Land Atmosphere Feedback Analysis (LAFA)

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The Land-Atmosphere Feedback Experiment (LAFE) deploys several state-of-the-art scanning lidar and remote sensing systems at the US Atmospheric Radiation Measurement (ARM) program Southern Great Plains (SGP) site. These instruments will augment the ARM instrument suite in order to collect a dataset for studying feedback processes between the land-surface and the atmosphere. The novel synergy of remote sensing systems will be applied for simultaneous measurements of land-surface fluxes as well as horizontal and vertical turbulent and transport processes in the atmospheric convective boundary layer (CBL). The impact of spatial inhomogeneities of the soil-vegetation system on land-atmosphere (LA) feedback will be studied using the scanning capability of the instrumentation. The time period of the observations is August 2017, as large differences in surface fluxes between different fields and bare soil can be observed. Due to the high temporal and vertical resolution of this sensor synergy, mean profiles of horizontal wind, temperature, and humidity, their gradients, profiles of their higher-order moments up to the forth order as well as profiles of sensible and latent heat fluxes can be measured from close to the surface to the interfacial layer at the CBL top. Within this Land Atmosphere Feedback (LAFA) proposal, the LAFE data set will be exploited and - for selected LAFE observation periods - the UHOH WRF-NOAHMP model system will be operated in a multi-turbulence parameterization ensemble from the convective permitting scale down to the large eddy simulation (LES) scale. Based on the LAFE observations and the model output, LAFA has two objectives: 1) Determine profiles of higher-order moments of water vapor, temperature, and vertical velocity fluctuations as well as latent heat flux profiles and investigate new similarity relationships for entrainment fluxes and variances. For this purpose, the LAFE results are analyzed with respect to relationships between fluxes, variances, and gradients. 2) Verify LES runs and improve turbulence parameterizations in mesoscale models. The model output will directly be compared with the LAFE data permitting a verification of LES with previously unachieved detail. The results will provide an understanding how far LES can be used for the analysis of turbulent processes and for the derivation of turbulence parameterizations. With respect to the model output on the convection permitting scale, the corresponding parameters and variables of the turbulence parameterizations will be extracted. Different local and non-local turbulence parameterizations available in the WRF physics suite will be verified, their performance will be specified, and improvements will be developed and suggested.Therefore, LAFA will contribute to an advanced process understanding and a more accurate representation of LA exchange and the CBL in the next generation of weather forecast, climate, and earth system models.