Preliminary Aerosol Climatology for the Pacific Boundary Layer and Free Troposphere
Antony D. Clarke, PI
Vladimir Kapustin, Co-PI
David Covert, Adjunct PI
Abstract:
We propose to combine and interpret extensive aerosol size distribution
data collected during the past decade around the Pacific Basin in order to
develop a preliminary climatology of aerosol microphysics for the
Pacific troposphere. This includes aircraft, ship and ground based data
collected as part of our numerous field experiments supported by NASA,
NOAA and NSF. Although these experiments frequently had diverse goals,
most included extensive data on aerosol size distributions, optical
properties (light scattering and light absorption) and chemistry. In
general, only small portions of these data sets have been published with
limited objectives in mind. We propose to assemble the aerosol data in
order to provide spatial, temporal and regional characterization of
aerosol fields over the North and South Pacific. Aircraft vertical
profiles (about 100) of aerosol size distributions and light-scattering
(often for both coarse and fine aerosol at 4 wavelengths) will be used to
characterize vertical structure and to link it to concurrent satellite
retrievals of column aerosol optical depth. Some airborne experiments
(GLOBE, ACE1) also allow us to extend in-situ aerosol measurements in
order to compare and interpret aerosol fields in the troposphere
characterized concurrently by airborne lidar.
We propose to put our in-situ data in context and to identify links to
regional meteorological regimes and processes. Size resolved
aerosol types will include dust, pollution, sea-salt, sulfates and
clean cloud-processed air. Characteristics will be identified that are
associated with meteorological regimes in the Pacific such as the
westerlies, subtropical trade-wind and equatorial regions.
Interhemispheric differences will be identified as well as transitional
boundaries established by the Intertropical Convergence Zones (ITCZ) and
the South Pacific Convergence Zones (SPCZ). Aircraft data will extend
this characterization to altitudes of 6 to 10km depending upon the
specific flight missions over the Pacific (about 1 month each) that we
have participated in (GLOBE1, GLOBE2, CPACE, ACE1, PEM-Tropics).
Shipboard data for the marine boundary layer include more than 200 days at
sea from our cruises during SAGA1, SAGA2, SAGA3, RITS88, RITS93, RITS94, ACE-1.
We will focus on aerosol sizes of immediate consequence to radiative
transfer (direct effect) but will also characterize smaller aerosol sizes
whose behavior is often associated with the source, transport and removal
of aerosol. We believe that this will help link regional aerosol
characteristics to those processes that shape the size distribution as
well as its optical properties. Regional aerosol size and optical
parameters will be described suitable for modeling purposes and placed in
a meteorological context. Thes will be made available both to NASA and/or
as an accessible database on our website. Key observations and an overview
paper would also be prepared.
