Comparison of COOP and new HCN-M temperature products

Since 2006, in cooperation with the National Weather Service and the National Climatic Data Center, Alabama has installed 3 Climate Reference Network stations and 17 modernized HCN stations. The HCN-M stations are equivalent to CRN standards for temperature and precipitation. With four years of parallel observations we are able to note significant differences between the original COOP and ASOS sites (some were old HCN) and the high-quality, well-sited HCN-M and CRN data. Summer TMax and TMin are compared to minimize differences due to a.m. observers in the COOP network. In general, the aspirated, well-sited HCN-M and CRN stations are cooler than the old COOP and ASOS readings. Among the effects we can determine are (a) the moderating effect of large lakes, (b) the warming effect of urban/near-building COOP (MMTS) sites, especially for TMin, and (c) the warming effect of ASOS siting over crushed limestone near runways.