Browsing by Author "Honrath, Richard"
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- Absorption coefficients by aerosols in remote areas: a new approach to decouple dust and black carbon absorption coefficient using seven-wavelength Aethalometer dataPublication . Fialho, Paulo; Hansen, Anthony; Honrath, RichardWe present a new approach to decouple aerosol absorption coefficients due to iron oxide in Sahara dust from those due to black carbon (BC) particles. Absorption coefficients, σaerosol(λ,t), were measured at the summit of Pico mountain (2225 m ASL) in the Azores Islands using a seven-wavelength Aethalometer. Measurements between 27th July and 1st August, 2001, are analyzed here. Variations in aerosol absorption coefficients were uncorrelated to those of CO during the latter part of this period, suggesting the presence of non-combustion-derived aerosol, apparently African dust. To differentiate between BC and other absorbing particles, we analyzed the wavelength dependence of σaerosol(λ,t) and determined a best-fit exponent during the later period equal to -2.9±0.2, somewhat lower than previously reported for soil dust. Using this method, it is possible to estimate the aerosol absorption due to BC and that due to soil dust separately through the full period analyzed.
- The Azores Islands: A Unique Location for Ground-Based Measurements in the MBL and FT of the Central North Atlantic.Publication . Honrath, Richard; Fialho, PauloThe Azores Islands - the only islands in the central North Atlantic that are distant from all surrounding continentes - have historically been important for studies of the North Atlantic atmosphere. Prior to the advent of satellite observations, they provided weather data critical to the accuracy of forecasts of European weather. Today, they provide a unique base for observations of the impacts on atmospheric composition of emissions from the surrounding continents. As part of the NARE program, ground-based measurements of CO and O3 [Parrish et al., 1998] and NOY [Peterson et al., 1998], as well as ozone sondes [Oltmans et al., 1996] were made in 1993 on the island of Terceira. The Azores have also served as a base for airborne studies (e.g., those described by Law et al., this issue) and shipboard studies [e.g., Huebert et al., 1996]. Here, we briefly discuss Azores ground-based measurements, with an emphasis on a new mountaintop site designed to probe the free troposphere. […].
- Identification of black carbon and dust aerosol events at the Azores PICO-NARE station during the ICARTT experiment.Publication . Fialho, Paulo; Barata, Filipe; Honrath, Richard; Hansen, AnthonyDuring the International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) experiment (July – August 2004), aerosol samples were taken and their aerosol absorption coefficients measured. At the same time the levels of carbon monoxide and ozone where also monitored. These measurements were taken at PICO-NARE site on Pico mountain summit (2225 m ASL) in the Azores Islands. This site is in the pathway of air masses that travel from the surrounding continents (Africa, Europe and North America) that carry with them, among other species, aerosols resulting from combustions (black carbon) and/or natural emissions (dust). In particular, transport from Africa may bring soil dust particles, rich in iron oxides, which are involved in the biogeochemical cycling of iron, an essential micronutrient to marine phytoplankton (Arimoto, Balsam, & Schloesslin, 2002). During this period the sampled masses mainly came form the North American and during sometimes carried with them pollutants resulting from forest fires that occurred in Canada and Alaska.
- Impacts of anthropogenic and boreal fire emissions in the central North Atlantic lower free troposphere: summertime observations at the PICO-NARE observatory.Publication . Val Martin, Maria; Honrath, Richard; Kleissl, J.; Owen, Robert; Lapina, K.; Fialho, Paulo; Helmig, Detlev; Tanner, D. M.We present measurements of CO, O3, aerosol Black Carbon (BC) made over the central North Atlantic lower Free Troposphere (FT) during the summers of 2001-2004 along with measurements of nitrogen oxides (NOx and NOy) made during the summer of 2004 (ICARTT period) and non-methane hydrocarbons (NMHCs) made during the winter 2004-spring 2005.
- Large-scale impacts of anthropogenic and boreal fire emissions apparent in multi-year free tropospheric observations in the Azores.Publication . Honrath, Richard; Val Martin, Maria; Kleissl, J.; Owen, Robert; Lapina, K.; Fialho, Paulo; Helmig, Detlev; Tanner, D. M.Pico Mountain in the Azores Islands provides an ideal location for studies of the central N. Atlantic lower free troposphere. The PICO-NARE station has operated there since summer 2001. Here, we present key findings from summertime measurements, during 2001-2004. Main Findings: Anthropogenic and boreal wildfire emissions dominate variations in CO and have major impacts on O3, nitrogen oxides, non-methane hydrocarbons (NMHCs) and black carbon.
- Late summer changes in burning conditions in the boreal regions and their implications for NO x and CO emissions from boreal firesPublication . Lapina, K.; Honrath, Richard; Owen, R. Chris; Val Martin, Maria; Hyer, E. J.; Fialho, PauloBuilding emission inventories for the fires in boreal regions remains a challenging task with significant uncertainties in the methods used. In this work, we assess the impact of seasonal trends in fuel consumption and flaming/smoldering ratios on emissions of species dominated by flaming combustion (e.g., NO x ) and species dominated by smoldering combustion (e.g., CO). This is accomplished using measurements of CO and NO y at the free tropospheric Pico Mountain observatory in the central North Atlantic during the active boreal fire seasons of 2004 and 2005. ΔNO y /ΔCO enhancement ratios in aged fire plumes had higher values in June-July (7.3 × 10−3 mol mol−1) relative to the values in August-September (2.8 × 10−3 mol mol−1), indicating that NO x /CO emission ratios declined significantly as the fire season progressed. This is consistent with our understanding that an increased amount of fuel is consumed via smoldering combustion during late summer, as deeper burning of the drying organic soil layer occurs. A major growth in fuel consumption per unit area is also expected, due to deeper burning. Emissions of CO and NO x from North American boreal fires were estimated using the Boreal Wildland Fire Emissions Model, and their long-range transport to the sampling site was modeled using FLEXPART. These simulations were generally consistent with the observations, but the modeled seasonal decline in the ΔNO y /ΔCO enhancement ratio was less than observed. Comparisons using alternative fire emission injection height scenarios suggest that plumes with the highest CO levels at the observatory were lofted well above the boundary layer, likely as a result of intense crown fires.
- North American Boreal Wildfire and Anthropogenic Emissin Impacts in the Lower Free Troposphere over the North Atlantic Region: observations at the PICO-NARE stationPublication . Fialho, Paulo; Val Martin, Maria; Honrath, Richard; Owen, Robert; Pfister, Gabriele; Lapina, K.; Barata, FilipeWe present analyses of CO, O3, nitrogen oxides (NOx and NOy) and aerosol black carbon (BC) measurements made in the lower free troposphere (FT) over the North Atlantic region during summers 2004 (ICARTT period) and 2005.
- A permanent free tropospheric observatory at Pico summit in the Azores Islands? Past measurements (2001–2005) and future plans.Publication . Honrath, Richard; Fialho, Paulo; Helmig, Detlev; Val Martin, Maria; Owen, Robert; Kleissl, J.; Strane, J. M.; Dziobak, Michael P.; Tanner, D. M.; Barata, Filipe; Lapina, K.Pico mountain in the Azores Islands provides a base for continuous, free tropospheric measurements that is unique in the central North Atlantic region. The PICO-NARE station was installed there in 2001 as a temporary observatory. However, the location proved ideal for studies of aged emissions from anthropogenic (N. American) and boreal fire (N. American and Russian) emissions, as well as for less frequent interception of European and African plumes. As a result, station operation was continued through summer 2005, and we are planning for continuing operation and conversion into a permanent Portuguese GAW station in the future. This poster will provide an overview of the station, the measurements made there, typical transport pathways to the station and interannual variability in transport, and an overview of the full suite of multi-season observations and key findings from measurements to date. In addition, data availability and near-term and long-term plans for the station's future will be discussed.
- Photochemical evolution of continental outflow to Pico Mountain (Azores): Integrating observations with CTM simulations in lowerFT outflow.Publication . Honrath, Richard; Owen, Robert; Li, Q. B.; Helmig, Detlev; Fialho, PauloAn analysis of the consistency of lower-FT observations with chemical transport model (CTM) simulations in aged U.S. export.
- Regional and hemispheric impacts of anthropogenic and biomass burning emissions on summertime CO and O3 in the North Atlantic lower free tropospherePublication . Honrath, Richard; Owen, R. Chris; Val Martin, Maria; Reid, J. S.; Lapina, K.; Fialho, Paulo; Dziobak, Michael P.; Kleissl, J.; Westphal, D. L.We report summertime measurements of CO and O3 obtained during 2001–2003 at the PICO-NARE mountaintop station in the Azores. Frequent events of elevated CO mixing ratios were observed. On the basis of backward trajectories arriving in the free troposphere and global simulations of biomass burning plumes, we attribute nearly all these events to North American pollution outflow and long-range transport of biomass burning emissions. There was a high degree of interannual variability in CO levels: median [CO] ranged from 65 ppbv in 2001 to 104 ppbv in 2003. The highest concentrations were associated with transport of Siberian fire emissions during summer 2003, when Siberian fire activity was unusually high. Ozone mixing ratios also increased (by up to ∼30 ppbv) during the fire events. These findings demonstrate the significant hemispheric scale impact that biomass burning events have on background CO and O3 levels. O3 enhancements of similar magnitude were also observed in North American pollution outflow. O3 and CO were correlated during North American outflow events, with a slope averaging 1.0 (d[O3]/d[CO], ppbv/ppbv) when no fire impact was present. This slope is more than 80% larger than early 1990s observations made in the eastern United States and nearshore outflow region, even after accounting for declining U.S. CO emissions and for CO loss during transport to the Azores, and is not consistent with simple dilution of U.S. outflow with marine background air. We conclude that a significantly larger amount of O3 production occurred in the air sampled during this study, and we suggest several potential reasons for this, each of which could imply potentially significant shortcomings in current estimates of the hemispheric impact of North American emissions on tropospheric ozone and should be evaluated in future studies.