Guest post by Lance Wallace
Last week (Aug 30), Anthony Watts posted my analysis of the errors in estimating true mean temperatures due to the use of the (Tmin+Tmax)/2 approach widely used in thousands of temperature measuring stations worldwide: http://wattsupwiththat.com/2012/08/30/errors-in-estimating-temperatures-using-the-average-of-tmax-and-tmin-analysis-of-the-uscrn-temperature-stations/ . The errors were determined using the 125 stations in NOAA’s recently-established US Climate Reference Network (USCRN) of very high-quality temperature measuring stations. Some highlights of the findings were:
A majority of the sites had biases that were consistent throughout the years and across all seasons of the year.
The 10-90% range was about -0.5 C to + 0.5 C. (Negative values indicate underestimates of the true temperature due to using the Tminmax approach.)
Two parameters—latitude and relative humidity–were fairly powerful influences on the direction and magnitude of the bias, explaining about 30% of the observed variance in the monthly averages. Geographic influences were also strong, with coastal sites typically…
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