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Dynamical responses to volcanic forcings in climate model simulations DynVar workshop 22.04.13 Matthew Toohey with Kirstin Krger, Claudia Timmreck, Hauke Schmidt Slide 2 What would happen if a large volcanic eruption occurred tomorrow? Every seasonal to decadal climate forecast made prior to the eruption would become obsolete. Motivation Thompson et al. (2012) Thompson et al. (2009) Slide 3 Motivation Slide 4 Winter Warming Robock and Mao (1992) Slide 5 Post-volcanic dynamical anomalies Baldwin and Dunkerton. 2001 Christiansen, 2008 13 eruptions Schmidt et al., 2013 Slide 6 Stratospheric mechanism Stenchikov et al. (2002) Slide 7 Dynamical response to volcanic forcing = anomalous dynamics in 1 st (and sometimes 2 nd ) Northern Hemisphere winter after a major lower latitude volcanic eruption, characterized by: Positive NAO (NAM) at surface Strong stratospheric vortex westerlies Negative anomalies of polar cap lower stratosphere geopotential height Definitions Slide 8 A number of studies have reported realistic simulation of post-volcanic NH dynamical anomalies (Graf et al., 1993, 1994; Mao and Robock, 1998; Kirchner et al., 1999; Shindell et al., 2001; Rozanov et al., 2002; Stenchikov et al., 2002; Collins, 2004; Shindell et al., 2003, Shindell et al. 2004) But multi-model studies (e.g. CMIP, CCMVal-2) have not produced a convincing picture of model behavior. Model results Slide 9 CCMVal-2 post-eruption T anomalies Ch. 8 in SPARC, CCMVal Report, 2010 Slide 10 CMIP5 9 eruptions n=18 9 eruptions 13 models 72 members 9 eruptions 13 models 72 members 4 eruptions n=8 Driscoll et al. 2012 Sea level Pressure 50 hPa Geopotential height Slide 11 CMIP5 Charlton-Perez et al., 2013 Low-top High-top ERA-interim CMIP5 Slide 12 Stratospheric mechanism Stenchikov et al. (2002) ? ? Slide 13 Why dont CMIP5 models show strong NH winter vortices (i.e., negative polar cap z50 anomalies) after volcanic eruptions? Either 1.Response is not real (just chance?) 2.Models are flawed 3.Implementation of volcanic aerosol forcing is flawed 4.Volcanic aerosol forcing is flawed The question Slide 14 CMIP volcanic forcings 0.4 0.3 0.2 0.1 0 Sato et al. (1990)/GISS/Stenchikov Ammann (2003)/(2007) Pinatubo and El Chichon based on SAGE observations Recently updated with OSIRIS observations Oct 2001 - present Best estimate sulfur mass injection, distributed via parameterized stratospheric transport model Jan 92Jul 91Jan 92Jan 91Jan 92Jul 91Jan 92Jan 91 Slide 15 Notes: zonal mean, monthly mean, for pre-satellite era eruptions, spatial distribution of aerosols poorly constrained CMIP Volcanic forcings Sato et al. (1990)/GISS/Stenchikov Slide 16 Part 1: Use MAECHAM5-HAM, a coupled aerosol-climate model, to simulate the evolution of stratospheric sulfate aerosol after a Pinatubo-like eruption. Part 2: Use MPI-ESM, a high-top CMIP5 model, and replace the prescribed Pinatubo volcanic forcing from historical simulations with forcing sets built from Part 1. Experiment Slide 17 MPI-ESM: full Earth System model, with atmosphere, ocean, carbon cycle, vegetation components. Atmospheric component ECHAM6. low resolution (LR, T63/L47), configuration used here (no QBO). Volcanic aerosols are prescribed CMIP5 historical simulations use Stenchikov et al. (1998) forcing data set -> monthly mean, zonal mean aerosol extinction, single scattering albedo, and asymmetry factor MPI-ESM Slide 18 ECHAM: GCM developed at MPI-M, Hamburg Middle atmosphere version: 39 vertical levels up to 0.01 hPa (~80 km) T42 horizontal resolution Climatological sea surface temperatures, no QBO, no chemistry HAM: Aerosol microphysical module Modified for simulation of stratospheric volcanic aerosols Models aerosol growth, radiative effects, eventual removal MAECHAM5-HAM Inject SO 2 at 24 km Aerosol growth Radiative effects Aerosol transport via atmospheric circulation Transport to troposphere, rainout! HAM ECHAM5 SO 2 H 2 SO 4 Slide 19 Toohey et al (2011, ACP) MAECHAM5-HAM Pinatubo simulations Simulations of 17 Tg eruption, June 15, 15.3N Excellent agreement with ERBE TOA SW flux anomalies observed after Pinatubo eruption. Little to no dependence on eruption longitude. Slide 20 Modeled aerosol transport months after eruption Toohey et al. (2011) Slide 21 HAM July eruption simulations: DJF1 TemperatureGeopotential heightZonal wind n=12 Slide 22 DJF1 z50 anomalies n=12 July eruptions April, July and October eruptions n=36 Slide 23 AOD: July eruption ensemble variability Slide 24 Weak and Strong vortex composite AOD n=12 July eruptions Slide 25 Vortex strength ~ AOD gradient? Polar cap gph anomaly calculated as area mean over 70-90N. AOD gradient at 60N as AOD(60-90N) AOD(50-60N) Slide 26 Vortex strength ~ AOD gradient? Strong Vortex AOD gradient across vortex Aerosol heating gradient? If we want our prescribed aerosols to force a strong vortex, the forcing had better take the form of a strong vortex. Slide 27 MPI-ESM Pinatubo forcing experiment Stenchikov (CMIP5) HAM weak HAM strong r1,r2,r3 r4,r5,r6 r7,r8,r9 Slide 28 Aerosol extinction at 550 nm Stenchikov HAM weak HAM strong Slide 29 MPI-ESM: tropical 50 hPa T Slide 30 MPI-ESM: DJF1 T and u anomalies StenchikovHAM weakHAM strong Temperature (K) u wind (m/s) Slide 31 MPI-ESM: DJF1 z50 anomalies Low-top High-top ERA-interim Slide 32 MPI-ESM: DJF1 z50 anomalies Low-top High-top ERA-interim Slide 33 MPI-ESM: DJF1&2 z50 anomalies Low-top High-top ERA-interim CMIP5 Slide 34 Aerosol extinction at 550 nm Stenchikov HAM weak HAM strong Slide 35 Arfeuille et al. ACPD 2013 Extinction at 550 nm August Slide 36 CCMI: Surface Area Densities (SADs), stratospheric heating rates, and radiative properties, based on SAGE_4 retrievals (Tom Peter and Beiping Luo, ETHZ) Volcanic forcing, the next generation Model-based aerosol reconstructions becoming available for pre-satellite era eruptions. Tambora: Arfeuille et al. (2013) vs. Crowley (2008) Slide 37 For a CMIP5 historical-style simulation of Pinatubo, we can control the strength of the (ensemble mean) post- eruption NH winter vortex with the aerosol forcing set Vortex strength ~ AOD gradient across vortex edge Likely that dynamical response to volcanic eruptions can be improved by using different forcing data sets. Future work will show whether new volcanic forcing sets lead to better dynamical responses in climate models. Conclusions Slide 38 Volcanic vs. Anthropogenic forcing