Surface Bowen Ratio Research Articles

The Humidity and Temperature Sensitivity of Clear-Air Radars in the Convective Boundary Layer

Abstract A top-down/bottom-up diffusion Model is used to evaluate the relative contributions of humidity temperature, and their cross correlation to the radar refractive index structure function paramer Cn2 in the cloud-free, convective planetary boundary layer (PBL). Profiles of Cn2 can be measured continuously in the clear air with Doppler radars. Extraction of information about PBL dynamical parameters is more straightforward if Cn2 is dominated by either moisture (Cq2) or temperature (CT2). In the lower part of the PBL the surface Bowen ratio β0 determines this dominance. In the upper part of the PBL the inversion Bowen ratio β1 is the primary determining factor. The model suggests that humidity accounts for at least 75% of Cn2 over tropical and midlatitude oceans. Polar oceans, where β0 often exceeds 0.5, may not be dominated by either temperature or moisture. Over land β0 can easily vary from 0.1 to 10. Geographical regions with β0 5 wil...

How Similar are Temperature and Humidity Profiles in the Unstable Boundary Layer?

A comparison was made between temperature and humidity profiles obtained from radiosonde measurements under unstable conditions over hilly terrain in northeastern Kansas during the summer and fall of 1987. The summer profiles were found to be similar in a layer over the height range given by z = 65(plus or minus 45) to 124(plus or minus 54)m, where z is the height above the ground surface reference level. Evidence for this similarity was the closeness of the scaled ratio of the temperature and humidity gradients at any given time to the mean Bowen ratio determined at ground-based surface flux stations. Above the layer, in the outer region of the atmospheric boundary layer, it was found that the profiles of humidity and potential temperature are completely dissimilar in terms of the surface Bowen ratio. The profiles of the fall campaign when soil moisture content was low and vegetation senescent displayed a less pronounced similarity.