SCALE ISSUES IN MODELING INTERCONTINENTAL SCALE ISSUES IN MODELING INTERCONTINENTAL TRANSPORTTRANSPORT

Daniel J. Jacob, Rokjin Park, Lin Zhang, Colette L. Healdwith support from NASA, EPA, EPRI

Issue 4 of Background Document: “What is the effect of spatial resolution of the model on estimates of source-receptor relationships? Is it necessary to nest regional models within global models, and what difficulties must be overcome to perform this nesting? Is one way nesting sufficient, or is two-way nesting necessary?”

INTERCONTINENTAL TRASPORT AS WEDDING INTERCONTINENTAL TRASPORT AS WEDDING OF GLOBAL AND REGIONAL MODEL CULTURESOF GLOBAL AND REGIONAL MODEL CULTURES

GLOBAL MODELS REGIONALMODELS

regional statistics and events

local events

synoptic(~100 km, days)

global(~1000 km, months)

meso(~10 km, hours)

global budgets and distributions

fine variabilityconvectionscavenging

strat-trop exchange

boundary conditionssurface stratification

BL dynamicstopography

Priorities

Scales

Scaling nightmares

NEED TO SHAREOUR

NIGHTMARES

TRANSPACIFIC TRANSPORT OF OZONE AND AEROSOLSTRANSPACIFIC TRANSPORT OF OZONE AND AEROSOLS

entrainment

ASIA PACIFIC NORTH AMERICA

NOx, SO2, VOC

warm conveyor

belts,convection

aerosols,HNO3

PAN

VOCs (long-lived)

OCaerosol PAN

O3

NOxO3

SulfateOC aerosol

Boundary layer

Free troposphere2 km

subsidence

ozone, sulfate, OC

HEMISPHERIC POLLUTION

plumetransport

SURFACE DATA FOR OZONE AT REMOTE SITESSURFACE DATA FOR OZONE AT REMOTE SITESSUGGEST LITTLE VARIANCE IN INTERCONTINENTAL INFLUENCESUGGEST LITTLE VARIANCE IN INTERCONTINENTAL INFLUENCE

CASTNet observations (13-17 LT)GEOS-Chem model Standard Background Natural Stratospheric

*

Intercontinentalpollution

Regionalpollution}

}+X

Voyageurs NP, Minnesota, 2001

Intercontinental ozone enhancement of 5-10 ppbv, driven by large-scale subsidence

Fiore et al. [2003]

SURFACE OZONE AT TRINIDAD HEAD, CALIFORNIA, SURFACE OZONE AT TRINIDAD HEAD, CALIFORNIA, Apr-May 2002Apr-May 2002

Observations: 41 ± 5 ppb (filtered against local influence)GEOS-Chem model: 39 ± 5 ppb (Asian 4.5 ± 1.1 ppb)MOZART model: 37 ± 9 ppb (Asian 4.2 ± 1.3 ppb)

Synoptic variability is weak in both model and observations, but local nighttime depletion (stratification) is not resolved in global models

Goldstein et al. [2004]

WHY ARE INTERCONTINENTAL OZONE POLLUTION PLUMESWHY ARE INTERCONTINENTAL OZONE POLLUTION PLUMESOBSERVED IN FREE TROPOSPHERE BUT NOT AT SURFACE?OBSERVED IN FREE TROPOSPHERE BUT NOT AT SURFACE?

Aircraft observations during NOAA/ITCT-2K2 out of Monterey (April-May 2002)

COO3

Hudman et al. [2004]

Asian pollution plume at 2-4 km

May 17

This is consistent with aircraft vs. surface observations of transpacific dust plumes, which show 10x dilution between lower free troposphere and surface – but can models reproduce this? (they can’t resolve the free tropospheric plumes)

INTERCONTINENTAL OZONE POLLUTION ASSESSMENTSINTERCONTINENTAL OZONE POLLUTION ASSESSMENTSMUST ACCOUNT FOR LOCAL TITRATION/STRATIFICATIONMUST ACCOUNT FOR LOCAL TITRATION/STRATIFICATION

CASTNet sitesGEOS-Chem ModelOzone background

*

Ozo

ne

(pp

bv

)

Cumulative Probability

Ozone background is depleted under stagnant/stratified/titrated conditions…but global models cannot deal properly with this

Addressing this issue requires downscaling, e.g., global regional nesting

Fiore et al.[2003]

1-WAY NESTING OF GEOS-Chem AND CMAQ: 1-WAY NESTING OF GEOS-Chem AND CMAQ: PRELIMINARY RESULTSPRELIMINARY RESULTS

CMAQ (GEOS-Chem boundary conditions) GEOS-Chem

CMAQ and GEOS-Chem have comparable surface ozone over continents butCMAQ is lower across Pacific and transpacific pollution influence is half that in GEOS-Chem

April 2001 surface ozone

Rokjin Park (Harvard) and Carey Jang (EPA/OAQPS)

CMAQ domain stretched from Asia to the North Atlantic

CMAQ vs. GEOS-Chem TRANSPACIFIC TRANSPORTCMAQ vs. GEOS-Chem TRANSPACIFIC TRANSPORT

ASIA N. AMERICA

Ozone concentrations at 25-50oN vs. pressure and longitude (April 2001)

CMAQ

GEOS-Chem

Low free tropospheric ozone in CMAQ likely due to processes usually neglectedin regional models: STE, lightning, …

Ozone, ppbv

Evaluation w/ mean TRACE-P obs in Asian outflow (<140E)

TRACE-PCMAQGEOS-Chem

Rokjin Park (Harvard) and Carey Jang (EPA/OAQPS)

Ozo

ne

(pp

bv)

TESR=0.64Slope=0.62

GEOS-ChemModelR=0.84

Slope=0.50

USING SPACE-BASED TES OZONE-CO DATA TO OBSERVE INTERCONTINENTAL OZONE POLLUTION

Lin Zhang (Harvard)

Ozone-CO relationshipdownwind of Asia

CO

ppbv

ppbv

Carbon monoxide (pppbv)

Ozone

602 hPa TES observations, July 2005

Ozo

ne

(pp

bv)

TESR=0.38Slope=0.75

GEOS-ChemmodelR=0.79

Slope=0.67

USING SPACE-BASED TES OZONE-CO DATA TO OBSERVE INTERCONTINENTAL OZONE POLLUTION

Lin Zhang (Harvard)

Ozone-CO relationshipdownwind of eastern N. America

CO

ppbv

ppbv

Carbon monoxide (pppbv)

Ozone

618 hPa TES observations, July 2005

TRANSPACIFIC ASIAN AEROSOL POLLUTION TRANSPACIFIC ASIAN AEROSOL POLLUTION AS SEEN BY MODISAS SEEN BY MODIS

X1018 [molecules cm-2]

Heald et al. [2006]

Quantitative comparison to models must use MODIS reflectances (not AODs)

CMAQ vs. GEOS-Chem TRANSPACIFIC CMAQ vs. GEOS-Chem TRANSPACIFIC TRANSPORT OF SULFATE (April 2001)TRANSPORT OF SULFATE (April 2001)

SulfateIn surfaceair

Column

CMAQ GEOS-Chem

Asian pollution influence in U.S. surface air in CMAQ is 5x that in GEOS-Chem Rokjin Park (Harvard) and Carey Jang (EPA/OAQPS)

EVALUATING ASIAN SULFATE OUTFLOW:EVALUATING ASIAN SULFATE OUTFLOW:

Concentration, g m-3

Alt

itu

de,

km

Sulfate SOx

TRACE-P aircraft observations (Mar-Apr 2001, <140oE)

Rokjin Park (Harvard) and Carey Jang (EPA/OAQPS)

Suggests insufficient scavenging in CMAQ during venting to free troposphere

TESTING TRANSPACIFIC SULFATE IN GEOS-ChemTESTING TRANSPACIFIC SULFATE IN GEOS-ChemWITH SURFACE OBSERVATIONS IN NORTHWEST U.S.WITH SURFACE OBSERVATIONS IN NORTHWEST U.S.

Mean Asian pollution enhancement in NW U.S. in spring: 0.16 ± 0.08 g m-3

Heald et al. [2006]

Observed sulfateObserved dust

Model sulfate Model Asian sulfateModel Asian dust

Northwest U.S. IMPROVE sites (2001)

CONCLUSIONS AND RECOMMENDATIONSCONCLUSIONS AND RECOMMENDATIONS

• Global models have capability to describe intercontinental transport on synoptic scales (100-1000 km)

• For policy applications, need coupling with regional models to downscale the information to meso and local scales (1-10 km)– focus regional models on synoptic-to-meso downscaling– 2-way nesting of course nice but 1-way nesting should be OK

• Apply regional models to improve simulation of continental venting– requires new thinking in regional models– could be exploited in 2-way nesting

• Improve simulation of free tropospheric pollution plumes in global models– this may be tied to convective parameterizations, model resolution,

advection algorithms• Need to investigate model ability to describe subsidence and boundary layer

entrainment