CO2 Vertical Advection and its importance on the Eddy Covariance Flux: LBA Multi-site analyses
Silva, INPA, firstname.lastname@example.org
Randow, INPA, email@example.com
Since begin of LBA Project measurement of Net ecosystem exchange of carbon dioxide (NEE) is routinely measured at several sites around the Amazonia. In the recent literature research has indicated that the interpretation of NEE from eddy covariance (EC) measurements may be questionable in night-time stable conditions, particularly in areas of complex terrain. It has been suggested that one cause of the observed underestimation of nocturnal ecosystem respiration by the EC method is vertical and horizontal advection of mass out of the ecosystem. The vertical advection has been reported in subtropical areas in Europe and USA, but there is none information in the literature about the importance of vertical and horizontal advection correction the night time EC CO2 flux in the LBA Project sites in Amazonia. This work examines vertical motion and the importance of vertical advection on EC flux in the Manaus, Santarem and Rondonia LBA sites. The vertical motions found in the Santarem Flona Tapajos have a tendency to downward vertical velocities at nighttime relative to the daytime. This tendency have inverse pattern in the Manaus LBA site. The contribution of the vertical advection seems related with terrain complexity and composition of the ecosystems where the tower-based were place. This pattern may result in vertical advection of CO2-depleted air unaccounted for by EC measurements. There is large part of the time that below-canopy flow (and scalar transport) is decoupled from conditions aloft. These results support arguments that the inclusion of simple advection terms in estimates of ecosystem respiration, based on above-canopy measurements, is specific site-to-site and not universally applicable.