Solar Radiation & Radiative Transfer Research at ASRC

Researchers:  Lee HarrisonRichard Perez

Solar radiation research at the ASRC is focused on the accurate measurement and interpretation of measurements of solar and infrared radiation. The data collected include broadband and spectrally resolved ultraviolet, visible, and near-infrared radiation measurements and broadband terrestrial infrared radiation measurements.

Basic research in these areas is concerned with improving models of radiation transfer within the atmosphere through comparisons of models and accurate measurements. These models are used to predict the effects of climate change and must be validated in order to provide a basis for policy decisions. Applied research includes improving our knowledge of the available energy for solar energy production, for example, photovoltaic cell electricity generation.

We have developed the rotating shadowband radiometer and two spectral variants of it, a 7-filter and one spectrometer version, for widespread measurement of direct solar beam and scattered solar irradiance. The ultraviolet measurements are sponsored by the U.S. Dept. of Agriculture whose concern is the effects of changing ozone levels on the biosphere.

The earth's climate depends on a radiative-convective balance. Human beings have altered the climate by changing the atmospheric concentration of important trace gases (so called "greenhouse gases"). So researchers are interested in details of radiation transfer trying to understand how the earth's climate will be influenced.

Sun light affects weather, climate, and life on earth. In order to protect organism from 'harmful UV' in the range from 270 nm to 325 nm (UV-B), the sun's light output is filtered by ozone in the earth's atmosphere. Accurate measurements are nowadays so important to prove theoretical predictions of increased surface UV-B irradiance as a consequence of decreased stratospheric ozone ("ozone whole"). Further to understand the interactions with clouds, atmospheric aerosols and atmospheric trace gases.

ASRC researchers were responsible for the development and operation of the US Ultraviolet Reference and Research Spectroradiometric network, funded by the USDA. This network consists of six state-of-the-art spectroradiometers capable of scanning the full UV-B and UV-A spectrum at high-resolution. One of these instruments is displayed in the figure below. The aim of this network is to to act as ground calibration sites for satellite instruments studying ozone and UV, and to measure atmospheric trace gases accurately, including ozone, sulfur dioxide, nitrogen dioxide, hydroxl radical, bromine and chlorine monoxide, and potentially nitrous acid and formaldehyde.

The scientists play an important role in the USDOE Atmospheric Radiation Measurements Program (ARM). More detailled information about solar radiation, computing modeling, instrumentation and future programs is given here.