Stepp, R. D. and Martsolf, J. D., 1973. An error analysis of the measurement of horizontal divergence in the wind field of a small, heated orchard. Agric. Meteorol., 12:249 257. During the springs of 1970 through 1972, an attempt to observe the net heat advected out of a 0.57-ha sour cherry orchard heated with 120 large cone heaters was made. An important part of this effort was the estimation of ~ (the spatial mean vertical component of the wind at the orchard's top surface) by first measuring the horizontal component of the wind normal to each of the orchard's four vertical faces, and then employing the equation of continuity. The above mentioned measurements are subject to several anemometer errors. Among these are the u-error, imperfect cosine response, stalling, and spatial sampling errors. The effect of each of these on the eventual ~ estimate was calculated. It was found that while the u and stalling errors were negligible, the cosine response and spatial sampling errors were significant (each _+0.2 cm sec -~ ). Of the latter two, the first can be easily calculated and its effect on the estimation of ~ removed, ttowever, spatial sampling error cannot be reduced without employing more instruments.