I am still receiving questions about the method by which the satellite microwave measurements are calibrated to get atmospheric temperatures. The confusion seems to have arisen because Christopher Monckton has claimed that our satellite data must be tied to the surface thermometer data, and after Climategate (as well all know) those traditional measurements have become suspect. So, time for a little tutorial.
NASA’S AQUA SATELLITE
The UAH global temperatures currently being produced come from the Advanced Microwave Sounding Unit (AMSU) flying on NASA’s Aqua satellite. AMSU is located on the bottom of the spacecraft (seen below); the AMSR-E instrument that I serve as the U.S. Science Team Leader for is the one on top of the satellite with the big dish.
Aqua has been operational since mid-2002, and is in a sun-synchronous orbit that crosses the equator at about 1:30 am and pm local solar time. The following image illustrates how AMSU, a cross-track scanner, continuously paints out an image below the spacecraft (actually, this image comes from the MODIS visible and infrared imager on Aqua, but the scanning geometry is basically the same):
HOW MICROWAVE RADIOMETERS WORK
Microwave temperature sounders like AMSU measure the very low levels of thermal microwave radiation emitted by molecular oxygen in the 50 to 60 GHz oxygen absorption complex. This is somewhat analogous to infrared temperature sounders (for instance, the Atmospheric InfraRed Sounder, AIRS, also on Aqua) which measure thermal emission by carbon dioxide in the atmosphere.
As the instrument scans across the subtrack of the satellite, the radiometer’s antenna views thirty separate ‘footprints’, nominally 50 km in diameter, each over over a 50 millisecond ‘integration time’. At these microwave frequencies, the intensity of thermally-emitted radiation measured by the instrument is directly proportional to the temperature of the oxygen molecules. The instrument actually measures a voltage, which is digitized by the radiometer and recorded as a certain number of digital counts. It is those digital counts which are recorded on board the spacecraft and then downlinked to satellite tracking stations in the Arctic.
HOW THE DATA ARE CALIBRATED TO TEMPERATURES
Now for the important part: How are these instrument digitized voltages calibrated in terms of temperature?
Once every Earth scan, the radiometer antenna looks at a “warm calibration target” inside the instrument whose temperature is continuously monitored with several platinum resistance thermometers (PRTs). PRTs work somewhat like a thermistor, but are more accurate and more stable. Each PRT has its own calibration curve based upon laboratory tests.
The temperature of the warm calibration target is allowed to float with the rest of the instrument, and it typically changes by several degrees during a single orbit, as the satellite travels in and out of sunlight. While this warm calibration point provides a radiometer digitized voltage measurement and the temperature that goes along with it, how do we use that information to determine what temperatures corresponds to the radiometer measurements when looking at the Earth?
A second calibration point is needed, at the cold end of the temperature scale. For that, the radiometer antenna is pointed at the cosmic background, which is assumed to radiate at 2.7 Kelvin degrees. These two calibration points are then used to interpolate to the Earth-viewing measurements, which then provides the calibrated “brightness temperatures”. This is illustrated in the following graph:
The response of the AMSU is slightly non-linear, so the calibration curve in the above graph actually has slight curvature to it. Back when all we had were Microwave Sounding Units (MSU), we had to assume the instruments were linear due to a lack of sufficient pre-launch test data to determine their nonlinearity. Because of various radiometer-related and antenna-related factors, the absolute accuracy of the calibrated Earth-viewing temperatures are probably not much better than 1 deg. C. While this sounds like it would be unusable for climate monitoring, the important thing is that the instruments be very stable over time; an absolute accuracy error of this size is irrelevant for climate monitoring, as long as sufficient data are available from successive satellites so that the newer satellites can be calibrated to the older satellites’ measurements.
WHAT LAYERS OF THE ATMOSPHERE ARE MEASURED?
For AMSU channel 5 that we use for tropospheric temperature monitoring, that brightness temperature is very close to the vertically-averaged temperature through a fairly deep layer of the atmosphere. The vertical profiles of each channel’s relative sensitivity to temperature (’weighting functions’) are shown in the following plot:
These weighting functions are for the nadir (straight-down) views of the instrument, and all increase in altitude as the instrument scans farther away from nadir. AMSU channel 5 is used for our middle tropospheric temperature (MT) estimate; we use a weighted difference between the various view angles of channel 5 to probe lower in the atmosphere, which a fairly sharp weighting function which is for our lower-tropospheric (LT) temperature estimate. We use AMSU channel 9 for monitoring of lower stratospheric (LS) temperatures.
For those channels whose weighting functions intersect the surface, a portion of the total measured microwave thermal emission signal comes from the surface. AMSU channels 1, 2, and 15 are considered “window” channels because the atmosphere is essentially clear, so virtually all of the measured microwave radiation comes from the surface. While this sounds like a good way to measure surface temperature, it turns out that the microwave ‘emissivity’ of the surface (it’s ability to emit microwave energy) is so variable that it is difficult to accurately measure surface temperatures using such measurements. The variable emissivity problem is the smallest for well-vegetated surfaces, and largest for snow-covered surfaces. While the microwave emissivity of the ocean surfaces around 50 GHz is more stable, it just happens to have a temperature dependence which almost exactly cancels out any sensitivity to surface temperature.
POST-PROCESSING OF DATA AT UAH
The millions of calibrated brightness temperature measurements are averaged in space and time, for instance monthly averages in 2.5 degree latitude bands. I have FORTRAN programs I have written to do this. I then pass the averages to John Christy, who inter-calibrates the different satellites’ AMSUs during periods when two or more satellites are operating (which is always the case).
The biggest problems we have had creating a data record with long-term stability is orbit decay of the satellites carrying the MSU and AMSU instruments. Before the Aqua satellite was launched in 2002, all other satellites carrying MSUs or AMSUs had orbits which decayed over time. The decay results from the fact that there is a small amount of atmospheric drag on the satellites, so they very slowly fall in altitude over time. This leads to 3 problems for obtaining a stable long-term record of temperature.
(1) Orbit Altitude Effect on LT The first is a spurious cooling signal in our lower tropospheric (LT) temperature product, which depends upon differencing measurements at different view angles. As the satellite falls, the angle at which the instrument views the surface changes slightly. The correction for this is fairly straightforward, and is applied to both our dataset and to the similar datasets produced by Frank Wentz and Carl Mears at Remote Sensing Systems (RSS). This adjustment is not needed for the Aqua satellite since it carries extra fuel which is used to maintain the orbit.
(2) Diurnal Drift Effect The second problem caused by orbit decay is that the nominal local observation time begins to drift. As a result, the measurements can increasingly be from a warmer or cooler time of day after a few years on-orbit. Luckily, this almost always happened when another satellite operating at the same time had a relatively stable observation time, allowing us to quantify the effect. Nevertheless, the correction isn’t perfect, and so leads to some uncertainty. [Instead of this empirical correction we make to the UAH products, RSS uses the day-night cycle of temperatures created by a climate model to do the adjustment for time-of-day.] This adjustment is not necessary for the Aqua AMSU.
(3) Instrument Body Temperature Effect. As the satellite orbit decays, the solar illumination of the spacecraft changes, which then can alter the physical temperature of the instrument itself. For some unknown reason, it turns out that most of the microwave radiometers’ calibrated Earth-viewing temperatures are slightly influenced by the temperature of the instrument itself…which should not be the case. One possibility is that the exact microwave frequency band which the instrument observes at changes slightly as the instrument warms or cools, which then leads to weighting functions that move up and down in the atmosphere with instrument temperature. Since tropospheric temperature falls off by about 7 deg. C for every 1 km in altitude, it is important for the ‘local oscillators’ governing the frequency band sensed to be very stable, so that the altitude of the layer sensed does not change over time. This effect is, once again, empirically removed based upon comparisons to another satellite whose instrument shows little or no instrument temperature effect. The biggest concern is the long-term changes in instrument temperature, not the changes within an orbit. Since the Aqua satellite does not drift, the solar illumination does not change and and so there is no long-term change in the instrument’s temperature to correct for.
One can imagine all kinds of lesser issues that might affect the long-term stability of the satellite record. For instance, since there have been ten successive satellites, most of which had to be calibrated to the one before it with some non-zero error, there is the possibility of a small ‘random walk’ component to the 30+ year data record. Fortunately, John Christy has spent a lot of time comparing our datasets to radiosonde (weather balloon) datasets, and finds very good long-term agreement.
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Forgive me if this is slightly OT, and/or a stupid question (I am not a physicist) or if it has been asked before (I haven’t read all of the comments above) but to what extent could the increased DIRECT heating of the atmosphere over the 30+ year period of satellite measurements, due to the increasing human population, account for the slight increase in temperature of the troposphere measured by the satellite(s)? By ‘direct’ heating I mean the heat of (the increasing number of) buildings escaping into the atmosphere, plus all other human activities which generate heat (all of which eventually must leak out) – not to mention our increased biomass (we are warm-blooded after all). Thus, heating of the atmosphere directly, without the involvement of the greenhouse effect.
I wouldn’t have thought it would be too difficult for someone sufficiently knowledgeable (not me) to calculate the quantity of heat released by human activity in 1978 (using available figures for e.g. the amount of fossil fuel burnt + size of biomass i.e. population), do the same for 2010, then calculate the potential effect of the additional released heat on the amount of radiation which might be detected by the satellite?
I imagine this HAS probably already been done and the answer is that the theoretical effect is negligible, but I just thought I’d ask.
Moderator – if possible could you change the name for my previous comment to lower case ‘sjb’. I just realised I think there might already be an ‘SJB’ contributing to WUWT (not me, that was the first time I have commented).
[Reply: Only you can change your WordPress name. You can’t change your username, but you can add nicknames. The one you designate will appear as your screen name. ~dbs]
As a mathematician I appreciate the distinction you have made between a potential error in the absolute temperature derived from these measurements and the stability of that error. As we teach our first year calculus students, the first derivative of a constant is zero. If an instrument has an internal systematic (but constant error) it may read “wrong” but its first derivative — ie trend information — may remain completely accurate. The constant cancels out in any differencing operation.
This is an important point, and brings me to mind of a recent debate that demonstrated a standard alarmist tactic very well. When it is pointed out that surface temperatures have remained constant or fallen slightly over the last temperatures this is often met with the oblique “[That’s not true!] Several of the warmest years in recorded history have occurred during that same 10 years!”
In the debate I recently watched the exact phrase I used “That’s not true!” actually occurred, which brought me some amusement. For, the “rejoinder” does not contradiction the original assertion at all. It is quite possible for the temperature to be falling and at the same time at or around its highest overall value. Indeed, what else can it do after it attaining a local maximum? And this is precisely the case for the instrument-based temperature data these folks generally invoke as gospel. Whether or not one accepts the CRU-and-Mann-generated constructions, to present these two statements as somehow contradictory is simply ludicrous — it is the most common error made by students who flunk Calculus I by failing to understand the distinction between a function f and its derivative f’.
Insofar as this point touches on “debating points” it should be pointed out that the first derivative of temperature is far more important than that of the temperature itself when considering what climate trends are afoot. The second derivative is also very important. Where is the inflection point? Is the curvature up or down? Alarmists make some ludicrous temperature about the “increasing rate” of temperature change, CO2 increase, or polar ice disappearance. Even when these values themselves are seen to be increasing (f’>0) it is almost always the case, as I have observed, that they display a negative second derivative (f”<0), which merely underscores either the ignorance of the speaker or that they are willfully playing to the ignorance of their audience.
What is it temperature after all?…as faked as the word of a politician, no one believes in it, I would rather prefer amperage.☺
Well Dr Roy, you have added some more detail to the previous presentation you posted here. Too bad that some folks can’t tell the difference between accuracy, and repeatability.
I’m pretty dumb when it comes to molecular spectroscopy in the microwave region (50-60 GHz). Does your sensor simply grab that whole frequency range in something like a thermopile; or can you actually frequency select some much narrower specific O2 frequencies. That would have a bearing on the sensitivity to RFI noise that some have raised as an issue. The two point calibration doesn’t raise any hackles with me; though it seems to have bothered some.
I find my self chuckling at the comments vis-a-vis the 1deg C accuracy. I assume that these people must have absolute faith in the absolute accuracy of the thermistors or thermocouples that are in these Stephenson Screen “Owl boxes”. And fancy that every single one of those thermometers has exactly the same accurate calibration down to millidegrees I am sure. You must be cheating too only need one thermometer to look at the whole globe.
Personally, I have close to zero confidence in any thermistor or thermocouple thermometer. The thought of connecting a temperature sensor to external circuitry through heat conducting wires does not excite me.
One thing I didn’t quite get was whether ALL of your measurments are made looking straight down; or whether you do do oblique readings. You mentioneed the shift due to atmospheric path in oblique readings, but I didn’t get whether you do it anyway, and correct for path obliquity.
I’m somewhat curious as to why your 2.7 K big bang echo measurements are not offset by actual starlight. Do you spectrum filter to get rid of the energy spectra of real stars ?
Butch (05:19:47) :
What you’re reading is not the original version of Monckton’s piece. It did indeed originally say that the satellites were calibrated from the earth measurements, but he promptly revised it to what you’re reading after he was alerted to the error, so the incorrect version was on his site for only a very short time.
Dr. Spencer thank you for the explanation.
I just thought of one question. Radiant energy leaving the earth consists of reflected sunlight and emitted infra-red. But from Dr. Spencer’s explanation it now seems like some energy also leaves through emitted microwaves. Is that amount significant enough to affect the energy balance?
I assume the integration avoids “double/multiple counting” over the poles ?
Are polar measurements used to check repeatability ?
I’ve dealt with this issue of false precision here as has Lucia. It doesn’t make much of a difference.
@R Craigen
You are absolutely right, but the problem lies with differentiating a noisy signal. In the frequency domain, differentiation is a filter with an amplitide prortional to -j.omega so that noise becomes problematic. The second derivative is even worse.
John Simons (03:39:29) :
“Speaking of satellite data
Wow! check out the present anomalies
http://discover.itsc.uah.edu/amsutemps/amsutemps.html”
It would be a remarkable discovery indeed to find that during an ice age, global temperatures actually increase! However we would have no reason to doubt it, especially if published in the leading climate journals. Climate science by climate scientists!
“SJB (09:59:35) :
Forgive me if this is slightly OT, and/or a stupid question (I am not a physicist) or if it has been asked before (I haven’t read all of the comments above) but to what extent could the increased DIRECT heating of the atmosphere over the 30+ year period of satellite measurements, due to the increasing human population, account for the slight increase in temperature of the troposphere measured by the satellite(s)? …..
I wouldn’t have thought it would be too difficult for someone sufficiently knowledgeable (not me) to calculate the quantity of heat released by human activity in 1978 (using available figures for e.g. the amount of fossil fuel burnt + size of biomass i.e. population), do the same for 2010, then calculate the potential effect of the additional released heat on the amount of radiation which might be detected by the satellite?”
Hoyt (2006) indicated the US generated heat at about 0.34 W/M2, about 1 W/M2 in urban areas and much higher in cities. For this reason you would believe satellites are much better than surface temperature stations, at least 1/2 or more are in urban areas. Of course, land accounts for only 29% of the globes surface area.
He estimated that since 1900 a population increase of 1 billion to 6 billion could account for 0.5 deg C, which is close to the observed warming. Of course, it’s complicated by land useage changes, aerosols, more active sun, and of course more CO2, etc.
Thats from David Rapps book on Assessing Climate Change
Ignots (05:00:41) :
“- Did we know how PRT is influenced by prolonged cosmic radiation?”
http://www.onlineconversion.com/forum/forum_1059218210.htm
100 rem = 1 Gray
http://www.fas.org/spp/military/docops/usaf/2020/app-f.htm (on satellite radiation exposure)
“using 5.0 gm/cm2 of aluminum shielding, the REM for one year continuous exposure would be reduced to about 550.”
So. 5.5gy per year in a Bud box; less exposure with more shielding.
According to http://www.lakeshore.com/pdf_files/Appendices/LSTC_appendixB_l.pdf their PtRDs typically shift about -20 milliKelvin with a Gamma dose of 29 Grays plus 2.5e12 neutrons/cm2, so the drift probably would be less than 5 millikelvin per year. There’s a NASA engineer sitting in a cubicle somewhere who knows what the shielding actually is (prolly not a Bud Box).
R. Craigen (10:47:57) :
“When it is pointed out that surface temperatures have remained constant or fallen slightly over the last temperatures this is often met with the oblique “[That’s not true!]”
But the claim isn’t that” the surface temperature record [from HadCRUT/GISS or even RSS or UAH] have remained constant or fallen slightly”, nor do the people making the claims address whether they are statistically significant. What is claimed is that we see “global cooling” since 1998 or 2002, usually ending at the 2007 minimum – google shows “Results 1 – 10 of about 1,610 from wattsupwiththat.com for “global cooling” – ignoring Arctic sea ice, glacier, and Greenland ice loss, which indeed ” … underscores either the ignorance of the speaker or that they are willfully playing to the ignorance of their audience.” Speaking of which, do you not realize that SNR of the derivative of a noisy signal will be worse, or were you hoping that people like Richard Saumarez (14:37:58) : aren’t paying attention?
KeithGuy (01:19:16) : Now would someone please explain in simple terms how GISS global temperature data is contrived (Whoops! I mean calculated)?
Try this:
http://chiefio.wordpress.com/2009/11/09/gistemp-a-human-view/
It has clickable links to greater detail if you want to get more deeply into any one part, but has a “normal folks” feel to the text.
From here:
http://www.wsdmag.com/Articles/ArticleID/18449/18449.html
we have
One final note about the propagation. As it turns out, 60 GHz is at that part of the spectrum where the absorption of the signal by water molecules is at a peak. That’s probably why they made 60 GHz the unlicensed band. The frequencies directly above and below are more useful. What that means is that when it rains or snows signal amplitude will be severely decreased even blocked. That attenuation is in the 10 dB/km to 15 dB/km or about 1.5 dB/100 meters. Luckily, most applications will probably be of the indoor variety, so we won’t have to worry about that.
Two really good arguments for high water-vapor attenuation are interference mitigation and security. Signals won’t travel far beyond their intended targets with this technology so interference to others will be minimal and the chance for illegal reception significantly less.
OK, it’s a bit vague on how far below 60 gHz is less attenuated… but I still come away with an uneasy feeling about this.
We have folks building gear using these frequencies for radars and “stuff” and we have water absorption of at least some of it.
Sure seems to me like we could easily have a mistaken “warming” signal via some combination of “more radars on more things” and / or “more gHz leakage from computers everywhere”. It also looks like reduced water in the air (say from, oh, I don’t know, Frozen Air in a cooling trend…) could end up letting more signal reach a satellite.
I’m as willing as the next guy to accept some “magic sauce” is applied that prevents this (say o2 is in 55 gHz and water absorbs from 58 to 60, so you put a notch filter in and look at 55 gHz); but I’d be more comfortable with a word from the folks who make this bird work saying “Yeah, we handled that”… “ground source and water absorption are covered”.
from the same source, it looks like it is going to get worse:
Each week I hear more about products and plans for the unlicensed 60 GHz spectrum. Yes, that is 60 gigahertz, or 60 billion cycles per second. Very high frequency indeed. What can you do with frequencies that high? Well, with all the progress in 60 GHz semiconductors, we are about to find out. A 60 GHz wireless product is probably in the near future.
… This was from March, 2008 …
As for data rate you need to look at available bandwidth. With 7-GHz bandwidth available at 60 Hz (57 to 64 GHz in the U.S.), you can really get some great data rates (4 to 5 Gb/s to be conservative), and that is using the simpler BPSK and QPSK modulation methods.
And some of it is in the top end of 50 gHz…
Panasonic has an HDTV gizmo at 60 gHz:
http://www.wirelesshd.org/ as have others
http://ieeexplore.ieee.org/Xplore/login.jsp?url=http%3A%2F%2Fieeexplore.ieee.org%2Fiel3%2F4660%2F13055%2F00596529.pdf%3Farnumber%3D596529&authDecision=-203
I also found a bunch of paywalled references to a 50 gHz rain guage and similar 50 gHz radar type gear.
So, OK, which is it: Water is “an issue” and attenuates. Or Water is not an issue, but ground source is going to propagate and be an issue…
Don’t know what it is, but something here has my “What?” sensor tingling..
”
Kendra (04:58:06) :
Off-Topic but Please Help:
I know someone who is in a position of influence – ie will be teaching a new class on the politicization of climate science.
Unfortunately, this person buys the schtick (climategate overblown, evidence stands, etc.)
The person recommended (others as well, but this was specifically mentioned) that I read The Long Thaw by David Archer. Not only is it difficult for me to spend money on what I’m “biased” to see as propaganda, but I need information as soon as possible. The reviews at Amazon were not informative altho there was a negative one, nothing substantive.
If I can do one thing about this, it’s to at least try to affect someone with influence who then keeps the “machine” haha (re MIT debates, etc.) rolling. So this is an important challenge for me, altho the person is brushing me off with the “agree to disagree” meme.
I never even heard of David Archer since I started researching over a year ago.
I probably seem a bit histrionic but the sooner I can stop this, the better – I mean, try to stop this.
This is not the kind of thing for Climate Audit so won’t ask there, and am assuming that Jeff Id’s readers also read here.
So, 1. Does anyone have anything to say about this book and/or David Archer’s arguments. 2. Where else could I ask this?
”
Kendra,
I’m not familiar with Archer’s book. He has put a MODTRAN Calculator on his website that allows one to calculate the radiative power transfer into and out of the atmosphere and offers a few parameters to manipulate. As far as I know, it’s an honest one to the limitations that exist. In and of itself, it doesn’t prove anything one way or the other.
One book that might be of interest is Svensmark’s and Calder’s The Chilling Stars.
You need to understand that there is GW, global warming, AGW, anthropogenic global warming (man-made), and CAGW, catastrophic antrhopogenic global warming. You also need to understand that it is a cult style religion being exploited for political reasons in order to impose tyranical rule that would never be accepted otherwise. As such, there will be difficulty using logic to combat emotion. Somewhere deep in the mix, there is the science or some cartoon rendition of science.
GW is not an issue. Climate does change and if we didn’t cause it, there’s probably no prospect we could actually manipulate it. AGW has the appearance that we caused it so we must fix it. What the hype is about is the CAGW or catastrophic change we supposedly caused. It has to be catastrophic to justify the expense and suffering. Let’s face it, if we actually are responsible for the increase in co2 in the air and it does lead to less colder weather and more plant growth with no down side, we might be responsible for saving life on planet Earth by this additional injection of co2. To reduce this co2 could actually be a very bad idea. This is the antithesis of the mentality found in the cult which begins with the notion that man is evil and is destroying the planet, including those cute cuddly polar bears and baby seals.
What it means for the argument is that there are many pieces that must be addressed. One that this web site has concentrated in is determining the validity of the instrument record being used. This particular thread is concerned with a particular satellite record and how it is done. Another is Climate Audit tthat concerns itself with the validity of the statistical analysis being used, quite often with proxies like tree rings. There are others that are more general or without specialties and there are others that concentrate on only certain aspects.
One key thing to know is that while there may be thousands of scientists involved in global warming research, practically none of them are knowledgeable in the fundamentals of the physics associated with the warming. A biologist or economist dealing with the ramifications of 5 degree C warming is likely to be clueless as to whether or not 5 degrees C increase is even possible under any circumstances. Another is that statements like “10 years or it’s too late” or consensus science, and the like are unscientific.
In reality, this huge case for CAGW is far from proven. There are severe flaws on every front.
Anyone interested in more detail about remote sensing of atmospheric temperature as well as the physics of radiative energy transfer would not go wrong by obtaining a copy of A First Course in Atmospheric Radiation by Grant W. Petty.
Dr. Spencer’s post is informative about some of the details of calculating temperature from microwave emission, but there’s a lot more he left out. But then he’s not writing a chapter in a textbook here.
@pft (17:05:03)
Thanks, very interesting. I would add that Rapps book to my birthday list, but I’ve just looked it up and seen how much it costs!
So let me understand some of the basics regarding the Advanced Microwave Sounding Unit (AMSU) flying on NASA’s Aqua satellite:
1) The Aqua satellite takes 99 mins to orbits the earth.
See: http://aqua.nasa.gov/about/instruments.php
Therefore it makes 14.55 orbits in 24 hours
24 hrs x 60 mins = 1,440 minutes
1,440 / 99 = 14.545454
i.e. Aqua flies over the equator in daylight 14 times in 24 hours.
2) The earth circumference at the equator is 40,075 km
See: http://en.wikipedia.org/wiki/Earth
Therefore, the AMSU should scan 2,862.5 km of the equator on each orbit.
40,075 km / 14 = 2,862.5 km
3) This WUWT article says the instrument scans across the subtrack of the satellite,
the radiometer’s antenna views thirty separate ‘footprints’, nominally 50 km in diameter
Therefore, the AMSU only scans 1,500 km of the equator on each orbit.
Using simple maths this means the AMSU only scans 52.4% of the equator.
1,500 / 2,862.5 = 0.524
Note:
The AMSU has a Swath of 1650 km according to http://aqua.nasa.gov/about/instrument_amsu.php
This might increase the coverage to 57.64%
Therefore, I would like to know how we get UAH global temperatures by sampling only 52.4% or 57.64% of the globe….
Joe Born (12:58:22) :
Thank you for the response. It was my recollection that I had in fact seen the statement both ways. I believe now that the linkage to earth temperature reference was part of a video production I watched, probably produced prior to the correction.
It didn’t sync with my understanding of UAH’s methods, which prompted the search that yielded the paper, which was obviously corrected by that time. Time lines can be so tricky. Thanks again!
Malaga View (11:32:16) :
“i.e. Aqua flies over the equator in daylight 14 times in 24 hours.”
http://aqua.nasa.gov/news/nasa_release.php?id=1
“Aqua crosses the equator 28-30 times a day, doing so at 1:30 p.m. as it heads north and at 1:30 a.m. as it heads south. ”
And the atmospheric microwave emissions don’t turn off at night.
Brian Dodge (18:44:37) :
Aqua crosses the equator 28-30 times a day, doing so at 1:30 p.m. as it heads north and at 1:30 a.m. as it heads south.
This means 14-15 crosses in daylight and 14-15 crosses on the dark side….
And the atmospheric microwave emissions don’t turn off at night.
So the AMSU could take 14-15 day time scans and 14-15 night time scans…
But generating UAH global temperatures from these 28-30 scans would really mixing sunlight apples with moonlight pears…
cba,
Thanks so much for your kind answer – and a very informative overview as well. I just received Svensmark’s book and am very much looking forward to it – my husband has it right now.
Someone I know, to whom I’ve sent links including Climate Audit, WUWT and others, is about to teach a class on (ironically) the politicization of science, where one of the required books is Archer’s. We’d had discussions during a visit last summer and, actually, the follow-up e-mail debate was supposed to be about whether or not there was a consensus (I know, bogus argument). Rather than compiling lists (I see a new one’s out, comparing warmists and skeptics in terms of numbers but also in which fields), I thought those I knew of showing skeptical points of substance was the right way to go. No response was ever given to these over more than 6 months, although she had said she would send links representing her side of the argument.
In return, I finally got a dismissal “we’ll have to agree to disagree” with a recommendation that I read The Long Thaw (rather elitist, I have to buy a book and she got from me links for free). I also have a list of the other few required readings and recommended readings to be used in the seminar – just what you’d expect. I had mentioned following Climategate, too, and the comment included the usual “overblown” and “science not affected.”
This is someone I’ve known for over 30 years but rarely see. A political scientist with leftist persuasion I had always been aware of but we rarely discussed politics, until last time. I was hoping to open her mind just ever so slightly but I doubt that she gave the links even a cursory glance.
Not only did I feel anger on a personal level (uppity Kendra oversteps bounds) but the reality of what was going to occur – a number of minds subjected to the same old propaganda – and I felt this impulse to try to stop it and to be able to make a couple of arguments in terms of this Archer guy seemed to be the first step.
I did keep on searching and found an introductory piece on pbs.org (also showing funding by ExxonMobil, go figure) where I identified 2 statements that I know are at minimum controversial – how long CO2 remains in atmosphere and amount of CO2 in volcanoes, so that’s a start.
Naturally, I would make the point that I do not wish to buy an expensive book that already presumes as proven what is not – moreover, even without those 2 points, the book was published in 2008 and cannot possibly deal with the latest information (CO2’s lumpiness, haha, for example).
I’ve come to the realization that the whole endeavor will be tilting at windmills and this group of kids will be 15 or 20 more brainwashed ones set loose in the world and feel quite demoralized. However, I still will slowly work on a reply so am grateful for any assistance in dealing with this +”*ç% Archer. I also discovered he’s associated with our old friend realclimate!!!
I only wanted to post this plea in the latest WUWT so more people would see it, knowing it would be OT in any case. Haste makes waste, so I accidentally clicked on this thread instead of the newest!!!!
Thank you very much again!