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Keywords:

  • solarterrestrial relationship;
  • CAWSES;
  • introduction

[1] In the special section on CAWSES (Climate and Weather of the Sun Earth System) a total of 19 papers are published covering several aspects of Sun-Earth coupling. Six papers concentrate on summer mesospheric ice clouds including detection by satellites, radar-based derivation of particle properties, and water vapor observations in the mesosphere. Solar radiation affects ice clouds on time scales of the 11 year solar cycle and 27 days. Stratospheric shrinking contributes significantly to long-term trends of ice clouds. The seasonal variability of smoke particles is confirmed to be impacted by global circulation. Six papers address the external forcing of the atmosphere caused by the Sun. The relevance of radionuclei and solar radiation spectral irradiance is presented. The impact of precipitating energetic solar particles on trace gas concentrations is studied. Ion chemistry and electron production can be important to destroy ozone in the mesosphere and upper stratosphere. Strong solar events can reduce ice clouds on short time scales owing to dynamical feed back mechanisms. The 27 day solar signal is identified in ozone concentration using satellite measurements. Model studies show that the dynamical response of the stratospheric polar vortex to solar cycle forcing depends on the phase of the quasi-biennial oscillation. The year 2009 was a remarkable exception from this rule reinforcing natural variability. Regarding centennial time scales it is shown that changes in the stratosphere can influence tropospheric circulation. Tides have extensively been studied within CAWSES. As is demonstrated, nonmigrating tides originating in the troposphere can propagate into the thermosphere.