Analysis of periods with strong and coherent CO 2 advection over a forested hill
Agricultural and forest meteorology
Pages / Article-Number
Forest ecosystems, Advection, Net ecosystem exchange, Carbon balance, ADVEX
Horizontal and vertical advective ﬂuxes of CO 2 measured during the CarboEurope-IP advectionexperiment (ADVEX) at the Wetzstein spruce forest site in Thuringia, Germany, were related to winddirection, stratiﬁcation regime and friction velocity u * . Measurements of wind speed and directioncarried out at one of the slopes of the ridge revealed the existence of reverse ﬂow below the canopy onthe downwind side. This uphill ﬂow occurred concurrently with the advective ﬂuxes measured at the topof the hill. Such result is in agreement with recent modeling works that support the existence ofadvection at low hills covered with a canopy. Another experimental evidence that suggest a link betweenadvection at this site with the ﬂow over the hill came from the analysis of the horizontal gradient of CO 2inside the volume formed by the ADVEX towers. It was observed that CO 2 accumulated near thedownwind side of the crest for cross-ridge ﬂows, what is consistent with another modeling work of thetransport of scalars across a low hill covered with a canopy.