Role of wind stress in driving SST biases in the Tropical Atlantic

Aurore Voldoire*, Eleftheria Exarchou, Emilia Sanchez-Gomez, Teferi Demissie, Anna Lena Deppenmeier, Claudia Frauen, Katerina Goubanova, Wilco Hazeleger, Noel Keenlyside, Shunya Koseki, Chloé Prodhomme, Jonathan Shonk, Thomas Toniazzo, Abdoul Khadre Traoré

*Corresponding author for this work

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3 Citations (Scopus)

Abstract

Coupled climate models used for long-term future climate projections and seasonal or decadal predictions share a systematic and persistent warm sea surface temperature (SST) bias in the tropical Atlantic. This study attempts to better understand the physical mechanisms responsible for the development of systematic biases in the tropical Atlantic using the so-called Transpose-CMIP protocol in a multi-model context. Six global climate models have been used to perform seasonal forecasts starting both in May and February over the period 2000–2009. In all models, the growth of SST biases is rapid. Significant biases are seen in the first month of forecast and, by 6 months, the root-mean-square SST bias is 80% of the climatological bias. These control experiments show that the equatorial warm SST bias is not driven by surface heat flux biases in all models, whereas in the south-eastern Atlantic the solar heat flux could explain the setup of an initial warm bias in the first few days. A set of sensitivity experiments with prescribed wind stress confirm the leading role of wind stress biases in driving the equatorial SST bias, even if the amplitude of the SST bias is model dependent. A reduced SST bias leads to a reduced precipitation bias locally, but there is no robust remote effect on West African Monsoon rainfall. Over the south-eastern part of the basin, local wind biases tend to have an impact on the local SST bias (except in the high resolution model). However, there is also a non-local effect of equatorial wind correction in two models. This can be explained by sub-surface advection of water from the equator, which is colder when the bias in equatorial wind stress is corrected. In terms of variability, it is also shown that improving the mean state in the equatorial Atlantic leads to a beneficial intensification of the Bjerknes feedback loop. In conclusion, we show a robust effect of wind stress biases on tropical mean climate and variability in multiple climate models.

Original languageEnglish
Pages (from-to)3481-3504
JournalClimate Dynamics
Volume53
Issue number5-6
Early online date13 Mar 2019
DOIs
Publication statusPublished - Sep 2019

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wind stress
sea surface temperature
climate modeling
heat flux
climate
global climate
advection
monsoon
experiment
rainfall
prediction
basin
effect

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Voldoire, A., Exarchou, E., Sanchez-Gomez, E., Demissie, T., Deppenmeier, A. L., Frauen, C., ... Traoré, A. K. (2019). Role of wind stress in driving SST biases in the Tropical Atlantic. Climate Dynamics, 53(5-6), 3481-3504. https://doi.org/10.1007/s00382-019-04717-0
Voldoire, Aurore ; Exarchou, Eleftheria ; Sanchez-Gomez, Emilia ; Demissie, Teferi ; Deppenmeier, Anna Lena ; Frauen, Claudia ; Goubanova, Katerina ; Hazeleger, Wilco ; Keenlyside, Noel ; Koseki, Shunya ; Prodhomme, Chloé ; Shonk, Jonathan ; Toniazzo, Thomas ; Traoré, Abdoul Khadre. / Role of wind stress in driving SST biases in the Tropical Atlantic. In: Climate Dynamics. 2019 ; Vol. 53, No. 5-6. pp. 3481-3504.
@article{e18948dab0fc47cd9cdc2cba170d4915,
title = "Role of wind stress in driving SST biases in the Tropical Atlantic",
abstract = "Coupled climate models used for long-term future climate projections and seasonal or decadal predictions share a systematic and persistent warm sea surface temperature (SST) bias in the tropical Atlantic. This study attempts to better understand the physical mechanisms responsible for the development of systematic biases in the tropical Atlantic using the so-called Transpose-CMIP protocol in a multi-model context. Six global climate models have been used to perform seasonal forecasts starting both in May and February over the period 2000–2009. In all models, the growth of SST biases is rapid. Significant biases are seen in the first month of forecast and, by 6 months, the root-mean-square SST bias is 80{\%} of the climatological bias. These control experiments show that the equatorial warm SST bias is not driven by surface heat flux biases in all models, whereas in the south-eastern Atlantic the solar heat flux could explain the setup of an initial warm bias in the first few days. A set of sensitivity experiments with prescribed wind stress confirm the leading role of wind stress biases in driving the equatorial SST bias, even if the amplitude of the SST bias is model dependent. A reduced SST bias leads to a reduced precipitation bias locally, but there is no robust remote effect on West African Monsoon rainfall. Over the south-eastern part of the basin, local wind biases tend to have an impact on the local SST bias (except in the high resolution model). However, there is also a non-local effect of equatorial wind correction in two models. This can be explained by sub-surface advection of water from the equator, which is colder when the bias in equatorial wind stress is corrected. In terms of variability, it is also shown that improving the mean state in the equatorial Atlantic leads to a beneficial intensification of the Bjerknes feedback loop. In conclusion, we show a robust effect of wind stress biases on tropical mean climate and variability in multiple climate models.",
author = "Aurore Voldoire and Eleftheria Exarchou and Emilia Sanchez-Gomez and Teferi Demissie and Deppenmeier, {Anna Lena} and Claudia Frauen and Katerina Goubanova and Wilco Hazeleger and Noel Keenlyside and Shunya Koseki and Chlo{\'e} Prodhomme and Jonathan Shonk and Thomas Toniazzo and Traor{\'e}, {Abdoul Khadre}",
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doi = "10.1007/s00382-019-04717-0",
language = "English",
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pages = "3481--3504",
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Voldoire, A, Exarchou, E, Sanchez-Gomez, E, Demissie, T, Deppenmeier, AL, Frauen, C, Goubanova, K, Hazeleger, W, Keenlyside, N, Koseki, S, Prodhomme, C, Shonk, J, Toniazzo, T & Traoré, AK 2019, 'Role of wind stress in driving SST biases in the Tropical Atlantic', Climate Dynamics, vol. 53, no. 5-6, pp. 3481-3504. https://doi.org/10.1007/s00382-019-04717-0

Role of wind stress in driving SST biases in the Tropical Atlantic. / Voldoire, Aurore; Exarchou, Eleftheria; Sanchez-Gomez, Emilia; Demissie, Teferi; Deppenmeier, Anna Lena; Frauen, Claudia; Goubanova, Katerina; Hazeleger, Wilco; Keenlyside, Noel; Koseki, Shunya; Prodhomme, Chloé; Shonk, Jonathan; Toniazzo, Thomas; Traoré, Abdoul Khadre.

In: Climate Dynamics, Vol. 53, No. 5-6, 09.2019, p. 3481-3504.

Research output: Contribution to journalArticleAcademicpeer-review

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AU - Voldoire, Aurore

AU - Exarchou, Eleftheria

AU - Sanchez-Gomez, Emilia

AU - Demissie, Teferi

AU - Deppenmeier, Anna Lena

AU - Frauen, Claudia

AU - Goubanova, Katerina

AU - Hazeleger, Wilco

AU - Keenlyside, Noel

AU - Koseki, Shunya

AU - Prodhomme, Chloé

AU - Shonk, Jonathan

AU - Toniazzo, Thomas

AU - Traoré, Abdoul Khadre

PY - 2019/9

Y1 - 2019/9

N2 - Coupled climate models used for long-term future climate projections and seasonal or decadal predictions share a systematic and persistent warm sea surface temperature (SST) bias in the tropical Atlantic. This study attempts to better understand the physical mechanisms responsible for the development of systematic biases in the tropical Atlantic using the so-called Transpose-CMIP protocol in a multi-model context. Six global climate models have been used to perform seasonal forecasts starting both in May and February over the period 2000–2009. In all models, the growth of SST biases is rapid. Significant biases are seen in the first month of forecast and, by 6 months, the root-mean-square SST bias is 80% of the climatological bias. These control experiments show that the equatorial warm SST bias is not driven by surface heat flux biases in all models, whereas in the south-eastern Atlantic the solar heat flux could explain the setup of an initial warm bias in the first few days. A set of sensitivity experiments with prescribed wind stress confirm the leading role of wind stress biases in driving the equatorial SST bias, even if the amplitude of the SST bias is model dependent. A reduced SST bias leads to a reduced precipitation bias locally, but there is no robust remote effect on West African Monsoon rainfall. Over the south-eastern part of the basin, local wind biases tend to have an impact on the local SST bias (except in the high resolution model). However, there is also a non-local effect of equatorial wind correction in two models. This can be explained by sub-surface advection of water from the equator, which is colder when the bias in equatorial wind stress is corrected. In terms of variability, it is also shown that improving the mean state in the equatorial Atlantic leads to a beneficial intensification of the Bjerknes feedback loop. In conclusion, we show a robust effect of wind stress biases on tropical mean climate and variability in multiple climate models.

AB - Coupled climate models used for long-term future climate projections and seasonal or decadal predictions share a systematic and persistent warm sea surface temperature (SST) bias in the tropical Atlantic. This study attempts to better understand the physical mechanisms responsible for the development of systematic biases in the tropical Atlantic using the so-called Transpose-CMIP protocol in a multi-model context. Six global climate models have been used to perform seasonal forecasts starting both in May and February over the period 2000–2009. In all models, the growth of SST biases is rapid. Significant biases are seen in the first month of forecast and, by 6 months, the root-mean-square SST bias is 80% of the climatological bias. These control experiments show that the equatorial warm SST bias is not driven by surface heat flux biases in all models, whereas in the south-eastern Atlantic the solar heat flux could explain the setup of an initial warm bias in the first few days. A set of sensitivity experiments with prescribed wind stress confirm the leading role of wind stress biases in driving the equatorial SST bias, even if the amplitude of the SST bias is model dependent. A reduced SST bias leads to a reduced precipitation bias locally, but there is no robust remote effect on West African Monsoon rainfall. Over the south-eastern part of the basin, local wind biases tend to have an impact on the local SST bias (except in the high resolution model). However, there is also a non-local effect of equatorial wind correction in two models. This can be explained by sub-surface advection of water from the equator, which is colder when the bias in equatorial wind stress is corrected. In terms of variability, it is also shown that improving the mean state in the equatorial Atlantic leads to a beneficial intensification of the Bjerknes feedback loop. In conclusion, we show a robust effect of wind stress biases on tropical mean climate and variability in multiple climate models.

U2 - 10.1007/s00382-019-04717-0

DO - 10.1007/s00382-019-04717-0

M3 - Article

VL - 53

SP - 3481

EP - 3504

JO - Climate Dynamics

JF - Climate Dynamics

SN - 0930-7575

IS - 5-6

ER -

Voldoire A, Exarchou E, Sanchez-Gomez E, Demissie T, Deppenmeier AL, Frauen C et al. Role of wind stress in driving SST biases in the Tropical Atlantic. Climate Dynamics. 2019 Sep;53(5-6):3481-3504. https://doi.org/10.1007/s00382-019-04717-0