Radiative forcing of fine ash and volcanic sulphate aerosol. sulphate aerosol after a very large Northern hemisphere mid-latitude eruption

Transcription

1 Radiative forcing of fine ash and volcanic sulphate aerosol after a very large Northern hemisphere mid-latitude eruption Ulrike Niemeier (1), Claudia Timmreck (1), Sebastian Rast (1), Marco Giorgetta (1), Hans-F Graf (2), Stephen Self (3) 1) Max Plack Institute for Meteorology, Bundesstr. 53, D Hamburg, Germany ( ulrike.niemeier@zmaw.de) 2) Centre Atmospheric Sciences, University Cambridge, Downing Place, Cambridge CB2 3EN, Unitgdomed Kingdom 3) Department of Earth Science, Open University, Milton Keynes IUGG, July 2007

2 Outline Introduction The Model Pinatubo Yellowstone Conclusions

3 Introduction History of simulation of volcanic eruptions at MPI-MET Interactive simulation of ash and sulfate processes necessary Volcano Module for ECHAM5 see also talk of C.Timmreck after coffee break

4 GCM ECHAM5 Global Circulation Model Spectral dynamical core Semi-implicit leapfrog time differencing Prognostic equations for vorticity, divergence, pressure and temperature Flux-form semi-lagrangian transport of passive tracers Micro-physical prognostic equations for water vapour, water, and ice SW radiation scheme; 4 spectral bands LW radiation scheme; 16 spectral bands

5 GCM ECHAM5 Adiabatic processes Winds Temperature Humidity Cloud species Diffusion Radiation Cumulus convection Stratiform precipitation Friction Sensible heat flux Evaporation Ground roughness Ground temperature Snow Ground humidity Model processes Model variables Snow melt

6 Aerosol Model HAM Aerosol micro physics 7 log-normal modes Aerosol mass and number are transported as tracers Contains: Sulfate, OC, BC, Dust, DMS, Sea Salt Composition of internally mixed mode modified by aerosol dynamics, themodynamical and cloud processes Stratospheric sulfate chemistry for volcano study

7 Ash Module Ash independent from HAM - own module Dry deposition Wet deposition Sedimentation SW-LW radiative effects One mode only HAM used for sulfate chemistry Extension of HAM toward the stratosphere

8 Interactive eruption in ECHAM5 Fine Ash and SO2 is injected into the Stratosphere at 50 and 30 hpa Only 5% of the total errupted ash Other parts coagulate in wet aggregates Mean Radius of fine ash: 10µm

9 Simulations Pinatubo eruption Ash - number and mass: 468 Mt at 50hPa for 3 hours SO2: 17 Mt at 30hPa for 3 hours Yellowstone Erruption 100 times Pinatubo Ash - number and mass: Mt at 50hPa for 10 days SO2: 1700 Mt at 30hPa for 10 days SO2 conversion follows parameterization after Bekki (1996)

10 Pinatubo: Fine Ash and SO2 at 50hPa

11 Pinatubo: Fine ash wetdeposition [kg/m2]

12 Pinatubo: Measurements Ash deposition [mm] (Wiesner et al, 2004)

13 Comparison with Satellite Data Ash [Mt] days ECHAM Satellite days Comparison of the global mass of fine ash in the size range 1µm to 15µm in ECHAM to retrieval results of Guo et al (2004) Ash [Mt]

14 ECHAM5/HAM T63 L31 and L47 Ash mass Monthly mean values one month after eruption: L31 left and L47 right at 50 hpa

15 Yellowstone Erruption eruption time: 1st of June for 10 days 100 times Pinatubo Ash - number and mass: Mt at 50hPa for 10 days SO2: 1700 Mt at 30hPa for 10 days SO2 conversion follows parameterization after Bekki (1996)

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17 Yellowstone: Ash [1.e-9 kg/kg]; monthly mean July August December

18 Yellowstone: Ash fall out [kg/m2] in the first month dry dep. wet dep. sedimentation

19 Yellowstone: SO2 [1.e-9 kg/kg]; monthly mean After Bekki (1996): OH is limited; SO2 lifetime prescribed; OH concentration set to zero in the stratosphere

20 Yellowstone: Sulfate [1.e-9 kg/kg]; monthly mean July August December

21 Yellowstone: SW heating rate [K/d] of Sulfate July August December

22 Yellowstone: Temperature responce [K] to LW effect of sulfate in June; monthly mean

23 Summary Summary We developed a interactive volcanic ash modul for ECHAM5/HAM Aerosol model HAM was extended to stratosphere including sulfate chemistry Comparison of Pinatubo eruption to measurement Showed first results of a super volcano eruption Radiative effect of ash and lw effect of sulfate still missing Effect on meteorological parameters not extremely strong Next steps Include coupling with LW and SW radiation Include gas phase chemistry, especially for calculation of the OH chemistry

24 Thank you