Variation Of Mixing Ratio Research Articles

First detection of tidal behaviour in polar mesospheric water vapour by ground based microwave spectroscopy

Abstract. Mesospheric water vapour has been observed above ALOMAR in northern Norway (69° N 16° E) by our group since 1995 using a 22 GHz ground based microwave spectrometer. A new instrument with higher sensitivity, providing a much better time resolution especially in the upper mesosphere, was installed in May 2008. The time resolution is high enough to provide observations of daily variations in the water vapour mixing ratio. We present the first ground based detections of tidal behaviour in the polar middle atmospheric water vapour distribution. Diurnal and semidiurnal variations of water vapour have been observed and due to the long chemical lifetime of water they are assumed to be caused by changing wind patterns which transport water-rich or poor air into the observed region. The detected tidal behaviour does not follow any single other dynamical field but is instead assumed to be a result of the different wind components. Both the diurnal and semidiurnal amplitude and phase components are resolved. The former shows a stable seasonal behaviour consistent with earlier observations of wind fields and model calculations, whereas the latter appears more complex and no regular behaviour has so far been observed.

Shipboard measurements and modeling of the distribution of CH4 and 13CH4 in the western Pacific

We present observations of methane (CH4) mixing ratio and 13C/12C isotopic ratios in CH4 (δ13C) data from a collaborative shipboard project using bulk carrier ships sailing between Nelson, New Zealand, and Osaka, Japan, in the western Pacific Ocean. Measurements of the CH4 mixing ratio and δ13C in CH4were obtained from large clean‐air samples collected in each 2.5° to 5° of latitude between 30°S and 30°N on eight voyages from 2004 to 2007. The data show large variations in CH4 mixing ratio in the tropical western Pacific, and data analysis suggests that these large variations are related to the positions and strengths of the South Pacific Convergence Zone and the Intertropical Convergence Zone, with variability in the sources playing a much smaller role. These measurements are compared with results from a modified version of the Unified Model (UMeth) general circulation model along two transects, one similar to the ship transects and another 18.75° to the east. Although UMeth was run to a steady state with the same sources and sinks each year, the gradient structures varied considerably from year to year, supporting our conclusion that variability in transport is a major driver for the observed variations in CH4. Simulations forced with an idealized representation of the El Niño‐Southern Oscillation (ENSO) suggest that a large component of the observed variability in latitudinal gradients of CH4 and its δ13C arises from intrinsic variability in the climate system that does not occur on ENSO time scales.

Some features of water vapor mixing ratio in tropical upper troposphere and lower stratosphere: Role of convection

Spatial and temporal variation of water vapor mixing ratio (WVMR) is examined for its association with the convective activity in upper troposphere and lower stratosphere over tropical region particularly Asian monsoon region (AMR) and Indonesian–Australian West Pacific region (IAWPR) using WVMR obtained from MLS satellite with simultaneous daily mean OLR from NOAA and daily mean wind from NCEP reanalysis. An examination of WVMR at various pressure levels during high water vapor regime (moist Phase) indicates that water vapor (WV) transport, in troposphere, is rather fast up to a level of ~147hPa. Seasonal variation of WVMR over tropical lower stratosphere (TLS) is noted to be closely associated with seasonal northward movement of intertropical convergence zone (ITCZ). Convection activity over AMR appears to be a prominent contributor to the moist phase of WVMR seasonal cycle in TLS. However, other tropical regions may also be contributing to the seasonal variability of WVMR. Low WV (dry) phase of the WVMR seasonal cycle in TLS observed during NH winter and early spring months may be caused by the appearance of extreme cold temperatures (≤191K) close to tropopause heights over IAWPR. Mechanisms that could cause such low temperatures over IAWPR are discussed. Intraseasonal oscillations with period of 30–40days are observed in WVMR at various pressure levels. At 100hPa level such oscillations are noted to be closely associated with similar oscillation in OLR and temperature. These observations suggest that variations in OLR (proxy of convection activity) produce such oscillation in WVMR. Present analysis thus report signature of convection in upward transport of WV, seasonal and intraseasonal oscillation in WVMR in upper troposphere and lower stratosphere (UTLS).

Contrasting winter and summer VOC mixing ratios at a forest site in the Western Mediterranean Basin: the effect of local biogenic emissions

Abstract. Atmospheric volatile organic compounds (VOCs) are involved in ozone and aerosol generation, thus having implications for air quality and climate. VOCs and their emissions by vegetation also have important ecological roles as they can protect plants from stresses and act as communication cues between plants and between plants and animals. In spite of these key environmental and biological roles, the reports on seasonal and daily VOC mixing ratios in the literature for Mediterranean natural environments are scarce. We conducted seasonal (winter and summer) measurements of VOC mixing ratios in an elevated (720 m a.s.l.) holm oak Mediterranean forest site near the metropolitan area of Barcelona (NE Iberian Peninsula). Methanol was the most abundant compound among all the VOCs measured in both seasons. While aromatic VOCs showed almost no seasonal variability, short-chain oxygenated VOCs presented higher mixing ratios in summer, presumably due to greater emission by vegetation and increased photochemistry, both enhanced by the high temperatures and solar radiation in summer. Isoprenoid VOCs showed the biggest seasonal change in mixing ratios: they increased by one order of magnitude in summer, as a result of the vegetation's greater physiological activity and emission rates. The maximum diurnal concentrations of ozone increased in summer too, most likely due to more intense photochemical activity and the higher levels of VOCs in the air. The daily variation of VOC mixing ratios was mainly governed by the wind regime of the mountain, as the majority of the VOC species analyzed followed a very similar diel cycle. Mountain and sea breezes that develop after sunrise advect polluted air masses to the mountain. These polluted air masses had previously passed over the urban and industrial areas surrounding the Barcelona metropolitan area, where they were enriched in NOx and in VOCs of biotic and abiotic origin. Moreover, these polluted air masses receive additional biogenic VOCs emitted in the local valley by the vegetation, thus enhancing O3 formation in this forested site. The only VOC species that showed a somewhat different daily pattern were monoterpenes because of their local biogenic emission. Isoprene also followed in part the daily pattern of monoterpenes, but only in summer when its biotic sources were stronger. The increase by one order of magnitude in the concentrations of these volatile isoprenoids highlights the importance of local biogenic summer emissions in these Mediterranean forested areas which also receive polluted air masses from nearby or distant anthropic sources.

A Diagnostic for Evaluating the Representation of Turbulence in Atmospheric Models at the Kilometric Scale

Abstract Turbulence is well represented by atmospheric models at very fine grid sizes, from 10 to 100 m, for which turbulent movements are mainly resolved, and by atmospheric models with grid sizes greater than 2 km, for which those movements are entirely parameterized. But what happens at intermediate scales, Wyngaard’s so-called terra incognita? Here an original method is presented that provides a new diagnostic by calculating the subgrid and resolved parts of five variables at different scales: turbulent kinetic energy (TKE), heat and moisture fluxes, and potential temperature and mixing ratio variances. They are established at intermediate scales for dry and cumulus-topped convective boundary layers. The similarity theorem allows the determination of the dimensionless variables of the problem. When the subgrid and resolved parts are studied, a new dimensionless variable, the dimensionless mesh size , needs to be added to the Deardorff free convective scaling variables, where h is the boundary layer height and hc is the height of the cloud layer. Similarity functions for the subgrid and resolved parts are assumed to be the product of the similarity function of the total (subgrid plus resolved) variables and a “partial” similarity function that depends only on . In order to determine the partial similarity function form, large-eddy simulations (LES) of five dry and cloudy convective boundary layers are used. The resolved and subgrid parts of the variables at coarser grid sizes are then deduced from the LES fields. The evolution of the subgrid and resolved parts in the boundary layer with is as follows: fine grids mainly resolve variables. As the mesh becomes coarser, more eddies are subgrid. Finally, for very large meshes, turbulence is entirely subgrid. A scale therefore exists for which the subgrid and resolved parts are equal. This is obtained for in the case of TKE, 0.4 for the potential temperature variance, and 0.8 for the mixing ratio variance, indicating that the velocity structures are smaller than those for the potential temperature, which are smaller than those for the mixing ratio. Furthermore, boundary layers capped by convective clouds have structures larger than dry boundary layer ones as displayed by the scaling in the partial similarity functions. This new diagnostic gives a reference for evaluating current and future parameterizations at kilometric scales. As an illustration, the parameterizations of a mesoscale model are eventually evaluated at intermediate scales. In its standard version, the model produces too many resolved movements, as the turbulence scheme does not sufficiently represent the impact of the subgrid thermal. This is not true when a mass-flux scheme is introduced. However in this case, a completely subgrid thermal is modeled leading to an overestimation of the subgrid part.

The impact of soil uptake on the global distribution of molecular hydrogen: chemical transport model simulation

Abstract. The global tropospheric distribution of molecular hydrogen (H2) and its uptake by the soil are simulated using a model called CHemical AGCM (atmospheric general circulation model) for the Study of the Environment and Radiative forcing (CHASER), which incorporates a two-layered soil diffusion/uptake process component. The simulated distribution of deposition velocity over land is influenced by regional climate, and has a global average of 3.3×10−2 cm s−1. In the region north of 30° N, the amount of soil uptake shows a large seasonal variation corresponding to change in biological activity due to soil temperature and change in diffusion suppression by snow cover. In the temperate and humid regions in the mid- to low- latitudes, the uptake is mostly influenced by the soil air ratio, which controls the gas diffusivity in the soil. In the semi-arid regions, water stress and high temperatures contribute to the reduction of biological activity, as well as to the seasonal variation in the deposition velocity. A comparison with the observations shows that the model reproduces both the distribution and seasonal variation of H2 relatively well. The global burden and tropospheric lifetime of H2 are 150 Tg and 2.0 yr, respectively. The seasonal variation in H2 mixing ratios at the northern high latitudes is mainly controlled by a large seasonal change in the soil uptake. In the Southern Hemisphere, seasonal change in net chemical production and inter-hemispheric transport are the dominant causes of the seasonal cycle, while large biomass burning contributes significantly to the seasonal variation in the tropics and subtropics. Both observations and the model show large inter-annual variations, especially for the period 1997–1998, associated with large biomass burning in the tropics and at Northern Hemisphere high latitudes. The soil uptake shows relatively small inter-annual variability compared with the biomass burning signal. Given that the thickness of biologically inactive layer plays an important role in the soil uptake of H2, its value in the model is chosen to achieve agreement with the observed H2 trends. Uncertainty of the estimated soil uptake flux in the semi-arid region is still large, reflecting the discrepancy in the observed and modeled seasonal variations.

Ground level volume mixing ratio of methane in a tropical coastal city

Urban regions are hotspots of greenhouse gas emissions which include CO(2), CH(4), N(2)O, etc. Methane is a strong greenhouse gas which is produced from a number of sources including fossil fuel combustion, municipal waste, and sewage processing, etc. Ground level mixing ratio of methane in the tropical coastal city of Thiruvananthapuram in South India, during calm early morning period was measured. Measurements were done during both winter and summer seasons. Concentrations were significantly higher than global average value. Intra-city variation in ground level mixing ratio was also significant. Ground level methane concentration at Thiruvananthapuram urban area showed maximum value of 3.16ppmV. Under stable atmospheric conditions in early morning, ground level mixing ratio of methane was 2.79ppmV in winter and 2.54ppmV during summer. The spatial distribution of methane concentration shows correlation with urban heat island.

Analysis of reactive bromine production and ozone depletion in the Arctic boundary layer using 3-D simulations with GEM-AQ: inference from synoptic-scale patterns

Abstract. Episodes of high bromine levels and surface ozone depletion in the springtime Arctic are simulated by an online air-quality model, GEM-AQ, with gas-phase and heterogeneous reactions of inorganic bromine species and a simple scheme of air-snowpack chemical interactions implemented for this study. Snowpack on sea ice is assumed to be the only source of bromine to the atmosphere and to be capable of converting relatively stable bromine species to photolabile Br2 via air-snowpack interactions. A set of sensitivity model runs are performed for April 2001 at a horizontal resolution of approximately 100 km×100 km in the Arctic, to provide insights into the effects of temperature and the age (first-year, FY, versus multi-year, MY) of sea ice on the release of reactive bromine to the atmosphere. The model simulations capture much of the temporal variations in surface ozone mixing ratios as observed at stations in the high Arctic and the synoptic-scale evolution of areas with enhanced BrO column amount ("BrO clouds") as estimated from satellite observations. The simulated "BrO clouds" are in modestly better agreement with the satellite measurements when the FY sea ice is assumed to be more efficient at releasing reactive bromine to the atmosphere than on the MY sea ice. Surface ozone data from coastal stations used in this study are not sufficient to evaluate unambiguously the difference between the FY sea ice and the MY sea ice as a source of bromine. The results strongly suggest that reactive bromine is released ubiquitously from the snow on the sea ice during the Arctic spring while the timing and location of the bromine release are largely controlled by meteorological factors. It appears that a rapid advection and an enhanced turbulent diffusion associated with strong boundary-layer winds drive transport and dispersion of ozone to the near-surface air over the sea ice, increasing the oxidation rate of bromide (Br−) in the surface snow. Also, if indeed the surface snowpack does supply most of the reactive bromine in the Arctic boundary layer, it appears to be capable of releasing reactive bromine at temperatures as high as −10 °C, particularly on the sea ice in the central and eastern Arctic Ocean. Dynamically-induced BrO column variability in the lowermost stratosphere appears to interfere with the use of satellite BrO column measurements for interpreting BrO variability in the lower troposphere but probably not to the extent of totally obscuring "BrO clouds" that originate from the surface snow/ice source of bromine in the high Arctic. A budget analysis of the simulated air-surface exchange of bromine compounds suggests that a "bromine explosion" occurs in the interstitial air of the snowpack and/or is accelerated by heterogeneous reactions on the surface of wind-blown snow in ambient air, both of which are not represented explicitly in our simple model but could have been approximated by a parameter adjustment for the yield of Br2 from the trigger.

Anomalous Variations in Atmospheric Carbon Monoxide Associated with the Tsunami

Variations in ambient atmospheric carbon monoxide(CO) observed at an inland mining site in the Indo-Gangetic plains, Jaduguda (<TEX>$22^{\circ}38'N$</TEX>, <TEX>$86^{\circ}21'E$</TEX>, 122m MSL, ~75 km away from the coast of the Bay of Bengal) during the Tsunami of 26 December 2004 were monitored. CO mixing ratio over this site was measured using a non-dispersive infrared analyzer (Monitor Europe Model 9830 B). Back trajectory analysis data obtained using NOAA Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) Model was also used for this study. Variations in CO mixing ratio at a coastal site, Thiruvananthapuram (<TEX>$8^{\circ}29'N$</TEX>, <TEX>$76^{\circ}57'E$</TEX>, located ~2 km from the Arabian Sea coast) have also been investigated using CO data retrieved from the Measurement Of Pollution In The Troposphere (MOPITT) instrument. Ground-based measurements indicated abnormal variations in CO mixing ratio at Jaduguda from 25 December 2004 evening (previous day of the Tsunami). MOPITT CO data showed an enhancement in CO mixing ratio over Thiruvananthapuram on the Tsunami day. Back trajectory analyses over Thiruvananthapuram and Jaduguda for a period of 10 days from <TEX>$21^{st}$</TEX> to <TEX>$30^{th}$</TEX> December 2004 depicted that there were unusual vertical movements of air from high altitudes from 25 December 2004 evening. CO as well as the back trajectory analyses data showed that the variations in the wind regimes and consequently wind driven transport are the most probable reasons for the enhancement in CO observed at Jaduguda and Thiruvananthapuram during the Tsunami.

Continuous isotopic composition measurements of tropospheric CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; at Jungfraujoch (3580 m a.s.l.), Switzerland: real-time observation of regional pollution events

Abstract. A quantum cascade laser based absorption spectrometer (QCLAS) is applied for the first time to perform in situ, continuous and high precision isotope ratio measurements of CO2 in the free troposphere. Time series of the three main CO2 isotopologue mixing ratios (12C16CO2, 13C16CO2 and 12C18O16O) have simultaneously been measured at one second time resolution over two years (from August 2008 to present) at the High Altitude Research Station Jungfraujoch (3580 m a.s.l., Switzerland). This work focuses on periods in February 2009 only, when sudden and pronounced enhancements in the tropospheric CO2 were observed. These short-term changes were closely correlated with variations in CO mixing ratios measured at the same site, indicating combustion related emissions as potential source. The analytical precision of 0.046‰ (at 50 s integration time) for both δ13C and δ18O and the high temporal resolution allowed the application of the Keeling plot method for source signature identification. The spatial origin of these CO2 emission sources was then determined by backward Lagrangian particle dispersion simulations.

Spatial variations of atmospheric methane concentrations in China

Methane (CH4) is regarded as one of the most important greenhouse gases due to its radiative forcing. Therefore, in running climate models, it is important to have accurate estimates of CH4 concentrations at an appropriate scale. Although great efforts have recently been undertaken to quantify atmospheric CH4 concentrations based on extensive ground-based measurements, it is still difficult to obtain the spatial variations of the CH4 volume mixing ratio (VMR) on a regional scale. This study analyses the spatial variations of CH4 VMRs in China, based on the retrieved CH4 data from Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) spectra. The results showed that the spatial distribution of CH4 VMRs presented decreasing gradients from south-east to north-east and the lowest CH4 concentrations were located on the Qinghai-Tibet Plateau. Paddy fields were the main sources of CH4 in China, as shown through spatial analysis. Natural wetlands and population also contributed to CH4 VMRs. Plant, climate and soil properties presented a strong positive influence on CH4 concentrations, which could be used to interpret the spatial variations. Stepwise multiple regression modelling results showed that temperature, normalized difference vegetation index (NDVI) and soil total nitrogen could explain 76.9% of the differences in CH4 throughout China, and the average difference between the retrieved and the modelled methane concentrations was 14 ppb.

Observations of water vapour and carbon monoxide in the Martian atmosphere with the SWC of PFS/MEX

In the history of Mars exploration its atmosphere and planetary climatology aroused particular interest. In the study of the minor gases abundance in the Martian atmosphere, water vapour became especially important, both because it is the most variable trace gas, and because it is involved in several processes characterizing the planetary atmosphere. The water vapour photolysis regulates the Martian atmosphere photochemistry, and so it is strictly related to carbon monoxide. The CO study is very important for the so-called “atmosphere stability problem”, solved by the theoretical modelling involving photochemical reactions in which the H 2O and the CO gases are main characters. The Planetary Fourier Spectrometer (PFS) on board the ESA Mars Express (MEX) mission can probe the Mars atmosphere in the infrared spectral range between 200 and 2000 cm −1 (5–50 μm) with the Long Wavelength Channel (LWC) and between 1700 and 8000 cm −1 (1.2–5.8 μm) with the Short Wavelength Channel (SWC). Although there are several H 2O and CO absorption bands in the spectral range covered by PFS, we used the 3845 cm −1 (2.6 μm) and the 4235 cm −1 (2.36 μm) bands for the analysis of water vapour and carbon monoxide, respectively, because these ranges are less affected by instrumental problems than the other ones. The gaseous concentrations are retrieved by using an algorithm developed for this purpose. The PFS/SW dataset used in this work covers more than two and a half Martian years from Ls=62° of MY 27 (orbit 634) to Ls=203° of MY 29 (orbit 6537). We measured a mean column density of water vapour of about 9.6 pr. μm and a mean mixing ratio of carbon monoxide of about 990 ppm, but with strong seasonal variations at high latitudes. The seasonal water vapour map reproduces very well the known seasonal water cycle. In the northern summer, water vapour and CO show a good anticorrelation most of the time. This behaviour is due to the carbon dioxide and water sublimation from the north polar ice cap, which dilutes non-condensable species including carbon monoxide. An analogous process takes place during the winter polar cap, but in this case the condensation of carbon dioxide and water vapour causes an increase of the concentration of non-condensable species. Finally, the results show the seasonal variation of the carbon monoxide mixing ratio with the surface pressure.

Seasonal variability of ambient NH 3, NO, NO 2 and SO 2 over Delhi

We present the diurnal and seasonal variability of ambient NH 3, NO, NO 2 and SO 2 over Delhi, India. Ambient NH 3, NO and NO 2 were measured continuously during winter, summer and autumn seasons using NH 3- and NO x-analyzer, which operates by chemiluminescence method with a higher estimation efficiency (> 90%) than the chemical trap method (reproducibility 4.7%). Prominent diurnal, day-to-day and seasonal variations of ambient mixing ratio of NH 3, NO, NO 2 and SO 2 were observed during the study period. Seasonal variation with higher mixing ratio in winter was observed for all measured trace gases except NO. Day-night variation of all measured trace gases observed was higher in winter in comparison with summer. Late morning increase in NO 2 mixing ratio might be attributed to conversion of NO to NO 2 with the interaction of O 3.

Hydrochlorofluorocarbon and hydrofluorocarbon emissions in East Asia determined by inverse modeling

Abstract. The emissions of three hydrochlorofluorocarbons, HCFC-22 (CHClF2), HCFC-141b (CH3CCl2F) and HCFC-142b (CH3CClF2) and three hydrofluorocarbons, HFC-23 (CHF3), HFC-134a (CH2FCF3) and HFC-152a (CH3CHF2) from four East Asian countries and the Taiwan region for the year 2008 are determined by inverse modeling. The inverse modeling is based on in-situ measurements of these halocarbons at the Japanese stations Cape Ochi-ishi and Hateruma, the Chinese station Shangdianzi and the South Korean station Gosan. For every station and every 3 h, 20-day backward calculations were made with the Lagrangian particle dispersion model FLEXPART. The model output, the measurement data, bottom-up emission information and corresponding uncertainties were fed into an inversion algorithm to determine the regional emission fluxes. The model captures the observed variation of halocarbon mixing ratios very well for the two Japanese stations but has difficulties explaining the large observed variability at Shangdianzi, which is partly caused by small-scale transport from Beijing that is not adequately captured by the model. Based on HFC-23 measurements, the inversion algorithm could successfully identify the locations of factories known to produce HCFC-22 and emit HFC-23 as an unintentional byproduct. This lends substantial credibility to the inversion method. We report national emissions for China, North Korea, South Korea and Japan, as well as emissions for the Taiwan region. Halocarbon emissions in China are much larger than the emissions in the other countries together and contribute a substantial fraction to the global emissions. Our estimates of Chinese emissions for the year 2008 are 65.3±6.6 kt/yr for HCFC-22 (17% of global emissions extrapolated from Montzka et al., 2009), 12.1±1.6 kt/yr for HCFC-141b (22%), 7.3±0.7 kt/yr for HCFC-142b (17%), 6.2±0.7 kt/yr for HFC-23 (&gt;50%), 12.9±1.7 kt/yr for HFC-134a (9% of global emissions estimated from Velders et al., 2009) and 3.4±0.5 kt/yr for HFC-152a (7%).

HCCI機関における二種燃料を用いた層状給気による燃焼圧力上昇率の低減効果(熱工学,内燃機関,動力など)

Operating range of HCCI engines is limited by an excessive pressure rise rate (PRR) in high load region resulting in engine knock. Dispersing auto-ignition timing at each local area in the combustion chamber and retarding combustion phasing (CA50) are main methods of decreasing the excessive PRR. Changing mixing ratio of two fuels which have different auto-ignition characteristics leads to the change of combustion phasing. The objective of this study was to investigate the effect of making the variation of mixing ratio in the mixture to change the combustion phasing at each local area in the combustion chamber on reducing PRR. The test fuels were DME and n=Butane which both have LTHR and HTHR during HCCI combustion. In addition to in-cylinder gas pressure measurement, in order to assess the combustion at each local area, chemiluminescence imaging and numerical analysis with multi-zones modeling were used. Maximum PRR changes depending on mixing condition of DME and n-Butane. When DME is stratified and n-Butane is distributed uniformly in the combustion chamber (Case 3), maximum PRR becomes lowest. In Case 3, the appearance timing of chemiluminescence at each local area is dispersed and the duration of chemiluminescence is longer than in Case 1 (DME and n-Butane are both distributed uniformly). By numerical analysis, it is found that the temperature distribution and difference of HTHR start temperature makes difference of HTHR start timing in each zone.

Observations of carbon monoxide mixing ratios at a mountain site in central Taiwan during the Asian biomass burning season

Carbon monoxide (CO) mixing ratios were observed from 30 January to 7 April 2008 at Mt. Lulin (23.51°N, 120.92°E, 2862 m asl) in central Taiwan to investigate characteristics of CO during biomass burning periods. During the sampling campaign, the average mixing ratio of CO was 234 ± 63 ppb with higher levels observed in March. The elevated CO in March can, on the basis of backward trajectories and satellite fire spots analyses, possibly be attributed to biomass burning activities in the Asian continent. Significant diurnal variations of CO mixing ratios were observed at the remote site. The higher CO levels in the afternoon were influenced by the transport of boundary layer pollution to the site during daytime upslope flow. Backward trajectory analysis showed that air masses mainly originated from India (ID), the Indochina Peninsula (IP) and South Coastal China (SC), which together accounted for 85% of the total trajectories. Higher mixing ratios of CO were found in the ID, IP, and SC categories, indicating significant impacts of anthropogenic emissions on the Pacific region. Furthermore, the air parcels were divided into two categories, those that passed over the fire regions and those that did not. The result showed that the average difference of CO levels between the two categories was approximately 79 ppb, suggesting that Asian biomass burning plays an important role in CO levels at this remote site during the springtime.

Dynamical modes associated with the Antarctic ozone hole

Abstract. Generalized Maximum Covariance Analysis (GMCA) has been developed and applied to diagnosing the dynamical modes associated with variations in the Antarctic spring ozone hole. GMCA is used to identify the most important patterns of co-variability between interannual ozone mixing ratio variations in the Antarctic region and temperature, zonal, meridional and vertical velocities between 100 and 10 hPa in the same region. The most important two pairs of GMCA time coefficients show large year-to-year variations and trends, which are connected with the growth of the Antarctic Ozone Hole and the increase of ozone depleting substances. The associated spatial patterns of ozone variations may be characterized as being quasi-symmetric and asymmetric about the pole. These patterns of ozone variations are associated with comparable patterns of variations of temperature and winds through most of the vertical domain. The year 2000 is shown to be dominated by the asymmetric mode, whereas the adjacent year 2001 is dominated by the quasi-symmetric mode. A case study, focusing on the asymmetric differences between these two years, shows the magnitude of the ozone mixing ratio, temperature and zonal wind differences to be in the range of 2 e–6 kg/kg, 10°C and 10 m/s, respectively. Budget calculations show that transport processes contribute substantially to the ozone and temperature changes in the middle stratosphere over the Antarctic continent. However, both radiative and chemical processes also play important roles in the changes.

Observations of NO&amp;lt;sub&amp;gt;x&amp;lt;/sub&amp;gt;, ΣPNs, ΣANs, and HNO&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt; at a Rural Site in the California Sierra Nevada Mountains: summertime diurnal cycles

Abstract. Observations of NO, NO2, total peroxy nitrates (ΣPNs), total alkyl nitrates (ΣANs), HNO3, CO, O3, and meteorological parameters were obtained from October 2000 through February 2002 at 1315 m a.s.l., 38.9° N, 120.6° W on Sierra Pacific Industries land, adjacent to the University of California Blodgett Forest Research Station (UC-BFRS). We describe the data set with emphasis on the diurnal cycles during summertime 2001. We show that transport of the Sacramento urban plume is a primary factor responsible for diurnal variation in total reactive nitrogen mixing ratios as well as in NOx, ΣPNs and ΣANs, all of which exhibit a late afternoon/early evening peak. In contrast, HNO3 has a peak just after local noon indicating that HNO3 is in near steady state during the day with production due to photochemistry and removal by deposition and mixing with the background free troposphere. Boundary layer dynamics influence mixing ratios of all species in the early morning. Analysis of the morning feature suggests that higher mixing ratios of NOx and HNO3 persist in the residual layer than in the nocturnal boundary layer indicating the presence of nocturnal sinks of both species. Nighttime observations also indicate large HNO3 and ΣANs production through oxidation of alkenes by NO3.

Stability of irinotecan-loaded drug eluting beads (DC BeadTM) used for transarterial chemoembolization

The aim of this study was to determine the loading efficiency, physicochemical stability, and release of irinotecan-loaded DC Beads (bead size 100-300 microm, 300-500 microm) before and after mixing with nonionic contrast medium (Accupaque 300, Imeron 300, Ultravist 300) during a prolonged period of time (28 days) when stored at room temperature or refrigerated. DC Beads were loaded with 50 mg irinotecan (Campto) per milliliter beads in a 2 h loading period. Drug loading efficiency and stability were determined by measuring the irinotecan concentration in the excess solution. A free-flowing in vitro elution method for a period of 2 h and phosphate buffered solution (PBS, pH 7.2) as elution medium were used to analyze the integrity of the irinotecan-loaded. Stability of irinotecan-loaded beads after mixing with an equal volume of three different nonionic contrast agents was determined by measuring irinotecan concentrations in the excess solutions. Vials with loaded beads were stored protected from light at room temperature. Mixtures with contrast media were stored protected from light under refrigeration (2-8 degrees C). Samples were taken periodically over a 4 week period (day 0, 1, 3, 7 and 28). A reversed phase HPLC assay with ultraviolet detection was utilized to analyze the concentration and purity of irinotecan. The loading procedure of DC Beads with irinotecan drug solution resulted in a loading percentage of 96% (bead size 100-300 microm) independent of the storage time. No differences in loading levels and no irinotecan degradation products were observed over the period of 28 days, while the test vials were stored light protected at room temperature. Integrity of loaded irinotecan was also given over that same period of time according to the purity and concentration of irinotecan measured after intentional elution with PBS. Mixing of irinotecan-loaded beads (bead size 100-300 microm, 300-500 microm) with nonionic contrast media decreased the irinotecan loading efficiency by approximately 5-10% during a maximum period of 24 h. However, no further elution or degradation was observed during a 4-week period when stored protected from light under refrigeration. Irinotecan-loaded DC Beads are shown to have adequate physicochemical stability over a period of at least 28 days when stored light protected at room temperature. Due to concerns of microbiological overgrowth refrigeration should always be considered. The preparation of admixtures of irinotecan-loaded beads with contrast medium in centralized cytotoxic preparation units is not recommended, because of rapid elution of 5-10% of irinotecan from the loaded beads. Furthermore, physicians see no advantages of admixtures due to the wide variation of mixing ratios of drug-loaded beads with contrast medium. In addition varying volumes of 0.9% sodium chloride solution are to be admixed during the chemoembolization procedure.

Volatile organic compounds measured in summer in Beijing and their role in ground‐level ozone formation

Beijing has long suffered from serious ground‐level ozone pollution, and volatile organic compounds (VOCs) play a key role in ozone formation. To understand the chemical speciation of VOCs in Beijing, nonmethane hydrocarbons (NMHCs) and oxygenated VOCs (OVOCs) were measured in summer in Beijing and nearby provinces (VOCs in this work means NMHCs+OVOCs). A variation of VOC mixing ratios and chemical speciation from 2004 to 2006 was observed at an urban site in Beijing. The typical VOC species, e.g., propane, propene, and toluene, had comparable or lower mixing ratios than levels found in other cities that previously hosted the Olympic Games, while the mixing ratios for isoprene were higher. The chemical compositions of VOCs within Beijing were heavily influenced by vehicular emissions and differed from those obtained in Tianjin and Hebei Province. OVOCs were an important component, accounting for 54% and 37% in the VOC mixing ratio in 2005 and 2006, respectively, and about 40% of the OH loss rates. The main reactive VOC compounds were aldehydes and alkenes. By using isoprene chemistry and the ratio of ethylbenzene to mp‐xylene, the initial mixing ratios of VOCs were estimated. The VOCs had similar variation patterns to ambient ozone and peroxyacetyl nitrate (PAN) concentrations. The correlation between daily maximum ozone concentrations and initial VOCs revealed that ozone formation was sensitive to VOCs for both urban (Peking University, PKU) and rural (Yufa) sites. A reduction in NOx would lead to a decrease in ozone at Yufa, but would cause increased ozone at the PKU site.