In the lowermost layer of the atmosphere-the troposphere-ozone is an important source of the hydroxyl radical, an oxidant that breaks down most pollutants and some greenhouse gases. High concentrations of tropospheric ozone are toxic, however, and have a detrimental effect on human health and ecosystem productivity. Moreover, tropospheric ozone itself acts as an effective greenhouse gas. Much of the present tropospheric ozone burden is a consequence of anthropogenic emissions of ozone precursors resulting in widespread increases in ozone concentrations since the late 1800s. At present, east Asia has the fastest-growing ozone precursor emissions. Much of the springtime east Asian pollution is exported eastwards towards western North America. Despite evidence that the exported Asian pollution produces ozone, no previous study has found a significant increase in free tropospheric ozone concentrations above the western USA since measurements began in the late 1970s. Here we compile springtime ozone measurements from many different platforms across western North America. We show a strong increase in springtime ozone mixing ratios during 1995-2008 and we have some additional evidence that a similar rate of increase in ozone mixing ratio has occurred since 1984. We find that the rate of increase in ozone mixing ratio is greatest when measurements are more heavily influenced by direct transport from Asia. Our result agrees with previous modelling studies, which indicate that global ozone concentrations should be increasing during the early part of the twenty-first century as a result of increasing precursor emissions, especially at northern mid-latitudes, with western North America being particularly sensitive to rising Asian emissions. We suggest that the observed increase in springtime background ozone mixing ratio may hinder the USA's compliance with its ozone air quality standard.

On the other hand, high mixing ratios of sulfur dioxide (up to 1.5 ppb) and aerosol sulfate (up to 3 ppb) indicate the influence of fossil fuel burning. During most flights the contributions from these two sources were well mixed within the same air mass, suggesting that the sources on the ground are also close to each other. This is consistent with the assumption that biomass is mainly burnt as biofuel for domestic use in populated areas, where fossil fuel is also used. The ratios dX/dCO (X:acetone, acetonitrile, sulfur dioxide, potassium, or sulfate) measured during the flights indicate that most of the CO in the continental outflow is due to biomass or biofuel burning, whereas the majority of the aerosols results from fossil fuel burning.

Abstract. In a flight through a wave cloud during SUCCESS on 2 sampling opportunity since the particles are only minutes old and May 1996, simultaneous forward-and aft-facing NOy inlets were likely nucleated on sulfuric acid aerosols [Jensen et al., this issue]. used to infer the amount of condensed-phase NOy present on ice particles that were up to a few minutes old. Condensed-phase 2. Measurements amounts were 25-75 pptv, or 10-20% of gas-phase NOy. Given The "aft-inlet" NOy was sampled through a horizontal inlet the rapid HNO 3 uptake on ice observed in the laboratory, a model calculation implies that virtually all of the gas-phase HNO3 will be tube oriented perpendicular to the aircraft window. The tube's end depleted in the first 1-2 minutes after the appearance of ice. Thus face was a 45" cut, oriented 45" away from directly aft. This inlet , though for the ice cloud ice particles is the subject of this paper. particles of interest here, 10-20 [tm in diameter, the enhancement The partitioning of NOy between the gas and condensed phases factors are very close to the high-mass limit and so not as sizeis an important aspect of the NOy budget. Species will be subject dependent as for the smaller particles in PSCs. Since the highto different chemical and transport processes depending on mass limit is well-defined, and simply equal to the ratio of the true whether they are in the gas or condensed phase. Photolytic and air speed and the known flow velocity inside the inlet tube, chemical reactions will be different, and the vertical transport will enhancement factor errors due to flow around the inlet are be different, as particles will sediment. The presence of NOy minimal. The high-mass enhancement factor is altitude-dependent species in ice particles could result from several processes: (1) since a constant mass flow is drawn into the inlet. It has a value of They could be in the ice nuclei responsible for ice formation. (2) 43 for the case described in this paper at 41 kft. Integrations of Their presence could result from chemical conversions that occur the size-dependent enhancement factor over the particle size in/on the particles and that leave the product species in the spectrum give values which are generally within a few percent of condensed phase. Or, (3) they could be adsorbed onto the ice this upper limit when in the wave cloud and not at the very edge. surface during or after growth.On the other hand, the flow around the fuselage could also impact During SUCCESS we employed forward-and aft-facing inlets particle concentrations. Using the semi-empirical approach of to measure NOy. Since cloud ice particles are collected with King [1984], we have estimated a shadow zone depth for 10o[tm enhanced efficiency by the forward-facing inlet and discriminated diameter particles of 4 cm at the fuselage station (530 in.) of the against by the aft, the difference between the two simultaneous inlet. The inlet stuck out 37 cm into the flow, and at this point the NOy measurements enables a measurement of the amount...

Anthropogenic pollution and wildfires are main producers of carbon monoxide (CO) and black carbon (BC) in the Northern Hemisphere. High concentrations of these compounds are transported into the Arctic troposphere, influencing the ecosystem in high northern latitudes and the global climate. The global chemical transport model MOZART-4 is used to quantify the seasonal evolution of the contribution of CO and BC from different source regions in spring and summer 2008 by tagging their emissions. Aircraft observations from the POLARCAT experiments, in particular NASA ARCTAS, NOAA ARCPAC, POLARCAT-France, DLR GRACE and YAK-AEROSIB, as well as the NSF START08/preHIPPO experiments during Spring-Summer 2008 are combined to quantify the representation of simulated tracer characteristics in anthropogenic and fire plumes. In general, the model reproduces CO and BC well. Based on aircraft measurements and FLEXPART back-trajectories, the altitude contribution of emissions coming from different source regions is well captured in the model. Uncertainties of the MOZART-4 model are identified by comparing the data with model results on the flight tracks and using MOPITT satellite observations. Anthropogenic emissions are underestimated by about 10% in high northern latitudes in spring, and shortcomings exist in simulating fire plumes. The remote impact of East-Siberian fire emissions is underestimated for spring, whereas the impact of Southeast Asian fire emissions to mid-latitude CO values is overestimated by the model. In summer, mid-latitude CO values agree well between model and observations, whereas summer high latitude East-Siberian fire emissions in the model are overestimated by 20% in comparison to observations in the region. On the other hand, CO concentrations are underestimated by about 30% over Alaska and Canada at altitudes above 4 km. BC values are overestimated by the model at altitudes above 4 km in summer. Based on MOZART-4, with tagged CO and BC tracers, anthropogenic emissions of Asia, Europe and the US have the largest contribution to the CO and BC in mid- and high latitudes in spring and summer. Southeast Asian, Chinese and Indian fires have a large impact on CO pollution in spring in low latitudes with a maximum between 20° and 30°, whereas Siberian fires contribute largely to the pollution in high latitudes, up to 10% in spring and up to 30% in summer. The largest contributions to BC values in high latitudes are from anthropogenic emissions (about 70%). CO and BC have larger mass loadings in April than in July, as a result of photochemistry and dynamics

This study examined the socioeconomic impacts of Daily Extreme Precipitation Events (hereafter "DEPEs") in Belem-Pará during the period 1987-2009. The DEPEs were characterized as "extreme" using the Decile technique. The objective of the study was to identify the consequences and the main neighborhoods affected by these events. The years influenced by occurrences of El Niño or La Niña had the lowest or the highest rates of DEPEs, respectively, and as well as the number of articles published in the city's newspapers. The monthly variation showed that the DEPEs and resulting newspaper articles were higher in Eventos extremos de precipitação em Belém-PA: …