Lower tropospheric ozone trend observed in 1989-1997 at Okinawa, Japan (original) (raw)
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Journal of Geophysical Research: Atmospheres, 1999
Surface 0 3 and CO measurements were carried out at Oki, Japan during March 1994 to February 1996 in order to elucidate the processes determining temporal variations of 03 and CO in the northeast Asian Pacific rim region. The isentropic trajectory analysis was applied to sort out the influences of the air mass exchange under the Asian monsoon system and the regional-scale photochemical buildup of 03. The trajectories were categorized into five groups which cover background and regionally polluted air masses. The seasonal cycles of 03 and CO in the background continental air mass revealed spring maximum-summer minimum with averaged concentrations ranging from 32 and 120 ppb to 45 and 208 ppb, respectively. In contrast, 03 concentrations in the regionally polluted continental air mass ranged from 44 to 57 ppb and showed a winter minimum and a spring-summer-autumn broad maximum, which was characterized by photochemical 03 production due to anthropogenic activities in northeast Asia. CO concentrations in the same air mass showed a spring maximum of 271 ppb and a summer-autumn minimum of 180 ppb. The photochemical buildup of 03 resulting from anthropogenic activities in this region was estimated to be 21 ppb in summer, while its production was insignificant, an average 3 ppb, in winter. A comparison between data in northeast Asia and in Europe shows many similarities, supporting the contention that photochemical buildup of 03 from large-scale precursor emissions in both regions is very significant. trajectory calculations to observational data in Europe, the Atlantic islands, and North America [Oltmans and Levy, 1992; Derwent et al., 1994; Moody et al., 1995; Harris and Oltmans, underlying mechanism, two different approaches are essentially important. One is trend analysis based on long-term data either 1997; Sirnrnonds et al., 1997]. Northeast Asia is one of the most anthropogenically active aron surface measurements or by sounding routines. Another is the eas in the world and provides an interesting study field for tropoclimatological study of ozone and its precursors which clarifies the mechanism of long-range transport and transformation. Trend spheric ozone buildup. A trend of increasing tropospheric ozone has been observed in this region based on ozone sounding data in analysis has established that surface ozone concentration has increased at least by a factor of 2 or more in many areas of Europe Japan [Akirnoto et al., 1994]. In contrast to Europe, the trend of over this century [Logan, 1985; Bojkov, 1986; Volz and Kley, increasing boundary layer ozone is still continuing in the 1990s in this area, possibly due to a trend of increasing emissions of 1988;
Characteristics of background surface ozone in Japan
Atmospheric Environment, 1994
Ahatract-A study has been performed on the characteristics and behavior of background surface ozone concentrations at 10 of the background surface ozone monitoring stations in Japan. This surface ozone monitoring network was set up in the 1980s to study the diurnal, seasonal and long-term behavior of background ozone in Japan at ~remote" sites relatively unperturbed by human influences. There is seasonal variability in the measured ozone concentrations with its peak in spring and a significant summer minimum. This summer minimum is likely due to regional air flow originating from southern marine latitudes bringing relatively clean air. Diurnal behavior varies with site elevation and location relative to urban and industrial sources. The high elevation sites in Japan show significantly higher average concentrations than similar sites in Europe and the United States of America.
A numerical study of tropospheric ozone in the springtime in East Asia
Advances in Atmospheric Sciences, 2004
The Models-3 Community Multi-scale Air Quality modeling system (CMAQ) coupled with the Regional Atmospheric Modeling System (RAMS) is applied to East Asia to study the transport and photochemical transformation of tropospheric ozone in March 1998. The calculated mixing ratios of ozone and carbon monoxide are compared with ground level observations at three remote sites in Japan and it is found that the model reproduces the observed features very well. Examination of several high episodes of ozone and carbon monoxide indicates that these elevated levels are found in association with continental outflow, demonstrating the critical role of the rapid transport of carbon monoxide and other ozone precursors from the continental boundary layer. In comparison with available ozonesonde data, it is found that the model-calculated ozone concentrations are generally in good agreement with the measurements, and the stratospheric contribution to surface ozone mixing ratios is quite limited.
Tropospheric ozone production and transport in the springtime in east Asia
Journal of Geophysical Research, 1998
Ozone transport and chemistry in the springtime in east Asia are studied by use of the STEM-II (Sulfur Transport Eulerian Model) regional-scale transport/chemistry model. Threedimensional simulations are performed for the period May 1-15, 1987. This was a period of strong downward transport of ozone in east Asia, associated with traveling low-pressure systems. Elevated ozone levels were observed at high-altitude surface sites in Japan during this period. Model simulations both with and without photochemical processes are performed in order to assess the relative importance of the transport and chemical sources of tropospheric ozone. The model results are compared with measured values at a network of stations in Japan and are found to accurately capture most of the important observed features. Near-surface ozone levels are found to be strongly influenced both by continental outflow of precursors occurring behind the cold fronts as they move out over the Pacific Ocean and by the strong downward transport of ozone-rich air from the upper troposphere which occurs in association with these weather systems. 1Now at Measurements in Japan show that ozone displays a distinct seasonal cycle [Sunwoo et al., 1992, 1994; Tsutsumi et al., 1996]. Both downward transport of ozone-rich air originating in the lower stratosphere and accumulation and production of ozone and its precursors over the winter are possible explanations for the consistent spring peak in ozone concentrations. The summer minimum may be attributed to a dynamic shift in the dominant meteorology over the region from continental northeasterly winds from China brought on by the Aleutian low-pressure system in the winter season, to mostly southerly winds bringing moist air from the lower latitudes in the summer [Whelpdale and Moody, 1990]. The summer circulation from the southern marine environments is low in ozone and precursors of ozone. Further insights into the behavior of ozone in east Asia are found by examining the hourly surface ozone data during the spring. Shown in Figure 1 is surface ozone measured at Happo, Japan, during May 1987. The Happo site is located in the middle of Honshu at an elevation of 1840 m. During this period, ozone concentrations varied from 40 to 100 ppb. Ozone showed a diurnal variation of about 10 ppb (e.g., May 6-9) superimposed on a larger synoptic-scale signal. Ozone concentrations increased dramatically during the period May 8-11, reaching a peak value of ~100 ppb. Relative humidity is also shown in . In general, the surface concentrations of ozone are anticorrelated with relative humidity, with low concentrations under conditions of high relative humidity and high concentrations during periods of low relative humidity. However, the relationship between ozone and relative humidity is quite complex. Take, for example, the high ozone episode around May 10. The initial buildup of ozone occurred in an air mass which had low relative humidity, but the peak value is associated with air which had relative humidities greater than 60%. In this study the transport and production of ozone in east Asia during the springtime are studied using a regional-scale atmospheric chemistry model. Specifically, the behavior of 10,649
Sources of tropospheric ozone along the Asian Pacific Rim
2003
The sources contributing to tropospheric ozone over the Asian Pacific Rim in different seasons are quantified by analysis of Hong Kong and Japanese ozonesonde observations with a global three-dimensional (3-D) chemical transport model (GEOS-CHEM) driven by assimilated meteorological observations. Particular focus is placed on the extensive observations available from Hong Kong in 1996. In the middle-upper troposphere (MT-UT), maximum Asian pollution influence along the Pacific Rim occurs in summer, reflecting rapid convective transport of surface pollution. In the lower troposphere (LT) the season of maximum Asian pollution influence shifts to summer at midlatitudes from fall at low latitudes due to monsoonal influence. The UT ozone minimum and high variability observed over Hong Kong in winter reflects frequent tropical intrusions alternating with stratospheric intrusions. Asian biomass burning makes a major contribution to ozone at <32°N in spring. Maximum European pollution influence (<5 ppbv) occurs in spring in the LT. North American pollution influence exceeds European influence in the UT-MT, reflecting the uplift from convection and the warm conveyor belts over the eastern seaboard of North America. African outflow makes a major contribution to ozone in the low-latitude MT-UT over the Pacific Rim during November-April. Lightning influence over the Pacific Rim is minimum in summer due to westward UT transport at low latitudes associated with the Tibetan anticyclone. The Asian outflow flux of ozone to the Pacific is maximum in spring and fall and includes a major contribution from Asian anthropogenic sources year-round.
Remote sensing evidence of decadal changes in major tropospheric ozone precursors over East Asia
Recent regulatory policies in East Asia reduce ozone precursors, but these changes are spatially and temporally nonuniform. This study investigates variations in the long-term trends of tropospheric NO 2 , HCHO, and HCHO/NO 2 ratios to diagnose ozone sensitivity to changes in NO x and volatile organic compound using the Ozone Monitoring Instrument (OMI). Using an adaptive-degree polynomial filter, we identify extremums of time series of NO 2 to determine when and how NO 2 change.
Near-ground ozone source attributions and outflow in central eastern China during MTX2006
Atmospheric Chemistry and Physics, 2008
A 3-D regional chemical transport model, the Nested Air Quality Prediction Model System (NAQPMS), with an on-line tracer tagging module was used to study the source of the near-ground (<1.5 km above ground level) ozone at Mt. Tai (36.25 • N, 117.10 • E, 1534 m a.s.l.) in Central Eastern China (CEC) during the Mount Tai eXperiment 2006 (MTX2006). The model reproduced the temporal and spatial variations of near-ground ozone and other pollutants, and it captured highly polluted and clean cases well. The simulated near-ground ozone level over CEC was 60-85 ppbv (parts per billion by volume), which was higher than values in Japan and over the North Pacific (20-50 ppbv). The simulated tagged tracer data indicated that the regionalscale transport of chemically produced ozone over other areas in CEC contributed to the greatest fraction (49%) of the near-ground mean ozone at Mt. Tai in June; in situ photochemistry contributed only 12%. Due to high anthropogenic and biomass burning emissions that occurred in the southern part of the CEC, the contribution to ground ozone levels from this area played the most important role (32.4 ppbv, 37.9% of total ozone) in the monthly mean ozone concentration at Mt. Tai; values reached 59 ppbv (62%) on 6-7 June 2006. The monthly mean horizontal distribution of chemically produced ozone from various ozone production regions indicated that photochemical reactions controlled the spatial distribution of O 3 over CEC. The regional-scale transport of pollutants also played an important role in the spatial and temporal distribution of ozone over CEC. Chemically produced ozone from the southern part of the study region can be transported northeastwardly to the northern rim of CEC; the mean contribution was 5-10 ppbv, and it reached 25 ppbv Correspondence to: J. Li (lijie8074@jamstec.go.jp) during high ozone events. Studies of the outflow of CEC ozone and its precursors, as well as their influences and contributions to the ozone level over adjacent regions/countries, revealed that the contribution of CEC ozone to mean ozone mixing ratios over the Korean Peninsula and Japan was 5-15 ppbv, of which about half was due to the direct transport of ozone from CEC and half was produced locally by ozone precursors transported from CEC.
Projection of surface ozone over East Asia in 2020
Journal of Agricultural Meteorology, 2009
To evaluate the impact of emission changes in East Asia on the surface ozone concentration, we conducted 1-year calculations with emission inventories for 2000 and 2020, using a one-way nested global-regional chemical transport model (CTM), consisting of global and regional CTMs. The global CTM was based on the chemical atmospheric general circulation model for the study of the atmospheric environment and radiative forcing (CHASER) model, while the regional part is based on the Weather Research and Forecasting (WRF)/Chem model. The anthropogenic emissions in East Asia were taken from the Regional Emission inventory in ASia (REAS). Comparison of the modeled surface ozone with ground-based observations at Mt. Tai showed that the model generally reproduced the diurnal variations of ozone in the North China Plain. For the horizontal distribution of surface ozone concentration, comparison between 2000 and 2020 revealed an ozone decrease of 1-3 ppbv in the North China Plain, where the increase of ozone precursors was most remarkable. An increase of 3-10 ppbv was also apparent in the outflow region of the North China Plain, over the Sichuan Province, Korea, and Japan. Comparison of the diurnal variations of surface ozone over the North China Plain in 2000 and in the "policy failed case" for 2020 (2020PFC) showed ozone levels peaking at 10 more in the latter, due to enhanced ozone production during the daytime.
Atmospheric Chemistry and Physics, 2008
We use an ensemble of aircraft, satellite, sonde, and surface observations for April-May 2006 (NASA/INTEX-B aircraft campaign) to better understand the mechanisms for transpacific ozone pollution and its implications for North American air quality. The observations are interpreted with a global 3-D chemical transport model (GEOS-Chem). OMI NO 2 satellite observations constrain Asian anthropogenic NO x emissions and indicate a factor of 2 increase from 2000 to 2006 in China. Satellite observations of CO from AIRS and TES indicate two major events of Asian transpacific pollution during INTEX-B. Correlation between TES CO and ozone observations shows evidence for transpacific ozone pollution. The semi-permanent Pacific High and Aleutian Low cause splitting of transpacific pollution plumes over the Northeast Pacific. The northern branch circulates around the Aleutian Low and has little impact on North America. The southern branch circulates around the Pacific High and impacts western North America. Both aircraft measurements and model results show sustained ozone production driven by peroxyacetylnitrate (PAN) decomposition in the southern branch, roughly doubling the transpacific influence from ozone produced in the Asian boundary layer. Model simulation of ozone observations at Mt. Bachelor Observatory in Oregon (2.7 km altitude) indicates a mean Asian ozone pollution contribution of 9 ± 3 ppbv to the mean observed concentration of 54 ppbv, reflecting mostly an enhancement in background ozone rather than episodic Asian plumes. Asian pollution enhanced surface ozone concentrations by 5-7 ppbv over western North America in spring 2006. The 2000-2006 rise in Asian anthropogenic emissions increased the influence by 1-2 ppbv.