AEROSOLS AND THEIR RADIATIVE/CLIMATIC EFFECTS: SPACE, AIR, AND GROUND MEASUREMENTS AND ANALYSES

Philip B. Russell and Rudolf F. Pueschel1

As a part of Science Team activities for the spacecraft sensors SAM II, Stratospheric Aerosol and Gas Experiment (SAGE, SAGE II, and SAGE III), Ames has designed, participated in, and analyzed measurements by aircraft, balloons, and ground-based remote sensors to validate and complement the spacecraft measurements. Current and recent activities include ER-2 and DC-8 campaigns to measure particle size distribution, composition, and optical depth spectra before and after the Pinatubo eruption (in coordination with SAGE II measurements), developing the data validation plan for the SAGE III sensor (to fly on the Earth Observing System, EOS), and designing several autotracking sunphotometers to fly on a variety of occupied and unoccupied aerial vehicles (UAVs) as a component of multidisciplinary studies of aerosol climatic effects.

A SAGE II Science Team data analysis task is bringing together experimental evidence required to build realistic models of the global evolution of physical, chemical, and optical properties of the aerosol resulting from the 1991 Pinatubo volcanic eruption. Such models are needed to compute the effects of the aerosol on atmospheric chemistry, dynamics, radiation, and temperature. Whereas there is now a large and growing body of post-Pinatubo measurements by a variety of techniques, some results are in conflict, and a self-consistent, unified picture is needed, along with an assessment of remaining uncertainties. This task examines data from photometers, radiometers, impactors, optical counters/sizers, and lidars operated on the ground, aircraft, balloons, and spacecraft. Example data sources include:

* Tracking sunphotometers and lidars at Mauna Loa Observatory (MLO) and on the DC-8

* Particle spectrometers and wire impactors on the ER-2 and DC-8

* Dustsondes (particle counter/sizers on balloons)

* SAGE II, SAM II, AVHRR, CLAES, and ISAMS sensors on a variety of satellites.

This task assesses the mutual consistency of these disparate data sets and recommends "consensus" properties and uncertainties in the process of developing a composite data set.

Related tasks have developed scientific strategies for measuring tropospheric aerosol properties and radiative/climatic effects, and for testing the mutual consistency of these measurements and the model calculations that link them. These strategies are described in the plans for the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) and the Aerosol Characterization Experiment (ACE), field studies planned for 1995-1997. These experiments will combine space, air, and Earth-surface measurements to improve scientific understanding of aerosol effects on climate.

Project participants include John M. Livingston of SRI International and Patrick Hamill, Shari Brooks, Jill Baumann Hughes and Robert Bergstrom of San Jose State University.

Ames-Moffett contact: Dr. Philip B. Russell

prussell@mail.arc.nasa.gov

or tel: (415) 604-5404

Headquarters program office: YSM

1SGP