Transport impacts on atmosphere and climate: Shipping

A User's Guide for the

A User's Guide for the CALPUFF Dispersion Model

Confidence limits for air quality model evaluations, as estimated by bootstrap and jackknife resampling methods

[1] A ship emission plume experiment was conducted about 100 km off the California coast during the NOAA Intercontinental Transport and Chemical Transformation (ITCT) 2K2 airborne field campaign. Measurements of chemical species were made from the NOAA WP-3D aircraft in eight consecutive transects of a ship plume around midday during 2.5 hours of flight. The measured species include NOx, HNO3, peroxyacetylnitrate (PAN), SO2, H2SO4, O3, CO, CO2, nonmethane hydrocarbons (NMHC), and particle number and size distributions. Observations demonstrate a NOx lifetime of ∼1.8 hours inside the ship plume compared to ∼6.5 hours (at noontime) in the moderately polluted background marine boundary layer of the experiment. This confirms the earlier hypothesis of highly enhanced in-plume NOx destruction. Consequently, one would expect the impact of ship emissions is much less severe than those predicted by global models that do not include rapid NOx destruction. Photochemical model calculations suggest that more than 80% of the NOx loss was due to the NO2 + OH reaction; the remainder was by PAN formation. The model underestimated in-plume NOx loss rate by about 30%. In addition, a comparison of measured to predicted H2SO4 in the plumes suggests that the photochemical model predicts OH variability reasonably well but may underestimate actual values. Predictions of in-plume O3 production agree well with the observations, suggesting that model-predicted peroxy radical (HO2 + RO2) levels are reasonable. The model estimated ozone production efficiency ranges from 6 to 30. The largest model bias was seen in the comparison with measured HNO3. The model overestimated in-plume HNO3 by about a factor of 6. This is most likely caused by underestimated HNO3 sinks possibly involving particle scavenging. However, limited data availability precluded a conclusive test of this possible loss process.

/pdf/an-investigation-of-the-chemistry-of-ship-emission-plumes-4j45gbzkm0.pdf

An investigation of the chemistry of ship emission plumes during ITCT 2002

The Offshore and Coastal Dispersion (OCD) model has been developed for the Minerals Management Service (MMS) to determine the impact of offshore and onshore emissions from point sources on the air quality of coastal regions. Constructed on the framework of the EPA guideline model MPTER, the OCD model incorporates overwater plume transport and dispersion as well as changes that occur as the plume crosses the shoreline. Hourly meteorological data are needed from both offshore and onshore locations, including wind direction and speed, mixing height, overwater air temperature and relative humidity, and the sea surface temperature. Observed turbulence intensities are preferred by the model but are not mandatory. Building downwash and plume rise are incorporated into the OCD model similar to their use in the Buoyant Line and Point Source (BLP) model. Partial plume penetration into elevated inversions is treated using Briggs’ model. Dispersion coefficients are proportional to turbulence intensities. A virtual so...

Mitchell Baer

Papers

Development and Evaluation of the Offshore and Coastal Dispersion Model