I’ve moved to WordPress. This post can now be found at Mid-August 2010 SST Anomaly Update#########################
NOTE: The weekly OI.v2 SST data is available in two periods through the NOAA NOMADS website, from November 1981 to 1989, and from 1990 to present. The mid-month posts now include the full term of the NINO3.4 and Global SST anomalies from 1990 to present and a shorter-term view from 2004 to present to make the recent wiggles easier to see.
NINO3.4 SST anomalies for the week centered on August 18, 2010 show that central equatorial Pacific SST anomalies have reached an initial plateau. Presently they’re at -1.1 deg C, which is 0.21 deg C higher than the lowest value that occurred three weeks ago.
NINO3.4 SST Anomalies
NINO3.4 SST Anomalies - Short-Term
Weekly Global SST anomalies are still elevated and are firmly planted in a mid-year stall. They don’t appear to want to rise or fall. Will they make a sizable drop as they had during 2007?
Global SST Anomalies
Global SST Anomalies - Short-Term
COMPARISON TO PAST LA NIÑA EVENTS
And for those wondering where the present NINO3.4 SST anomalies stack up against prior La Niña events, I’ve provided the following comparison.
Comparison Of La Niña Evolution – 2010 Versus 1988, 1998, and 2007
OI.v2 SST anomaly data is available through the NOAA NOMADS system:
Hi Bob -
What would keep the SSTs elevated? Isn't the normal response a drop that acommpanies the Nina as the cooler waters spread and impact the other oceans?
John: First, an answer to your question: I have no idea what's causing the delay in the response outside of the tropical Pacific.
Second, a clarification: Oceans remote to the tropical Pacific warm and cool during El Nino and La Nina events due primarily to changes in atmospheric circulation. Here's a comment I made at Lucia's yesterday that helps detail that.
Are SST anomalies in areas remote to the tropical Pacific, such as the tropical Atlantic, being warmed by the heat released into the atmosphere by the El Niño?
Wang provides a very detailed description in his “ENSO, ATLANTIC CLIMATE VARIABILITY, AND THE WALKER AND HADLEY CIRCULATIONS” (2005).
There’s a brief (and not too technical) summary of the causes for the rise in tropical Atlantic SST anomalies in response to an El Niño on page 24. He writes about the tropical North Atlantic [TNA], “The anomalous subtropical ascending motion corresponds to a late winter weakening of the North Atlantic anticyclone and the associated northeast (NE) trade winds over its southern limb in the TNA region. With the weaker NE trades come reduced evaporation and entrainment (from below the oceanic mixed layer) during late winter and early spring, leading to warmer SST anomalies over the TNA region by late spring and early summer (Enfield and Mayer 1997 and others)… …Thus, the Walker and Hadley circulations can serve as a ‘tropospheric bridge’ for transferring the Pacific El Niño SST anomalies to the Atlantic sector and inducing the TNA SST anomalies just at the time of year when the warm pool is developing.”
So SST anomalies can rise in response to an El Niño without the transfer of heat and without a change in forcings. When trade winds decrease in response to an El Niño, SST anomalies increase.
Eyeballing it, it seems 2010 seems a fairly good match to 1998.
YFNWG: Assuming you're talking about the weekly global SST anomalies, the 2010 peak ran 0.05 deg C short of 1998.
And here's a look at the monthly data:
2010 peaked 0.04 deg C less than 1998.
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