Inter-comparison of AIRS temperature and relative humidity profiles with
AMMA and DACCIWA radiosonde observations over West Africa
Abstract
The vertical profiles of temperature and water vapour from the
Atmospheric InfraRed Sounder (AIRS) have been validated across various
regions of the globe as an effort to provide a substitute for radiosonde
observations. But there is a paucity of inter-comparisons over West
Africa where local convective processes dominate and RAOBs are limited.
This study validates AIRS temperature and relative humidity profiles for
selected radiosonde stations in West Africa. Radiosonde data was
obtained from the AMMA and DACCIWA campaigns which spanned 2006 - 2008
and June-July 2016 respectively and offered a period of prolonged
radiosonde observations in West Africa. AIRS performance was evaluated
with the bias and root mean square difference (RMSD) at seven RAOB
stations which were grouped into coastal and inland. Evaluation was
performed on diurnal and seasonal timescales, cloud screening conditions
and derived thunderstorm instability indices. At all timescales, the
temperature RMSD was higher than the AIRS accuracy mission goal of ±1 K.
Relative humidity RMSD was satisfactory for the entire troposphere with
deviations < 20% and < 50% respectively. AIRS
retrieval of water vapour under cloudy and cloud-free conditions had no
significant difference whereas cloud-free temperature was found to be
more accurate. The seasonal evolution of some thunderstorm convective
indices were also found to be comparable for AIRS and RAOB. The ability
of AIRS to capture the evolution of these indices imply its
applicability for determining the thunderstorm probability over West
Africa under the Global Challenges Research Fund African Science for
Weather Information and Forecasting Techniques project.