On Height of the Surface Air Layer by Sodar Data

Pub Date : 2024-05-14 DOI:10.1134/s0001433824700063

M. A. Lokoshchenko

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Abstract

Average empirical estimations of the surface air layer height in Moscow have been received by the data of long-term acoustic remote sensing of the atmosphere using the MODOS Doppler sodar (METEK, Germany). Based on the assumption that the average conditions are close to neutral stratification, this height, as the top of the quasi-linear section of the average long-term wind velocity profile in semilogarithmic coordinates, is 40–60 m. The wind rotation height, i.e., the height of intersection of day and night wind profiles, is 95 m per year on average. The roughness length in conditions of loosely packed but high urban development in the vicinity of Moscow State University in Moscow is 5 m. According to the criterion of the constant wind direction in the surface air layer, its height manifests itself in the monthly average wind direction profiles over the “dead zone” of the sodar (40 m) in approximately one out of three cases and usually amounts to 60 m (less often 80 or 100 m). In all other cases, it is apparently masked by the dead zone. According to this approach, the average height of the surface layer is probably a little less than 50 m, which is close to the estimate obtained from the logarithmic distribution of wind velocity with height in this layer. The daily variation of the surface air layer height is noted by the largest values in the afternoon (80–100 m in summer under conditions of prevailing unstable stratification and 60–80 m in winter) and the smallest ones (less than 40 m) in the late evening and at night in summer and from evening to noon in winter.

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通过 Sodar 数据了解地表空气层高度

摘要莫斯科地表空气层高度的平均经验估计是通过使用 MODOS 多普勒超声波雷达（德国 METEK 公司）对大气进行长期声学遥感的数据得出的。根据平均条件接近中性分层的假设，该高度作为半对数坐标中长期平均风速剖面的准线段顶端，为 40-60 米。根据地表空气层风向恒定的标准，其高度在索达 "死区"（40 米）的月平均风向剖面图中约占三分之一，通常为 60 米（较少为 80 或 100 米）。在所有其他情况下，风向剖面显然被死区所掩盖。根据这种方法，表层的平均高度可能略低于 50 米，这与表层风速随高度变化的对数分布得出的估计值相近。表层空气高度的日变化特点是：下午的数值最大（夏季不稳定分层条件下为 80-100 米，冬季为 60-80 米），夏季傍晚和夜间的数值最小（小于 40 米），冬季从傍晚到中午的数值最小（小于 40 米）。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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