If only BHTs are available with no time-since-circulation information, simply adding 33 °F (18 °C) is actually one of the best correction methods. The expected Teq uncertainty is ±17 °F (±9 °C) . Averaging multiple corrected BHT data from a single depth using either of the latter two methods improves the predicted equilibrium temperature estimate.
The histogram above shows the difference between observed and predicted equilibrium temperature where the correction is obtained by simply adding a constant to the observed BHT (Teq = BHT + 33 °F ) for all data used in this analyses (N = 983 DST-BHT pairs). The constant is the median of the difference between equilibrium temperature and adjacent (±500 ft) measured BHTs. Surprisingly, this correction is less biased and has a smaller residual variance than any correction examined which incorporates depth information.
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