کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
81586 158326 2015 13 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Secondary circulations at a solitary forest surrounded by semi-arid shrubland and their impact on eddy-covariance measurements
ترجمه فارسی عنوان
انتشارات ثانویه در یک جنگل انفرادی احاطه شده توسط بوته نیمه خشک و تأثیر آنها بر اندازه گیری کوجیما
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات علم هواشناسی
چکیده انگلیسی


• Eddy covariance, Doppler lidar measurements and LES at Yatir forest, Israel.
• Surface buoyancy flux is 220–290 W m−2 higher above the forest.
• Development of a secondary circulation between forest and desert.
• Non-closure of energy balance due to low-frequency contributions.

The Yatir forest in Israel is a solitary forest at the dry timberline that is surrounded by semi-arid shrubland. Due to its low albedo and its high surface roughness, the forest has a strong impact on the surface energy budget, and is supposed to induce a secondary circulation, which was assessed using eddy-covariance (EC) and Doppler lidar measurements and large-eddy simulation (LES). The buoyancy fluxes were 220–290 W m−2 higher above the forest, and the scale of the forest relative to the boundary-layer height is ideal for generating a secondary circulation, as confirmed by a LES run without background wind. However, usually a relatively high background wind (6 m s−1) prevails at the site. Thus, with the Doppler lidar a persistent updraft above the forest was detected only on 5 of the 16 measurement days. Nevertheless, the secondary circulation and convective coherent structures caused low-frequency flux contributions in the mixed-layer w spectra, the surface layer u and w spectra and in the surface-layer momentum fluxes. According to the ogive functions from the tower data and a control volume approach using the LES, such low-frequency contributions with timescales >30 min were a major reason the non-closure of the energy balance at the desert site. In the roughness sublayer above the forest, these large structures were broken up into smaller eddies and the energy balance was closed.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Agricultural and Forest Meteorology - Volumes 211–212, 15 October 2015, Pages 115–127
نویسندگان
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