入江 仁士

Since January 2017 continuous multi-axis differential optical absorption spectroscopy (MAX-DOAS) observations have been performed for the first time at Pantnagar (29.03 degrees N, 79.47 degrees E), a semi-urban site located in the Indo-Gangetic Plain region in India. Here we report the formaldehyde (HCHO), glyoxal (CHOCHO), and nitrogen dioxide (NO2) concentrations for the lowest layer (0-1 km) of the retrieved vertical profiles. The ratio of CHOCHO to HCHO concentrations (R-GF), an important tracer indicative of changes in volatile organic compound emissions was estimated. During spring and autumn enhanced concentrations of HCHO and CHOCHO were observed wider the influence of biomass burning. The mean R-GF for the whole observation period (January-November) in Pantnagar was estimated to be 0.029 +/- 0.006. Comparing with similar MAX-DOAS observations in central Thailand and reported literature values, we found that the R-GF tends to be < similar to 0.04 under the influence of biomass burning and/or anthropogenic emissions.

Himawari-8, a next-generation geostationary meteorological satellite, was launched on 7 October 2014 and became operational on 7 July 2015. The advanced imager on board Himawari-8 is equipped with 16 observational bands (including three visible and three near-infrared bands) that enable retrieval of full-disk aerosol optical properties at 10min intervals from geostationary (GEO) orbit. Here we show the first application of aerosol optical properties (AOPs) derived from Himawari-8 data to aerosol data assimilation. Validation of the assimilation experiment by comparison with independent observations demonstrated successful modeling of continental pollution that was not predicted by simulation without assimilation and reduced overestimates of dust front concentrations. These promising results suggest that AOPs derived from Himawari-8/9 and other planned GEO satellites will considerably improve forecasts of air quality, inverse modeling of emissions, and aerosol reanalysis through assimilation techniques.

Asian continental outflow air masses reach western Japan in the springtime, carrying high levels of ozone produced over the Asian continent, and facilitating in-situ production. In this study, in-situ production was highlighted; the rate and limiting factors of net ozone production were diagnosed at Fukue Island, a remote island west of Japan, on 17 days during May-June 2009, when the continental outflow air mass arrived, using an observation-based modeling approach. The average ozone production was estimated to be 6.8 ppb per day. Information on the chemical status of the arriving air mass is important, because it affects how further ozone production in the air mass occurs after precursor addition from Japanese domestic emissions. The main limiting factor of ozone production for such air masses was usually nitrogen oxides (NOx), suggesting that domestic NOx emission control is important in reducing further ozone production. Volatile organic compounds (VOCs) also increased the ozone production rate, and occasionally (14% of time) became the dominant controlling factor. This analysis implies that the VOC reduction legislation recently enacted by the Japanese government should be effective. VOC-limited conditions occurred particularly when the air mass traveled within 6. 8 h, via the Korean Peninsula. The uncertainty in the radical chemistry mechanism governing ozone production had a non-negligible impact, but the main conclusion relevant to policy was not altered. When chain termination was augmented by HO2 + NO/NO2 reactions in the presence of H2O and by heterogeneous loss of HO2 on aerosol particle surfaces, as recently verified or hypothesized, the daily ozone production rate decreased by up to 24%, and the fraction of hours when the VOC-limited condition occurred varied from 14% to 13-26%.

SKYNET and Aerosol Robotic Network (AERONET) retrieved aerosol single scattering albedo (SSA) values of four sites, Chiba (Japan), Pune (India), Valencia (Spain), and Seoul (Korea), were compared to understand the factors behind often noted large SSA differences between them. SKYNET and AERONET algorithms are found to produce nearly same SSAs for similarity in input data, suggesting that SSA differences between them are primarily due to quality of input data due to different calibration and/or observation protocols as well as difference in quality assurance criteria. The most plausible reason for high SSAs in SKYNET is found to be underestimated calibration constant for sky radiance (). The disk scan method (scan area: 1 degrees x1 degrees area of solar disk) of SKYNET is noted to produce stable wavelength-dependent values in comparison to those determined from the integrating sphere used by AERONET to calibrate sky radiance. Aerosol optical thickness (AOT) difference between them can be the next important factor for their SSA difference, if AOTs between them are not consistent. Inconsistent values of surface albedo while analyzing data of SKYNET and AERONET can also bring SSA difference between them, but the effect of surface albedo is secondary. The aerosol nonsphericity effect is found to be less important for SSA difference between these two networks.

Firstly, this study discusses long-term observations of aerosol chararacteristics over four typical SKYNET sites (Chiba, Fukuejima, Miyakojima, and Hedo) within Japan to clarify the seasonal dependent characteristics of aerosols of different origins and their impacts on atmospheric heat budget. Optically thicker aerosols with significant amount of coarse-mode aerosols are found in the spring season. The aerosol radiative forcings at the surface and top of the atmosphere in the spring season can be roughly two times of the values in the winter season. Secondly, we discuss the optical characteristics of clouds obtained from the sky radiometer of SKYNET and Moderate Resolution Imaging Spectroradiometer (MODIS). Our analysis suggests that MODIS cloud optical depth (COD) may be underestimated, which in turn may lead to overestimate calculated shortwave flux.

Long-term (2005-2015) tropospheric nitrogen dioxide (NO2) column data recorded by the satellite-borne Ozone Monitoring Instrument (OMI) in East Asia were analyzed to investigate annual trends on an national basis and their potential causes. We found an evident decrease of 6% year(-1) in the NO2 level over China after 2011. The grid-basis trend analysis implies that the rapid decrease occurred on a provincial or larger spatial scale and was likely due to a nationwide action such as the widespread use of denitrification units. In Japan and South Korea, a turnaround indicating an increase was observed after 2013 and 2012, respectively. As a consequence, the tropospheric NO2 pollution level in East Asia was found to be recovered to the 5-year-ago level in 2015.

A first direct intercomparison of aerosol vertical profiles from Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) observations, performed during the Cabauw Intercomparison Campaign of Nitrogen Dioxide measuring Instruments (CINDI) in summer 2009, is presented. Five out of 14 participants of the CINDI campaign reported aerosol extinction profiles and aerosol optical thickness (AOT) as deduced from observations of differential slant column densities of the oxygen collision complex (O-4) at different elevation angles. Aerosol extinction vertical profiles and AOT are compared to backscatter profiles from a ceilometer instrument and to sun photometer measurements, respectively. Furthermore, the near-surface aerosol extinction coefficient is compared to in situ measurements of a humidity-controlled nephelometer and dry aerosol absorption measurements. The participants of this intercomparison exercise use different approaches for the retrieval of aerosol information, including the retrieval of the full vertical profile using optimal estimation and a parametrised approach with a prescribed profile shape. Despite these large conceptual differences, and also differences in the wavelength of the observed O-4 absorption band, good agreement in terms of the vertical structure of aerosols within the boundary layer is achieved between the aerosol extinction profiles retrieved by the different groups and the backscatter profiles observed by the ceilometer instrument. AOTs from MAX-DOAS and sun photometer show a good correlation (R &gt; 0.8), but all participants systematically underestimate the AOT. Substantial differences between the near-surface aerosol extinction from MAX-DOAS and from the humidified nephelometer remain largely unresolved.

An investigation into the diurnal characteristics of vertical formaldehyde (HCHO) profiles was conducted based on multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements in Beijing during the CAREBEIJING campaign, covering a month-long period through August and September 2006. Vertical HCHO profiles were retrieved based on a combined differential optical absorption spectroscopy (DOAS) technique and an optimal estimation method (OEM). The HCHO volume-mixing ratio (VMR) was found to be highest in the layer from the surface up to an altitude of 1 km and to decrease with altitude above this layer. In all retrieved profiles, HCHO was not detected in the layer from 3-4 km. Over the diurnal cycle, the HCHO VMR values were generally highest at 15:00 local time (LT) and were lower in the morning and late afternoon. The mean HCHO VMRs were 6.17, 1.82, and 0.80 ppbv for the 0-1, 1-2, and 2-3-km layers, respectively, at 15:00 LT, whereas they were 3.54 (4.79), 1.06 (1.43), and 0.46 (0.63) ppbv for the 0-1, 1-2, and 2-3-km layers, respectively, at 09:00 (17:00) LT. The HCHO VMRs reached their highest values at 15:00 LT on August 19, which were 17.71, 5.20, and 2.31 ppbv for the 0-1, 1-2, and 2-3-km layers, respectively. This diurnal pattern implies that the photo-oxidation of volatile organic compounds (VOCs) was most active at 15:00 LT for several days during the campaign period. In a comparison of the derived HCHO VCDs with those obtained from the Ozone Monitoring Instrument (OMI) measurements, the HCHO vertical column density (VCD) values obtained from the OMI measurements tend to be smaller than those from the MAX-DOAS.

Distributions and optical characteristics of aerosols were continuously observed with a polarization-sensitive (532 nm), Mie-scattering (532 and 1064 nm) and Raman-scattering (607 nm) lidar and a sky radiometer in Phimai, Thailand. Polarization lidar measurements indicated that high concentration plumes of spherical aerosols considered as biomass burning smoke were often observed in the dry season. Plumes of non-spherical aerosols considered as long-range transported soil dust from Africa, the Middle East, or Northeast Asia were occasionally observed. Furthermore, low-concentration non-spherical aerosols were almost always observed in the atmospheric mixing layer. Extinction coefficient profiles of spherical aerosols and non-spherical dust exhibited different diurnal variations, and spherical aerosols including smoke were distributed in higher altitudes in the mixing layer and residual layer. The difference can be explained by hygroscopic growth of smoke particles and buoyancy of the smoke. Analysis of seasonal variations of optical properties derived from the Raman lidar and the sky radiometer confirmed that the lidar ratio, aerosol optical depth, and Angstrom exponent were higher in the dry season (October-May) and lower in the wet season (June-September). The single scattering albedo was lower in the dry season. These seasonal variations are explained by frequent biomass burning in the dry season consistent with previous studies in Southeast Asian region. At the same time, the present work confirmed that soil dust was a major aerosol component in Phimai, Thailand.

This paper presents a distribution automation system (DAS) for service restoration in the distribution network with photovoltaic (PV) generator systems, which are disconnected simultaneously after a fault and subsequently reconnected after service restoration. Because the reverse power flow of PVs affects voltage in the distribution system, voltage dips and surges occur during the service restoration. However, current DAS do not control voltage regulators such as an on-load tap changer (OLTC) and step voltage regulators (SVRs) during the service restoration. The proposed DAS estimates the voltage in a distribution network considering the simultaneous disconnection of PVs by performing power flow calculations, and it controls the tap position of OLTC and/or SVRs according to the predicted voltage deviation. The voltage after the disconnection of PVs is calculated by estimating the PV output utilizing square kilometer solar radiation data calculated using satellite image data in real time.

Continuous NO2 profile observations have been made using ground-based Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) at Fukuoka (33.55 degrees N, 130.36 degrees E), an urban area in Japan. Throughout the year, NO2 variations measured by MAX-DOAS (0-100 m) are in good agreement with in situ surface NO2 measurements on several-day, week-to-week, and seasonal timescales. We investigated the spatiotemporal inhomogeneity in NO2 over Fukuoka by observing at two azimuth angles: the Tenjin (towards the city center) and Itoshima (away from the city center) directions. In terms of diurnal variations, NO2 in both directions show clear morning maxima, on account of local emissions in the morning and the development of a boundary layer. The concentrations in the early morning are nearly the same in both directions, but they are higher in the Tenjin direction during most of the daytime on average. Variability in both directions, as well as spatial inhomogeneity, is large during most of the daytime except for in the morning. The diurnal maximum for 0-1 km between 10 and 13 LT is sometimes observed in the Tenjin direction; in some cases, 1 h after this maximum, a maximum is also observed in the Itoshima direction. The NO2 maxima for the upper level (1-2 km) in both directions are also delayed from the maximum in the Tenjin direction for 0-1 km. Analysis of the surface wind field indicates that the NO2 inhomogeneity is strongly related to vertical/horizontal transport of high concentrations of NO2 from the city center, and to horizontal transport of low concentrations from the ocean via a land sea breeze. Three-dimensional continuous observations by MAX-DOAS are potentially a powerful tool for increasing our understanding of pollutant transport and mixing in urban areas. (C) 2014 Elsevier Ltd. All rights reserved.

Coincident aerosol observations of multi-axis differential optical absorption spectroscopy (MAX-DOAS), cavity ring-down spectroscopy (CRDS), lidar, and sky radiometer were conducted in Tsukuba, Japan, on 5-18 October 2010. MAX-DOAS aerosol retrieval (for aerosol extinction coefficient and aerosol optical depth at 476 nm) was evaluated from the viewpoint of the need for a correction factor for oxygen collision complexes (O-4 or O-2-O-2 absorption. The present study strongly supports this need, as systematic residuals at relatively high elevation angles (20 and 30 degrees) were evident in MAX-DOAS profile retrievals conducted without the correction. However, adopting a single number for the correction factor (f(O4) = 1.25) for all of the elevation angles led to systematic overestimation of near-surface aerosol extinction coefficients, as reported in the literature. To achieve agreement with all three observations, we limited the set of elevation angles to &lt;= 10 degrees and adopted an elevation-angle-dependent correction factor for practical profile retrievals with scattered light observations by a groundbased MAX-DOAS. With these modifications, we expect to minimize the possible effects of temperature-dependent O-4 absorption cross section and uncertainty in DOAS fit on an aerosol profile retrieval, although more efforts are encouraged to quantitatively identify a physical explanation for the need of a correction factor.

NO2 vertical column densities (VCDs) over East Asia in June and December 2007 were simulated by the Community Multi-scale Air Quality (CMAQ) version 4.7.1 using an updated and more elaborate version of the Regional Emission Inventory in Asia (REAS) version 2. The modeling system could reasonably capture observed spatiotemporal changes of NO2 VCDs by satellite sensors, the Global Ozone Monitoring Experiment-2 (GOME-2), the Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY), and the Ozone Monitoring Instrument (OMI), even at the coarsest horizontal resolution of 80 km. The CMAQ simulations were performed in a sequence of three horizontal resolutions (80 km, 40 km, and 20 km) for June and December 2007 to investigate the influence of changes of horizontal resolution on the obtained NO2 VCDs. CMAQ-simulated NO2 VCDs generally increased with improvements in resolution from 80 km to 40 km and then to 20 km. Increases in the CMAQ-simulated NO2 VCDs were greater for the change from 80 km to 40 km than for those from 40 km and 20 km, in which the increases of NO2 VCDs due to the improvement of horizontal resolution were approached convergence at the horizontal resolution of approximately 20 km. Conversely, no clear convergences in NO2 VCDs changes were found at near Tokyo and over the East China Sea. The biases of the NO2 VCDs simulated at a resolution of 20 km against the satellite retrievals were ~36% near Beijing (CHN1) and ~78% near Shanghai (CHN2) in summer; these errors were found to be comparable to the horizontal resolution-dependent errors, which were 18-25% at CHN1 and 44-58% at CHN2 from 80 km to 40 km. Conversely, the influence of changes of horizontal resolution in winter was relatively less compared to that in summer. NO2 VCDs over East Asia in June and December 2007 were simulated using CMAQ version 4.7.1 and REAS version 2. The modeling system could reasonably capture observed spatiotemporal changes of NO2 VCDs by satellite sensors. The CMAQ simulations were performed in a sequence of three horizontal resolutions, 80, 40, and 20 km, to investigate the influence of changes of horizontal resolution on the obtained NO2 VCDs. The results suggested that the influence of changes of horizontal resolution was larger in summer compared to that in winter. The magnitude of the influence was comparable to the biases of the NO2 VCDs simulated at a resolution of 20 km against the satellite retrievals. © 2014 Copyright © 2014 A&WMA.

Satellite observations of the tropospheric NO2 vertical column density (VCD) are closely correlated to, and thus can be used to estimate, surface NOx emissions. In this study, the NO2 VCD simulated by a regional chemical transport model with emissions data from the updated Regional Emission inventory in ASia (REAS) version 2.1 were validated through comparison with multisatellite observations during the period 2000-2010. Rapid growth in NO2 VCD (similar to 11% year(-1)) driven by the expansion of anthropogenic NOx emissions was identified above the central eastern China (CEC) region, except for the period during the economic downturn. In contrast, slightly decreasing trends (similar to 2% year(-1)) were identified above Japan accompanied by a decline in anthropogenic emissions. To systematically compare the modeled NO2 VCD, we estimated sampling bias and the effect of applying the averaging kernel information, with particular focus on the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) data. Using the updated REAS, the modeled NO2 VCD reasonably reproduced annual trends observed by multisatellites, suggesting that the rate of increase of NOx emissions estimated by the updated REAS inventory would be robust. Province-scale revision of emissions above CEC is needed to further refine emission inventories. Based on the close linear relationship between modeled and observed NO2 VCD and anthropogenic NOx emissions, NOx emissions in 2009 and 2010, which were not covered by the updated REAS inventory, were estimated. NOx emissions from anthropogenic sources in China in 2009 and 2010 were determined to be 26.4 and 28.5 Tg year(-1), respectively, indicating that NOx emissions increased more than twofold between 2000 and 2010. This increase reflected the strong growth of anthropogenic emissions in China following the rapid recovery from the economic downturn from late 2008 until mid-2009. Our method consists of simple estimations from satellite observations and provides results that are consistent with the most recent inventory of emissions data for China.

We investigated the effect of surface reflectance anisotropy, bidirectional reflectance distribution function (BRDF), on satellite retrievals of tropospheric NO2. We assume the geometry of geostationary measurements over Tokyo, which is one of the worst air-polluted regions in East Asia. We calculated air mass factors (AMF) and box AMFs (BAMF) for tropospheric NO2 to evaluate the effect of BRDF by using the radiative transfer model SCIATRAN. To model the BRDF effect, we utilized the Moderate Resolution Imaging Spectroradiometer (MODIS) products (MOD43B1 and MOD43B2), which provide three coefficients to express the RossThick-LiSparse reciprocal model, a semi-empirical and kernel-based model of BRDF. Because BRDF depends on the land cover type, we also utilized the High Resolution Land-Use and Land-Cover Map of the Advanced Land Observing Satellite (ALOS)/Advanced Visible and Near Infrared Radiometer type 2 (AVNIR-2), which classifies the ground pixels over Tokyo into six main types: water, urban, paddy, crop, deciduous forest, and evergreen forest. We first develop an empirical model of the three BRDF coefficients for each land cover type over Tokyo and then apply the model to the calculation of land-cover-type-dependent AMFs and BAMFs. Results show that the variability of AMF among the land types is up to several tens of percent, and if we neglect the reflectance anisotropy, the difference with AMFs based on BRDF reaches 10% or more. The evaluation of the BAMFs calculated shows that not considering BRDF will cause large errors if the concentration of NO2 is high close to the surface, although the importance of BRDF for AMFs decreases for large aerosol optical depth (AOD).

We assess the standard operational nitrogen dioxide (NO2) data product (OMNO2, version 2.1) retrieved from the Ozone Monitoring Instrument (OMI) onboard NASA's Aura satellite using a combination of aircraft and surface in situ measurements as well as ground-based column measurements at several locations and a bottom-up NOx emission inventory over the continental US. Despite considerable sampling differences, NO2 vertical column densities from OMI are modestly correlated (r = 0.3-0.8) with in situ measurements of tropospheric NO2 from aircraft, ground-based observations of NO2 columns from MAX-DOAS and Pandora instruments, in situ surface NO2 measurements from photolytic converter instruments, and a bottom-up NOx emission inventory. Overall, OMI retrievals tend to be lower in urban regions and higher in remote areas, but generally agree with other measurements to within +/- 20%. No consistent seasonal bias is evident. Contrasting results between different data sets reveal complexities behind NO2 validation. Since validation data sets are scarce and are limited in space and time, validation of the global product is still limited in scope by spatial and temporal coverage and retrieval conditions. Monthly mean vertical NO2 profile shapes from the Global Modeling Initiative (GMI) chemistry-transport model (CTM) used in the OMI retrievals are highly consistent with in situ aircraft measurements, but these measured profiles exhibit considerable day-to-day variation, affecting the retrieved daily NO2 columns by up to 40 %. This assessment of OMI tropospheric NO2 columns, together with the comparison of OMI-retrieved and model-simulated NO2 columns, could offer diagnostic evaluation of the model.

We conducted long-term network observations using standardized Multi-Axis Differential optical absorption spectroscopy (MAX-DOAS) instruments in Russia and ASia (MADRAS) from 2007 onwards and made the first synthetic data analysis. At seven locations (Cape Hedo, Fukue and Yokosuka in Japan, Hefei in China, Gwangju in Korea, and Tomsk and Zvenigorod in Russia) with different levels of pollution, we obtained 80 927 retrievals of tropospheric NO2 vertical column density (TropoNO2VCD) and aerosol optical depth (AOD). In the technique, the optimal estimation of the TropoNO2VCD and its profile was performed using aerosol information derived from O-4 absorbances simultaneously observed at 460-490 nm. This large data set was used to analyze NO2 climatology systematically, including temporal variations from the seasonal to the diurnal scale. The results were compared with Ozone Monitoring Instrument (OMI) satellite observations and global model simulations. Two NO2 retrievals of OMI satellite data (NASA ver. 2.1 and Dutch OMI NO2 (DOMINO) ver. 2.0) generally showed close correlations with those derived from MAX-DOAS observations, but had low biases of up to similar to 50 %. The bias was distinct when NO2 was abundantly present near the surface and when the AOD was high, suggesting a possibility of incomplete accounting of NO2 near the surface under relatively high aerosol conditions for the satellite observations. Except for constant biases, the satellite observations showed nearly perfect seasonal agreement with MAX-DOAS observations, suggesting that the analysis of seasonal features of the satellite data were robust. Weekend reduction in the TropoNO(2)VCD found at Yokosuka and Gwangju was absent at Hefei, implying that the major sources had different weekly variation patterns. While the TropoNO2VCD generally decreased during the midday hours, it increased exceptionally at urban/suburban locations (Yokosuka, Gwangju, and Hefei) during winter. A global chemical transport model, MIROC-ESM-CHEM (Model for Interdisciplinary Research on Climate-Earth System Model-Chemistry), was validated for the first time with respect to background NO2 column densities during summer at Cape Hedo and Fukue in the clean marine atmosphere.

2000 <tt>年から</tt>2012 <tt>年までの東アジア域の窒素酸化物質</tt>NOx <tt>の排出量の増加トレンドを</tt>GEOS Chem <tt>化学輸送モデル、４つの環境監視衛星からの</tt>NO₂<tt>カラム濃度計測、最新のアジア域大気汚染物質排出データベース</tt>REAS Ver. 2.1 <tt>を用いて調べた。モデル計算は全球格子（</tt>2˚×2.5˚<tt>）にアジア域高解像度格子</tt> (0.5 ˚×0.667˚) <tt>をネストし、</tt>NO₂<tt>の大気中の寿命に関わる化学反応過程を修正して行った。衛星計測による</tt>CEC <tt>の</tt>NO₂<tt>の対流圏カラム濃度は</tt>2000 – 2005 <tt>年に年率で</tt> 10<tt>％で増加していた。</tt>REAS Ver 2.1 <tt>を利用した</tt>GEOS Chem <tt>モデル解析は</tt>2000 <tt>–</tt> 2008 <tt>年の変動傾向をよく再現していた。窒素酸化物間の組成の季節変動と</tt>NOx <tt>排出量の関係を解析し、</tt>NO₂<tt>カラム濃度と</tt>NOx <tt>排出量の間に高い線形関係が確認され、衛星から計測できる</tt>NO₂<tt>カラム濃度が</tt>NOx <tt>排出量のよいインデックスになることを示した。この結果をもとに、衛星計測の結果から</tt>2009 <tt>年以降の</tt>NOx <tt>排出量を逆推定する回帰式を示した。全窒素化合物の</tt>CEC <tt>領域の収支解析を行った。暖候期には</tt>CEC <tt>で排出された</tt>NOx <tt>の</tt>60% <tt>強が</tt>CEC <tt>領域内に乾性•湿性沈着で除去されるが、寒候期には域外への水平輸送の寄与が約</tt>2/3 <tt>に達することを示した。</tt>

We present intercomparison results for formaldehyde (HCHO) slant column measurements performed during the Cabauw Intercomparison campaign of Nitrogen Dioxide measuring Instruments (CINDI) that took place in Cabauw, the Netherlands, in summer 2009. During two months, nine atmospheric research groups simultaneously operated MAX-DOAS (MultiAXis Differential Optical Absorption Spectroscopy) instruments of various designs to record UV-visible spectra of scattered sunlight at different elevation angles that were analysed using common retrieval settings. The resulting HCHO data set was found to be highly consistent, the mean difference between instruments generally not exceeding 15 % or 7.5 x 10(15) molec cm(-2), for all viewing elevation angles. Furthermore, a sensitivity analysis was performed to investigate the uncertainties in the HCHO slant column retrieval when varying key input parameters such as the molecular absorption cross sections, correction terms for the Ring effect or the width and position of the fitting interval. This study led to the identification of potentially important sources of errors associated with cross-correlation effects involving the Ring effect, O-4, HCHO and BrO cross sections and the DOAS closure polynomial. As a result, a set of updated recommendations was formulated for HCHO slant column retrieval in the 336.5-359 nm wavelength range. To conclude, an error budget is proposed which distinguishes between systematic and random uncertainties. The total systematic error is estimated to be of the order of 20 % and is dominated by uncertainties in absorption cross sections and related spectral cross-correlation effects. For a typical integration time of one minute, random uncertainties range between 5 and 30 %, depending on the noise level of individual instruments.

We conducted an intensive field campaign at the summit of Mt. Tai (36.26 degrees N, 117.11 degrees E, 1534m above sea level), Shandong Province, located at the center of central East China, during the period 28 May to 30 June 2006, to study seasonal maxima of regional air pollution with respect to ozone (O-3) and aerosols. The specific objectives, campaign design, and major findings are summarized. High concentrations of O-3 and its precursors, and aerosols, were detected and studied in the context of annual variations. Most importantly, we identified that emissions from regional-scale open crop residue burning after the harvesting of winter wheat, together with photochemical aging, strongly increased the concentrations of O-3, aerosols, and primary pollutants in this month of year. Studies of in situ photochemical activity, regional source attribution of O-3, O-3-aerosol interactions, validation of satellite observations of tropospheric NO2, behaviors of volatile organic compounds and organic/inorganic aerosol species, loss rates of black carbon (BC), and instrument inter-comparisons are also summarized. The observed BC levels must have a strong impact on the regional climate.

To illuminate the issue of trans-boundary O-3 pollution and regional O-3 reduction policies in East Asia, we have investigated the East Asian ozone (O-3) response to perturbations caused by Chinese anthropogenic emissions using the Community Multiscale Air Quality (CMAQ) model, a regional chemical transport model. The O-3 responses have been examined for the range between -100 and +100% changes from the Chinese emissions level in 2004 in 10% intervals. We have found that springtime and summertime O-3 responses both at the source and at the downwind areas can be regarded as linear over the range between -30 and +100% changes from the current emissions level. We therefore suggest that the perturbation between -30 and +100% is sufficiently small to avoid nonlinear chemical influence on O-3 formation in a model experiment to investigate East Asian scale O-3 source-receptor relationships. On the other hand, the O-3 response is strongly nonlinear in April at Hong Kong, where the current NMVOCs/NOx ratio is low and the O-3 production regime is easily moved to the NMVOCs sensitive region. The O-3 responses to the NOx emission changes have been investigated using surface O-3 concentrations at remote Japanese sites and tropospheric NO2 vertical column density (NO2 VCD) over central east China both with observations and with model simulations in springtime during 2003-2009. Analysis of satellite data shows that the observed range of NO2 VCD over central east China in 2003-2009 is the range between 25 and +34% from the 2004 level, which corresponds approximately to an emission variation between 21 and +29%. The O-3 concentration in the downwind region during 2003-2009 responds linearly to a change of the NO2 VCD over central east China both in the model and in the observation. The corresponding O-3 responses derived from surface observations at remote Japanese sites show linear features consistent with this expectation. The doubling of emissions, i.e., approximately 1.9-fold increase in the NO2 VCD from 2004, leads to O-3 increments of 5 ppbv and 8 ppbv in the model and in the observation, respectively. The modeled O-3 increase due to changes in NOx emission explains approximately 60% of the observed O-3 trend at remote Japanese sites. Thus, approximately 40% of the observed O-3 increase is unaccounted for by the NOx emissions growth. (C) 2012 Elsevier Ltd. All rights reserved.

To investigate the feasibility of new satellite observations, including air quality (AQ) observations from geostationary (GEO) orbit, it is essential to link the measurement precision (epsilon) with sensor specifications in advance. The present study attempts to formulate the linkage between E and specifications of a UV/visible sensor (signal-to-noise ratio (SNR), full width at half maximum (FWHM) of the slit function, and sampling ratio (SR)) on a GEO satellite. A sophisticated radiative transfer model (JACOSPAR) is used to calculate synthetic radiance spectra that would be measured by a UV/visible sensor observing the atmosphere over Tokyo (35.7 degrees N, 139.7 degrees E) from GEO orbit at 120 degrees E longitude. The spectra, modified according to given sensor specifications, are analyzed by the differential optical absorption spectroscopy technique to estimate the E for slant column densities of O-3 and NO2. We find clear relationships: for example, the e of the O-3 slant column density (molecules cm(-2)) and SNR at 330 nm are linked by the equation log(epsilon) = -1.06 . log(SNR) + 20.71 in the UV region, and the epsilon of the NO2 slant column density and SNR at 450 nm are linked by log(epsilon) = -0.98 . log(SNR) + 18.00, at a FWHM = 0.6 nm (for the Gaussian slit function) and SR = 4. The relationships are mostly independent of other specifications (e.g., horizontal and temporal resolutions), as they affect E primarily through SNR, providing constraints in determining the optimal SNR (and alternatively FWHM and SR) for similar UV/visible sensors dedicated for AQ studies.

The study of comparison of NO2 SCD between two ground-based multi axis DOAS is introduced. The slant columns of NO2 from JAMASTEC are compared with those of AIOFM during the period from November to 31 December 2009. It says that the more signal to noise ratio is obtained by using the adjusted integral time rather than fixed settings; Two instrument show good accordance in the lower viewing angles, with the correlation coefficient of 0.995, but it becomes bad with higher viewing angles. The low deviation between the two instruments was achieved during the period from 9am to 17pm, the results in the 20 degree direction show best agreement with a deviation of 12%, but in other period the deviation becomes larger. The results in the visible range are better than those in the UV range, the residual in the fit decreases by more than 60%, and the results in the visible range show good agreements with those of AIOFM in the UV range during the whole day.

From June to July 2009 more than thirty different in-situ and remote sensing instruments from all over the world participated in the Cabauw Intercomparison campaign for Nitrogen Dioxide measuring Instruments (CINDI). The campaign took place at KNMI's Cabauw Experimental Site for Atmospheric Research (CESAR) in the Netherlands. Its main objectives were to determine the accuracy of state-of-the-art ground-based measurement techniques for the detection of atmospheric nitrogen dioxide (both in-situ and remote sensing), and to investigate their usability in satellite data validation. The expected outcomes are recommendations regarding the operation and calibration of such instruments, retrieval settings, and observation strategies for the use in ground-based networks for air quality monitoring and satellite data validation. Twenty-four optical spectrometers participated in the campaign, of which twenty-one had the capability to scan different elevation angles consecutively, the so-called Multi-axis DOAS systems, thereby collecting vertical profile information, in particular for nitrogen dioxide and aerosol. Various in-situ samplers and lidar instruments simultaneously characterized the variability of atmospheric trace gases and the physical properties of aerosol particles. A large data set of continuous measurements of these atmospheric constituents has been collected under various meteorological conditions and air pollution levels. Together with the permanent measurement capability at the CESAR site characterizing the meteorological state of the atmosphere, the CINDI campaign provided a comprehensive observational data set of atmospheric constituents in a highly polluted region of the world during summertime. First detailed comparisons performed with the CINDI data show that slant column measurements of NO2, O-4 and HCHO with MAX-DOAS agree within 5 to 15 %, vertical profiles of NO2 derived from several independent instruments agree within 25% of one another, and MAX-DOAS aerosol optical thickness agrees within 20-30% with AERONET data. For the in-situ NO2 instrument using a molybdenum converter, a bias was found as large as 5 ppbv during day time, when compared to the other in-situ instruments using photolytic converters.

In the present study, we aim at developing an empirical model of BRDF over Tokyo, Japan, which is one of the most polluted areas in Asia, to evaluate the effect of the surface albedo on air-pollution monitoring from space. We used the RossThick-LiSparseReciprocal model with MODIS data to retrieve BRDF information. The BRDF had a strong dependence on season and local time, and the magnitude of the seasonal and local time change was up to 50%.

Multi Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements were taken during 12 hazy days in December 2006 in Fresno, USA. We obtained vertical distributions of aerosol extinction coefficients (AECs) and aerosol optical depths (AODs) at UV wavelengths of 353 and 380 nm by applying a recently developed aerosol retrieval algorithm based on O-4 slant column densities (SCDs) from MAX-DOAS measurements. A linear correlation coefficient (R) of 0.74 (0.73) was obtained between surface PM2.5 concentrations and AECs at 353 (380) nm within the 0-1 km layer under hazy conditions. AODs obtained from MAX-DOAS measurements were validated by comparison with those measured by a collocated sunphotometer. AODs derived at both wavelengths were overestimated under the hazy atmospheric conditions compared with those retrieved from sunphotometer measurements. A coefficient of determination (R-2) of 0.58 (0.79) was obtained for AODs at 353 (380) nm from MAX-DOAS and sunphotometer during the hazy period, and AODs obtained using MAX-DOAS agreed with sunphotometer data within 50% and 40% for the different wavelengths, respectively. (C) 2011 Elsevier Ltd. All rights reserved.

Since March 2007, continuous NO2 profile observations have been performed using ground-based Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) at Cape Hedo (26.87 degrees N, 128.25 degrees E) on Okinawa Island, Japan. NO2 observations show particularly low values of less than 0.3 ppbv at 0-1 km in most cases during the northern summer, whereas higher concentrations of more than 1 ppbv were occasionally observed during winter and spring. Trajectory analysis using meteorological analysis data showed that the high NO2 concentrations were caused mainly by rapid air-mass transport in the marine boundary layer, with strong westerly winds bringing the air mass from coastal China to the study site within 24 h. Such rapid transport is a major cause of NO2 variations at Cape Hedo, even though the region is located approximately 700 km from China. (C) 2011 Elsevier Ltd. All rights reserved.

Aerosols in the troposphere influence photolysis frequencies and hence the concentrations of chemical species. We used a three-dimensional regional chemical transport model (NAQPMS) coupled with an accurate radiative transfer model to examine the impacts of aerosols on summertime photochemistry in Central Eastern China (CEC) via changing photolysis frequencies. In addition to looking at changes in concentrations as previous studies have done, we examined the changes in ozone (O-3) budgets and the uncertainties related to our estimations. The 1st-12th June 2006 was selected as the simulation period when high aerosol optical depth at 550 nm (AOD550) and O-3 were found. A comparison of measurements showed that the model was capable of reproducing the spatial and temporal variations in photolysis frequencies, ultraviolet (UV) radiation, AOD550, cloud optical depth, O-3 and other chemical constitutes in CEC. Aerosols have important impacts on atmospheric oxidation capacity in CEC. On a regional scale, aerosols decreased the average O-3 -&gt; O (D-1) photolysis frequency by 53%, 37% and 21% in the lower, middle and upper troposphere in CEC. The uncertainties of these estimations were 37%, 25% and 14%, respectively. Mean OH concentrations decreased by 51%, 40% and 24% in layers below 1 km, 1-3 km and 3-10 km, with uncertainties of 39%, 28% and 9%, respectively. The changes in HO2 concentrations were smaller but significant. In contrast, NOx showed a significant increase at 0-1 km and 1-3 km in CEC, with magnitudes of 6% and 8%. The largest relative enhancement occurred in downwind regions below 1 km. Summertime boundary layer O-3 (below 1 km and 1-3 km) was reduced by 5% with a maximum of 9% in highly polluted regions. The reduced ozone production (P (O-3)) was responsible for this reduction below 3 km. (C) 2011 Elsevier Ltd. All rights reserved.

In the field, aerosol in-situ measurements are often performed under dry conditions (relative humidity RH &lt; 30-40%). Since ambient aerosol particles experience hygroscopic growth at enhanced RH, their microphysical and optical properties - especially the aerosol light scattering are also strongly dependent on RH. The knowledge of this RH effect is of crucial importance for climate forcing calculations or for the comparison of remote sensing with in-situ measurements. Here, we will present results from a four-month campaign which took place in summer 2009 in Cabauw, The Netherlands. The aerosol scattering coefficient sigma(sp)(lambda) was measured dry and at various, predefined RH conditions between 20 and 95% with a humidified nephelometer. The scattering enhancement factor f (RH,lambda) is the key parameter to describe the effect of RH on sigma(sp)(lambda) and is defined as sigma(sp)(RH,lambda) measured at a certain RH divided by the dry sigma(sp)(dry,lambda). The measurement of f (RH,lambda) together with the dry absorption measurement (assumed not to change with RH) allows the determination of the actual extinction coefficient sigma(ep)(RH,lambda) at ambient RH. In addition, a wide range of other aerosol properties were measured in parallel. The measurements were used to characterize the effects of RH on the aerosol optical properties. A closure study showed the consistency of the aerosol in-situ measurements. Due to the large variability of air mass origin (and thus aerosol composition) a simple parameterization of f (RH,lambda) could not be established. If f (RH,lambda) needs to be predicted, the chemical composition and size distribution need to be known. Measurements of four MAX-DOAS (multi-axis differential optical absorption spectroscopy) instruments were used to retrieve vertical profiles of sigma(ep)(lambda). The values of the lowest layer were compared to the in-situ values after conversion of the latter ones to ambient RH. The comparison showed a good correlation of R-2 = 0.62-0.78, but the extinction coefficients from MAX-DOAS were a factor of 1.5-3.4 larger than the insitu values. Best agreement is achieved for a few cases characterized by low aerosol optical depths and low planetary boundary layer heights. Differences were shown to be dependent on the applied MAX-DOAS retrieval algorithm. The comparison of the in-situ extinction data to a Raman LIDAR (light detection and ranging) showed a good correlation and higher values measured by the LIDAR (R-2 = 0.82-0.85, slope of 1.69-1.76) if the Raman retrieved profile was used to extrapolate the directly measured extinction coefficient to the ground. The comparison improved if only nighttime measurements were used in the comparison (R-2 = 0.96, slope of 1.12).

We attempt for the first time to retrieve lower-tropospheric vertical profile information for 8 quantities from ground-based Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) observations. The components retrieved are the aerosol extinction coefficients at two wavelengths, 357 and 476 nm, and NO2, HCHO, CHOCHO, H2O, SO2, and O-3 volume mixing ratios. A Japanese MAX-DOAS profile retrieval algorithm, version 1 (JM1), is applied to observations performed at Cabauw, the Netherlands (51.97 degrees N, 4.93 degrees E), in June-July 2009 during the Cabauw Intercomparison campaign of Nitrogen Dioxide measuring Instruments (CINDI). Of the retrieved profiles, we focus here on the lowest-layer data (mean values at altitudes 0-1 km), where the sensitivity is usually highest owing to the longest light path. In support of the capability of the multi-component retrievals, we find reasonable overall agreement with independent data sets, including a regional chemical transport model (CHIMERE) and in situ observations performed near the surface (2-3 m) and at the 200-m height level of the tall tower in Cabauw. Plumes of enhanced HCHO and SO2 were likely affected by biogenic and ship emissions, respectively, and an improvement in their emission strengths is suggested for better agreement between CHIMERE simulations and MAX-DOAS observations. Analysis of air mass factors indicates that the horizontal spatial representativeness of MAX-DOAS observations is about 3-15 km (depending mainly on aerosol extinction), comparable to or better than the spatial resolution of current UV-visible satellite observations and model calculations. These demonstrate that MAX-DOAS provides multi-component data useful for the evaluation of satellite observations and model calculations and can play an important role in bridging different data sets having different spatial resolutions.

Understanding the relationship between black carbon (BC) and carbon monoxide (CO) will help improve BC emission inventories and the evaluation of global/regional climate forcing effects. In the present work, the BC (PM1) mass concentration and CO mixing ratio were continuously measured at a high-altitude background station on the summit of Mt. Huang (30.16 degrees N, 118.26 degrees E, 1840ma.s.l.). Annual mean BC mass concentration was 1004.5 +/- 895.5 ng m(-3) with maxima in spring and autumn, and annual mean CO mixing ratio was 424.1 +/- 159.2 ppbv. A large increase of CO was observed in the cold season, implying the contribution from the large-scale domestic coal/biofuel combustion for heating. The BC-CO relationship was found to show different seasonal features but strong positive correlation (R &gt; 0.8). In Mt. Huang area, the Delta BC/Delta CO ratio showed unimodal diurnal variations and had a maximum during the day (09:00-17:00 LST) and minimum at night (21:00-04:00 LST) in all seasons, indicating the impact of planetary boundary layer and the intrusion of clean air masses from the high troposphere. Back trajectory cluster analysis showed that the Delta BC/Delta CO ratio of plumes from the Eastern China (Jiangsu, Zhejiang provinces and Shanghai) was 8.8 +/- 0.9 ng m(-3) ppbv(-1). Transportation and industry were deemed as controlling factors of the BC-CO relationship in this region. The Delta BC/Delta CO ratios for air masses from Northern China (Anhui, Henan, Shanxi and Shandong provinces) and southern China (Jiangxi, Fujian and Hunan provinces) were quite similar with mean values of 6.5 +/- 0.4 and 6.5 +/- 0.2 ng m(-3) ppbv(-1) respectively. The case studies combined with satellite observations demonstrated that the Delta BC/Delta CO ratio for biomass burning (BB) plumes were 10.3 +/- 0.3 and 11.6 +/- 0.5ng m(-3) ppbv(-1), significantly higher than those during non-BB impacted periods. The loss of BC during transport was also investigated on the basis of the Delta BC/Delta 1CO-RH (relative humidity) relationship along air mass pathways. The results showed that BC particles from Eastern China area was much more easily removed from atmosphere than other inland regions due to the higher RH along transport pathway, implying the importance of chemical compositions and mixing states on BC residence time in the atmosphere.