3D Brewer Dobson circulation derived from satellite measurements

Transcription

1 SPARC BDC Workshop Grindelwald, Tuesday, June 26, 202 3D Brewer Dobson circulation derived from satellite measurements Axel Gabriel, Deniz Demirhan Bari,2, Heiner Körnich 3, Dieter H.W. Peters Leibniz-Institute for Atmospheric Physics at the University Rostock, Kühlungsborn, Germany 2 Istanbul Technical University, Department of Meteorological Engineering 3 Department of Meteorology, Stockholm University, Stockholm, Sweden

2 Outline. Introduction 2. 3D Eulerian and idual mean winds in the stratosphere and mesosphere and their effects on stationary wave patterns in H 2 O and O 3 (Odin, Aura) 3. Summary

3 . Introduction: Stratospheric ozone and planetary wave fluxes Pacific versus Atlantic O 3 * and (F ϕ,f z ) averaged over the Pacific half of hemisphere Zonally asymmetric ozone O 3 *=O 3 [O 3 ] at 0 hpa, January 990s, ERA-40 O 3 * and (F ϕ,f z ) averaged over the Atlantic half of hemisphere 3D wave flux vectors (Plumb;985) (vectors are scaled by (F ϕ,f z ) (p/p 0 ) -/2 (F ϕ,00*f z )) below 50hPa primarily zonal wave numbers k 4

4 .2 Introduction: 3D idual circulation Earlier works: Hoskins et al. (983), Trenberth (986), Plumb (986) 3D TEM approach focused on wavemean flow interaction Recently: Kinoshita et al. (JMSJ, 200) 3D TEM approach used for a case study of ozone transport in the SH u = u e Rd u T ( ) z H N² + S ( ) y f Transformed momentum equations: d u dt f v = φ x + F u v = v e Rd ( z H v T ) N² S ( ) x f d v dt + f u = φ y + F v f y S f w = w e + Rd ( y H v T ) N² + Rd u T ( ) x H N² Introduce a balance equation for the rotational component (Trenberth, 986): S = Rd ( u ² + v ² T ²/N² ) / 2 H Divergent component of the idual flow: f v d F u ( is time mean, the wave energy perturbation S contributes to the Stokes drift Kinoshita et al., 200) + f u d F v f y S f An alternative: Callaghan and Salby (JAS, 2002) 3D diabatic circulation in isentropic coordinates show zonal asymmetries in the downwelling and a cross-polar flow in the northern middle stratosphere

5 2. Temperature, geopotential and winds, Northern Winter, 60 N (Odin & ERA-Interim) Temperatu of Odin (50-90km) and ERA Interim (0-50km) 0-year means on a 0 x0 lon-lat grid. ( A. Gabriel, H. Körnich, S. Lossow, D.H.W. Peters, J. Urban, and D. Murtagh, ACP, 20.) T* L H Φ* ERA Interim Odin v g * w b * Temperature geopoential height geostrophic winds quasi-geostrophically balanced vertical wind T Φ=φ/g, φ z = RT/H (u g,v g ) = f - (-φ y, φ x ) w b * ( [u g ]θ* x + v g *[θ] y + [v g *θ*] y ) / θ 0z

6 2.2 Effect of Eulerian time mean transport on H 2 O*, Northern Winter, 60 N (Odin) Water vapour of Odin (489Ghz: 20-75km, 557GHz: 50-00km) 0-year means on a 0 x0 lon-lat grid. Balanced transport of μ*=μ-[μ]: dμ*/dt = S*+G*+D μ * [u g ] μ*/ x = S* + G* g G* = - v* [μ]/ y - w* [μ]/ z S* = P* - L*[μ] - [L]μ* H 2 O*= H 2 O [H 2 O] derived from Odin Wave one pattern with a jump in phase at upper stratosphere Fourier decomposition for zonal wave numbers k: linear solution μ*(tr) Linear source term S*(T*): P=k3[CH 4 ] [OH], L=k4[O D] k3= k3 0 exp(-t3/t) k4= k4 0 not important, because H 2 O is inert up to 80km Wave one pattern in H 2 O* due to Eulerian mean winds Additional processes: - eddy time mean flow and eddy mixing - zonal asymmetries in methane (CH 4 )

7 2.3 Effect of Eulerian time mean transport on O 3 *, Northern Winter, 60 N (Odin) Ozone of Odin (544Ghz: 20-75km) 0-year means on a 0 x0 lon-lat grid. Balanced transport of μ*=μ-[μ]: dμ*/dt = S*+G*+D μ * [u g ] μ*/ x = S* + G* g G* = - v* [μ]/ y - w* [μ]/ z S* = P* - L*[μ] - [L]μ* Fourier decomposition for zonal wave numbers k: O 3 *=O 3 [O 3 ] derived from Odin Wave one pattern with a pronounced double-peak structure during winter linear solution μ*(tr) S*=0 S* [L]μ*+L*[μ] Linear source term S*(T*): L = k[o 3 P]+0.5 k2[no] k = k 0 exp(-t/t) k2 = k2 0 exp(-t2/t) significant influence in the upper stratosphere Wave one pattern in O 3 * due to Eulerian mean winds without and with S* Additional processes: - eddy time mean flow and eddy mixing. - zonal asymmetries in catalytic ozone destruction

8 2.4 Monthly mean eddy heat fluxes at 60 N, January (Aura) Irregularly spaced profiles of Aura/MLS (provided by NASA) daily means on a 0 x0 lon-lat grid monthly mean eddy heat and momentum fluxes based on deviations of daily mean from monthly mean. u' T' v' T' u' T' v' T' R S = (u'u' + v'v' H d T' T')/2 H L s s Pronounced zonal asymmetries in zonal and meridional eddy heat fluxes in stratosphere and mesosphere S is significant at stratopause altitudes (note scaling in the plot: S S (H S /L S ). H S =0km, L S =00km)

9 2.5 Wave forcing at 60 N, January (Aura) Left panel: f v d F u The wave fluxes produce northward / southward idual winds v (grey shaded: zonal wind u) Right panels: + f u d F v f y S f The wave fluxes produce eastward / westward idual winds u (grey shaded: meridional wind v)

10 2.6 Eulerian and idual circulation at 60 N, January (Aura) Zonally asymmetric components of Eulerian wind vector (u e [u e ], w e [w e ]) Difference between the idual and Eulerian wind vector (u u e, w w e ) ( Isolines: H 2 O in ppm; zonal winds in m/s; vertical winds in mm/s; note: w* is stronger than [w] by a factor of 0 ) The Eulerian and eddy time mean flow are partly counteracting (similar as in the zonal mean approach)

11 2.7 Residual circulation and O 3 * - Pacific versus Atlantic, Jan (Aura) latitude O 3 * and (v,w ) averaged over the Pacific half of hemisphere (90E 90W) latitude O 3 * and (v,w ) averaged over the Atlantic half of hemisphere (90W 90E) Lower / middle stratosphere: stronger transport of O 3 towards polar latitudes Upper stratosphere: up- and southward transport Upper / middle stratosphere: Down- and poleward transport of O 3 towards the center of the polar vortex Lower stratosphere: southward transport towards mid-latitudes

12 2.8 Zonal asymmetries in the eddy mixing at 60 N, January (Aura) 3D TEM tracer transport equation: μ/ t + v μ = P -Lμ + ρ - M, where ρ - M repents the eddy mixing Contribution of zonally asymmetric idual eddy mixing to the tendency of H 2 O Contribution of zonally asymmetric idual eddy mixing to the tendency of O 3 Residual eddy mixing contributes significantly to the configuration of the wave one patterns in H 2 O and O 3

13 2.9 Effect of idual time mean transport on H 2 O* and O 3 * (Aura) Observed fields derived from Aura H 2 O* O 3 * Wave one pattern due to idual mean winds and eddy mixing The wave one pattern are better reproduced, in particular the double-peak structure in O 3 * Non-balanced flow components might lead to further improvements of amplitude and structure of H 2 O* and O 3 *

14 2.0 Optimized daily wind fields based on day-to-day variations of H 2 O(Aura) Iterative adjustment of the day-to-day variations of an initial vector v b to the daily varying distributions of H 2 O: () Include a correction to the balanced wind: μ/ t + (v b +v c ) μ = S+D, (v c =v +v 2 ++v i for i iterations) (2) Neglect day-to-day variations of chemical source terms S and diffusion D ( S/ t 0, D/ t 0; update planned) (v i μ) t = ²μ/ t² t ( ((v b +v i- ) μ) t (v μ) t0 ) := ε i at time step t and iteration step i, where ε i 0 (3) Decompose ε i in vector components assuming mean values between maximum change and previous step: (μu i )/ x = 0.5*( (ε i (μv i- )/ y (μω i- )/ p + (μu i- )/ x) ) u i } ω i / p = u i / x v i / y ω i (μv i )/ y = 0.5*( (ε i (μu i- )/ x (μω i- )/ p) + (μv i- )/ y) ) v i (4) Convergence: v ci+ -v ci << v b +v ci ((v ci+ -v ci ) μ) t )/((v b +v ci ) μ) t ) (ε ci+ -ε ci )/ε ci ( <<% for i 30 ) Balanced vertical wind, Aura, 07 Jan 2007 Optimized vertical wind, Aura, 07 Jan 2007 Balanced vertical wind, ERA-Interim, 07 Jan 2007 Total vertical wind, ERA-Interim, 07 Jan 2007 The adjustment procedure provides improved daily mean wind fields for the stratosphere and mesosphere Upper stratospheric winds of ERA-Interim are uncertain because vertical planetary wave propagation is limited

15 2. Effect of optimized idual time mean transport on H 2 O*, 60 N, Jan 2007 (Aura) Observed fields derived from Aura, Jan 2007 Wave one pattern due to idual mean winds and eddy mixing (linear transport approach) The non-balanced flow and eddy mixing play an important role in reproducing the wave one pattern in H 2 O*

16 3. Summary. 3D idual winds derived from satellite data suggest pronounced zonal asymmetries in the 3D BDC and associated eddy mixing processes 2. Pacific Atlantic / European bimodality in the wave forcing and the wave-driven 3D BDC ponsible for the stationary wave patterns in O 3 and H 2 O( important for stratosphere-troposphere coupling) 3. Plans for the future: investigation of long-term changes in the 3D BDC, the 3D wave driving and stationary waves in tracer distributions ( local trends could be much larger than zonal mean trends) 4. Some updates are needed: high-order balanced equation, ω-equation, improved inversion procedure, validation of the stratospheric and mesospheric wind fields with local wind measurements