Overview of observations from the RADAGAST experiment in Niamey, Niger: Meteorology and thermodynamic variables

Abstract

[1] An overview is presented of the meteorological and thermodynamic data obtained during the Radiative Atmospheric Divergence using Atmospheric Radiation Measurement (ARM) Mobile Facility, Geostationary Earth Radiation Budget (GERB) data, and African Monsoon Multidisciplinary Analysis (AMMA) stations (RADAGAST) experiment in Niamey, Niger, in 2006. RADAGAST combined data from the ARM Program Mobile Facility (AMF) at Niamey airport with broadband satellite data from the GERB instrument on Meteosat-8. The experiment was conducted in collaboration with the AMMA project. The focus in this paper is on the variations through the year of key surface and atmospheric variables. The seasonal advance and retreat of the Intertropical Front and the seasonal changes in near-surface variables and precipitation in 2006 are discussed and contrasted with the behavior in 2005 and with long-term averages. Observations from the AMF at Niamey airport are used to document the evolution of near-surface variables and of the atmosphere above the site. There are large seasonal changes in these variables, from the arid and dusty conditions typical of the dry season to the much moister and more cloudy wet season accompanying the arrival and intensification of the West African monsoon. Back trajectories show the origin of the air sampled at Niamey and profiles for selected case studies from rawinsondes and from a micropulse lidar at the AMF site reveal details of typical atmospheric structures. Radiative fluxes and divergences are discussed in the second part of this overview, and the subsequent papers in this special section explore other aspects of the measurements and of the associated modeling.

ECMWF Atmospheric Profiles in Maroua, Cameroon: Analysis and Overview of the Simulation of Downward Global Solar Radiation

“…However, further investigations are necessary, knowing that the determination of the effective start of the rainy season is capital for sowing in such regions. The analysis of the ECMWF atmospheric profiles shows that the Maroua atmosphere state and dynamics present many similarities with what was reported in some studies in West Africa, a neighboring zone [9,11,47,48]. Adding to this, the good correlation coefficients obtained between ECMWF and measured meteorological data at ground level show the capacity of ECMWF profiles to characterize the Maroua atmosphere and therefore show the possibility to use these in solar radiation simulation.…”

“…With the arrival of the monsoon flux during the wet season, it was shifted northward (negative anomaly of U wind) and was replaced in the mid-troposphere by the AEJ between May and October, as noticed in Niamey in 2006 [11]. These phenomena, previously detected in Niamey in 2006 and largely explained in [9], presented in Maroua a temporal shift of about 2 weeks. This delay could be due to the 12 year difference between the two databases used.…”

Measurements of aerosol properties from aircraft, satellite and ground‐based remote sensing: a case‐study from the Dust and Biomass‐burning Experiment (DABEX)

“…The ARM Mobile Facility (AMF) was stationed at Niamey Airport throughout 2006 (Miller and Slingo, 2007;Slingo et al, 2008). AODs were estimated by the MFRSR which measures solar irradiance at six wavelengths (415, 500, 615, 673, 870 and 940 nm).…”

Characterizing energy budget variability at a Sahelian site: a test of NWP model behaviour

“…We refer the reader elsewhere for further, in-depth details (e.g. Slingo et al, 2008Slingo et al, , 2009). The incident solar radiation (TSI) enters the top of the atmosphere.…”