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Nowcast and short-term forecast in the middle atmosphere based on the observed UV irradiance

The solar irradiance variability plays a dominant role in the formation of the neutral and ionic composition of the mesosphere. Ionospheric D-region (50-90 km) has substantial effects on the propagation of high frequency radio waves during day time, because the ions formed by solar irradiance and charged energetic particles are able to almost completely absorb electromagnetic waves with frequency up to ~7 MHz. The solar irradiance originating by the Lyman alpha emission is of great importance not only as a source of ionization of the D-region, but also as a major contributor to the dissociation of water vapor and other neutral constituents and as the direct source of heat in the mesosphere. The temperature and the state of the neutral compounds are important for the ionic components in the mesosphere. A better measurement accuracy of for well defined Sun conditions (presently known to an accuracy of 20%) and a better determination of its variations in short- and intermediate-term [27-day Sun rotation cycle and harmonics] (up to 30%) and in long term [11-year solar cycle] (up to a factor of 2.5) is fundamental for an accurate understanding and modeling of the chemistry, thermodynamics and ionization in the mesosphere.
    The 200-220 nm channel of LYRA covers the Herzberg continuum, which is important for the creation of atomic oxygen and ozone in the stratosphere. High frequency and accurate LYRA data together with statistical prediction tools being implemented in a chemistry-climate model (CCM) can facilitate the nowcast and short-term forecast of the neutral and ionic states of the mesosphere.

CCM SOCOL has been extended the model capabilities by the inclusion of the ion chemistry. The extended chemistry-ionosphere-climate model (CICM) used for nowcast and short-term forecast of the neutral and ionic state of the mesosphere on the basis of solar irradiance data measured by LYRA instrument. The LYRA observations serve as input data for CICM. The final aim of this project is to have a data reduction pipeline ready that will produce in near real time from the LYRA irradiance observations a prediction of the state of the upper atmosphere. 

 

 

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