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Aerosol Aircraft Measurements

Airborne Aerosol Observatory (AAO)

Background

It is well known that unlike the major long-lived gases, aerosols are not distributed uniformly in the atmosphere. Regions downwind of major particulate sources such as deserts, biomass burning areas and large cities often have heavy atmospheric aerosol burdens while other areas in cleaner regions have relatively low aerosol loadings. The composition and size distribution of these particles, and thus their optical properties, vary widely from place to place and over time. The atmospheric lifetime of particles in the atmosphere and its dependence on factors such as rainfall, clouds, and other scavenging processes plays a major role in this inhomogeneity. In order to estimate global aerosol radiative forcing and the effects of aerosols on the global climate, measurements of the aerosols are being made by GML scientists at many locations. Many major surface regions remain undersampled, however, and very few long term measurement efforts have been made above the surface.

The NOAA Office of Global Programs has recently funded a new program conceived by the GML Aerosol Group to conduct regular long-term aircraft measurements over the United States. Aerosol optical, microphysical, and chemical properties are being measured on this aircraft, as well as carbon cycle gases and ozone. The airplane is based at Champaign, IL, so that regular vertical profiles over the GML Bondville surface station can be obtained.

Objectives and Approach

The primary objective of this program is to obtain a statistically-significant data set of the vertical distribution of aerosol properties and to relate these properties to those measured by similar or identical instruments at the surface. The measurements will be made by flying a light aircraft (Cessna Turbo 206) over a heavily instrumented surface site Bondville, IL (BND) and utilizing an airborne instrument package to measure aerosol optical, microphysical, and chemical properties similar to that employed at GMLs surface sites. The AAO aircraft will fly level legs at altitudes between 1500 ft and 15000 ft above sea level (400 m - 4800 m asl) several times per week. The measurements taken aboard the AAO aircraft will be used to answer the following scientific questions:

  • How do aerosol properties vary through the vertical column?
  • Under what conditions can surface-based measurements of these properties be used to calculate the direct aerosol radiative forcing from a measured aerosol optical depth?

A secondary objective of the project is to participate in the calibration and validation of aerosol remote sensing data and retrieval algorithms used by several satellites, including the "A-Train" Aqua and Calipso satellites and the TERRA satellite. This will be accomplished by coordination of aircraft activities with satellite overflights and generation of value-added products for comparison with the lidar and column-average sunphotometer data. The aspect of the project is of mutual interest to satellite researchers and GML aerosol scientists. The satellite measurements require "air truth" in situ measurements to identify and constrain systematic errors in the retrievals of aerosol physical properties. Improvements in these algorithms will improve the quality of height dependent information from CALIPSO and other backscatter lidars. The primary mission of the NOAA Airborne Aerosol Observatory (AAO) project is to characterize the radiative properties of aerosols for evaluation of climate forcing. By moving the profile location to a major urban area for periods of time, NOAA scientists get to sample different aerosols and different synoptic scale meteorology than are present at the AAO's central Illinois base of operations. Ferry flights to and from these different profile locations also will provide a wealth of information about aerosols over the eastern US..

In-situ Aerosol Profiles at SGP

Southern Great Plains, Lamont, Oklahoma, USA

The In-situ Aerosol Profiles (IAP) program is funded and operated by the Department of Energy/Atmospheric Radiation Measurement (DOE/ARM) program. This is a joint effort between the ARM program and NOAA/GML. NOAA/GML serves as a mentor for the ARM aerosol observing systems (AOS).

Objectives and Approach

The objective of this project is to obtain a statistically-significant data set of the vertical distribution of aerosol properties (e.g., light scattering and absorption, particle chemistry). The measurements will be used to answer the following scientific questions:

  • How do aerosol properties vary through the vertical column?
  • Under what conditions can surface-based measurements of these properties be used to calculate the direct aerosol radiative forcing from a measured aerosol optical depth?

The measurements will be made by flying a light aircraft (Cessna C-172N) over the SGP site and utilizing a similar aerosol instrument package to the one at SGP. The aircraft will fly level legs at altitudes between 500 m and 3500 m several times per week over the course of one year. How much aerosol do we miss staying at or below 3.5 km?