the Air Vent

Because the world needs another opinion

Instrument Bias

Posted by Jeff Id on April 8, 2010

Zeke and Lucia have an interesting post.

http://rankexploits.com/musings/2010/a-cooling-bias-due-to-mmts/

7 Responses to “Instrument Bias”

  1. Retired Engineer said

    Given the technology of the MMTS (a thermistor on a long wire) and the problems the surface stations project has uncovered, I have serious doubts about differences of a few tenths of a degree. Thermistors are OK for maintaining approximate temperatures in your fish tank, and almost totally worthless for absolute temperature measurements.

    I think they are lost in the noise.

  2. DeWitt Payne said

    Re: Retired Engineer (Apr 10 10:53),

    Once upon a a time I calibrated liquid-in-glass thermometers against an NIST calibrated standard platinum resistance thermometer with a water triple point cell as a calibration check. I also had a very precise and accurate thermistor based system that was more precise and much easier to use than the PRT with its Wheatstone bridge. Don’t tell me that thermistor systems can’t be both precise and accurate. Whether the MMTS systems actually perform up to spec is another question.

  3. John F. Pittman said

    No matter the technology, a good system is reproducible. It also requires testing and maintenance. Some are better than others, but if standards are established and met a consistant and useable database can be had. I think that the problem was, as has been expressed so often, that the system was meant for local use and the head office did not provide the necessities for maintaining the standards. Although I agree the data should not be thrown out, since it is what it is and what we have, I also think that the efforts of computer mainly (only?) bias removal are naive (not statistically powerful), unless shown to be correct and expansive in-situ. The large number’s argument does not necessarily address bias issues. However, it should make that bias small. “How small?” is the approximately trillion dollar question.

  4. curious said

    Does anybody have any info. on how SAT responds to sunshine? I’ve seen a report from 2000 which tried to quantify the difference between SAT an Skin surface temp for varying levels of radiation – ie cloud cover. Unfortunately it only gave the delta T between SAT and Skin temp rather than the tow series independently. I’m wondering how much SAT is a proxy for cloudiness and I’d guess this is not a new question.

  5. Jeff Id said

    #4, I don’t have much, just make sure that you don’t mix up the ground skin temp measurements with the tropospheric microwave measurements.

  6. curious said

    Ok Thanks – the paper I found showed strong and immediate response of skin temp to insolation. It also must have had the two source series as it quoted the delta T. I’ll google around more tomorrow and if I get nowhere I’ll maybe email the author. Before doing that I figured that tAV readers would be able to tell me if I’m just covering old ground. I can’t say I’ve seen it discussed but I doubt it is a new thought.

  7. Chuckles said

    Not that great a thread, much monologues, nitpicking and handwaving.

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