Next Step: The Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX)

Contributed by P. B. Russell, NASA Ames Research Center, USA

Reprinted from IGACtivities Newsletter #4, March 1996


Introduction

As noted in the preceding news feature (Bates and Gras, IGACtivities 4), uncertainties regarding the climatic impacts of anthropogenic aerosols are unacceptably large, both for validating current climate models and for predicting future regional and global climate. An important step in reducing these uncertainties is to measure the direct radiative forcing by tropospheric aerosols over various regions of the globe while simultaneously measuring the properties of the responsible aerosols. Intensive field programs, when extended with satellite measurements and validated retrieval algorithms, can provide the necessary data on both the aerosols and their radiative effects. The Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) will focus on providing this information for one of the most polluted regions of the world, namely, the United States (US) eastern seaboard.

To illustrate the coverage possible with satellite remote sensing of aerosol properties, Figure 1 shows a map of the mean June/July/August aerosol optical thickness derived from the NOAA/AVHRR operational product. These are approximate values, since an aerosol model is used to retrieve aerosol optical thickness from the measured satellite reflectances. TARFOX will provide a critical assessment of the correctness of these retrievals. The data in Figure 1 show a well-defined plume of aerosol extending from the US east coast over the Atlantic Ocean. This plume is well separated from the plume that extends from the west coast of Africa, across the Atlantic, and over the Caribbean, which consists predominantly of mineral dust. Hence, the US east coast plume provides an excellent opportunity to isolate and study aerosols generated by industrial activity, and to determine the magnitude and uncertainty of the direct radiative forcing due to these aerosols.


Goals

The principal goals of TARFOX are to:

To achieve these goals, the following principal questions have to be answered:


Implementation

Answering the questions posed above will require an extensive theoretical radiative transfer modeling effort, an intensive field measurement program, and integrated analyses. The specific Tasks of TARFOX are discussed below.

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