Evaporation over a Heterogeneous Land Surface: EVA_GRIPS and the LITFASS-2003 Experiment—An Overview

Beyrich, Frank; Mengelkamp, Heinz-Theo

doi:10.1007/s10546-006-9079-z

Cited by 90 publications

(67 citation statements)

References 56 publications

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“…A total of 13 micrometeorological stations were deployed over this heterogeneous landscape to measure the turbulent fluxes of heat and momentum. More details about the experiment are found in Beyrich and Mengelkamp (2006).…”

Section: Eddy-covariance Measurementsmentioning

confidence: 99%

A Simple Model for the Afternoon and Early Evening Decay of Convective Turbulence Over Different Land Surfaces

Nadeau

Pardyjak

Higgins

et al. 2011

Boundary-Layer Meteorol

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A simple model to study the decay of turbulent kinetic energy (TKE) in the convective surface layer is presented. In this model, the TKE is dependent upon two terms, the turbulent dissipation rate and the surface buoyancy fluctuations. The time evolution of the surface sensible heat flux is modelled based on fitting functions of actual measurements from the LITFASS-2003 field campaign. These fitting functions carry an amplitude and a time scale. With this approach, the sensible heat flux can be estimated without having to solve the entire surface energy balance. The period of interest covers two characteristic transition subperiods involved in the decay of convective boundary-layer turbulence. The first sub-period is the afternoon transition, when the sensible heat flux starts to decrease in response to the reduction in solar radiation. It is typically associated with a decay rate of TKE of approximately t −2 (t is time following the start of the decay) after several convective eddy turnover times. The early evening transition is the second sub-period, typically just before sunset when the surface sensible heat flux becomes negative. This sub-period is characterized by an abrupt decay in TKE associated with the rapid collapse of turbulence. Overall, the results presented show a significant improvement of the modelled TKE decay when compared to the often applied assumption of a sensible heat flux decreasing instantaneously or with a very short forcing time scale. In addition, for atmospheric modelling studies, it is suggested that the afternoon and early evening decay of sensible heat flux be modelled as a complementary error function.

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Section: Eddy-covariance Measurementsmentioning

confidence: 99%

A Simple Model for the Afternoon and Early Evening Decay of Convective Turbulence Over Different Land Surfaces

Nadeau

Pardyjak

Higgins

et al. 2011

Boundary-Layer Meteorol

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“…Patton et al (2005) showed that the strongest SCs occur if the ratio between the heterogeneity length scale and z i is between 4 and 9. Maronga and Raasch (2013), hereafter MR13, reported that the SCs contributed up to 20 % of the total sensible heat flux and up to 39 % of the total latent heat flux in their LES for the complex heterogeneous terrain of the LITFASS-2003 experiment (Beyrich and Mengelkamp 2006). In general, the existence of SCs throughout the bulk of the CBL conflicts with the concept of a blending height.…”

Section: Introductionmentioning

confidence: 99%

Heterogeneity-Induced Heat-Flux Patterns in the Convective Boundary Layer: Can they be Detected from Observations and is There a Blending Height?—A Large-Eddy Simulation Study for the LITFASS-2003 Experiment

Sühring

Raasch

2013

Boundary-Layer Meteorol

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An understanding of how the convective boundary layer (CBL) is mixed under heterogeneous surface forcing is crucial for the interpretation of area-averaged turbulence measurements. To determine the height and degree to which a complex heterogeneous surface affects the CBL, large-eddy simulations (LES) for two days of the LITFASS-2003 experiment representing two different wind regimes were undertaken. Spatially-lagged correlation analysis revealed the turbulent heat fluxes to be dependent on the prescribed surface flux pattern throughout the entire CBL including the entrainment layer. These findings prompted the question of whether signals induced by surface heterogeneity can be measured by airborne systems. To examine this question, an ensemble of virtual flights was conducted using LES, according to Helipod flight measurements made during LITFASS-2003. The resulting ensemble-averaged heat fluxes indicated a clear dependence on the underlying surface up to the top of the CBL. However, a large scatter between the flux measurements in different ensemble runs was observed, which was the result of insufficient sampling of the largest turbulent eddies. The random and systematic errors based on the integral length scale did not indicate such a large scatter. For the given flight leg lengths, at least 10-15 statistically independent flight measurements were necessary to give a significant estimate of heterogeneity-induced signals in the CBL. The need for ensemble averaging suggests that the observed blending of heterogeneity-induced signals in the CBL can be partly attributed to insufficient averaging.

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“…Furthermore, soil water contents, soil temperatures and soil heat fluxes are measured operationally. For details of the investigation programme, instrumentation and measurement accuracy, the reader is referred to Beyrich et al (2002), , Beyrich and Mengelkamp (2006), Beyrich and Adam (2007) and Beyrich and Engelbart (2008). An overview of the measurements that were used in our study is given in Table 1.…”

Section: The Falkenberg Field Site and Micrometeorological Datamentioning

confidence: 99%

Modelling hourly evapotranspiration and soil water content at the grass-covered boundary-layer field site Falkenberg, Germany

Wegehenkel

Beyrich

2014

Hydrological Sciences Journal

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The study analyses a 2-year period of hourly rates of real evapotranspiration (ETr) derived from eddy covariance measurements and soil water contents at depths from 8 to 90 cm, monitored by time domain reflectometry probes at the grass-covered boundary-layer field site Falkenberg of the Lindenberg Meteorological Observatory -Richard-Aßmann-Observatory, operated by the German Meteorological Service (DWD). The ETr rates and soil water contents were compared with the results of a modelling approach consisting of the Penman-Monteith equation and the soil water balance model Hydrus-1D using a noncompensatory and a compensatory root-water uptake model. After optimization of soil hydraulic parameters by inverse modelling, using measured soil water contents as the objective function, simulated and measured model outputs showed good agreement for soil water contents above 90 cm depth and for ETr rates simulated by our modelling approaches using noncompensatory root-water uptake. The application of a compensatory root-water uptake model led to a decrease in the simulation quality for the total investigation period.

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Evaporation over a Heterogeneous Land Surface: EVA_GRIPS and the LITFASS-2003 Experiment—An Overview

Cited by 90 publications

References 56 publications

A Simple Model for the Afternoon and Early Evening Decay of Convective Turbulence Over Different Land Surfaces

A Simple Model for the Afternoon and Early Evening Decay of Convective Turbulence Over Different Land Surfaces

Heterogeneity-Induced Heat-Flux Patterns in the Convective Boundary Layer: Can they be Detected from Observations and is There a Blending Height?—A Large-Eddy Simulation Study for the LITFASS-2003 Experiment

Modelling hourly evapotranspiration and soil water content at the grass-covered boundary-layer field site Falkenberg, Germany

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