PhD: Links between atmospheric chemistry and -climate in the Marine Boundary Layer

Project Description

The oceans cover ~70% of the Earth's surface. The lowest part of the atmosphere over the oceans, the marine boundary layer (MBL), is subject to fluxes of sea spray aerosol and gases from the ocean and is linked to the free troposphere (FT) by vertical mixing in convective events but also by large scale mixing events such as frontal passages or tropical easterly waves. Most greenhouse gases (such as carbon dioxide, CO2, nitrous oxide, N2O) have atmospheric lifetimes of hundreds or thousands of years but others, notably methane, CH4, and tropospheric ozone, O3, have much shorter lifetimes (~9 years and weeks, respectively), largely because they have chemical sinks in the troposphere. Together they account for about 30% of the global radiative forcing of all greenhouse gases. Under most conditions, the MBL acts as a sink for O3 due to the low concentrations of NOx; furthermore about 25% of the tropospheric CH4 destruction occurs in the tropical MBL and a further 35% in the tropical marine free troposphere. Therefore a quantitative understanding of the composition and chemistry of the marine atmosphere is crucial to examine the atmospheric oxidative capacity and climate forcing.

 

This project will investigate mechanistic details of this coupling using a state-of-the-art high resolution three-dimensional atmospheric chemistry model (WRF-Chem). This model allows, in addition to capturing the complex photochemistry, the examination of the role of meteorological factors including convection and cloud effects on transport and chemistry and to quantify the impacts on tropospheric oxidation capacity and climate forcing. The model results will be compared to data from recent and planned field campaigns in the North Atlantic (Cape Verde Atmospheric Observatory and Bermuda). The model will then be used to quantify lifetimes and budgets of important compounds such as ozone and methane.

 

The overarching objective of this proposal is:

To quantify the cycling of marine gases and particles and their impact on the chemistry of the marine boundary layer and the free troposphere with emphasis on reactive halogens.

This will be addressed with the help of the following specific objectives:

(1) To quantify the role of meteorological processes for the spatial variability of marine gases and their vertical transport  and export to the free troposphere.

(2) To investigate the temporal variability (day-to-day and interannual) of halogen release in the North Atlantic.

(3) To establish details of the cycling of reactive chlorine between the gas, aerosol and cloud droplet phases.

 

This project is suitable for a student with a strong interest in atmospheric science and numerical modelling. The student will receive training in atmospheric science, especially atmospheric chemistry, numerical modelling, data analysis and interpretation and will have the opportunity to collaborate with colleagues from other universities that make relevant field measurements and take part in a major field campaign in the North Atlantic (Cape Verde or Bermuda) to understand the complexities of data collection and for improved collaboration with the partners.

 

Information

Start date: October 2015

Programme: PhD

Mode of Study: Full Time

 

Deadline: 31 May 2015. NB Applications are processed as soon as they are received, so early application is encouraged as the project may be filled before the application deadline.

 

More information and apply online.