Refinements in the use of equivalent latitude for assimilating sporadic inhomogeneous stratospheric tracer observations, 1: Detecting transport of Pinatubo aerosol across a strong vortex edge

The use of PV equivalent latitude for assimilating stratospheric tracer observations is discussed - with particular regard to the errors in the equivalent latitude coordinate, and to the assimilation of sparse data. Some example measurements are assimilated: they sample the stratosphere sporadically...

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Main Authors: P. Good, J. Pyle
Format: Article in Journal/Newspaper
Language:English
Published: Copernicus Publications 2004
Subjects:
Online Access:https://doaj.org/article/016872fc515645d484734cd065ab812f
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spelling ftdoajarticles:oai:doaj.org/article:016872fc515645d484734cd065ab812f 2023-05-15T15:15:49+02:00 Refinements in the use of equivalent latitude for assimilating sporadic inhomogeneous stratospheric tracer observations, 1: Detecting transport of Pinatubo aerosol across a strong vortex edge P. Good J. Pyle 2004-01-01T00:00:00Z https://doaj.org/article/016872fc515645d484734cd065ab812f EN eng Copernicus Publications http://www.atmos-chem-phys.net/4/1823/2004/acp-4-1823-2004.pdf https://doaj.org/toc/1680-7316 https://doaj.org/toc/1680-7324 1680-7316 1680-7324 https://doaj.org/article/016872fc515645d484734cd065ab812f Atmospheric Chemistry and Physics, Vol 4, Iss 7, Pp 1823-1836 (2004) Physics QC1-999 Chemistry QD1-999 article 2004 ftdoajarticles 2022-12-31T01:52:48Z The use of PV equivalent latitude for assimilating stratospheric tracer observations is discussed - with particular regard to the errors in the equivalent latitude coordinate, and to the assimilation of sparse data. Some example measurements are assimilated: they sample the stratosphere sporadically and inhomogeneously. The aim was to obtain precise information about the isentropic tracer distribution and evolution as a function of equivalent latitude. Precision is important, if transport across barriers like the vortex edge are to be detected directly. The main challenges addressed are the errors in modelled equivalent latitude, and the non-ideal observational sampling. The methods presented allow first some assessment of equivalent latitude errors and a picture of how good or poor the observational coverage is. This information determines choices in the approach for estimating as precisely as possible the true equivalent latitude distribution of the tracer, in periods of good and poor observational coverage. This is in practice an optimisation process, since better understanding of the equivalent latitude distribution of the tracer feeds back into a clearer picture of the errors in the modelled equivalent latitude coordinate. Error estimates constrain the reliability of using equivalent latitude to make statements like 'this observation samples air poleward of the vortex edge' or that of more general model-measurement comparisons. The approach is demonstrated for ground-based lidar soundings of the Mount Pinatubo aerosol cloud, focusing on the 1991-92 arctic vortex edge between 475-520K. Equivalent latitude is estimated at the observation times and locations from Eulerian model tracers initialised with PV and forced by UK Meteorological Office analyses. With the model formulation chosen, it is shown that tracer transport of a few days resulted in an error distribution that was much closer to Gaussian form, although the mean error was not significantly affected. The analysis of the observations revealed a small ... Article in Journal/Newspaper Arctic Directory of Open Access Journals: DOAJ Articles Arctic
institution Open Polar
collection Directory of Open Access Journals: DOAJ Articles
op_collection_id ftdoajarticles
language English
topic Physics
QC1-999
Chemistry
QD1-999
spellingShingle Physics
QC1-999
Chemistry
QD1-999
P. Good
J. Pyle
Refinements in the use of equivalent latitude for assimilating sporadic inhomogeneous stratospheric tracer observations, 1: Detecting transport of Pinatubo aerosol across a strong vortex edge
topic_facet Physics
QC1-999
Chemistry
QD1-999
description The use of PV equivalent latitude for assimilating stratospheric tracer observations is discussed - with particular regard to the errors in the equivalent latitude coordinate, and to the assimilation of sparse data. Some example measurements are assimilated: they sample the stratosphere sporadically and inhomogeneously. The aim was to obtain precise information about the isentropic tracer distribution and evolution as a function of equivalent latitude. Precision is important, if transport across barriers like the vortex edge are to be detected directly. The main challenges addressed are the errors in modelled equivalent latitude, and the non-ideal observational sampling. The methods presented allow first some assessment of equivalent latitude errors and a picture of how good or poor the observational coverage is. This information determines choices in the approach for estimating as precisely as possible the true equivalent latitude distribution of the tracer, in periods of good and poor observational coverage. This is in practice an optimisation process, since better understanding of the equivalent latitude distribution of the tracer feeds back into a clearer picture of the errors in the modelled equivalent latitude coordinate. Error estimates constrain the reliability of using equivalent latitude to make statements like 'this observation samples air poleward of the vortex edge' or that of more general model-measurement comparisons. The approach is demonstrated for ground-based lidar soundings of the Mount Pinatubo aerosol cloud, focusing on the 1991-92 arctic vortex edge between 475-520K. Equivalent latitude is estimated at the observation times and locations from Eulerian model tracers initialised with PV and forced by UK Meteorological Office analyses. With the model formulation chosen, it is shown that tracer transport of a few days resulted in an error distribution that was much closer to Gaussian form, although the mean error was not significantly affected. The analysis of the observations revealed a small ...
format Article in Journal/Newspaper
author P. Good
J. Pyle
author_facet P. Good
J. Pyle
author_sort P. Good
title Refinements in the use of equivalent latitude for assimilating sporadic inhomogeneous stratospheric tracer observations, 1: Detecting transport of Pinatubo aerosol across a strong vortex edge
title_short Refinements in the use of equivalent latitude for assimilating sporadic inhomogeneous stratospheric tracer observations, 1: Detecting transport of Pinatubo aerosol across a strong vortex edge
title_full Refinements in the use of equivalent latitude for assimilating sporadic inhomogeneous stratospheric tracer observations, 1: Detecting transport of Pinatubo aerosol across a strong vortex edge
title_fullStr Refinements in the use of equivalent latitude for assimilating sporadic inhomogeneous stratospheric tracer observations, 1: Detecting transport of Pinatubo aerosol across a strong vortex edge
title_full_unstemmed Refinements in the use of equivalent latitude for assimilating sporadic inhomogeneous stratospheric tracer observations, 1: Detecting transport of Pinatubo aerosol across a strong vortex edge
title_sort refinements in the use of equivalent latitude for assimilating sporadic inhomogeneous stratospheric tracer observations, 1: detecting transport of pinatubo aerosol across a strong vortex edge
publisher Copernicus Publications
publishDate 2004
url https://doaj.org/article/016872fc515645d484734cd065ab812f
geographic Arctic
geographic_facet Arctic
genre Arctic
genre_facet Arctic
op_source Atmospheric Chemistry and Physics, Vol 4, Iss 7, Pp 1823-1836 (2004)
op_relation http://www.atmos-chem-phys.net/4/1823/2004/acp-4-1823-2004.pdf
https://doaj.org/toc/1680-7316
https://doaj.org/toc/1680-7324
1680-7316
1680-7324
https://doaj.org/article/016872fc515645d484734cd065ab812f
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