Wednesday, 17 January 2007: 8:45 AM
Sources of unexpected inaccuracies in temperature measurements
207A (Henry B. Gonzalez Convention Center)
It is well known that inhomogeneous numbers enter into the climate record due to changes in observers, instrumentation, radiation shields, aspirated vs. unaspirated instrumentation, location of site, changes in time of observation, and urbanization or changing land uses near an observation site. It is also well known that the requirements of meteorological instrumentation can differ from those intended for climatological purposes. With the coming of high resolution forecast models, the requirements for meteorological siting may have to change. With urban areas dominating the scene in some of the grids of a high resolution model, the old standard of instrumentation over a grass field may have to give way to a site reflective of landuse in an urban setting. Surprisingly,in addition to all of these considerations, unintended bias, error or noise appears to enter into the record from causes such as the protocol of how a measurement is translated into a number appearing on an instrument display. There are clear examples of a lack of standardization or meteorological thought given to the sampling frequency from one platform to another. The instrumental response times differ between various platforms and from prior instruments at a given site. Finally, variables such as the maximum temperature of the day are calculated as the highest instantaneous value observed on some platforms to the highest of a 5 minute average of instantaneous values on other platforms!