Reactive nitrogen and ozone over the western Pacific: Distribution, partitioning, and sources

Measurements of important reactive nitrogen species (NO, NO2, HNO3, PAN, PPN, NO3−, NOy), C1 to C6 hydrocarbons, O3, chemical tracers (C2Cl4, CO), and meteorological parameters were made in the troposphere (0 to 12 km) over the western Pacific (0°–50°N) during the Pacific Exploratory Mission-West A campaign (September–October 1991). Under clean conditions, mixing ratios of NO, NO2, NOy, and O3 increased with altitude and showed a distinct latitudinal gradient. PAN showed a midtropospheric maximum, while nitric acid mixing ratios were generally highest near the surface. Measured NOy concentrations were significantly greater than the sum of individually measured nitrogen species (mainly NOx, PAN, and HNO3), suggesting that a large fraction of reactive nitrogen present in the atmosphere is made up of hitherto unknown species. This shortfall was larger in the tropics (≈65%) compared to midlatitudes (≈40%) and was minimal in air masses with high HNO3 mixing ratios (>100 ppt). A global three-dimensional photochemical model has been used to compare observations with predictions and to assess the significance of major sources. It is possible that the tropical lightning source is much greater than commonly assumed, and both lightning source and its distribution remain a major area of uncertainty in the budgets of NOy and NOx. A large disagreement between measurement and theory exists in the atmospheric distribution of HNO3. It appears that surface-based anthropogenic emissions provide nearly 65% of the global atmospheric NOy reservoir. Relatively constant NOx/NOy ratios imply that NOy and NOx are in chemical equilibrium and the NOy reservoir may be an important in situ source of atmospheric NOx. Data are interpreted to suggest that only about 20% of the upper tropospheric (7–12 km) NOx is directly attributable to its surface NOx source, and free tropospheric sources are dominant. In situ release of NOx from the NOy reservoir, lightning, direct transport of surface NOx, aircraft emissions, and small stratospheric input collectively maintain the NOx balance in the atmosphere. It is shown that atmospheric ratios of reactive nitrogen and sulfur species, along with trajectory analysis, can be used to pinpoint the source of Asian continental outflow. Compared to rural atmospheres over North America, air masses over the Pacific are highly efficient in net O3 production. Sources of tropospheric NOx cannot yet be accurately defined due to shortcomings in measurements and theory.

[1]  D. Blake,et al.  Chemical characteristics of continental outflow from Asia to the troposphere over the western Pacific Ocean during February‐March 1994: Results from PEM‐West B , 1997 .

[2]  D. Davis,et al.  Pacific Exploratory Mission‐West A (PEM‐West A): September–October 1991 , 1996 .

[3]  D. Blake,et al.  Model study of tropospheric trace species distributions during PEM‐West A , 1996 .

[4]  S. Rowland,et al.  Assessment of ozone photochemistry in the western North Pacific as inferred from PEM‐West A observations during the fall 1991 , 1996 .

[5]  D. Davis,et al.  Reactive nitrogen over the Pacific Ocean during PEM-West A , 1996 .

[6]  D. Blake,et al.  Photostationary state analysis of the NO2‐NO system based on airborne observations from the western and central North Pacific , 1996 .

[7]  M. Koike,et al.  Ratios of reactive nitrogen species over the Pacific during PEM-West A , 1996 .

[8]  D. Blake,et al.  PEM-West A: Meteorological overview , 1996 .

[9]  J. Merrill.  Trajectory results and interpretation for PEM-West A , 1996 .

[10]  D. Blake,et al.  Three-dimensional distribution of nonmenthane hydrocarbons and halocarbons over the northwestern Pacific during the 1991 Pacific Exploratory Mission (PEM-West A) , 1996 .

[11]  D. Blake,et al.  Chemical characteristics of continental outflow from Asia to the troposphere over the western Pacific Ocean during September–October 1991: Results from PEM-West A , 1996 .

[12]  J. Bradshaw,et al.  Asian influence over the western North Pacific during the fall season: Inferences from lead 210, soluble ionic species and ozone , 1996 .

[13]  S. Rowland,et al.  Comparison of free tropospheric western Pacific air mass classification schemes for the PEM‐West A experiment , 1996 .

[14]  R. Chatfield.  Anomalous HNO3/NOx ratio of remote tropospheric air: Conversion of nitric acid to formic acid and NOx? , 1994 .

[15]  D. Jacob,et al.  Origin of tropospheric NO x over subarctic eastern Canada in summer , 1994 .

[16]  E. M. Bailey,et al.  O3 and NO y relationships at a rural site , 1994 .

[17]  S. Wofsy,et al.  SUMMERTIME DISTRIBUTION OF PAN AND OTHER REACTIVE NITROGEN SPECIES IN THE NORTHERN HIGH-LATITUDE ATMOSPHERE OF EASTERN CANADA , 1994 .

[18]  G. W. Sachse,et al.  Summertime partitioning and budget of NOy compounds in the troposphere over Alaska and Canada: ABLE 3B , 1994 .

[19]  D. Fahey,et al.  Reactive nitrogen and its correlation with ozone in the lower stratosphere and upper troposphere , 1993 .

[20]  Paul J. Crutzen,et al.  Reaction of N2O5 on tropospheric aerosols: Impact on the global distributions of NO x , O3, and OH , 1993 .

[21]  Nobuo Kato,et al.  Anthropogenic emissions of SO2 and NOx in Asia : emission inventories , 1992 .

[22]  D. Blake,et al.  Summertime tropospheric observations related to N x O y distributions and partitioning over Alaska: Arctic Boundary Layer Expedition 3A , 1992 .

[23]  D. Jacob,et al.  Summertime photochemistry of the troposphere at high northern latitudes , 1992 .

[24]  P. Crutzen,et al.  Relationship of peroxyacetyl nitrate to active and total odd nitrogen at northern high latitudes: influence of reservoir species on NOx and O3. , 1992, Journal of geophysical research.

[25]  E. Atlas,et al.  Partitioning and budget of NO y species during the Mauna Loa Observatory Photochemistry Experiment , 1992 .

[26]  B. Huebert,et al.  Measurements of nitric acid and aerosol nitrate at the Mauna Loa Observatory during the Mauna Loa Observatory Photochemistry Experiment 1988 , 1992 .

[27]  D. Ehhalt,et al.  Sources and distribution of NO x in the upper troposphere at northern mid‐latitudes , 1992 .

[28]  H. Singh,et al.  Atmospheric distribution and sources of nonmethane hydrocarbons , 1992 .

[29]  Nobuo Kato,et al.  Anthropogenic emissions of SO 2 and NO x in Asia: Emission inventories , 1992 .

[30]  P. Crutzen,et al.  A 3 Dimensional Global Study of the Photochemistry of Ethane and Propane in the Troposphere: Production and Transport of Organic Nitrogen Compounds , 1992 .

[31]  P. Kasibhatla,et al.  The relative impact of stratospheric photochemical production on tropospheric NO y levels: A model study , 1991 .

[32]  Henning Rodhe,et al.  A global three-dimensional model of the tropospheric sulfur cycle , 1991 .

[33]  P. Crutzen,et al.  A two-dimensional study of ethane and propane oxidation in the troposphere , 1991 .

[34]  P. Crutzen,et al.  The changing photochemistry of the troposphere , 1991 .

[35]  B. Ridley.  Recent measurements of oxidized nitrogen compounds in the troposphere , 1991 .

[36]  B. Huebert,et al.  Peroxyacetyl nitrate measurements during CITE 2 - Atmospheric distribution and precursor relationships , 1990 .

[37]  S. M. Beck,et al.  Aircraft measurements of NO x over the eastern Pacific and continental United States and implications for ozone production , 1990 .

[38]  S. M. Beck,et al.  Ratios of peroxyacetyl nitrate to active nitrogen observed during aircraft flights over the eastern Pacific Oceans and continental United States , 1990 .

[39]  B. Huebert,et al.  Measurements of the nitric acid to NOx ratio in the troposphere , 1990 .

[40]  Robert C. Harriss,et al.  Measuring tropospheric HNO3: Problems and prospects for nylon filter and mist chamber techniques , 1990 .

[41]  P. Crutzen,et al.  Parameterization of vertical tracer transport due to deep cumulus convection in a global transport model and its evaluation with 222Radon measurements , 1990 .

[42]  J. Prospero,et al.  Effect of continental sources on nitrate concentrations over the Pacific Ocean , 1989, Nature.

[43]  D. Fahey,et al.  Reactive nitrogen species in the troposphere: measurements of NO , 1986 .

[44]  J. Mugler,et al.  NASA global tropospheric experiment , 1983 .

[45]  P. Hanst,et al.  Peroxyacetyl nitrate (PAN) in the unpolluted atmosphere: An important reservoir for nitrogen oxides , 1981 .