Clouds, aerosols and climate
The role of clouds in the climate system is still the largest uncertainty in the prediction of the future development of climate and in the understanding of the water cycle. Broadening the knowledge about cloud processes will not only deepen our understanding of the climate system, but it is an essential prerequisite to assessing the climate effects of transport emissions.
During the last years the Institute of Atmospheric Physics has attained important progress in the development of one and three-dimensional radiation transfer models and the airborne and space-borne remote sensing of aerosols, water and ice clouds. New passive instruments with high accuracy enable one to observe the life-cycle of clouds from space.Aerosols and clouds and their respective properties are simulated with global climate models and aerosol-cloud interactions and their role in the climate systems are explored. Aerosol modifies the radiation budget and the clouds, the latter because aerosol particles act as condensation and ice nuclei. A special aerosol module of the climate model simulates the atmospheric aerosol parameters. Current research activities aim at aerosol effects of cirrus clouds and the effects of particles from land, sea and air traffic. Comprehensive work concerns cirrus clouds because their complex physics is not yet adequately represented in the climate models so far.
First steps have been carried out to generate realistic virtual satellite images from the results of weather and climate models. These allow not only a direct comparison with real observations, but are also a powerful new method to test cloud parameterizations as well as to develop and verify algorithms for the remote sensing of clouds.
Our goal is the development of novel remote sensing procedures for clouds and aerosols by using the synergy of active and passive lidar, radar, imaging spectrometry and in-situ methods and to prepare the EarthCare mission. These methods allow a quantitative determination of vertical profiles of cloud properties and their effects on the radiation budget of the Earth from space.
Moreover, we are pursuing an improvement of the representation of the water budget in the upper troposphere in numerical weather prediction and climate models. In particular, we see chances because high performance computers now enable a direct simulation of clouds in ultra high-resolution model simulations which on the one hand can be validated by observational data and on the other hand can be used as a virtual reality to develop cloud parameterizations.