Surface air temperature records biased by snow-covered surface

Abstract

The radiation shield bias of the maximum and minimum temperature system (MMTS) relative to the US Climate Reference Network (CRN) was investigated when the ground surface is snow covered. The goal of this study is to seek a debiasing model to remove temperature biases caused by the snow-covered surface between the MMTS and the US CRN. The side-by-side comparison of air temperature measurements was observed from four combinations of temperature sensor and temperature radiation shield in both MMTS and US CRN systems: (a) a standard MMTS system; (b) an MMTS sensor housed in the CRN shield; (c) a standard US CRN system; and (d) a CRN temperature sensor housed in the MMTS shield. The results indicate that the MMTS shield bias can be seriously elevated by the snow surface and the daytime MMTS shield bias can additively increase by about 1 °C when the surface is snow covered compared with a non-snow-covered surface. A non-linear regression model for the daytime MMTS shield bias was developed from the statistical analysis. During night-time, both the cooling bias and the warming bias of the MMTS shield existed with approximately equal frequencies of occurrence. However, the debiased night-time data based on the linear model developed in this study was less significant due to relatively smaller biases during night-time. The debiasing model could be used for the integration of the historical temperature data in the MMTS era and the current US CRN temperature data and it also could be useful for achieving a future homogeneous climate time series. This article is a US Government work and is in the public domain in the USA. Published in 2005 by John Wiley & Sons, Ltd.