Neural Networks: Cloud Parameterizations

Abstract

The role of clouds in the climate system is very complex and is the subject of much interest and research. Clouds interact nonlinearly with radiative, dynamical, chemical, and hydrological processes in the atmosphere on a wide range of temporal and spatial scales. Clouds play a fundamental role in controlling the amount of solar and infrared radiation available to the climate system. The radiative properties of clouds make them a key component in the energy balance of the Earth. In particular, clouds are involved in both heating and cooling in the determination of the Earth’s temperature. On average, roughly 50% of the Earth is covered by clouds. They contribute to the planet’s albedo by reflecting some incident sunlight (shortwave radiation) back to space (they also absorb some). However, they also partially block the escape of infrared radiation from below; that is, they exert a greenhouse effect on Earth. (Clouds are the primary contributors to the greenhouse effect.) They also emit some longwave radiation. Clouds also play an essential role in controlling the amount of moisture available to the climate system. Through precipitation, clouds serve as a conduit for the transfer of heat from the oceans to the atmosphere. They are also important in many chemical processes such as the absorption of water-soluble chemicals and pollutants in cloud droplets and their elimination by precipitation. See [Tre92] for further discussion.