Julio Tóta*, David Roy Fitzjarrald**, Ralf M. Staebler***, Ricardo K. Sakai**

1. - JRG Dozens of measurements need to be synchronized: 3D Sonic #1 RS-232 lines Licor #1 Data Acquisition Hardware Links 3D Sonic #2 PC, Linux System Licor #2 23X Cyclades Network Link Multi-Serial Port 3D Sonic #3 to Albany 23x Zip Drive Dat Tape CR10x etc. 2 meter above ground 2D North 75m 2D East 2D West 2D Tower 75m 2D South Measuring subcanopy CO2 advection in the FLONA Tapajós Julio Tóta*, David Roy Fitzjarrald**, Ralf M. Staebler***, Ricardo K. Sakai** * LBA Project Office, INPA, Manaus AM, tota@lbaeco.com.br ** Jungle Research Group, University at Albany, SUNY,, fitz@asrc.cestm.albany.edu *** ARQP, Meteorological Service of Canada, Toronto ON., ralf.staebler@ec.gc.ca INTRODUCTION At night, a shallow thermal inversion develops near the surface and deepens with time, under low wind speed conditions and radiational cooling. If terrain is not level, a drainage flow can develop. Above forests the flow above the canopy becomes decoupled from the flow just above and within canopy. It is possible that the drainage flow will carry respiratory CO2 from foliage, boles, and soil downslope. If this flow advects CO2 away from observation tower, some CO2 emission goes unmeasured. Eddy covariance systems above canopy will not detect this flux. A horizontal gradient in CO2 coupled with a persistent flow in a certain direction, can create non-zero horizontal advection terms of the form (u)(dc/dx)+(v)(dc/dy), terms commonly assumed to be zero. We report preliminary results from measurements of the horizontal advection of CO2, which may explain the “missing” vertical CO2 fluxes on frequent calm nights, when the eddy covariance technique fails to detect nocturnal respiration properly. The aim is to actually measure this term to determine its significance. RESULTS CALIBRATION PERIOD (July 12-15 2003) To determine instrumental differences, all anemometers were co-located within a radius of about 2m at the end of each study for this period. A realistic detection limit for divergences using this setup is on the order of ±4x10-3 s-1. The wind speeds on the order of a few cm s-1 can be reliably measured in the subcanopy. SUBCANOPY ARRAY EXPERIMENTAL AND METODOLOGY LOCALIZATION: The JRG Draino data are being collected about 60 km south of Santarém, Pará, Brazil. The data set will be useful to extend the study to the topographical effects of a large nearby river, a large escarpment, and a slope opposing the prevailing winds. From the map it is clear that the flux towers may be affected in different ways by local topography; the Old Growth Site is only a few kilometers from the Tapajos escarpment, and may experience drainage flows towards the west. Meteorological stations were chosen to help in identifying various topographical effects, for example airshed drainage from the Old Growth site to the river (specifically Jamaraqua), escarpment effects (Belterra), and the extent of the river breeze effect (Mojui, km 117). MEASUMENTS AND AIR SAMPLING: Data acquisition was handled with a system developed at ASRC. The hardware consists of a Pentium II computer running a Linux operating system, with a Cyclades multiple serial board (CYCLOM-16YeP/DB25) collecting any arbitrary number of serial streams. Individual serial data streams from all instruments were synchronized and merged in real time, producing ASCII data files that are immediately processed by another program running in parallel. This program calculated half hour means, 2nd – 4th moments, cross-products, power and covariance spectra, and auto- and cross-covariance functions. The system is designed to be flexible and can be easily modified for various field projects, with different instrument configurations and output product requirements. A schematic of the air flow system is show. The flow out of the main pump at km67 was measured to be about 45 L/min. There is continuous flow through all 10 lines at all times. A rotating valve diverts an additional amount of air from the main lines through the Licor, for 20 seconds for each of the 10 lines. During this “active” period, the flow through the line is increased by typically 0.5 L/min, as measured by rotameter at the inlet. SUBCANOPY CO2 PROFILE SUBCANOPY HORIZ. GRADIENTS ANALYSIS PERIOD (July 17 – August 26 2003) DOY 200/2003 SUBCANOPY FLOW The air shed drainage from the Old Growth site to the river agree with wind direction in Jamaraqua station. The flow rate through the 10 sample lines is best determined by timing the arrival of a CO2 spike, generated by breathing into the inlet, at the Licor. If this is not possible, e.g. on solo trips, a flow meter (rotameter) can be attached to the inlet. Note that the rotameter itself represents a major restriction (resistance) to the flow, and the flow rate read does NOT actually represent the unrestricted air flow through the line. But the reading can still be used to check for consistency, and that there is actually flow through the line. The flow rates read with a rotameter are around 3 L/min for the six short lines (profile) and about 1.0 L/min for the long (horizontal) lines, and will increase by about 0.5 L/min while the line is active (i.e. during the 20 seconds while the rotating valve is sampling the line). REFERENCES Staebler, R.M., D.R. Fitzjarrald, M.J. Czikowsky and R.K. Sakai, 2001: Nocturnal CO2 fluxes and understory drainage flows. Fall Conference of the American Geophysical Union, San Francisco, CA. Staebler, R.M., D.R. Fitzjarrald, K.E. Moore, M.J. Czikowsky and O.C. Acevedo, 2000a: Topographic effects on flux measurements at Harvard Forest. 14th Symposium on Boundary Layers and Turbulence / Ninth Conference on Mountain Meteorology, Aspen, CO. Staebler, R.M., PhD Thesis. Fitzjarrald, D.R. et al. 2000. Fitzjarrald, D.R., 1984: Katabatic wind in opposing flow. J. Atm. Sc. , 41, 1143-1158. Aubinet, M., B. Heinesch and M. Yernaux, 2003. Horizontal and vertical CO2 advection in a sloping forest. Bound. Layer Meteorol. 108:397-417. 2003 for more information: Julio Tota tota@inpa.gov.br LBA/INPA/SUNY Manaus – Brasil – CEP.: 69083-000 phone 55 XXX 92 643 3255 fax 55 XXX 92 643 3238