Estimates of integral time scales from a 100-M meteorological tower at a plains site |
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| Authors: | G E Moore Mei-Kao Liu Lu-Huai Shi |
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| Institution: | (1) Systems Applications, Inc., 94903 San Rafael, CA, USA;(2) Atmospheric Environmental Monitoring and Research Center, Ministry of Electric Power, People's Republic of China |
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| Abstract: | Four distinct types of autocorrelograms were observed using high-frequency vertical velocity data measured at 100 m above a flat terrain. Several types of nonstationary atmospheric motions due to low frequency fluctuations were examined. Under nighttime stable conditions, these phenomena were found to lead to abnormally slow exponential decay of the autocorrelation function. Several different techniques for estimating Eulerian integral time scales were compared in order to select an appropriate method of estimation. When grouped by stability classes, the Eulerian integral time scales decrease slightly with increasing stability, but generally exhibit no significant correlation with other meteorological parameters. Using a postulated relation, estimates of the Lagrangian to Eulerian integral time scale ratio range from 3 to 5 under unstable conditions and 15 to 25 under stable conditions. Under unstable conditions the average Lagrangian integral time scale is on the order of 40 s and exhibits no significant correlation with several pertinent meteorological parameters. Under stable conditions, the Lagrangian integral time scale correlates well with the Monin-Obukhov length and temperature lapse rate.Work conducted while a visiting scholar at Systems Applications, Inc. |
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