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Research Letter
Weakened seasonality of the African rainforest precipitation in boreal winter and spring driven by tropical SST variabilities
Xichen Li
Institute of Atmospheric Physics Chinese Academy of Sciences
Corresponding Author
ORCiD: https://orcid.org/0000-0001-6325-6626
License:
This work is licensed under a CC BY 4.0 License. Read Full License
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.
Keywords
seasonality of precipitation, African rainforest, Walker Circulation, convergence of moisture
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CURRENT STATUS: Under Review
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On 06 Dec, 2020
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Received 05 Dec, 2020
Review #1 received
Received 01 Nov, 2020
Reviewer #2 agreed
On 05 Oct, 2020
Reviewers invited
Invitations sent on 23 Sep, 2020
Reviewer #1 agreed
On 23 Sep, 2020
First submitted
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On 18 Sep, 2020
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This preprint is under consideration at Geoscience Letters. A preprint is a preliminary version of a manuscript that has not completed peer review at a journal. Research Square does not conduct peer review prior to posting preprints. The posting of a preprint on this server should not be interpreted as an endorsement of its validity or suitability for dissemination as established information or for guiding clinical practice.
Learn more about In Review
Research Letter
Weakened seasonality of the African rainforest precipitation in boreal winter and spring driven by tropical SST variabilities
Xichen Li
Institute of Atmospheric Physics Chinese Academy of Sciences
Corresponding Author
ORCiD: https://orcid.org/0000-0001-6325-6626
Badges
Prescreen
This manuscript passed our Prescreen assessment
Complete author information
Appropriate declaration statements
Potential risks to human health
Prescreen
Peer Review Timeline
CURRENT STATUS: Under Review
Version 1
Posted 23 Sep, 2020
No community comments so far
Editorial decision: Major Revision
On 06 Dec, 2020
Review #2 received
Received 05 Dec, 2020
Review #1 received
Received 01 Nov, 2020
Reviewer #2 agreed
On 05 Oct, 2020
Reviewers invited
Invitations sent on 23 Sep, 2020
Reviewer #1 agreed
On 23 Sep, 2020
First submitted
On 18 Sep, 2020
Editor assigned
On 18 Sep, 2020
Submission checks complete
On 17 Sep, 2020
Editor invited
On 17 Sep, 2020
Metrics
Comments: 0
PDF Downloads: ...
HTML Views: ...
License:
This work is licensed under a CC BY 4.0 License. Read Full License
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