There’s been some discussion about specs on siting of weather stations and temperature measurement.
Coincidentally, I’ve been conversing with Jos de Laat of KNMI, the Dutch Meteorological Institute who offered some scans of weather station siting specifications from the World Meteorological Institute (WMO)
he writes:
OK then, you can find the first part of the report here (~ 1 Mb):
http://www.knmi.nl/~laatdej/TMP/WMO488.pdf
Especially the beginning of part 3 is relevant, I guess. Because of document size considerations for now I only scanned up to paragraph 3.1.2.1.7 (after paragraph 3.1.2.1.7 the description of requirements for measuring on other locations like sea and the free troposphere starts).
Descriptions of sensor and siting requirements are also available online (see below) …
… but they are more formal and largely based on WMO report 488, which contains some interesting quotes that are not present in later reports. The online reports also refer to the report below, which unfortunately I was not able to locate either online nor in our library.
World Meteorological Organization, 1993a: Siting and Exposure of Meteorological Instruments (J. Ehinger). Instruments and Observing Methods Report No. 55, WMO/TD-No. 589, Geneva.
These specs are worth a read, because they show that quite a lot of thought and analysis went info choosing the specs.
As for the 100 feet cited by the NWS on this page: http://www.nws.noaa.gov/om/coop/standard.htm
I suspect its a round off of 30.48 m where 30 meters is the minimum distance to an artificial heat source cited for a Class 2 climate site as defined by the specs used in the Climate Reference Network (CRN) which has a French lineage, and likely traces back to WMO.
Anthony:
I looked through the documents you provided, but still do NOT see a quantification of the effect of nearby pavement on as-measured temperature and thus a mathematical justification of the 100 foot off-set specification.
Well you are welcome to research that question yourself. You spend a lot of time criticizing basic assumptions, so here is your chance to contribute.
There may not be a “mathematical” justification, and I’d point out that one is not required. One derived experimentally would be just as valid.
For example, take a look at this website and note the before and after IR pictures related to asphalt. Clearly proximity to asphalt would have an effect on temperature readings.
http://www.pavements4life.com/QDs/Environment_1HeatIsland.asp
In any event, the fact that both NOAA and WMO have siting requirements and specifications for weather stations is reason enough to follow them. For example, I don’t have to prove that 1meter is defined by the International Bureau of Weights and Measures as the distance travelled by light in absolute vacuum in 1/299,792,458 of a second in order to be able to measure with it.
Until someone can prove that there is no reason to have such specifications I will consider them valid.
Anthony, that’s fine and understood. I just want to make a distinction.
Anthony,
Reading Leroy’s comments from the 2006 WMO meetings n instrumentation and siting guidelines it seems clear that some experimental work was done to establish the guidelines but he is french and I can’t locate him.
Nothing I have read on Extensive UHI studies indicates that the effect of asphalt falls off in short distances.
Since the US has 1221 stations and Brazil is sampled by six stations and samples only need be taken every 1000km, it would seem prudent to prune the polluted sites.
Or we can simply test the following.
a. Trend at asphalt infected
b. Trend at nicely watered
grassy site.
This is exactly similar to PARKERS UHI study.
Re: “Until someone can prove that there is no reason to have such specifications I will consider them valid.”
Now that is just plain silly. It should be fairly obvious to even the most casual observer that specifications for station siting have little or no validity since it appears that few folks follow them. Why be tied down to a specification? Reading the directions stifles creativity.
Specifications (like blog comment guidelines), are superfluous and mean next to nothing in the grand scheme of things.
;-]
Anthony,
http://www.cs.sunysb.edu/~vislab/papers/TVCGShimmering.pdf
These fellows have done something of note .in my old line of work I pushed for using GPU to calculate Lattice Boltzmann equations…
Essentially you want to see the thermal flow from the heat capacitor ( concrete, rock, asphalt)
to the surroundings
in 3Dspace and time..
Remember when we joked about doing a microClimate model for surface stations?
Where the ocean is a slab of asphalt?