Effects of Recent Thermometer Changes in the Cooperative Station Network

Abstract

During the past five years, the National Weather Service (NWS) has replaced over half of its liquid-in-glass maximum and minimum thermometers in wooden Cotton Region Shelters (CRSs) with thermistor-based Maximum-Minimum Temperature Systems (MMTSs) housed in smaller plastic shelters. Analyses of data from 424 (of the 3300) MMTS stations and 675 CRS stations show that a mean daily minimum temperature change of roughly +0.3°C, a mean daily maximum temperature change of-0.4°C, and a change in average temperature of-0.1 °C were introduced as a result of the new instrumentation. The change of-0.7°C in daily temperature range is particularly significant for climate change studies that use this element as an independent variable. Although troublesome for climatologists, there is reason to believe that this change (relative to older records) represents an improvement in absolute accuracy. The bias appears to be rather sharp and well defined. Since the National Climatic Data Center (NCDC) station history database contains records of instrumentation, adjustments for this bias can be readily applied, and we are reasonably confident that the corrections we have developed can be used to produce homogeneous time series of area-average temperature.

Historical changes in lake ice‐out dates as indicators of climate change in New England, 1850–2000

“…The data have been subjected to quality control and homogeneity testing, and adjustment procedures for bias originating from changes in observation time (Karl et al, 1986), instrumentation (Karl and Williams, 1987;Quayle et al, 1991), station location (Karl and Williams, 1987), and urban heat-island effects (Karl et al, 1988).…”

The reliability of global and hemispheric surface temperature records

“…A more recent example of changes in instrumentation is the automation of measurements across whole countries and regions that has taken place during the last 25 years [e.g., for the U.S., in Quayle et al (1991)]. It is, however, possible to identify such changes and correct for them, provided dates of the changes are known.…”

Precipitation trends over the Russian permafrost‐free zone: removing the artifacts of pre‐processing

“…Nevertheless, the estimates presented in this paper, while being the most probable, and based on all the data available to the authors in digital form, can be significantly improved, if most of the entire former Soviet Union precipitation network (up to 11 thousand stations in the early 1970s), and/or the supplementary information about wind speed, precipitation type, and the history of the station exposures (to account for the wind undercatch) become available for the analyses. Figure 1, but after re-adjustment for wetting correction using Table AI and Table AII This study illustrates the challenges that proper data preprocessing represents for climate change studies and is part of a long list of similar difficulties, such as: the uncertainty with the bucket correction of sea surface temperature (Folland and Parker, 1995); troubles with implementation of the WMO recommendation in 1949 to switch the total cloud cover measurements from tenths to octas (some large countries, including Russia, Canada, China and the United States neglected this recommendation); introduction of new temperature sensors in the United States network (Quayle et al, 1991); and numerous changes in remote sensing instrumentation.…”