Surface-layer fluxes in stable conditions

• Published in: Boundary - layer meteorology Vol. 90; no. 3; pp. 495 - 520
• Main Authors: HOWELL, J. F, SUN, J
• Format: Conference Proceeding Journal Article
• Language: English
• Published: Dordrecht Springer 01.03.1999; Springer Nature B.V
• Subjects: Convection, turbulence, diffusion. Boundary layer structure and dynamics; Earth, ocean, space; Exact sciences and technology; External geophysics; Fluctuations; Meteorology; Studies; Kansas; United States; North America; America; Sampling error; Micrometeorology; Night; Atmospheric turbulence; Atmospheric boundary layer; Surface layer; Flux; Similarity theory; Atmospheric stability; Heat transfer
• ISSN: 0006-8314; 1573-1472
• DOI: 10.1023/A:1001788515355

Micrometeorological tower data from the Microfronts experiment are analyzed. Scale-dependencies of the flux and flux sampling error are combined to automatically determine Reynolds turbulence cut-off time scales for computing fluxes from time series. The computed downward heat flux at the 3 m height averaged over nine nights with 7.3 hours each night is 20% greater than the downward heat flux computed at the 10 m height. In contrast, there is only a 1.2% difference between 3 m and 10 m heat fluxes averaged over daytime periods, and there is less than a 2% difference between 3 m and 10 m momentum fluxes whether averaged over nighttime or daytime periods. Stability functions, ΦM(z/L) and ΦH(z/L) are extended to z/L up to 10, where z is the observational height and L is the Obukhov length. For 0.01 < z/L < 1 the estimated Φ functions generally agree with Businger-Dyer formulations, though the ΦH estimates include more scatter compared to the ΦM estimates. For 1 < z/L < 10, the flux intermittency increases, the flux Richardson number exceeds 0.2, and the number of flux samples decreases. Nonetheless the estimates of the stability function ΦM based on 3-m fluxes are closer to the formula proposed by Beljaars and Holtslag in 1991 while the ΦM functions based on 10-m fluxes appears to be closer to the formula proposed by Businger et al. in 1971. The stability function ΦH levels off at z/L = 0.5.[PUBLICATION ABSTRACT]