Mount Rwenzori (4750 m a.s.l., Uganda): meteorological characterization and Air-Mass transport analysis

Abstract

The meteorological conditions at Mount Rwenzori (RWZ), in Western Uganda, are explored by analysing meteorological observations carried out during the years 2006-2009 by an Automatic Weather Station (AWS) installed at 4750 m a.s.l. in the eastern part of the Mount Stanley (0° 22’ N and 29° 52’ E), the most extensive RWZ glacial mass. The AWS provides hourly measurements of the main meteorological variables: air temperature, rain precipitation, atmospheric pressure, relative humidity, wind speed and direction, and global short-wave irradiance. In this work we described the typical seasonal and diurnal variations of the meteorological parameters recorded during the period October 2006 – August 2007 and July 2008 – June 2009. Throughout these periods, a remarkable low variability of the main meteorological parameters is detected, as expected for an equatorial high-altitude site. Only for the rain precipitation amount a direct influence of the Inter Tropical Convergence Zone (ITCZ) can be detected. As deduced by the analysis of the typical seasonal diurnal variations, the local mountain weather regime is likely to dominate the variability of the meteorological parameters at RWZ. These measurements permitted to characterize for the first time the meteorological conditions of the Rwenzori Mountains. In addition, the Lagrangian model HYSPLIT has been used to calculate a 2-year climatology of three-dimensional air-mass back-trajectories in order to provide a description of the synoptic-scale atmospheric circulation affecting the measurement site, and verify the seasonal influence of the ITCZ on large-scale atmospheric circulation at RWZ.