tag:blogger.com,1999:blog-30828338149659301052023-07-18T06:06:54.359+01:00QBOi DiscussionsThe following is a forum to discuss topics and science relevant to QBOi. It's aim is to facilitate discourse between QBOi participants and those with an interest in the subject.Anonymoushttp://www.blogger.com/profile/03941743933450723234noreply@blogger.comBlogger11125tag:blogger.com,1999:blog-3082833814965930105.post-28143197720800591662015-05-28T02:59:00.001+01:002015-05-28T03:20:15.422+01:00Additional Experiments - Contrained Dynamics or "Nudging" <br />
<div class="MsoNormal" style="margin: 0in 0in 10pt;">
<span style="line-height: 115%;"><span style="font-family: Calibri;">At our March
meeting there was some interest in QBOi coordination of “nudging” or
“constrained dynamics” (CD) experiments.<span style="mso-spacerun: yes;">
</span>It was agreed that the initial QBOi focus would be on (i) long-term
“control” runs together with “global climate perturbation” runs and (ii) seasonal
hindcast experiments.<span style="mso-spacerun: yes;"> </span>These would use
some versions of the “full” GCMs with constraints imposed only on the initial
conditions and perhaps lower boundary conditions.<span style="mso-spacerun: yes;"> </span>In contrast, the CD experiments would (by
definition) involve some additional constraints on the model dynamics acting
continuously as the integration proceeds. <o:p></o:p></span></span></div>
<br />
<br />
<div class="MsoNormal" style="margin: 0in 0in 10pt;">
<span style="line-height: 115%;"><span style="font-family: Calibri;">At the
meeting we arrived at a suggested time line where at least the first group of integrations
for the (i) and (ii) experiments would take up to about 18 months (to be ready
for the fall 2016 QBOi workshop).<span style="mso-spacerun: yes;"> </span>So
there may be no urgency for QBOi to plan for CD experiments now, but this blog
posting of some general ideas of mine may start an online discussion of such
experiments for interested participants.<span style="mso-spacerun: yes;">
</span><o:p></o:p></span></span></div>
<br />
<br />
<div class="MsoNormal" style="margin: 0in 0in 10pt;">
<span style="line-height: 115%;"><span style="font-family: Calibri;">I will
consider here only CD experiments that constrain dynamical fields (horizontal
winds and possibly also temperatures) by means of a linear relaxation.<span style="mso-spacerun: yes;"> </span>The potential experiments can then be classed
by what scales are constrained (here notably either relaxation of the full 3D fields
or relaxation of only the zonal-mean fields), what height regions are
constrained (stratosphere only, toposphere only, both), what geographical
regions are constrained (tropics, extratropics, global), and what “target” the
fields are relaxed towards (climatology, actual times series of data, idealized
profiles…).<span style="mso-spacerun: yes;"> </span><o:p></o:p></span></span></div>
<br />
<br />
<h4 class="MsoNormal" style="margin: 0in 0in 10pt;">
<span style="line-height: 115%;"><em>Continuously relaxing the tropical
stratosphere zonal-mean flow<o:p></o:p></em></span></h4>
<br />
<div class="MsoNormal" style="margin: 0in 0in 10pt;">
<span style="line-height: 115%;"><span style="font-family: Calibri;">The simplest
experiments to think about are those that involve just adding an extra
zonally-symmetric momentum source so that tropical stratospheric zonal-mean
winds are forced to <o:p></o:p></span></span></div>
<br />
<div class="MsoNormal" style="margin: 0in 0in 10pt;">
<span style="line-height: 115%;"><span style="font-family: Calibri;">(a) undergo
a prescribed (idealized) QBO cycle, or<o:p></o:p></span></span></div>
<br />
<div class="MsoNormal" style="margin: 0in 0in 10pt;">
<span style="line-height: 115%;"><span style="font-family: Calibri;">(b) undergo
a QBO based on another model simulation, or<o:p></o:p></span></span></div>
<br />
<div class="MsoNormal" style="margin: 0in 0in 10pt;">
<span style="line-height: 115%;"><span style="font-family: Calibri;">(c) follow
the actual observed winds for some period, or<o:p></o:p></span></span></div>
<br />
<div class="MsoNormal" style="margin: 0in 0in 10pt;">
<span style="line-height: 115%;"><span style="font-family: Calibri;">(d) remain
nearly constant. i.e. held to some specified profile.</span></span></div>
<div class="MsoNormal" style="margin: 0in 0in 10pt;">
<span style="line-height: 115%;"><span style="font-family: Calibri;"><o:p></o:p></span></span> </div>
<br />
<div class="MsoNormal" style="margin: 0in 0in 10pt;">
<span style="line-height: 115%;"><span style="font-family: Calibri;">There are several
such experiments already reported in the literature (for example Kodera et al.,
1991; Hamilton, 1995, 1998; Balachandran and Rind, 1995; Giorgetta &
Bengtsson, 1999; Bruhwiler & Hamilton, 1999;<span style="mso-spacerun: yes;"> </span>Hamilton et al., 1984; Stenchikov et al.,
1984; Thomas et al., 2008; Mathes et al, 2010; Garfinkel & Hartman,
2011).<span style="mso-spacerun: yes;"> </span>We can imagine that the extra
forcing of the mean zonal momentum accounts for missing (or misrepresented)
eddy fluxes, and so <i style="mso-bidi-font-style: normal;">conceptually</i>
these experiments are somewhat similar to model simulations with QBOs generated
by highly tuned nonstationary gravity wave parameterizations.<span style="mso-spacerun: yes;"> </span>However by using relaxation to a prescribed “target”
wind field, these experiments could provide a suite of simulations performed with
different models, but with nearly identical mean flow profiles in the tropical
stratosphere through which waves will propagate.<span style="mso-spacerun: yes;"> </span>By choosing an appropriate “target” to relax
towards we can also ensure that the stratospheric mean winds in the models will
be quite realistic.<span style="mso-spacerun: yes;"> </span></span></span></div>
<br />
<h4 class="MsoNormal" style="margin: 0in 0in 10pt;">
<span style="line-height: 115%;"><em>Nudging the troposphere<o:p></o:p></em></span></h4>
<br />
<div class="MsoNormal" style="margin: 0in 0in 10pt;">
<span style="line-height: 115%;"><span style="font-family: Calibri;">A set of
possibly interesting experiments could result from nudging the tropospheric
fields towards observations.<span style="mso-spacerun: yes;"> </span>This might
be most plausibly done with some kind of prescribed relaxation of the full 3D
wind and temperature field towards some global reanalysis product.<span style="mso-spacerun: yes;"> </span>This could, in principle, let one compare the
stratospheric simulation among e.g. different versions of one model with
different vertical resolutions,<span style="mso-spacerun: yes;"> </span>or
different models all with the resolved (or at least sufficiently large scale)
wave fluxes expected to be realistic.<span style="mso-spacerun: yes;"> </span>I
believe something like this approach has been tried (e.g. by a Canadian group
some years ago?), but I can’t easily locate relevant references. Of course
there are problematic aspects as well, notably how the convection
parameterization in each model will react with an effectively “imposed”
horizontal divergence.<span style="mso-spacerun: yes;"> </span><o:p></o:p></span></span></div>
<br />
<h4 class="MsoNormal" style="margin: 0in 0in 10pt;">
<span style="line-height: 115%;"><em>Nudging to produce initial conditions for
free running integrations<o:p></o:p></em></span></h4>
<br />
<div class="MsoNormal" style="margin: 0in 0in 10pt;">
<span style="line-height: 115%;"><span style="font-family: Calibri;">As was
discussed in Victoria, a focus of the initial stage of QBOi will be
on seasonal hindcasts from realistic initial conditions.<span style="mso-spacerun: yes;"> </span>Some centers are no doubt set up to easily
start their models from a realistic initial state.<span style="mso-spacerun: yes;"> </span>Another option that some groups could conceivably
adopt is producing an initial state by running their model for some time with
3D relaxation to global reanalyses, and then at t=0 turning off the relaxation and
beginning the hindcast.<span style="mso-spacerun: yes;"> </span>So one application of
this approach might be for some groups to participate in the QBOi “realistic” hindcast experiments,
but one could also imagine this machinery being used for other
experiments.<span style="mso-spacerun: yes;"> </span>For example one could
compare two hindcasts made with the same model: (i) with the full 3D fields “initialized”
this way, and (ii) with just the tropical stratosphere (or even just the tropical
stratospheric zonal-mean flow) initialized.<span style="mso-spacerun: yes;">
</span>This would allow one to see how dependent the evolution of the
zonal-mean equatorial stratospheric flow is on the details of the day to day
weather situation in the troposphere.<span style="mso-spacerun: yes;"> </span><span style="mso-spacerun: yes;"> </span><o:p></o:p></span></span></div>
<br />
<div class="MsoNormal" style="margin: 0in 0in 10pt;">
<span style="line-height: 115%;"><o:p><span style="font-family: Calibri;"> </span></o:p></span></div>
<br />
<div class="MsoNormal" style="margin: 0in 0in 10pt; text-align: center;">
<b style="mso-bidi-font-weight: normal;"><span style="line-height: 115%;"><span style="font-family: Calibri;">References<o:p></o:p></span></span></b></div>
<br />
<div class="MsoNormal" style="margin: 0in 0in 10pt;">
<span style="line-height: 115%;"><span style="font-family: Calibri;">Balachandran,
N. K., and D. Rind, 1995: Modeling the effects of solar variability and the QBO
on the troposphere/stratosphere system. Part I: The middle atmosphere. <i style="mso-bidi-font-style: normal;">J. Climate</i>, <strong>8</strong>, 2058–2079.<o:p></o:p></span></span></div>
<br />
<div class="MsoNormal" style="margin: 0in 0in 10pt;">
<span style="line-height: 115%;"><span style="font-family: Calibri;">Bruhwiler,
L.P., and K. Hamilton, 1999: A numerical simulation of the stratospheric ozone
quasi-biennial oscillation using a comprehensive general circulation model. <span style="mso-spacerun: yes;"> </span><i style="mso-bidi-font-style: normal;">J.
Geophys. Res</i>., <strong>104</strong>, 30,525–30,557.<o:p></o:p></span></span></div>
<br />
<div class="MsoNormal" style="margin: 0in 0in 10pt;">
<span style="line-height: 115%;"><span style="font-family: Calibri;">Garfinkel,
C.I., and D.L. Hartmann, 2011: The influence of the Quasi-Biennial Oscillation
on the troposphere in winter in a hierarchy of models. Part II: Perpetual
winter WACCM runs<i style="mso-bidi-font-style: normal;">. <span style="mso-spacerun: yes;"> </span>J. Atmos. Sci.,</i> <strong>68</strong>, 2026-2041.<o:p></o:p></span></span></div>
<br />
<div class="MsoNormal" style="margin: 0in 0in 10pt;">
<span style="line-height: 115%;"><span style="font-family: Calibri;">Giorgetta,
M., and L. Bengtsson, 1999: The potential role of the quasi-biennial
oscillation in the stratosphere-troposphere exchange as found in water vapour
in general circulation model experiments. <span style="mso-spacerun: yes;"> </span><i style="mso-bidi-font-style: normal;">J. Geophys.
Res</i>., <strong>104</strong>, 6003–6019.<o:p></o:p></span></span></div>
<br />
<div class="MsoNormal" style="margin: 0in 0in 10pt;">
<span style="line-height: 115%;"><span style="font-family: Calibri;">Hamilton,K.,
1995: Interannual variability in the Northern Hemisphere winter middle
atmosphere in control and perturbed experiments with the SKYHI general
circulation model<i style="mso-bidi-font-style: normal;">. J. Atmos. Sci</i>., <strong>52</strong>,
44–66<o:p></o:p></span></span></div>
<br />
<div class="MsoNormal" style="margin: 0in 0in 10pt;">
<span style="line-height: 115%;"><span style="font-family: Calibri;">Hamilton, K.,
1998: Effects of an imposed Quasi-Biennial Oscillation in a comprehensive troposphere–stratosphere–mesosphere
General Circulation Model. <span style="mso-spacerun: yes;"> </span><i style="mso-bidi-font-style: normal;">J. Atmos. Sci</i>., <strong>55</strong>, 2393–2418.<o:p></o:p></span></span></div>
<br />
<div class="MsoNormal" style="margin: 0in 0in 10pt;">
<span style="line-height: 115%;"><span style="font-family: Calibri;">Hamilton,
K., A. Hertzog, F. Vial, and G. Stenchikov, 2004: Longitudinal variation of the
stratospheric Quasi-Biennial Oscillation<i style="mso-bidi-font-style: normal;">.
<span style="mso-spacerun: yes;"> </span>J. Atmos. Sci</i>., <strong>61</strong>, 383–402<o:p></o:p></span></span></div>
<br />
<div class="MsoNormal" style="margin: 0in 0in 10pt;">
<span style="line-height: 115%;"><span style="font-family: Calibri;">Kodera, K., Chiba,
M., & Shibata, K., 1991: A general circulation model study of the solar and
QBO modulation of the stratospheric circulation during the Northern Hemisphere
winter. <i style="mso-bidi-font-style: normal;">Geophys. Res. Lett.</i>, <strong>18</strong>,
1209-1212.<o:p></o:p></span></span></div>
<br />
<div class="MsoNormal" style="margin: 0in 0in 10pt;">
<span style="line-height: 115%;"><span style="font-family: Calibri;">Matthes, K.,
D.R. Marsh, R.R. Garcia, D.E. Kinnison, F. Sassi, and S. Walters, 2010: Role of
the QBO in modulating the influence of the 11-year solar cycle on the
atmosphere using constant forcings. <i style="mso-bidi-font-style: normal;">J.
Geophys. Res</i>., <strong>115</strong>, D18110, doi:10.1029/2009JD013020.<o:p></o:p></span></span></div>
<br />
<div class="MsoNormal" style="margin: 0in 0in 10pt;">
<span style="line-height: 115%;"><span style="font-family: Calibri;">Stenchikov,
G., K. Hamilton, A. Robock, V. Ramaswamy, and M.D. Schwarzkopf, 2004: Arctic
oscillation response to the 1991 Pinatubo eruption in the SKYHI general
circulation model with a realistic quasi-biennial oscillation, <i style="mso-bidi-font-style: normal;">J. Geophys. Res.,</i> <strong>109</strong>, D03112,
doi:10.1029/2003JD003699.</span></span><br />
<span style="line-height: 115%;"><span style="font-family: Calibri;"></span></span><br />
<span style="line-height: 115%;"><span style="font-family: Calibri;">Thomas, M.A., M.A. Giorgetta, C. Timmreck, H.F. Graf & G. Stenchikov, 2008: Simulation of the climate impact of Mt. Pinatubo eruption using ECHAM5: Part 2: Sensitivity to the phase of the QBO. <em>Atmos. Chem. Phys. Discussions</em>, <strong>8</strong>, 9239-9261.</span></span></div>
<br />Anonymoushttp://www.blogger.com/profile/14934792439814338154noreply@blogger.com0tag:blogger.com,1999:blog-3082833814965930105.post-32743748807267297682015-05-14T14:23:00.001+01:002015-05-14T19:43:21.796+01:00Overview<i><span style="color: yellow; font-family: Times, Times New Roman, serif;">Version 1.0 Drafted by <u>John Scinocca, Tim Stockdale & Francois Lott</u></span></i><br />
<i><span style="color: yellow; font-family: Times, Times New Roman, serif;"><u><br /></u></span></i>
<span style="font-family: Times, Times New Roman, serif;">This is a draft protocol for a set of five QBO experiments, and is based on the outcome of discussions at the QBO Modeling and Reanalyses Workshop, Victoria, March 2015. The motivations and goals of the experiments are described below, followed by the technical specification of the experiments and information on data and diagnostics. The experiments themselves are designed to be simple and accessible to a wide range of groups.</span><br />
<span style="font-family: Times, Times New Roman, serif;"><br /></span>
<span style="font-family: Times, Times New Roman, serif;"></span><br />
<span style="font-family: Times, Times New Roman, serif;">It is expected that each group will submit a set of results from all the experiments, made with a single “best shot” model version. Use of the same model version for the different experiments is crucial for learning the most from this study. </span>Anonymoushttp://www.blogger.com/profile/03941743933450723234noreply@blogger.com0tag:blogger.com,1999:blog-3082833814965930105.post-77117657978042241252015-05-14T14:20:00.002+01:002015-05-14T19:43:52.202+01:00Experiment List & Goals<i><span style="color: yellow; font-family: Times, Times New Roman, serif;">Version 1.0 Drafted by <u>John Scinocca, Tim Stockdale & Francois Lott</u></span></i><br />
<i><span style="color: yellow; font-family: Times, Times New Roman, serif;"><u><br /></u></span></i>
<span style="font-family: Times, Times New Roman, serif;"><i>a) Present-Day Climate: Identify and distinguish the properties of and mechanisms underlying the different model simulations of the QBO in present-day conditions:</i></span><br />
<span style="font-family: Times, Times New Roman, serif;"><br /></span>
<span style="font-family: Times, Times New Roman, serif;"><span style="color: yellow;">EXPERIMENT 1</span>: AMIP – specified interannually varying SSTs, sea ice, and external forcings</span><br />
<span style="font-family: Times, Times New Roman, serif;"><br /></span>
<span style="font-family: Times, Times New Roman, serif;"><span style="color: yellow;">EXPERIMENT 2</span>: 1xCO2 - identical simulation to the AMIP above except employing repeated annual cycle SSTs, sea ice, and external forcings</span><br />
<span style="font-family: Times, Times New Roman, serif;"><br /></span>
<span style="font-family: Times, Times New Roman, serif;">These experiments will allow an evaluation of the realism of modelled QBOs under present-day climate conditions, employing diagnostics and metrics discussed in Section 5. The impact of interannual forcing on the model QBO can also be assessed, and Experiment 2 is a control for the climate projection experiments. </span><br />
<span style="font-family: Times, Times New Roman, serif;"><br /></span>
<span style="font-family: Times, Times New Roman, serif;"><i>b) Climate Projections: Subject each modelled QBO contribution to an external forcing that is similar to that typically applied for climate projections:</i></span><br />
<span style="font-family: Times, Times New Roman, serif;"><br /></span>
<span style="font-family: Times, Times New Roman, serif;"><span style="color: yellow;">EXPERIMENT 3</span>: 2xCO2 - identical to Experiment 2, but with a change in CO2 concentration and specified SSTs and sea ice appropriate for a 2xCO2 world</span><br />
<span style="font-family: Times, Times New Roman, serif;"><br /></span>
<span style="font-family: Times, Times New Roman, serif;"><span style="color: yellow;">EXPERIMENT 4</span>: 4xCO2 - identical to Experiment 2 but with a change in CO2 concentration and specified SSTs and sea ice appropriate for a 4xCO2 world</span><br />
<span style="font-family: Times, Times New Roman, serif;"><br /></span>
<span style="font-family: Times, Times New Roman, serif;">The response of the QBO, its forcing mechanisms, and its impact/influence will be evaluated by the same set of diagnostics used for diagnosing Experiments 1 and 2, but representing the response 2xCO2 - 1xCO2 and 4xCO2 - 1xCO2. Obvious questions that will arise:</span><br />
<span style="font-family: Times, Times New Roman, serif;"><br /></span>
<br />
<ul>
<li><span style="font-family: Times, Times New Roman, serif;">What is the spread/uncertainty of the forced model response?</span></li>
<li><span style="font-family: Times, Times New Roman, serif;">Do different model contributions cluster in any particular way?</span></li>
<li><span style="font-family: Times, Times New Roman, serif;">Can a connection/correlation be made between QBOs with similar metrics/diagnostics in present day climate and their response to CO2 forcing?</span></li>
</ul>
<br />
<span style="font-family: Times, Times New Roman, serif;"><br /></span>
<span style="font-family: Times, Times New Roman, serif;">The hope is that this sort of sensitivity experiment might indicate what aspects of modelled QBOs determine the spread, or uncertainty, of the QBO response to CO2 forcing. These aspects are the ones which should receive the most attention by QBOi in order to reduce uncertainty in future projections. Such experiments also will inform the community as to what the general uncertainty might be for state-of-the-art QBOs in CMIP6 projection experiments.</span><br />
<span style="font-family: Times, Times New Roman, serif;"><br /></span>
<span style="font-family: Times, Times New Roman, serif;"><i>c) QBO Predictions and process study: Evaluate and compare the predictive skill of modelled QBOs in a seasonal prediction hindcast context, and study the model processes driving the evolution of the QBO.</i></span><br />
<span style="font-family: Times, Times New Roman, serif;"><br /></span>
<span style="font-family: Times, Times New Roman, serif;"><span style="color: yellow;">EXPERIMENT 5</span>: A set of initialized QBO hindcasts, with 9-12 month range. Observed SSTs and forcings specified as in Experiment 1 (these are diagnostic experiments), with reanalysis data for the atmosphere inserted at a set of given start dates.</span><br />
<span style="font-family: Times, Times New Roman, serif;"><br /></span>
<span style="font-family: Times, Times New Roman, serif;">These are not strictly prediction experiments in the seasonal forecast sense (they use prescribed observed SST), but still represent a challenge as to how well the models can predict the evolution of the QBO from specified initial conditions. Obvious questions that will arise:</span><br />
<span style="font-family: Times, Times New Roman, serif;"><br /></span>
<br />
<ul>
<li><span style="font-family: Times, Times New Roman, serif;">How much does model prediction skill vary between models, and to what extent are models able to predict the QBO evolution correctly at different vertical levels and different phases of the QBO?</span></li>
<li><span style="font-family: Times, Times New Roman, serif;">How does the forecast skill relate to the behaviour of the QBO in Experiment 1? Does a realistic QBO in a long model run guarantee good predictions, or vice versa, or neither?</span></li>
<li><span style="font-family: Times, Times New Roman, serif;">Do the models that cluster and/or do well in the prediction experiments cluster in the CO2 forcing experiments?</span></li>
</ul>
<br />
<span style="font-family: Times, Times New Roman, serif;"><br /></span>
<span style="font-family: Times, Times New Roman, serif;">The hope is that this sort of prediction experiment might indicate what aspects of modelled QBOs determine the quality of QBO prediction, so that these aspects can receive attention in order to improve prediction. Alternatively, the prediction framework may be helpful for directly assessing model changes, to help drive improvements in free-running models. Can prediction experiments help narrow the range of plausible models for climate change experiments?</span><br />
<span style="font-family: Times, Times New Roman, serif;"><br /></span>
<span style="font-family: Times, Times New Roman, serif;">Process Studies: Experiment 5 has a dual purpose: it not only provides information on the predictive capabilities of the models, it offers a unique opportunity to investigate and evaluate differences in wave dissipation and momentum deposition, so as to understand the processes driving the QBO in each model. The initialization of the seasonal forecasts will necessarily present each QBO contribution with the same basic state. The evolution of that state immediately after the start of the forecast offers an opportunity to compare and contrast the properties of wave dissipation and momentum deposition between different models given an identical basic state. Specifying the same observed SST in all models (rather than allowing each model to predict its own SST evolution) helps focus attention on the model mechanisms that drive the QBO, and the extent to which they are correctly represented.</span><br />
<span style="font-family: Times, Times New Roman, serif;"><br /></span>
<span style="font-family: Times, Times New Roman, serif;"></span><br />
<span style="font-family: Times, Times New Roman, serif;">It is likely that a special, high-frequency, data request for an early period of each forecast should be defined which focuses on dissipation processes for this study.</span><br />
<div>
<br /></div>
Anonymoushttp://www.blogger.com/profile/03941743933450723234noreply@blogger.com0tag:blogger.com,1999:blog-3082833814965930105.post-56747201816486589592015-05-14T14:16:00.001+01:002015-05-14T19:44:21.146+01:00Experiment Details<i><span style="color: yellow; font-family: Times, Times New Roman, serif;">Version 1.0 Drafted by <u>John Scinocca, Tim Stockdale & Francois Lott</u></span></i><br />
<br />
Five sets of simulations/experiments have been defined above:<br />
<br />
- <span style="color: yellow;">EXPERIMENT 1</span> - AMIP, interannually varying SSTs, sea ice, and external forcing<br />
- <span style="color: yellow;">EXPERIMENT 2</span> - 1xCO2, repeated annual cycle SSTs, sea ice, and external forcings<br />
- <span style="color: yellow;">EXPERIMENT 3</span> - 2xCO2, as EXPT 2 with perturbed SSTs and sea ice and 2xCO2<br />
- <span style="color: yellow;">EXPERIMENT 4</span> - 4xCO2, as EXPT 2 with perturbed SSTs and sea ice and 4xCO2<br />
- <span style="color: yellow;">EXPERIMENT 5</span> - QBO hindcasts, with reanalysis initial conditions on specified start dates.<br />
<br />
For all experiments it is requested that all modelling groups use the same set of SST and sea ice boundary conditions, as specified below. External forcings should be followed to the extent possible, although it is recognized that models may vary in how they specify aerosols, volcanic forcing etc. For the purposes of these experiments (sensitivity studies of the QBO), what matters is that the external forcing remains constant when it is supposed to be constant, and varies as realistically as the model allows when it is supposed to vary. In all cases, the experiments are intended to be made using only reasonable efforts. Any changes in experimental details should be documented.<br />
<br />
Ensemble sizes are given as a range, from minimum to preferred size. Each group should assess what is reasonable, given costs, resources and expected results (e.g. some models may have a highly regular or phase-locked QBO).<br />
<br />
<b><span style="color: yellow;">EXPERIMENT 1</span> - AMIP Cost: 30-90y</b><br />
<br />
This is based on the CMIP5: Expt 3.3<br />
<br />
Period: 30y (1979-2008)<br />
<br />
Ensemble size: 1-3<br />
<br />
Boundary Conditions: CMIP5 interannually varying sea ice and SSTs obtained from:<br />
<br />
http://www-pcmdi.llnl.gov/projects/amip/AMIP2EXPDSN/BCS/amipbc_dwnld.php<br />
<br />
External Forcings: CMIP5 external forcings for radiative trace gas concentrations, aerosols, solar, explosive volcanoes etc. obtained from: http://cmip-pcmdi.llnl.gov/cmip5/forcing.html#amip<br />
<br />
<b><span style="color: yellow;">EXPERIMENT 2</span> - 1xCO2 Cost: 30-90y</b><br />
<br />
Repeated annual cycle simulation.<br />
<br />
Period: 30y, after a suitable spinup (5y?).<br />
<br />
Ensemble size: 1-3<br />
<br />
Boundary Conditions: CMIP5 "SST Climatology 1988-2007" and "SEA ICE Climatology 1988-2007" obtained from:<br />
<br />
http://www-pcmdi.llnl.gov/projects/amip/AMIP2EXPDSN/BCS/amipbc_dwnld.php<br />
<br />
External Forcings: repeated annual cycle forcings. Ideally this would be some sort of climatological forcing averaged over the 30 year period used in EXPT1, but that doesn't really exist. The suggestion is to use year 2002 of the CMIP5 external forcings:<br />
<br />
http://cmip-pcmdi.llnl.gov/cmip5/forcing.html#amip<br />
<br />
The year 2002 has neutral ENSO, neutral PDO, and is well-away from any historical explosive volcanoes. Since this experiment will be the base for the 2xCO2/4xCO2 experiments, a constant value of CO2 corresponding to the average over the year 2002 should be used. Note that although these choices are not ideal (the 30 year comparison period, the 20 year SST climatology and the 2002 fixed forcing are all inconsistent with each other), the observed dependence of the QBO on changing climate through this period appears to be negligible. Thus for QBO purposes (and in particular for comparing model responses) the protocol is believed adequate, if all models use the same approach.<br />
<br />
<b><span style="color: yellow;">EXPERIMENTS 3 and 4</span> - 2xCO2 / 4xCO2 Cost: 60-180y</b><br />
<br />
Period: 30y, after suitable spinup<br />
<br />
Ensemble size: 1-3<br />
<br />
Boundary Conditions: repeated annual cycle of SSTs and sea ice will be provided to modelling centres on a 1x1 degree grid as in Experiments 1 and 2. The proposal is to use an ensemble average over the CMIP5 models average over the decade centred on the time of CO2 doubling/quadrupling in the RCP8.5 scenario. [In practice we may use the decades 2050-60 and 2090-2100 from RCP8.5 runs, since 4xCO2 occurs a little later than 2100. But this dataset will be prepared centrally, to ensure we all use the same values].<br />
<br />
External Forcings: the forcings in these two experiments should be exactly the same as used in EXPT 2 except for the CO2 concentration, which should be doubled and quadrupled. Only CO2 forcings should be changed, not other greenhouse gases. These are sensitivity experiments, not attempts to predict specific periods in the future.<br />
<br />
<b><span style="color: yellow;">EXPERIMENT 5</span> - QBO hindcasts Cost: 68-150y</b><br />
<br />
These are atmosphere-only experiments, initialized from re-analysis data, providing multiple short integrations from a relatively large set of start dates sampling different phases of the QBO.<br />
<br />
Start dates: 1 May and 1 November in each of the years 1993-2007 (15 years, 30 start dates)<br />
<br />
Hindcast length: 9-12 months<br />
<br />
Ensemble size: 3-5 members<br />
<br />
The boundary conditions and forcings for this experiment closely follows the prescription of the AMIP experiment (EXPT 1).<br />
<br />
Boundary Conditions: CMIP5 interannually varying sea ice and SSTs obtained from:<br />
http://www-pcmdi.llnl.gov/projects/amip/AMIP2EXPDSN/BCS/amipbc_dwnld.php<br />
<br />
External Forcings: CMIP5 external forcings for radiative trace gas concentrations, aerosols, solar, explosive volcanoes etc. obtained from:<br />
http://cmip-pcmdi.llnl.gov/cmip5/forcing.html#amip<br />
<br />
Initial data for these dates should be taken from the ERA-interim reanalysis. ERA-interim data is available for download from apps.ecmwf.int/datasets (registration is required; if downloading lots of start dates from this site, it may be easier to use the “batch access” method described on the site, although interactive download of each date is also possible. Data are available on either standard pressure levels or original model levels, and in either grib or netCDF. Try to download only the data you need, e.g. at 0 z on the 1st of the month).<br />
<br />
The ensemble is expected to be generated by perturbing each ensemble member by a small anomaly, which needs do no more than change the bit pattern of the simulation.<br />
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Anonymoushttp://www.blogger.com/profile/03941743933450723234noreply@blogger.com4tag:blogger.com,1999:blog-3082833814965930105.post-16463873829463325472015-05-14T14:07:00.004+01:002015-05-14T19:44:47.142+01:00Additional Experiments<i><span style="color: yellow; font-family: Times, Times New Roman, serif;">Version 1.0 Drafted by <u>John Scinocca, Tim Stockdale & Francois Lott</u></span></i><br />
<br />
Some groups may want to conduct additional experiments, to provide further information on the sensitivity of the results to various factors.<br />
<br />
<b><span style="color: yellow;">EXPERIMENT 5A</span>:</b> As EXPT5, but using a coupled ocean-atmosphere model and predicting the SST, instead of specifying observed values. External forcings could also be fixed so as not to use future information. This is then a true forecast experiment for the QBO, and can be compared with the results of EXPT5.<br />
<br />
Further, groups may want to run some or all of the experiments with multiple model versions, to explore the sensitivity of some of the results e.g. to vertical resolution or physics package. Although ideally all experiments would be re-run, this may not be practical. Model versions for which complete experiment sets are available are likely to be considered the “primary” results when analysis takes place.<br />
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Anonymoushttp://www.blogger.com/profile/03941743933450723234noreply@blogger.com0tag:blogger.com,1999:blog-3082833814965930105.post-37170429937680220882015-04-24T11:58:00.004+01:002015-05-14T19:45:16.600+01:00Requested Diagnostics<i><span style="color: yellow; font-family: Times, Times New Roman, serif;">Version 1.0 Drafted by <u>John Scinocca, Tim Stockdale & Francois Lott</u></span></i><br />
<span style="font-family: Times, Times New Roman, serif;"><br /></span>
<span style="font-family: Times, Times New Roman, serif;">Input to this and a discussion of the rationale has been provided by Francois Lott: see http://qboiexperiments.blogspot.co.uk/. The text is reproduced below for convenience. This will need to be turned into a specific list of variables and pressure levels to be saved, for both “standard” and “high frequency” diagnostics, and agreement on which parts of EXPTS 1-5 should have high-frequency output archived. This document will be updated with a specific proposal in due course.</span><br />
<span style="font-family: Times, Times New Roman, serif;"><br /></span>
<span style="font-family: Times, Times New Roman, serif;">Storage is available at BADC, and it is proposed that groups upload their data in a common format (CF compliant netCDF) to BADC. This will involve registering to obtain an account, and preparing datasets to the specified common format. Please contact Scott Osprey for further details.</span><br />
<span style="font-family: Times, Times New Roman, serif;"><br /></span>
<span style="font-family: Times, Times New Roman, serif;">It will facilitate comparisons if the data are on a common lat-long grid, as well as being on standard pressure levels. SNAP specified a 1.5 deg grid, which is probably adequate for this project, too. (ERAI uses a 0.75 deg standard lat-long grid).</span><br />
<span style="font-family: Times, Times New Roman, serif;"><br /></span>
<span style="font-family: Times, Times New Roman, serif;">Are there any fields which should be supplied on the original model grid as well as a standard lat-long grid?</span><br />
<div>
<span style="font-family: Times, Times New Roman, serif;"><br /></span></div>
<span style="font-family: Times, Times New Roman, serif;"><br /></span>
<br />
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<i><span style="color: yellow; font-family: Times, Times New Roman, serif;">Text from <u><b>Francois Lott:</b></u></span></i><br />
<span style="font-family: Times, Times New Roman, serif;"><br />
Here is a table of diagnostics, which include the diagnostics requested by the ISSI group initiated by
Joan Alexander a couple of years ago, and from which I started. What I remember from our discussions during
the QBOi workshop, is that each group makes a simulation with its best QBO (not necessarily a
version suited to CMIP6), and over 30 years (more maybe for histograms and spread?) store at
pressure levels as near as they can be from the model levels and between 0.01 and 1000hPa,
monthly-mean zonal mean data of:</span><br />
<span style="font-family: Times, Times New Roman, serif;"><br />
u, du/dt, T, v*, w*, F_phi, F_z, divF, G_ogw, G_ngw</span><br />
<span style="font-family: Times, Times New Roman, serif;"><br />
</span><br />
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<span style="font-family: Times, Times New Roman, serif;">Here the time derivative of the mean velocity (dynamical tendency) is to try to make the difference
between the advective terms we can deduce from the TEM equations, and the advective plus forcing
terms due to explicit/numerical diffusions which are sometimes difficult to extract from models. Also, we nead the EPF divergence (EPFD), and the tendencies due to the
orographic and non-orographic gravity waves G_ogw, G_ngw</span><br />
<span style="font-family: Times, Times New Roman, serif;"><br />
Also, it is useful to have the eastward and westward component of the non-orographic GWs
momentum fluxes, rho_0*\bar{u'w'}_egw, rho_0*\bar{u'w'}_wgw</span><br />
<span style="font-family: Times, Times New Roman, serif;"><br />
</span><br />
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<span style="font-family: Times, Times New Roman, serif;">We could repeat this in 2XCO2+2K SST and 4XCO2+4K SST to see how our QBOs respond to
climate change: there seems to be large spread amoing models.
</span><br />
<span style="font-family: Times, Times New Roman, serif;"><br />
Now, from the QBOi workshop I remember that we need to no know if our models simulate the
QBO for the right (or the same reasons) and in particular the fraction of the resolved waves in each
models. For this, the EPFD may not be sufficient, and the EPF themselves can include large
opposing balance so we have to calculate time-wavenumber spectra of EPF, and this request storage
of <span style="font-weight: 700;">instantaneous </span>values of u, w, v, and T at pressure levels, every three hours (to be discussed,
1hr?) and during at least one QBO period (for instance over three years). In my opinion, this needs to be done over a good number of levels in the QBO regions, above and below, for instance (to be
discussed):
</span><br />
<span style="font-family: Times, Times New Roman, serif;"><br />
200hPa<span style="font-style: italic;">,</span>150hPa<span style="font-style: italic;">,</span>100hPa<span style="font-style: italic;">,</span>70hPa<span style="font-style: italic;">,</span>50hPa<span style="font-style: italic;">,</span>30hPa<span style="font-style: italic;">,</span>20hPa<span style="font-style: italic;">,</span>15hPa<span style="font-style: italic;">,</span>10hPa<span style="font-style: italic;">,</span>5hPa<span style="font-style: italic;">,</span>2hPa<span style="font-style: italic;">,</span>1hPa<br />
Why many levels: 1) to make better than the spectra in Horinoushi et al.~(2003) on top of the fact
that we now all have a QBO (which was not the case in the 2003, paper); 2) A big question is to
know how fast the equatorial waves dissipate in the vertical in the QBO region, 3) understand the
behaviour around the TTL and in the SAO region. Differences between vertical levels may also
help reduce the contribution of the tidal signals in the time-lon spectra, something that can be
problematic at sub-diurnal periods (true?).
</span><br />
<span style="font-family: Times, Times New Roman, serif;"><br />
My rough estimate for one model is almost 500GB if we stay on netcdf format. But this opens the
debate (3years of u,v,w,T at 12 vertical levels, 160x90 horizontal levels, every 3hrs).
</span><br />
<span style="font-family: Times, Times New Roman, serif;"><br />
Also, we would need a good deal of 2D fields, like precipitation, convective prec, OLR, etc.
Information on the vertical structure of the tropical heating would be useful also, but I have no especially precise idea right now of about this should be done.
</span><br />
<span style="font-family: Times, Times New Roman, serif;"><br />
</span></div>
</div>
</div>
<span style="font-family: Times, Times New Roman, serif;">All diagnostics are done according to the TEM formalism as described in, Middle atmosphere
dynamics. By D. G. Andrews, J. R. Holton and C. B. Leovy. Academic Press, San Diego, 1987 </span><br />
<span style="font-family: Times, Times New Roman, serif;"><br />
Horinouchi, T., S. Pawson, K. Shibata, E. Manzini, M.A. Giorgetta, F. Sassi, R. J. Wilson, K.</span><br />
<span style="font-family: Times, Times New Roman, serif;">Hamilton, J. DeGrandpe and A.A. Scaife, 2003: Tropical cumulus convection and upward propagating waves in middle-atmospheric GCMs, J. Atmos. Sci. , 60, 2765—2782.</span><br />
<span style="font-family: Times, Times New Roman, serif;"><br />
Some spectra/composites from CMIP5 models are in:</span><br />
<span style="font-family: Times, Times New Roman, serif;"><br />
</span><br />
<span style="font-family: Times, Times New Roman, serif;">Lott, F. S. Denvil , N. Butchart, C. Cagnazzo , M. Giorgetta, S. Hardiman, E. Manzini, T. T. Krishmer , J.-P. Duvel, P. Maury, J. Scinocca, S. Watanabe, S. Yukimoto, 2014: Kelvin and Rossby gravity wave packets in the lower stratosphere of some high-top CMIP5 models, J. Geophys. Res., 119, 5, 2156-2173, DOI: 10.1002/2013JD020797</span></div>
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Anonymoushttp://www.blogger.com/profile/03941743933450723234noreply@blogger.com1tag:blogger.com,1999:blog-3082833814965930105.post-15287643289129430682015-03-25T10:47:00.003+00:002015-05-14T14:28:12.573+01:00Additional Experiment - Dynamical CoresThese experiments investigate the sensitivity of QBO-like variability in GCM dynamical cores to changes/representations of numerics and resolution.<br />
<br />
<span style="color: yellow; font-family: Georgia, Utopia, Palatino Linotype, Palatino, serif;"><span style="font-size: 15px; line-height: 20px;"><b>A first draft for this experiment is being prepared by Christiane Jablonowski and will appear here shortly. At this time wider discussion will be encouraged to best facilitate wider participation within the group.</b></span></span>Anonymoushttp://www.blogger.com/profile/03941743933450723234noreply@blogger.com0tag:blogger.com,1999:blog-3082833814965930105.post-73414978324862442252015-03-25T10:41:00.003+00:002015-05-14T14:28:12.578+01:00Additional Experiment - Nudging to Specifiy DynamicsThe following experiments are suggested for interested groups. These investigate the role of feedbacks in maintaining the QBO. The general idea would be to alter model physics or numerics while maintaining the zonal mean state. This technique will isolate the resolved wave response without feedbacks from the changing zonal men state. Possible experiments might include:<br />
<br />
<ul>
<li>nudging zonal-mean conditions in the tropical stratosphere</li>
<li>nudging aspects of the tropical troposphere</li>
</ul>
<div>
<span style="color: yellow; font-family: Georgia, Utopia, Palatino Linotype, Palatino, serif;"><span style="font-size: 15px; line-height: 20px;"><b>A first draft for this experiment is being prepared by Kevin Hamilton and will appear here shortly. At this time wider discussion will be encouraged to best facilitate wider participation within the group.</b></span></span></div>
Anonymoushttp://www.blogger.com/profile/03941743933450723234noreply@blogger.com1tag:blogger.com,1999:blog-3082833814965930105.post-63643185374991749692013-11-07T12:51:00.001+00:002015-05-14T14:27:17.970+01:00ExperimentsThe objective of QBOi is to evaluate the sensitivity dependencies of tropical stratosphere variability within current global climate models. In so doing, we anticipate learning more about the modelled dynamics and variability of the tropical stratosphere. On a practical level, it is hoped this project will help improve QBO modelling in time for CMIP6.<br />
<span class="Apple-style-span" style="-webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469); -webkit-tap-highlight-color: rgba(26, 26, 26, 0.296875);"><br /></span>
<span class="Apple-style-span" style="-webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469); -webkit-tap-highlight-color: rgba(26, 26, 26, 0.296875);">It is commonly believed that to generate a QBO, GCMs require the right choice of: resolution (spatial and temporal), parameterisation (convection and GWs) and numerics (diffusion, numerical solvers). The choice of parameters is not completely unique: getting a QBO in one model, with one set of parameters, may not necessarily result in a QBO in another model. Having said this, one might suspect particular parameter choices being more likely to result in a QBO than others. We propose to explore these parameter settings, across a range of GCMs, to better identify robust effects.</span><br />
<br />
We propose two levels of participation within QBOi. The first, QBOi-lite, assumes one or more sets of model runs with no changes in model formulation (but may include initial condition ensembles). The intention for these runs would be to compare <i>across</i> models i.e. an intermodel comparison. Although such an analysis is not without its problems, it is nothing different from other studies comparing different models e.g. CMIP5. A second level of participation, and more in line with the spirit of the project, is for separate runs using one model with structural changes to resolution, parameterisation etc. Differences would first be sought <i>within </i>a model, before then being checked across models for robustness.<br />
<br />
It is suggested that runs should be AMIP styled (atmosphere only) and run over the recent past (1960 onwards). More specifically, it is suggested that boundary/ancillary fields used for CMIP5 should be employed. As many participating groups would have been involved in CMIP5, this would seem a natural choice.<br />
<br />
The diagnostics which we suggest include those terms required to close the momentum budget, so include 4-daily instantaneous: u, v, Z, GW flux/tendencies. Presumably, there is flexibility for instantaneous or time-average output, but perhaps the former would be better(?). For completeness, temperature/heating terms (T, Q_sw, Q_lw) would be advantageous, but perhaps monthly mean output would be suitable. Obviously, the high frequency diagnostics would be used to derived terms in the TEM equations (e.g. EP flux) which your model may already log. However, it is recognised that model diagnostics should be <b>openly discussed</b> within the wider group.<br />
<br />
But what do you think? Should experiments be more prescriptive? Should specific resolutions, parameterisations be suggested? What is the right balance of diagnostics which should be included? A number of these questions also require a discussion of the science people wish to do. If you think this is important do say so, otherwise science topics will be deferred to a separate discussion blog. Please feel free to contribute to this discussion, your thoughts are most welcome.<br />
<br />
<span style="color: yellow;"><b>Update 22 March 2015 </b>- Following the discussion coming out from the first QBOi Workshop held in Victoria, BC 16-18 March 2015, a number of experiments were endorsed. The details of these will be discussed in separate blogs found on this website.</span><br />
<br />
<br />Anonymoushttp://www.blogger.com/profile/03941743933450723234noreply@blogger.com1tag:blogger.com,1999:blog-3082833814965930105.post-83613868416658001652013-11-07T12:50:00.001+00:002013-11-20T23:03:35.564+00:00QuestionnaireWe are interested in assessing tropical stratosphere variability in past and present day global climate models. Not only are we interested in better understanding the phenomenology of a modelled QBO, but we are also interested in knowing why most GCMs can not readily reproduce it. The <a href="http://users.ox.ac.uk/~astr0092/Questionnaire.html" target="_blank">QBOi questionnaire</a> is designed to identify and collate the phenomenological characteristics of QBO variability from GCMs. The survey makes no attempt to be exhaustive, but instead attempts to balance capturing as much useful information as possible, with a minimum of user calculation, to better ensure user participation.<br />
<div>
<br /></div>
<div>
The questions are (mostly) designed to objectively identify the observed characteristics of a modelled QBO, so that comparisons can be made with observations/reanalyses. However we may have missed out other interesting and verifiable diagnostics which would be of interest to a wider group. What questions would you have liked to have been asked? Do you think the current questions capture most of the salient features of the QBO?<br />
<br />
Lastly, we can also arrange for your data to be uploaded to the QBOi project work-space where we can analyse the data for you. Please contact us if this is an option for you.</div>
<div>
<br /></div>
<div>
Please let us know your thoughts?<br />
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Anonymoushttp://www.blogger.com/profile/03941743933450723234noreply@blogger.com0tag:blogger.com,1999:blog-3082833814965930105.post-5853377379389163652013-11-07T12:48:00.001+00:002013-11-19T22:37:28.181+00:00WebsitePlease let us know how we can improve the <a href="http://users.ox.ac.uk/~astr0092/QBOi.html" target="_blank">QBOi</a> website. <span class="Apple-style-span" style="-webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469); -webkit-tap-highlight-color: rgba(26, 26, 26, 0.292969);">What additional content and information should be added? What are other interesting QBO websites?</span><br />
<span class="Apple-style-span" style="-webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469); -webkit-tap-highlight-color: rgba(26, 26, 26, 0.292969);"><br /></span>
<span class="Apple-style-span" style="-webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469); -webkit-tap-highlight-color: rgba(26, 26, 26, 0.292969);">There are known issues with the display of some pages on mobile devices.</span>Anonymoushttp://www.blogger.com/profile/03941743933450723234noreply@blogger.com0