Use of remote ozone and aerosol measurements and back trajectory calculations in interpretation of the Arctic troposphere springtime ozone maximum

 

William B. Grant, Edward V. Browell, Johnathan W. Hair, Carolyn F. Butler, Russell J. DeYoung, Vincent G. Brackett, Lorraine H. Brasseur, Marian B. Clayton, Marta A. Fenn, David B. Harper, Anthony Notari, and Jerry A. Williams, NASA Langley Research Center, Hampton, VA 23681; 757-864-5846; e-mail: w.b.grant@larc.nasa.gov); Jennie L. Moody and Anthony J. Wimmers (University of Virginia, Charlottesville, VA)

 

The Tropospheric Ozone Production about the Spring Equinox (TOPSE) mission, which ran from February 4 to May 23, 2000, had as its major goal to investigate the chemical and dynamic evolution of tropospheric composition over mid- to high-latitude continental North America during the winter/spring transition, with particular emphasis on the springtime ozone maximum. The NASA Langley UV differential absorption lidar (DIAL) system participated in that mission, and was able to provide vertical cross sections of aerosol and ozone distributions from near the surface to the lower stratosphere along the flight tracks. During the early part of the mission, the air was relatively cold and stable, and thin layers of elevated aerosols and ozone were often observed. For example, on February 25, layers of enhanced aerosols and ozone were observed from 2-6 km. The back trajectories from the flight track in the 60o-70oN region were from Arizona, California, and Washington state. On the flights from 60o-70oN of April 4, 7, 25, 28 and May 18, the highest ozone in the 2-6 km region of tropospheric origin was observed. (On 4 of these flights the only SO2 plumes north of 60oN were seen.) The 5-day back trajectories for these 5 flight segments were primarily from Siberia or East Asia, from approximately 65o-80oN and 90o-180oE. The flight of April 25 also had elevated ozone mixing ratio for a 5-day back trajectory going back to Japan (40oN, 140oE). Inspection of the NOAA-CIRES Climate Diagnostics Center, Boulder, Colorado, USA, web site (http://www.cdc.noaa.gov/) indicates that when the back trajectories ended in Siberia and East Asia, the air flow to there was usually coming from urban/industrial regions of Europe, Russia or East Asia, with that from Europe sometimes going south before heading north. Additional in situ chemical concentration data will be examined to aid in the determination of source regions of the elevated ozone. This transport process can be a significant contributing factor to the observed springtime ozone maximum observed in the Arctic free troposphere.

 

 


Use of remote ozone and aerosol measurements and back trajectory calculations in interpretation of the Arctic troposphere springtime ozone maximum

 

William B. Grant,1 Edward V. Browell,1 Carolyn F. Butler,2 Russell J. DeYoung,1 Johnathan W. Hair,1 Vincent G. Brackett,2 L. H. Brasseur,2 Marian B. Clayton,2 Marta A. Fenn,2 David B. Harper,2 Anthony Notari,2 Jerry A. Williams,1 Anthony J. Wimmers,3 Jennie L. Moody3

1 Atmospheric Sciences Research, NASA Langley Research Center, MS 401A, Hampton, VA 23681-2199, w.b.grant@larc.nasa.gov, e.v.Browell@larc.nasa.gov

2 Science Applications International Corporation, c/o NASA Langley Research Center, MS 401A, Hampton, VA 23681-2199

3 Department of Environmental Sciences, University of Virginia, P.O. Box 400123, Charlottesville, VA 22904-4123, ajw7g@unix.mail.virginia.edu, jlm8h@Virginia.edu

 

TOPSE Evidence is presented supporting the hypothesis that the springtime tropospheric ozone maximum arises primarily from transport from tropospheric regions outside the Arctic. The source regions, dating back 5-10 days, change from the Pacific Ocean in February and March to Europe and Asia in April and May. Photochemical production in the source regions and during transport play major roles, with destruction by deposition to land surfaces playing minor roles. There is no evidence that stratospheric intrusions contribute to the annual cycle in tropospheric ozone in the Arctic. There is support for this assessment in the prior literature.


Backward Trajectories for TOPSE Flight Altitudes, Calculated by University of Virginia

 

Representative backward trajectories are shown for two periods: prior to April 4 and on or after April 4. 10-day backward trajectories are shown for flight altitudes >4 km. For the first period, Flights 7 (February 7) and 12 (February 25), the 10-day backward trajectories show that the air masses had long residence times over the oceans; for the second period, Flights 26 (April 4) and 39 (May 18), the air masses spent several days over Eurasia prior to reaching the flight track. When the air masses spend long times over oceans, the ozone precursors can decay and be diluted. While there was transport over the U.S. for Flight 12, it was not a period of high-activity photochemistry, and only a portion of the backward trajectories traversed urban/industrial areas.
Wind fields from NOAA-CIRES Climate Diagnostics Center for 2000.

700 mb (3.0 km):

February flow into Arctic from Atlantic and Pacific Oceans, very little from Siberia;

March flow into Arctic from Atlantic and Pacific Oceans, a little from Siberia;

April 1-15 flow into the Arctic from the Atlantic Ocean over Greenland, a bit from Siberia and the Pacific Ocean;

April 16-30 flow into the Arctic from the west coast of North America, over Greenland, and from Siberia;

May flow into the Arctic from the Atlantic Ocean and Europe, Siberia, and the west coast of North America;

June flow into the Arctic from the Pacific Ocean below Alaska and the Atlantic Ocean.

 

500 mb (5.6 km):

March 1-15 flow in from Pacific Ocean, Siberia, Atlantic Ocean;

March 16-30 flow in from Pacific Ocean, Atlantic Ocean;

April 1-15 flow in from Siberia, Atlantic Ocean, Pacific Ocean;

April 15-30 flow in from Atlantic Ocean, west coast of North America;

May 1-15 flow in from Atlantic Ocean, Siberia;

May 16-30 flow in from Europe;

June 1-15 flow in from Pacific Ocean, Siberia, Europe?

 

 


Transport. Iversen et al. [1989] find that the occurrence of atmospheric flow systems on planetary scale is the major cause of long-range transport of polluted air to the Arctic during winter/spring. Sulfate is the pollution species used in this analysis, and its concentrations peak in FMA at Bjornoya (75oN) and March with high values also found for February and April at Ny Alesund (80oN).

 

Pacyna [1995] points out the importance of the emissions from Eurasia as the major contributors to Arctic pollution throughout the year. However, he points out that the wintertime south-to-north transport from Eurasia is replaced by a weak north-to-south transport in summer. This observation agrees with the aerosol data presented in Cheng et al. [1993].

 

 

Cheng, M.-D., P. K. Hopke, L. Barrie, A. Rippe, M. Olson, and S. Landsberger, Qualitative determination of source regions of aerosol in Canadian high Arctic, Environ. Sci. Technol., 27, 2063-2071, 1993.

 

Iversen, T., Some statistical properties of ground level air pollution at Norwegian Arctic stations and their relation to large scale atmospheric systems, Atmos. Environ., 23, 2451-2462, 1989.

 

Pacyna, J. M., The origin of Arctic air pollutants: lessons learned and future research, Sci. Total Environ., 160-161, 39-53, 1995.

 

 


Chemical species concentrations suggest a 7+2 day differential transit time for late May compared with late February, assuming and OH concentration of 106 ions/cm3 and summertime insolation. Since it was spring and high latitude, the transit time from the source was probably a bit longer, consistent with the backward trajectory calculations, showing Europe as a source region 10 days ago.

Lifetime

(years) (0.1 yrs) (0.01 yrs)

 

CFC114 300.00 3000.00 30000.00

CFC113 85.00 850.00 8500.00

CFC11 50.00 500.00 5000.00

CH4 7.30 73.00 730.00

CH3Cl 1.26 12.60 126.00

CO 0.23 2.30 23.00

CH2Cl2 0.20 2.00 20.00

ethane 0.10 0.97 9.73

ethyne 0.04 0.38 3.84

propane 0.02 0.21 2.14

i-butane 0.01 0.15 1.45

C2HCl3 0.01 0.14 1.37

n-butane 0.01 0.14 1.37

CH3I 0.01 0.11 1.10

i-pentane 0.01 0.08 0.85

n-pentane 0.01 0.08 0.80

CH3OOH 0.01 0.05 0.55

toluene 0.01 0.05 0.55

H2CO 3.29e-3 0.03 0.33

t-2 butene 4.90e-4 4.90e-3 0.05


Typical UV DIAL Ozone and Aerosol Data Sets for the TOPSE Mission, Along with Backward Trajectory Calculations by U VA.

 

These images show that prior to April 4, transport above 60oN was primarily from the Pacific Ocean across the United States, with low ozone and aerosol concentrations. The long time over the ocean reduced the concentration of ozone precursors, and photochemical activity was limited due to the low solar elevation angle as well.

 

On and after April 4, transport above 60oN was primarily from Eurasia, with high ozone and aerosol concentrations. There are many urban/industrial areas in Eurasia, and the solar elevation angle was higher, permitting more photochemistry to occur during transport.