© Crown copyright Met Office Impact of aerosols on South Asian Monsoon on short and medium-range timescales Jane Mulcahy Met Office, Exeter, UK

© Crown copyright Met Office

Impact of aerosols on South Asian Monsoon on short and medium-range timescalesJane Mulcahy

Met Office, Exeter, UK

[email protected]© Crown copyright Met Office

Introduction

• Seasonally high aerosol loading over India during pre-monsoon and monsoon seasons.

• Largely anthropogenic sources from IGP and China but also natural mineral dust aerosol during pre-monsoon and monsoon season

AOD climatology (2000-2008) from MISR, Dey and Di Girolamo (2011)


Potential impact on monsoonA number of different mechanisms have been proposed for the impact of aerosols on Asian Monsoon

Elevated Heat Pump hypothesis (Lau et al. 2006)

Solar Dimming Effect

(Ramanathan et al (2005))

Chung et al. (2005)


Aerosols in the UMAerosols are currently not treated 'seamlessly’ in the UM across all time and space scales.

Timescale

Resolution

Direct effect from monthly mean

CLASSIC aerosol climatologies-Cheap!

Fully interactive CLASSIC or

UKCA aerosol schemes


Aerosols & NWP Prediction The story so far…..

Improved aerosol-microphysics

Future

SAMBBA 2012Global dust forecasts: July 2011

Co

st

Old Aerosol Configuration

Current Operational Configuration

(Upgrade: July 2010)


Aims

• Can we improve the radiation budget in the model?

• What are the impacts on the predictive skill of the global NWP model?

• What are the impacts on the hydrological cycle and circulation patterns?

• What level of aerosol complexity is required across the different timescales?

SAPRISE:

Investigate the aerosol impacts on the Asian summer monsoon circulation, variability and the hydrological cycle from days (NWP) to sub-seasonal timescales.

By including a more realistic distribution of aerosols in global NWP models can we address the following questions:

[email protected]

SAPRISE Work Plan

1. Run a set of high resolution global NWP experiments covering a number of monsoon seasons, including a set of 15 day forecasts (n320L70):

• with and without prognostic aerosols

• with and without the direct and indirect aerosol effects

• Initialized aerosol experiments using MACC aerosol analysis

http://www.gmes-atmosphere.eu/d/services/gac/nrt/nrt_opticaldepth

• Sensitivity studies focussing on particular aerosol species, e.g. black carbon,dust and sulphate.

2. Conduct some coupled sub-seasonal runs (1 month) to investigate the impact of SST forcing on the aerosol forcing of the monsoon. (n96ORCA1.0).

Monsoon seasons: 2009 (“dry”); 2007 (“wet”); 2012

Evaluation of aerosol and model predictions against a range of observations.


Initial findings from MACC Short-range global NWP simulations for June-July 2009


Global NWP simulations with prognostic aerosol

Set of global 5 day NWP simulations for June-July 2009 with different aerosol configurations.

Resolution: N320L70 (~40km).

Aerosol scheme: CLASSIC (Bellouin et al. 2011), AeroCom-2 2005 emissions.

List of Experiments

CNTRL:

CLIM:

AER_Dir:

AER_Dir_InDir:

INIT_Dir:

INIT_Dir_InDir:

“Historical” aerosol climatology.

New climatologies derived from CLASSIC

Full CLASSIC aerosol, Direct Effect Only

Full CLASSIC aerosol, Direct & Indirect Effects Included

Initialised CLASSIC aerosol, Direct Effect Only

Initialised CLASSIC aerosol, Direct & Indirect Effects Included

Source: Monsoon On Line, http://www.tropmet.res.in

Trial Period


2009 monsoon season

Analysis period

[email protected]

Aerosol optical depth D+5440nm 21st June – 20th July 2009


CLASSIC InitialisedCLASSIC

Aerosol Climatologies

MODIS


Aerosol speciationDust is key contributing species to the westSulphate becomes more dominant further east


Impact on 850hPa winds D+5

Direct Effect

InitialisedDirect Effect

All figures show Expt - Cntrl

InitialisedDirect & Indirect Effect

Direct & Indirect Effect

CNTRL: Simplistic 2D aerosol representation (Cusack et al. 1998)


Impact on total precipitation

D+5

AER_Dir_InDir-CNTRLAER_Dir-CNTRL

INIT_Dir-CNTRL INIT_Dir_InDir-CNTRL

TRMM data (mm/day) CNTRL-TRMM


Inclusion of Indirect Aerosol Effect

More realistic values of cloud droplet number concentration results in a significant reduction in low level cloud in remote “clean air” regions and leads to significant warming of TOA +surface.

Impact on Net TOA Radiation T+120

Net Surface Radiation T+120Improvement in SW downward fluxes found at NSA-Alaska ARM site

CDNC

Next GA release will incorporate the indirect aerosol effects from the aerosol climatology.


15-day Case Studies


Global verification of 15 day forecasts

Z500 NHPMSL NH

T850 Tropics

T850 NH

Mean Error:

RMSE:

Mean Error:

RMSE:

W850 TropicsPMSL Tropics


Aerosol optical depth440nm d+10

Aerosol Climatology CLASSIC DirectCLASSIC

Direct+Indirect

AER_Dir - CLIM AER_Dir_InDir - CLIM

1.5m Temperature

Aerosol Climatology, D+10

Impact of CLASSIC Direct Effect Only

Impact of CLIMw/Indirect Effects

Impact of CLASSIC Direct + Indirect


Precipitation

Aerosol Climatology


Impact of Clim w/Indirect Effects


D+5

D+10

D+15


850hPa Winds

D+5

D+10

D+15

Error Aerosol Climatology



Impact of Clim w/Indirect Effects

© Crown copyright Met Office [email protected]

Conclusions so far

• Evaluated the impacts of an improved aerosol representation in high resolution global NWP model from short to medium-range timescales.

• In general, AOD is reduced over South Asia when prognostic CLASSIC aerosol scheme is used instead of climatologies and is underestimating aerosol loading in IGP.

• Strong sensitivity to 2nd indirect aerosol effect enhances convergence over southeast Asia and the low level monsoon flow increasing positive wet bias in this region.

• On medium range timescales global verification metrics suggest some benefits of including prognostic schemes in particular the indirect effects on NH and Tropical model skill.

• Impacts on monsoon are similar to short-range with some enhanced impact in response to SW surface warming in direct only aerosol effect experiments.

• Indirect effect of climatologies has a smaller impact on precipitation and low level monsoon flow than fully interactive prognostic equivalent.

© Crown copyright Met Office [email protected]

Future work

• Initialized aerosol experiments using MACC aerosol analysis

• Sensitivity to particular aerosol species, e.g. black carbon,dust and sulphate.

• Absorption sensitivity runs.

• Emission sensitivity for carbonaceous aerosols (Streets et al. 2003; Carmichael, Uni. Of Utah)

• Additional cases? Run possibly for a different monsoon season.

• Conduct some coupled sub-seasonal runs (n96ORCA1.0).


Thank you


CLASSICAerosol scheme implemented in HadGEM2-ES

Advection and Deposition schemes

>20 Prognostic Tracers

Full interaction with model’s

radiation scheme – direct and

indirect effects

Climatological Oxidants

AeroCom-2 Hindcast

Emissions based on 2005

Ref: Bellouin et al. (2011)* diagnostic; ** climatology

Source: Monsoon On Line, http://www.tropmet.res.in

Trial Period© Crown copyright Met Office

2009 monsoon season

Analysis period

Case Studies

© Crown copyright Met Office© Crown copyright Met Office

Impact on standard verification metrics

T+120 Temperature (K) T+120 Height (m) T+120 RH(%)

Short-range:

(Full trial June-July 2009)

Direct & Indirect simulations improve biases in NH temperature and height profiles.

Temperature 850hPaRMSE

Height 500hPaRMSE

PMSLRMSE

Medium-range: (Set of 12 15-day case studies from above trial.)

Reduced RMS errors when direct & indirect aerosol effects are included.

© Crown copyright Met Office© Crown copyright Met Office

Met Office Unified Model™Atmospheric model components

• Regular lat/lon grid.

• Non-hydrostatic, semi-Lagrangian.

• Atmospheric tracer advection

• Parameterization of physical processes

• Aerosols: CLASSIC or UKCA

• ≈ 0.35°× 0.23° ≈ 25km

• 70 levels (80km top)

• Initialised via hybrid Ensemble/4D-Var

Operational model •≈ 0.56°× 0.38° ≈ 40km

•70 levels (80km top)

•Initialised via 4D-Var

Used in this study

Documents

© Crown copyright Met Office Impact of aerosols on South Asian Monsoon on short and medium-range timescales Jane Mulcahy Met Office, Exeter, UK