Objective
To evaluate the uncertainty in methodology for the assessment of the direct radiative forcing of aerosol over the North Atlantic from an over-determined set of aerosol optical properties measured in a column and connected through radiation models.
Physical and chemical properties of the aerosol will be measured in the vertical column to be used to accurately
predict the integrated direct effect of aerosols on radiative transfer. In that column, the experiment will derive the aerosol parameters which are necessary to quantify the direct
radiative forcing of the tropospheric aerosol. These data will provide the radiative reference point for all
airborne radiative measurements within ACE-2. The satellites involved in this study will then be used to relate
the direct radiative forcing derived in CLEARCOLUMN and in other columnar experiments to the larger North
Atlantic region.
The ground based columnar extinction- and scattering measurements are carried out at three elevations, on three
airborne platforms in the vicinity of a LIDAR beam. Unidisciplinary and multi-disciplinary local closure will be
derived at different altitudes in the boundary layer and free troposphere from radiative and physico-chemical
aerosol information.
The vertically integrated LIDAR information will be compared to columnar extinction data derived from
ground-based and air- and space borne radiometers (supported by data on water-leaving radiances from ship and airborne platforms) in order to derive column closure of aerosol optical properties.
The radiative flux divergences from airborne measurements at different altitudes will be compared to
corresponding results derived by means of radiative transfer modelling from LIDAR-profiles and airborne
measurements within the aerosol layer in order to quantify the direct radiative forcing of the aerosol layer.