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Tuesday, January 13, 2015

More Tropical Ocean Stuff

In keeping with my recent series of thoughts I guess some satellite data might be useful.  This uses the Reynolds Oiv2 SST data masked to 20S-20N using Climate Explorer with the UAH MSU data for the lower and middle troposphere plus inverted lower stratosphere.  I used UAH because it is already masked for the tropics for all three products.  RSS mid-tropo and lower strat are a bit of a pain for me to work with.  Their lower troposphere product in absolute temperature is on Climate Explorer, but for now I will stick to this.

As you can hopefully see, there is very little difference between the UAH lt and mt, in other words, not obvious indication of mid-tropospheric warming.  Since I used a 1981 to 2014 baseline because of the Reynolds data, this comparison might look a little different that some others.  As would be expected, the inverted stratosphere data tracks well but has a lot of excursions or noise if you like, related to volcanic aerosols and solar forcing variations.  Since the lower stratosphere densitity is much lower than the lower troposphere, that would be expected.  Note the right hand scale is in Wm-2.

Since Reynolds data is in absolute temperature, I converted the data to approximate energy anomaly.  That is a useful reference.  Since the lower troposphere density is greater than the mid-troposphere density, There should be more fluctuation in the mid-troposphere data, if you have a nice tidy isolated system that is.

This plot of the RSS tropical lower troposphere in absolute temperature should be a hint as to why things aren't so tidy.  279K is about 6 C degrees and the actual "surface" temperature would be closer to 30 C degrees.  RSS is measuring something close to the tropical cloud base.  Since UAH and RSS don't use the same weighting, they are not measuring exactly the same thing, so you really should not expect them to be the same.

By converting both Reynolds SST and the RSS lt to approximate energy anomaly, thanks to the available absolute temperatures, I can get a difference between the two.  That difference would be roughly the latent heat loss of the surface.  If there is less latent heat loss, you should not expect there to be a tropical tropospheric hot spot related to increased heat in the lt due to pushing the saturated lapse rate.  There is no tropical tropospheric hot spot because there is no reason for there to be one.  The latent heat loss is being regulated by some combination of factors.  Clouds would be part of the regulating function but since surface and upper atmosphere wind impact the simple up/down heat transfer there isn't any easy way to assign attribution to what is causing what.  So let's just say the models are missing some part(s) of the dynamics and leave it there for the moment.

Unfortunately, we only have satellite data for a very short period of time.  My "guess" would be that the tropics are currently near a happy place.  You could call it a control point or a strange attractor, but it is a somewhat stable operating point.  This point happens to coincide with the "pause" and based on the Oppo et al. 2009 plus a few other tropical temperature reconstructions, what was "normal" prior to the period known as the Little Ice Age.  Calibrating climate models to a recovery from the LIA period would cause considerable over estimation of impact similar to what is happening now.

From a modelers perspective, Issac Held has a recent post on the TTHP.  I prefer not to get caught up in climate model issues when simply noting where they miss should be all that is required.  The why's of the misses are up to the modelers themselves.

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