| Summary: | Clouds are one of the less understood Earth's system components. In the Arctic, clouds play a fundamental role in many processes, and their characterization is crucial for the understanding of regional climate, ice melting, radiative budget, and related processes. Arctic cloud optical properties are measured from ground-based and space-borne instruments, but high surface reflectance values, a widespread condition at high latitudes but in general for snow and ice-covered regions, pose severe limitations to the application of many retrieval algorithms. These aspects have been investigated based on measurements made with a UV-VIS-NIR (300-950 nm wavelength range) spectrometer at the Thule High Arctic Atmospheric Observatory (76.5° N, 68.8° W, http://www.thuleatmos-it.it/) on the northwestern coast of Greenland. Continuous measurements are available for the 2022 season (March to September). In combination with radiation transfer simulations carried out with the libRadtran package, different retrieval algorithms for estimating the cloud optical thickness (COT) have been tested and compared. In addition to the spectral measurements, the information on the cloud base height provided by a ceilometer has been included to address the challenges posed by the high reflectance surfaces. Sensitivity studies on COT retrievals in different atmospheric and surface conditions will be presented, along with a case study.
|
|---|