Prof. Nga Lee (Sally) Ng is a world leader in the field of aerosol science and the impact of particulate matter on air quality, human health, and climate. Her work exemplifies the phrase “excellence in climate and atmospheric science research and leadership” that defines the criteria for the Ascent Award.

Dr. Ng’s early work helped to define the state of the science for particulate matter and organic aerosol. Major contributions included elucidating the role of different generations of oxidants that produce organic aerosol from biogenic (natural origin, vegetation) hydrocarbon oxidation, furthering the understanding of anthropogenic (human origin) oxidation processes, and pioneering experiments showing large organic aerosol yields from nighttime oxidation of isoprene, the most important biogenic hydrocarbon.

The developing field of aerosol mass spectrometry underpinned much of this progress. Dr. Ng made novel contributions to the interpretation of this now widely used analytical tool. Dr. Ng’s insightful interpretation of fragment masses and their dependence on different oxidation processes has enabled the definition of different aerosol types and their major sources and chemical characteristics. These tools have been invaluable to the field and are reflected in a series of highly cited reviews and papers.

A signature result of Dr. Ng’s research has been the quantification of the influence of anthropogenic emissions in the oxidation of biogenic volatile organic compounds (VOCs) to form organic aerosol that affects climate and human health. These so-called anthropogenic-biogenic interactions take several forms, and can occur through emissions of both sulfur (emitted as SO₂) and nitrogen (emitted as nitrogen oxides, NO_x = NO + NO₂). Dr. Ng has used detailed measurements from both the laboratory and the field to advance this field of research.

Most recently, Dr. Ng has established a network for the long-term measurement of aerosol composition at sites across the United States. Her recently established network will provide long-term, state-of-the-art, high time resolution mass spectrometric aerosol composition and other data. This ambitious initiative exploits the current state of the art in analytical capacity to build an entirely new program for the trends, sources, and climate and air quality impacts of aerosols. The National Science Foundation–supported Atmospheric Science and Chemistry Measurement Network (ASCENT) is in its infancy, with 12 sites across 10 states. The value of this network will grow rapidly as it develops a data record that will be used by atmospheric scientists and modelers around the world.

—Daniel M. Sigman, Department of Geosciences, Princeton University, Princeton, N.J.