MEAN MONTHLY DIURNAL CYCLES OBSERVED WITH PRESTORM SURFACE DATA

Data from 84 surface mesonetwork stations deployed across Oklahoma and Kansas are used to calculate monthly mean diurnal cycles at each meso network site during May and June of 1985 during the Preliminary Region al Experiment for Stormscale Operational and Research Meteorology (PRE -STORM). The horizontal variations in mean monthly temperatures and sp ecific humidities are large, even though this experimental domain cove rs only a portion of each state. Landscape differences cause much of t his variation, with the harvesting of winter wheat over a large region of Oklahoma in late May being one of the more clear factors influenci ng the surface layer cycles. A subjective classification of the mean m onthly diurnal cycles shows that the type of diurnal cycle changes as the vegetation changes. However, this relationship is strongly modifie d by the effects of convection. Results suggest that the mean diurnal cycles include the effects of convective downdrafts, indicating that t he interaction of convection with the atmospheric surface layer is an important process even on monthly timescales. This is important to con sider for those trying to evaluate regional climate simulations.