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Ayako Yamamoto’s PhD Proposal

Ayako will be presenting her PhD proposal today, Friday April 25, at 10am in room 934 on “the relative importance of the atmosphere and the ocean in controlling Western European climate variability and their couplings”. All are invited to attend.

In the News: Global warming felt to deepest reaches of ocean

Our very own Jaime Palter and Casimir de Lavergne are making waves with a new article titled Cessation of deep convection in the open Southern Ocean under anthropogenic climate change.

Read more about it in the McGill NewsRoom.

Seminar: Madalina Surcel and Dominik Jacques

Madalina Surcel and Dominik Jacques have combined efforts to bring you a
special student seminar tomorrow at 14:35. Please join us for cookies and coffee before at
2:15 preceding the talk.

Abstract

For our student seminar, we have prepared something special. When
discussing our respective talks, we realized that we were touching many
similar concepts from different points of view. Instead of working out a
bridge between our presentation, we have interlaced them in order to
make a story. We think this will make it easier (and more interesting)
to understand the concepts presented. For us, it make a nice change from
the more formal conference presentations that we are accustomed to.

In the same spirit, here is our common abstract,

*Mesoscale prediction of precipitation: current status and future work*

It is widely accepted that whereas the performance of Numerical Weather
Prediction (NWP) models is continuously improving, precipitation still
remains very difficult to forecast and quantitative precipitation
forecasting (QPF) skill is generally low. This talk discusses the
ability of current generation mesoscale models (with dx~1km) to forecast
rainfall. Emphasis is put on the main factors affecting forecast quality
and on the methods that could improve QPF.

Through the evaluation of high-resolution ensemble
precipitation forecasts it is shown that models have generally very
little skill in forecasting rainfall at scales lower than 100km.
Furthermore, while ensemble methods can increase predictability at
scales larger than 100km, for small scales, the spread is too large to
provide useful forecasts.

At storm scales, assimilation of radar observations has the potential to
improve model predictions. So far, demonstrating the improvements
brought by assimilation has proven very challenging as forecasts show
great sensitivity to small errors in initial conditions. This is
especially true for humidity, which is not corrected significantly
through assimilation. As a solution to this problem, an alternative
method for the assimilation of radar observations based on a combination
of variational techniques and statistical analysis of model output is
discussed here.

Another pathway for the improvement of forecasts is through the use of
more accurate model physics. However, sensitivity tests show that
despite large dependence of results on various model parameters at small
scales, no single parameter explains the largest forecast errors.

The work presented here seems to indicate the existence of
a critical spatial scale situated around 100km. Above this scale,
forecasting results are satisfactory, while below it QPF skill is poor.
The effect of radar data assimilation is limited to scales smaller than
the critical scale such that improvements due to assimilation are
expected to be short-lived.

New Software: HDFView

HDFView is now available ! To use HDFView, please issue ‘hdfview’ on all 64-bit computers in our department.

HDFView Screenshot

HDFView is a visual tool for browsing and editing HDF4 and HDF5 files. Using HDFView, you can:

  • >view a file hierarchy in a tree structure
  • create new file, add or delete groups and datasets
  • view and modify the content of a dataset
  • add, delete and modify attributes
  • replace I/O and GUI components such as table view, image view and metadata view

Seminar: Dr. Robert Rabin

Dr. Robert Rabin of NOAA’s National Severe Storm Laboratory NSSL in Oklahoma will be joining us Thursday, January 10, 2013 at 3:30 p.m. in Burnside Hall, room 934 to discuss “Research activities at the NOAA National Severe Storms Laboratory: Ideas for collaboration”

Abstract

A brief history of National Severe Storms Laboratory and the evolution of research activities there. The use of Doppler radar and GOES satellite data as an observation tool for detecting thunderstorm initiation and precipitation systems, land-use interaction with the boundary layer, monitoring surface wetness and wildfires, and challenges in numerical weather forecasting will be discussed. Ideas for collaboration with projects will be explored.

Happy Holidays from AOS

With every new year it is often rewarding to look back at the past one and note all of the achievements and changes that were made.  The department of Atmospheric and Oceanic Sciences did just that and producred a holiday newsletter looking back at the past year. Please have a look!

We wish you and your family happy holidays!

Wiki has a new look

The AOS departmental wiki has a new look!

The new AOS Wiki Theme

The new AOS Wiki Theme

Remember, you can login with your AOS account to make any changes you feel may be beneficial to the department. If you have any questions or concerns, please contact support@meteo.mcgill.ca.

IDL is Available

IDL Logo

Courtesy of Exelis Visualization

10 license for IDL 8.2 are now available departmentally. Special thanks the following individuals for their contributions:

To use idl, you must be logged into a departmental 64-bit Linux system. Once logged in, you may issue:

idl to start IDL in the terminal

idlde to start IDL graphically

If you experience any difficulties, please contact support@meteo.mcgill.ca

Seminar: Joowan Kim

Please join us tomorrow, Wednesday at 14:35 in Burnside 934 for a student seminar by Joowan Kim. Abstract is as follows:

 

Climatology of ERA-Interim and ensemble of CMIP5 models.

Annual-mean climatology (1979-2005) of 100-hPa temperature from a) ERA-Interim and b) ensemble of CMIP5 models. White contours denote OLR from observation and model ensemble respectively. c) Taylor diagram of the temperature field within 15S-15N for individual models (open and closed circles) and their ensemble (cross).

Thermal characteristics of the tropical tropopause layer in CMIP5 models: historical simulations

The climatology and variability of temperatures in the tropical tropopause layer are investigated in 16 Coupled Model Intercomparison Project Phase 5 (CMIP5) models for historical simulations. The climatology of 100-hPa temperatures compare well with ERA-Interim reanalysis. The models possess reasonable temperature minima in the deep tropics, but some models also have a warm bias or a bias in the location of the temperature minima. The CMIP5 models generally capture the phase of the seasonal cycle in 100-hPa temperatures, but the amplitude of the seasonal cycle varies greatly among models. The interannual variability in 100-hPa temperature is associated with the El Niño-Southern Oscillation (ENSO) and volcanic forcing in observation and CMIP5 models. Most of models successfully capture the ENSO-related large scale response, but the response to volcanic forcing is overestimated in many models. On intraseasonal timescales, observed and modeled variability is dominated by equatorial waves (Kelvin, inertio-gravity, and mixed Rossby-gravity waves) and the Madden-Julian Oscillation (MJO). Most models show variability related to the equatorial waves, but significant biases are found in the phase speeds of the waves when compared to ERA-Interim. The MJO signature is weak and non-distinguishable from the Kelvin wave power in most CMIP5 models.

Student Seminar: Amélie Bouchat

Energy dissipation in viscous-plastic sea ice models

Energy dissipation in viscous-plastic sea ice models

Energy dissipation in viscous-plastic sea ice models by Amélie Bouchat

Most current sea ice models are based on the viscous approximation introduced by Hibler (1979). These viscous-plastic (VP) models approximate the small elastic deformations by the viscous deformations of a creeping flow. The resulting numerical treatment is much more simple than in earlier sea ice models, but viscous deformations introduce a non-physical energy sink in the model since they are not reversible as the elastic deformations. The project is aimed at assessing the consequences, physically speaking, of this non-physical energy dissipation in the models and therefore verifying the validity of the VP approximation. The dissipation is studied using the kinetic energy balance that is derived using the continuity and momentum equations for sea ice. This analysis allows us to evaluate the different terms of the balance and look at the relative importance of the viscous dissipation. The results will be presented for a 40km-resolution run of 1 year. The dependence of the viscous dissipation on the number of Newton loops of the numerical solver of the momentum equation is also studied. Preliminary results at 20km-resolution will also be shown.

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