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Centre for Atmospheric Science

RHaMBLe Project-Cruise

The NERC research vessel RRS Discovery.
The NERC research vessel RRS Discovery.

The RHaMBLe project cruise (known as D319) comprises the whole of WP 2 (and much more!!!):
Ship characterisation of MBL chemistry variation with latitude and variable source region

The cruise aims are.
i) to quantify marine halocarbon emission variability and latitudinal variation,
ii) characterise in situ open ocean atmospheric reactive iodine latitudinal variability and
iii) characterise oxidative chemistry perturbation due to oceanic emission of halogens from the Mauritanian upwelling region.

The original envisaged rationale behind WP2.
By deploying on a suitable available NERC ship transecting from the UK through Biscay, south past the west coast of Africa, through the Mauritanian upwelling, to pass Cape Verde simultaneous to the intensive deployment in WP1, WP2 will provide a detailed latitudinal characterisation of marine atmospheric halogen chemistry. This will feed validation and constraint data to regional and global models in the linked projects. In addition this work package will address a number of key scientific questions required to determine the global importance of iodine chemistry and to further our understanding of the controls of halogen chemistry in the remote ocean:
i) How heterogeneous are the direct halogen sources and on what scale is the heterogeneity – does the upwelling region produce more or less halogens than the “background” region?
ii) What are the relative contributions of I atoms to the remote MBL from I2 and organic iodine?
iii) Is sufficient iodine released to the remote MBL to sustain aerosol nucleation or to significantly affect the ozone budget and free radical populations?

Broad description of the activities originally envisaged within WP2.
May / June 2007. Measured species include a variety of halocarbons in both water column and atmosphere and tropospheric measurements of I2, OIO and IO by Broadband Cavity Enhanced Absorption Spectroscopy (BBCEAS). A compact version of the FAGE system, developed for the FAAM BAe-146, was to be deployed to provide measurements of IO or OH / HO2, permitting direct assessment of RHS-induced changes in the oxidising environment through the upwelling region. A range of trace gas monitors would also be simultaneously deployed on the ship to measure O3 and NOx, with aerosol number and size distribution measurements from 3 nm to 20 ?m being made by a range of mobility (SMPS) and optical instrumentation, (OPC and FSSP). Prevailing meteorological conditions will be used to direct the cruise in terms of geographical positioning and measurement interpretation, e.g.
i) exploitation of any broad flow connection between Cape Verde and the ship to interpret measurements as process studies and
ii) identification of in- and out-of-plume conditions to contrast chemistry influenced and uninfluenced by emissions from the upwelling region.
In line with UK SOLAS guidance, exact cruise logistics were to be agreed once all successful projects had received ship-time allocation, with 4 berths required by RHaMBLe participants.

See the measurement description page for details of the techniques mentioned above.

Discovery Cruise D319 has vastly expanded upon the original aims of WP2 within RHaMBLe.
The ship-time allocation within UK SOLAS was unable to marry the aims and objectives of RHaMBLe to those of any other funded activity. The D319 slot on the RRS Discovery was therefore directly allocated to RHaMBLe. It was decided to extend the scientific remit as far beyond the original requirement as the original PIs were able and then to invite participation of additional personnel. Firstly, all groups increased the number of personnel to improve data coverage. Secondly, in addition to the core RHaMBLe measurements outlined above, a number of additional measurements were made. Brendan Keely, from the University of York, provided HPLC measurements of photosynthetic pigments. Paul Monks from the University of Leicester provided 2 spectral radiometers for use on the cruise. Measurements of aerosol particles formed in bubble bursting were made as part of the COMPAS project of Hugh Coe and Gordon McFiggans at the University of Manchester. A greatly extended payload of aerosol measurement instrumentation was deployed within the UK SOLAS funded Aerosol Characterisation and Measurement in the Marine Environment (ACMME) project, headed by James Allan of the University of Manchester. The number of scientific berths occupied has increased from 4 in a shared cruise to 13 in D319.

RHaMBLe Cruise D319 on the RRS Discovery will deliver.
Spatial distribution of concentrations of trace molecules, radicals and aerosol particles plus a whole lot more!!!

Some ship facts.
Length overall: 90.25 m
Length B.P.: 82.85 m
Breadth moulded: 14.02 m
Depth to main deck: 5.49 m

Accelerate: 0-6 knots in 7.5 minutes
Consumption: 0.147 nautical miles per gallon; 6.8 gallons per nautical mile; 7.5 tonnes a day

Carries 512 tonnes of fuel oil and 208 tonnes of fresh water (98% capacity).