Where Does Moisture Come From for Rainfall over the Congo Basin?
Abstract
The Congo Basin hosts the third largest global center of terrestrial rainfall and the second largest contiguous rainforest. However, it is not clear whether moisture transport from the adjacent oceans or evapotranspiration (ET) is the primary source of water vapor in Congo basin (5°S-5°N, 15°-30°E). Through a joint use of multiple satellite observations over the period 2005-2011, including the deuterium content of water vapor (HDO/H2O ratio or δD), water vapor mixing ratio in the free troposphere (qFT), solar induced fluorescence (SIF, an indicator of the photosynthesis), and precipitation (P), along with atmospheric reanalysis, we evaluate the seasonal contribution of ET to lower-tropospheric atmospheric moisture, a key pre-cursor for precipitation. We find that SIF covaries with the spring and autumn Congo basin rainy seasons, indicating that photosynthesis and subsequent evapotranspiration contribute to both rainy seasons. However, δD values, moisture transport and ET from the re-analysis, and SIF together indicate that ET is the primary source of qFT during the boreal winter dry and spring rainy seasons, with relatively decreasing contributions of ET during the boreal summer dry season and boreal autumn rainy season. A comparison of this deuterium content relative to simple isotope models that describe mixing of air parcels from an ocean or land source find that 69% ±14% of the air parcels likely originate from a land source prior to the spring season whereas 42% ± 13% of the observed air parcels are likely from a land source prior to the fall season. This change in the relative contribution of ET is qualitatively consistent with the re-analysis.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMB046.0013W
- Keywords:
-
- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0495 Water/energy interactions;
- BIOGEOSCIENCES