Development of a sky imager for cloud classification and aerosol characterization (desarrollo de un sistema de cámara de cielo para la clasificación de nubes y la caracterización del aerosol)

Abstract

Cloud cover is a meteorological measurement registered by visual inspection hourly or 3 hourly in all the meteorological stations. Clouds affect the weather and also have an important role in the amount of solar radiation reaching the Earth's surface. Cloud cover can reduce the solar radiation up to 99% and the different types of clouds exert a key role in the energy budget since clouds reflect incoming sun radiation, but also because they absorb Earth infrared radiation. This influence of clouds on radiation is especially important in the ultraviolet because certain configurations of clouds in the sky (type and position) yields an amount of ultraviolet radiation greater than expected. On the other hand, the suspension of particles in the atmosphere (the atmospheric aerosol) also exerts an important role in the energy budget. Aerosol directly scatters and absorbs radiation and, indirectly affects clouds modifying their life time and radiative properties. Aerosol produces a cooling effect on the Earth system, opposite to the heating effect due to the CO2 and the rest of green house gases, but the uncertainty is large, and therefore more studies and instrumentation are required for its characterization. Because of the importance of cloud cover and other macrophysical properties of clouds, and the importance of the aerosol in the radiative transfer processes and energy budget, we propose the design of a device, a sky imager, for the record of sky conditions. On one hand, the information on cloud cover and other macrophysical properties of clouds is needed for meteorological studies and studies on the cloud effect on solar radiation. On the other hand, the importance of the aerosol on the radiative budget requires establishing new methods for its characterization. While sky imager systems have been design primarily for cloud cover characterization, in this work we also propose the use for aerosol characterization.