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 Jul 29, 2015 Local Time
Graph of UV Index is not available for this location

Latest News
July 2015

Two students from Southern University and Agricultural and Mechanical Collge, Baton Rouge, Louisiana are visiting for the month of July. The focus of their research has been how urban forest influences UV radiation in an urban environment and how UV radiation affects a tree's health. We are helping them learn about our instrumentation and data processing procedures. Welcome.

Welcome aboard Scott Simpson. Scott will be working with George Janson and Bill Durham maintaining and updating our instrumentation, both in house and out in the field.

On April 9, 2015, Zhibin Sun was a Special Awards Judge for SPIE at the 60th Colorado Science and Engineering Fair (CSEF). The students were from high schools all around the state. Most of the awards focus on optics and photonics, but there were great projects in other fields as well.

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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.