Analyzing the effects of Brewer-Dobson circulation upwelling and horizontal transport on the TTL composition

Transcription

1 Analyzing the effects of Brewer-Dobson circulation upwelling and horizontal transport on the TTL composition Felix Ploeger F. Ploeger, P. Konopka, R. Müller, S. Fueglistaler, T. Schmidt, J. Manners, J.-U. Grooß, G. Günther, P. Forster, M. Riese (2012), J. Geophys. Res., 117, D09303 SPARC BD workshop, Grindelwald, 26 June 2012

2 Motivation UTLS composition impacts radiation & temperature! T-anomaly in [K] contribution due to O 3 tropics: 30% T ann. ampl. linked to O 3 [Fueglistaler, 2011] which processes drive seasonal trace gas variations in TTL?

3 Annual cycles in TTL for various species (e.g., H 2 O, O 3, CO) Mixing ratio: t χ = S(t) θ(t) θ χ v(t) y χ + D source sink upwelling in mixing eddy diff. seasonality due to: θ (BD-circulation, convection) v (horizontal in-mixing from extratropics) S (sources & sinks) seasonality linked to vert. transport O 3 : in-mixing impact [Konopka,2009] [e.g., Randel,2007; Schoeberl,2006; Folkins,2006]

4 Annual cycles in TTL for various species (e.g., H 2 O, O 3, CO) Mixing ratio: t χ = S(t) θ(t) θ χ v(t) y χ + D source sink upwelling in mixing eddy diff. Goals seasonality & Outline: due to: θ (BD-circulation, convection) v (horizontal in-mixing from extratropics) Disentangle in mixing & BD-upwelling effects on TTL seasonality S (sources & sinks) 1 In-mixing & BD-upwelling effect on H 2 O, O 3, CO 2 Characteristics seasonality linked to ofvert. in-mixing transport O 3 : in-mixing impact [Konopka,2009] 3 Sensitivities [e.g., Randel,2007; Schoeberl,2006; Folkins,2006]

5 Method 1: 3D backtrajectories reconstruct H 2 O: freeze-drying O 3 : photochem. production CO: chemical loss

6 Method 1: 3D backtrajectories reconstruct H 2 O: freeze-drying O 3 : photochem. production CO: chemical loss Separation of pathways: in mixing: eq.lat.> 50 & θ > 350 K tropical (BD-upwelling): rest TTL mixing ratio: χ TTL = f trop χ trop + f NH χ NH + f SH χ SH

7 Seasonality of tropical and in mixed mixing ratios (χ s)

8 Seasonality of tropical and in mixed mixing ratios (χ s)

9 Seasonality of tropical and in mixed mixing ratios (χ s) Seasonality due to: O 3 : tropics + in mixing

10 Seasonality of tropical and in mixed mixing ratios (χ s) Seasonality due to: O 3 : tropics + in mixing CO: tropics + in mixing

11 Seasonality of tropical and in mixed mixing ratios (χ s) Seasonality due to: O 3 : tropics + in mixing CO: tropics + in mixing H 2 O: tropical transport

12 Seasonality of tropical and in mixed mixing ratios (χ s) Seasonality due to: O 3 : tropics + in mixing CO: tropics + in mixing H 2 O: tropical transport TTL seasonality: Tropical view not sufficient in mixing important!

13 Origin of TTL O 3 ann. cycle (@400K) a) In-mixed air fraction (f s): in-mixed air ann. cycle NH/SH inversely phased ERA-Int agrees with obs. estimate [Volk,1996] b) Contributions to TTL O 3 : χ TTL = f trop χ trop +f NH χ NH +f SH χ SH 50% summer O 3 in-mixed (ann. amplit. main forcing!)

14 Origin of TTL O 3 ann. cycle (@400K) Fraction of in-mixed air 20%, O 3 50%: = in-mixing impact depends on species meridional gradient! a) In-mixed air fraction (f s): in-mixed air ann. cycle NH/SH inversely phased ERA-Int agrees with obs. estimate [Volk,1996] b) Contributions to TTL O 3 : χ TTL = f trop χ trop +f NH χ NH +f SH χ SH 50% summer O 3 in-mixed (ann. amplit. main forcing!)

15 What drives in-mixing? PV & hor. 370 K (NH summer) 50 -crossing PDF (summer) djf

16 What drives in-mixing? PV & hor. 370 K (NH summer) 50 -crossing PDF (summer) In mixing caused by: monsoon circulations! ( strong seasonality) djf

17 In-mixing & sensitivities: vert. velocity Vert. velocity θ in TTL (rad. calculation ERA-Interim)

18 In-mixing & sensitivities: vert. velocity Vert. velocity θ in TTL (rad. calculation ERA-Interim) Rad. calculation ERA-Interim: TTL upwelling in ERA-Interim 40% too fast!

19 1D tropical tracer model 1D tropics with in mixing rates α (entrainment) sum [Volk,1996] t χ = θ(t) θ χ α n (t)(χ χ n ) α s (t)(χ χ s ) + P Lχ θ from ERA-Interim (corrected), in-mixing from 3D trajectories

20 1D tropical tracer model 1D tropics with in mixing rates α (entrainment) sum [Volk,1996] t χ = θ(t) θ χ α n (t)(χ χ n ) α s (t)(χ χ s ) + P Lχ θ from ERA-Interim (corrected), in-mixing from 3D trajectories Sensitivity TTL composition to upwelling & in-mixing: vary annual mean & amplitude of upwelling & in-mixing!

21 Sensitivity O 3 & CO profiles to ann. mean upwelling θ increased θ = weaker O 3 gradient (less production) = weaker CO gradient (less loss) best fit for 0.6 θ ERA = ERA-Interim θ 40% too fast!

22 Sensitivity of O 3 annual cycle to upwelling/in-mixing:

23 Sensitivity of O 3 annual cycle to upwelling/in-mixing:

24 Sensitivity of O 3 annual cycle to upwelling/in-mixing:

25 Sensitivity of O 3 annual cycle to upwelling/in-mixing: no-inmix

26 Sensitivity of O 3 annual cycle to upwelling/in-mixing: no-inmix O 3 control: upwelling & in-mixing amplitudes!

27 Sensitivity of CO annual cycle to upwelling/in-mixing: CO control: Brewer-Dobson upwelling!

28 In-mixed O 3 fraction throughout realistic vert. velocity range: (NH summer) very weak dependence on upwelling ( 37% O 3 in-mixed) ann. amplitude fraction linked to in-mixing 70%

29 In-mixed O 3 fraction throughout realistic vert. velocity range: (NH summer) How much O 3 in-mixed? min. in-mixing very weakcase dependence (ERA 20%): on upwelling ( 37% O 3 in-mixed) 30% ann. Oamplitude 3 mixing ratio fraction linked to in-mixing 70% 65% O 3 ann. anomaly

30 Sensitivity of in-mixed O 3 to vert. velocity? Mean tropical ascent along 1D trajectory θ(t): Eqn. dχ dθ = γχ + αχ m + P θ P...chem. production; α...in-mixing rate; χ m...mid-latitude value; γ = L + α, L...chem. loss

31 Sensitivity of in-mixed O 3 to vert. velocity? Mean tropical ascent along 1D trajectory θ(t): Eqn. dχ dθ = γχ + αχ m + P θ P...chem. production; α...in-mixing rate; χ m...mid-latitude value; γ = L + α, L...chem. loss χ(θ) = θ θ 0 ( αχm + P θ ) G(θ,θ )dθ +χ 0 G(θ,θ 0 ), G(θ,θ ) = e θ θ γ dθ production & in-mixing along trajectory + upward propagation of boundary χ 0

32 Sensitivity of in-mixed O 3 to vert. velocity? Mean tropical ascent along 1D trajectory θ(t): Eqn. dχ dθ = γχ + αχ m + P θ P...chem. production; α...in-mixing rate; χ m...mid-latitude value; γ = L + α, L...chem. loss θ ( ) αχm + P χ(θ) = G(θ,θ θ 0 θ )dθ +χ 0 G(θ,θ 0 ), G(θ,θ ) = e θ θ γ dθ production Contribution & of in-mixing in-mixing: along trajectory relative to photochem. production + upward (= αχ m /P) propagation independent of boundary of θ! χ 0 30% O 3 in-mixed independent of θ

33 Conclusions: in-mixing important for TTL seasonality (merid. gradient!) annual cycle of in-mixing (summer: 20%, monsoons!) impact on composition O 3 : large (summer: 30-50%, anomaly control 65%) CO: weak H 2 O: vanishing ERA-Interim upwelling 40% too fast in-mixed O 3 fraction independent of BD-upwelling velocity if seasonal O 3 variations amplify trop. temperature cycle link between in-mixing and trop. temperatures!

34 Appendix Appendix

35 What if no in-mixing??? o3-seas no in-mixing: vary θ a need extremely large θ a θ 65% mean O 3 too low! Appendix

36 What if no in-mixing??? o3-seas no in-mixing: vary θ a need extremely large θ a θ 65% mean O 3 too low! at least some in-mixing needed!!! Appendix

37 Fraction of in-mixed air (a) and of in-mixed O 3 (b) in-mixing occurs in TTL ( K) upward propagation of in-mixed air impact on O 3 largest in TTL ( K) (no upward propagation) Appendix

38 What drives in-mixing? PV & hor. 370 K (NH winter) 50 -crossing PDF (winter) jja Appendix