Category Archives: News

JGR article on the lack of stratospheric dynamical variability in CMIP5 models

In their online first JGR article from 25 March 2013, SPARC DynVar scientist Andrew Charlton-Perez and co-authors describe the main differences in simulations of stratospheric climate and variability by models within the fifth Coupled Model Intercomparison Project (CMIP5) that have a model top above the stratopause and relatively fine stratospheric vertical resolution (high-top), and those that have a model top below the stratopause (low-top).

Although the simulation of mean stratospheric climate by the two model ensembles is similar, the low-top model ensemble has very weak stratospheric variability on daily and interannual time scales. The frequency of major sudden stratospheric warming events is strongly underestimated by the low-top models with less than half the frequency of events observed in the reanalysis data and high-top models. The lack of stratospheric variability in the low-top models affects their stratosphere-troposphere coupling, resulting in short-lived anomalies in the Northern Annular Mode, which do not produce long-lasting tropospheric impacts, as seen in observations. The lack of stratospheric variability, however, does not appear to have any impact on the ability of the low-top models to reproduce past stratospheric temperature trends. The authors find little improvement in the simulation of decadal variability for the high-top models compared to the low-top, which is likely related to the fact that neither ensemble produces a realistic dynamical response to volcanic eruptions.

View source article.

JoC article on a comparison between gravity wave momentum fluxes in observations and climate models

In their Journal of Climate article, SPARC Data Centre scientist Marv Geller and co-authors conduct for the first time, a formal comparison between gravity wave momentum fluxes in models and those derived from observations.

Abstract. Although gravity waves occur over a wide range of spatial and temporal scales, the authors concentrate in this paper on scales that are being parameterized in present climate models, sub-1,000 km scales. Only observational methods that permit derivation of gravity wave momentum fluxes over large geographical areas are discussed, and these are from satellite temperature measurements, constant-density long-duration balloons, and high vertical-resolution radiosonde data. The models discussed include two high-resolution models in which gravity waves are explicitly modeled, Kanto and CAM5, and three climate models containing gravity wave parameterizations, MAECHAM5, HadGEM3, and GISS. Measurements generally show similar flux magnitudes as in models, except that the fluxes derived from satellite measurements fall off more rapidly with height. This is likely due to limitations on the observable range of wavelengths, although other factors may contribute. When one accounts for this more rapid fall-off, the geographical distribution of the fluxes from observations and models compare reasonably well, except for certain features that depend on the specification of the non-orographic gravity wave source functions in the climate models. For instance, both the observed fluxes and those in the high-resolution models are very small at summer high latitudes, but this is not the case for some of the climate models. This comparison between gravity wave fluxes from climate models, high-resolution models, and fluxes derived from observations indicates that such efforts offer a promising path toward improving specifications of gravity wave sources in climate models.

Find source article.

Reminder: registration deadline for S-RIP Planning Meeting on 20 February

(revised) First Announcement of the S-RIP Planning Meeting April 29 – May 1, 2013 Met Office, Exeter, UK http://wwwoa.ees.hokudai.ac.jp/~fuji/s-rip/meeting2013/

Information provided by Masatomo Fujiwara, David Jackson, and S-RIP Working Group:

Dear colleagues,

It is our pleasure to invite you to participate in the SPARC Reanalysis/analysis Intercomparison Project (S-RIP) Planning Meeting in Exeter, UK during April 29-May 1, 2013.

A temporary website for the S-RIP is found at: http://wwwoa.ees.hokudai.ac.jp/~fuji/s-rip/
The meeting webpage is found at: http://wwwoa.ees.hokudai.ac.jp/~fuji/s-rip/meeting2013/

Scientific objective and scope of the meeting:

The first S-RIP Planning Meeting shall be held at the Met Office in Exeter (UK) on April 29 to May 1, 2013. The aim of the S-RIP is to create a review report on the reanalysis intercomparison within the next 4-5 years as one of the SPARC report series. Thus the goal of the Planning Meeting is for S-RIP Working Group members, representatives from the reanalysis centres, and key SPARC researchers to discuss key processes and diagnostics for the reanalysis intercomparison that are relevant for SPARC-related middle atmosphere science. Furthermore, the chapter titles and leads will be determined at the Planning Meeting.

Specific aims of the meeting:

  • To finalize the report outline/chapters including chapter lead names and initial list of contributors. (The Working Group has prepared a draft structure of the final S-RIP report. At the meeting, each chapter will be given a 1 hour time slot, and the diagnostics list and observational data for validation are presented by the chapter co-leads and discussed by the participants.)
  • To define the general guidelines and protocols, and the specific diagnostics used in each chapter.
  • To define the timetable of the project.


Important Additional Information:

Oral presentations are by invitation only. In addition, we welcome contributed poster presentations. The structure of the meeting is such that all participants are expected to assist the S-RIP Working Group in agreeing the structure of the report to result from the project, and in volunteering to lead (or to make major contributions to) the writing of the report. The meeting is open to all, but since space is limited all participants must register. To do this, please send the following information to
1: Name
2: Email address
3: Affiliation
4: Title
and short abstract (if you are submitting a poster)) by *** 20 February 2013 ***.

Information on travelling to the Met Office is found at the meeting webpage. In addition, a block booking of hotel accommodation in Exeter may be made. Further information on this will be available soon.