Simulated satellite image for the SEVIRI sensor aboard the satellite Meteodat-9. Shown is the brightness temperature in channel 13.4. It is a scene showing the atmosphere over Germany on May, 15 2012 at 12:00. Clouds are associated with lower brightness temperatures, as a consequence they appear as darker structures.
At the Institute of Atmospheric Physics numerical models including different methods are used to study radiative transfer in the atmosphere and the interaction between radiation and clouds or aerosol. Examples for applied methods are DISORT (Discrete Ordinate), a fast two-stream variant for the calculation of radiation fluxes, and MYSTIC (Monte Carlo Code for the Physically Correct Tracing of Photons in Cloudy Atmospheres), which are part of the program package libRadtran (Library for Radiative Transfer). The wavelength range available for simulations includes the ultraviolet, visible, and infrared spectral region. While the first two methods solve one-dimensional problems, MYSTIC simulates radiative transfer in three dimensions and is able to consider polarization effects. An additional model based on the matrix operator method (MOM) is also applied.
Results of radiative transfer calculations can be used to find answers to scientific questions concerning clouds and aerosol, possibilities of remote sensing by satellites, and to develop corresponding algorithms. Main aspects of science in the department are the properties of ice clouds, their life cycle and the underlying interactions as well as anthropologically generated ice clouds amongst others. This includes contrails and cirrus clouds emerging from these. In the context of development and validation of algorithms designed to derive parameters of clouds and radiation budget the radiative transfer models are applied as well.
To increase the gain of solar power plants, one aim is to optimize the nowcasting of solar radiation reaching the Earth’s surface. Circumsolar radiation is also considered when calculating the irradiation using MYSTIC. Besides that, an algorithm for determination of UV radiation was developed by means of the matrix operator method.
Concerning the mentioned fields of work, a co-operation between the department and the Meteorological Institute of the Ludwig-Maximilians-Universität München (MIM) exists, where libRadtran is developed at the Chair of Experimental Meteorology (Prof.Mayer).