AeroCom marine intercomparison

Eimear Dunne

Finnish Meteorological Institute

First MAGIC Science Workshop

BNL, 6th May 2014

AeroCom marine intercomparison

Eimear Dunne

Finnish Meteorological Institute

First MAGIC Science Workshop

BNL, 6th May 2014

Outline• Marine CCN project

• AeroCom marine intercomparison• Which models? • What data?

• Polite request for any and all available marine data

Marine CCN project• Finnish Meteorological Institute project, funded by the

Academy of Finland• PI: Hannele Korhonen

Purpose: To improve our understanding of current and future sources of CCN in the marine atmosphere

• Primary model: GLOMAP (University of Leeds)

I will be giving a presentation on Thursday at 11am

AeroCom• “Aerosol Comparisons between Observations and

Models”• Aerosol modellers submit simulations from their

models with prescribed emissions etc. • Their performance is then compared against each

other and against observations• As part of Marine CCN, I am coordinating a miniature

AeroCom intercomparison focusing on marine regions

Sectional versus modal models• Sectional models can

capture the shape of the size distribution more accurately

• Modal models are much less computationally intensive

Models included in the comparison• GLOMAP-mode

• University of Leeds• Modal aerosol scheme in TOMCAT chemical transport model

• HadGEM• Hadley Centre / UK Met Office• GLOMAP-mode implemented in HadGEM climate model

• ECHAM-SALSA• University of Hamburg• Sectional aerosol scheme implemented in ECHAM climate model

• CAM-Oslo• Norwegian Meteorological Institute• Sectional aerosol scheme implemented in CAM atmosphere model

Challenges from global models• Large grid box size means that in-situ measurements

may be very different from the grid box average value in the model• This can be an especially difficult issue when a grid box

contains both continental and marine regions• Global models cannot resolve sub-grid-scale

processes and will use parameterisations to represent cloud-scale processes etc.• Some of these processes (like wet removal) are

extremely important to aerosol concentrations, but aren’t explicitly resolved

Challenges from AeroCom• Data provided to the AeroCom database are monthly

mean values for e.g. mode radius, number concentration etc. • Advantage: gets rid of a lot of noise• Disadvantage: if we’re looking at daily values of

shipboard measurements, and the ship moves between grid-boxes…

• Just got to do the best we can

What kind of data are we looking for?• Literally any marine-based aerosol measurements• The more remote, the more relevant to the project

• But we are still interested in coastal measurements! • Already have several offers of Arctic/Antarctic

measurements, so lower latitudes would be especially welcome

• Aircraft are great, too – as long as they’re over the ocean!

• We always use data within relevant data policy• Always interested in collaboration if you would like to

compare observations with models

MAGIC data• MAGIC is exactly what we’re looking for – long-term,

high-quality aerosol measurements in marine regions• We will try to fit the model investigation to whatever

data are made available• Because the models are global, we’ll be using a grid-

box average• The inclusion of statistics from long-term MAGIC

measurements will improve the comparison• Things we are particularly interested in:

• Size distributions• Compositions• AODs at different wavelengths

Data Please?Eimear.Dunne@fmi.fi

Discussion