The Shortwave Array Spectroradiometer – Zenith (SASZE) measures the zenith sky shortwave radiance over the spectral range from the near infrared to the ultraviolet. The SASZE incorporates two Avantes fiber-coupled spectroradiometers (Avaspec ULS 2048 CCD and Avaspec NIR256-1.7) for visible and near-infrared detection in the wavelength range 350–1700 nm. The sampling frequency is 1 Hz. The spectral resolution is 2.4 nm for the ULS 2048 CCD and 6 nm for the NIR256-1.7. The light collector has a narrow field of view (1° full-angle) collimator at the front end of a high-grade fiber optic. The SASZE measures sky radiance throughout the day including throughout twilight before the sun has risen and after it has set. The SASZE rack with spectroradiometers and data acquisition system is located within a temperature-controlled building isolated from the elements.
The SAS measurements can be used to retrieve cloud optical depth, particle size and cloud water path, test the cloud optical depth retrieval for overcast and broken cloud fields, validation/comparison with SGP surface remote sensors and future cloud IOP campaigns, multivariate analysis to derive information content in hyper spectral data sets and to improve cloud retrieval algorithm development, and compare with radiative transfer models for testing and validating retrieval procedures.