The Climate in a World without Ozone

Transcription

1 The Climate in a World without Ozone Frank Selten, Richard Bintanja, Dewi Le Bars, Hylke de Vries, Michiel van Weele (KNMI) Aarnout van Delden (Univ. Utrecht) QOS 2016, 5-9 September 2016, Edinburgh

2 Study Objectives and Approach Goals - to fully appreciate the role of ozone in the present-day climate system - To investigate the shortwave and longwave radiative effects of ozone in a coupled global climate model - Sanity check on the GCM response to a strong forcing (~ -13 W/m 2 ) - Educational / A narrative on the fundamental role of ozone Through: - Multi-year coupled GCM simulations with the ozone concentrations set to zero globally, at all altitudes, in calls to the radiation scheme - There is no direct relation to reality outside the climate model. Chemical effects nor changes in atmospheric mass taken into account

3 Climate simulations: model set up EC Earth V2.2 (Hazeleger et al., Clim. Dyn, 2012) - IFS cy31r1 atmosphere at resolution T159L62 - NEMO-2 ocean model (1 degree, L42) - LIM-2 sea-ice model - Transient simulations - Two 5-year 30-member ensembles - One member extended to 20 years - Additional simulations with EC-Earth V3.2: high-top T159L91 and with separate shortwave and longwave forcings (still under investigation)

4 EC Earth consortium SMHI, Sweden* KNMI, The Netherlands* DMI, Denmark* AEMET, Spain* Met Éireann, Ireland* CNR ISAC, Italy* Instituto de Meteorologia, Portugal* FMI, Finland* BSC, Spain Centro de Geofisica, University of Lisbon, Portugal ENEA, Italy Geophysical Institute, University of Bergen, Norway IC3, Spain ICHEC, Ireland ICTP, Italy IRV, Sweden Lund University, Sweden Meteorologiska Institutionen, Stockholm, Sweden Niels Bohr Institute, University of Copenhagen, Denmark NTNU, Norway SARA, The Netherlands Unité ASTR, Belgium Universiteit Utrecht, The Netherlands Universiteit Wageningen, The Netherlands University College Dublin, Ireland Vrije Universiteit Amsterdam, the Netherlands EC Earth brings together research institutes from 10 European countries to collaborate on the development of an Earth System Model. The goal is to build a fully Coupled Atmosphere Ocean Land - Biosphere model, that can be utilised in seasonal to decadal prediction and climate change projections. It builds on model technology from ECMWF and aims to implement the concept of seamless NWP/climate prediction

5 Top of atmosphere net radiative flux Surface temperature 1.5 K cooling Instantaneous -8 W/m 2 SW forcing restored to -1.5 W/m 2 within 5 years Ctrl No ozone

6 TOA radiation budget Net downward flux at TOA (no ozone ctrl) -1.5 W/m 2 Net shortwave flux W/m 2 (more upward scattered) Net longwave flux + 8 W/m 2 (reduced OLR)

7 Surface radiation budget Shortwave flux change at surface: + 5 W/m 2 (Less clouds +1 W/m 2 ) Longwave flux change at surface: -4 W/m 2 Net: +1 W/m 2 Despite surface radiative warming increased evaporation due to reduced atmospheric stability leads to 3.5K surface cooling in first year, which is restored to 1.5K after 5 years (and 0 K after 20 years)

8 Energy budget No ozone Atmospheric absorption 82.5 (= ) W/m 2 Atmospheric emission -188 (= ) W/m 2 Net radiative budget change -104 => Closed by enhanced LH, SH turbulent surface fluxes; Fast response of evaporation & precipitation reduced after 5 years

9 Slightly increased instability; no inversion Stronger and higher-reaching deep convection Atmospheric temperatures adjust within 2 years

10 Response of the jets Control No ozone

11 Response of the jets Low-top(20 hpa)/l62 High-top(0.01 hpa)/l91

12 Reversed temperature gradients Above 150 hpa reversed N-S gradient with absence of polar jets Jet maxima remain just poleward of PV=2 steep gradients Some asymmetry between the NH and SH remains

13 Increased mid-latitude storminess DJF standard deviation of daily 850 hpa geopotential height

14 Changing land/sea pattern of precipitation More precipitation (colder) on tropical land / less on (colder) tropical seas

15 Weaker planetary stationary waves in NH lead to Canadian warming, Siberian cooling

16 Summary for A World without Ozone Using a global climate model without ozone radiative effects the size of the impact of ozone on present-day physical climate has been calculated Some key features of our modeled climate without ozone include: The planet would cool by ~1.5 K through enhanced Rayleigh scattering The greenhouse effect would decrease reducing surface temperatures The stratospheric jets disappear; the tropospheric jets strengthen and extend upward in altitude The mid-latitude storm tracks intensify and convection reaches higher Global mean precipitation seems largely unaffected, though important changes occur in monsoon precipitation distribution over land and sea Understanding of all changes still requires some further study

17 Take home message Ozone is a radiative, dynamically and chemically active key climate component: Impacting the overall climate system through the radiation budget Controlling atmospheric composition through atmospheric chemistry Providing protection at the surface against energetic UV radiation Contributing to the natural greenhouse effect and to radiative forcing Lowering crop yields and causing health effects when breathing in Ozone is advised to be modeled interactively in a GCM, even without chemistry, because also less exaggerated ozone changes and variability as has been shown here, fundamentally impact through radiative effects atmospheric circulation, winds, convection and precipitation in a climate model.

18 Thank you

19 Annual means

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