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Airborne Aerosol Closure Studies During PRIDEThe Puerto Rico Dust Experiment (PRIDE) was conducted during June/July of 2000 to study the properties of Saharan dust aerosols transported across the Atlantic Ocean to the Caribbean Islands. During PRIDE, the NASA Ames Research Center six-channel (380 - 1020 nm) airborne autotracking sunphotometer (AATS-6) was operated aboard a Piper Navajo airplane alongside a suite of in situ aerosol instruments. The in situ aerosol instrumentation relevant to this paper included a Forward Scattering Spectrometer Probe (FSSP-100) and a Passive Cavity Aerosol Spectrometer Probe (PCASP), covering the radius range of approx. 0.05 to 10 microns. The simultaneous and collocated measurement of multi-spectral aerosol optical depth and in situ particle size distribution data permits a variety of closure studies. For example, vertical profiles of aerosol optical depth obtained during local aircraft ascents and descents can be differentiated with respect to altitude and compared to extinction profiles calculated using the in situ particle size distribution data (and reasonable estimates of the aerosol index of refraction). Additionally, aerosol extinction (optical depth) spectra can be inverted to retrieve estimates of the particle size distributions, which can be compared directly to the in situ size distributions. In this paper we will report on such closure studies using data from a select number of vertical profiles at Cabras Island, Puerto Rico, including measurements in distinct Saharan Dust Layers. Preliminary results show good agreement to within 30% between mid-visible aerosol extinction derived from the AATS-6 optical depth profiles and extinction profiles forward calculated using 60s-average in situ particle size distributions and standard Saharan dust aerosol refractive indices published in the literature. In agreement with tendencies observed in previous studies, our initial results show an underestimate of aerosol extinction calculated based on the in situ size distributions relative to the extinction obtained from the sunphotometer measurements. However, a more extensive analysis of all available AATS-6 and in situ size distribution data is necessary to ascertain whether the preliminary results regarding the degree of extinction closure is representative of the entire range of dust conditions encountered in PRIDE. Finally, we will compare the spectral extinction measurements obtained in PRIDE to similar data obtained in Saharan dust layers encountered above the Canary Islands during ACE-2 (Aerosol Characterization Experiment) in July 1997. Thus, the evolution of Saharan dust spectral properties during its transport across the Atlantic can be investigated, provided the dust origin and microphysical properties are found to be comparable.
Document ID
20010092169
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Redemann, Jens
(NASA Ames Research Center Moffett Field, CA United States)
Livingston, John M.
(NASA Ames Research Center Moffett Field, CA United States)
Russell, Philip B.
(NASA Ames Research Center Moffett Field, CA United States)
Schmid, Beat
(NASA Ames Research Center Moffett Field, CA United States)
Reid, Jeff
(NASA Ames Research Center Moffett Field, CA United States)
Date Acquired
August 20, 2013
Publication Date
January 13, 2000
Subject Category
Meteorology And Climatology
Meeting Information
Meeting: American Geophysical Union 2000 Fall Meeting
Location: San Francisco, CA
Country: United States
Start Date: December 15, 2000
End Date: December 19, 2000
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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