overestimate) soil moisture in regions with a relatively high (low) soil moisture content. The differences in soil moisture between ERAInt and ERAInt/Land vary only slightly in the course of the year. This is not the case for precipitation, where the differences between the two sets of reanalyses vary markedly between different seasons. The direct impact of the regional differences in precipitation between ERAInt and ERAInt/Land on the corresponding deviations in soil moisture varies considerably by region. One reason is that the regional differences in precipitation vary by season, while the regional differences in soil moisture typically persist throughout the year. Another reason is that the specific nature of the interaction between precipitation and soil moisture diverges between different regions, depending on the climate conditions and on the degree to which the soil is saturated with moisture. The differences in soil moisture between the two sets of reanalyses have notable effects on the characteristics of surface energy fluxes. The nature of these effects differs by region and also by season, that is the coupling between soil moisture and the latent or the sensible heat flux is positive in one region or season, respectively, and negative in another one. In any case, the differences in the soil moisture content typically affect the latent and the sensible heat flux in opposite ways. Increases (decreases) in latent heat flux typically coincide with decreases (increases) in sensible heat flux. By this, the differences in soil moisture have a substantial impact on the partitioning of latent and sensible heat flux. The effect of the soil moisture differences on the evaporative fraction, for instance, is mainly governed by the impact on the latent heat flux because of the opposite effects on latent and sensible heat fluxes and, hence, only a weak impact on the total surface energy flux. The effect on the Bowen ratio, on the other hand, is for the most part controlled by the impact on the sensible heat flux, with higher (lower) values of the Bowen ratio in regions with increased (decreased) sensible heat flux.

Download Full-text

Comparing inferred surface energy fluxes with observation-based flux estimates over the ocean

10.5194/egusphere-egu21-7514 ◽

2021 ◽

Author(s):

Johannes Mayer ◽

Michael Mayer ◽

Leopold Haimberger

Keyword(s):

Surface Energy ◽

Energy Budget ◽

North Atlantic ◽

Surface Flux ◽

Surface Fluxes ◽

Energy Fluxes ◽

Surface Energy Fluxes ◽

The North ◽

The North Atlantic ◽

Good Agreement

We combine atmospheric energy transports from ECMWF's latest reanalysis dataset ERA5 with observation-based TOA fluxes from CERES-EBAF to infer net surface energy fluxes (FSinf) for the period 1985-2018. We present an extensive comparison at scales ranging from global to local using 15 in-situ buoy measurements, parameterized surface fluxes from ERA5, and previous evaluations of FSinf using ERA-Interim. We also combine FSinf with various estimates of the ocean heat content tendency (OHCT) and observation-based oceanic heat transports from RAPID and moorings in Fram Strait and Barents Sea Opening to evaluate the oceanic energy budget in the North Atlantic Ocean basin.Our results show that the indirectly estimated FSinf has a 1985-2018 ocean mean of 1.7 W m-2 (see J.Mayer et al. (2021); under review), which is in good agreement with the long-term mean OHCT derived from ocean reanalyses as well as independent surface flux estimates presented in recent literature (e.g., von Schuckmann et al. (2020); https://doi.org/10.5194/essd-12-2013-2020), suggesting an only small global ocean mean bias of FSinf. Moreover, our FSinf product is temporally more stable than parameterized surface fluxes from ERA5 and previous FSinf estimates using ERA-Interim, at least from 2000 onwards. The evaluation of the oceanic energy budget in the North Atlantic shows good agreement between FSinf and observation-based divergence of oceanic heat transports and OHCT such that its residual is on the order of <0.2 PW (~7 W m-2). Even on station-scale, FSinf agrees reasonably well with buoy-based surface flux measurements with a bias of 19.7 W m-2 over all 15 buoys &#160;(compared to 21.7 W m-2 for parameterized surface fluxes), with largest biases in the Indian Ocean. This assessment demonstrates that our inferred surface flux estimate using ERA5 data outperforms parameterized fluxes from the model on all considered spatial scales (global-regional-local) in terms of bias and temporal stability and thus is well-suited for climate studies and model evaluations.&#160;

Download Full-text