Observations of frontal zone and tropopause structures with a VHF Doppler radar and radiosondes

Since March 1977 the SOUSY (Sounding System) VHF radar has been used to make a series of frontal passage observations in the spring and fall. The radar operates at a wavelength of 5.6 m and thus is sensitive to the temperature structure of the atmosphere. It has already been shown that VHF radars can be used to determine the location of the tropopause, for instance. We present data from five separate experiments showing that the reflectivity data can also be used to determine the location of tropopause breaks and frontal boundaries between the surface and the tropopause. In each case, we compare the reflectivities measured with the radar and the potential refractivity gradient calculated using radiosonde data from a nearby station. There is good agreement between the calculated and observed values, although the radar data show more detailed structure due to the much higher time resolution.