18 February 2008

"Climate type" analysis of DEMETER seasonal forecats

Here are few figures concerning the different DEMETER coupled models ability to capture observed features of seasonal forecasts over West Africa:

Fig1: Mean seasonal rainfall (JJAS 1980-2001) as simulated by the different coupled models used in DEMETER forecasts, compared to CMAP observations.

Fig2: Mean seasonal rainfall (JJAS 1980-2001) anomalies as simulated by the different coupled models used in DEMETER forecasts with respect to CMAP observations.

Fig3: Seasonal rainfall (JJAS 1980-2001) standard deviation as simulated by the different coupled models used in DEMETER forecasts, compared to CMAP observations.

Fig4: Seasonal rainfall (JJAS 1980-2001) standard deviation anomalies as simulated by the different coupled models used in DEMETER forecasts, with respect to CMAP observations.

Fig5: Seasonal rainfall (JJAS 1980-2001) spatial correlations between the different coupled models used in DEMETER forecasts, and CMAP observations.

Fig6: Seasonal rainfall (JJAS 1980-2001) potential predictability as simulated by the different coupled models used in DEMETER forecasts.

Sahelian rainfall index (JJAS 1980-2001, 16W-40E, 10N-20N) as simulated by the different coupled models used in DEMETER forecasts compared to CMAP observations (CMAP black line, Ensemble mean red line).

07 February 2008

Easily convert grib files to ncdf

NCL has been successfully installed on the server of the geography Dpt
This soft is able to read both grib and ncdf files

Included a usefull tool to convert grib files to ncdf.
Assuming a file called test.grb
Just try on a linux terminal:

ncl_convert2nc test.grb

It will create a file called test.nc

You can then see the file header by typing:
ncdump -h test.nc

More details:

Tools to modify ncdf files

Nco software:

Nco is a usefull tool to modify and to do operations onto netCDF files, using linux/unix command lines. It has been installed on the geography server at the university of Liverpool

Here is just a copy of the nco web site including examples:

What is NCO?

The netCDF Operators, or NCO, are a suite of programs known as operators. Each operator is a standalone, command line program which is executed at the UNIX shell-level like, e.g., ls or mkdir. The operators take netCDF files as input, then perform a set of operations (e.g., deriving new data, averaging, hyperslabbing, or metadata manipulation) and produce a netCDF file as output. The operators are primarily designed to aid manipulation and analysis of gridded scientific data. The single command style of NCO allows users to manipulate and analyze files interactively and with simple scripts, avoiding the overhead (and some of the power) of a higher level programming environment. The NCO User's Guide illustrates their use with examples from the field of climate modeling and analysis. Note that the “averagers” are misnamed because they perform many non-linear operations as well, e.g., total, minimum, maximum, RMS:

The operators are as general as netCDF itself: there are no restrictions on the contents of the netCDF file(s) used as input. NCO's internal routines are completely dynamic and impose no limit on the number or sizes of dimensions, variables, and files. NCO is designed to be used both interactively and with large batch jobs. The default operator behavior is often sufficient for everyday needs, and there are numerous command line (i.e., run-time) options, for special cases. NCO works well on all modern operating systems, including: Apple OS X, *BSD, Cray UNICOS, DEC Tru64, IBM AIX, HPUX, Linux, Microsoft Windows, NEC Super UX, SGI IRIX, and Sun Solaris.

06 February 2008


Here are few personal examples of the IDV software
get the quicktime soft to see the videos:

1) Seasonal cycle of the West african monsoon:

Mean seasonal cycle (1950-1999) of mean sea level pressure (shading at the surface) mean 925hPa winds (vectors in white). Tropical easterly jet (U wind at 200hPa, gray contours) African Easterly jet (U wind at 600 hPa, white contours), the vertical section is the temperature.....

You can note the establisment of the monsoon flow during boreal summer, the northward migration of the thermal low following the sun run (see the vertical profile), and the northward migration of the jets, and their westward extension.....

2) Seasonal cycle of the Inter tropical convergence zone (ITCZ), overlayed onto the orography

You can note the influence of the mountains upon rainfall (Cameroon mounts, Fouta djalon, Ethiopian highs). The impact of the Himalaya during the establishment of the Indian monsoon can be noted too......

Usefull tools for climate analysis and teaching

Here are listed few usefull softs concerning climate science

edGCM : simple Global Climate model (an older version of the NASA model) for education and training, it allows to setup climate simulation (scenario, paleoclimate sim....), to visualize the outputs (Eva interface) and to write papers
Really usefull for students......
Can be installed under windows.....

IDV: 3D real time visualization soft. Really usefull to impress people during the conferences....
Can acces real time forcecast of the GISS model via the web (a catalog can be accessed to by URL)
Read both grib and netcdf files......

Share your pc for climate simulations.....

NCAR portal, allowing to analyze datas, perform statistic analyses and lots of things.....
really easy to use (just push buttons....)

NCL: Ncar language, son of ncargraphix
really usefull to perform analysis and to do nice plots for papers: