Evidence of nocturnal horizontal transport of CO2 at an Amazon pasture/agricultural site Otávio Acevedo, Osvaldo Moraes, Rodrigo da Silva Universidade Federal de Santa Maria, Santa Maria, RS, Brazil David Fitzjarrald, Ricardo Sakai, Matt Czikowski Atmospheric Sciences Research Center, Albany, NY, USA
Motivation: CO2 accumulation rates observed at the Km 77 flux tower • What is causing the strong (and shallow) peak in CO2 accumulation rate, around 2200 LST?
Hypothesis: the peak marks the arrival of the drainage flow, transporting CO2 from the forest Km 77 tower
- Largest accumulation rates are observed whennorthwesterlies (from the forest, downslope) prevail; - Smallest accumulation rates for northerlies (from unforested regions)
Boundary layer CO2 profiling system (designed by Rodrigo da Silva)
What is the accumulation rate during the evening peak? 6.8 ppm/h 6.1 ppm/h
Who cares? • Estimations of the nocturnal respiration rates by the accumulation method are affected: Example: assuming a 50-m thick boundary layer and vertically homogeneous accumulation rate: Respiration rates:
Alternatively: assuming a 0.08-mg CO2 m-2 s-1 respiration rate and vertically homogeneous accumulation rate: Boundary layer thickness: FUTURE WORK • Go further from simple evidences; • Make a more detailed quantitative analysis