Coupled Chemistry in the Met Office UM: current and in a future extended (thermosphere) version

Transcription

1 Coupled Chemistry in the Met Office UM: current and in a future extended (thermosphere) version David Jackson QEPPA Meeting, Lancaster 13/03/2013

2 Overview What is the UM? UKCA chemistry Link to QEPPA goals Extended UM: Motivation Development including: What chemistry scheme? Link to QEPPA goals Summary

3 What is the Unified Model (UM)? Met Office weather and climate model Horizontal resolution N96- N768 (~ km) Vertical levels: 0-~80-85 km 70 and 85-level versions resolution: ~100m near surface; 4-8 km at top Navier Stokes equations with comprehensive physical parametrizations (radiation, gravity waves..) and coupled chemistry Semi-Lagrangian, deep atmosphere, non-hydrostatic dynamical cores (current and EndGame )

4 UM Coupled Chemistry - UKCA UKCA is a chemistry/aerosol scheme that runs within the UM Several variants of scheme Troposphere: Standard; with Isoprene; Extended (85(46) species, 63(26) advected tracers, 243(129) reactions); Regional AQ Stratosphere: 41 species, 36 advected tracers, 169 reactions + simple Trop chemistry (Morgenstern et al, 2009) Trop+Strat; merging of Trop+Isoprene and Strat schemes Has run with low top (~38km) and high top (~85km) versions of the UM Stratosphere scheme focuses on ozone depletion / multi year (eg 150 years) climate change runs.

5 UM Coupled Chemistry - UKCA Stratosphere version run up to ~85km (Morgenstern et al, 2009) Mesospheric constituents OK eg NOx shape right, but too large in mesosphere Little useful purpose above ~ 1hPa? No specific ion and / or MLT chemistry Morgenstern et al, 2009

6 Link to QEPPA goals NRT Level 2 product EP characteristics Not possible with existing UKCA-UM Estimates of NOx production during substorms and storms Possible with existing UKCA-UM, if NOx perturbation fields for the stratosphere can be produced (eg using FinROSE transport) Possible climate or seasonal forecast simulations Get first indication of impacts and whether to pursue experiments

7 Extended UM Motivation Met Office Ambition provide operational space weather forecasts for the UK Currently: Space weather forecasters providing alerts to selected customers (mainly UK Gov) from NOAA, satellite data sources CME forecasts from WSA Enlil (operational next month) European-area ionospheric TEC nowcasts from MIDAS (Bath Uni.) (near operational) No coupling between solar, geospace, thermosphere / ionosphere and lower atmosphere Pathway to improved forecasts requires coupled Sun to Earth models plus DA An Extended UM (surface to exobase) would be part of this coupled system Benefit to seasonal forecasts via EPP and strat/trop coupling is (currently) secondary motivation (for Extended UM)

8 Motivation Coupling between lower atmosphere and thermosphere / ionosphere is very important Non-migrating tides (DE3) important for w4 structure in EIA non-migrating tide generation linked to zonally-asymmetric forcing due to tropical convection? Other studies show strat. sudden warming / ionosphere linkages In general, PW / GW / tide interaction need to be properly represented IMAGE composite of nm O airglow ( km) in March April 2002 and modelled diurnal temperature oscillation at 115 km - Immel et al, 2006

9 Motivation Impact of thermosphere & ionosphere on lower atmosphere SEPs lead to NO x increase and O 3 decrease in mesosphere / stratosphere SPEs and EEs impact at different heights and transport is important Stratospheric ozone changes may affect tropospheric forecasts at medium/extended range, but further research is needed to understand this (eg Simpson et al, 2010) Solar cycle influence on European winter climate (Ineson et al, 2011, Seppala et al, 2009, Baumgaertner et al, 2011) Radiation change => Weak vortex=-ve NAO or more complex? Ozone changes above 60 N magnetic latitude. Below each representation of the measurements the corresponding model results are shown. (Rohen et al, 2005 JGR) MSLP (solar min-solar max) a) model; b) ERA. NH winter (Ineson et al, 2011)

10 Extended UM Specifications Height range limited to region where Navier-Stokes equations are valid the exobase (~ km). Above here molecules follow ballistic trajectories and air no longer can be treated as continuous fluid Coupling between lower and upper levels needs to be represented accurately and self-consistently Comprehensive physics and chemistry needs to be included (eg gravity waves, non-lte radiation) Coupled ionosphere model vital for space weather forecasts but development track largely outside that for extended UM

11 Extended UM - R&D Outline Two Track approach 1. Robustness and Extension of Dynamical Core UM dynamics unlikely to run stably above ~ 120 km - develop dynamics-only TestBed to test and modify dynamics code 2. Intermediate Extended UM Full UM with upper boundary raised from ~85 km to ~ km Enables assessment of UM tidal (and other wave) climatology (and cf with meteor radar) in km region. Key for ionosphere coupling Enables testing of new physics/chemistry relevant to MLT (eg non- LTE radiation). First step to blending new schemes with 600 km UM with modified EndGame dynamics

12 Intermediate Extended UM Physics, Chemistry options Thermosphere-specific physics Non-LTE +EUV radiation gravity wave drag (E field, Joule heating & ion drag) Chemistry scheme. Need earlier decision on Import (eg MOZART (WACCM))? Or extend UKCA?

13 New Chemistry WACCM/MOZART +SIC? (+)Chemistry scheme in development (+)Some UK community willingness/expertise to import into UM (-)Doesn t fit well in UM structure ( another chemistry scheme!! ) UKCA Extension (+)Neater software / model development solution (-)More work to develop MLT / ion chemistry (?)Need to engage UKCA experts

14 Non-LTE radiation Ready to start this: Have Fomichev code important non-lte effects in IR (15µm CO2 and 9.6 µ um O3) and NIR (CO2) Merge into offline UM (Edwards-Slingo) radiation code Validate by comparing with full non-lte profiles Fix any errors/problems arising then merge the resulting code into the full UM Next steps: CO2 needed for levels up to ~120 km. For higher extension need NO (Kockarts, 1980?) and O (Bates, 1951?) SW non-lte (eg O3, O2): neglect or modify LTE values by thermalisation efficiency EUV, chemical heating, solar variation(f10.7) later (when chemical module being added) after Roble et al (1987)

15 Link to QEPPA goals NRT Level 2 product EP characteristics Possible with Extended UM if appropriate chemistry scheme in place Scope for improved forecasts Estimates of NOx production during substorms and storms But! Scope to re-run existing UKCA-UM climate or seasonal forecast runs with Extended UM, and to compare with results with UM simulations using NRT Level 2 product timescale for Extended UM development likely to be longer than QEPPA

16 Summary With existing UKCA-UM, it is possible to use NOx outputs from QEPPA A future Extended UM (with appropriate chemistry) could also use QEPPA NRT Level 2 EP outputs Future Extended UM may not be available until after QEPPA end but clear track for future research programme aimed at properly quantifying EP impacts on seasonal forecasts

17 Questions and answers