Parameterization of Atmospheric Convection: (In 2 Volumes): Volume 1: Theoretical Background and Formulation: Volume 2: Current Issues and New Theories

1169 Pages·2015·42.221 MB·English

by  Robert S Plant, Robert S Plant, Jun-Ichi Yano

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P1005hc_V1_9781783266937_tp.indd 1 30/7/15 11:14 am
Series on the Science of Climate Change
ISSN: 2045-9726
Editor: Hans-F Graf (University of Cambridge, UK)
Published
Vol. 1 Parameterization of Atmospheric Convection (In 2 Volumes)
Volume 1: Theoretical Background and Formulation
Volume 2: Current Issues and New Theories
edited by Robert S Plant and Jun-Ichi Yano
Catherine - Parameterization of Atmospheric.indd 1 28/7/2015 1:52:02 PM
P1005hc_V1_9781783266937_tp.indd 2 30/7/15 11:14 am
Published by
Imperial College Press
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Covent Garden
London WC2H 9HE
Distributed by
World Scientific Publishing Co. Pte. Ltd.
5 Toh Tuck Link, Singapore 596224
USA office: 27 Warren Street, Suite 401-402, Hackensack, NJ 07601
UK office: 57 Shelton Street, Covent Garden, London WC2H 9HE
Library of Congress Cataloging-in-Publication Data
Plant, Robert S. author
Parameterization of atmospheric convection / Robert S. Plant, Jun-Ichi Yano.
pages cm -- (Series on the science of climate change ; volume 1)
Includes bibliographical references and index.
ISBN 978-1-78326-693-7 (hardcover, v. 1 : alk. paper) --
ISBN 978-1-78326-694-4 (hardcover, v. 2 : alk. paper) --
ISBN 978-1-78326-690-6 (set : alk. paper)
1. Convection (Meteorology). 2. Atmospheric physics. 3. Weather forecasting.
I. Yano, Jun-Ichi. II. Title.
QC880.4.C64P595 2015
551.51'5--dc23
2015014333
British Library Cataloguing-in-Publication Data
A catalogue record for this book is available from the British Library.
Copyright © 2016 by Imperial College Press
All rights reserved. This book, or parts thereof, may not be reproduced in any form or by any means,
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Printed in Singapore
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Preface
In numerical modelling of weather and climate, we face an issue called
subgrid-scale physical parameterization. That is the main topic of this
two-volume set with a specific focus on convection parameterization.
Despiteitsimportanceinatmosphericmodelling,currentlyitisdifficult
to find a complete, self-contained, and up-to-date description of the con-
vection parameterization problem in the literature. Thus, the aim of this
set is to fill a gap in the literature.
In order to best fill this gap, this set takes the somewhat unusual po-
sition of considering parameterization as a theoretical problem. This is in
contrastto the commonattitude in the wider modelling community,which
usually considers it rather a purely technical problem. As a result, model
parameterizations are sometimes seen as something to be tuned and ma-
nipulated, and only in a piecemeal fashion, rather than as something fun-
damental to be periodically rethought and redeveloped. This set takes the
view that parameterization is a fundamental science problem demanding
clear and rigorous thinking and physical insight. It also intends to demon-
strate that sucha systematic approachto parameterizationdevelopmentis
indeed possible.
Clearly we have to recognize that parameterization is in some ways a
rather “messy” problem in which compromises, short-cuts, and appeals to
limited data sources are sometimes needed in order to reduce the full com-
plexityofthephysicalproblemintoaparameterizationfitforpracticaluse.
Not everything can be established in a very lucid manner as a matter of
fundamentalphysicalprinciples. Nonetheless,somebasicprinciplesforcon-
vection parameterization can clearly be set, and much valuable guidance
is available in trying to adhere to those principles as faithfully as possible
when constructing a parameterization. This approach is based on the col-
v
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vi Preface
lectiveconvictionofourgroupthatasolidtheoreticalapproachoffersgood
prospects for making faster progressona problemon which relativelyslow
progress has been made so far.
There remainplaces where we haveno suchclear-cutanswers,but only
more or less plausible alternatives, notably for issues such as closure. For
these issues, we pay great attention to some of the important technical
details that come into play, especially in operational implementations. A
few chapters are devoted to operational issues, partly for this reason.
The set focuses mainly on the deep-convection parameterization prob-
lem,andmainlyonitsmass-fluxformulation. Theshallowconvectionprob-
lem is mainly discussed in rather tangential ways throughout the text, al-
though more thorough attention is given to it in Vol. 2, Ch. 24, dedicated
to the similarity approach. This omission may be considered unfortunate
given the importance of non-precipitating shallow-convection parameter-
ization in its own right, and also its interactions with deep convection.
However, we also have to realize that shallow-convectionparameterization
along with related boundary-layer parameterizations has its own extensive
development over the years, sometimes related to but sometimes indepen-
dent of the development of deep-convection parameterizations. A full and
comprehensiveconsiderationofshallow-convectionparameterizationwould,
thus, amount to another book volume.
Webelievethatthefocusondeepconvectionisalsolegitimateconsider-
ing the fact that this was how the parameterization problem became most
acute in global atmospheric modelling in a historical context, and where
many of the most acute issues remain. Various issues are examined from
historical perspectives throughout the book, because we believe that it is
oftenimportanttoaskwherewearecomingfrominordertoknowwherewe
aregoing. Forthisreason,weoftenpayspecialattentiontosomeimportant
historicalpapers. For example,within the firstfew chapters we trace some
historical roots of the deep-convection parameterization problem through
to Riehl and Malkus’s (1958) hot-tower hypothesis. The concept of mass
flux naturally arises from this hypothesis.
The set is comprised of two volumes and has five parts. Volume 1 con-
tainsPartsIandII.PartIexaminesvariousbasicconceptsthatarecentral
forparameterizationofsubgrid-scalephysicalprocessesingeophysicalmod-
elling: scaleseparation,quasi-equilibrium,andclosure. PartIIisdevotedto
athoroughexplorationofmass-fluxconvectionparameterization. Certainly
there are alternative approaches, and these are discussed within both vol-
umes, but the mass-flux parameterization framework demands particular
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Preface vii
attention given its status as by far the most popular approach in oper-
ational models and at major climate modelling centres. Specific concepts
thatareheavilyexploitedinmass-fluxparameterizationareintroducedand
discussedoneby oneinPartII,andstrengthsandlimitations arecritically
examined.
InVolume2,weconsidertheactualbehaviourofconvectionparameter-
izationswithinthecontextthattheyarerequiredtooperate,i.e.,numerical
weatherpredictionandclimatemodels. Issueswithinournumericalmodels
and the continuing evolution of the these models pose difficult challenges
to mass-flux parameterizations. Volume 2 considers the responses to those
challenges. Furthercriticalreconsiderationsarerequiredoftraditionalcon-
cepts, and these provoke our interest in possible new frameworks.
With their increasing horizontal resolutions, a new generation of nu-
mericalmodels particularlyurges us to abandonthe traditionalframework
and assumptions arising from the concept of scale separation. How can we
construct a parameterizationwithout this concept? This challenging ques-
tion is addressed over several chapters in Part III, alongside some closely
relatedissuesconcerningtheneedtoreconsiderourstrategiesforanalysing
observations and comparing models to observations.
In Part IV we consider some alternative parameterization approaches
and formulations inspired by some of the treatments used by other param-
eterization schemes within the models, notably similarity theory for tur-
bulentflows,thelayer-cloudschemeexpressedusingdistributionfunctions,
andvariousaspectsofmicrophysicsschemes. Suchconsiderationsnaturally
lead to andaccompanydiscussions ofself-consistency in the formulationof
our models, or the lack thereof.
Finally, in Part V we explore two perspectives from theoretical physics
that seem to hold some promise for parameterization development in the
future. First, motivated by recent observational evidence, we consider a
proposalinthe recentliterature that atmosphericconvectionmayoccur at
self-organized criticality, a macroscopic state far from conventional statis-
tical equilibrium. Second, we consider some aspects of symmetry classifi-
cations for partial differential equations, which can provide constraints on
the acceptableformsofparameterizationsuchthatfundamentalproperties
ofthe originalequationsremainaspropertiesofthe parameterizedsystem.
Some examples are presented for how such theoretical and mathematical
principles can be exploited for developing solidly based parameterizations.
In order to make the book as self-contained as possible, it also covers
various related issues for deep-convection parameterization. For example,
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viii Preface
theinclusionofcloudmicrophysicsintodeepconvectionisinevitableconsid-
ering its precipitating nature. However, this raises many questions about
which microphysical processes need to be included, how they should be
represented, and how the representations can be made properly compati-
ble with the deep-convection parameterization framework. Two chapters
(Ch.18andCh.23)inVolume2aredevotedtoaself-containeddescription
of cloud microphysics.
Some special considerations are also required for verifying the perfor-
mance of convectionparameterization, especially for the precipitation field
at higher resolutions, and Ch. 21 is devoted to model validation issues.
Wealsorecognizetheimportanceofextensivelyexploitingrapidlyevolving
satelliteobservationsforthedevelopmentandverificationofconvectionpa-
rameterization. Chapter 16 discusses this promising but challenging issue.
This set is intended to be both textbook and a reference book. As a
textbook,weexpectthatitcanbeusedforaspecializedcourseatagradu-
ate level, and some selected materials could be appropriate to supplement
some undergraduate courses. For this reason, no prior knowledge of me-
teorology is assumed in most parts of the book. Certainly in places some
basic background knowledge would be helpful, say, in order to appreciate
fully a discussion about the role of convection within a certain larger-scale
phenomenon. Nonetheless, it is intended that the book should be compre-
hensibletoarelativenoviceinmeteorology. Readersare,however,assumed
to befamiliarwithbasicphysicsandmathematics,andunderthis assump-
tion, wetry to introducethe keyconcepts ofmeteorologythatarerequired
throughout the book, although often in a compact manner. We hope that
this book will prove useful not only to meteorologists who wish to develop
theirexpertiseinanimportantaspectoftheirsubject,butalsoforsomeen-
gineers and physicists interested in atmospheric modelling, who would like
to understand the details of the modelling called parameterization from a
theoretical perspective.
We should admit that not all of the background issues are carefully
introduced or explained. Some more advanced chapters in Volume 2 im-
plicitly assume knowledge not carefully introduced in earlier chapters. We
rather hope that the readers would grasp the basic concepts behind at-
mospheric modelling in the course of reading, or alternatively by following
some of the supplementary reading materials that are suggested.
As a reference book, it does not intend to replace the detailed docu-
mentation that is available for expert users or the slightly more generic
documentation that is available for user communities of existing opera-