Comparison of ABL Heights

This study investigates two approaches for determining the height of the Atmospheric Boundary Layer (ABL): analyzing radio occultation (RO) observations and using NOAA's Rapid Update Cycle (RUC) model. The first approach determines the ABL height by examining radio wave bending angle profiles from the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC). The second approach examines the vertical structure of meteorological parameters reproduced by the RUC model. This study compares the values of collocated ABL heights obtained by each approach over the North America and adjacent ocean for both summer and winter months to determine seasonal variations. Significant differences in the ABL heights were found for the two approaches, as well as seasonal variations. High-precision comparisons were not produced between RUC and COSMIC ABL heights, because this ABL analysis did not include RUC model data for water vapor and turbulence. To perform a better comparison, the RUC ABL should be better characterized by accounting for water vapor and turbulent mixing data. Both methods measure the ABL, but they measure different parts of the ABL. COSMIC is measuring where the strongest decrease in water vapor and humidity occurs. RUC on the other hand just reports the height that fits its definition this might not always be the true ABL height. This chart shows why the RUC and COSMIC methods may be producing different results for the ABL heights.You can see that the temperature stays constant with increasing altitude, then there is a decrease but it smoothes back out to a constant temperature, then it decreases again. Since the RUC model only reports the first height that fits its definition, it marks the first decrease it as the ABL height—but COSMIC may take the second decrease due to the strong inversion layer