Spatial distribution of intermittent turbulence during CASES99.
A suite of three sonic anemometers, two minisodars, and a laser scintillometer were used at four locations in the Atmospheric Boundary Layer Experiments (ABLE) facility during the Cooperative Atmosphere Surface Exchange Study 1999 (CASES99) to study the spatial and temporal evolution of intermittent turbulence during very stable conditions. Two locations were within the main CASES99 site at Leon, KS, separated by roughly 1 km; the remaining sites were about 15 km east (Beaumont) and 20 km south (Smileyburg). Sudden increases from an otherwise quiescent signal of downward heat flux (as measured by sonic anemometers and lasers scintillometer) or temperature structure parameter correlation with vertical velocity (from minisodars) were used to define intermittent turbulence. It was generally found that there was little or no one-to-one correlation among turbulent episodes at Leon, Beaumont, and Smileyburg. Within the Beaumont and Leon sites, there were multiple instances of near-simultaneous bursts as observed with sonic - minisodar and scintillometer - minisodar comparisons separated by 20 - 100 m, perhaps indicating that the spatial extent of nocturnal bursts of turbulence varies from a few meters to greater than 1 km but rarely extends beyond 10 km. There were several well defined events, such as microfronts and/or density currents, that were observed at all four sites, generally with a time delay. During the 30 day experimental period, there were only 6 nights with largely quiescent conditions punctuated by periods of intermittent turbulence; the remaining nights were characterized by nearly continuous significant downward heat fluxes, forced by strong winds aloft. The six nights were characterized by relatively light winds and predominantly northerly wind directions. The overall character of the turbulence in terms of duration, frequency of occurrence, and range of turbulence intensity was similar at all sites. However, there were significant differences between overall turbulence intensities between sites on individual nights.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- DE-AC02-06CH11357
- OSTI ID:
- 943230
- Report Number(s):
- ANL/ER/JA-38506; TRN: US200916%%671
- Journal Information:
- EOS, Trans., Am. Geophys. Union, Vol. 81, Issue 48 ; 2000
- Country of Publication:
- United States
- Language:
- ENGLISH
Similar Records
Intermittent turbulence events observed with a sonic anemometer and minisodar during CASES99.
Structure of the nocturnal boundary layer over a complex terrain