Air Quality Prediction

Louisa EmmonsAtmospheric Chemistry Observations and 

Modeling (ACOM) LaboratoryNational Center for Atmospheric Research

CESM Workshop, June 2017

Prediction of air pollution hazards

Air pollution hazards:• Consist of ozone, oxidants, toxics, and fine and ultrafine particles

from anthropogenic emissions intensified by heat waves and stagnation events, as well as extreme events such as wildfires, gas leaks, …

• Threat to human health and food security

Exposure to air pollution: • 100,000 premature mortalities

per year in U.S.• Crop damage > $1B per year

Difficult to predict in locations of rapid change, such as:• Areas of increasing

urbanization / megacities• The Arctic• Regions where strict

emissions controls have been implemented

CESM Workshop, June 2017

Cross-scale prediction of atmospheric chemistry and air pollution hazards

• Coordinated research is needed to attain accurate near-term prediction of AQ on local-to-global scales for effective responses to air pollution hazards that threaten human and ecosystem health

• Observations on local, regional and global scales, will be integrated into a global model with regional refinement using data assimilation

• Advances in the representation of fine-scale chemical processing and large-scale, longer-term Earth-system prediction are incorporated

George Washington Bridge, NY, 1970s London, Jan 2017Los Angeles, 1948 & today

CESM Workshop, June 2017

Framework for cross-scale air quality prediction

Global-to-local scale Earth System Model

ProcessesEmissions – Chemistry – Transport

Cross-scale observations

Analyses, Forecasts, OSSEs

Community user applications

(e.g., operational forecasts)

Assimilation

Error analysisModel deficiencies

New observations& Field campaigns

CESM Workshop, June 2017

Data Assimilation

Gaubert et al., JGR, 2016

• Assimilation of MOPITT CO in CAM-chem for 2002

• Increases CO, particularly in the NH

• Resulting OH decrease• Implies increase in primary

CO emissions necessary, as well as increase in emissions of VOCs that oxidize to CO

• Also captures decreasing trend in CO emissions; impacts OH and CH4trends

Control Assim. Control-Assim

CO

OH

129Tg 197Tg

162Tg195Tg

Primary CO

SecondaryCO

CESM Workshop, June 2017

Real-time emissions for AQ prediction

Model

Near-real-time fire counts, traffic, O&G extraction can update emissions

Special events needing rapid response:• Growing urban areas, gas leaks, volcanic

eruptions, wildfiresOn-going activities with real-time adjustment• Vehicle emissions based on actual trafficRapidly changing regions• Inverse modeling for emissions estimates are

laggingAircraft observations can measure fluxes and

evaluate inventories on a regional scale Denver from NCAR C-130

Real-time emissionsActivity data

CESM Workshop, June 2017

Transport Model Resolved scale transportVertical mixing / PBL transportConvective transport

Physics Model RadiationCloud Physics

Land & Surface Models

Community Chemistry ModelPhotolysis and Kinetic

Chemical Reactions

• Cloud and Aerosol Optical Properties

• Wet Deposition of Trace Gases and Aerosols

• Lightning Flash Rate

• Transported Trace Gases and Aerosols

• Convective Wet Deposition of Trace Gases and Aerosols and Lightning Flash Rate

• Emissions of dust, sea salt, trace gases from vegetation (and ocean)

• Dry Deposition

Chemistry Model within an Earth System Model

CESM Workshop, June 2017

Vision

Improve S2S and Climate Forecast

Skill

Improve Representation of Chemistry in

ESMs

Impactful Atmospheric Composition

Prediction

Advances in AQ, S2S and climate forecasting capability will be beneficial to many sectors in society

A new unified chemistry model allows for:• Better rep. of aerosol and

radiative forcing of climate• Improved S2S AQ and

weather forecast skill

Essential we engage users to identify the most useful AQ forecast products