Geoscientific Model Development Evaluation of the new UKCA climate-composition model – Part 1 : The stratosphere

The UK Chemistry and Aerosols (UKCA) model is a new aerosol-chemistry model coupled to the Met Office Unified Model capable of simulating composition and climate from the troposphere to the mesosphere. Here we introduce the model and assess its performance with a particular focus on the stratosphere. A 20-year perpetual year-2000 simulation forms the basis of our analysis. We assess basic and derived dynamical and chemical model fields and compare to ERA-40 reanalyses and satellite climatologies. Polar temperatures and the lifetime of the southern polar vortex are well captured, indicating that the model is suitable for assessing the ozone hole. Ozone and long-lived tracers compare favourably to observations. Chemical-dynamical coupling, as evidenced by the anticorrelation between winterspring northern polar ozone columns and the strength of the polar jet, is also well captured. Remaining problems relate to a warm bias at the tropical tropopause, slow ascent in the tropical pipe with implications for the lifetimes of long-lived species, and a general overestimation of ozone columns in middle and high latitudes.

[1]  Richard S. Stolarski,et al.  Search for evidence of trend slow-down in the long-term TOMS/SBUV total ozone data record: the importance of instrument drift uncertainty and fingerprint detection , 2006 .

[2]  Elizabeth C. Kent,et al.  Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century , 2003 .

[3]  D. Rind,et al.  Intercomparison of stratospheric water vapor observed by satellite experiments: Stratospheric Aerosol and Gas Experiment II versus Limb Infrared Monitor of the Stratosphere and Atmospheric Trace Molecule Spectroscopy , 1993 .

[4]  Hongwoo Park,et al.  The Solar Backscatter Ultraviolet (SBUV) and Total Ozone Mapping Spectrometer (TOMS) experiment , 1978 .

[5]  G. Martin,et al.  A New Boundary Layer Mixing Scheme. Part I: Scheme Description and Single-Column Model Tests , 2000 .

[6]  Martyn P. Chipperfield,et al.  Multiannual simulations with a three‐dimensional chemical transport model , 1999 .

[7]  Adam A. Scaife,et al.  Quasi‐biennial oscillation in ozone in a coupled chemistry‐climate model , 2003 .

[8]  Olaf Morgenstern,et al.  Technical Note: Description and assessment of a nudged version of the new dynamics Unified Model , 2007 .

[9]  J. Pyle,et al.  Changes in tropospheric ozone between 2000 and 2100 modeled in a chemistry‐climate model , 2003 .

[10]  J. A. Pyle,et al.  A two‐dimensional mean circulation model for the atmosphere below 80km , 1975 .

[11]  O. Wild,et al.  Excitation of the primary tropospheric chemical mode in a global three-dimensional model , 2000 .

[12]  P. Braesicke,et al.  Changing ozone and changing circulation in northern mid‐latitudes: Possible feedbacks? , 2003 .

[13]  D. Waugh.  Atmospheric dynamics: The age of stratospheric air , 2009 .

[14]  James M. Russell,et al.  The Halogen Occultation Experiment , 1993 .

[15]  B. Naujokat,et al.  An Update of the Observed Quasi-Biennial Oscillation of the Stratospheric Winds over the Tropics , 1986 .

[16]  Oliver Wild,et al.  The ASAD atmospheric chemistry integration package and chemical reaction database , 1997 .

[17]  S. Solomon.  The Physical Science Basis : Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change , 2007 .

[18]  David John Lary,et al.  Diffuse radiation, twilight, and photochemistry — I , 1991 .

[19]  M. Chipperfield,et al.  Model sensitivity studies of Arctic ozone depletion , 1998 .

[20]  P. Braesicke,et al.  The World Avoided by the Montreal Protocol , 2008 .

[21]  A. Staniforth,et al.  A new dynamical core for the Met Office's global and regional modelling of the atmosphere , 2005 .

[22]  Rolando R. Garcia,et al.  Simulation of secular trends in the middle atmosphere, 1950–2003 , 2007 .

[23]  Timothy M. Hall,et al.  Evaluation of transport in stratospheric models , 1999 .

[24]  J. Penner,et al.  Global atmospheric chemistry: Integrating over fractional cloud cover , 2007 .

[25]  Volker Grewe,et al.  Assessment of temperature, trace species, and ozone in chemistry-climate model simulations of the recent past , 2006 .

[26]  Ulrike Langematz,et al.  Update on the global ozone climatology and on concurrent ozone and temperature trends , 1995, Remote Sensing.

[27]  Dudley E. Shallcross,et al.  Evaluation of modelled O3 using MOZAIC data , 1998 .

[28]  A. Priestley.  A Quasi-Conservative Version of the Semi-Lagrangian Advection Scheme , 1993 .

[29]  K. Carslaw,et al.  Evaluation of a global aerosol microphysics model against size-resolved particle statistics in the marine atmosphere , 2007 .

[30]  R. A. Cox,et al.  Evaluated kinetic and photochemical data for atmospheric chemistry: Supplement V , 1996 .

[31]  E. Fleming,et al.  Two-dimensional model simulations of the QBO in ozone and tracers in the tropical stratosphere , 2002 .

[32]  J. Houghton,et al.  Climate change 2001 : the scientific basis , 2001 .

[33]  M. Prather,et al.  Fast-J2: Accurate Simulation of Stratospheric Photolysis in Global Chemical Models , 2002 .

[34]  Richard Swinbank,et al.  Impact of a Spectral Gravity Wave Parameterization on the Stratosphere in the Met Office Unified Model , 2002 .

[35]  T. Shepherd,et al.  Overview of the New CCMVal reference and sensitivity simulations in support of upcoming ozone and climate assessments and the planned SPARC CCMVal report , 2008 .

[36]  A. Slingo,et al.  Studies with a flexible new radiation code. I: Choosing a configuration for a large-scale model , 1996 .

[37]  Mark Lawrence,et al.  The atmospheric chemistry general circulation model ECHAM5/MESSy1: consistent simulation of ozone from the surface to the mesosphere , 2006 .

[38]  Stuart Webster,et al.  Improvements to the representation of orography in the Met Office Unified Model , 2003 .

[39]  R. Stolarski,et al.  Changes in Column Ozone Correlated with the Stratospheric EP Flux , 2002 .

[40]  D. Rind,et al.  A simple lightning parameterization for calculating global lightning distributions , 1992 .

[41]  David W. J. Thompson,et al.  Interpretation of Recent Southern Hemisphere Climate Change , 2002, Science.

[42]  A. Sterl,et al.  The ERA‐40 re‐analysis , 2005 .