Kz. Kaminsky et R. Dubayah, ESTIMATION OF SURFACE NET-RADIATION IN THE BOREAL FOREST AND NORTHERNPRAIRIE FROM SHORTWAVE FLUX MEASUREMENTS, J GEO RES-A, 102(D24), 1997, pp. 29707-29716
The relationships between net radiation and surface shortwave fluxes w
ere explored by using one year of 15 min surface flux data for nine si
tes in central Canada. The sites were located throughout a 50,000 km(2
) area, in conjunction with the BOREAS project, across a gradient in s
urface cover from prairie grassland to boreal forest. When insolation
alone was used to estimate instantaneous net radiation, the r(2) value
s at the nine sites ranged from 0.93 to 0.98. The use of the net short
wave flux as a predictor improved the range in r(2) values to between
0.96 and 0.99. The root-mean-square error across sites varied from 26
to 41 W m(-2) without albedo to a range of 18-36 W m(-2) when albedo w
as included. The data for all sites were combined to produce a single
linear relationship with an r(2) value of 0.97 and a root-mean-square
error (RMSE) of 29 W m(-2) when the surface albedo is included. Cross
validations were performed where the data for eight sites were used to
predict net radiation at a ninth (excluded) site, revealing little si
te-specific bias. Classifications of the data by season and by transmi
ttance provided little improvement in estimated net radiation at any s
ite. Our study suggests that a single equation using net shortwave flu
x alone can be used to estimate net radiation for large portions of th
e boreal forest and northern prairie, regardless of spatial and tempor
al variation in surface cover and atmospheric conditions.