Sea surface temperature (SST)
anomalies during July 2009 remained above average across the equatorial
all of the Niņo-region SST
indices were between +0.6°C to +1.0°C throughout the month
The oceanic thermocline along
the equator, measured by the depth of the 20°C
isotherm, remained deeper than average across the equatorial
(Figs. T15, T16).
Consistent with these conditions, temperatures were 1o-4oC
above average at thermocline depth across the equatorial Pacific (Fig. T17).
during July, convection was suppressed over
and enhanced across the
western Pacific and near the Date Line (Figs.
This coupling of the oceanic and atmospheric anomalies reflects El Niņo
200-hPa streamfunction field indicates El Niņo was impacting the upper-level
circulation during July in both the subtropics and extratropics. The impacts
were strongest in the winter (i.e., Southern) hemisphere, where they extended
from the subtropical South Pacific well into the higher latitudes (Fig.
the SH, the subtropical ridge was stronger than average across the central South
Pacific and weaker then average over the
. This circulation
reflected an overall eastward extension/ shift of the mean subtropical ridge,
and is consistent with the El Niņo-related pattern of anomalous tropical
convection. These conditions were also associated with an eastward extension of
the South Pacific jet stream, and with an eastward shift of the jet core to the
date line (Fig. T21).
500-height field shows the El Niņo impacts extending well into the SH high
latitudes, as indicated by an extensive area of negative anomalies across the
central South Pacific and positive anomalies over the high latitudes of the
eastern South Pacific (Fig. E15).
Another El Niņo impact seen during July was cyclonic streamfunction anomalies
in the extratropics of both hemispheres, as indicated by negative values in the
NH and positive values in the SH (Fig. T22).
This pattern is opposite to that seen earlier in the year in association with La
the latest status of the ENSO cycle see the ENSO Diagnostic Discussion at: