Analysis of the impacts of station exposure on the U.S. Historical Climatology Network temperatures and temperature trends

The recently concluded Surface Stations Project surveyed 82.5% of the U.S. Historical Climatology Network (USHCN) stations and provided a classification based on exposure conditions of each surveyed station, using a rating system employed by the National Oceanic and Atmospheric Administration (NOAA) to develop the U.S. Climate Reference Network (USCRN). The unique opportunity offered by this completed survey permits an examination of the relationship between USHCN station siting characteristics and temperature trends at national and regional scales and on differences between USHCN temperatures and North American Regional Reanalysis (NARR) temperatures. This initial study examines temperature differences among different levels of siting quality without controlling for other factors such as instrument type. Certain temperature trends are found to vary systematically with siting quality, and an initial attempt is made to quantify temperature biases.