Scaling up flux measurements for the boreal forest using aircraft‐tower combinations

Fluxes of carbon dioxide, water vapor, sensible heat, and momentum obtained over the boreal forest from the Twin Otter aircraft and six tower-based systems are compared. These measurements were collected as part of the Boreal Ecosystem-Atmosphere Study (BOREAS) during three intensive field campaigns between May 25 and September 17, 1994. The representativeness of the tower-based measurements collected during BOREAS is discussed. Even though the net radiation from aircraft- and tower-based systems agreed well, in general, the aircraft tended to observe larger latent heat and smaller sensible heat fluxes than the towers. The CO2 fluxes from the aircraft were substantially less than from the tower, while the differences were relatively small for the momentum fluxes. The relationships between aircraft and tower-based flux measurements obtained by making repeated runs past various towers are used to scale up tower-based fluxes to a 16×16 km2 area near Prince Albert, Saskatchewan. It is demonstrated that except for a couple of cases primarily due to rapidly changing radiation conditions, this combination of measurements provides regional flux estimates of momentum, CO2, and sensible and latent heat similar to those obtained by flying a grid pattern over the area.

[1]  A. Perrier,et al.  HAPEX—MOBLIHY: A Hydrologic Atmospheric Experiment for the Study of Water Budget and Evaporation Flux at the Climatic Scale , 1986 .

[2]  Peter D. Blanken,et al.  Annual cycles of water vapour and carbon dioxide fluxes in and above a boreal aspen forest , 1996 .

[3]  Larry Mahrt,et al.  An Adaptive Decomposition: Application to Turbulence , 1994 .

[4]  Monique Y. Leclerc,et al.  Footprint prediction of scalar fluxes from analytical solutions of the diffusion equation , 1990 .

[5]  J. I. MacPherson,et al.  Effects of spatial variability in topography, vegetation cover and soil moisture on area-averaged surface fluxes: A case study using the FIFE 1989 data , 1995 .

[6]  Alexander Gluhovsky,et al.  A definitive approach to turbulence statistical studies in planetary boundary layers , 1994 .

[7]  Spatial Distribution of Surface Fluxes Estimated from Remotely Sensed Variables , 1994 .

[8]  D. Baldocchi,et al.  Energy and CO(2) flux densities above and below a temperate broad-leaved forest and a boreal pine forest. , 1996, Tree physiology.

[9]  D. Lenschow,et al.  Errors in airborne flux measurements , 1994 .

[10]  J. I. MacPherson,et al.  Water Vapor Flux Measurements from Aircraft , 1991 .

[11]  J. I. MacPherson,et al.  Spatial and temporal variations of the fluxes of carbon dioxide and sensible and latent heat over the FIFE site , 1992 .

[12]  L. Mahrt,et al.  The influence of coherent structures and microfronts on scaling laws using global and local transforms , 1994, Journal of Fluid Mechanics.

[13]  R. Desjardins,et al.  Crop net carbon dioxide exchange rate and radiation use efficiency in soybean , 1995 .

[14]  R. Desjardins,et al.  Mass and energy exchanges over a black spruce forest during key periods of BOREAS 1994 , 1997 .

[15]  L. Barrie,et al.  The Northern Wetlands Study (NOWES): An overview , 1994 .

[16]  Eric A. Smith,et al.  Area‐averaged surface fluxes and their time‐space variability over the FIFE experimental domain , 1992 .

[17]  William J. Massman,et al.  California ozone deposition experiment: Methods, results, and opportunities , 1995 .

[18]  J. I. MacPherson,et al.  Footprint considerations in BOREAS , 1997 .

[19]  H. Schmid.  Source areas for scalars and scalar fluxes , 1994 .

[20]  R. L. Desjardins,et al.  A Micrometeorological Facility for Eddy Flux Measurements of CO2 and H2O , 1989 .

[21]  Hans Peter Schmid,et al.  The influence of surface texture on the effective roughness length , 1995 .

[22]  Adjustment of footprint correction for airborne flux mapping over the FIFE site , 1992 .

[23]  Robert L. Grossman,et al.  Scale Dependence of Air-Sea Fluxes over the Western Equatorial Pacific , 1996 .

[24]  J. I. MacPherson,et al.  Aircraft- and tower-based fluxes of carbon dioxide, latent, and sensible heat , 1992 .

[25]  J. I. MacPherson,et al.  An evaluation of aircraft flux measurements of CO2, water vapor and sensible heat , 1989 .

[26]  J. I. MacPherson,et al.  Flux estimates of latent and sensible heat, carbon dioxide, and ozone using an aircraft-tower combination , 1995 .

[27]  L. Mahrt.  Boundary‐layer moisture regimes , 1991 .

[28]  J. I. MacPherson,et al.  Budget analysis of the boundary layer grid flights during FIFE 1987 , 1992 .

[29]  H. Neumann,et al.  Energy budget measurements using eddy correlation and Bowen ratio techniques at the Kinosheo Lake tower site during the Northern Wetlands Study , 1994 .

[30]  J. I. MacPherson,et al.  Boundary-layer heat and moisture budgets from fife , 1990 .

[31]  Analysis of flux maps versus surface characteristics from Twin Otter grid flights in BOREAS 1994 , 1997 .

[32]  P. Sellers,et al.  The First ISLSCP Field Experiment (FIFE) , 1988 .