Low-Cost Shortwave Spectroradiometer for Retrieval of Cloud Properties

Micro-networks to measure spatial variability of cloud optical properties would provide better understanding of cloud property heterogeneity and data to evaluate retrievals and simulations within larger areas of satellite sensor footprints and model grid boxes where sub-grid parameterization are necessary. This SBIR project will develop a compact, affordable instrument capable of measuring these properties, along with a means of calibrating the instrument in the field. Retrievals to produce continuous, high temporal resolution cloud optical properties and tools for in-field calibrations will remove two barriers to successful, routine use of shortwave spectral radiation measurements by the broader scientific community. A near infrared enhanced version of the cloud properties sensor was developed and deployed during Phase 1. Measurements of spectral radiance and retrievals of cloud optical depth, droplet effective radius and thermodynamic phase, the latter two a result of algorithm development during Phase 1, compared well with other co-located instruments. This and similar demonstration projects have garnered interest in this new instrumentation for science goals that can be explored in field deployments planned for the near future. The field calibrator concept, based on a small integrating sphere, a temperature-controlled LED, and a compound parabolic concentrator to increase the effective exit aperture of the sphere, was a partial success in Phase I testing. The Phase 2 project will build on these results by constructing four near infrared enhanced cloud properties sensors, possibly extending the range to 2500 nm for more robust phase retrieval. Field campaigns to evaluate spatial variability of cloud and precipitation processes and aerosol-cloud interactions in heterogeneous regions will benefit from this sensor. Campaigns planned for the Houston (convective aerosol interactions) and New York City (urban threat dispersion)willbenefit by adding this sensor to mobile units designed to measure boundary layer dynamics, clouds, and radiation in the complex urban environment for applications ranging from energy efficiency, to air quality, to national security. Data from these deployments will be used to further improve the retrieval algorithms. The field calibrator will be further developed with a focus on improving the uniformity and extending the wavelength coverage. The instrument and calibrator developed in this project will yield a significant level of direct commercial sales. The initial market will be atmospheric research groups at universities and national laboratories worldwide. Expanding into monitoring networks will constitute a potentially much larger market. The high time- and spatial-resolution of the cloud optical properties measured by this instrument will improve the predictability of climate models.