There are many oscillations in the global sea surface temperature field, e.g. Pacific Decadal Oscillation (PDO), El Nino and South Oscillation (ENSO), North Atlantic Tripple (NAT). I wondering how long does it take for the atmosphere to fully feel these signals. And how long does it take for the atmosphere to forget them.
I am not an expert in this field, but I am afraid that there is no simple direct answer to your question, as the research in this area is still very lively and the response to each of them will differ. I suggest you to start reading some older papers to get the idea how the coupling works, like:
Lau and Nath(1989) http://journals.ametsoc.org/doi/pdf/10.1175/1520-0442%281990%29003%3C0965%3AAGCMSO%3E2.0.CO%3B2
Kushnir and Held (1995) http://journals.ametsoc.org/doi/pdf/10.1175/1520-0442%281996%29009%3C1208%3AEARTNA%3E2.0.CO%3B2
Liu and Wu (2004):
http://journals.ametsoc.org/doi/abs/10.1175/1520-0442(2004)017%3C1859:ARTNPS%3E2.0.CO;2
The responses are different in each case. El NIno & La NIna has zero effect, when integrated over the total length of the disturbance, which is about 4...5 years. The atmosphere responses for the irradiation change in about one year:. The residence times are 2,74 months for the sea and 1.04 months for the land. That is why La Nina increases the temperature and La Nana decreases and the normally the totola effect is about zero.
Here is a link into my web site, where are publications and slideshows on this matter
www.climatexam.com
In general the atmosphere is very fast, especially in the tropics where the dynamics - in the absence of rotation - is dominated by fast waves; slower as you get to higher latitudes. But in general the atmosphere has crappy memory; whatever the SST was a week or two ago, doesn't matter much for the atmosphere today.
However, in many cases the SST signals arise from a coupled atmosphere/ocean process; not from some magic change in SST that just "happens" and then the atmosphere responds to it. In ENSO for example, the predictability, which is basically the same thing but the inverse, is decent for up to 6-12 months but that is not because it takes so long for the atmosphere to respond but because that is the inherent times-scale for the coupled system. And that time scale in turn is also different for the different teleconections involving SST that you mention, depending on where and by what dynamics they work.
The answer hence is that the question is wrong...:-). First, oscillations in SST are forced by the atmosphere and not the other way around, and second, for a typical time scale you can't look at one forcing the other; they are both forcing each other.
Thank you, everyone, especially Prof. Tjernstrom. Your answers make me to rethink this question in a new perspective.
Hi Shuyun,
The earlier answers are right to say that ENSO is due to a coupling between the atmosphere and ocean and that many ocean surface temperature variations are due to the atmospheric effects on the ocean rather than the other way around but nevertheless there is also a simple partial answer to the response time of the atmosphere to ocean changes.
It turns out that the atmospheric temperature response to ENSO events is significantly lagged and this can be easily seen in global average temperature. ENSO events, either La Nina or El Nino peak in winter but then lead to maximum changes in global average temperature a few months later, in the first half of the following year. This is the reason that 1998 was so much warmer than 1997 globally for example.
The response time of a few months is due largely to the time taken for warming to spread to other ocean basins. The size of the effect for ENSO is about 0.1 degree of global warming or cooling for each degree of El Nino or La Nina.
Given the big El Nino now at its peak, this means 2016 will also be very warm globally compared to other years.
Hope this is useful
Adam
Thank you Adam. Thank you Farah, I am sure your articles will be helpful.
Hi Shuyun,
I would like to add a little correction in the above discussion. Actually, the appropriate representation of "El Nino" is ENSO (El Nino Southern Oscillation). The "El Nino" only represents the Oceanic component and the Southern Oscillation indicates the Atmospheric component. Hence the name ENSO. The ENSO has a recurrence interval of 2 to 7 years. On the contrary, thePacific Decadal Oscillation (PDO) is a long-term ocean fluctuation of the Pacific Ocean. The PDO is more like an Oceanic phenomena with very long residence time (20 ~ 30 years) that perturb the the Jet Stream truck over North America. Like PDO, the Atlantic Meridional Overturning Circulation (AMOC) is completely a Oceanic oscillation pattern with residence time of 60~70 years.
In addition, the response of these oscillation patterns depends on which place of the Earth it happens. The ENSO takes place in the tropics but PDO in the high latitude.
Furthermore, If the oscillation pattern is belongs to Oceanic origin then it would take very longer time to mature and decay due to higher heat capacity and inertia of the global Ocean. In contrast, a coupled oscillation pattern like ENSO takes shorter response time as it is controlled by the Hadley and Walker circulation.
In summary, all meteorological oscillation patterns are characteristically different both in origin and response time.
Thank you for your question. I hope this explanation will help you to understand the above discussion more easily.
Thank you, Mostofa, for letting me know the AMOC and that the response time of atmosphere depends on the origins and places of the Oscillation.
Thank you, Guillermo. Your answer do inspire me to think about the difference between PDO and ENSO. Thank you again.
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