IAP

Surface measurements of aerosol optical properties have been made in a variety of locations and used to estimate the aerosol contribution to radiative forcing. The applicability of such calculations depends on how well surface measurements represent the column properties. NOAA/ESRL/GMD (formerly NOAA/CMDL) has been mentoring ARM’s surface measurements of climatically important aerosol optical properties at the Southern Great Plains CART site near Lamont, OK since 1996. Variability in the surface properties of aerosol particles has been shown over hourly, daily, monthly and seasonal timescales due to, but it is not well understood how well these variations correlate with aerosol properties aloft and how those vertical variations would affect radiative forcing estimates. In March 2000, a small aircraft (Cessna 172) was outfitted with a subset of the instrument package at the surface site and the In-Situ Aerosol Profiles (IAP) campaign began. IAPs purpose is 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? • How much aerosol do we miss staying at or below 3.5 km? The IAP aircraft obtains vertical profiles of aerosol optical properties over the surface site 2-3 times per week. The original IAP instrument package made measurements of light scattering and backscattering at 3-wavelengths, and light absorption at a single wavelength for sub-micron aerosol at low (<40%) relative humidities. The success of the IAP program in its first few years resulted in an upgrade to a slightly larger aircraft (Cessna 206). As of April 2006, the IAP aerosol package measures light scattering, back scattering and absorption at 3 wavelengths for particles with diameter less than approximately 5 microns. It also measures submicron light scattering at 1 wavelength for 3 humidities to provide an indication of the hygroscopic nature of the aerosol. Non-aerosol instruments which have been incorporated into the aerosol package include a programmable flask package for obtaining samples of carbon dioxide and other trace gases at each flight level and continuous gas analyzers for carbon dioxide and ozone. Data from the IAP measurements have been used in multiple peer-reviewed papers and the long-term profiling campaign concept has won the 2006 NOAA Administrator’s award. Data from the more than 700 flights (as of September 2006) are available from the ARM archive. Typically the flight data are reviewed, QC’d and submitted to ARM within 2 days of a flight occurring.

Timeline

Campaign Data Sets