The role of "rural" in comparisons of observed suburban-rural flux differences

Simultaneous measurements of surface energy balance fluxes and other climate variables were made at suburban, wet and dry sites in the Sacramento region, California, during late August 1991. The sites have classic energy partitioning; with average Bowen ratios much greater than 10 at the dry site and 0.18 at the wet site during the daytime. These values remain reasonably constant from day-to-day. In the suburban area the partitioning between sensible, latent and storage heat fluxes is more equal (average daytime Bowen ratio 1.39). Unlike the sites the predominant flux is more variable from day-to-day; changing through the twelve day period between storage heat flux and sensible heat flux. The marked difference in energy partitioning between the two areas means that the site used as the rural reference for the definition of suburban-rura l flux differences and urban heat islands is significant.