 Hello and welcome to tutorial 8. So, here we shall cover details about Doppler weather radar data abbreviated as DWR and also try to see how DWR based precipitation estimation is made possible. Now to start with let me give you little details about what DWR is. So, as seen in the screen in front of you DWR is an active microwave sensor which is used for monitoring the occurrence and movement of rainfall patterns. So, DWRs can be mounted on the ground, it can be mounted on trucks or on towers and it provides valuable information about the timing, the probability, the location, type and intensity of rainfall. So, let me reiterate it provides you the timing, the probability, the location, the type and intensity of rainfall whether it is heavy rainfall or whether it is low intensity rainfall and so on and it is largely being used by weather forecasters and general public. So, DWR data also gives us information about occurring thunderstorms and cyclones because they operate in the microwave region of the electromagnetic spectrum and hence included as part of this tutorial. Now these microwave radiations from DWRs give us the three-dimensional profile of clouds and they give us the ability to see through clouds and hence measure the severity and intensity of rainfall. So, this tutorial is designed to focus on visualizing and understanding the data from DWR instrument. So, shown here towards your right side you can see the abbreviation for radar that is radio detection and ranging wherein you have a microwave transmitter, a pulse transmitted from the transmitter travels to the target, hits it, comes back and the hit pulse here is getting reflected from the target and it travels back to the antenna where it is getting detected and the travel time between transmission of a pulse and when the reflected signal reaches the receiver back that is measured by the radar and this is used to give us something known as a range that is a distance. So, to reiterate the DWR as you see it generates a strong microwave signal and it transmits the signal in one direction with the use of antenna. Now this transmitted signal is going to interact with the medium that is the atmosphere in this case and it is going to hit the target which may be clouds, it can be birds and those targets are going to influence the amount of reflected energy that is going to come back. So, this reflected signal from the target as received by the radar contains information about the amplitude and phase of the target. So, throughout this tutorial for us we are going to consider clouds as the target because DWR is being used for measuring information about rainfall and thunderstorms and cyclones. Moving on, let me try to show you how a Doppler weather radar looks like. So, this is the representation of DWR data. On the x-axis you have easting from radar, y-axis is northing from radar and as you can see on the left side the reflectivity image is plotted at a particular elevation. So, the radar typically sends out beams in 360 directions and that is being captured in the spherical coordinate system. So, not in the Cartesian coordinate system but in the spherical coordinate system and what you see is two of the variables that we get from DWR data. On the left side is reflectivity, I am going to give you a new terminology reflectivity and on the right side what you see is the velocity image. I have not specified the station here to make it more generic and the legend you can see the colors are representing the reflectivity as well as the velocity. Now, from the amplitude received power can be calculated and using the received power reflectivity factor is derived through the radar equation. Now, more details about radar equation how it is derived and what is the physical significance of reflectivity they have been covered as part of lectures but just to reiterate from the amplitude we get the received power and using the strength of this received power reflectivity factor is calculated through the radar equation. Similarly, we can measure the phase difference between subsequent signals which gives information about the velocity at which target is moving towards or away from the radar and you may have seen similar plots in movies you know when the target can be a submarine or it can be an aircraft and you can see it moving towards or away from a radar and the measured velocity of a target is usually known as radial velocity. So, I am giving you two terminologies one is reflectivity another is radial velocity. So, here as part of this tutorial we are going to see how the reflectivity image from a Doppler whether radar is going to look like and how the radial velocity plots from DWR is going to look like. Again in real time the reflectivity and radial velocity products they are going to be made available to us in polar coordinate system and here always the range denoted typically in textbooks by capital letter R range it represents the distance of the target from the radar. Now what we will try to do is we will try to understand how the data looks like using WCT which stands for Weather and Climate Toolkit. Now this is made available to us by NOAA. NOAA stands for National Oceanic and Atmospheric Administration. This is an American Scientific Agency within the United States Department of Commerce which enables daily weather forecast not only that it gives us information about severe storm warnings and climate monitoring fisheries management to name a few. So, they keep the public informed of the changing environment and NOAA Weather and Climate Toolkit that is WCT the interface is going to look something like this. So, this is an independent software that is distributed from NOAA's National Centers for Environmental Information. It is typically abbreviated as NCEI National Centers for Environmental Information and this is used to visualize the Doppler weather radar products let it be reflectivity and radial velocity. And during severe weather conditions say heavy rainfall conditions both the reflectivity plots as well as the radial velocity plots they help us to identify give us more information about the structure of precipitation as well as the movement motion of precipitation. And this inbuilt tool that is WCT tool it supports data conversion into a variety of formats you know it can be KMZ or Geotape for net CDF and so on. So, moving on let us see where to access WCT from. So, we directly go to the ncdc.noaa.gov website from where you can access WCT. So, this comes in the form of a portable zip file and you can download the version corresponding to you. So, I am going to download the version corresponding to Windows but you have a similar version available for those who are using Unix or Mac. Moving on. So, once we click on the download or launch button typically a new page will appear in which as I mentioned earlier I click the Windows version. Now, if I click on the .exe file the installation happens automatically it will open the WCT visualization interface for us. It is just a matter of few seconds and this is how the interface looks like. You find the data selector option wherein find data, big data, URL directory, single file all these options are made available for you. So, in this tutorial what we will do is we will try to visualize the NexRAD data archive. NexRAD data archive. Now, NCEI's radar archive includes the NexRAD which is an abbreviation for next generation weather radar system. Now, it is a system of 160 high resolution Doppler weather radars that operate in the S band of the microwave region. So, S band DWRs. Now, shown here in dots are the locations of these radars and they are jointly operated by the National Weather Service that is NWS, the Federal Aviation Administration FAA and the United States Air Force. And NexRAD it helps us detect precipitation as well as wind information and NCEI it provides us free access to NexRAD level 2 as well as level 3 products. So, there are two ways in which you can go to the site and import the radar data into the WCT package. Here as I mentioned before we are specifically mentioning about the NexRAD data. So, the two ways in which you can import the data is either from your local hard disk, you can download the data and keep it in one of the drives and then access it using WCT or you can access it remotely that is by remote access. So, to access the NexRAD data archive this link has to be clicked and you will be able to see the map of DWR locations when you click on data access. Now, several informations are made available for us to zoom and then read. So, I am going to specifically the radar products wherein more information is given about the NexRAD data. So, typically when I click on NexRAD I will be able to see the map and the location at which the data is being made available. So, I am going to go to NexRAD inventory. So, there are different ways in which I can select data, I can either select by map or by country or I can access the historical data. So, in this case just for the sake of representation purpose let us try to take an example of Miami radar in Florida which is seen here. The different levels of data are being made available. So, for example, let us try to look at the date of occurrence of Hurricane Katrina that is 26th August 2005 it occurred over Miami city. So, I am going to try to visualize how the radar data looks like. I am going to select level 2 base data and click on create graph. So, make sure that the page appears wherein precipitation mode lines are present in the graph. Now, if precipitation mode lines as what you see in red if this is not present in the graph I would urge you to please select a different date. So, here details are present I directly click on download button to download the data. So, you can see it is given as dot gz files. So, typically you have to select a suitable time step for the download to happen and if you observe closely the data will be having its own typical nomenclature wherein you know underscore in the file name represents the time step. So, here 002320 it represents 00 hours 23 minutes 20 seconds in UTC time zone. So, what we do is we try to download the file and then we try to unzip the compressed file. Again let me reiterate before starting the process make it a point to select a major weather event that has occurred over a particular state in USA and in this tutorial the example shown is for Hurricane Katrina that occurred over Florida state on 26th August and again this is for 2005 for demonstration purposes. So, what we did is we downloaded the data now let us try to import it to WCT and see how the data looks like. So, what we are going to do is you can see a button known as NOAA big data. You can click on that and then again there is an option for you to select the data and the time zone time period. You get to select a suitable station from the drop down window. So, if I click on that it is going to drop down and I get to select a suitable station from this list and once I choose the appropriate date from this window here what we can do is we can try to click on list files which will show us a list of available data. The next step is you know once you have imported the data into WCT you click on the load button it starts displaying the image with a background boundary map and shown here is the image specific to radial velocity which has been captured in different elevations. So, if I click on 4.51 it means the image shown here is of that particular elevation. So, additional options are also present which one can explore based on your interest. So, to re-itrate let me try to show you what we do is we open the WCT interface and I click on NOAA big data next read level 2 and then I click on the drop down option which helps me select the locations again. And then I also get to specify the time I have just clicked an example. So, previously what we did was we understood how to download the data save it in a hard disk maybe we can use it while dealing with Python and in this particular video you can see that I am trying to access the data remotely. When I click on list files a series of files of level 2 next read dual polarization radar data the files open up and I can click on any of these options and then it automatically loads itself. Say I want to create an animation of the files back to back I can use WCT to create a neat animation. So, the plot you see here is the reflectivity plot Z reflectivity plots and at different elevations. So, the plot you see is of 0.46 elevation similarly I can click on each of these elevation values and load so that I get the reflectivity and please make a note of the legend which is DBZ. Similarly, I can get plots that give you information about radial velocity I can have spectrum width. So, these are different variables that are found in a Doppler weather radar data what it means and how to interpret that is covered shortly. So, right now we are just interested to visualize the data. Just to give you an example of the different variables that are present in a file. Okay, moving forward. So, till now we were trying to visualize next rat data but then we also want to know how to get access to the Indian Doppler weather radar data. For that you can visit the MOSDAC website that is Meteorological and Oceanographic Satellite Data Archival Center that is what MOSDAC stands for space application center of ISRO provides the 3D volumetric level 3 Doppler weather radar data in the MOSDAC website. So, for downloading we need to create a user ID password and then go to the MOSDAC portal the link will open up an FTP as what you see towards your right side wherein the level 3 data will be listed. So, what I have done is I have tried to list the weather events occurring over Trivandrum radar in Kerala and its surrounding regions. So, I can easily go to a suitable month to download the .tar.gz file as shown I have just highlighted one file for representation and once we untar the downloaded files it will contain a set of netcdf.nc files and these netcdf files will contain information specifically I am going to highlight the two variables which were introduced as part of this tutorial that is reflectivity and radial velocity and you may like to note the nomenclature of the file which gives you when the data has been captured the particular time step is assigned to the name of each file. So, till now we have downloaded data from Nexrad we have seen the process how to download data from MOSDAC site we have installed the WCT package and we have also seen how to visualize the Nexrad data in WCT. So, now what we will do is let us try to work with Doppler weather radar data using Python. So, here let me introduce you to PyArt. Remember in one of the previous tutorials I was mentioning that in Python whenever you need certain libraries specific to your function you need to download install it in the command prompt before importing the same in Python in Jupyter notebook. So, PyArt stands for Python ARM radar toolkit and it contains a collection of weather radar algorithms that help you analyze data, visualize data and also it is capable to handle many types of weather radars. So, what I have done is I have just introduced the manuscript which has come out in journal of open research software that has been put out by the developers themselves. So, in case you are interested to know more about PyArt I will urge you to read get more information from this paper. So, as before we need to install PyArt library for our exercise. So, I am going to go to command prompt of Anaconda and then type the commands conda install c conda forge ARM PyArt. So, typically when we are working with different tutorials that require different libraries and different functions it will be beneficial if you create a separate environment and then install the libraries that are relevant for your exercise. So, that there is no clash. And the PyArt as I mentioned earlier it is a module for visualizing radar data particularly which has been designed for next rat data. Now PyArt has some dependencies as in PyArt works when a few related libraries are also installed prior in Python. And for PyArt the dependencies are numpy, scipy, matplotlib and netcdf4. Let me repeat PyArt dependencies are numpy, scipy. We have already seen what they are as part of previous tutorials. So, by now I am assuming that you are comfortable with these names. So, I am going to install the dependencies one by one. First is matplotlib as before it hardly takes a few seconds and then scipy and numpy and netcdf4 because basically the Doppler with the radar data is going to be in dot NC format that is netcdf format and we need netcdf4 library as well. And every time I am going to use conda install followed by the library name whatever I want to install. And remember I am going to do this in the command prompt. So, now I have completed matplotlib and netcdf4. If it is already installed the message comes up saying all the packages are already installed. But if in your system you are doing it for the first time it is going to ask you whether you want to install the packages or not. So, in this case a few of the packages are already installed in my system and hence the message. So, I wait for all the libraries to be installed and then I am going to open the Jupiter notebook to start with the exercise. So, till now we understood how to access the Doppler with the radar data and then now we are trying to visualize, analyze the Doppler with the radar data from Nexrad and from Indian Doppler with the radars in python environment. And for that the first step was we installed the libraries that are relevant. And then after installing all the libraries and the dependencies I am trying to open the Jupiter notebook. So, let me hope that you found this section of the tutorial useful and as part of the next section we will understand more about the specific extraction of variables that are required to estimate precipitation from Doppler with the radar data. Thank you.