Dr Scott Osprey FRMetS

Abstract:

An examination of zonal asymmetries in meridional momentum flux reaching the mesosphere is made using the Hines Doppler spread parameterization of gravity waves. As expected a general correspondence is seen between wave one wind in the stratosphere and wave one signals in gravity wave momentum flux leaving the stratosphere. However, a significant difference is the presence of wave one features in the gravity-wave momentum flux at 56 km and ∼70°N during mid-summer which contrast with minimal signals in stratospheric wave one wind. The prominence of this feature is accounted for by a significant wave one Brunt-Väisälä feature at the tropopause amplifying a wave one signal in momentum flux which can then propagate to great heights. Such a feature could result in mesospheric planetary waves which are coupled to the tropopause forcing without intervening planetary wave signals in the stratosphere.

Abstract:

rcp45 is an experiment of the CMIP5 - Coupled Model Intercomparison Project Phase 5 (http://cmip-pcmdi.llnl.gov/cmip5/). CMIP5 is meant to provide a framework for coordinated climate change experiments for the next five years and thus includes simulations for assessment in the AR5 as well as others that extend beyond the AR5. 4.1 rcp45 (4.1 RCP4.5): Future projection (2006-2100) forced by RCP4.5. RCP4.5 is a representative concentration pathway which approximately results in a radiative forcing of 4.5 W m-2 at year 2100, relative to pre-industrial conditions. RCPs are time-dependent, consistent projections of emissions and concentrations of radiatively active gases and particles. Experiment design is described in detail in http://cmip-pcmdi.llnl.gov/cmip5/docs/Taylor_CMIP5_design.pdf and the list of output variables and their temporal resolutions are given in http://cmip-pcmdi.llnl.gov/cmip5/docs/standard_output.pdf . The output is stored in netCDF format as time series per variable in model grid spatial resolution. For more information on the Earth System model and the simulation please refer to the CIM repository.