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Ann. Geophys., 24, 415-426, 2006
www.ann-geophys.net/24/415/2006/
© European Geosciences Union 2006
Analysis of wind data in the low atmosphere from a RASS sodar
I. A. Pérez, M. A. García, M. L. Sánchez, and B. de Torre
Department of Applied Physics, Faculty of Sciences, University of Valladolid, Valladolid, Spain
Abstract. This paper focuses on the ability of a sodar to describe some
characteristics of the atmospheric vertical structure and presents some
techniques for meteorological data evaluation. The measuring campaign took
place in April 2001 and consisted of 10-min averages covering the lower
atmosphere from 40 to 500 m at 20-m levels. Three methods were considered,
the first of which was a scalar analysis performed using a combination of
wind and temperature median profiles. A noticeable contrast between day and
night was obtained. Flat wind profiles during the day were a consequence of
prevailing convective conditions that determined thermal turbulence. A
stable layer above 260 m capped the unstable layer situated below and
guaranteed the stability of the boundary layer. During the night, the
presence of a low level jet was the most significant feature. The height of
the core was 340 m and the higher vertical winds defined it clearly. The
second method focused on the wind vector. In this analysis, the
anti-cyclonic rotation of hourly averages was considered in the lower levels
where it was observed. After a translation of the origin, an empirical,
robust model with two parts was then proposed for the resulting vector. The
angle was described linearly and the module by a second order model for
cylindrical data. Finally, as a third method, three regression analyses were
investigated: vectorial, taking every wind component separately and scalar.
The two first seemed to be more complete due to their description of
anti-cyclonic wind rotation when height increased. Correlation coefficients
also proved to be more satisfactory. As a consequence, these techniques,
although less frequently used, are more suitable to study wind in the low
atmosphere.
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