Aerosol Optical Properties and Particle Size Distributions on the East Coast of the United States Derived from Airborne In Situ and Remote Sensing Measurements

Abstract

Airborne in situ measurements of vertical profiles and horizontal transects of aerosol optical and physical properties, obtained during the Chesapeake Lighthouse and Aircraft Measurements for Satellites (CLAMS) field campaign off the East Coast of the United States during the summer of 2001, are presented. Most of the measurements were obtained in relatively clean air dominated by airflows that had passed over Canada and the northern Atlantic Ocean. Results from the 17 July and 2 August 2001 flights are presented; on these days, the aerosol loading was relatively high. In the lower troposphere, 0 values at a wavelength of 550 nm were consistently above 0.93 throughout the field experiment, indicating the dominance of weakly absorbing aerosol. Particle number size distributions are presented and discussed for transects at altitudes ϳ0.05-3.5 km above mean sea level. Particles with diameters (D p ) Ͻ0.1 m made up the majority of the aerosol number. Accumulation mode particles dominate the number size, surface area, and volume distributions. The variability of optical and physical aerosol parameters was analyzed on horizontal scales of ϳ1-4 km. There was little horizontal variability in the single-scattering albedo ( 0 ), aerosol optical depth (AOD), and accumulation mode size, but greater variability in particle number concentration. Comparisons of the airborne measurements with remotely sensed aerosol parameters, such as 0 and effective particle radius (r eff ), derived from the Multiangle Imaging Spectroradiometer (MISR) aboard the Terra satellite were generally in good agreement. Overall, the MISR retrievals captured both the similarities and the differences between the properties of the aerosols measured on 17 July and 2 August.

Atmospheric Research Over the Western North Atlantic Ocean Region and North American East Coast: A Review of Past Work and Challenges Ahead

“…The Chesapeake Lighthouse and Aircraft Measurements for Satellites (CLAMS) campaign in July–August of 2001 included airborne, surface, and satellite observations with a goal of validating space‐based retrievals of aerosol properties and vertical characteristics of state variables such as temperature and water vapor (e.g., Redemann et al, ). The region of analysis was off the U.S. East Coast where flights intercepted days with both clean and polluted air masses (Magi et al, ; Reidmiller et al, ), categorized into three regimes (Castanho et al, ): local pollution/sea salt background, long‐range transported dust, and long‐range transported pollution. Numerous research papers associated with CLAMS were critical in terms of advancing aerosol retrievals over land and ocean for both satellite remote sensors such as the Moderate Resolution Imaging Spectroradiometer (MODIS) (Castanho et al, ; Levy et al, ; Remer et al, ), the Multi‐angle Imaging Spectroradiometer (MISR) (Kahn et al, ; Reidmiller et al, ), and the CERES (Smith et al, ), in addition to airborne instruments such as the 14‐channel NASA Ames Airborne Tracking Sunphotometer (AATS‐14) (Redemann et al, ), the Research Scanning Polarimeter (Chowdhary et al, ), and the Cloud Absorption Radiometer (CAR) (Gatebe et al, ).…”

“…The region of analysis was off the U.S. East Coast where flights intercepted days with both clean and polluted air masses (Magi et al, ; Reidmiller et al, ), categorized into three regimes (Castanho et al, ): local pollution/sea salt background, long‐range transported dust, and long‐range transported pollution. Numerous research papers associated with CLAMS were critical in terms of advancing aerosol retrievals over land and ocean for both satellite remote sensors such as the Moderate Resolution Imaging Spectroradiometer (MODIS) (Castanho et al, ; Levy et al, ; Remer et al, ), the Multi‐angle Imaging Spectroradiometer (MISR) (Kahn et al, ; Reidmiller et al, ), and the CERES (Smith et al, ), in addition to airborne instruments such as the 14‐channel NASA Ames Airborne Tracking Sunphotometer (AATS‐14) (Redemann et al, ), the Research Scanning Polarimeter (Chowdhary et al, ), and the Cloud Absorption Radiometer (CAR) (Gatebe et al, ). With the support of MODIS data, in situ observations during CLAMS showed that an incursion of Saharan dust between 24 and 26 July resulted in dust accounting for 40% of fine particulate mass, while on another occasion (17 July 2001) SO 4 2‐ accounted for 70% of fine particulate mass during a regional pollution episode (Castanho et al, ).…”

Response to “Toward unified satellite climatology of aerosol properties. 3. MODIS versus MISR versus AERONET”

“…The MISR and MODIS instrument teams, as well as many other research groups, have performed such evaluations using a variety of methods, ranging from theoretical sensitivity studies to comparisons with other satellite and suborbital data sets [e.g., 2,[6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. Over the past ten years, the exchange of data, information, and ideas represented by this body of work has yielded better characterization of existing products, as well as algorithm upgrades.…”

SAM-CAAM: A Concept for Acquiring Systematic Aircraft Measurements to Characterize Aerosol Air Masses

“…Data download to the ground might be required to make any real-time flight decisions. The payload could occasionally also be flown within the field of view of satellite instruments, to allow intercomparison and, to the degree possible, cross validation of in situ and remote sensing results (e.g., Kahn et al 2004;Reidmiller et al 2006). However, satellite coordination would not be required to meet the primary objectives of SAM-CAAM, and, for example, the required in situ sampling would be possible under nonprecipitating, cloudy conditions.…”