2011-01-21 11:55:41Are UAH and RSS global? If not, what don't they cover?
John Cook

john@skepticalscience...
60.231.100.70
Robert mentions in Monckton Myth #2 that RSS and UAH are not global - does anyone know how much they don't cover? Why wouldn't they cover polar regions?
2011-01-21 12:36:17Sun-synchronous polar orbits
Daniel Bailey
Daniel Bailey
yooper49855@hotmail...
68.188.192.170

 The AMSU satellites are polar; RSS and UAH both analyze the same raw data, but do it differently:

 

Beginning with NOAA-15 (launched on May 18, 1998), the TIROS-N spacecraft were replaced by the
Advanced TIROS-N, or TIROS-ATN spacecraft and are the current platforms for the POES program. Like
their predecessors, they follow sun-synchronous polar orbits in a two-satellite profile with orbital plane
precession rates that guarantee a constant sun-earth illumination profile with respect to the spacecraft
throughout the year.

 

Source:

http://www.geo.utexas.edu/courses/387H/PAPERS/church1.pdf

 

From RSS Website:

Polar Orbits (SSM/I, AMSR-E, QuikScat, WindSat)

A polar-orbiting satellite is placed in a circular sun-synchronous orbit, typically at a low altitude of 700 to 800 km. It usually takes about 100 minutes to make one trip around the earth, allowing for just over 14 orbits daily. These satellites cross the equator at the same local solar time each day, once ascending (traveling from south to north) and once descending. A good description of this type of orbit is provided by the Naval Research Lab, Monterrey: Navy Forecaster's Guidance: General Description of Polar Orbiting Satellites

We provide data from the DMSP polar orbiters hosting the SSM/I instruments and the QuikScat platform hosting the SeaWinds scatterometer. Sun-synchronous orbits are often described by their equatorial crossing times. The equatorial crossing times remain nearly constant throughout the year. However, orbit degradation can cause a slow change in this value over time. Listed below are the ascending and descending equatorial crossing times for each currently functioning instrument on our web page. The plot shows the change over time of the ascending equatorial crossing times. Some satellite orbits are more stable than others and little change occurs over the years of operation.

Source:

http://www.remss.com/support/crossing_times.html#swath_time_labels

 

Daily data available here:

http://www.amsr-data.com/idx/ion-p.exe?page=amsre_daily.ion

 

2011-01-21 13:54:12
Daniel Bailey
Daniel Bailey
yooper49855@hotmail...
68.188.192.170

NOAA-18 Information page:

http://nssdc.gsfc.nasa.gov/nmc/masterCatalog.do?sc=2005-018A

 

 

NOAA-18 tracking page:

http://www.n2yo.com/?s=28654

2011-01-21 15:34:10
Glenn Tamblyn

glenn@thefoodgallery.com...
124.179.215.36

I believe that RSS cover from 82.5N to 70 S. UAH may go further south than this. I believe, although I'm not certain about this, that they don't use data from higher latitudes due to problems associated with measurement over ice.

2011-01-21 17:25:46TLT = 70S-82.5N; all other channels are 82.5S-82.5N (data issues poleward)
Daniel Bailey
Daniel Bailey
yooper49855@hotmail...
68.188.192.170

"Christy and Spencer also developed the first version of the TLT dataset. For a global average extending from 70S to 82.5N, we find a warming trend of 0.163 K/decade , while Christy and Spencer (version 5.2) find a warming trend of 0.147 K/decade ."

"Globally averaged trends computed over latitudes from 82.5S to 82.5N (70S to 82.5N for channel TLT) are shown in the table below, and include data through December, 2010:"

 

  Start Time  

  Stop Time  

  # Years  

Global Trend

Channel TLT  

1979

2010-12

30+

0.163 K/decade

Channel TMT  

1979

2010-12

30+

0.099 K/decade

Channel TTS  

1987

2010-12

22+

0.008 K/decade

Channel TLS  

1979

2010-12

30+

-0.306 K/decade

 

"We do not provide monthly means poleward of 82.5 degrees due to difficulties in merging measurements in these regions, and because these regions are not sampled by all central fields of view."

TLT


 

TMT


 

TTS


 

TLS


Source:

http://www.remss.com/msu/msu_data_description.html#version

2011-01-21 18:02:43
Glenn Tamblyn

glenn@thefoodgallery.com...
121.214.101.34

You also need to be careful which temp series you are looking at. The TLT series from RSS and T2LT from UAH are based on the T2 sensors and look at the lower to mid troposphere. All the MSU's suffer from issues with signals that originate partly in the lower stratosphere rather than just in the troposphere, introducing a cooling bias in the signal due to stratospheric cooling. TLT/T2LT were developed to try and filter this out. They are using more readings from each scan, from wider scan angles and then taking differences between the readings to try and filter out the stratospheric influence. However, this will increase the error margins due to sampling issues since you are using differences and these products have been cfriticised for this.

In contrast the TMT series from RSS and T2 from UAH are based on the T2 sensors but without the differencing algorithms. So their error margins are smaller but the stratospheric cooling hasn't been filtered out. The trends reported by these two series almost certainly underreport tropospheric warming.

I will be discussing this and other things in my advanced rebuttal to 'The Troposphere Isn't Warming', after I get my TFK 09 post up (and my wife's birthday party done)

2011-01-22 03:44:45Confusion
Albatross
Julian Brimelow
stomatalaperture@gmail...
199.126.232.206

Hi all,

I'm not sure who or what to believe.  According to Tisdale, the UAH MSU data go to 82.5 N and 70 S, and "UAH also fills in the polar data".

There definitely seems to be consensus that there are issues with the MSU data over the poles (i.e., ice).

John, perhaps it is best to email Christy or Spencer and ask them directly about their handling of UAH-MSU data over the polar regions.

2011-01-24 18:18:54
Ari Jokimäki

arijmaki@yahoo...
192.100.112.210
If Tisdale refers to Bob Tisdale, I'd suggest not to consider him as a reliable information source. Doubt his sayings as much as any other deniers.
2011-01-25 04:48:53Good Point
Albatross
Julian Brimelow
stomatalaperture@gmail...
199.126.232.206

Good point Ari-- my only thinking there was that he is probably close to Christy et al., so may have reliable information on that one point.

 

2011-01-25 14:45:12RSS TLT
Glenn Tamblyn

glenn@thefoodgallery.com...
124.181.128.239
Notice that in the RSS series suppled by Daniel are all 82.5 - 82.5 except for the TLT series which is 70 - 82.5. This uses a different processing algorithm. Maybe that is something to do with it.
2011-01-25 17:39:18
Daniel Bailey
Daniel Bailey
yooper49855@hotmail...
74.87.123.162

Been reading some more (IPCC and Tamino)

 

Per IPCC WG1 Ch 3.4.1.2, it would appear that TLT was the earliest using data from the earliest satellites.  My take is that in order to keep things backwards compatible with the oldest data, the TLT swath of 70S-82.5N was maintained.

There is also mention of comparisons with radiosonde data.  Radiosondes, especially the oldest datasets for sure, are/were land-based.  Spatial coverage in the SH was an issue as well.  This would also seem to come into play with the coverage swath for the TLT channel (since older radiosonde data was used to "ground truth" the TLT).  Data from an averaged zone that was higher than 1500 meters was excluded (thus no Antarctica or most of Greenland).  Data poleward of 60 degrees is suspect (Mears & Wentz 2008, which interestingly use global as being 75S-75N).

The newer stuff from RSS seems to have much less issues.  This post by Tamino delves into UAH vs RSS & recommends (wait for it)....RSS (OK, Tamino concludes there's something e**ed up with UAH TLT).  More from Tamino here.

Dunno why any of them use data poleward of 75 degrees.  Lotsa issues, no documentation I can find, yet.

2011-01-25 18:36:11
Rob Painting
Rob
paintingskeri@vodafone.co...
118.93.226.156

Dan, I've searched a few times before, but could never find anything. Maybe you'll have better luck:

http://www.climatescience.gov/Library/sap/sap1-1/finalreport/default.htm

 

2011-01-28 06:40:29
MarkR
Mark Richardson
m.t.richardson2@gmail...
134.225.187.80

The A-train are in Sun-synchronous orbits:

http://en.wikipedia.org/wiki/A-train_%28satellite_constellation%29

And in the A-train there is the AQUA satellite, which carries the AMSU-A instrument used for atmospheric temperature measurements.

 

 

A 'sun synchronous orbit' is where the satellite crosses over the same point on Earth at the same time each day, so 3pm in January and 3pm in July for example. If you do the maths for the orbit, you find that in the region where we can put satellites (between the top of the atmosphere and the van Allen belt which damages instruments), the closest you can get to the poles is about 82.5° latitude.

So instruments can have trouble measuring the poles (you can get closer with a big swath, like by swinging your instrument in that direction, but it can be difficult!)

 

2011-01-28 10:34:17
Rob Honeycutt

robhon@mac...
98.207.62.223
Albatross...  If John's going to contact Christy or Spencer maybe he should do it by way of a FOI request... or maybe 10 or 20 of them.  (joking)
2011-01-28 10:43:30
nealjking

nealjking@gmail...
84.151.54.151
We were talking somewhere about the paper Pielke and Watts were doing on weather site problems: If they don't publish plausible results, shouldn't we hit them up with FOIs?
2011-01-28 11:00:20
Rob Honeycutt

robhon@mac...
98.207.62.223
Neal...  Now there I think you're on to something!
2011-03-11 10:38:54More info from Carl Mears from RSS
John Cook

john@skepticalscience...
124.186.229.6

Saw this in an email from Mears:

The answer is different for RSS and UAH.  For RSS, we don't report TLT south of 70S.  This is for two reasons. 

1.  Much of the polar ice cap is at very high altitude, so the amount of surface emission in the TLT product starts to become large.

2.  The TLT near-nadir minus limb differencing procedure causes an unwanted spatial derivative to be included in the product.  This effect is especially troublesome when part of the swath is on the icecap, and part is off.  You can read about this in the TLT paper in JTECH.

Mears, CA, FJ Wentz, 2009, Construction of the RSS V3.2 lower tropospheric dataset from the MSU and AMSU microwave sounders, Journal of Atmospheric and Oceanic Technology, 26, 1493-1509.

UAH includes data down to 82.5 or 85.0 (the edge of the swath) , and then provides infill (extrapolated) data over the poles.  I'm not exactly sure what their procedure is.  This also means that I am not sure what their data means over the ice cap.  But I would guess that the surface contribution is at least 30%, if not 40%.

We exclude TLT data where the average height of the material surface is above 3000m, and south of 70S.

For TMT, our data goes all the way to 82.5, and is available at all locations.

Sorry, complicated answer to a simple question.

Interesting that UAH extrapolate into the Arctic - the same technique GISS use that have skeptics all in a tizzy. This mustn't be very public knowledge - I had no idea.

2011-03-11 11:11:06ironic
dana1981
Dana Nuccitelli
dana1981@yahoo...
38.223.231.252

Yes this is an interesting irony, considering how much heat the "skeptics" give GISS for their Arctic extrapolation.

2011-03-11 11:11:46
Albatross
Julian Brimelow
stomatalaperture@gmail...
199.126.232.206

"Interesting that UAH extrapolate into the Arctic - the same technique GISS use that have skeptics all in a tizzy. This mustn't be very public knowledge - I had no idea."

Quickly, tell Watts!

I'm still a little confused, it sounds then that the UAH TLT product may have a cool bias b/c of the way it deals with Antarctica--i.e., "contamination" for the high altitude ice sheet.  Does Mears have some insight on that?

 

2011-03-11 13:14:20UAH extrapolation
John Cook

john@skepticalscience...
124.186.229.6

It wouldn't hurt to get some refs on the extrapolation, then perhaps do a rebuttal to the "GISS extrapolate" argument which:

1. Defends how it gives good results and is superior to the HadCRUT assumption that Arctic temp is the same as the global average

2. Show how GISS is consistent with reanalysis products which are based on real measurements, not extrapolation

3. Little dig about how UAH extrapolate

So when skeptics slag off GISS, we have a page to redirect them to

2011-03-11 15:33:29comment
Robert Way

robert_way19@hotmail...
142.162.24.8

I wouldn't mind doing a rebuttal perhaps on this subject but if someone else wants it they can take it. The hadley warming should be put in there too. This should really be a post of the advantages and disadvantages of the different records perhaps?

2011-03-11 16:07:14Advantages/disadvantages
John Cook

john@skepticalscience...
124.186.229.6

I like that idea, written in an open, non-partisan tone that honestly confronts the weaknesses/strengths of all the various records. Would make a good reference that even both sides might appreciate (yes, I am still that naive after all we've been through). Robert, I'd say you da man on this topic. We all have our relative strengths - Rob is the word smith, Dana is the cyborg, I'm the delegator... you're the temp record whisperer :-)

2011-03-11 16:08:03good idea
dana1981
Dana Nuccitelli
dana1981@yahoo...
69.230.107.233

I like the idea of a 'GISS fudges Arctic temperatures' rebuttal.  It would be good to include the independent analysis of HadCRU data which found they were underestimating the warming trend due to omission of the Arctic.  Go for it, Robert!

Here's a potential "skeptic" quote for the rebuttal, from Goddard:

"[The GISS'] entire 21st century warming story is based on a defective interpretation of the Arctic...GISS graphs are broken, there is no significant 21st century warming trend."

2011-03-11 16:09:37Debunking Goddard
John Cook

john@skepticalscience...
124.186.229.6

There would be so many juicy quotes from Goddard if we wanted to include him in http://sks.to/skeptics but he just doesn't deserve the dignity of being in that list.

2011-03-11 17:48:12comment
Robert Way

robert_way19@hotmail...
142.162.24.8

The temp record whisperer? Clunkkkkyyyyy haha

Yeah i'll have a look at putting something together. Been meaning to for a long time on this subject. Its too bad cause hadley is not gonna come out looking good nowmatter what. I was looking at trying to put a paper together comparing the 3 methods plus taminos for an isolated region (I have all the data processing done) just haven't gotten around to writing it so this could be a good primer.

2011-03-11 19:58:24
perseus

owlsmoor@googlemail...
78.143.195.202

Has the near surface layer now failed on AMSU? (you need to move to channel 4).  Presumably this is the main channel of interest. 

Wouldn't we expect Satellite measurements to underestimate surface temperature changes due to measuring the average of a layer which is effectively an altitude based measurement and warming is less pronounced at altitude.  Is there an adjustment for this?

2011-03-12 06:52:50"The temp record whisperer? Clunkkkkyyyyy"
John Cook

john@skepticalscience...
124.187.101.78
Hey, Rob is the word smith. I'll have to delegate to him to come up with a snappier term for you:-)
2011-03-12 08:29:03
Glenn Tamblyn

glenn@thefoodgallery.com...
124.180.231.197

I have a post drafted on satellite temperature measurement - it is the advanced rebuttal to 'the troposphere isn't warming' but is also intended as a general tutorial on sat temp measurement. Hopefully I can pull it out of Word and into SkS tonight. Off to the salt mines now.

 

2011-03-12 09:01:45comment
Robert Way

robert_way19@hotmail...
142.162.8.171

Maybe I should postpone this post until the "BEST" results come in?

2011-03-12 09:41:14Forgive the pun
Daniel Bailey
Daniel Bailey
yooper49855@hotmail...
97.83.150.102

Would that be the BEST "Way" to go?