From the earliest attempt at numerical weather prediction up until today's efforts on improving the land surface hydrologic parameterization in General Circulation models (GCMs), it has been recognized that the realistic characterization of atmospheric phenomena requires accurate representation of surficial processes. Lewis F. Richardson who attempted numerical weather prediction using hand calculations around the First World War period includes, in his notes, a parameterization of the surface evapotranspiration and plant stomatal control of the vapor exchange between land and atmosphere. He writes: “…Let the rate of loss of water from a leaf be denoted by T, then (Formula Presented.) here K is the conductance of the stomatal openings and F (θleaf) is the saturated vapour density at θ.” [Richardson, 1922]. Almost three‐quarters of a century later and using high‐speed digital computers, the research community is essentially implementing Lewis F. Richardson's original scheme of stomatal resistance to vapor flux between the saturated interior of leaves at temperature 9ieaf and near‐surface air humidity wair. At first sight it may appear that not much scientific progress has been made in the interim years. Transpiration, turbulence and other processes related to land‐atmosphere exchange are complex phenomena and in fact there has been significant recent advances in the study of land‐atmosphere interaction. The land, biosphere, atmosphere and ocean systems are coupled across a wide range of space and time scales such that each discovery leads to a deeper and larger scientific question. Research inquiry in this area is now performed in both the hydrologic and the atmospheric science communities. Copyright 1995 by the American Geophysical Union.
