Low Cost Shortwave Spectroradiometer for Retrieval of Cloud Properties

One of the stated goals in the Atmospheric Radiation Measurement ARM) Climate Research Facility Decadal Vision is to “continue to build excellence in ground-based measurements.1” In particular, we plan to address the need for improved measurements of cloud properties. Clouds play a significant role in Earth’s radiation budget. While cloud property sensors have long existed, they tend to be costly to produce and maintain. We propose to deploy our prototype visible VIS) and near infrared NIR) band spectroradiometer sensor at ARM’s Southern Great Plains Facility. Our sensor measures absolute spectral radiance in the two bands and will retrieve cloud optical depth COD), droplet effective radius and thermodynamic phase. Our prototype is built predominantly from off-the-shelf components and uses uncooled spectrometers. A lower cost, easy to use sensor could allow deployment at many more sites for greater spatial coverage. Approximately five years ago, Aerodyne developed a VIS only version of the cloud property sensor retrieves only COD.This sensor his been deployed successfully at multiple field campaigns, including two Department of Energy campaigns. Recently, we upgraded the sensor to include, a NIR spectrometer that should allow the retrieval of effective radius and phase in addition to COD. We are proposing to deploy this sensor at ARM’s Southern Great Plains atmospheric observatory and perform extensive data and retrieval comparisons with several baseline sensors and value-added products.Furthermore, we are proposing an additional, much smaller, task to investigate the potential utility of an LED-based field calibration capability. The most immediate commercial opportunity would be the sale of instruments for deployment at the National Oceanic and Atmospheric Administration’s Surface Radiation Budget SURFRAD) sites. Our target cost for the sensor is close to that of an Aerosol Robotic Network AERONET) site, ideally making feasible widespread deployment.