FN Archimer Export Format
PT J
TI The asymmetric influence of ocean heat content on ENSO predictability in the CNRM-CM5 coupled general circulation model
BT 
AF Planton, Yann Y.
   Vialard, Jérôme
   Guilyardi, Eric
   Lengaigne, Matthieu
   McPhaden, Michael J.
AS 1:1;2:1;3:1,2;4:1,3;5:4;
FF 1:;2:;3:;4:;5:;
C1 LOCEAN-IPSL, CNRS-IRD-MNHN-Sorbonne Université, Paris, France
   NCAS-Climate, University of Reading, UK
   MARBEC, University of Montpellier, CNRS, IFREMER, IRD, Sète, France
   NOAA/Pacific Marine Environmental Laboratory, Seattle, WA, USA
C2 IPSL, FRANCE
   UNIV READING, UK
   IRD, FRANCE
   NOAA, USA
UM MARBEC
IN WOS Cotutelle UMR
   copubli-france
   copubli-europe
   copubli-int-hors-europe
IF 5.38
TC 9
UR https://archimer.ifremer.fr/doc/00694/80616/83870.pdf
LA English
DT Article
DE ;Pacific Ocean;Atmosphere-ocean interaction;ENSO;Seasonal forecasting;Climate models;Interannual variability
AB Unusually high western Pacific oceanic heat content often leads to El Niño about 1 year later, while unusually low heat content leads to La Niña. Here, we investigate if El Niño Southern Oscillation (ENSO) predictability also depends on the initial state recharge, and discuss the underlying mechanisms. To that end, we use the CNRM-CM5 model, which has a reasonable representation of the main observed ENSO characteristics, asymmetries and feedbacks. Observations and a 1007-years long CNRM-CM5 simulation indicate that discharged states evolve more systematically into La Niña events than recharged states into neutral states or El Niño events. We ran 70-members ensemble experiments in a perfect-model setting, initialized in boreal fall from either recharged or discharged western Pacific heat content, sampling the full range of corresponding ENSO phases. Predictability measures based both on spread and signal-to-noise ratio confirm that discharged states yield a more predictable ENSO outcome one year later than recharged states. As expected from recharge oscillator theory, recharged states evolve into positive central Pacific sea surface temperature anomalies in boreal spring, inducing stronger and more variable Westerly Wind Event activity and a fast growth of the ensemble spread during summer and fall. This also enhances the positive wind stress feedback in fall, but the effect is offset by changes in thermocline and heat flux feedbacks. The state-dependent component of westerly wind events is thus the most likely cause for the predictability asymmetry in CNRM-CM5, although changes in the low-frequency wind stress feedback may also contribute. 
PY 2021
PD JUN
SO Journal Of Climate
SN 0894-8755
PU American Meteorological Society
VL 34
IS 14
UT 000668206100010
BP 5775
EP 5793
DI 10.1175/JCLI-D-20-0633.1
ID 80616
ER

EF