The Morning Inversion Near the Ground and Its Daytime Transition at Two Rural Sites in the Carolinas

Abstract

Abstract Six years of tower data from two dissimilar sites in the eastern piedmont of the Carolinas are analyzed to yield a selective climatology of the lower portion of the morning inversion. Its transition to daytime conditions is then described and statistically modeled. Both sites are in clearings surrounded by forest, but one site is in a valley by a lake, while the other, 175 km to the north, is on a low hilltop. Measurements of wind speed and direction, the standard deviation of wind direction, dew point, and temperature at 11 m, temperature difference (ΔT) between 11 and 60 m, plus solar radiation, were analyzed for an 8-h period starting from three hours before local sunrise each day for both locations. Results show that predawn inversions characterize over 70% of the data and strong inversions of over 5°C per 100 m in the tower layer characterize 30% of the mornings at the hilltop site. At the valley site, strong inversions are less common, probably because of the proximity of the lake. There is...