As paleoclimatic studies indicate a high unstability, any reduction of the low-level cloud cover due to climate change may represent a major tipping-point for forest cover and functioning, but so far the few existing studies on the region have concentrated on the rainy seasons. Therefore there is an urgent need to better understand the presence, variability and bioclimatic effects of the low-level cloud cover in western Central Africa in the current climate and to provide a robust assessment of its future evolution under climate change. This constitutes the main aims of the DYVALOCCA project funded over 2020-2022 by the ANR and the DFG.

To achieve its aims, DYVALOCCA is based on an international consortium composed of French, German and Gabonese partners including meteorologists, climatologists, atmospheric modelers ( as well as external collaborators from UK, US and Belgium with an expertise in clouds remote sensing and forests functioning). The consortium will conduct a field campaign, acquire existing in-situ observations and utilize satellite and re-analyses data for diagnostic and modeling analyses.

The meteorological processes (WP3) driving the low cloud cover formation and dissolution at the diurnal scale will be studied from the synergistic analysis of historical in-situ data, a dedicated field campaign in July-August 2021 and atmospheric modeling activities. A focus will be put on ocean-land transects to determine the extent to which processes are different between the coastal plains, the windward slopes of the Chaillu mountains and inland plateaus. Results will be compared to a recently developed conceptual model for LCC over southern West Africa.

The intraseasonal to interannual variability of the low cloud cover (WP4) will be characterized from the analysis of long-term in-situ data and satellite estimates. Variations in the timing, i.e. seasonal onset and retreat as well as intraseasonal breaks, and in the inland extent of the low cloud cover will be documented. The atmospheric and oceanic forcings at play will be explored. The impact of local to regional sea surface temperatures on the low cloud cover development and interannual variability will be assessed, coupling statistical analyses and dedicated sensitivity experiments with a regional climate model.

Lastly the effect of low clouds on light and water availability on forest functioning (WP5) will be explored based on in-situ measurements. Results will be compared with those obtained from measurements in northern Congo, where the dry season is sunny, and with outputs from a simple two-reservoirs water balance model adapted for the region.