Setup of tools and dataset selection for MBL investigation over a coastal (Mediterranean Sea) site. Preliminary results.

We propose the height zi of the inversion in the vertical profile of potential temperature, on the top of a mixed layer or of a residual layer as a relevant parameter for retrieving information related to water vapour in the lower layers of the atmosphere, from currently available operational satellites information. We estimated zi using an algorithm where a set of threshold values in the vertical gradients of potential temperature are used to analyse the available profiles in order to find relevant inversions. Thresholds are derived from the subjective analysis of a set of high vertical resolution soundings from the coastal site of the Italian Meteorological Service of Pratica di Mare (WMO #16245, lat. 41.66° N, lon. 12.45° E). The sensitivity of the method to vertical sampling is tested comparing results obtained by applying the method to two sets of about 6500 raw and sampled radiosoundings during the period 2002-2008. Differences in average seasonal and six-hourly values of zi from the two datasets are found within the range 5-10%. The method was then applied to a larger set of soundings from coastal and continental Mediterranean sites collected in a standard archive. It was found that mean summer values of zi at coastal sites are lower than in winter, conversely to continental sites. Furthermore, values of zi found using the proposed algorithm show a systematically higher inversion if compared to height found using the Richardson Number method, although there are cases when both identify the inversion at the same height.