Annual sum values represent an accumulation over time. By integrating the irradiances over the number of seconds in a day, the daily sum of radiant energy in units of Joules per square meter is obtained. Then adding together the daily values for the entire year yields amount of radiant energy received during the year. The Caldwell biological spectral weighting function is a generalized action spectrum relating to plant damage from UV radiation exposure encompassing wavelengths from 280 to 313 nm and has been widely used to predict the consequences of ozone depletion.

UV Index for Apr 17, 2015 Local Time
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Latest News
April 2015

Wei Gao and Mike Coughenour attended the Winter Business Meeting for AmericaView on February 22-26. The first day of meetings was held at USGS Headquarters in Reston, VA and the second was held at the St. Regis Hotel in Washington, D.C.

George Janson travel to several of our UV-B monitoring sites, Starkville, Mississippi; Logan, Utah; Queenstown, Maryland; Beltsville, Maryland and NASA-Goddard, Maryland. He performed routine maintenance on our instrumentation. Bill Durham serviced our instruments at the Las Cruces, New Mexico site.

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Picture of our instruments at various locations
2007 Annual Caldwell Across the United States


The UV-B Monitoring and Research Program (UVMRP) is a data collection and research program of the United States Department of Agriculture (USDA), headquartered at Colorado State University in Fort Collins, Colorado.

The UVMRP supports two unique and complimentary program components:

Integrated Agricultural Impact Assessment System

Agriculture is entering a critical period with regard to climate change, crop stress, and potential related impacts to crop productivity. Decision makers need reliable and relevant crop yield and economic assessment tools. The objective of this UVMRP program component is to develop an Integrated Agricultural Impact Assessment System. This system will couple the Earth's climate, ultraviolet-visible solar radiation, and comprehensive crop growth models, and assimilating satellite and in situ observations to study climate-crop interactions and related economic impacts stemming from crop responses to a wide range of stressors. Common stressors include temperature, moisture, nutrients, UV radiation, CO2 concentration, aerosols and other air pollutants. Please click on the above Agricultural Impact for more information.

UV-B Monitoring Network

High-energy ultraviolet solar radiation can significantly damage plants, crops, animals, and ecosystems, alone or in combination with other environmental stress factors such as temperature and moisture. To address these concerns, in 1992, the USDA established the UV-B Monitoring and Research Program at Colorado State University to provide cost-effective monitoring of UV-B levels across the United States. The program's primary objective is continued operation of the national network of UV-B monitoring instruments to deliver high-quality data, data products, and services in support of agricultural research. In particular, we quantify the geographic distribution of UV-B solar irradiance; the effects of increased or diminished UV-B on crops, native and invasive plants, and animals; and facilitate the use of these measurements directly, or as inputs to climate and crop models.

These data are collected automatically every night, processed for quality control, and made available on this web site, typically within one day of its collection. Most data are available back through 1997, with some additional data available back to 1993. Please click on the above Monitoring Network for information about our locations and instruments. Please click on the above Data Download for our data and data products.