کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4459548 1621289 2011 10 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Relating the X-band opacity of a tropical tree canopy to sapflow, rain interception and dew formation
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات کامپیوتر در علوم زمین
پیش نمایش صفحه اول مقاله
Relating the X-band opacity of a tropical tree canopy to sapflow, rain interception and dew formation
چکیده انگلیسی

During summer and autumn 2007, a 11 GHz microwave radiometer was deployed in an experimental tree plantation in Sardinilla, Panama. The opacity of the tree canopy was derived from incoming brightness temperatures received on the ground. A collocated eddy-covariance flux tower measured water vapor fluxes and meteorological variables above the canopy. In addition, xylem sapflow of trees was measured within the flux tower footprint. We observed considerable diurnal differences between measured canopy opacities and modeled theoretical opacities that were closely linked to xylem sapflow. It is speculated that dielectric changes in the leaves induced by the sapflow are causing the observed diurnal changes. In addition, canopy intercepted rain and dew formation also modulated the diurnal opacity cycle. With an enhanced canopy opacity model accounting for water deposited on the leaves, we quantified the influence of canopy stored water (i.e. intercepted water and dew) on the opacity. A time series of dew formation and rain interception was directly monitored during a period of two weeks. We found that during light rainfall up to 60% of the rain amount is intercepted by the canopy whereas during periods of intense rainfall only 4% were intercepted. On average, 0.17 mm of dew was formed during the night. Dew evaporation contributed 5% to the total water vapor flux measured above the canopy.

Research highlights
► Microwave opacity of a tree canopy is closely related to the xylem sapflow.
► The percentage of canopy intercepted water depends on the rainfall intensity.
► First direct measurement of the temporal dew evolution in a tree canopy.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Remote Sensing of Environment - Volume 115, Issue 8, 15 August 2011, Pages 2116–2125
نویسندگان
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