range transport of dust and anthropogenic aerosols (e.g, black carbon,
organics and sulfates, and air pollution from Eurasia, across
the Pacific Ocean, into North America is one of the most wide spread
and major pollution
events on the planet. This plume passes through the Pacific Ocean
tropical cloud systems, which are important climate regulators through
their large radiative cooling
effect. The effect of this mixed dust-pollution plume on the
Pacific cloud systems and the associated radiative forcing is an
outstanding problem for understanding climate change and has not been
explored. The primary reason is the lack of an airborne platform
that can sample the evolution of this plume in situ all the way across
the Pacific Ocean.
The NSF/NCAR Gulfstream-V research aircraft (G-V) fills
observational gap and opens new doors for observing this great
natural/man made phenomenon. PACDEX plans for a pilot study
using Lagrangian sampling of this Eurasian-Pacific-North American dust
plume. We will observe the evolution of the aerosol physical and
chemical characteristics from the lower to the upper troposphere, the
vertical and horizontal gradients in the CCN and ice nuclei across the
Pacific, and cloud size spectra and liquid and ice water content.
This pilot experiment is designed to exploit and demonstrate the unique
capabilities of the G-V. PACDEX has the potential to open new frontiers
of science by observing human impacts on the mixed-phase and ice-phase
cirrus cloud systems.
PACDEX Field Campaign
The PACDEX Field Campaign has concluded its flight operations
from the Field Operations Planning Meeting on Feb
Agenda from the
Field Operations Planning Meeting
will be the focus
of this pilot experiment:
- Identification of the principal cloud-active aerosol
in the Asian plume. This will be
done using the CCN measurements and the IN measurements together with
basic aerosol package on the G-V.
- Document the changes in the cloud hydrometeor size
spectra in regions of enhanced
cloud active aerosol. This is within the limited capabilities of this
payload and is the first observational step needed to understand the
impact of the
Asian plume on clouds.
- Document the solar changes in the plume
vertical structure in clear air and cloudy
- Document near source and far from source
changes in the plume that might affect (a),
(b) and (c). While the sampling cannot be truly Lagrangian, due to the
wind shear over the depth of the plume, we can identify regions with
using trajectory analysis and model simulations.
- Compare the in-situ vertical structure observed from
the aircraft upwind and near the ground stations.
EOL Efforts in PACDEX
deploying the NSF/NCAR
Gulfstream-V research aircraft.
This airborne study requires several mission-critical measurements.
these will be available as user-requestable resources from NCAR/EOL,
and others will be
provided by project investigators
The key measurements include:
Trace gases that
identify clean and polluted
Aerosol physical properties (total number concentration
chemical composition (dust, black carbon, sulfates and organics (if
characterization of cloud active nuclei (CCN, giant nuclei, and ice
aerosol light scattering and absorption.
Cloud microphysical properties - basic measurements for
precipitation size spectra, water and ice content, including a CVI for
content and residual particle composition.
A radiation package that provides adequate
characterization of the
radiative impact of
the plume and clouds at least in the solar part of the spectrum.
covering wavelengths from about 0.3 µm to 3 µm are required
to cover the direct
impact of the Asian plume. The focus of PACDEX airborne
will be on the solar portion of the spectrum, which is well sampled by
G-V instrumentation. Additional instrumentation to measure the
may also be pursued, but is not part of the current
Real-time communication from the G-V to the ground via
communications for data
Last update Mon 14 May 2007
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