Preprints
https://doi.org/10.5194/angeo-2021-21
https://doi.org/10.5194/angeo-2021-21

  13 Apr 2021

13 Apr 2021

Review status: a revised version of this preprint is currently under review for the journal ANGEO.

Analysis of Migrating and Non-Migrating Tides of the Extended Unified Model in the Mesosphere and Lower Thermosphere

Matthew J. Griffith1 and Nicholas J. Mitchell2,3 Matthew J. Griffith and Nicholas J. Mitchell
  • 1Department of Mathematical Sciences, University of Bath, Claverton Down, Bath, BA2 7AY, UK
  • 2Department of Electronic & Electrical Engineering, University of Bath, Claverton Down, Bath, BA2 7AY, United Kingdom
  • 3British Antarctic Survey, High Cross, Madingley Rd, Cambridge, CB3 0ET, United Kingdom

Abstract. Atmospheric tides play a key role in coupling the lower, middle and upper atmosphere/ionosphere. The tides reach large amplitudes in the Mesosphere and Lower Thermosphere (MLT) where they can have significant fluxes of energy and momentum and so strongly influence the coupling and dynamics. The tides must therefore be accurately represented in Global Circulation Models (GCMs) that seek to model the coupling of atmospheric layers and impacts on the ionosphere. The tides consist of both migrating (sun-following) and non-migrating (not sun-following) components, both of which have important influences on the atmosphere. The Extended Unified Model (ExUM) is a recently developed version of the Met Office's Unified Model GCM which has been extended to include the MLT. Here, we present the first in-depth analysis of migrating and non-migrating modes in the ExUM. We show that the ExUM produces both non-migrating and migrating tides in the MLT of significant amplitude across a rich spectrum of spatial and temporal modes. The dominant non-migrating modes in the MLT are found to be the DE3, DW2 and DW3 in the diurnal tide and the S0, SW1 and SW3 in the semidiurnal tide. These modes can have monthly mean amplitudes at a height of 95 km as large as 35 ms−1 / 10 K. All the non-migrating modes exhibit a strong seasonal variability in amplitude and significant short-term variability is evident. Both the migrating and non-migrating modes exhibit notable variation with latitude. For example, the temperature and wind diurnal tides maximise at low latitudes and the semidiurnal tides include maxima at high latitudes. Our results demonstrate the capability of the ExUM for modelling atmospheric migrating and non-migrating tides and lays the foundation for its future development into a whole atmosphere model. To this end, we make specific recommendations on further developments which would improve the capability of the model.

Matthew J. Griffith and Nicholas J. Mitchell

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on angeo-2021-21', Anonymous Referee #1, 17 May 2021
    • AC1: 'Reply on RC1', Matthew Griffith, 23 Jul 2021
  • RC2: 'Comment on angeo-2021-21', Anonymous Referee #2, 02 Jul 2021
    • AC2: 'Reply on RC2', Matthew Griffith, 23 Jul 2021

Matthew J. Griffith and Nicholas J. Mitchell

Matthew J. Griffith and Nicholas J. Mitchell

Viewed

Total article views: 521 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
447 59 15 521 5 5
  • HTML: 447
  • PDF: 59
  • XML: 15
  • Total: 521
  • BibTeX: 5
  • EndNote: 5
Views and downloads (calculated since 13 Apr 2021)
Cumulative views and downloads (calculated since 13 Apr 2021)

Viewed (geographical distribution)

Total article views: 498 (including HTML, PDF, and XML) Thereof 498 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 29 Jul 2021
Download
Short summary
There is great scientific interest in extending atmospheric models such as the Met Office’s Unified Model upwards to include the upper atmosphere. Atmospheric tides are an important driver of circulation at these greater heights. This study provides a first in depth analysis of the migrating and non-migrating components of these tides, examining important tidal properties. Our results show that the ExUM produces a rich spectrum of spatial modes, with non-migrating modes of significant amplitudes