Weakened seasonality of the African rainforest precipitation in boreal winter and spring driven by tropical SST variabilities
Precipitation in the equatorial African rainforest plays an important role in both the regional hydrological cycle and the global climate variability. Previous studies mostly focus on the trends of drought in recent decades or long-time scales. Using two observational datasets, we reveal a remarkable weakening of the seasonal precipitation cycle over this region from 1979 to 2015, with precipitation significantly increased in the boreal winter dry season (+ 0.45 mm/day) and decreased in the boreal spring wet season (-0.78 mm/day), which account for ~ 14% of their respective climatological means. We further use a state-of-the-art atmospheric model to isolate the impact of sea surface temperature change from different ocean basins on the precipitation changes in the dry and wet seasons. Results show that the strengthening precipitation in the dry season is mainly driven by the Atlantic warming, whereas the weakening precipitation in the wet season can be primarily attributed to the Indian Ocean. Warming Atlantic intensifies the zonal circulation over the African rainforest, strengthening moisture convergence and intensifying precipitation in the boreal winter dry season. Warming Indian Ocean contributes more to reducing the zonal circulation and suppressing the convection in the boreal spring wet season, leading to an opposite effect on precipitation. This result has important implication on local ecology as well as global climate system.
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Posted 23 Sep, 2020
On 06 Dec, 2020
Received 05 Dec, 2020
Received 01 Nov, 2020
On 05 Oct, 2020
Invitations sent on 23 Sep, 2020
On 23 Sep, 2020
On 18 Sep, 2020
On 18 Sep, 2020
On 17 Sep, 2020
On 17 Sep, 2020
Weakened seasonality of the African rainforest precipitation in boreal winter and spring driven by tropical SST variabilities
Posted 23 Sep, 2020
On 06 Dec, 2020
Received 05 Dec, 2020
Received 01 Nov, 2020
On 05 Oct, 2020
Invitations sent on 23 Sep, 2020
On 23 Sep, 2020
On 18 Sep, 2020
On 18 Sep, 2020
On 17 Sep, 2020
On 17 Sep, 2020
Precipitation in the equatorial African rainforest plays an important role in both the regional hydrological cycle and the global climate variability. Previous studies mostly focus on the trends of drought in recent decades or long-time scales. Using two observational datasets, we reveal a remarkable weakening of the seasonal precipitation cycle over this region from 1979 to 2015, with precipitation significantly increased in the boreal winter dry season (+ 0.45 mm/day) and decreased in the boreal spring wet season (-0.78 mm/day), which account for ~ 14% of their respective climatological means. We further use a state-of-the-art atmospheric model to isolate the impact of sea surface temperature change from different ocean basins on the precipitation changes in the dry and wet seasons. Results show that the strengthening precipitation in the dry season is mainly driven by the Atlantic warming, whereas the weakening precipitation in the wet season can be primarily attributed to the Indian Ocean. Warming Atlantic intensifies the zonal circulation over the African rainforest, strengthening moisture convergence and intensifying precipitation in the boreal winter dry season. Warming Indian Ocean contributes more to reducing the zonal circulation and suppressing the convection in the boreal spring wet season, leading to an opposite effect on precipitation. This result has important implication on local ecology as well as global climate system.
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9