Parameterization of Cn2 using data from operational weather stations

• Applicants: Dr. Alexander Graf; Professor Dr. Clemens Simmer
• Subject Area: Atmospheric Science
• Term: from 2013 to 2014
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 246652336

The lower atmosphere, in which most human activities take place, is a strongly turbulent layer. Among others, temperature and humidity vary on a range of scales. The temperature and humidity variations cause variations in the refractive index of air: scintillations. This is visible to the eye as the shimmering over a warm road on a summer day. Similar to the degradation of our visual perceptions by scintillations, also the image quality of imaging instruments (e.g. for monitoring and reconnaissance, astronomy) and the signals of communication systems (e.g. radio links) are degraded.The strength of scintillations (which we will loosely refer to as optical turbulence) can be quantified with the structure parameter of the refractive index of air. It not only depends on the strength of turbulent temperature and humidity variations, but it is also different for different wavelengths. People who use or plan to install systems that rely on the propagation of electromagnetic radiation need to know what kind of optical turbulence they can expect (in the planning phase), or what they encounter during operation. Therefore, there is a need for simple but robust methods to determine the structure parameter of the refractive index based on readily available data (e.g. standard weather station data). Such a method could both be used to derive the climatology of the structure parameter for a given location, and to determine the real-time value during operation.

• DFG Programme: Research Grants
• International Connection: Netherlands
• Participating Person: Professor Dr. Arnold F. Moene