Earth System Research Laboratory Long-Term Surface Aerosol Measurements

Aerosol measurements began at the NOAA Earth System Research Laboratory (ESRL) Global Monitoring Division (GMD) baseline observatories in the mid-1970's with the purpose of detecting a response, or lack of response, of atmospheric aerosols to changing conditions on a global scale. In 1992 ESRL/GMD expanded its aerosol research program to include regional aerosol monitoring stations due to anthropogenic aerosols creating a significant perturbation in the Earth's radiative balance on regional scales. The goals of this regional-scale monitoring program are to characterize means, variability, and trends of climate-forcing properties of different types of aerosols, and the factors that control them. In situ measurements of aerosol optical properties (including light absorption, total scattering, hemispheric backscattering, and total aerosol number concentration) are made at monitoring sites at hourly time resolution. The basic aerosol measurement system consists of a nephelometer (measures aerosol light scattering), absorption photometer (measures light absorption), and a condensation nuclei counter (measures particle number concentration). Data from the aerosol monitoring stations are updated several times a day. Following collection of the raw data at the station, the data are inspected through automatic and manual contamination screenings to eliminate contamination from local pollution sources. Automatic screenings use measured wind speed, direction, and/or total particle number concentration to flag contaminated data. Manual screening is more subjective, relying on the station scientist to evaluate the data in the context of automated contamination flags and their knowledge of the site.

Data applications indicate the importance of continuing to provide long-term aerosol in-situ measurements for use in analysis of trends and climatologies, evaluation of model simulations of aerosol climatologies, and behavior and validation of remote sensing retrievals of aerosol optical properties. GMD's measurements also provide ground-truth for satellite measurements and global models, as well as key aerosol parameters for global-scale models.

Through the Big Earth Data Initiative (BEDI), ESRL/GMD has taken their data collection and converted files into NetCDF-4, a self-describing format.