The value of the effective exchange coefficient for area-averaged fluxes can depend significantly on the averaging scale. This dependence implies that the exchange coefficient in numerical models should depend on grid size. The main goal of this study is the assessment of the importance of such scale-dependence. When the large-scale...
This study examines the bulk aerodynamic method for estimating surface fluxes of heat and moisture using the surface radiative temperature. The surface radiative temperature is often the only available surface temperature from field measurements. Models typically predict heat fluxes from the surface radiative temperature computed from the surface energy balance....
This study relates surface fluxes to remotely sensed variables over well-defined variations of surface wetness and vegetation. The surface fluxes are estimated from repeated Twin Otter aircraft flights at 33 m above the surface after correcting for advection and local storage between the aircraft level and the surface. An extensive...
The exchange coefficients for area-averaged surface fluxes can become anomalously large when the large-scale flow is weak and significant fluxes of heat and moisture are driven by mesoscale motions within the averaging or subgrid area. To prevent this erratic behavior of the exchange coefficient, the “subgrid velocity scale” must be...
The authors reconsider the problem of estimating the sensible heat transfer at the earth's surface from direct measurements of turbulent fluxes in the atmospheric boundary layer. For simplicity, only horizontally homogeneous conditions are considered for a thin atmospheric layer containing no liquid water, adjacent to the earth's ground surface. Applying...
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...
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...
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...
The horizontal and vertical structure of the mean flow and turbulent fluxes are examined using aircraft
observations taken near a barrier island on the east coast of the United States during offshore flow periods. The
spatial structure is strongly influenced by the surface roughness and surface temperature discontinuities at the...
Toward the goal of predicting area-averaged evapotranspiration, the evaporative fraction is modelled in terms of surface radiation temperature, air temperature, solar zenith angle, Normalized Difference of the Vegetation Index and albedo. Previous relationships break down when applied simultaneously to a variety of surfaces. The zenith angle is required to account...