SENSIBLE AND LATENT-HEAT FLUX PREDICTIONS USING CONDITIONAL SAMPLING METHODS

The conditional sampling formulation typically used in eddy accumulati on flux measurements was tested at two sites using velocity, temperatu re, and specific humidity time series measurements. The first site was at Owen's Lake in southern California, and the second site was an irr igated bare soil field at the Campbell Tract facility in Davis, Califo rnia. The constant beta relating the turbulent flux to the accumulated concentration difference between updrafts and downdrafts was related to the statistics of the vertical velocity. It was found that this for mulation for beta reproduces the extreme fluxes (both senible and late nt heat) better than previous beta formulations. The overall compariso n between eddy correlation measured fluxes and conditional sampling pr edicted fluxes for a wide range of atmospheric stability conditions wa s excellent (R2 = 0.97). On average, the mean beta obtained from our e xperiments for temperature and water vapor is in good agreement (+/-4% ) with other reported beta values for carbon dioxide, water vapor, ozo ne, and temperature. These results suggest that the conditional sampli ng formulation used in eddy accumulation methods is useful for routine flux measurements of passive greenhouse gases.