!  Fig.%2%shows%resul*ng%densi*es%at%the%la*tude,%longitude,%and%height%of%CHAMP%(TIEGCM%values%have%been%interpolated).%

%%

!  DTM%performs%best%at%solar%min,%however%TIEGCM%also%agrees%well,%both%having%a%small%number%of%outliers.%

!  Fig.%3%shows%resul*ng%densi*es%at% the% la*tude,% longitude,%and%height%of%CHAMP.%

%%

%

!  Both%models% are% less% accurate% at% solar%max,% generally% underes*ma*ng%the%density.%TIEGCM%performs%best%overall.%

!  DTM% mirrors% some% increases/decreases% in% CHAMP% densi*es% well,%par*cularly%when%mul*ple%MI% and% XI% class% flares% occur% (not% necessarily%reflected%in%Kp%and%F10.7%values).%

!!

Assessing%the%performance%of%thermospheric%%modelling%with%data%assimila*on:%%

results%of%the%EU%FP7%ATMOP%project%%%

Sophie%A.%Murray1,%E.%M.%Henley1,%D.%R.%Jackson1,%S.%L.%Bruinsma2%%1Met%Office,%UK%%2CNES,%France%

©%Crown%copyright%%%%%%Met%Office%and%the%Met%Office%logo%are%registered%trademarks%

Contact!%

Email:%sophie.murray@metoffice.gov.uk%%Met%Office%FitzRoy%Road,%Exeter,%Devon,%EX1%3PB%United%Kingdom%Tel:%01392%885680%%%Fax:%01392%885681%

References!%

[1]!Henley,%E.,%et%al.,%2013,%ESWW%10,%S.%12.%[2]!Murray,%S.%A.,%et%al.,%2014,%Space%%% %%%%%%%%%%%%%%%%%%%%Weather,%in%prep.%[3]!Bruinsma,%S.,%et%al.,%2012,%JSWSC,%2:%A04.%!!

!!

[4]!Richmond,%A.%D.,%et%al.,%1992,%Geophys.%%%%%%%Res.%Le;.,%19:%601%I%604.%%[5]!Heelis,%R.%A.,%et%al.,%1982,%JGR,%87:%6339.%%[6]!Harris,%M.%J.,%2000,%PhD%Thesis,%UCL.%

%%

!!

Figure'1:% %a)%DTM%and%b)%TIEGCM%densiDes%on%

2009% March% 01% 00:00UT;% c)% CHAMP% densiDes%

between%00:00%UT%–%01:30%UT.%%

!  Neutral% density% observa*ons% inferred% from% CHAMP% accelerometer% (see%Fig.%1c).%CHAMP%orbiged%at%~400km%in%2003%and%~330km%in%2009.%

!  Results% from% the% two%models% using%DA%were% compared% for% two% 60Iday%periods;% solar% minimum% in% 2009% March% I% May,% and% maximum% in% 2003%March%–%May%(solar%equinox%periods).%

The% ATMOP% project% was% designed% to% provide% a% European% capability% for%nowcas*ng% and% forecas*ng% of% the% thermosphere.% As% part% of% this% project,%data% assimila*on% (DA)% procedures% have% been% developed% [1]% for% two%thermospheric%models%using%satellite%density%measurements%I%one%a%general%circula*on% model% (TIEGCM)% and% the% other% a% semiIempirical% model% (DTM).%Results% of% runs% using% DA% with% these% models% were% compared% with%observa*ons%at%solar%max%and%min%[2].%Both%models%show%similar%behaviour,%underes*ma*ng% densi*es% at% solar%max% and% overes*ma*ng% at% solar%min.% A%mean%improvement%of%~3.5%%was%found%using%hourly%DA%with%TIEGCM%over%a%60Iday% period.% Further% work% will% allow% nearIrealI*me% assimila*on% of%thermospheric%data%into%these%models%for%improved%forecas*ng.

!  Using%1Ihour%DA%with%TIEGCM%yields%a%mean%improvement%of%~3.5%%over%both%*me%periods%studied%(see%Table%1).%

!  Both%models%perform%well%at%solar%min.%Improvements%to%the%models%may%be%needed%to%reproduce%stormy%condi*ons%beger%at%solar%max%[2].%%

!  The% inclusion% of%more% satellite% data% in% the% TIEGCM%DA% (such% as%GRACE%and%GOCE)%may%improve%results,%as%well%as%Incremental%Analysis%Updates.%

Figure'2:%Upper% row:%OrbitRaveraged%CHAMP,% TIEGCM,%and%DTM%densiDes.%Upper%Middle:%Density%

difference%between%CHAMP%and%the%two%models.%Lower%Middle:%F10.7%and%Kp%values%used%as%inputs%to%

the%models.%Lower:%GOES%soY%XRray%flux.%

Figure'3:%Upper% row:%OrbitRaveraged%CHAMP,% TIEGCM,%and%DTM%densiDes.%Upper%Middle:%Density%

difference%between%CHAMP%and%the%two%models.%Lower%Middle:%F10.7%and%Kp%values%used%as%inputs%to%

the%models.%Lower:%GOES%soY%XRray%flux.%

ρ [x 10-12 kg m3]

Model%Run%Mean%%%Difference%

Solar%min%(2009)% Solar%max%(2003)%CMAT2% I45.8% 38.4%TIEGCM% I24.9% 29.1%TIEGCM%(DA)% I21.4% 25.3%DTM%2012% I18.9% 57.7%

Table' 1:% Mean% percentage% difference%

between% measured% CHAMP% densiDes% and%

resulDng%densiDes% from%various%model% runs.%

Note%that%results%from%TIEGCM%runs%without%

DA,% as% well% as% CMAT2% runs% [6],% were%

included% here% in% order% to% compare% models%

with%GCMs%that%do%not%include%DA.%

!  DTMI2012%[3]%:%!  F10.7% solar% and% Am% auroral%

indices% used% as% inputs;% DA% of%mul*Isatellite%observa*ons.%%

!  Resul*ng% parameter% at% a%specific% la*tude,% longitude,%and% al*tude% between% 200% I%1000km,% and% up% to% 1°%%resolu*on%(see%Fig.%1a).%

!  TIEGCM%[4]%:%!  F10.7% and% Kp% were% used% as%

inputs,% with% the% Heelis% ion%convec*on%pagern%[5];%hourly%DA% procedure% using% CHAMP%or%GRACE%data%[1].%%%

!  3D% model% atmosphere% ~90% I%500km;%5°%resolu*on%(Fig.%1b).%%