Evaluation of Satellite NO2 Columns over U. S. Power Plants using a Regional Atmospheric

Chemistry Model

Si-Wan Kim

ESRL, NOAA and CIRES, U. of Colorado

Acknowledgements

SCIAMACHY Data: A. Heckel, A. Richter, and J. Burrows at Univ. of Bremen

OMI Data: J. Gleason at NASA

Emission Inventory and WRF-Chem model:

G. Frost, S. McKeen, E.-Y. Hsie, M. Trainer, G. Grell and S. Peckham at ESRL, NOAA and CIRES, U. of Colorado

Sep 10-12, 2007, Workshop at KNMI

1. Background 2. WRF-Chem model 3. Satellite instruments and retrievals4. NO2 columns over power plants5. Conclusions 6. Future Plans

Outline

Uncertainties in NOx emission inventory (“bottom-up emission”)

Evaluation of estimated NOx emissions with satellite observed NO2 columns

NOx emissions NO2 columns (Martin et al., 2003, Beirle et al., 2003, Richter et al., 2005, van

der A, 2006, Kim et al., 2006… ) For power plants, known NOx emissions

(CEMS) --> Accurate model NO2 columns --> Evaluation of satellite NO2 observations

1. Background

Western US Eastern US

BackgroundWhy Western U.S. ?

SCIAMACHY OMI

BackgroundObservation of NO2 Columns by Satellites

BackgroundIdentification of Sources (Power Plants)

North Valmy

Intermountain

Hunter /Huntington

Mohave

Navajo Four Corners/San Juan

Cholla/Coronado/ Springerville

Bonanza

Craig/Hayden

Jim Bridger/Naughton

Dave Johnston/Laramie River

Colstrip

Reid Gardener

BackgroundIdentification of Sources (Power Plants)

North Valmy

Intermountain

Hunter /Huntington

Mohave

Navajo Four Corners/San Juan

Cholla/Coronado/ Springerville

Bonanza

Craig/Hayden

Jim Bridger/Naughton

Dave Johnston/Laramie River

Colstrip

Reid Gardener

Weather Research and Forecasting – Chemistry model (www.wrf-model.org/WG11)

Simulate chemistry and aerosol online within WRF model Option to simulate coupling among chemistry, aerosol,

radiation and clouds. Various chemical mechanisms (kpp available) and aerosol

modules

Various physical packages: PBL, Microphysics, Radiation and Convective parameterizations

2. WRF-Chem Model

Period: 2005 Summer

Initial & Boundary Condition: NCEP GFS & Idealized chemical soundings

Emissions : NEI99 updated following CEMS 2005

PBL: YSU Microphysics: WSM5 Radiation: Dudhia shortwave Cumulus parameterization: Grell & Devenyi Land-Surface: Noah

Chemical mechanisms: RADM2, RACM, RACM-ESRL Aerosol: MADE-SORGAM

Advection scheme: Original & Positive Definite

WRF-Chem ModelSetup

WRF-Chem ModelDifference due to Chemical Mechanism

WRF-Chem Model

Four Corners & San Juan Power Plants

Difference due to Advection Scheme

• SCIAMACHY (ENVISAT) Period: March 2002 ~ Resolution: 60 x 30 km2

Global coverage at the equator: 6 days (due to alternate limb nadir viewing

Time: 10:30 LT

• OMI (EOS-Aura) Period: November 2004 ~ Nadir View Resolution: 13 x 24 km2 (nominal), 13 x 8 km2 (zoom-in) Global coverage: 1 day Time: 1:30 LT

• Sampling Clear Sky (Pixels with Cloud fraction < 0.15) For OMI, 10 < swath mode number < 50 are used.

3. Satellite instruments

Satellites

Subtraction of stratospheric NO2

Vertical sensitivity (AMF, Air Mass Factor) A priori NO2 profile Aerosols Terrain Height Albedo (Reflectivity)

Retrieval Issues: Tropospheric NO2 columns

Satellites

A priori NO2 profile SCIAMACHY MOZART NO2 profile SCIAMACHY WRF-Chem NO2 profile

Retrieval Issues (prof1)

Satellites

A priori NO2 profile

Retrieval Issues (prof2)

AMF-WRFprof

AMF-MOZprof

SatellitesSatellites

Aerosols

Retrieval Issues (aero1)

SatellitesSatellites

Aerosols

Retrieval Issues (aero2)

AMF-NoAerosol

AMF-EdgarAerosol

Satellites Retrieval Issues (terrain)

4. NO2 columns over power plants

SCIA

Mohave

Intermountain

Navajo

Four Corners/ San Juan

* Summer of 2005

WRF

OMI

WRF

Jim Bridger/ Naughton

Four Corners (SCIAMACHY)

Power plant emissions

* 14 day running mean

Model chemistry ~7%Model advection ~8%Satellite a priori profile ~6%Satellite aerosol ~3%

Four Corners (OMI)

Power plant emissions

Model Chemistry ~2%Model Advection ~11%

Jim Bridger & NaughtonPower plant emissions

IntermountainPower plant emissions

MohavePower plant emissions

NavajoPower plant emissions

Name of Plant

(size of box: lon. x lat. )

Satellite NO2 columns or Difference (WRF - Satellite) (1015 molec. cm-2)

SCIA1 WRF - SCIA1 SCIA2 WRF - SCIA2 OMI WRF - OMI

Four Corner/San Juan (2 x1)

Jim Bridg./Naught. (2.75 x 2)

Intermountain (1.5 x 1)

Mohave (1 x 0.788)

Navajo (1.5 x 0.625)

2.77

1.38

1.32

2.35

1.82

0.71 ( 25%)

0.04 ( 3%)

0.70 ( 53%)

1.41 ( 60%) 1.61 ( 89%)

2.59

1.10

1.14

2.41

1.78

0.88 ( 34%) 0.32 ( 29%)

0.88 ( 78%)

1.35 ( 56%)

1.66 ( 93%)

3.06

1.26

2.40

2.86

2.76

-0.14 ( -5%) -0.07 ( -6%)

-0.55 ( -23%)

-0.17 ( -6%)

0.17 ( 6%)

•SCIA1: MOZART NO2 profile / SCIA2: WRF-Chem NO2 profile•Model is overestimated to SCIA and is underestimated to OMI. However, both satellites show good agreement with model for Four Corners/San Juan power plants. In general, smaller boxes show higher biases for SCIA

Summary: Power Plants

5. Conclusions

* Satellite NO2 columns agree well with model NO2 columns over the regions where total NOx emission is dominated by power plants. For small size power plants, however, SCIAMACHY data are higher than the model results, while OMI and the model agree reasonably well, implying that the data frequency and resolution of SCIAMACHY limit the detection of these confined power plants.

* Applying positive advection scheme for RACM-ESRL (not done yet) may reduce discrepancy between SCIAMACHY and the model and increase discrepancy between OMI and the model.

* Inclusion of hourly and daily varying power plant emissions may reduce the discrepancy between model and satellites.

* The analysis can be extended to urban and highway emissions, which was known to be much more uncertain than those from power plants.

* Include daily variation of emissions from Four Corners and San Juan Power Plants: reductions in weekends and holidays by 25%

6. Future Plans