Comparisons of Ground-Based Observation Networks: USCRN and COOP

Photo of Cooperative Observer Program (COOP) and U.S. Climate Reference Network (USCRN) instruments

These pictures show some of instruments from the observing systems in the study. The exterior of a COOP cotton region shelter housing a liquid-in-glass thermometer is pictured in the top left, and a COOP standard 8-inch precipitation gauge is pictured in the top right. Three USCRN Met One fan-aspirated shields with platinum resistance thermometers are pictured in the middle. And, a USCRN well-shielded Geonor weighing precipitation gauge is pictured at the bottom.

In collaboration with the Cooperative Institute for Climate and Satellites–North Carolina, our scientists evaluated how diverse technological choices between two observing networks affect temperature and precipitation observations in a new study in the Journal of Atmospheric and Oceanic Technology titled Observational Perspectives from U.S. Climate Reference Network (USCRN) and Cooperative Observer Program (COOP) Network: Temperature and Precipitation Comparison.

The authors of the study compared pairs of U.S. Cooperative Observer Program (COOP) and U.S. Climate Reference Network (USCRN) stations located within 500 meters of each other across the United States. Their findings indicate that  COOP sensors in shields ventilated by natural wind flow generally reported warmer daily maximum temperatures (+0.48°C, +0.86°F) and cooler daily minimum temperatures (–0.36°C, –0.65°F) than the more advanced USCRN sensors with better solar shielding and fans to ventilate the instrument. For precipitation, COOP stations reported slightly more precipitation overall (1.5%).Network differences vary considerably among individual station pairs for both temperature and precipitation.

The existing COOP network was formed in the early 1890s to provide daily observations of temperature and precipitation across the United States. With over 100 years of manual observations collected from thousands of stations across the United States and its territories, the COOP network has evolved into the backbone for U.S. climate and weather assessments. However, observations of temperature and precipitation from the COOP network are taken daily from naturally ventilated temperature shields and unshielded precipitation gauges, which can result in observational uncertainty. In addition, the uncertainty can evolve over time with instrumentation and shielding upgrades and changes in primary observer and observation location. In order to account for these non-climatic shifts, automated corrections (known as homogenization) are required so as to not obscure long-term climate trends.

Advancements in observational technologies and measurement techniques were incorporated into the development of the USCRN in 2001. USCRN consists of 132 stations spread over the United States. Data for temperature and precipitation are collected much more frequently (sub-hourly) using more advanced, automated sensors that are shielded from weather conditions and installed redundantly, which limits the need for data corrections. This automated approach also reduces the impacts of inconsistencies in manual observations that occur in the COOP network.

Determining the variations in temperature and precipitation data between the networks allows scientists to develop an improved understanding of weather and climate data. The authors also find that USCRN validates the effectiveness of monthly COOP temperature homogenization efforts by confirming that during the time of network overlap, both homogenized COOP network and USCRN national temperature departures from normal are in strong agreement (for more information, see the National Temperature Index page).