ROSES ID: NNH15ZDA001N Selection Year: 2015
Program Element: SCOSTEP/VarSITI
Principal Investigator: Han-Li Liu
Affiliation(s): University Corporation For Atmospheric Research (UCAR)
Project Member(s):
McInerney, Joe M. Co-I
Solomon, Stanley C. Co-I University Corporation For Atmospheric Research (UCAR)
Rempel, Matthias Co-I University Corporation For Atmospheric Research (UCAR)
Qian, Liying Co-I University Corporation For Atmospheric Research (UCAR)
Summary:
Using a state-of-the-art solar radiation MHD model, we will estimate the photospheric total solar irradiance (TSI) and chromospheric ultra-violet (UV) emissions under extreme quiet solar conditions. The proposed simulation employs very high spatial resolution to calculate changes in TSI from photospheric variations with different magnetic field configurations, and solar spectral irradiance (SSI) by performing radiative transfer in a few frequency bands. The total chromospheric variation will be estimated from these models by using the upward directed Poynting flux above the photosphere as a proxy, and can be related to the variation of photospheric TSI variation. These physically self-consistent estimates will then be used to drive the National Center for Atmospheric Research (NCAR) Whole Atmosphere Community Climate Model with thermosphere and ionosphere extension (WACCM-X) to study the implications for the climate of the whole atmosphere system, including the bottom-up and top-down interactions of the ionosphere, thermosphere, mesosphere, stratosphere and troposphere. This will enable us to quantify the atmospheric climate state under extreme quiet solar conditions using physically-based minimum irradiance estimates, and will provide insights into the solar-climate connection. The solar TSI and SSI estimates will first be validated against existing observations under nominal solar minimum conditions, and these observed solar spectra be used to drive WACCM-X baseline simulations. The WACCM-X baseline simulations will be compared to the Chemistry-Climate Model Initiative (CCMI) results for validating the stratosphere, and to measurements of the mesosphere and lower thermosphere by the SABER instrument on the TIMED satellite. We will then perform WACCM-X simulations under extreme quiet solar conditions, using estimates obtained from the solar radiation MHD simulation. The WACCM-X simulations will be compared with the baseline simulations, to analyze the differences in the lower, middle and upper atmosphere. The unique capability of WACCM-X will enable us to investigate the mechanisms responsible for these changes, including direct radiative impact, and upward and downward coupling processes.