ACE-2 (Jun 16 - Jul 25, 1997)

Brief description

The anthropogenically influenced marine atmosphere of the North Atlantic was chosen for second Aerosol Characterization Experiment (ACE-2). Aerosol characteristics, processes and effects were contrasted with those observed during ACE-1, which took place in the minimally polluted Southern Ocean. Four major aerosol types have been identified in the North Atlantic region. Sea-salt particles are ubiquitous in the lowest layers of the marine atmosphere. Dimethyl sulfide (DMS)-derived particulate mass has been identified throughout the marine troposphere. Large mass concentrations of Saharan mineral dust are predominantly found in the sub-tropical and tropical part of this area. Finally, the North Atlantic is exposed to most of the North American and part of the European plume of anthropogenic emissions, and anthropogenic aerosols have been observed over large areas of the North Atlantic Ocean.

The goal of ACE-2 was to determine and understand the properties and controlling factors of the aerosol in the anthropogenically modified atmosphere of the North Atlantic and assess their relevance for radiative forcing. To achieve this goal, ACE-2 pursued three specific 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 of their physical, chemical, radiative and cloud nucleating properties.
• 3. Develop procedures to extrapolate aerosol properties and processes from local to regional and global scales, and assess the regional direct and indirect radiative forcing by aerosols in the North Atlantic region.

Overview of C-130 flights

• Flight map
• Figure of flight profiles and latitudes

Overview of ARAT flights

• Flight map
• Figure of flight profiles and latitudes

Special remarks concerning ETHmeg database content

Measurements included in the database were obtained from the following two platforms:

• ARAT (Avion de Recherches Atmosphériques) Fokker 27 (FR).
  Only O3 and H2O (and radiation) data available
• C-130: MRF, Max Planck Institute for Chemistry: SO2 and Aerosol Ion data.
  MRF, UEA University of East Anglia, UK): H2O2 data on
  MRF, UKMO: H2O2, CO, JNO2, O3, H2O (H2O not downloaded yet)
  MRF, UYORK: hydrocarbon data

An overview of file types and contents can be found in the file readme_ukmo.txt.

We used the following ARAT files and parameters:

• ARAT-INSU-003: Contains a subset of parameters from all ARAT flights. This is the only ARAT file needed. Used parameters:
  lon, lat, p, O3, MIXR (derived from dewpT using ice saturation curve), T, dewpT

• file2: GPS lat, GPS lon, GPS alt (converted to p assuming US standard atmosphere)
• file1: CN, O3
• co: CO
• h2o2: H2O2, org. peroxides
• jno2: up and down (not used because no NO available either)

• O3 concentrations on 19970625 at 14:39 and 14:45 UTC are unreasonably high (up to 700 ppb). These values therefore eliminated (by hand) from the monthly file.
• Several near-zero O3 concentrations on 19970615 between 10:45 and 10:57 are strange.
• File a551_file1.dat-gz had a wrong header. The header of a552_file1 was therefore copied to this file.
• File a560_file1.dat-gz: was not read sucessfully because several columns were missing.

Overview of measurement techniques and uncertainties

References