Geodäsche Woche 0 Nürberg, 7. 9. Sepember 0 O he compuao of mass-chage reds from GRACE gravy feld me-seres Olver Baur Isu für Welraumforschug, Öserrechsche Aademe der Wsseschafe
Movao Greelad lear mass-chage reds (jus a few examples... Velcoga ad Wahr (GRL, 005 Ramlle e al. (GPC, 006 Averagg 04/00 07/004 CSR erel 07/00 03/005 Averagg CNES/GRGS erel Che e al. (Scece, 006 Luhce e al. (Scece, 006 07/003 07/005 Mascos KBRR 04/00 /005 Forward CSR modelg Wouers e al. (GRL, 008 Baur e al. (JGR, 009 Velcoga (GRL, 009 Che e al. (JGR, 0 0/003 0/008 Forward CSR, modelg GFZ Leaage 08/00 07/008 CSR, quafcao GFZ, JPL 04/00 0/009 Averagg CSR erel 04/00 /009 Forward CSR modelg -50-00 -50-00 -50-300 G/yr Sources of dscrepacy mpac geoceer of GIA geoceer moo sgal from moo SLR Iverso mehod / pre-processg Perod of vesgao Daa used Daa mapulao (c 0, degree-
Movao Greelad mass-chage accelerao (aga, jus a few examples... Velcoga ad Wahr (Naure, 006 04/00 04/004: -95 ± 50 G/yr 05/004 04/006: -34 ± 6 G/yr Che e al. (JGR, 0 04/00 03/005: -44 ± 5 G/yr 04/005 /009: -48 ± 43 G/yr Velcoga (GRL, 009 Schrama e al. (JGR, 0 Rgo e al. (GRL, 0-5 -0-5 -30-35 -40 G/yr Sources of dscrepacy Iverso mehod / pre-processg Perod of vesgao Daa used Daa mapulao (c 0, degree- Compuao of mass-chage reds 3
Coe Lear red modelg No-lear red modelg Model seleco Coclusos Greelad Iverso mehod: Baur e al. (JGR, 009 Perod of vesgao: 05/00 04/0 (ad subses hereof Daa used: CSR (RL04 Daa mapulao : c 0 : SLR, geoceer moo: SLR, GIA: Paulso e al. (007 Compuao of mass-chage reds: varable Amazo bas 4
Lear red modelg Model fuco Tred, approxmaed by frs-order polyomal (regresso le y ( 0,,..., Addoal aual sgal y ( A cos( f B s( f 0,,..., F chage rae (G/yr Regresso le -3 ± 5 + aual sgal -3 ± 4 + sem-aual sgal -3 ± 3 + S dal alas -3 ± 3 + K dal alas -30 ± 3 + K dal alas -30 ± 3 5
Lear red modelg Model fuco Tred, approxmaed by frs-order polyomal (regresso le y ( 0,,..., Addoal aual ad sem-aual sgal ad dal alases y ( cos( s(,,..., ; 0 A f B f j j j j j j,... F chage rae (G/yr Regresso le -3 ± 5 + aual sgal -3 ± 4 + sem-aual sgal -3 ± 3 + S dal alas -3 ± 3 + K dal alas -30 ± 3 + K dal alas -30 ± 3 6
Lear red modelg Model fuco Tred, approxmaed by frs-order polyomal (regresso le y ( 0,,..., Addoal aual ad sem-aual sgal ad dal alases y ( cos( s(,,..., ; 0 A f B f j j j j j j,... F chage rae (G/yr Regresso le -3 ± 5 + aual sgal -3 ± 4 + sem-aual sgal -3 ± 3 + S dal alas -3 ± 3 K + K dal alas -30 ± 3 + K dal alas -30 ± 3 K S 7
Lear red modelg Smoohg of me seres Tred, approxmaed by frs-order polyomal (regresso le Addoal aual ad sem-aual sgal ad dal alases Ier-aual varaos 3-moh wdow Lowess fler low-pass fler lowess 0.5-33 ± G/yr lowess 0. -33 ± G/yr Velcoga (GRL, 009 8
Lear red modelg F chage rae (G/yr Regresso le 50 ± 8 + aual sgal 43 ± 6 + sem-aual sgal 43 ± 6 + S dal alas 43 ± 6 + K dal alas 36 ± 7 + K dal alas 36 ± 7 lowess 0.5 0. 39 4 ± 3 G/yr K K S 9
Lear red modelg Mass-chage accelerao Che e al. (JGR, 0 04/00 03/005: -9 ± 38 G/yr 04/00 03/005: -44 ± 5 G/yr 04/005 /009: -48 ± 43 G/yr Re-compuao - ± 4 G/yr -70 ± 3 G/yr -50 ± 8 G/yr 0
Lear red modelg Mass-chage accelerao Che e al. (JGR, 0 04/00 03/005: -44 ± 5 G/yr 04/005 /009: -48 ± 43 G/yr Velcoga ad Wahr (Naure, 006 04/00 04/004: -95 ± 50 G/yr 05/004 04/006: -34 ± 6 G/yr Velcoga (GRL, 009 04/00??/003: -37 G/yr??/007 0/009: -86 G/yr Choce of accelerao po?
Lear red modelg Subse perod: 5 years Subse shf: 6 mohs Subse perod: 6 years Subse shf: 6 mohs
3,... ;,...,,, (... ( 0 f y j j p p Tred approxmao by p-h order polyomal (regresso polyomal Regresso le Regresso parabola No-lear red modelg Model fuco
4 Tred approxmao by p-h order polyomal (regresso polyomal Regresso le Regresso parabola No-lear red modelg Model fuco,... ;,...,,, (... ( 0 f y j j p p
Model seleco Whch model s relable / o be preferred?? 5
6 (, / 0 ~ / ˆ, 0 :, 0 : p T H H Hypoheses esg of polyomal coeffces (absolue measure Iformao crera (relave measure Leave-oe-ou cross valdao (relave measure CV ˆ CV ( y y Whch model s relable / o be preferred? l( ˆ l( BIC ( AIC AIC, ˆ ˆ, ˆ l( AIC R ( R ( ˆ R c p e - p - - y y σ - R-square Aae IC Bayesa IC Model seleco
Model seleco Whch model s relable / o be preferred? Greelad Order ΔR ΔAIC c ΔBIC ΔCV Sgfca parameers 0.00 0.7 8. 69 all 0 0 0 0 all 3 0. 3.6 5945 ercep 4 0 3.4 8. 8865 ercep Secod-order polyomal s superor o oher red fucos accelerao: -5 ± 3 G/yr Amazo bas Order ΔR ΔAIC c ΔBIC ΔCV Sgfca parameers 0.043 0 0 0 all 0 0.7 3.3 373 oe Frs-order polyomal s superor o oher red fucos 7
Coclusos I bref I s a mess! More scefcally Treds umbers (ad her error bouds are hghly subjec o he uderlyg processg scheme Ierpreao of mass-chage reds ad mass-chage red varaos over shor perods should be avoded Never ever valdae chage raes agas reds umbers based o dfferg perods Tred model seleco should rouely be accompaed by hypoheses esg ad formao crera evaluao The compuao of mass varao from GRACE has bee becomg creasgly heerogeeous; coveos would mprove cossecy 8
Tred model Whch model s relable / o be preferred? CSR Nle bas ITG DMT 9
Tred model Subse perod: 5 years Subse shf: 6 mohs Subse perod: 6 years Subse shf: 6 mohs 0