http://www.drroyspencer.com/2010/03/february-2010-uah-global-temperature-update-version-5-3-unveiled/

I trust that you received my “proposal” via e-mail. I see from your previous comments that you have done some calculations similar to those which I suggested. Great!

The Christy et al. algorithm for the AMSU was published in this report:

Christy, J.R., R.W. Spencer, W.B. Norris, W.D. Braswell and D.E. Parker, 2003: Error estimates of Version 5.0 of MSU/ MSU bulk atmospheric temperatures. Journal of Atmospheric and Oceanic Technology 20, 613-629.

There are 30 scan positions with the AMSU, reflecting the higher resolution of the newer instrument. Their algorithm uses channel 5, which has a slightly different theoretical emission curve than that of the MSU channel 2. Here are the weighting values used for each of the scan positions, as they gave them in Note 6:

“We attempted to create a multichannel AMSU retrieval to match MSU2 from various combinations of AMSU channels (specifically 5–8), but the noise characteristics were greater than those of AMSU5 alone. The AMSU5 linear coefficients for view angles 1 (limb) to 15 (symmetric with 16 to 30) are 21.74, 20.57, 0.00, 0.42, 0.40, 0.56, 0.54, 0.39, 0.44, 0.26, 0.00, 0.26, 0.00, 0.00, and 0.04.”
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First of all, I am intending to get in touch soon (and note that I always use my real name in private correspondence). But this is a sideline for me, and I’m not well placed to do a complete analysis from scratch (not to mention also not having the time).

This present post was more of a quick update and my previous post was more extensive. There, I examined the strong UAH seasonal divergence in the tropics, which certainly appears unrealistic. I also compared AQUA-based UAH to the previous data set based on NOAA-15. Also I found evidence of a less severe annual cycle in TMT/T2 in both UAH and RSS, which accords with your observation above.

Clearly the UAH LT annual cycle is highly problematic, but I’m not convinced that RSS is problem-free, and there may be inherent difficulties in inter-satellite calibration that will never be satisfactorially resolved.

I’ve not done much beyond producing the graphic of the TMT linked to above. I’m not a professional in the field, being from an engineering background. My knowledge of the math behind the MSU analysis does not include the theoretical foundation of the particular atmospheric emission/absorption physics, so there’s not much I can add.

I do think there remain serious problems with the UAH approach that should be investigated by someone. It looks like that someone isn’t going to be me. I wrote a proposal for a slightly different analysis of the MSU, but did so in an attempt to find someone else who might be interested in doing the work, which would require starting from scratch with the raw MSU scan data. That would be way over my head. If you want, I will send you a copy of that proposal, for whatever it might be worth, but you will need to identify yourself ..:-)

That said, I think you might try looking at the daily zonal averaged data, (which I used), and plot the trends for several zonal divisions. For example, you might divide the data into ranges of 82.5N-50N, 50N-20N, 20N-20S, 20S-50S, and lastly, 50S-82.5S. One might be able to visually detect any dependence on latitude in the annual cycle, which would certainly be interesting. I suppose I could do that too, but I’m trying to finish installing a wood stove and repair the engine on a 4×4 to get ready for Winter just now. If Winter is as nasty as some indications imply, I may have lots of time then…

Or, split the data into MSU and AMSU sections, to see whether the annual cycle appears different for those two instruments. Christy and Spencer use a different algorithm for each type of instrument in order to produce their TLT time series. It could be that the AMSU algorithm has a problem.

I was planning to highlight that accomplishment in my next post on this subject, but I’m happy to do so now.

I take it you’re also aware of John Christy’s comments, published in the UAH readme noted by MarkB above. I suppose this blog is not an apt venue for scientific exchange, but I must admit I’m curious as to your current thinking on these issues. Perhaps you are considering publishing on this in the near future; at least I, for one, hope so.

Swanson, R. E., Evidence of possible sea-ice influence on Microwave Sounding Unit tropospheric temperature trends in polar regions, Geophys. Res. Lett., 30(20), 2040, doi:10.1029/2003GL017938, 2003.

I looked at the UAH data over the Antarctic. Here’s a link to a graph of similar results for the TMT:

http://i454.photobucket.com/albums/qq268/Know_body/2mt7998a.jpg
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I have taken 5-year averages of redefined “seasons” in order to reduce the noise level while still leaving enough data points to discern the time evolution. I shifted the “seasons” by one month as Feb/Mar/Apr, May/Jun/Jul, Aug/Sep/Oct and Nov/Dec/Jan, because the impact of Christy’s adjustment is largest in MJJ. The 5-year periods are indicated in the plot. Conveniently 1998 (the year both of the transition between data sets and the big El Nino) lies at the border between two 5-year periods.

http://i26.tinypic.com/azfbte.png