A11B-0376
Dust Storm over Eastern Asia during PACDEX 2007
Dust storm cases are analyzed based on surface observed data for the period of PACDEX 2007. There were 10 large¡§Cscale dust storms, 6 cases occurred in Mongolia and 4 cases in Taklimakan desert (Tarim Basin). The incidence of these dust storms spread to Mongolia, the Northern China, Yellow Sea, Peninsular of Korea, Southern Japan and the Pacific Ocean over southeast Japan. Three sources of dust outbreak are found, i.e., Western Mongolia, middle region of Mongolia and Taklimakan desert. The Northwest path, on which the dust storm moved to the Pacific Ocean over southeast Japan, and the West path, on which the dust storm affected only on local area, are two major transfer paths. Most Taklimakan dust storms only affect on the region of desert. But, the Mongolia dust storms are serious one, and the intensity varied during the process of movement. Developing cyclones is the major synoptic systems for caused Mongolia dust storm. Those dust storms can be enhanced when the cyclone developed to a deeper front cyclone, and moved toward south-east led by upper jet flow. The dust storm in Taklimakan desert was induced by cold high, with cold air moving into Tarim Basin from its east gate or climbed over Tianshan Mountain and rushed down to the basin.
A11B-0377
Single particle ATOFMS measurements of the chemical and physical properties of polluted and fresh air masses in Gosan, Korea
Real-time single particle mass spectrometry measurements were made during the Pacific Dust Experiment (PACDEX) to gain insight into the size-resolved aerosol mixing state at the Aerosol Brown Cloud Monitoring Station in Gosan, Korea. During the one month sampling period during April and May 2007, there were several distinct time periods with different sources contributing significantly to the observed aerosol. The different events include outflow from the Asian continent, a minor Asian dust event, clean marine periods, and episodes of local influence. The aerodynamic size and chemical composition of individual particles were measured in real time using an aerosol time-of-flight mass spectrometer (ATOFMS). This information provides insight into the sources of the aerosol during these different periods. The mixing state and light scattering properties obtained from the scattering signal recorded by the ATOFMS allow information regarding the radiative properties of distinct chemical classes to be determined. The data from the ATOFMS along with concurrent measurements of particle number concentration, size distribution, bulk scattering, and black carbon mass concentration provide broad insight into the evolution of the polluted air masses. Within the different air masses, the distinct particle types observed include fly ash, elemental carbon, dust, sea salt, and vanadium types. Processed and agglomerated particle types, such as elemental carbon with sea salt and elemental carbon with dust, were also observed and are thought contribute significantly to the radiative properties of the air mass. Particle aging was assessed using nitrate, sulfate, and ammonium. From these measurements information regarding different sources contributing to Asian outflow was determined. This information is necessary for understanding Asian outflow events. The mixing state of chemically different particle types and their associated light scattering properties observed by ATOFMS measurements are shown. The demonstrated variability of scattering properties within both the fresh and aged aerosol demonstrates the need to include these findings in future global climate models for complete evaluation of the earth's radiation budget.
A11B-0378
Airborne Measurements of Aerosol Size Distributions During PACDEX
The Pacific Dust Experiment (PACDEX) is an airborne project that attempts to characterize the indirect aerosol effect by tracing plumes of dust and pollution across the Pacific Ocean. This project occurred during April-May 2007 and used the NSF/NCAR HIAPER research aircraft. When a period of strong generation of dust particles and pollution was detected by ground-based and satellite sensors, then the aircraft was launched from Colorado to Alaska, Hawaii, and Japan. Its mission was to intercept and track these plumes from Asia, across the Pacific Ocean, and ultimately to the edges of North America. For more description, see the abstract by Stith and Ramanathan (this conference) and other companion papers on PACDEX. The HIAPER aircraft carried a wide variety of sensors for measuring aerosols, cloud particles, trace gases, and radiation. Sampling was made in several weather regimes, including clean "background" air, dust and pollution plumes, and regions with cloud systems. Altitude ranges extended from 100 m above the ocean to 13.4 km. This paper reports on aerosol measurements made with a new Ultra-High Sensitivity Aerosol Spectrometer (UHSAS), a Radial Differential Mobility Analyzer (RDMA), a water-based CN counter, and a Cloud Droplet Probe (CDP). These cover the size range 10 nm to 10 um diameter. In clear air, dust was detected with the UHSAS and CDP. Polluted air was identified with high concentrations of carbon monoxide, ozone, and CN. Aerosol size distributions will be presented, along with data to define the context of weather regimes.
A11B-0379
In-Situ Measurements Of Air Pollution Over China Loess Plateau During PACDEX
Ground measurements of trace gases and mass concentration of dust aerosols were obtained from April 19 to May 31, 2007 at an integrated observational site of China (35.57N,104.08E), which is about 48 km away from the centre of Lanzhou city. The site is located at the southern bank of Yellow River in Gansu province, northwestern China, just on the so-called China-loess Plateau with an elevation of about 1965.8 m above sea level. The instantaneous volume mixing ratios of CO, SO2, NOx and O3 are measured continuously along with the size distribution of atmospheric aerosols in the 10 nm diameter range. Average mass concentration of black carbon is also collected during this experiment. The light scattering coefficients measured derived from single-wavelength nephelometer for 450, 520, 700nm. Overall, there is a very good agreement between scattering coefficients and PM10 for the time period observations, especially during dust events. The objective of this study is to understand the detailed characteristics and underlying mechanisms of air pollution in Lanzhou and its potential impacts on the regional/global climate. Preliminary analysis shows that the hourly mean volume mixing ratios of O3, CO, SO2, NOx are 48.67 ppb, 609.12 ppb, 8.10 ppb, and 6.89 ppb£¬respectively. During a dust storm event, the mass concentration of particulates (PM10) can rise to 2484.72 ug/m3, about 13 times as high as that in non-dust storm days. Dust plumes are transported from the surface to a long distance from their sources and have a significant influence on regional air quality in this region. The meteorological analysis indicates that these polluted layers are not from local sources. http://climate.lzu.edu.cn/~jhuang/people/wx/Xin_Wang.htm
A11B-0380
Dusty Cloud Properties Determined from Surface and Satellite Observations over Asia during PACDEX
In this study, the optical and radiative properties of dusty clouds (clouds formed in dusty air) over Asia are analyzed using A-Train satellite radiances and surface measurements during the Pacific Dust Experiment (PACDEX). The dusty clouds are identified by the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite and surface lidar measurements. Significant differences are found in the cloud optical depth, effective particle size, liquid water path and radiative forcing between the dusty and dust-free clouds. The water paths of dusty clouds are considerably smaller than those of dust-free clouds due to the semi-direct effect of dust aerosol. The net radiative forcing at the top of atmosphere (TOA) for dusty clouds is reduced compared to that for dust-free clouds. The reduced cooling effects may lead to a net warming. The semi-direct effect may be dominated by the interaction between dust aerosols and clouds over arid and semi-arid areas and partly contribute to reduced precipitation.
A11B-0381
Balloon borne measurements of aerosol and cloud particles over Japan during PACDEX
This paper presents the preliminary result of the balloon borne measurements of the aerosol and cloud microphysical properties over Tsukuba (36.1°N, 140.1°E), Japan, on 10 and 22 May 2007. The purpose of the measurement is to study the influence of Asian mineral dust on ice clouds formation in the middle and upper troposphere. The balloon measured the vertical distributions of aerosol number size distribution (0.13 to 3.9 μm in threshold radius, 8 sizes) by use of the optical particle counter, cloud size (10 μ m to 5 mm in the longest dimension), shape, and number concentration by use of the hydrometer videosonde, humidity by use of SnowWhite hygrometer, and temperature and pressure by use of Meisei RS-01G radiosonde between altitudes of 0 and 16 km. The aerosol size distribution showed bimodal distribution with mode radii of <0.13 μm (fine mode) and about 0.8 μm (coarse mode) over the troposphere (0-13.5 km in altitude). The number concentrations ranged from 150 to 1 cm-3 in the fine mode and from 3 to 0.1 cm-3 in the coarse mode. High depolarization ratio (>10%) obtained from the ground-based Raman lidar measurement revealed the presence of nonspherical dust in the coarse mode. Columnar, bullet-like, and irregular ice crystals with 10-400 μm in size were detected between altitudes of 8 and 13 km on 10 May and 10 and 13 km on 22 May. The maximum crystal concentration was 0.15 cm-3. We discuss the possibility of the formation of the ice cloud from the dust based on the result of the measurements.
A11B-0382
Single-particle black carbon measurements during PACDEX
The single particle soot photometer (SP2) uses laser incandescence to measure black carbon (BC) particle mass and concentration. In the PACific Dust EXperiment (PACDEX), the SP2 flew on the NCAR G-V aircraft sampling outflow of dust and pollution from Asia. Preliminary results from different PACDEX flights will be presented, with the focus on ambient aerosol measurements. On May 2, 2007, vertical profiles of black carbon were obtained in pollution plumes and background air to the east of Japan. A series of vertical steps showed layers of black carbon at and between 3.7 and 5.6 km above sea level (ASL). BC varied from under 100 ng/m3 to over 400 ng/m3. Typically, 6-8% of the particles detected by the SP2 contained black carbon. Most BC-containing particles appeared to have a significant non-BC component in addition to the BC mass, indicating internal mixing throughout this layer. Number size distributions based on the BC mass/particle, expressed as the incandescent mass-equivalent diameter, suggest two modes, one with particles that contain about 0.5 fg-BC each and a broader peak of particles that contain 2-9 fg-BC each. Most of the BC mass was contained in aerosol with 6-9 fg- BC/particle. Similar characteristics were observed for BC in a layer between 3.7-5 km ASL 350 nautical miles south-southeast of the first region, with BC mass concentrations also ranging from under 100 ng/m3 to almost 400 ng/m3. The similarity of BC concentrations, number fractions and mixing state at these two widely-separated locations could indicate that it was the same plume, spread over a large area. At the northeastern end of the flight path box, the air mass appeared cleaner, with BC concentrations around 50 ng/m3 between 5.5-8 km ASL.
A11B-0383
Ship Measurements of the Submicron Aerosol Size Distributions Over the Yellow Sea and East China Sea in 2005
As part of the Atmospheric Brown Cloud-East Asian Regional Experiment (ABC-EAREX) 2005 campaign, submicron aerosol size distribution (10 nm < particle diameter, Dp < 300 nm), number concentration (Dp > 10 nm) and meteorological parameters were measured over the southern sea of the Korean Peninsula and Yellow Sea on board the research vessel Kisang2000 during March 2nd-3rd and March 8th-10th, respectively. The average number concentration was 5511 cm-3 for the southern sea cruise and 7590 cm-3 and 5111 cm-3 for the northward and southward cruise over the Korean sector of the Yellow Sea, respectively. The minimum concentration for the whole campaign was 837 cm-3. The average geometric mean diameter was 74.9 nm, 67.2 nm and 60.3 nm, respectively. During the cruise the vessel had gone through various kinds of meteorological conditions including clear sky and thick fog. Such different conditions gave way to different aerosol phenomena, i.e., the particle formation event took place in one region while it wasn¢¢ç¯t the case for other regions on a same day. Another ship measurement was conducted over the East China Sea during September 8th-9th and 13th-14th while cruising from Jeju Island, Korea to Shanghai, China and from Shanghai to Jeju Island, respectively. The same aerosol instruments were used as the previous campaign but meteorological parameters was not measured this time. The average concentration was 3650 cm-3 and 5413 cm-3 for each cruise. The minimum concentration (1025 cm-3) was recorded at the mid-point of the cruise track where the distance to the land mass was the farthest from either direction, suggesting that the distant from either coast was the main factor influencing the aerosol concentration. The average geometric mean diameter was 77.4 nm and 62.9 nm for the two cruises, respectively. The weather was fairly calm for both cruises. According to the back trajectory analysis, the duration for which the air mass had stayed over the continental region before reaching the measurement location was rather a minor factor. Further analyses in association with weather conditions and air mass back trajectories will be presented at the conference.
A11B-0384
Ground Level Ozone Regional Background Characteristics In North-west Pacific Rim
Understanding the ground level ozone regional background characteristics is essential in understanding the contribution of long-range transport of pollutants from Asia Mainland to air quality in downwind areas. In order to understand this characteristic in north-west Pacific Rim, we conducted a coupled study using ozone observation from regional background stations and 3-D regional-scale chemical transport model simulations. We used O3, CO, wind speed and wind direction data from two regional background stations and ¡§other stations¡¨ over a ten year period and organized several numerical experiments to simulate one spring month in 2003 to obtain a deeper understanding. The so called ¡§other stations¡¨ had actually been named as background stations under various governmental auspices. But we found them to be often under strong influence of local pollution sources with strong diurnal or slightly longer time variations. We found that the Yonagunijima station (24.74 N, 123.02 E) and Heng-Chuen station (21.96 N,120.78 E), about a distance of 400 km apart, have almost the same ozone time series pattern. For these two stations in 2003, correlation coefficients (R2) for annual observed ozone concentration is about 0.64, in the springtime it is about 0.7, and in a one-month period at simulation days it is about 0.76. These two stations have very little small scale variations in all the variables studied. All variations are associated with large scale circulation changes. This is especially so at Yonagunijima station. Using a 3-D regional-scale chemical transport model for East Asia region including contribution from Asia continental outflow and neighboring island pollution areas we found that the Yonagunijima and HengChuen station are indeed free of pollutants from all neighboring areas keeping in mind that pollutants from Taiwan area is never far away. Ozone concentrations in these two stations are dominated by synoptic scale weather patterns, with diffused pollutant contribution from distant sources. When the weather system brings in air mass from the low latitude of western Pacific Ocean, ozone concentrations are about 10-20 ppb. When the China high pressure system moves eastward and with the accompanying Asian continental outflow plume, ozone concentrations are about 65-80 ppb.
A11B-0385
Gas phase tracer analysis of air sampled during the Pacific Dust Experiment (PACDEX)
In April and May, 2007, the Pacific Dust Experiment explored transpacific transport of gas and aerosol species, with a focus on interactions of air parcels with clouds. Plumes containing dust and anthropogenic signatures were tracked from Tokyo to the North American West coast in order to study the evolution of composition. As a starting point in analysis of this data set, gas phase tracer fields are analyzed to identify intervals of free tropospheric long-range transport of relatively unreactive and insoluble gas phase constituents from Asian to North American mid-latitudes.
A11B-0386
Long-range transport its effect on cloud condensation nuclei over the Pacific Ocean
Dust and anthropogenic emissions from Asia traverse the Pacific Ocean and intercept North America within a week during the spring months when storm and frontal activity is most intense. The Intercontinental Chemical Transport Experiment – Phase B (INTEX-B), which occurred in April 2006, focused on the transport and transformation of gases and aerosols on transcontinental/intercontinental scales. Airborne measurements during INTEX allow nearly complete characterization of the physicochemical properties of aerosol which allow an independent assessment of their mixing states and ability to act as cloud condensation nuclei (CCN). This size- resolved chemical information, in conjunction with measurements of aerosol size distribution, investigates the concept of activation indices, which relate the efficiency of an aerosol to serve as CCN based on the relative amount of water-soluble material. The Pacific Dust Experiment (PACDEX) in April-May 2007 also focused on direct measurements of long-range transport by following the plumes across the Pacific Ocean from Asia into North America, which demonstrated the unique capabilities of the HIAPER platform. During PACDEX, CCN measurements were made with a dual-column CCN instrument. During both experiments, we observed variety of aerosol layers during vertical and horizontal profiles, ranging from aged aerosols from major Asian dust storms to ultra-fine particles from recent nucleation events. Aerosols from a few hours to over a week old were sampled – including similar air masses at different stages during their transport. Aerosol layers observed were found throughout the Pacific Ocean in stratified layers ranging from altitudes of 1000 meters to 9000 meters. Size resolved chemical measurements indicate cloud processed aerosol in the boundary layer and both aged and ultra-fine layers aloft. Aerosols undergoing cloud processing activate close to an ammonium sulfate limit; while those with anthropogenic origins show lower activation efficiency which points to an insoluble or hydrophobic core (i.e., biomass burning or dust) that has been aged by deposition of a water-soluble material. In some flights, the evolution of the aerosols has been identified and changes in aerosol chemistry from aging or cloud processing are likely to have enhanced the cloud nucleating ability of these aerosols as results indicate an increase in soluble mass fraction from ca. 10% to 40%. Mixing states (i.e., internal vs. external mixtures) are important for interpreting the soluble fraction – and single particle analysis will shed light in this area. The results indicate that horizontal mixing during high-altitude long-range transport (above several kilometers) may be more significant than vertical mixing unless vigorous mixing brings the aerosol into the boundary layer.
A11B-0387
Some Measured Ice Concentrations in Pacific Clouds
The Pacific Dust Experiment (PACDEX) provided an opportunity to measure ice concentrations in clouds at locations from near Japan to near the continental U.S. and at altitudes from near the surface to above 40,000 ft. Because the flights of the NSF/NCAR Gulfstream-V sought to track pollution and dust events originating in China, aerosol conditions also varied greatly in regard to concentrations of total, dust, black carbon, and sulfate aerosol. The flights included studies of several frontal systems in cyclonic storms over the Pacific. This paper documents representative ice concentrations as encountered during this project, using measurements from a new (2D) hydrometeor probe modified to operate at Gulfstream-V flight speeds and to handle the associated higher data rates, and shows how such ice concentrations depend on altitude, temperature, distance from Asia, association with aerosol properties, and nature of the cloud systems.
A11B-0388
PACDEX From a Satellite Perspective
Satellite observations from the TOMS, OMI, and MODIS experiments are used to place the April-May 2007 PACDEX mission in both a historical and geographical perspective. TOMS monthly averaged aerosol optical depths for 1979-2000 indicate the well known fact that dust storms are most prevalent in April and May, and are used to quantify the time-averaged trans-Pacific gradient in aerosol optical depth. Aerosol optical depths are largest over the Taklimakan desert source region, with smaller contributions from the Gobi desert, in both the TOMS historical record and in April-May 2007 OMI observations. MODIS aerosol fine mode data indicate that larger particles are observed over land and smaller particles over the ocean. Finally, MODIS radiances are analyzed to relate 3.75 micron cloud reflectance to aerosol amount. The Twomey effect, in which increases in aerosol amount are associated with increases in cloud reflectance, is readily apparent over the Taklimakan desert, but less so over the Pacific.