Timescales of processes controlling water vapour entry to the stratosphere
type: CreativeWork
description: This thesis assesses the representation of the key processes determining water vapour entry into the stratosphere in reanalysis and two global climate model configurations. This is done by applying the advection-condensation method and comparing alternative formulations. In the region of the atmosphere around 15–50 km altitude known as the stratosphere, water vapour is present in concentrations around ten thousand times lower than at the Earth’s surface. Yet, water vapour still influences surface warming and stratospheric chemistry due to its radiative and chemical properties. Previous studies have identified low temperatures (more accurately, low saturation mixing ratios) and large-scale transport through the tropical tropopause layer to be the key factors that determine stratospheric water vapour. However, their relative importance at different timescales, and the role of the other influences such as detailed ice microphysics, are not yet well known. It is a crucial priority to improve the generally poor representation of stratospheric water vapour in global climate models for both present and future scenarios. In the first chapter of results, the representation of the average annual cycle of lower stratospheric water vapour by temperature and large-scale transport is assessed. Model-specific features are reflected in water vapour predictions by the advection-condensation method. Applying a climate model advection scheme to the advection-condensation method, to test sensitivity to transport formulation, finds more similar temporal variability but also affects vertical attenuation of concentrations in the stratosphere. Expanding on earlier studies, the impact of sub-seasonal temperature variability on stratospheric water vapour is quantified in reanalysis and in one global climate model where it is found to be under-represented. Following on, the next chapter investigates the substantial interannual variability of tropical lower stratospheric water vapour by isolat…
abstract: This thesis assesses the representation of the key processes determining water vapour entry into the stratosphere in reanalysis and two global climate model configurations. This is done by applying the advection-condensation method and comparing alternative formulations. In the region of the atmosphere around 15–50 km altitude known as the stratosphere, water vapour is present in concentrations around ten thousand times lower than at the Earth’s surface. Yet, water vapour still influences surface warming and stratospheric chemistry due to its radiative and chemical properties. Previous studies have identified low temperatures (more accurately, low saturation mixing ratios) and large-scale transport through the tropical tropopause layer to be the key factors that determine stratospheric water vapour. However, their relative importance at different timescales, and the role of the other influences such as detailed ice microphysics, are not yet well known. It is a crucial priority to improve the generally poor representation of stratospheric water vapour in global climate models for both present and future scenarios. In the first chapter of results, the representation of the average annual cycle of lower stratospheric water vapour by temperature and large-scale transport is assessed. Model-specific features are reflected in water vapour predictions by the advection-condensation method. Applying a climate model advection scheme to the advection-condensation method, to test sensitivity to transport formulation, finds more similar temporal variability but also affects vertical attenuation of concentrations in the stratosphere. Expanding on earlier studies, the impact of sub-seasonal temperature variability on stratospheric water vapour is quantified in reanalysis and in one global climate model where it is found to be under-represented. Following on, the next chapter investigates the substantial interannual variability of tropical lower stratospheric water vapour by isolat…
author: Smith, Jacob Willock
language: en
keywords: Atmosphere, Climate science, water vapour, global climate model, transport, stratosphere, tropical tropopause layer
license: https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/2838628a-a035-414f-bd69-bbba52a04328/download
license: https://creativecommons.org/licenses/by/4.0/
date published: 2020-03-12
date modified: 2026-07-22T22:24:13Z
provider: Cambridge University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Cambridge

PropertyValue
property ID: DOI
value: 10.17863/CAM.50382