Risi C., Bony S., Vimeux Françoise, Chong M., Descroix Luc. (2010). Evolution of the stable water isotopic composition of the rain sampled along Sahelian squall lines. Quarterly Journal of the Royal Meteorological Society, 136 (s1), p. 227-242. ISSN 0035-9009.
Titre du document
Evolution of the stable water isotopic composition of the rain sampled along Sahelian squall lines
Risi C., Bony S., Vimeux Françoise, Chong M., Descroix Luc
Source
Quarterly Journal of the Royal Meteorological Society, 2010,
136 (s1), p. 227-242 ISSN 0035-9009
In the Tropics. the stable isotopic composition (HDO, (H2O)-O-18) of precipitation is strongly modulated by convective activity To better understand how convective processes impact the precipitation isotopic composition, we analyze the isotopic composition of rain collected during the passage of four squall lines over the Sahel (Niamey. Niger) in August 2006 during the African Monsoon Multidisciplinary Analysis (MAMA) campaign The high-frequency sampling (5-10 mm) of the preciptation allows us to Investigate the evolution of the precipitation isotopic composition in different phases of the squall lines Despite a large variability among the different squall lines, some robust isotopic features appear the W shape of the delta O-18 evolution and the deuterium excess decrease in the first part of the sit:inform zone To understand more quantitatively how convective processes impact the precipitation isotopic composition. a simple stationary two-dimensional transport model including a representation of cloud microphysics and isotopic fractionation is developed and forced by three-dimensional winds retrieved from the Massachusetts Institute of Technology (MIT) radar on 11 August 2006 The model reproduces the robust observed features and a large sensitivity to the squall-line dynamics This model suggests that the main controlling factors of the isotopic evolution ale (1) squall-line dynamics. especially the downward advection of an at the rear of the squall lines, affecting the vapour composition and, by isotopic equilibration. the subsequent precipitation composition and (2) rain re-evaporation This suggests that water isotopes have the potential to better constrain squall-line dynamics and rain re-evaporation, and to evaluate the representation of convective processes in numerical models Copyright (C) 2009 Royal Meteorological Society
Plan de classement
Sciences du milieu [021]
;
Limnologie physique / Océanographie physique [032]
