Surface response to rain events throughout the West African monsoon.

Fabienne Lohou (1) , Laurent Kergoat (2) , F. Guichard (3) , A. Boone (3) , B. Cappelaere (4) , J.M. Cohard (5) , J. Demarty (4) , S. Galle (5) , Manuela Grippa (2) , C. Peugeot (4) , D. Ramier (6) , C.M. Taylor (7) , Franck Timouk (2)

1 LAERO - Laboratoire d'aérologie
2 GET - Géosciences Environnement Toulouse
3 CNRM - Centre national de recherches météorologiques
4 HSM - Hydrosciences Montpellier
5 LTHE - Laboratoire d'étude des transferts en hydrologie et environnement
6 CETE Ile-de-France - Centre d'études techniques de l'équipement Ile-de-France
7 CEH - Centre for Ecology and Hydrology [Wallingford]

This study analyses the response of the continental surface to a rain event, taking advantage of the long-term near-surface measurements over different vegetation covers at different latitudes, acquired during the African Monsoon Multidisciplinary Analysis (AMMA) experiment. The simulated surface response by nine land surface models involved in AMMA Land Model Intercomparison Project (ALMIP), is compared to the observations. The surface response, described via the evaporative fraction, evolves in two steps: the immediate surface response and the surface recovery. The immediate surface response corresponds to an increase in the evaporative fraction occurring immediately after the rain. For all the experimental sites, the immediate surface response is strongest when the surface is relatively dry. From the simulation point of view, this relationship is highly model and latitude dependent. The recovery period, characterized by a decrease of the evaporative fraction during several days after the rain, follows an exponential relationship whose rate is vegetation dependent: from 1 day over bare soil to 70 days over the forest. Land surface models correctly simulate the decrease of EF over vegetation covers whereas a slower and more variable EF decrease is simulated over bare soil

Domaines: Physique Atmosphérique et Océanique [physics.ao-ph]

Fabienne Lohou, Laurent Kergoat, F. Guichard, A. Boone, B. Cappelaere, et al.. Surface response to rain events throughout the West African monsoon.. Atmospheric Chemistry and Physics Discussions, 2013, 13 (7), pp.18581-1/8620. ⟨10.5194/acpd-13-18581-2013⟩. ⟨hal-00965406⟩