CSPHOT

The Cimel sunphotometer (CSPHOT) is a multi-channel, automatic sun-and-sky scanning radiometer that measures the direct solar irradiance and sky radiance at the Earth’s surface. It takes measurements at predetermined discrete wavelengths in the visible and near-infrared parts of the spectrum to determine atmospheric transmission and scattering properties. Before 2017, ARM CSPHOTs only operated during daylight (sun above horizon). Starting in 2017, ARM deployed a new triple-mode sunphotometer model with solar and lunar irradiance and sky radiance modes to all ARM sites. The newer models allow for sun-sky-lunar measurements, enabling nighttime operation. Data from the older CSPHOTs and triple-mode models are available in the ARM Data Center.

• Aerosol optical depth
• Aerosol optical properties
• Particle number concentration
• Particle size distribution
• Precipitable water
• Shortwave narrowband radiance