A41B-01
Transport, Evolution and Entrainment of Asian Dust/Pollution into the Pacific Marine Boundary
Various airborne and ship based studies over the past several years have allowed us to measure Asian dust and pollution aerosol from near its source to locations up to 10,000km downwind where it was entrained into the marine boundary layer (MBL). Dust was found to accumulate up to half of the soluble species such as sulfate and nitrate during passage through pollution regions in Asia before being lofted into the free troposphere near Japan. At times, transport in the free troposphere included regions of subsidence in high pressure regions that brought these "rivers" of dust and pollution down to the top of the MBL. Shipboard measurements and lidar data indicated both clear air entrainment and convective activity, associated with the passage of low pressure systems, facilitated dust transport through the inversion. High temperature volatilization of particles in the MBL up to 900C was used to remove most sulfates, nitrates, carbon and sea-salt to leave only dust measured and sized by an optical particle counter. These shipboard data and concurrent chemical measurements revealed the relation between entrainment of pollution and dust into the MBL associated with passage of high pressure systems. Subsequent passage of low pressure systems also revealed scavenging and removal of aerosol through precipitation to the ocean surface. This process appears to be a common removal pathway for dust over the Pacific and a mechanism for supplying the ocean surface with soluble iron and aluminum to the ocean surface. Measurements in the free troposphere and MBL also captured various aspects of these processes. Airborne missions flown north of Hawaii during the NASA PEM-Tropics and IMPEX missions characterized the vertical structure of subsiding dust and pollution. In-flight mapping of the dust/pollution layers and structure using the NASA Langley DIAL LIDAR show a sloping, subsiding Asian air-mass entraining into the marine boundary layer (MBL). In-situ measurements of the aerosol size distribution, chemistry, optical properties and the increase in light scattering as a function of relative humidity [f(RH)] were able to characterize and discriminate between MBL air, FT Asian dust/pollution and an external mixture of the two air-mass types during entrainment. Dusty air-masses were transported from Asia to the Pacific Ocean north of Hawai`i via the free troposphere (FT) and were even evident as a pronounced event the NOAA Mauna Loa Observatory (19.54N, 155.58W, 3,397m alt.). In situ measurements confirmed that regional and global chemical transport models (CTM) successfully predicted several Asian dust/pollution outbreaks and subsidence into the MBL. One episode is put into broader context using models, satellite observations and data from the Mauna Loa Observatory. We include a discussion of dust-flux to the ocean surface due to wet-deposition, a potentially important source of iron to the oligotrophic waters of the North Pacific Subtropical Gyre.
A41B-02
Studying Role of Dust in Atmosphere-Ocean Interactions Using Giovanni
For dust events, properties of aerosols, clouds, water vapor, precipitation, and other atmospheric parameters
measured by Terra MODIS and Aqua MODIS, TRMM, AIRS, Aura OMI, and other space-based remote sensing
instruments are studied. More specifically, spatio-temporal correlations using available daily data are computed
using Giovanni (http:giovanni.gsfc.nasa.gov), the NASA Goddard online visualization and analysis tool. Also, the
high resolution data from CloudSat and CALIPSO, are used to study vertical structure of dust events. In addition,
sea surface temperature measured by Aqua MODIS and ocean color data measured by SeaWiFS and Aqua
MODIS, are studied in relevance to the above atmospheric parameters. Giovanni is demonstrated to serve as a
very convenient online tool for this inter-disciplinary multi-sensor field of studying how dust affects atmospheric
processes and marine environment.
http:giovanni.gsfc.nasa.gov
A41B-03
Quantifying the Impact of Dust on Tropical Atlantic Ocean Temperatures
This presentation will focus on linking sea surface temperature changes in the Atlantic with African dust activity through the radiative forcing associated with these plumes as they traverse the Atlantic. We will demonstrate that periods of cooler ocean temperatures are likely reinforced by radiative feedbacks associated with a coincident increase in dust activity. To do this we analyze 25 years of observations of aerosol optical thickness from the Advanced Very High Resolution Radiometer, climatological maps of mixed layer depths, and cloud diurnal cycles. While many factors alter Atlantic ocean temperatures, we aim to demonstrate that quantifying the sea surface temperature forcing by aerosols is needed to fully understand the interannual and multidecadal changes observed across the basin.