Wind-driven heat fluxes in the surface energy balance over land
Submitter
Williams, Ian N — Iowa State University
Area of research
Surface Properties
Journal Reference
Science
U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) user facility observations were used to quantify wind gusts from secondary circulations that are too small to be realistically captured by weather and climate models. Lidar wind profiles and surface measurements show that secondary circulations are connected to surface wind gusts. Experiments using the DOE E3SM land model revealed that the circulations increase surface heat fluxes in areas where air converges and rises beneath convective clouds.
Impact
Secondary circulations significantly increase surface heat fluxes and alter the surface energy balance over land. Current gust parameterizations do not match the driving processes. The results provide a basis for improving gust parameterizations at kilometer-scale resolutions.
Summary
Doppler lidar and surface observations were combined with DOE E3SM land model experiments, revealing increased surface winds (5 m/s) and heat fluxes (±50 W/m2) in convergent branches of secondary circulations frequently associated with boundary-layer clouds. Larger wind-driven flux responses (up to 150 W/m2) were found along gust fronts. Surface energy balance shifts to accommodate wind-driven fluxes, reducing ground heat conduction and longwave cooling.
(a) Pattern of wind-driven surface heat fluxes in the E3SM land model with 3-km meteorological input. (b) Time-height cross-section of correlations between surface wind gusts and lidar vertical velocity for normalized time lags (updrafts lead to positive surface wind perturbations by a quarter cycle). Images from journal.