TY - JOUR

T1 - Photochemical trajectory modeling studies of the North Atlantic region during August 1993

AU - Wild, O

AU - Law, KS

AU - McKenna, DS

AU - Bandy, BJ

AU - Penkett, SA

AU - Pyle, JA

N1 - Copyright 1996 by the American Geophysical Union

PY - 1996/12/20

Y1 - 1996/12/20

N2 - A Lagrangian photochemical trajectory model has been used to assess the factors affecting O-3 production during transport of polluted air masses across the North Atlantic Ocean. Sensitivity studies have been performed along idealized trajectories, and it is found that the potential impact of North American emission sources is maximized by transport of air at high altitudes, in drier conditions and in conditions where mixing of the air with background air masses is relatively limited. Measurements taken from the NCAR King Air aircraft as part of the North Atlantic Regional Experiment (NARE) August 1993 intensive have been used to initialize forward trajectories, calculated using European Centre for Medium-Range Weather Forecasting analyzed wind fields, from eastern North America to assess O-3 production over the Atlantic during this period. The effects of dilution of a polluted air parcel with air from the upper troposphere have also been studied, and the contribution of photochemical O-3 production to the air mass composition is found to be smaller than that of dilution, particularly for long trajectories and for conditions where dilution is relatively rapid or involves air from the stratosphere. Measurements taken from the Meteorological Research Flight Hercules aircraft over the eastern Atlantic as part of the Oxidizing Capacity of the Tropospheric Atmosphere campaign have been examined in the light of these studies. A backward trajectory analysis has been performed from one of the vertical profiles taken off the coast of Portugal on August 31, 1993, to assess the origin of the different air masses intercepted. While the lower levels are characteristic of air from the European boundary layer advected over the ocean, the upper levels show strong evidence for anthropogenic influence from North American sources, with elevated levels of O-3, NOy, CO, and aerosol. Although it cannot be concluded that this air mass definitely originated from over North America, the measured concentrations are shown to be consistent with those for an air mass from this source region experiencing some mixing with air masses in the upper troposphere.

AB - A Lagrangian photochemical trajectory model has been used to assess the factors affecting O-3 production during transport of polluted air masses across the North Atlantic Ocean. Sensitivity studies have been performed along idealized trajectories, and it is found that the potential impact of North American emission sources is maximized by transport of air at high altitudes, in drier conditions and in conditions where mixing of the air with background air masses is relatively limited. Measurements taken from the NCAR King Air aircraft as part of the North Atlantic Regional Experiment (NARE) August 1993 intensive have been used to initialize forward trajectories, calculated using European Centre for Medium-Range Weather Forecasting analyzed wind fields, from eastern North America to assess O-3 production over the Atlantic during this period. The effects of dilution of a polluted air parcel with air from the upper troposphere have also been studied, and the contribution of photochemical O-3 production to the air mass composition is found to be smaller than that of dilution, particularly for long trajectories and for conditions where dilution is relatively rapid or involves air from the stratosphere. Measurements taken from the Meteorological Research Flight Hercules aircraft over the eastern Atlantic as part of the Oxidizing Capacity of the Tropospheric Atmosphere campaign have been examined in the light of these studies. A backward trajectory analysis has been performed from one of the vertical profiles taken off the coast of Portugal on August 31, 1993, to assess the origin of the different air masses intercepted. While the lower levels are characteristic of air from the European boundary layer advected over the ocean, the upper levels show strong evidence for anthropogenic influence from North American sources, with elevated levels of O-3, NOy, CO, and aerosol. Although it cannot be concluded that this air mass definitely originated from over North America, the measured concentrations are shown to be consistent with those for an air mass from this source region experiencing some mixing with air masses in the upper troposphere.

KW - CONVECTION

KW - TRANSPORT

KW - BOUNDARY-LAYER

KW - POLLUTION

KW - CHEMISTRY

KW - TROPOSPHERIC OZONE

KW - OCEAN

KW - AIR

U2 - 10.1029/96JD00837

DO - 10.1029/96JD00837

M3 - Journal article

VL - 101

SP - 29269

EP - 29288

JO - Journal of Geophysical Research: Atmospheres

JF - Journal of Geophysical Research: Atmospheres

SN - 2169-8996

IS - D22

ER -