School of Earth and Environment

Thomas Wood Thomas Wood

Postgraduate Researcher

Email address: pm11tw@leeds.ac.uk

Affiliation: Institute for Climate and Atmospheric Science

Qualifications

BEng Civil Engineering (University of Birmingham, 2011)

MSc Energy & Environment (University of Leeds, 2012)

Project details

Project title

Novel climate feedbacks in the Earth system and their contribution to future global change.

Supervisors

Dr Amanda Maycock and Professor Piers Forster

Funding

NERC DTP

Start date

1 January 2017

Project outline

Quantifying drivers of changes in the position of the Hadley cell edge in idealised climate perturbation experiments:

The tropical belt comprises a band of high rainfall encircling the equatorial region, bordered by arid subtropical zones to the north and south. The latitudinal extent of the tropical belt is related to the structure of the Hadley cell.

Observations and reanalysis data show that since the late-1970's, the dry tropical edge has expanded poleward, particularly in the Southern hemisphere. The rate of tropical expansion over this period is estimated between 0.25° and 3° latitude decade-1 (Davis & Rosenlof, 2012). Climate models generally underestimate the rate of tropical expansion compared to observed estimates. It is not clear whether this is due to differences in modelled internal variability compared to observations and/or differences in the response to climate forcings.

Expansion of the tropical edge could have significant implications for the hydrological cycle and regional climate, particularly for areas currently on the poleward side of the subtropical arid zones. It is therefore important to explore the factors that drive changes in the width of the tropics.

A recent study examined the response of metrics for the tropical edge in the Southern hemisphere to a 4xCO2 perturbation using CMIP5 model data. This study builds on that work by analysing the mechanisms for modelled changes in the location of the Hadley cell edge in response to a range of anthropogenic drivers from the Precipitation Driver and Response Model Intercomparison Project (PDRMIP), including CO2, CH4, and sulphate and black carbon aerosols. Each simulation includes an abrupt perturbation to a particular forcing agent, which the climate system then adjusts to. Different metrics for diagnosing the Hadley cell edge are computed and their responses to different forcing agents examined. This will contribute to understanding the causes of past tropical expansion and the potential rate and magnitude of future expansion.