A New Research Approach for Observing and Characterizing Land-Atmosphere Feedback
The Southern Great Plains observatory, showing remote sensing instruments in the background used in LAFE and pasture in the foreground. LAFE instruments were deployed in different fields (e.g., soybeans, tall native grasses, shrubs and trees) near this location, and scanning remote sensors measured temperature, humidity, and wind profiles above these fields simultaneously.
May 3, 2018
GSD’s Dave Turner was one of the two principal investigators for the Land-Atmosphere Feedback Experiment (LAFE) that was conducted at the Atmospheric Radiation Measurement Climate Research Facility Southern Great Plains atmospheric observatory in Oklahoma in August 2017. The experiment is described in an early online release of the Bulletin of the American Meteorological Society. LAFE used a novel collection of instruments to make simultaneous measurements from the surface to the top of the boundary layer to study the relationship between surface and atmospheric properties. In particular, LAFE’s observational approach collected a detailed dataset of over a range of different vegetation types, as different crops are hypothesized to impact the boundary layer in various ways.
The atmospheric boundary layer, which extends from the surface of the Earth up to approximately 1 km in height, is a dynamic and highly variable region of the atmosphere. This region of the atmosphere “feels” the surface, and thus characteristics of the surface can greatly impact the evolution of the boundary layer. For example, the solar heating of the surface drives the strong daily evolution of the boundary layer. Similarly, changes in the properties of the boundary layer, such as the concentration of water vapor, can impact the properties of the surface (e.g., a very dry boundary layer leads to more rapid evaporation and thus a drying of the surface). Thus, correctly representing the interactions between the boundary layer and the surface in numerical weather prediction models is critical.
The instrument configuration used during LAFE provided the first comprehensive dataset to evaluate a theory that has been used to predict profiles of wind, temperature, and humidity in numerical models for decades. This theory assumes that the surface is uniform and homogeneous, something that is rarely true in reality due to the heterogeneous nature of different plant types in relatively small patches (compared to model resolution). Furthermore, LAFE observations can serve as a bridge to to evaluate and improve satellite-based planetary boundary layer monitoring. LAFE will also be a blueprint for a new generation of experiments conducted in different climate regions to improve the representation of land-atmosphere feedback in models globally. The initiation of innovative land-atmosphere feedback studies in different climate regions will advance weather forecast, climate, and earth system models worldwide.
As an additional bonus, the LAFE instruments observed the evolution of the surface and boundary layer during the solar eclipse on August 21st. The eclipse mimicked a rapid sunset/sunrise event, and provides a nice complement to the normal sunset/sunrise periods observed during the rest of the month campaign. The rapid temporal evolution of the eclipse will test the parameterizations that attempt to represent the land-atmosphere interactions in a more challenging manner.
LAFE is the first international field campaign dedicated to measurement of all of variables needed to characterize and improve the land-atmosphere feedback. LAFE was supported by the Department of Energy, NOAA, NASA, and the German Federal Ministry for Education and Research. The Atmospheric Radiation Measurement Program Southern Great Plains site is sponsored by the Department of Energy.
For more information contact: Susan Cobb 303-497-5093