Atmospheric transport and chemistry lecture I Introduction II

Atmospheric transport and chemistry lecture I. Introduction II. Fundamental concepts in atmospheric dynamics: Brewer-Dobson circulation and waves III. Radiative transfer, heating and vertical transport IV. Stratospheric ozone chemistry V. The tropical tropopause VI. Climate gases VII. Solar variability 1 The sun 2 Solar radiation changes, climate & ozone 3 Solar particles and the middle atmosphere VII/

Solar irradiance provides energy to the earth system SW heating LW cooling UV/Vis/NIR Thermal IR Turco 1997 VII/2

Solar irradiance at TOA: near UV/Vis/IR 05 -MAR-2004 H Ca II Skupin et al. , 2005 Weber et al. , 1998, Weber 1999 VII/3

Mg. II h and k emission Fraunhofer lines: wing: absorption originating in the photosphere (T~6000 K) core: emission, originating in the chromophere/transition region Rottmann et al. , 2005 VII/4

Mg II index chromospheric activity index from GOME UV solar activity proxy from core-to-wing ratio of Mg II line èinsensitive to optical degradation èlinearly correlates well with UV and EUV wavelength variations down to 30 nm (Viereck et al. 2001) VII/5

Solar UV irradiance variability u Mg II index is a suitable proxy for modelling solar UV and EUV variability (Viereck et al. 2001) VII/6 u suitable proxy for modelling UV irradiance in climate models and for TSI reconstruction (Fröhlich et al. 2004)

Origin of solar irradiance variability Solar UV/vis radiation originates èupper photosphere èchromosphere ètransition region variations in received solar UV irradiance are caused by the emergence and decay of active regions as they transit the solar disk. Active regions contain enhanced: èUV brightness (photospheric faculae and chromspheric plages) èlocalized enhanced magnetic fields VII/7 Fox, 2004

origin of solar irradiance variability H continuum image (white light) VII/8 H line center emission

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The solar activity cycle Magnetic flux X-rays Minimum The short-wave radiation varies strongly through the activity cycle: from a factor 2 in the UV (<100 nm) up to a factor 100 in X-rays. The magnetic flux at the solar surface also varies quasi-periodically over the 11 -year solar cycle. Maximum VII/10 Maximum

solar irradiance variability Largest variations in UV Small variation in visible and NIR (not well known) Lean, 1994 VII/11

UV variation from solar minimum (1996) to maximum (1992) UARS/SOLSTICE (Rottmann, 2000 VII/12 UV variation below 400 nm linearly correlates with Mg. II index (280 nm)

Total solar irradiance from space („solar constant“) 0. 1% PMOD TSI CGD, NCAR VII/13 Froehlich, priv. comm.

„solar constant“ TSI composite time series from satellite observations VII/14 Froehlich, priv. communication

Modelled TSI contribution UV (<400 nm) contributes 8% to TSI ≈60% of TSI variability comes from the UV (<400 nm) Lean et al. (1997) estimated abt. 30% contribution from 200 -400 nm varibility to that of TSI (from SOLSTICE observations) ≈8% 50 nm Krivova et al. et 2006 Krivova al. 2006 VII/15 100 nm 500 nm

Contribution to TSI variability Lean et al. , 1997 VII/16

Solar indices Various solar indices show variation with the 11 year solar cycle and 27 d solar rotation (full disc) 122 nm èUV brightening competing with sunspot darkening (VIS) Mg index starts in 1978 F 10. 8 since the early 1900 s Sunspots counts since 1700 s VII/17

Correlation among indices Sunspot Area Total Irradiance VII/18 10. 7 cm Radio Flux GOES X-Ray Flares Geomagnetic aa index Climax Cosmic-Ray Flux

Penetration depth of solar radiation in the atmosphere Liou, 2002 VII/19 Thuillier et al. , 2004

Solar influence on climate Climate impact from periodic earth events solar influence some evidence for surface T response to solar variability on time scales longer than the 11 y cycle (before 1980) VII/20

Milankovich cycles: changes in earth orbit parameters obliquity ~41 ky Changes in earth parameters excentricity precession VII/21 ~100 ky ~19 and 24 ky èChange in solar insolation

Milankovich cycles: climate impact ice volume derivative solar insulation anomaly Wallace & Hobbs 2005 VII/22

Global warming & cooling VII/ Lohmann, priv. communication

Sunspot numbers Solar variability and climate: recent past VII/24 Maunder mínimum Dalton mínimum TSI about 0. 25% lower than current values during Maunder minimum

Total ozone trends: mid- to high NH latitudes recent trends solar wave driving BD circulation aerosol ESC Dhomse et al. (2006) VII/25 u. Increase in NH total ozone since mid nineties èincrease in BD circulation strength èrise of solar cycle 23 èreturn to stratospheric aerosol background conditions after Pinatubo eruption

Global ozone trends and solar cycle variability WMO 2006, Chapter 3 VII/26

Global ozone trends and solar cycle variability Models do not show the double peak (25 and 50 km altitude) èPossible reasons m Data record too short (~2. 5 solar cycles) m NOx from particle (electron precipitation) leads to ozone destruction during solar minimum in middle stratosphere -> BUT: equires „huge“ amounts of Nox m Reduced ozone production (less sunlight) in middle stratosphere from enhanced ozone in the upper stratosphere m Interference from QBO and other dynamical effects m Lower stratospheric solar signature are probbaly from dynamical response to solar variability WMO 2006, Chapter 3 VII/27

Δ UV Δ Absorption of solar UV-radiation Δ CP Δ NOx / HOx chemistry Ozone Temperature Dynamics Coupling between solar variability and atmospheric dynamics VII/

Solar coupling & planetary waves & polar O 3 loss extra solar heating during solar max strengthens subtropical stratopause jet (SJ) in early winter èradiative response Strengthening of westerlies (SJ) means reduced wave progation and reduced BD circulation /warming of tropical tropopause region in early einter èdynamical response Deflection of planetary waves away from subtropics (towards pole) while SJ descends downwards and polewards leading to a waekening weakening of polar night jet (polar vortex) in mid- to late winter warmer polar stratospheric temperatures with reduced polar ozone loss in late winter èchemical response Kodera and Kuroda (2002) VII/29

U and T response to solar cycle T u Change in zonal mean wind (u) in m/s and zonal mean temperature (T) in K for a cahnge of 100 sfu (F 10. 8 units) From solar minimum to maximum ~120 sfu VII/30

Solar coupling and QBO extra solar heating during solar max strengthens subtropical stratopause jet (SJ) in early winter èradiative response Strengthening of westerlies (SJ) means reduced wave progation and reduced BD circulation /warming of tropical tropopause region in early einter èdynamical response Deflection of planetary waves away from subtropics (towards pole) while SJ descends downwards and polewards leading to a waekening weakening of polar night jet (polar vortex) in mid- to late winter Update from Labitzke, 1987, and Labitzke and van Loon, 1988 mostly during QBO west phase VII/31 warmer polar stratospheric temperatures with reduced polar ozone loss in late winter èchemical response

The Quasi-Biennial Oscillation (QBO) Baldwin et al. , 2001 QBO phase defined by zonal mean wind speed (u) in the lower tropical stratosphere (define QBO phase) Downward descent of alternating easterly and westerlies VII/32 Red: westerlies Blue: easterlies

QBO: coupling to the extratropics Wind speed differences between QBO east and QBO west phase (40 h. Pa) èBlue: wind speed difference ( u) negative (more easterly) èRed: wind speed difference ( u) positive (more westerly) Holton-Tan mechanism relates mid-latitude planetary wave propagation to QBO èimpacting the mean meridonal circulation Holton-Tan mechanism (1980) VII/33 Baldwin, et. al. , 2001