An investigation of nocturnal intermittent turbulence during the Cooperative Atmosphere Surface Exchange Study in 1999 (CASES-99) revealed three turbulence regimes at each observation height: 1) regime 1, a weak turbulence regime when the wind speed is less than a threshold value; 2) regime 2, a strong turbulence regime when the...
Turbulence measurements for very stable conditions near the surface are contrasted
among three sites: a high altitude basin during winter with grass or snow-covered
grass, a broad valley with complex agricultural land use, and a more narrow valley that is
influenced by a valley cold pool and cold air drainage....
The authors investigate atmospheric internal gravity waves (IGWs): their generation and induction of global intermittent turbulence in the nocturnal stable atmospheric boundary layer based on the new concept of turbulence generation discussed in a prior paper by Sun et al. The IGWs are generated by air lifted by convergence forced...
Turbulence measurements for very stable conditions near the surface are contrasted
among three sites: a high altitude basin during winter with grass or snow-covered
grass, a broad valley with complex agricultural land use, and a more narrow valley that is
influenced by a valley cold pool and cold air drainage....
The light-wind, clear-sky, very stable boundary layer (vSBL) is characterized by large values of bulk
Richardson number. The light winds produce weak shear, turbulence, and mixing, and resulting strong
temperature gradients near the surface. Here five nights with weak-wind, very stable boundary layers during
the Cooperative Atmosphere–Surface Exchange Study (CASES-99)...
Aircraft data collected at approximately 15 m above the sea surface in the coastal zone are analyzed to examine the spatial distribution of surface stress. Advection of stronger turbulence from land dominates the near-surface turbulence for the first few kilometers offshore. With offshore flow of warm air over cold water,...
This study addresses the relationship between thermal microfronts and coherent vortex structures in homogeneous turbulence. The turbulence is created by mean shear in a weakly stratified flow. The data set is generated by direct numerical simulation providing highly resolved instantaneous three‐dimensional fields of fluctuating velocity and temperature (1603 data points...
Whole ecosystem carbon dioxide (CO₂) exchange estimated with the eddy covariance (EC) technique has been central to studies on the responses of terrestrial ecosystems to disturbance and intra‐annual and interannual variations in climate, but challenges exist in understanding and reducing the uncertainty in estimates of net ecosystem exchange (NEE) of...
Numerical weather prediction models often perform poorly for weakly forced, highly variable winds in nocturnal stable boundary layers (SBLs). When used as input to air-quality and dispersion models, these wind errors can lead to large errors in subsequent plume forecasts. Finer grid resolution and improved model numerics and physics can...
Relationships among the horizontal pressure gradient, the Coriolis force, and the vertical momentum transport by turbulent fluxes are investigated using data collected from the 1999 Cooperative Atmosphere-Surface Exchange Study (CASES-99). Wind toward higher pressure (WTHP) adjacent to the ground occurred about 50% of the time. For wind speed at 5...