FABLE: Forest Atmosphere Boundary Layer Experiment

Summary

An NCAR ISS will be deployed at the Park Falls, Wisconis tall tower site (WLEF-TV tower, instrumented as part of the Chequamegon Ecosystem-Atmosphere Study) for the month of August, 2000. The deployment will conincide both with continuous flux and mixing ratio measurements collected from WLEF and, most importantly, with a series of airborne over-flights conducted as part of the CO₂ Budget and Rectification Airborne study (COBRA). The one-month COBRA intensive will provide direct validation of the CO₂ profile calculations being conducted as part of the Forest Atmosphereic Boundary Layer Experiment (FABLE). FABLE has utilized the NCAR Integrated Sounding Systems (ISS) during 1998 at WLEF, and during 1999 at WLEF and Walker Branch Watershead, Oak Ridge, Tennessee. One goal of this study is to determine the seasonal pattern of the vertical distribution of CO₂ in the boundary layer and lower troposphere. An understanding of this distribution is needed to proplery interpret the global network of CO₂ flask samples that is used to constrain the global carbon budget. FABLE is relying on the tall tower CO₂ mixing ratio data (maximum altitude 396m) and rawinsonde temperature and humidity data to validate their methodology. Direct observations of the vertical and horizontal distribution of CO₂ that can be obtained via the COBRA aircraft will provide a valuable additional test of the FABLE results. The ISS will also add wind profile that has proven very valuable, in a June 1999 test flight, to interpreting the vertical profiles of CO₂ and other chemical tracers obtained by the COBRA aircraft.

The objectives of the Forest ABL coupling experiment are to observe and simulate how surface processes and boundary-layer development interact to modulate NEE of CO2. Also to Derive tropospheric CO2 mixing ratios via estimates of the entertainment flux and compare the modeled values. Also to see if the the results vary across North America and/or ecosystems.