Showing papers by "Kevin J. Noone published in 2004"
TL;DR: The Third European Stratospheric Experiment on Ozone (APE-THESEO) campaign was held from 15 February to 15 March 1999 from the Seychelles in the western Indian Ocean as discussed by the authors.
Abstract: The APE-THESEO campaign was held from 15 February to 15 March 1999 from the Seychelles in the western Indian Ocean. APE-THESEO stands for ‘Airborne Platform for Earth observation — (contribution to) the Third European Stratospheric Experiment on Ozone’. The campaign aimed to study processes controlling the low water content of the stratosphere, including the mechanisms of cloud formation in the tropical tropopause region, and transport processes, studied using measurements of long-lived trace gases and ozone. Two aircraft were used: the high-altitude research aircraft, M-55 Geophysica, which can fly up to 21 km, and the Falcon of the Deutsches Zentrum fur Luft- und Raumfahrt, a tropospheric aircraft. Seven flights were performed, including the first simultaneous in situ and remote sensing of sub-visible cirrus clouds, the first interception of sub-visible cirrus using in-flight guidance from a path-finding aircraft, and guided descent of a high-altitude research aircraft into the anvil cloud at the top of a tropical cyclone. In this paper we describe the payload used, the objectives for each flight, and the meteorological conditions encountered. First results show that a new type of cloud, which we have dubbed ultra-thin tropical tropopause cloud (UTTC), has been observed frequently, and observed to cover areas of 105 km2. The frequent coincidence of the tropopause and hygropause implies that the western Indian Ocean played an important role in the dehydration of the lower tropical stratosphere during the season of the mission. UTTCs, sub-visible cirrus, and visible cirrus, have all been implicated in the observed dehydration. Tracer measurements indicate little mixing of stratospheric air into the upper tropical troposphere.
32 citations
TL;DR: In this article, a one-dimensional ensemble-average model is used to simulate the North Atlantic regional Aerosol Characterisation Experiment (ACE-2) Second Lagrangian experiment, where the same air mass was followed in the trade wind area over the north-east Atlantic during July 1997.
Abstract: A one-dimensional ensemble-average model is used in this study to simulate the North Atlantic regional Aerosol Characterisation Experiment (ACE-2) Second Lagrangian experiment, where the same air mass was followed in the trade wind area over the north-east Atlantic during July 1997. The air mass was affected by increased sea surface temperatures and decreased synoptic-scale subsidence on its way southward towards the Canary Islands. This caused the marine boundary layer (MBL) to grow from a shallow layer capped by a stratocumulus deck to a decoupled layer with cumulus clouds forming below the stratocumulus layer.
Several of the meteorological parameters obtained during a control run show reasonable agreement with observations. The model essentially captures the MBL growth, but the increase of the cloud top height occurs more slowly in the simulation than is indicated by the in situ observations. The sea surface temperature increase seems to be the most important factor for the deepening of the MBL.
The model simulates relatively steep vertical gradients in the sea-salt mass concentrations both in the shallow and deeper MBLs, consistent with in situ measurements. Furthermore, the sea-salt particle mass concentrations estimated by the model for most of the altitude levels in the MBL are within 22% of the observed concentrations of sea-salt-related ions. Turbulent mixing by wind shear did not create well-mixed MBLs based on the sea-salt mass concentrations. Vertical gradients in sea-salt number and mass concentrations suggest a reduced influence of sea-salt particles as cloud condensation nuclei. © Royal Meteorological Society, 2004. S. R. Obsborne's contribution is Crown copyright.
16 citations