Reason : Why Climatology beings from 1979 onwards

Reasons behind climatology beings from 1979 onwards,

Most of the global region observation relying on satellite measurements data.

1) Satellite measurements of ice areas began in 1979

Notz Dirk, Marotzke Jochem, 2012, Observations reveal external driver
for Arctic sea-ice retreat, Geophysical Research Letters, VOL. 39, L08502, doi:10.1029/2012GL051094 Link

The above paper says,

2) The pre-1953 data is pretty useless, much of it is obviously not

changing from year to year. The variation in the Hadley Centre’s Sea Ice and Sea Surface (HadISST) Temperature dataset changes pretty radically at 1979 onwards.

3) From 1979 onwards the HadISST data set is primarily based on

satellite observations. We find across the 1978/1979 boundary an
unusually large increase in sea-ice extent in March and an unusually
large decrease in sea-ice extent in September.

Source :

In above link you can see the plots which shows observation variability rapid cut-off at 1979 onwards.

4) P. Nabat et al., 2013, A 4-D climatology (1979–2009) of the monthly tropospheric aerosol optical depth distribution over the Mediterranean region from a comparative evaluation and blending of remote sensing and model products, Atmos. Meas. Tech., 6, 1287-1314, doi:10.5194/amt-6-1287-2013 Link

The above paper says,

They extend the 2003–2009 reconstruction to the past up to 1979 using the 2003–2009 average and applying the decreasing trend in sulfate aerosols from LMDz-OR-INCA. Finally optical properties of the different aerosol types in this region are proposed from Mie calculations so that this reconstruction can be included in regional climate models for aerosol radiative forcing and aerosol-climate studies.

i.e. Upto 1979 observed / satellite data are reconstructed using after 1979th year observed dataset.


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How to insatll clim.pact inside R path in Ubuntu

Dear All,

To install clim.pact packages inside our R path follow the below steps.

Step 0 : Install R
Download latest R source tar ball from and extract it.

Then go inside to that directory and run the following three commands as root or sudo user.

$ ./configure
$ make
$ sudo make install

Step 1 : Install Dependencies

We need "ncdf" & "akima" additional packages to be installed inside R.

To install ncdf correctly we need to install the following packages in our machine.

In Ubuntu follow the below step.

$ apt-get install libnetcdf-dev udunits-bin libudunits2-dev

Then type R command in terminal

$ R
> install.packages(‘akima’)

> install.packages(‘ncdf’)

Choose any one of the country to select mirror and download, install the corresponding packages inside R.

Step 2 : Install clim.pact package inside R


Download latest ‘clim.pact’ tar ball from

Then go to the downloaded directory in terminal then issue the following command.

$ sudo R CMD INSTALL clim.pact_2.3-10.tar.gz


$ su
# R CMD INSTALL clim.pact_2.3-10.tar.gz

Thats it. We installed clim.pact package successfully inside our R path.

Note : In the file name specify the downloaded version clim.pack_version.tar.gz

Step 3 : Test
Go to R shell command and load ‘clim.pact’ package as follows.

$ R
> library(clim.pact)
Loading required package: ncdf
Loading required package: akima

Enjoy !

Project Associate,
Centre for Atmospheric Sciences,
Indian Institute of Technology Delhi.

Posted in Uncategorized | Tagged , , | 3 Comments

Steps to Access Github Repository Under IIT Proxy


Follow the below steps in your linux machine to create git repository and push to your remote github account repository.

I am pulling/pushing the github commits under IIT Delhi proxy. If you have proxy, then change the proxy address and port no according to yours.

$ su root

step 0: Login as root and enable/set http_proxy and all.

# vim /root/.bashrc

export http_proxy=
export https_proxy=
export ftp_proxy=

add the above lines. Also go to Network proxy settings in your ubuntu and set the system proxy as above.

step 1 :

# git config – -global http.proxy

# git config – -global https.proxy

# cat ~/.gitconfig

Add your laptop ssh public key to your github account
step 2 :

Either follow the above post link or follow the below steps:

# apt-get install xclip corkscrew

# ssh-keygen -t rsa

# xclip -sel clip < ~/.ssh/

# vim ~/.ssh/config

  PreferredAuthentications publickey
  IdentityFile ~/.ssh/id_rsa
  ProxyCommand corkscrew 3128 %h %p
  Port 443

add the above lines to config file. Mention is proxy ip address (instead of proxy host name like  and 3128 is port.

add the copied public rsa key (via xclip) into and set some title.

Then do the following, you will get  “Hi your github user name! You’ve successfully authenticated, but GitHub does not provide shell access.” response. If you get some thing like below, then your settings are working correctly.

# ssh -T

Hi arulalant! You’ve successfully authenticated, but GitHub does not provide shell access.

Now you can move to step 3.


step 3 : Create a repo in github account

I created repo named ‘UV-CDAT-IPython-Notebooks’

step 4 : add files to your local repo then do commit


git clone

# git clone

by the above way, we cloned the github repo into local system.

step 5.0 : pull the changes you made in the file in github account through browser itself.

# cd reponame

# cd UV-CDAT-IPython-Notebooks

step 5.1 : # git pull origin master

pull your changes which you made through browser in github  ‘origin’ repo ‘master’ branch  to local repo.

step 5.2: update global github profile in our local system


git config – -global “”
git config – -global “Your Name”

# git config – -global “”
# git config – -global “arulalant”


step 6.0: make some changed or add new files into local repo. then do # git add filename,    # git commit & finally push local changes into github repo by below command.
step 6.1: # git push origin master

push your changed which you made locally to the remote ‘origin’ [github acc] to ‘master’ branch.

it will ask username of github and passwd. enter username [arulalant] itself, no need to enter as login email id.

If you dont like to enter your username & passwd every time (applicable only if you cloned project repo via https instead of git) then follow the below step.

step 6.2 :

git remote set-url

$ git remote set-url origin

The above command must execute inside the project directory. It will tell github to use your ssh public key instead of asking you to enter your credentials every time.

PS : you can try to set all the above 6 steps into normal user itself instead of root.

Its works fine for me.

Now I can release all my development code as well as fun code. :-)

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Conducted PythonMonth Workshop at Jamia Millia Islamia University, New Delhi

Hi All,

Volunteers from NCR region for PythonMonth conducted the third PythonMonth workshop at Jamia Millia Islamia University, New Delhi on 24.08.2013, it was received well.

A special thanks to Konark, Akif, Anshul, Aniket and all the other student volunteers who helped co-ordinate the whole workshop at the college.

A brief about the workshop :

Instructor : Arulalan.T (myself)
Volunteers for Hands-On session : Satyaakam Goswami, Akif Khan, Anshul, Saurabh Kumar + Lot of helping hands, thank you everybody.

Content of the workshop :, along with project showcase by Satyaakam and Aniket

There were about 50-60 students who were given hands-on session on python.

Google+ Album:

The overall feedback was collected, and reading the survey results seems that workshop has made a positive impact.


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Conducted Python Workshop in IIC, DU, South Campus – Python Month 2013

Greetings to all.,

This August (2013) is the Python Month in India.
I already conducted python workshop in IIT Delhi, to the Centre for Atmospheric Science Students in July itself.

We volunteers from NCR region for PythonMonth conducted the first PythonMonth workshop at IIC(South Campus, Delhi) on 02.08.2013, it was received well.

A brief about the workshop :

Instructor : Mr. Arulalan.T ( Project Associate at Indian Institute of Technology) [myself]
Volunteers for Hands-On session :
Piyush Kumar
Mahesh Salaria
Satyakaam Goswami
Konark Modi

Content of the workshop :

There were about 50 students who were given hands-on session on python.

Flickr stream :

The overall feedback was collected using survey monkey, and reading the survey results seems that workshop has made a positive impact.

I thank the python month teams those who initiated and organized the workshop.

Next python workshop is going to be held in Amity Unitversity, Noida on coming saturday 10.08.2013.


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hdd quota control through webmin – GUI – Linux – Ubuntu

Dear All,

Here I documented about how to control/set the hard disk / home space quota to each users, groups through webmin gui.

You may get so many documents on how to do the same in command line itself.

Here we go !!!

1. Enable quota check on filesystem

First, you should specify which filesystem are allowed for quota check.

Modify the /etc/fstab, and add the keyword usrquota and grpquota to the corresponding filesystem that you would like to monitor.

The following example indicates that both user and group quota check is enabled on /home filesystem

# vim /etc/fstab
UUID=4ea80ca3-37b7-447e-831a-700a38627029 /home ext4 defaults,usrquota,grpquota 1 2 


 /dev/hda1 /home ext4 defaults,usrquota,grpquota 1 2

Reboot the server after the above change. While rebooting it will take some time (only one time) to enable usrquota, grpquota on the /home filesystem. So wait.

2. Initial quota check on Linux filesystem using quotacheck

Once you’ve enabled disk quota check on the filesystem, collect all quota information initially as shown below. For that you may need to install the following packages.

# apt-get install quota quotatool
# quotacheck -avug 
quotacheck: Scanning /dev/sda3 [/home] done 
quotacheck: Checked 5182 directories and 31566 files 
quotacheck: Old file not found. 
quotacheck: Old file not found.

In the above command:

  • a: Check all quota-enabled filesystem
  • v: Verbose mode
  • u: Check for user disk quota
  • g: Check for group disk quota

The above command will create a aquota file for user and group under the filesystem directory as shown below.

# ls /home/ 
# quotaon -avug

3. Install webmin gui to control hdd quota for the users & groups

First install the dependencies as shown below

# apt-get install apt-show-versions

For Ubuntu 12.04 you can download the webmin deb file from the below link

and install as follows

# dpkg -i webmin_1.620_all.deb

Once you installed you can access the webmin in your browser at either https://localhost:10000/ or it will give you hostname as like below.


You can download other os distro binary and source files from the below link.

4. Open webmin gui

now log into webmin & search ‘quota’ you should see a result called “Disk Quotas”

click on it and press enable quotas on /home

now u can create/set hdd quotas like soft, hart limits & grace time for each users, groups…

Soft limit : Actual size that you are allocating to the user/group
Grace time : Some grace period (seconds to days) you are allocating to allow the user to exceed the soft limit (upto grace period) but not hard limit.
Once they exceed the soft limit, then they have to revert back to less than their soft limit size within the allocated grace time period.
Hard limit : Hard limit that you are allocating to the user/group for the max size they can use at any most case. They can not exceed this limit at any time.

5. Notify the used home size & quota status report to the user when they login into the shell/terminal

Finally :-

add the below lines in the

# vim /etc/bash.bashrc

to show the users quota information with their limit & used space whenever they login to the shell/terminal.

echo "Your home directory quota information "
quota -us $USER
echo "Try to keep space < quota. You cant exceed the limit "

Have Fun !

Posted in Documentation, Linux, Ubuntu, Uncategorized, Web | Tagged , , , , , , , | Leave a comment

2012 in review

The stats helper monkeys prepared a 2012 annual report for this blog.

Here’s an excerpt:

4,329 films were submitted to the 2012 Cannes Film Festival. This blog had 18,000 views in 2012. If each view were a film, this blog would power 4 Film Festivals

Click here to see the complete report.

I couldn’t post my thoughts & codes in the past 6 months. :(.

I learned many new subjects in M.Tech Atmospheric Sciences.

Let me post those stuff in following days.

Happy new year to all. :-)



Posted in Arulalan | Leave a comment

2011 in review

The stats helper monkeys prepared a 2011 annual report for this blog.

Here’s an excerpt:

The concert hall at the Syndey Opera House holds 2,700 people. This blog was viewed about 30,000 times in 2011. If it were a concert at Sydney Opera House, it would take about 11 sold-out performances for that many people to see it.

Click here to see the complete report.

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About MetPy (ECMWF)

Dear Friends,

I have read about the MetPy from the ECMWF .

MetPy = Meteorological Python

Few words about ECMWF :

They are using

  • Perl language to created web application to serve the auto generated plots for both intranet & internet (in the above link)
  • Python language to do diagnostics
  • Magics or MetView to do plot
  • Serving around 24,000 images per day

Few words about MetPy :

A high level library called MetPy is being

developed. It currently offers:

  • an abstract definition of meteorological data and fields,
  • GRIB decoding, coding and field computation,
  • Field sorting and indexing,
  • ODB access using its NetCDF file export facility,
  • core score computing (rmse, ancf, stddev, mean), on a weighed grid and limited areas,
  • access to Verify scores (backwards compatibility) ,
  • interface with Magics,
  • interface with PCMS,
  • everything available in open source.

Example Program of MetPy usage :

>>> from MetPy import *

>>> an = FieldSet( ‘an.grib’ )
>>> fc = FieldSet( ‘fc.grib’ )
>>> cl = FieldSet( ‘climatology.grib’ )
>>> bi = FieldSet( ‘biases.grib’ )

>>> scores = Scores( fc-cl+bi,
area = verify_config[ 'europe' ] )

>>> print scores.correlation( )

>>> print scores.rmse( )

Few Application of MetPy :

  • Currently a typical experiment diagnostics is being written on ocean data.
  • compare ocean observation profiles with experiment fields and generate statistics.

MetPy Utilities :

  • The Date class is a primordial building block as computations on dates are always needed particularly in diagnostics & verification.
  • Configuration tools are also important, once your library can read configuration files with sufficient flexibility, you can introduce parametrisation from the begin-ning of any new development.

MetPy Source Link :

Presentation Link :
It contains about ECMWF & little core about MetPy

Conclusion :

  • MetPy Meteo France also installed & running the MetPy.
  • MetPy module has Fields, FieldSet, Ensemble, FieldIndex, Diagnostics.

I couldnt understand few meteorological terms in the MetPy. So I couldnt realize the more power of it.

What I understood from the example is metpy can calculate Scores, correlation, rmse & etc.,

I will post the CDAT Vs MetPy in upcoming posts in my blog.



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