Metadata Report for BODC Series Reference Number 1003683

• Metadata Summary

• Problem Reports

• Data Access Policy

• Narrative Documents

• Project Information

• Data Activity or Cruise Information

• Fixed Station Information

• BODC Quality Flags

• SeaDataNet Quality Flags

Metadata Summary

Problem Reports

No Problem Report Found in the Database

Data Quality Report

No problems with data quality were reported by the data originator, or identified by BODC. Aerosol growth factors drop for the duration of the port call at Mindelo, however there is no reason to believe that these data are defective.

Data Access Policy

Public domain data

These data have no specific confidentiality restrictions for users. However, users must acknowledge data sources as it is not ethical to publish data without proper attribution. Any publication or other output resulting from usage of the data should include an acknowledgment.

The recommended acknowledgment is

"This study uses data from the data source/organisation/programme, provided by the British Oceanographic Data Centre and funded by the funding body."

Narrative Documents

Instrument Description

Hygroscopic Tandem Differential Mobility Analyser

The Hygroscopic Tandem Differential Mobility Analyser (HTDMA) measures the changes in aerosol size distribution in response to a change in relative humidity. The response of an aerosol particle to a change in humidity is a function of its size and chemical composition. The ratio of the wet and dry particle diameters is referred to as the particle growth factor.

The HTDMA comprises two Differential Mobility Analysers (DMA, Winklmayer et al., 1991), a TSI 3010Condensation Particle Counter (particle detection limit 50% at 10 nm), and humidity control devices. The DMAs are used in series: DMA-1 and DMA-2. The polydisperse air sample is dried to < 10% relative humidity as it enters the instrument. DMA-1 is used to select a monodisperse distribution of a chosen size. The monodisperse sample is humidified as it enters DMA-2. DMA-2 is coupled to the particle counter to measure the size distribution of the humidified sample.

The HTDMA has two modes of operation: constant humidity; and varying humidity. In constant humidity mode, DMA-1 selects a sequence of monodisperse, dry samples, each of which is humidified to 90% relative humidity as it enters DMA-2. In varying humidity mode, DMA-1 is set to select a single dry size, and the humidity of the sample entering DMA-2 is increased in steps from 30-90%.

A full description of the instrument, and of data processing, is given by Cubison et al. (2005).

References

Cubison M.J., Coe H., Gysel M., 2005. A modified hygroscopic tandem DMA and a data retrieval method based on optimal estimation, Journal of Aerosol Science, 36, 846-865.

Winklmayer W., Reischl G.P., Lindner A.O., Berner A., 1991. A new electromobility spectrometer for the measurement of aerosol size distributions in the size range from 1 to 1000 nm, Journal of Aerosol Science, 22, 289-296.

Manchester Centre for Atmospheric Science Hygroscopic Tandem Differential Mobility Analyser (HTDMA)

The Hygroscopic Tandem Differential Mobility Analyser measures size-resolved aerosol hygroscopic properties (i.e. the manner in which an aerosol population responds to a change in relative humidity). The response is generally non-linear and depends on particle size and chemical composition. Soluble particles take on water and grow with increasing humidity, while particles composed of hydrophobic material do not. The amount of growth also depends on size according to the Kelvin effect, so small particles grow less than larger ones. The ratio of the wet and dry diameters is referred to as the growth factor.

To measure changes in aerosol size distribution in response to a change in relative humidity, the HTDMA uses two Differential Mobility Analysers (DMAs), operated in series. The incoming air sample is dried to <10% relative humidity, and the first DMA selects a monodisperse distribution of a chosen size. The monodisperse subsample is humidified, and the second DMA, coupled to a particle counter, measures the size distribution of the humidified sample.

Specifications

Further details can be found in the manufacturer's specification sheet.

Aerosol Properties Sampling

The University of Manchester deployed a suite of instruments to measure aerosol properties on D319. Wet and dry aerosol size spectra were measured by a combination of Differential Mobility Particle Sizers and an Optical Particle Counter. Online aerosol particle composition was determined by Aerodyne Aerosol Mass Spectrometer, and by Multi Angle Aerosol Photometer. Aerosol particle growth factors were measured by a Hygroscopicity Tandem Differential Mobility Analyser. A combination of samplers was used for the offline analysis of aerosol particle composition: a four stage Harvard compact cascade impactor, and an Anderson high-volume sampler.

Atmospheric aerosols were sampled throughout the D319 cruise through a 10 m vertical inlet stack mounted on the forecastle deck. Air was drawn in though a 2.5 µm cutoff cyclone, and distributed to the instruments listed above through a horizontal manifold, using isokinetic sampling ports.

Originator's Data Processing

Aerosol growth factors were measured using a Hygroscopic Tandem Differential Mobility Analyser (HTDMA). The HTDMA was operated in constant humidity mode, selecting dry diameters of 24, 43, 85, 127, 169, 211 and 254 nm. The instrument was calibrated at the start of the cruise, prior to data logging. Growth factors were reported hourly, between 20th May and 6th June 2007.

Further details of the sampling strategy and methodology for this, and for other D319 data sets, are available from the D319 cruise report, and from Allan et al. (2009).

References

Allan, J.D., Topping D.O., Good N., Irwin M., Flynn M., Williams P.I., Coe H., Baker A.R., Martino M., Niedermeier N., Wiedensohler A., Lehmann S., Muller K., Herrmann H., McFiggans G., 2009. Composition and properties of atmospheric particles in the eastern Atlantic and impacts on gas phase uptake rates, Atmospheric Chemistry and Physics, 9, 9299-9314.

BODC Data Processing

Data were received by BODC in tab separated ASCII format (D319_growth_factors_v1.txt). This file included date and time, and aerosol growth factors for seven dry particle diameters: 24, 43, 85, 127, 169, 211, and 254 nm. No position data were supplied with the growth factor data. Latitude and longitude position were merged into the data file, by BODC, from the screened and processed cruise navigation file, matching on time.

Parameter codes defined in the BODC parameter dictionary were mapped to the variables as follows:

The data were banked according to BODC standard procedures for series data. Once tagged with the appropriate parameter code, the data were transferred to NetCDF format, and loaded into the BODC Series Database.

Project Information

Surface Ocean Lower Atmosphere Study

The Surface Ocean-Lower Atmosphere Study (SOLAS) is an international research initiative comprising over 1500 scientists in 23 countries. Its central goal is to understand the biogeochemical-physical interactions between the ocean and atmosphere, and how their coupling affects, and is affected by climate change.

UK SOLAS, Aerosol Characterisation and Modelling in the Marine Environment (ACMME)

This project was run by the University of Manchester, with the following principal aims:

• To characterise the chemical and hygroscopic properties of marine aerosol as a function of size
• To quantify the cloud-forming potential of the aerosol
• To predict the effect of marine aerosol on cloud droplet number
• To study meridional variation in aerosol properties

ACMME made use of the fieldwork activities of other UK SOLAS projects. Sampling was carried out on the RHaMBLe cruise, D319, and at the Cape Verde observatory. Key measurements included aerosol size spectra, chemical composition, and hygroscopicity. The data will be used in conjunction with the models developed by the NERC-funded Aerosol Properties, Processes And InfluenceS on the Earth's climate (APPRAISE) programme. The model study will examine the relationships between aerosol characteristics and cloud formation.

More detailed information on this project may be found in the official cruise report for D319.

Weblinks

http://www.nerc.ac.uk/research/programmes/solas/

http://ncasweb.leeds.ac.uk/appraise/

UK Surface Ocean Lower Atmosphere Study

The UK Surface Ocean Lower Atmosphere Study (UK SOLAS) is the UK's contribution to the international SOLAS programme.

UK SOLAS formed interdisciplinary teams to address three primary aims

• To determine the mechanisms controlling rates of chemical transfer and improve estimates of chemical exchanges
• To evaluate the impact of these exchanges on the biogeochemistry of the surface ocean and lower atmosphere and on feedbacks between the ocean and atmosphere
• To quantify the impacts of these boundary layer processes on the global climate system

UK SOLAS started in 2003, to run for seven years. The programme was funded by the Natural Environment Research Council.

Funded projects

In total, 19 projects have been funded by UK SOLAS, over four funding rounds.

UK SOLAS has also supported ten tied studentships, and two CASE studentships.

Fieldwork

UK SOLAS fieldwork has included eight dedicated research cruises in the North Atlantic Ocean. Continuous measurements were made aboard aboard the Norwegian weather ship, Polarfront, until her decommission in 2009. Time series have been established at the SOLAS Cape Verde Observatory, and at the Plymouth Marine Laboratory L4 station. Experiments have taken place at the Bergen mesocosm facility.

A series of collaborative aircraft campaigns have added complementary atmospheric data. These campaigns were funded by UK SOLAS, African Monsoon Multidisciplinary Analyses (AMMA-UK), Dust and Biomass Experiment (DABEX) and the Facility for Airborne Atmospheric Measurements (FAAM).

Weblink: http://www.nerc.ac.uk/research/programmes/solas/

Data Activity or Cruise Information

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

No Fixed Station Information held for the Series

BODC Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:

SeaDataNet Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle: