What have we Learned from ACE-Asia? The ACE-Asia Science Team Tim Bates (NOAA PMEL), Phil Russell (NASA Ames), and Barry J. Huebert Department of Oceanography University of Hawaii Honolulu, HI USA B.Huebert, ACE-Asia, 03/03

Characterization : Determine the physical, chemical, and optical properties of the major aerosol types in the Eastern Asian and Northwest Pacific region and investigate the relationships between these properties. 1. How do the aerosol chemical, physical, and optical properties change with altitude, location, and time in Asia? 2. How absorbing are Asian dust and pollution aerosols? 3. How do the size and light scattering by Asian aerosols change with relative humidity? B.Huebert, ACE-Asia, 03/03

Radiation : Quantify the interactions between aerosols and radiation in this region. 4. With what accuracy can in situ measurements be integrated over the depth of the atmosphere to predict the observed radiative effects? 5. How much quantitative information about aerosols and their radiative impacts can be derived from satellites and other remote sensors? 6. What is the radiative forcing by Asian aerosols and how does it change with emissions, time, and distance from the continent? B.Huebert, ACE-Asia, 03/03

Processes : Quantify the physical and chemical processes controlling the evolution of the major aerosol types and of their physical, chemical, and optical properties and incorporate these into improved models. 7. Are the available source inventories for Asian primary aerosols and gas-phase precursors sufficiently realistic to support assessments of control strategies? 8. How are aerosol properties and dynamics modified by the uptake of gases? B.Huebert, ACE-Asia, 03/03

1. How do aerosol chemical, physical, and optical properties change with altitude, location, and time in Asia? Dust acts like a sponge, soaking up pollutant gases and aerosols. Complex aggregate of soot, mineral particles (upper), and a non-soot particle. Many different forms of soot stuck on a particle of quartz (SiO 2 ). These SEM micrographs by Jim Anderson (ASU) show the way soot balls (pollution) coat mineral dust particles B.Huebert, ACE-Asia, 03/03

Toxic metals become attached to dust even quite close to dust sources (data from Zhenbeitai, PRC) B.Huebert, ACE-Asia, 03/03 Arimoto, Zhang, Kang, Huebert, Savoie, Prospero, Sage, Schloesslin, and Khaing, Chemical composition of aerosols from Zhenbeitai, People's Replublic of China and Gosan, South Korea observed during ACE- Asia, J. Geophys. Res., in prep (ACE-Asia Special Issue B), 2003.

SO 2 and Scattering Profiles Courtesy of Blomquist, UH; Bandy, Drexel; Masonis & Anderson, U. Washington B. Huebert, ACE-Asia, 03/03 Not all layers are the same: some dust layers are more modified by pollution than others. SO 2 and dust co-exist from 4-5 km, but dust has scavenged all SO 2 from the 3-4 km layer. Blue = Total Scatt Green= <1um Scatt Red = SO 2 D D D P P P D C-130 sounding over Yellow Sea

Light absorbed by aerosols is highly variable regionally. Unpolluted Asian dust does not absorb much as we expected. B.Huebert, ACE-Asia, 03/03 The perception of how much light dust absorbs is changing rapidly! Anderson, Masonis, Covert, Ahlquist, Howell, Clarke, and McNaughton, Variability of aerosol optical properties derived from in-situ aircraft measurements during ACE-Asia, J. Geophys. Res., Submitted (ACE- Asia Special Issue), Courtesy P. Quinn (NOAA-PMEL) and S. Masonis (UW) Replotted by BJH Co-albedo is the fraction of light extinction due to absorption. (The balance is scattering.) 2. How absorbing are Asian dust and pollution aerosols?

The Mass Absorption Efficiency of soot is controversial. Ron Brown data argues that MAE ~ 9 m 2 /g for PM-10 Their MAE ~ 12 m 2 /g for PM-1 With Mie theory it is hard to explain MAEs larger than about 10 m 2 /g B.Huebert, ACE-Asia, 03/03 Quinn, Bates, Coffman, Miller, Covert, and Welton, Marine boundary layer aerosol optical properties during ACE Asia as a function of aerosol source region, J. Geophys. Res., ACE-Asia Special Issue B, 2003.

By contrast, BC encountered by the C-130 often had a Mass Absorption Efficiency (MAE) less than 10 m 2 /g. B.Huebert, ACE-Asia, 03/03 Bertram, Huebert, Howell, Eatough, Masonis, Anderson, Blomquist, and Heath, Organic and elemental carbon vs altitude during ACE-Asia, J. Geophys. Res., in prep, 2003.

When we sort the C-130 MAE to eliminate high-dust cases, the remaining data shows the clear impact that coating materials (OC and NSS) have on the MAE of soot Bertram, Huebert, Howell, Eatough, Masonis, Anderson, Blomquist, and Heath, Organic and elemental carbon vs altitude during ACE-Asia, J. Geophys. Res., in prep, (OC+NSS)/EC MAE, m2/g B.Huebert, ACE-Asia, 03/03

3. How do the size and light scattering by Asian aerosols change with relative humidity? Aerosol Optical Properties Show Broad Diversity with Aerosol Type Controlled RH Nephelometry showed that hysteresis plays a large role. Carrico, Kus, Rood, Quinn, and Bates, Mixtures of pollution, dust, seasalt and volcanic aerosol during ACE-Asia: Aerosol radiative properties as a function of relative humidity, J. Geophys. Res., Submitted (ACE-Asia Special Issue), B.Huebert, ACE-Asia, 03/03

How do the size and light scattering by Asian aerosols change with relative humidity? This is also controversial, since the surface and the airborne measurements give different values. The table below is from four fly-by comparisons: Courtesy Sarah Masonis et al. B.Huebert, ACE-Asia, 03/03

Schmid, Hegg, Wang, Bates, Redemann, Russell, Livingston, Jonsson, Welton, Seinfeld, Flagan, Covert, Dubovik, and Jefferson, Column closure studies of lower tropospheric aerosol and water vapor during ACE-Asia using airborne sunphotometer, airborne in-situ and ship-based lidar measurements, J. Geophys. Res., submitted (ACE-Asia Special Issue), With what accuracy can in situ measurements be integrated over the depth of the atmosphere to predict the observed radiative effects? Sun photometer extinction was modeled from Twin Otter composition and size data. The results were good except when large particles (dust or sea salt) were present. The C-130 LTI-derived size and composition data does not have this coarse particle disagreement, perhaps due to the LTI inlet (Redemann et al., 2003). B.Huebert, ACE-Asia, 03/03

Elevated layers of coarse dust Fine pollution aerosols near the surface Radiation column closure has been used to infer  0 and   550 (or SSA) ≈ near surface, (less absorbing) aloft  (wavelength dependence) is larger for pollution than dust B.Huebert, ACE-Asia, 12/02Huebert, ACE-Asia, 03/03

5. How much quantitative information about aerosols and their radiative impacts can be derived from satellites and other remote sensors? Coordinated Flights C-130 Twin Otter MODIS96 MISR64 MISR/LM3unk SeaWiFS78 NOAA-1422 NOAA-164 We have a rich data set of in situ profiles in satellite scenes B.Huebert, ACE-Asia, 03/03

AOD is often derived from satellites How good is this retrieval? B.Huebert, ACE-Asia, 03/03

Courtesy Schmid, Hsu et al. Comparison of the SeaWiFS algorithm with airborne Sun Photometer data suggests there is room for improvement… B.Huebert, ACE-Asia, 03/03 Many more satellite studies are underway… B.Huebert, ACE-Asia, 03/03

Lidar remote sensing During a period in which the C-130 flew as close as possible to the Tokyo-area lidars, remarkable agreement was found between the TUMM Lidar, in situ extinction (PSAP & Nephelometer), and the AATS-6 Sun Photometer. Disagreement in the BL may be due to spatial variability in the metropolitan area. Murayama, et al., An intercomparison of lidar-derived aerosol optical properties with airborne measurements near Tokyo during ACE-Asia, JGR, B.Huebert, ACE-Asia, 03/03

Combining the SeaWiFS data and ACE-Asia in situ aerosol optical properties allows us to estimate the direct surface aerosol forcing: about -30 w/m2, large and negative (cooling) B.Huebert, ACE-Asia, 03/03 6. What is the radiative forcing by Asian aerosols and how does it change with emissions, time, and distance from the continent?

“… monthly mean…aerosol direct effect… from a satellite method -2 to -4 W/m 2 at TOA and -20 to -70 W/m 2 at surface, … large regional difference caused by…AOT and SSA. “However … direct forcing … strongly depends on the estimation method of the aerosol properties, especially on the SSA. SPRINTARS aerosol model generates SSA values larger by 0.1 than surface-measured values, so that the modeled direct forcing at surface ranges from -3 to -10 W/m 2 which are significantly smaller than those from satellite method. “…aerosol indirect effect is estimated from satellite method and SPRINTARS model as -1 to -3 W/m 2 at both TOA and surface.” Nakajima, T., and APEX Science Team, Significance of direct and indirect radiative forcings of aerosols in the East Asian region, JGR, B.Huebert, ACE-Asia, 03/03

Bush and Valero, Aerosol Radiative Forcing at Gosan during the ACE-Asia campaign, J. Geophys. Res., submitted (ACE-Asia Special Issue), From radiative flux measurements at Gosan: “The diurnal forcing efficiency was determined to be –73.1, -36.3, and – 41.7 Wm -2 /  500 for the total solar, near-infrared, and visible spectral regions.” “… a larger percentage of the flux at visible wavelengths is radiatively forced compared to the total and near-infrared portions of the solar spectrum.”

Our Observations of Asian Dust Have Already Improved Emissions inventories in models SeaWiFS Courtesy NASA and Orbimage We Found More Than 1000 µg/m3 of Dust in the Yellow Sea. Models had not included a drought-stricken region in Liaoning Province, which can now be a source of dust to Korea and Japan 7. Are the available source inventories for Asian primary aerosols and gas-phase precursors sufficiently realistic to support assessments of control strategies? B.Huebert, ACE-Asia, 03/03

BC Modeling issues “… it appears that the emission estimates of BC are qualitatively correct. “… emissions from Japan may be underestimated “… under predicting BC levels at low altitudes in the Yellow Sea [Carmichael et al., 2002]. “… reported BC values are very dependent on the analysis method. “… how best to use the surface data in the constraint of BC emission estimates. “… much of the flux of BC occurs at altitudes well above the surface layer. “… we do not have sufficient information upon which to constrain wet and dry removal fluxes of BC.” B.Huebert, ACE-Asia, 03/03 Uno, Carmichael, Street, Satake, Takemura, Woo, Uematsu, and Ohta, Analysis of surface black carbon distributions during ACE-Asia using a regional scale aerosol model, J. Geophys. Res., in press (ACE-Asia Special Issue), 2003.

The ACE-Asia & TRACE-P observations are helping to reduce these uncertainties. Huebert et al., (ACE-Asia JGR Overview) taken from Streets et al., JGR, 2003 B.Huebert, ACE-Asia, 03/03

C-130 MOI data: Dust can modify pollutant chemistry and become coated with hygroscopic salts in the process. NSS B.Huebert, ACE-Asia, 03/03 8. How are aerosol properties and dynamics modified by the uptake of gases? Kline, Huebert, Howell, Bertram, Blomquist, Zhuang, and Heath, Chemical and physical size distributions vs altitude during ACE-Asia, J. Geophys. Res., in prep (ACE-Asia Special Issue B), 2003.

Was SO 2 adsorbed by the alkaline dust, or was some of this large-particle sulfate from gypsum at the source? Was HNO 3 adsorbed, or was some Ca(NO 3 ) 2 from fertilizer? Clearly most NO 3 - was coarse and most SO 4 = was fine. But what were their origins? B.Huebert, ACE-Asia, 03/03 Kline, Huebert, Howell, Bertram, Blomquist, Zhuang, and Heath, Chemical and physical size distributions vs altitude during ACE-Asia, J. Geophys. Res., in prep (ACE-Asia Special Issue B), 2003.

What unknowns remain? Why do the some values from surface sites and the C-130 differ? Is it a measurement problem or a real difference? B.Huebert, ACE-Asia, 03/03 Sarah Masonis Harmony paper

What unknowns remain? Need better total aerosol mass measurements, esp in dust Need to standardize BC/EC measurements Need to standardize many other measurements, too! Need profile (airborne) measurements near dust source regions Need evolution observations …and many more... etc. B.Huebert, ACE-Asia, 03/03

What have we learned from ACE-Asia? 1. Air pollution changes dust aerosols in many ways, adding black carbon, toxic materials, and acidic gases to the mineral particles. These change its impact on health, climate, and the delivery of nutrient iron to the remote Pacific ocean. 2. The dust that goes from East Asia to the Pacific does not absorb nearly as much light as the dark aerosol from South Asia or some previous Saharan dust data. There are dramatic regional differences in the optical properties of aerosols. 3. Combining ACE-Asia suborbital and satellite measurements yields monthly average (April 2001), cloud-free aerosol radiative forcing at the surface in ACE-Asia exceeding -30 W m-2 in a plume downwind of Japan and in the Yellow Sea, East China Sea, and Sea of Japan. B.Huebert, ACE-Asia, 03/03

ACE-Asia Ship and Aircraft Platforms B.Huebert, ACE-Asia, 03/03

>100 Scientific Groups 13 Countries China, Japan, South Korea, Chinese Tapiei, USA, Canada, France, Germany, Australia, UK, India, Russia, Netherlands >35 Funding Agencies Surface Sites >30 in Japan, China, Korea, Chinese Taipei, Hawaii Forecast Models MATCH, NCAR CFORS, Kyushu/Iowa GOCART, Goddard Satellites TERRA SeaWiFS AVHRR GMS Aircraft NSF/NCAR C-130 CIRPAS Twin Otter ARA KingAir Ships R/V Ron Brown R/V Mirai Lidars ADNet, in Japan, Korea, China SABLE on C-130 ACE-Asia Participants and Resources B.Huebert, ACE-Asia, 03/03

ACE-Asia Network Observations: B.Huebert, ACE-Asia, 03/03 Courtesy PMEL

Source: IPCC Third Assessment Report Understanding Climate: Aerosol Forcings Cause the Largest Uncertainty in the Earth’s Radiation Budget B.Huebert, ACE-Asia, 03/03 Source: IPCC Third Assessment Report

Instrument Intercomparisons - Harmony How confident can we be of any given measurement? C-130 Ron Brown Twin Otter Kosan KingAir: 1 P-3: 2 B.Huebert, ACE- Asia, 03/03

Harmony - what can we learn from it? Courtesy Sarah Masonis et al. B.Huebert, ACE-Asia, 03/03 1. The certainty that any individual number represents a region 2. The uncertainty in average quantities from each platform These are very different things.