Morphology and forcing of intra-seasonal Kelvin waves in the tropical Atlantic. Irene Polo (Univ. Complutense Madrid) Alban Lazar (LOCEAN-IPSL) Belen Rodriguez-Fonseca (Univ. Complutense Madrid) Sabine Arnault et Gildas Mainsant (LOCEAN-IPSL) I. Morphology Paper in revision for JGRocean II. Forcings

SSH Variability Hovmuller diagrams for the SSH T/P interannual anomalies (cm), equator and northern African coast (left), and equator and southern African coast (right

25-95 day time filtered T/P SSH, equator and N & S coasts Hovmuller diagrams for the time- filtered SLA T/P anomalies (in cm) for the equator and the northern African coast.

Speed estimates by Radon transform of 25-95d bpf T/P SSH m/s ~2,5 m/s ~1 m/s ~2 m/s

Untill where do the Kelvin waves impact the ssh ? Lagged correlation along the wave tracks of 10-60d bpf T/P SSH

Untill where do the Kelvin waves impact the ssh ? Lagged correlation along the wave tracks of 25-95d bpf T/P SSH ~12°N 12°S Remote forcing vanishes

Coastal wind forcing dominates poleward of ~12°N/S ~12°N 12°S NORTH r (dSSH/dt OGCM, tau//) ssh and along shore wind stress correlation NORTH r (dSSH/dt obs, tau//) SOUTH r (dSSH/dt OGCM, tau//) SOUTH r (dSSH/dt obs, tau//) 70% variability from local wind low latitude up to 70% variability remotely control Coasts: Local wind forcing dominates Local wind forcing dominates Large remote forcing

Figure 3. Climatology of the SSH intraseasonal anomalies (in cm), for observations (shaded areas) and the model (contour lines), along the northern track (left) and the southern track (right). Phase locking: climatology of the bpf T/P SSH A Climatological Intraseasonal Kelvin Wave (CIKW)

A Complex EOF analysis of the winter bpf SSH (obs) An Intraseasonal Winter Kelvin Wave (IWKW) mode PC EEOF

An Intraseasonal Winter Kelvin Wave (IWKW) mode

Equatorial wind forcing : where ? r (dSSH/dt OGCM, tauX) ssh and wind stress r (dSSH/dt obs, tauX) r (dSSH/dt OGCM, tauY) r (dSSH/dt obs, tauY)

Equatorial wind forcing : where ? r (dSSH/dt OGCM, tauX) ssh and wind stress r (dSSH/dt obs, tauX) r (dSSH/dt OGCM, tauY) r (dSSH/dt obs, tauY) Eastern equatorial wind not much in control of the situation

Equatorial wind forcing : where ? r (dSSH/dt OGCM, tauX) ssh and wind stress r (dSSH/dt obs, tauX) r (dSSH/dt OGCM, tauY) r (dSSH/dt obs, tauY) Western equatorial wind neither in control of the situation Eastern equatorial wind not much in control of the situation OFF-EQUATORIAL FORCING?

Western off-equatorial large scale wind forcing : a winter 1998 example Ekman pumping OLR

Western off-equatorial large scale wind forcing associated to the IWKW mode: southwestward propagating signal originating in the northern mid-latitudes

-coastally trapped waves are among us! they can not hide anymore, thanks to satellite data -winter phase locked intraseasonal KW mode -intraseasonal forcing at basin scale coming from the mid-latitudes ? Perspectives: climact (and biology) impacts: thursday