Water vapour isotopes over West Africa as observed from space: which processes control tropospheric H2O/HDO pair distributions?

• DOI: 10.5194/egusphere-2024-1613
• Publication Date: 2024-08-16T06:49:06Z
• Authors: Christopher Johan...; Matthias Schneider; Peter Knippertz; Tim Trent; Hartmut Boesch; Amelie Ninja Roeh...; John Worden; Benjamin Ertl; Farahnaz Khosrawi; Frank Hase
• Keywords: Water cycle

Abstract. The West African Monsoon (WAM) represents the main source of rainfall over Africa and thus has important socio-economic impacts. However, complex interactions large-scale circulation, convective dynamics microphysical processes pose a substantial challenge to reliably quantify atmospheric branches hydrological cycle in observations models. Making use recent advances retrieving isotopic composition tropospheric water vapour from space, we promote paired analysis H2O HDO investigate moisture pathways associated with WAM. Data state-of-the-art satellite sensors IASI, AIRS TROPOMI, together multi-satellite IMERG precipitation product, serve characterize variability (with their ratio product δD) as well seasonal perspective respect impacts dynamical processes. In particular, find: (1) convection Sahel leads marked anti-correlation between increasing decreasing δD free troposphere. This is due strong dry air intrusions Saharan upper troposphere that feed into Sahelian squall line systems, foster rain evaporation and, hence, lead depletion; (2) Over Guinea Coast, overall moist enriched signals without showing significant depletion. Here, surface Tropical Atlantic moistens troposphere, reducing efficiency corresponding (3) During monsoon peak, an amount becomes apparent. Thus, this provides observational evidence for effect vapour, similar what known precipitation; (4) When no considerable occurs, e.g. during winter, {H2O, δD} point mass mixing circulation. study demonstrates different occurring leave distinct features underlines value using space effects control tropical convection.