1 / 18

Investigation of Brewer-Dobson circulation changes in a future climate

Investigation of Brewer-Dobson circulation changes in a future climate. Martin Dameris and Rudolf Deckert German Aerospace Center, Institute for Physics of the Atmosphere. Santorini, September 25, 2007. What do we know so far? (e.g. WMO, 2007).

lycoris-rhea
Download Presentation

Investigation of Brewer-Dobson circulation changes in a future climate

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Investigation of Brewer-Dobson circulation changes in a future climate Martin Dameris and Rudolf Deckert German Aerospace Center, Institute for Physics of the Atmosphere Santorini, September 25, 2007

  2. What do we know so far? (e.g. WMO, 2007) • CCMs consistently indicate that the recovery of total ozone will be accelerated in some regions if stratospheric temperatures will further decrease, except in polar regions. • There, a cooler stratosphere will lead to an increase in the amount of polar stratospheric clouds (PSCs). • The future evolution in tropical ozone may differ from that in the extra-tropics. • The future strengthening of the Brewer-Dobson circulation in CCMs (GCMs, climate models) seems to be affected by increased large-scale planetary wave activity in the atmosphere. • So far, causes and mechanisms which drive these dynamical changes are unclear and need more investigations...

  3. Scheme of a Climate-Chemistry Model (CCM)

  4. Past and future evolution of the ozone layer 60°S-60°N 25°S-25°N 35°N-60°N 35°S-60°N UNEP/WMO, 2007

  5. Impact of climate change on ozone recovery Definition of reference simulations representing a "best estimate" conditions (REF) and sensitivity simulations representing "no-climate-change" conditions (NCC). • REF: • Well-mixed greenhouse gas concentrations and sea surface temperatures are prescribed according to observations and predictions (A1B = 'business as usual'; IPCC, 2001). • NCC: • Well-mixed greenhouse gas concentrations and sea surface temperatures are fixed after a given date, e.g. 1980. • All other boundary conditions in REF and NCC are the same, especially the evolution of ODSs!

  6. ULAQ E39C WACCM REF NCC Impact of climate change on ozone recovery Mean annual temperature deviations 60°N - 60°S (20 km) ΔT (K) 1950 2050 Time (years) UNEP/WMO, 2007

  7. ULAQ E39C WACCM REF NCC Impact of climate change on ozone recovery Zonally averaged mean total ozone deviations 60°N - 60°S (%) 1950 2050 Time (years) UNEP/WMO, 2007

  8. Impact of climate change on ozone recovery E39C WACCM ΔT [K] FMA pressure [hPa] REF–NCC WACCM E39C ΔO3 [%] FMA pressure [hPa] Latitude (°) Latitude (°)

  9. Impact of climate change on ozone recovery E39C WACCM ΔT [K] FMA pressure [hPa] REF–NCC WACCM E39C ΔO3 [%] FMA pressure [hPa] Latitude (°) Latitude (°)

  10. Impact of climate change on B-D circulation (REF-NCC) 30-90°S, JJA 20°S-20°N, a.m. 30-90°N, DJF

  11. Impact of climate change on B-D circulation (REF-NCC) Change of planetary wave activity in July/August

  12. Impact of climate change on B-D circulation (REF-NCC) Change of planetary wave activity in December/January

  13. mainly due to changes in stationary wave activity Impact of climate change on B-D circulation (REF-NCC) Change of wave activity in July/August Change of wave activity in December/January summer winter winter summer

  14. Impact of climate change on B-D circulation (REF-NCC) Change of TEM in December/January Change of TEM in July/August

  15. Δ(SST)max≈ 1 K Impact of climate change on B-D circulation (REF-NCC) Change of SST in December/January Change of SST in July/August latitude longitude longitude

  16. Δ(convective precipitation)max ≈ 7 % Impact of climate change on B-D circulation (REF-NCC) Change of conv. prec. in December/January Change of conv. prec. in July/August

  17. Summary and hypothesis • Tropical SSTs in the summer hemispheres of REF are up to 1 K higher than in NCC simulations (prescribed!). • There, convective precipitation is enhanced (up to 7%). • This implies enhanced release of latent heat, which leads to an increased generation of (quasi-) stationary waves in the summer tropics (Garcia and Salby, 1987), and enhanced tropical upwelling (which is compensated at higher latitudes by a change of sub-tropical downwelling). • It is not clear if changes in the extra-tropical wave activity originates from stronger wave generation in mid latitudes (cause?) or from different background conditions.

  18. ? Questions ? • Could it be that higher subtropical SSTs in the summer hemisphere are responsible for an increase of quasi-stationary planetary waves activity in this region? • Boehm and Lee, 2003: "The processes responsible for tropical upwelling are not well understood." (Partly driven by extratropical 'wave drag', but not sufficient.) Hypothesis: Tropical upwelling is driven in response to momentum transport by Rossby waves that are generated by tropical convection. • Could these changes in tropical wave activity affect extra-tropical wave activity in wintertime? • Blackmon et al., 1987: Found some evidence that tropical latent heat release contributes to mid-latitude planetary wave activity.

More Related