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The Arctic Airborne Measurement Program 2002(AAMP 02) campaign was carried out in March 2002 as one of the sub programs of the project Variations of atmospheric constituents and their climate impact in the Arctic". The main goal of the project was to investigate the transport, transformation and radiative effect of trace gases and aerosols, and their role in the global climate. An instrumented jet plane, Gulfstream II(G-II), was flown from Nagoya, Japan via Barrow, Alaska to Longyearbyen(78°N , 15°E ), Svalbard, crossing the Arctic Ocean in the lower stratospher. Three local flights were made over the Greenland Sea around Svalbard and two profile flights near Barrow. The plane was equipped with CO_2 and ozone analyzers, gas and aerosol sampling systems, aerosol particle counter, nephelometer, absorption photometer, PMS particle probes, sunphotometer, dew point hygrometer and dropsonde system. During the campaign, intensitive surface operations were also conducted at Ny-Ålesund(79°N , 12°E ), Svalbard. Vertical profiles of several trace gases gave information about transport, a new observation by sunphotometer derived an aerosol optical depth in the stratosphere, and another new observation by dropsonde gave information on the polar vortex.

In order to acquire long-term data sets of backscatter profiles of clouds and aerosols in the polar regions, we started Micro-pulse Lidar (MPL) measurements at Ny-Alesund, Svalbard in March 1998 and at Syowa Station, Antarctica in January 2001. The MPL data have been acquired and analyzed for 11 months from the Arctic measurement and for 12 months from the Antarctic measurement. Fine structures of clouds and their temporal change were observed by MPLs with a 30-m range resolution and a 1-min time average. Statistical features of the polar clouds were investigated from the Arctic and Antarctic measurements. Results from the preliminary analysis indicated some differences of seasonal cloud appearance and cloud base heights at the two polar sites. Some features obtained in this study are as follows: over Syowa Station, Antarctica, high altitude clouds tended to appear in (austral) summer, and low altitude appeared more often in (austral) spring and autumn. On the other hand, low altitude clouds in the Arctic were observed particularly in summer and early autumn. Clear sky days were not expected in this season. In both polar regions, the winter clouds were relatively thin compared to the summer clouds.

Shipboard aerosol measurements in the marine boundary layer (MBL) were carried out over the western Pacific Ocean through the eastern Indian Ocean during a cruise of the Antarctic research vessel Shirase from Tokyo, Japan to Fremantle, Australia in November 2000, as part of the 42nd Japanese Antarctic Research Expedition (JARE42) activities. The latitudinal variation of aerosol optical properties is investigated with the origin of aerosols. For elucidation of aerosol properties, a method for retrieving the complex refractive index from combined measurements is proposed using an optical particle counter, an integrating nephelometer and a particle soot absorption photometer. Backward trajectory analyses indicate three regions that are characterized by three distinct aerosol types: anthropogenic/continental aerosols (30°-33.5°N), maritime aerosols (3°-28°N), and biomass-burning aerosols (12°-2°S). Retrieval of the imaginary part of the complex refractive index is successfully achieved by the proposed method, resulting in mean values of 0.0056, 0.0003, and 0.0036 for anthropogenic/continental, maritime, and biomass-burning aerosols, respectively.

Concentrations of carbonyl sulfide (COS) were measured in whole air samples collected between East Asia (Japan) and the Arctic (Spitsbergen) up to an altitude of 12 km during the Arctic Airborne Measurement Program 98 (AAMP98). Continuously measured O3 and CO2 concentrations were used to interpret the distribution of COS concentrations. A latitudinal gradient to lower concentrations of COS was observed poleward of 70°N; concentrations of COS were 421±27 pptv poleward of 70°N and 461±30 pptv at 60-70°N. The relationship between COS concentration and the O3/CO2 ratio indicates that the concentrations of COS near the ozonopause were almost equal to those in the troposphere, and then decreased as the O3/CO2 ratio increased. Tropospheric influence was observed up to potential temperatures of 350 K in this study. According to the AAMP98 observations, on the basis of the trajectory analysis and the O3/O2 ratio, distribution of COS in the Arctic lowermost stratosphere is certainly effected by the downward transport of an arctic stratospheric air mass and by the horizontal transport of a tropospheric air mass across the tropopause over midlatitudes. The sulfate aerosol produced by COS oxidation is estimated to be very small at the observed altitudes between East Asia and the Arctic in late winter.

The Arctic Airborne Measurement Program (AAMP) was planned to investigate the transport, exchange and chemical processes of gas and aerosol in the Arctic atmosphere in early spring, and further to understand their roles in global change. An instrumented aircraft, Gulfstream II (G-II) twin-jet plane, was used for airborne measurements in the troposphere and lower stratosphere of the Arctic. For the AAMP 1998 campaign, G-II was equipped with CO_2 and O_3 concentration monitor systems, gas and aerosol sampling systems, aerosol particle counters, and the PMS 1D and 2D airborne particle probes. The aircraft was flown from Alaska, USA to Svalbard, Norway passing over the North Pole, and on the reverse route, in the first half of March 1998. The approximate cruising altitude was 12km for long-range flights. Vertical profiles of gas and aerosol concentrations were obtained over Spitsbergen, Svalbard and Barrow, Alaska. A convective cloud system associated with a polar low was observed over the Norwegian Sea. Another cloud observation was made for marine boundary layer clouds over the open sea off Spitsbergen. Most of the instruments on-board G-II worked well, and measurements were successfully acquired during the AAMP 1998 campaign.

We consider explanations for disagreements between models and measurements of clear-sky solar transmission. Data from four cloud-free days during the FIRE 1991 field experiment are studied. Our model simulations of solar broadband fluxes exceed measurements by about 10%, About half of this discrepancy occurs in the near-infrared spectral region. Ahout half of this discrepancy can be linked to the direct irradiance. These deviations suggest (1) model underestimates in near-infrared trace-gas absorption and (2) errors in visible diffuse fluxes. The near-infrared error in other models is generally less than the one associated with our model. Other models suggest more trace-gas absorption. However. variations among models are so large that they swamp current measurement errors such as uncertainties of the water vapor column. The visible diffuse flux error cannot he easily explained. We illustrate that a poor cosine response of solar flux instruments could have contributed. Also, underestimates of aerosol absorption could be a factor. There is clearly a need for measurements and comparisons at high spectral resolution to better quantify the sources of these errors. However. these comparisons will only he fruitful if we have confidence in the accuracy of our models and the accuracy of the data.

With the aim of improving the consistency of terrestrial and atmospheric longwave radiation measurements within the Baseline Surface Radiation Network, five Eppley Precision Infrared Radiometer (PIR) pyrgeometers and one modified Meteorological Research Flight (MRF) pyrgeometer were individually calibrated by 11 specialist laboratories. The round-robin experiment was conducted in a ‘‘blind’’ sense in that the participants had no knowledge of the results of others until the whole series of calibrations had ended. The responsivities C(mV/ Wm 22) determined by 6 of the 11 institutes were within about 2% of the median for all five PIR pyrgeometers. Among the six laboratories, the absolute deviation around the median of the deviations of the five instruments is less than 1%. This small scatter suggests that PIR pyrgeometers were stable at least during the two years of the experiment and that the six different calibration devices reproduce the responsivity C of PIR pyrgeometers consistently and within the precision required for climate applications. The results also suggest that the responsivity C can be determined without simultaneous determination of the dome correction factor k, if the temperature difference between pyrgeometer body and dome is negligible during calibration. For field measurements, however, k has to be precisely known. The calibration of the MRF pyrgeometer, although not performed by all institutes, also showed satisfactory results.

Measurements from the FIRE 1991 cirrus cloud field experiment in the central United States are presented and analyzed. The first part focuses on cirrus microphysical properties. Aircraft 2D-probe in situ data at different cloud altitudes were evaluated for cirrus cases on four different days. Also presented are simultaneous data samples from balloonborne videosondes. Only these balloonsondes could detect the smaller crystals. Their data suggest (at least for midlatitude altitudes below 10 km) that ice crystals smaller than 15 microns in size are rare and that small ice crystals not detected by 2D-probe measurements are radiatively of minor importance, as overlooked 2D-probe crystals account for about 10% of the total extinction. The second part focuses on the link between cirrus cloud properties and radiation. With cloud macrophysical properties from surface remote sensing added to the microphysical data and additional radiation measurements at the surface, testbeds for radiative transfer models were created. To focus on scattering processes, model evaluations were limited to the solar radiative transfer by comparing calculated and measured transmissions of sunlight at the surface. Comparisons under cloud-free conditions already reveal a model bias of about +45 W/sq m for the hemispheric solar downward broadband flux. This discrepancy, which is (at least in part) difficult to explain, has to be accounted for in comparisons involving clouds. Comparisons under cirrus cloud conditions identify as the major obstacle in cirrus solar radiative transfer modeling the inability of one-dimensional radiative transfer models to account for horizontal inhomogeneities. The successful incorporation of multidimensional radiative transfer effects will depend not only on better models but critically on the ability to measure and to define characteristic inhomogeneity scales of cloud fields. The relative minor error related to the microphysical treatment is in part a reflection of the improved understanding on solar scattering on ice crystals over the last decade and of the available wealth on ice-crystal size and shape data for this study. In absence of this information, uncertainties from microphysical cirrus model assumptions will remain high.

We investigated characteristics of cloud and long-wave downward radiation during the year 2008 at Ny-Ålesund using Micro Pulse LIDAR (MPL) and the pyrgeometer in Baseline Surface Radiation Network (BSRN). We found that long-wave downward radiation was lower as cloud base height was higher on January 1, when mean cloud amount was 10., 第4回極域科学シンポジウム個別セッション：[OM] 気水圏11月15日（金） 国立極地研究所 ３階ラウンジ

第4回極域科学シンポジウム横断セッション：[IA] 「急変する北極気候システム及びその全球的な影響の総合的解明」―GRENE北極気候変動研究事業研究成果報告2013―11月12日（火） 国立極地研究所 ２階大会議室

Optical depths in the visible to infrared spectral region were obtained from solar extinction measurements with two sun photometers during the First ISCCP Regional Experiment Phase II Cirrus Intensive Field Observation in Kansas. A method is described to correct sun photometry for gaseous absorption and is extended to estimate the water vapor amount. The approach uses a prior computation of gaseous absorption for the narrowband-pass sun photometry, parameterized with the slant-path absorber amount. These produce correction coefficients for gaseous absorption, as determined by LOWTRAN 7 models. Near-infrared channels were calibrated by modified Langley plots taking account of gaseous absorption. After the correction and calibration, the aerosol optical depths at the wavelength of 0.4–4 µm were obtained for clear sky conditions. The aerosol optical depth at the wavelength λ = 0.5 µm was 0.1–0.2 during the campaign. The cloud optical depth at λ = 0.5 µm was obtained for cirrus events on 26 November ...

A new method is proposed to retrieve various cloud physical parameters of water clouds from the solar-flux reflectances at four wavelengths measured by using the airborne Multi-channel Cloud Pyranometer (MCP) system. The MCP system was designed to measure the spectral reflectances at nine wavelengths in the visible and near-infrared region. The estimation procedure assumes a locally plane-parallel and vertically homogeneous water-cloud layer with monomodal particle size distributions of a fixed width. The cloud optical thickness τ500 and the effective particle radius re, of the water-cloud layer can be simultaneously retrieved from the MCP reflectances measured at the visible channel of λ=500 nm and at the near-infrared channel of λ=1650 nm. Under the assumption that cloud pressure height is known, the cloud liquid water content (LWC) can then be retrieved from the MCP reflectance at the oxygen absorption-band channel cantered at λ=760 nm. Finally, the in-cloud water vapor amount uH2O can be esti...

The design and performance of a spectral radiometer system are described for airborne measurements of solar flux reflectance by clouds. The system consists of a pair of identical multichannel pyranometers: one installed on the top and the other on the bottom of an aircraft fuselage to measure the downward and upward solar irradiances, respectively. This measurement scheme has an advantage in that reflectances derived from ratios between the upward and downward irradiances can avoid the need for absolute radiometric calibrations. The multichannel cloud pyranometer (MCP) system measures near-monochromatic solar irradiances at nine discrete wavelengths between 420 and 1650 nm by using interference filters with very narrow bandwidths. Included among these wavelengths are 760 and 938 nm in the oxygen and water vapor absorption bands, respectively. Solar radiation passing through the filters is instantly detected by a silicon photodiode for wavelength λ 1 µm. Go...

An inclined lidar with vertical resolution of 0.4 m was used for detailed boundary layer studies and to link observations at Zeppelin Mountain (474 m) and Ny-Alesund, Svalbard. We report on the observation of aerosol layers directly above the Kongsfjord. On 29 April 2007, a layer of enhanced backscatter was observed in the lowest 25 m above the open water surface. The low depolarization ratio indicated spherical particles. In the afternoon, this layer disappeared. The ultrafine particle concentration at Zeppelin and Corbel station (close to the Kongsfjord) was low. On 1 May 2007, a drying process in the boundary layer was observed. In the morning, the atmosphere up to Zeppelin Mountain showed enhanced values of the backscatter coefficient. Around noon, the top of the highly reflecting boundary layer decreased from 350 to 250 m. The top of the boundary layer observed by lidar was confirmed by radiosonde data.

A method is proposed to estimate the optical thickness of cirrus clouds from ground-based sun photometry. Transfer calculations of solar radiation in ice clouds were made by the Monte Carlo method. A scattering phase function presented by Takano and Liou was employed for ice clouds. Simulations of sun photometry, which include strong forward scattering into the instrument's field of view, give a simple relationship between the true and apparent optical thicknesses. The correction method was applied to Sun photometer measurements for cirrostratus clouds observed at Tsukuba, Japan. The relationship between the visible optical thickness and the broadband solar flux transmittance obtained from observations agreed well with that theoretically expected for cloud optical thickness up to about 10.

The ASTAR 2000 (Arctic Study of Tropospheric Aerosol and Radiation) campaign ran from 12 March until 25 April 2000 with extensive flight operations in the vicinity of Svalbard (Norway) from Longyearbyen airport (78.25°N, 15.49°E). It was a joint Japanese (NIPR Tokyo)–German (AWI Bremerhaven/Potsdam) airborne measurement campaign using AWI aircraft POLAR 4 (Dornier 228-101). Simultaneous ground-based measurements were done at the international research site Ny-Alesund (78.95°N, 11.93°E) in Svalbard, at the German Koldewey station, at the Japanese Rabben station and at the Scandinavian station at Zeppelin Mountain (475 m above sea level). During the campaign 19 profiles of various aerosol properties were measured. In general, the Arctic spring aerosol in the vicinity of Svalbard had significant temporal and vertical variability. A strong haze event occurred between 21 and 25 March in which the optical depth from ground-based observation was 0.18, which was significantly greater than the background value of 0.06. Airborne measurements on 23 March during this haze event showed a high aerosol layer with an extinction coefficient of 0.03 km −1 or more up to 3 km and a scattering coefficient from 0.02 in the same altitude range. From the chemical analyses of airborne measurements, sulfate, soot and sea salt particles were dominant, and there was a high mixing ratio of external soot particles in some layers during the haze event, whereas internal mixing of soot in sulfate was noticeable in some layers for the background condition. We argue that the high aerosol loading is due to direct transport from anthropogenic source regions. In this paper we focus on the course of the haze event in detail through analyses of the airborne and ground-based results. DOI: 10.1111/j.1600-0889.2005.00140.x

The size distribution and volatility of ultrafine aerosol particles were measured using scanning mobility particle sizer and thermodenuder at Syowa Station during the 46–47 Japanese Antarctic Research Expeditions (2005–2007). The relative abundance of non-volatile particles in a 240 °C scan was approximately 20% during the summer, whereas the abundance of non-volatile particles increased by >90% during the winter–spring. Most ultrafine particles were volatilized at temperature of 150–210 °C. This volatility was consistent well to major aerosol constituents (NH4+, SO42− and CH3SO3−) during the summer. In contrast, major constituents of ultrafine particles were sea-salts (Na+ and Cl−) in winter–spring. Therefore, the seasonal feature of volatility of ultrafine particles at Syowa was associated with seasonal variations of the major aerosol constituents. Although the relative abundance of non-volatile particles was usually higher during the winter–spring, the abundance dropped occasionally to

Accuracy requirements for aerosol optical depth (AOD) in polar regions are much more stringent tan those usually encountered in established sun photometer networks, while comparability of data from different archive centres is a further important issue. Therefore, two intercomparison campaigns were held during spring 2006 at Ny-Ålesund (Svalbard) and autumn 2008 at Izaña (Tenerife) within the framework of the IPY POLAR-AOD project, with the participation of various research institutions routinely employing different instrument models at Arctic and Antarctic stations. As reported here, a common algorithm was used for data analysis with the aim of minimizing a large part of the discrepancies affecting the previous studies. During the Ny-Ålesund campaign, spectral values of AOD derived from measurements taken with different instruments were found to agree, presenting at both 500 nm and 870 nm wavelengths average values of root mean square difference (RMSD) and standard deviation of the difference (SDD) equal to 0.003. Correspondingly, the mean bias difference (MBD) varied mainly between _0.003 and þ0.003 at 500 nm, and between _0.004 and þ0.003 at 870 nm. During the Izaña campaign, which was also intended as an intercalibration opportunity, RMSD and SDD values were estimated to be equal to 0.002 for both channels on average, with MBD ranging between _0.004 and þ0.004 at 500 nm and between _0.002 and þ0.003 at 870 nm. RMSD and SDD values for Ångström exponent a were estimated equal to 0.06 during the Ny-Ålesund campaign and 0.39 at Izaña. The results confirmed that sun photometry is a valid technique for aerosol monitoring in the pristine atmospheric turbidity conditions usually observed at high latitudes. The Italian research activity was supported by the Programma Nazionale di Ricerche in Antartide (PNRA) and developed as a part of Subproject 2006/6.01: “POLAR-AOD: a network to characterize the means, variability and trends of the climate-forcing properties of aerosols in polar regions”. The GOA-UVA group was funded by MICINN under projects CGL2008-05939-C01/CLI, CGL2009-09740 and CGL2009-09480-E. The Canadian research activity was supported by CANDAC (Canadian Network for the Detection of Atmospheric Change) and their funding organizations: CFCAS (Canadian Foundation for Climate and Atmospheric Sciences, CFI (Canadian Foundation for Innovation), NSERC (National Sciences and Engineering Research Council) and the IPY (NSERC administered) fund. Polish efforts were made within a framework of the POLAR-AOD National Grant.

第１回極域科学シンポジウム「極域大気圏を通して探る地球規模環境変動」ポスター発表

[1] During our aerosol measurement program at Syowa Station, Antarctica, in 2004-2007, some low-visibility (haze) phenomena were observed during winter―spring under conditions with low winds and without drifting snow and fog. During "Antarctic haze" phenomena, the number concentration of aerosol particles and black carbon concentration increased by 1 to 2 orders higher relative to background conditions at Syowa Station, whereas surface O 3 concentration dropped simultaneously, especially after polar sunrise. Chemical analysis showed that major aerosol constituents in the haze phenomena were sea salt (e.g., Na + , Cl ― ). Trajectory analysis and the Navy Aerosol Analysis and Prediction System model showed that plumes from biomass burning in South America and southern Africa were transported to Syowa Station, on the Antarctic coast, because of the eastward (occasionally westward) approach of cyclones in the Southern Ocean and subsequent poleward flow. This poleward flow from midlatitudes of the plume and injection of sea-salt particles during the transport might engender Antarctic haze phenomena at Syowa Station. Differences of 0 3 concentration between the background and the haze conditions tended to be larger in spring (after polar sunrise) than in winter. Enhancement of sea-salt particles in the haze events can serve important roles in providing additional sources of reactive halogen species.

[1] Aerosol optical depth (AOD) measurements were acquired at six Arctic sunphotometer sites during the ARCTAS-A (April, 2008) campaign. Numerous smoke events were identified and related to extensive forest and agricultural fires in eastern Russia and northern Kazakhstan/southwestern Russia respectively. An analysis of the fine (sub-micron) optical depths from the six stations indicated the presence of underlying low frequency trends which were coherent with general meteorological considerations, source information, model estimates and remote sensing information. Low frequency (diurnal) coarse-mode optical depth events were observed at a number of the stations; these singular events are likely due to ice particles whose nucleation may have been associated with the presence of smoke, or possibly dust.

Precise and continuous measurements of atmospheric CO_2 concentration have been continued at Syowa Station (69°00'S, 39°35'E), Antarctica since February 1984. Diurnal CO_2 variation was hardly observable throughout the year. The secular CO_2 trend was variable with time, showing slow increase in 1984,1986 and 1988 and rapid increase in 1985 and 1987. The annual CO_2 increase was remarkable, especially in 1987,which may be related to the 1987 ENSO event. The average rate of annual CO_2 increase over the last 5 years was about 1.6 ppmv yr^. The average seasonal CO_2 cycle showed minimum and maximum concentrations in mid-April and in early October, respectively. Its peak-to-peak amplitude was about 1.1 ppmv for the period 1984-1988. The seasonal cycle was variable from year to year, but there was no indication of long-term amplitude increase. It was found that irregular CO_2 variations with amplitudes of about 0.2 ppmv and with periods of a few tens of days have high correlation with air mass exchange by synoptic scale weather disturbances.

赤外放射フラックスの測定に広く用いられるEppley社のシリコン製ドーム付赤外放射計 (PIR) について、ドームの射出効果を定量的に調べた。温度を室温から-25°Cまで制御できる黒体錐とドーム温度を変化させるための装置を有する検定用黒体槽を開発し、PIRの測器定数およびドーム係数を求めた。ドームの射出効果をドーム温度を用いて補正することにより、温度上昇・下降時に見られたPIR出力のヒステリシスが消失し、入射放射量対PIR出力の検定回帰直線が精度良く得られることが確かめられた。PIRを用いた下向き赤外放射フラックスの野外測定では、ドーム効果によって、それを無視した場合には晴天大気下の地上観測では20W/m2以上の過大評価、航空機観測では10～20W/m2の過小評価がなされることがわかった。ドーム温度を測定しドーム効果を適正に補正することにより、10W/m2前後の誤差で赤外放射フラックスが測定されることを示す。

During the Arctic Study of Tropospheric Aerosol, Clouds and Radiation (ASTAR), which was conducted in Svalbard in March and April 2007, tropospheric Arctic clouds were observed with two ground-based backscatter lidar systems (micro pulse lidar and Raman lidar) and with an airborne elastic lidar. An increase in low-level (cloud tops below 2.5 km) cloud cover from 51% to 65% was observed above Ny-Ålesund during the time of the ASTAR campaign. Four different case studies of lidar cloud observations are analyzed: With the ground-based Raman lidar, a pre-condensation layer was observed at an altitude of 2 km. The layer consisted of small droplets with a high number concentration (around 300 cm−3) at low temperatures (−30°C). Observations of a boundary layer mixed-phase cloud by airborne lidar were evaluated with the measurements of concurrent airborne in situ and spectral solar radiation sensors. Two detailed observations of multiply layered clouds in the free troposphere are presented. The first case was composed of various ice layers with different optical properties detected with the Raman lidar, the other case showed a mixed-phase double layer and was observed by airborne lidar. The analysis of these four cases confirmed that lidar data provide information of the whole range from subvisible to optically thick clouds. Despite the attenuation of the laser signal in optically thick clouds and multiple scattering effects, information on the geometrical boundaries of liquid water clouds were obtained. Furthermore, the dominating phase of the clouds' particles in the layer closest to the lidar system could be retrieved.

Precise and continuous measurements of the atmospheric CO 2 concentration have been made at Syowa Station, Antarctica since February 1984. The diurnal CO 2 variation was hardly observable throughout the year. The secular CO 2 trend was variable with time, showing slow increase in 1984, 1986 and 1988 and rapid increase in 1985 and 1987. The annual CO 2 increase was especially large in 1987, which may be related to the 1986/1987 ENSO event. The average rate of annual CO 2 increase over the last 5 years was about 1.6 ppmv yr -1 . The average seasonal CO 2 cycle showed minimum and maximum concentrations in mid-April and early in October, respectively, and its peak-to-peak amplitude was about 1.1 ppmv. The measured seasonal cycle was variable from year to year, but there was no indication of a long-term increase of the amplitude. It was found that irregular CO 2 variations with amplitudes of 0.2 ppmv at most and periods of a few weeks show high correlation with airmass exchange by synoptic scale weather disturbances. The results from Syowa are compared with those from the South Pole and Cape Grim, Tasmania. DOI: 10.1034/j.1600-0889.1991.00007.x

[1] Modification of sea salt aerosol particles (SSA particles) by HNO3 and SO2 is an important process for changing phase partitioning of acidic gases from industrial regions to the ocean. During 12–29 September 2005, size-segregated aerosol particles and acidic gases were sampled around the western part of the Japanese Islands to elucidate controlling factors of modification of SSA particles by acidic gases and to estimate dry deposition flux over the ocean. For coarse (>2 μm diameter) SSA particles, the amount of Cl− deficiency from the seawater ratio was comparable to the sum of the equivalent concentrations of NO3− and nonsea-salt (nss) SO42−, suggesting Cl− displacement of SSA particles by acidic gases such as HNO3 and SO2. The Cl− deficiency of SSA particles varied according to the size range and wind speed. Decreasing modification occurred with increasing wind speed for particles of 2–8 μm. Under high (low) wind conditions, the NO3− concentration per unit surface area of coarse SSA particles was lower (higher) for particles >8 μm than for those of 2–8 μm diameter. The respective dry deposition fluxes (Fdry) of NO3−, nss-SO42−, HNO3, and SO2 were estimated according to the wind speed and size of aerosol particles. On average, the Fdry of particulate NO3− was 10 times larger than that of HNO3, but Fdry of nss-SO42− was almost equal to that of SO2. Phase partitioning of dry deposition for NO3− and nss-SO42− over the ocean differs from that of coastal marine areas.

Measurement of black carbon (BC) was carried out at Syowa station Antarctica (69° S, 39° E) from February 2004 until January 2007. The BC concentration at Syowa ranged from below detection to 176 ng m−3 during the measurements. Higher BC concentrations were observed mostly under strong wind (blizzard) conditions due to the approach of a cyclone and blocking event. The BC-rich air masses traveled from the lower troposphere of the Atlantic and Indian Oceans to Syowa (Antarctic coast). During the summer (November–February), the BC concentration showed a diurnal variation together with surface wind speed and increased in the katabatic wind from the Antarctic continent. Considering the low BC source strength in the Antarctic continent, the higher BC concentration in the continental air (katabatic wind) might be caused by long range transport of BC via the free troposphere from mid- and low- latitudes. The seasonal variation of BC at Syowa had a maximum in August, while at the other coastal stations (Halley, Neumayer, and Ferraz) and the continental station (Amundsen-Scott), the maximum occurred in October. This difference may result from different transport pathways and scavenging of BC by precipitation during the transport from the source regions. During the austral summer, long-range transport of BC via the free troposphere is likely to make an important contribution to the ambient BC concentration. The BC transport flux indicated that BC injection into the Antarctic region strongly depended on the frequency of storm (blizzard) conditions. The seasonal variation of BC transport flux increased by 290 mg m−2 month−1 in winter–spring when blizzards frequently occurred, whereas the flux decreased to lower than 50 mg m−2 month−1 in the summer with infrequent blizzards.

Optical observation around near UV spectral region potentially enables us to retrieve light absorbing features of aerosol, such as type as well as optical thickness. We analyzed near UV observation data to identify haze properties around Japan in the autumn of 2003, using Global Imager onboard Advanced Earth Observing Satellite-II (ADEOS-II/GLI), which has 380nm and 400nm window channels. At the same time, we had optical observation, such as a ground-based LIDAR measurement and a shipborne skyradiometer measurement, so as to retrieve vertical profile, particle sphericity, particle size distribution, and optical thickness of the haze. Based upon the three kinds of analyses with remotely sensed data, such as satellite, LIDAR, and skyradiometer, we have the following characteristics of the haze: little UV absorbing, of optical thickness 0.5 (around 500nm), within lower boundary layer (less than around 1km a.s.l.), and of spherical and fine particles (0.2 μm in radius). We also have some direct sampling measurements onboard Research Vessel Shirase, such as integrated nephelometer, particle soot / absorption photometer, and optical particle counter, so as to identify optical and microphysical properties of the haze as well as chemical composition analyses. The results of the surface direct sampling showed the dense haze dominantly consisted of smaller (0.2 μm in radius) and sulfate particulates, which is consistent to the remotely sensed results. Backward trajectory simulations also indicate that the hazy air mass had arrived from / through some mega cities over East Asia. Further, we are going to investigate the consistency between optical, microphysical, chemical, and dynamical aspects using a chemical transport model.

[1] Type II polar stratospheric clouds (PSCs) were observed by micropulse lidar (MPL) at Syowa Station in the Antarctic on 30 June and on 1 July 2001. The vertical profiles of the PSCs had a wavy structure that was synchronized with the temperature fluctuations. A wave analysis using radiosonde data shows that the wavy fluctuations were associated with an inertia gravity wave that was not forced by ground topography, but probably by a spontaneous adjustment in association with synoptic-scale wave-breaking processes in the upper troposphere. It is suggested that the observed PSCs were generated under the low-temperature conditions induced by these waves and that such gravity waves generated by spontaneous adjustment of large-scale fields can be more important to the formation of PSC particles, in both the Antarctic and Arctic stratosphere, than topographically forced gravity waves, because the former are not fixed to the ground topography. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0320 Atmospheric Composition and Structure: Cloud physics and chemistry; 0340 Atmospheric Composition and Structure: Middle atmosphere—composition and chemistry; 3334 Meteorology and Atmospheric Dynamics: Middle atmosphere dynamics (0341, 0342); KEYWORDS: polar stratospheric clouds, inertia gravity waves, micropulse lidar

Continuous measurement of the atmospheric CO_2 concentration was initiated at Syowa Station in February 1984. Variation of CO_2 concentration at this station can be divided into three components such as secular trend, seasonal cycle and irregular variation after removing contaminated data. The secular trend was variable with time. The increase rate of CO_2 concentration was low from 1984 to 1986,but it became very high in 1987 and 1988. This change may be related to the 1987 ENSO event. The average rate of annual CO_2 increase over the 5 years was about 1.6 ppmv (yr)^. The average seasonal CO_2 cycle showed minimum and maximum concentrations in mid-April and early in October and its peak-to-peak amplitude was about 1.1 ppmv. The seasonal cycle including irregular parts was variable from year to year, but there was no indication of long-term expansion of the amplitude. The irregular CO_2 variation observed, especially from February to August, had a high correlation with the air mass exchange by synoptic scale weather disturbances.

Aircraft and ground-based measurements of the atmospheric CO 2 concentration have been made at Syowa Station, Antarctica since January 1983. The minimum concentration of the average seasonal CO 2 cycle occurs in March throughout the troposphere, while the maximum concentration appears in mid-August in the upper troposphere and in late September in the lower and middle troposphere. The peak-to-peak amplitude of the cycle decreases slightly with height. The CO 2 concentration increases with height during most of the year, but from late winter to spring this height dependency is minimal. To examine the contribution of the atmospheric transport processes to these variations of the CO 2 concentration, a 3-dimensional trajectory analysis was performed using data from the US National Meteorological Center. From the results obtained, it is postulated that northern hemispheric air with relatively high CO 2 concentration is transported to the antarctic region through the upper troposphere from late fall to winter, while air with low CO 2 concentration is transported from the southern hemisphere middle latitudes into the antarctic region through the lower troposphere in the remaining seasons. It is hypothesized that these air transport processes could influence CO 2 variations over the station. DOI: 10.1034/j.1600-0889.47.issue4.1.x

Aircraft and ground-based measurements of the atmospheric CO_2 concentration have been made respectively at and over Syowa Station, Antarctica since January 1983. The minimum concentration of the average seasonal CO_2 cycle occurs in March throughout the troposphere and the maximum concentration appears in mid-August and late in September in the upper troposphere and in the lower and middle troposphere, respectively. The peak-to-peak amplitude of the cycle decreases slightly with height. The CO_2 concentration increases with height during most of the year and the height-dependent concentration difference is smaller from late winter to spring than in the remaining seasons. To interpret these variations of the CO_2 concentration, 3-dimensional trajectory analysis was done using U.S. NMC data. From the results obtained, it is suggested that the northern hemispheric air with high CO_2 concentration is transported to the Antarctic region through the upper troposphere from late fall to winter, while the air with low CO_2 concentration is transported from southern middle latitudes into the Antarctic region through the lower troposphere in the remaining seasons. These air transport processes are especially important for variations of the CO_2 concentration over the station.

Attenuation measurements of solar irradiance using an airborne sun photometer were performed for the first time over Syowa Station, Antarctica. The NIPR's Cessna 185 aircraft equipped with a sun photometer (Eko, Model MS-111) took 4 flights during JARE-25,on January 19,September 3,December 25 and 26,1984. The aerosol optical thicknesses (AOT) at wavelengths of 0.369,0.5,0.675 and 0.862μm were obtained at several altitudes up to 5km on each flight. The temporal change of vertical profiles of AOT confirmed that the decrease of AOT found in the ground-based measurements during 1984 (cf., M. SHIOBARA et al. : Mem. Natl Inst. Polar Res., Spec. Issue, 45,93,1986) reflects the depletion of stratospheric aerosols enhanced by the El Chichon eruption in 1982. The tropospheric AOT over Syowa Station was estimated as 0.005-0.01 at 0.5μm wavelength and was nearly comparable with the non-disturbed stratospheric AOT in contrast with the mid-latitude region where the tropospheric AOT constitutes most of the AOT of the whole atmosphere.

Measurements of direct and diffuse so[ar radiations w巴re carn巴d out in cooperation withinsitu measurements of aeroso[s during two periods of Nov. 4-7 , 1978 and Nov. 1-3, [979 in Sendai, Japan. Intercomparison of volume sp巴ctraof aeroso[s 0 btained by s巴vera[kinds of instrum巴ntsshowed that bimodal volume spectra 釘e preferred to int巴rpret the observed data. Values of the complex refractive index of aerosols were also investigat巴dusing a polar n巴phclomcterand th巴 diffuseto global radiation ratio measured by spectro-pyranome ters.

南極昭和基地において, 大気中の二酸化炭素濃度を高精度かつ連続的に観測するために, 非分散型赤外CO_2分析計(分析精度±0.01ppm以内)を用いた新たな計測装置を開発した。分析計の出力とCO_2濃度を関係づけるための標準ガスは, キャリアーガス効果の補正を必要としない空気と二酸化炭素の混合気体とし, その濃度は重量法によって絶対精度±0.1ppmで製造した特殊ガスを用いて検定された。, A new apparatus for in situ continuous measurements of atmospheric CO_2 concentration at Syowa Station, Antarctica was developed using a non-dispersive infrared CO_2 analyzer with a precision better than ±0.01ppm. Standard gases employed were CO_2 in air mixtures and their concentrations were determined against special gases with absolute accuracies around ±0.1ppm, which were prepared gravimetrically using an extremely precise balance.

A new method is proposed for the calibration of the sunphotometer. Well-known difficulties of the usual Langley-plot method when applied to unsteady turbidity conditions can be avoided by monitoring the circumsolar radiation. To realize this idea, an alternate of the Langley-plot method is developed, in which the logarithm of the sunphotometer reading is plotted against the ratio of intensity of singly scattered circumsolar radiation to that of direct solar radiation instead of the optical air mass in the usual Langley-plot method. Results of numerical simulations and field tests with a newly developed instrument show that the rms error of the calibration constant could be reduced to 1/5–1/10 of the usual method for wavelengths larger than 500 nm.

Atmospheric CF_2Cl_2,CFCl_3 and N_2O were measured by a gaschromatographic method in order to assess the influence of these gases on the stratospheric ozone. Air samples were successively obtained by the 24th and 25th Japanese Antarctic Research Expeditions. From Tokyo to Syowa Station, volume mixing ratios of CF_2Cl_2 and CFCl_3 decreased toward the equator and were almost constant in the southern hemisphere. This is because most of CF_2Cl_2 and CFCl_3 have been released in the northern hemisphere. Volume mixing ratios of CF_2Cl_2 and CFCl_3 at Syowa Station as of January 1983 were lower by 6% than mean volume mixing ratios of them over Japan from October 1982 to February 1983. As for N_2O, no gradient in mixing ratio from Tokyo to Syowa Station was found. The mean value of total 19 samples was 302 ppb (=(10)^v/v). Over the period between February 1982 to January 1984,CF_2Cl_2 and CFCl_3 showed a steady increase at Syowa Station, and their annual increases were 19.2 ppt (=(10)^v/v)/year for CF_2Cl_2 and 10.2 ppt/year for CFCl_3. In the same period, N_2O was almost constant.