Upper and middle precipitable water calculated from METEOSAT-8/-9 tropospheric humidity and NCEP/NCAR temperatures

The aim of this work is the estimation and the analysis of precipitable water in the middle-upper troposphere (850 hPa–300 hPa), obtained through Meteosat-8/-9 tropospheric humidity products, together with air temperature data, from NCEP/NCAR daily global reanalysis 1. The period of observation goes from 1st February 2004 to 30th November 2008, on a regular grid of 2.5° × 2.5° resolution, over Meteosat-8/-9 area, included between about 63°N–63°S of latitude and between about 63°W–63°E of longitude.Daily averages of tropospheric humidity products have been checked with two data sets: the first one was vertically averaged relative humidity from 97 Integrated Global Radiosonde Archive (IGRA) stations, the second one was relative humidity averaged from NCEP/NCAR daily global reanalysis 1. These comparisons have shown an underestimation of Meteosat relative humidity data respect the radiosounding data, in particular in the middle layer (850–600 hPa).Estimated middle-upper tropospheric precipitable water has shown a general coherence with typical climatological values representing about 30–45% of whole precipitable water in the same area. Linear trends for middle-upper troposphere shows values comprised between − 1.0 kg m− 2 yr− 1 and 0.2 kg m− 2 yr− 1, with bigger values (up to − 1.6 kg m− 2 yr− 1) mainly in the equatorial area, over South America. Hovmöller analysis underline mainly the middle-upper precipitable water seasonality with maximum values oscillating around the equator, following ITCZ migration, more marked over land than over the Ocean, from North to South.