Second Aerosol Characterization Experiment

Project Description
The second Aerosol Characterization Experiment (ACE-2) took
place from 16 June till 24 July, 1997, over the sub-tropical
North-East Atlantic.

The choice of the area and time period was based on the
following considerations. The area is characterized by large
scale subsidence and therefore by the existence of a distinct
temperature inversion separating the marine boundary layer
(MBL) from the free troposphere FT. Earlier observations
(ASTEX, Prospero, Raes, ?) have shown that in he MBL of the
N.E. Atlantic clean air alternates with anthropogenic pollution
from Europe and possibly from N. America (ASTEX, McGovern, see
discussion below). In the FT aloft, clean air masses alternate
with mineral dust transported out of N. Africa (Propspero,
Raes). The area thus offers opportunities for studying the
characteristics of various aerosol types. Furthermore, the
dynamics of the MBL in this area are reasonably well understood
(ASTEX) so that Lagrangian experiments could be planned
focusing on aerosol processing during transport over the
ocean. In addition, the area offers good opportunities to study
the interaction of aerosol! s with the low level MBL
stratiform clouds.

Objectives:

1. Determine the physical, chemical, radiative and cloud
nucleating properties of the major aerosol types in the North
Atlantic region and investigate the relationships between these
properties.

2. Quantify the physical and chemical processes controlling the
evolution of the major aerosol types and in particular their
physical, chemical, radiative and cloud nucleating processes.

3. Develop procedures to extrapolate aerosol properties and
processes from the local to regional and global scale, and
assess the regional direct and indirect radiative forcing by
aerosols in the North Atlantic region.

For more information, link to
http://www.ei.jrc.it/ace2/tellusov.html

[Summary provided by Frank Raes 1, Timothy Bates 2,
Ge' Verver 3, Daan Vogelenzang 3 and Marc Van Liedekerke1]