Upper Air Sounding System PDF

62 by 100 m or more from the mean during the second 05 minutes of the period, this shall be indicated. When the variation of the RVR values shows as upward or downward tendency this shall be indicated by...

62 by 100 m or more from the mean during the second 05 minutes of the period, this shall be indicated. When the variation of the RVR values shows as upward or downward tendency this shall be indicated by abbreviation "U" or "D" respectively. In circumstances when actual fluctuations during the 10-minute period indicate no distinct tendency, this shall be reported using the abbreviation "N". When indications of tendency are not available, no abbreviations shall be included (For example RI 2/1 IOOU). UPPER AIR SOUNDING SYSTEM Introduction 70. Directorate of Met, Air HQ (VB) has procured and installed Qty 10 Upper Air Sounding Systems (UASS) at various operational IAF bases. UASS is utilised for observation of upper air meteorological parameters like temperature, humidity, pressure, wind direction and speed at a very fine resolution up to an altitude extending well beyond troposphere. These parameters provide immense inputs to the Met observers, forecasters and aviators. UASS has various IT and communication related components in it and hence needs to be operated and maintained professionally. Working Principle 71. powered telemetry (Greek words tele=remote, and metron = measure) instrument package carried into the atmosphere by a weather balloon of either natural rubber latex or a synthetic latex that measures various atmospheric parameters and transmits them by a radio to ground receiver, operating at HF signal 400-406 MHz. Wind profiles from radiosonde are derived from tracking the displacement of the balloon from launch site as function of time using Global Positioning System (GPS). An Overview & Components of UASS 72. Various components of Upper Air Sounding System are illustrated below: -  63 Fig. 2.13 - Upper Air Sounding System 73. UASS provides the upper wind, temperature, dew point and humidity profiles timing of the day (0000 UTC and 1200 UTC). It is designed to measure the profile of various Met parameters from ground level to an altitude extending well beyond troposphere. Measured data is sent down through high frequency transmission to the receiving station (Ground Station) as the balloon lifts and is carried by the prevailing atmospheric winds. 74. Components of UASS. The primary components of UASS are: - (a) Balloon Filling Unit. This unit is basically an aluminum-coffer which consists of the following parts: - (b) Flexible pressure tube, pressure reducing valve and spark proof wrenches (Fig. 2.14a). (c) Earthing-kit consisting of earthing-rod, earthing cable and plastic hammer (Fig. 2.14b). (d) Pedestal with moveable nozzle and shut-off valve (Fig. 2.14c).  64 (a) Pressure tube & pressure reducing valve (b) Earthing kit (c)Pedestal Fig. 2.14 - Parts of Balloon Filling Unit (b) Antenna. There are three antenna fixed on the mast namely omni directional antenna (ANT.1) helix antenna (ANT.2) (Fig 3b) and GPS antenna (ANT.3). ANT.1 and ANT.2 are connected through antenna amplifiers to the adapter of the ground station by the appropriate antenna cable. ANT.3 is directly connected to the adapter of the ground station by antenna cable. (i) Omni-directional Antenna. ANT.1 is a 400 MHz omni- directional antenna which is used to receive data from a radiosonde and transmit it to the ground station. The ANT.1 is especially made for ascents with a direct view to the radiosonde of an angle up to 45°. (ii) Helix Antenna. ANT.2 is a 400 MHz helix antenna which is used to cover the angle from 45° up to 90° (overhead ascents). (iii) GPS Antenna. The antenna ANT.3 is used to receive the GPS signals to get the correct position.  65 Fig. 2.15 - Different types of Antenna (iv) Adapter Ground Station. Adapter Ground Station is connected with the output from ANT.1 antenna amplifier, ANT.2 antenna amplifier and ANT.3 through the appropriate antenna cables. There is no amplifier needed for the GPS antenna. (v) Lightning and Radar Protection Kit. This kit is installed along with the overhead antenna. It is used to protect the Ground station unit by neutralizing the lightning strokes. It also keeps the system safe from the disturbances of radar signals. (c) Ground Station. The GS-E ground station consists of the following parts: - (i) Tough Book. This system is basically a computer or a notebook. Windows Operating System and various Met software with visual interface are pre-installed in this system. The tough book is used for initializing the Sonde prior to launch of balloon along with the payload, processing the ascent, viewing messages, graphs and diagrams, printing, data storing/retrieval and other purposes. (ii) GS-E Ground Station. The GS-E ground station is the receiving unit. It contains the necessary hardware parts for the upper air sounding like receiver, interfaces for radiosonde and the computer, a GPS module and an antenna switch for antenna diversity. It can be used with any common computer like notebook, desktop PC or other office or industrial  66 PC version for the acquisition of measured data during a meteorological balloon ascent. (iii) DFM-06 Radiosonde. is the Met payload which is attached to a balloon. The Radiosonde consists of a sensor suite to measure temperature, humidity and pressure at different levels and a radio transmitter. The DFM-06 contains four parts namely:- (aa) DFM-06 Radiosonde (This unit consists of Transmitter, Battery, GPS, Temperature and Humidity sensors). (ab) Securing Pole. (ac) Unwinder. (ad) Parachute. (iv) Printer. In addition, HP colour laser jet printer model CP 3525n is connected to the Toughbook for printing messages, graphs, diagrams, etc. (v) Uninterrupted Power Supply. An UPS 1500 VA make APC for providing continuous power supply to the Toughbook, GS-E receiver and the printer. (a) Tough book (b) GS-E Ground station (c) DFM-06 Radiosonde Fig. 2.16 - Ground station components Pre-Flight Procedure 75. Initialisation of Sounding. Click on the GRAWMET desktop icon to start the software. The GRAWMET window will open. Click on the appropriate shortcut to start the Initialisation ) pop up window opens asking whether to initialise the radiosonde with the wizard or with the common Initialisation through the Initialisation process. The software offers a very simple Initialisation process via an Initialisation wizard in a series of steps. These are illustrated in the succeeding sub paras.  67 (a) Information on Ground station. Enter the Earth octant, location of station, ID number of station, WMO Block ID (if necessary) and station name on the ground station and click on the next button. (b) Selection of Sounding or Simulation. Select "Sounding" and click on the Next button to start a real ascent. (c) Initialisation of Radiosonde. Remove the elastic band and release the antenna from the DFM-06 radiosonde. Open the radiosonde by carefully lifting the cover up. Pull the sensor boom carefully sideways out of the folder. Do not touch the sensor head. Connect the radiosonde to the ground station with the interface cable. Make sure that the green LED lights up. Click on the Initialize Radiosonde button to start the Initialisation process. The software reads in the configuration of the radiosonde automatically (GPS data and EEPROM data). The software notifies the successful Initialisation process with when the radiosonde is initialised successfully. Fig. 2.17 - Menu Programme Fig. 2.18 - Choose Programme Fig. 2.19 - Enter Ground Station Info Fig. 2.20 - Select Mode  68 Fig. 2.22 - Initialise Probe (d) Frequency Setting. In the next step, set the transmitting frequency. The frequency can be set in 20 kHz steps (Bandwidth 400 406 MHz). Click on the MHz and KHz buttons to select the suitable frequency and click on the apply button to confirm the settings. To avoid conflicts with other transmitters, use the sweep function to scan the bandwidth (frequency scan). Click on the Sweep button to perform a frequency check. The "Frequency Scan (Sweep)" window opens. Click on Start button to scan the bandwidth. Now the frequency band will be scanned. Fig.2.23 - Set Frequency Fig. 2.24 - Select view (e) Selection of View. For selecting the view (diagrams and tables) which will be opened automatically after the ascent starts. Mark the appropriate checkboxes for tables and diagrams. Click on the Next button to proceed. (f) Entering Ground Values. Enter the ground values manually (pressure, temperature, humidity, etc.) before starting the sounding.  69 Fig. 2.25 - Initialise Ground Value Fig. 2.26 - Enter Ground Values (g) Start Sounding. Click on the. Ensure that the power supply of the radiosonde is turned ON, before disconnecting the interface cable. After disconnecting the cable of permanently lit. Use the securing plate to fix the sensor in place. Carefully move the holder over the sensor and the radiosonde into place. Slide the holder up to the stop mark. Open the Unwinder. The securing pole is already connected to the unwinding line. Screw the securing pole clockwise carefully into the threaded hole in the holder. Screw the securing pole approx. halfway into the holder. Ensure that the holder curves slightly upwards. The holder must be upright. The holder is now secured in place. (h) Checking Initialisation. The software detects the launch of the balloon automatically by increasing height or decreasing pressure. Check at the status bar before launching the balloon to make sure that the ground station and the radiosonde is initialised correctly and for sufficient receiving level. The "State" shows with a colour, whether the balloon can be launched or not. Following are the colour schemes that indicate the status of ground station and radiosonde and level of receiving signal: - (i) Green Status. Ready launch the balloon. (ii) Yellow Status. Don't launch the balloon the radiosonde is initialised correctly but GPS and/or data signal is missing. (iii) Red Status. Don't launch the balloon the radiosonde is not initialised and GPS and data signal is missing. (iv) Green Signal Bar. Optimal receiving level. (v) Yellow Signal Bar. Sufficient receiving level. (vi) Red Signal Bar. Insufficient receiving level.  70 Fig. 2.27 - Status Bar Initialisation & Receiving Level 76. Assembling Balloon Filling Unit. It is to be kept in mind (while operating the UASS system) that all the threads are left handed. After opening the coffer, take out the flexible pressure tube and the earthing kit. Take the pedestal out of the coffer using the carrying handle that is located below tube. NEVER USE INFLATING NOZZLE (MADE OF BRASS) FOR CARRYING PEDESTAL. The following procedures are observed while assembling the Balloon Filling Unit: - (a) After placing the pedestal on a stable ground, connect the earthing cable to the pedestal at the provided screw. Inflating Nozzle (a) Pedestal on stable ground Earthing Screw Carrying Handle (b) Earthing screw (c) Connecting earthing cable Fig. 2.28 - Connecting earthing cable to the pedestal (b) The other end of the earthing-cable should either be connected to the earthing rod, which is hammered into the earth with the provided plastic- hammer; or be connected to a properly earthed connector (e.g. on vessels).  71 Fig. 2.29 - Connecting earthing cable to earthing rod (c) The pressure reduction valve is mounted on the hydrogen cylinder by means of the provided wrench. Ensure that pressure gauge and flexible tube are fully tight. Make sure, that the cylinder valve and the reduction valve are closed. Wrench Yellow blow-off (a) Fixing pressure reduction valve /gauge (b) Fixing flexible pressure tube Cylinder Gas Cylinder Valve Pressure Indicator e Gas Releasing Pressure Re duction Valve Val ve (c) Flexible pressure tube (d) Yellow blow-off Fig. 2.30 - Mounting the pressure reduction valve & connecting the flexible pressure tube (d) The flexible pressure tube is connected on other side to the pedestal by the provided wrench. Make sure, that the yellow blow-off valve on the pedestal is closed. 77. Filling Balloon. After assembling the Balloon Filling Unit, check if the nozzle of the Balloon Filling Unit can be moved up and down easily. If it does not move  72 smoothly, lubricate the moving elements with the provided grease. The following steps are followed while filling the balloon: - (a) Make sure, that the yellow blows off valve on the pedestal is closed. Weights are not to be put on the hooks of the Balloon Filling Unit. (b) Put the neck of the balloon over the inflating nozzle. Tie the balloon with a short cord on the nozzle to fix it against accidental slipping off. (c) Open the gas-valve on the cylinder. After this, open the reduction valve and watch the pressure indicator. Adjust the pressure at the reduction valve to around 0.8 bar. 0.8 Bar Pressure Reduction Valve Fig. 2.31 and Fig. 2.32 - Opening the valve and adjusting the pressure (d) Inflate gas until nozzle lifts up and stops gas inflation automatically. Close gas valve of cylinder and pressure reduction valve. To reduce the amount of gas blown into the balloon, open the yellow blow off valve on the pedestal and release some gas. Make sure to close the yellow blow off valve again. Close the neck of the balloon over the nozzle of the Balloon Filling Unit by tying a piece of lace around it (the neck must be closed by the lace). 78. Preparation of Balloon-rig and Releasing Balloon. Tie the top of the parachute with 1 m cord strongly on the neck of the balloon. Tie the bottom of the parachute to the bottom of the un winder. Tie the radiosonde to the bottom end of the un winder. Slowly release the balloon with the payload. 79. Observation of Data in Toughbook using GRAWMET Software. The software has the provision for viewing and evaluating the sounding data through a variety of diagrams and tables. For viewing the profile of the sounding data in tabular. To view the main menu.  73 Fig. 2.33 - Sample view of data in tabular form Fig.2.34 - Sounding Data in graphical form 80. Terminating Ascent. When the desired height of the radiosonde is reached, clicking on the appropriate shortcut. The software can also terminate the sounding automatically when it detects the bursting of balloon. Post-Flight Procedure 81. The present generation GPS based Radiosonde Ground Station are capable of operations in any kind of weather, even in very adverse weather conditions. The  74 software provided with the system will automatically process the measured data and display it in the form of tables or graphical representation. This enables immediate availability of upper air profile of winds and temperature at a station. The system can also automatically generate the standardised upper air messages like PILOT, TEMP and Ballistic layer m -grams. 82. WMO Messages. The software of the system creates WMO weather. The shortcut can also be used to open the weather messages window. There is an option in the left part of the window (tree) to select different messages (TEMP, PILOT, CLIMAT and ballistic messages). Any of the supported encoding methods (FM35 TEMP, FM 36 SHIP and FM38 MOBILE) can also be selected using this option. The selected messages will appear in the right part of the window. Fig. 2.35 - Messages 83. Additional Functions and Diagrams. There are few additional functions like calculate, save, print and edit. The active diagram or table can be saved using the Save button. With the Print button the active diagram can be printed. With the Calculate button the messages can be created again. With the Edit button the values can be edited by clicking on them. The software has a provision to display the measured data in various diagrams. These diagrams can be seen during the ascent. Select the diagrams in the menu with a click on "View". Alternatively, the shortcuts can be used to open the diagrams. These diagrams are as follows: - (a) Stüve-Diagram (b) Balloon track (c) Refraction index (d) T- Log (P) / Skew-T diagram (e) -grams (f) Emagram  75 (g) Hodograph (h) Altitude Diagram (j) Altitude Wind Diagram 84. Storage and Reports. After the ascent is finished, all raw data are stored automatically in the data base. The same ascent can be repeated in the simulation mode or loaded from the archive for further evaluations. A simulation file is only created when the checkbox "Create simulation file" is activated in the main menu under "Options _ Settings _Simulation entry". The software offers a variety of reports e.g. summary report, wind report, altitude report, etc. Fig. 2.36 Frequency of Observation 85. Radiosonde ascents are taken twice in a day (0000 UTC and 1200 UTC). Units are to take ascents as directed by Air HQ depending upon the hydrogen gas availability from local procurement/ supply from Central Met Stores. Dissemination of Data 86. The upper air data (TTAA, Freezing Level, 600 hPa, PPAA & PPBB) obtained from UASS are to be entered in the Mausam Online (MOL) website besides filling other relevant data, in. C Met Os to ensure that the data is disseminated through MOL on routine basis.  76 Fig. 2.37 - Upper Wind Module in MOL Website Safety Instructions 87. The Tough book should not be connected to internet and it is to be used exclusively for the purpose of UASS ascents only. The following safety instructions are to be observed while filling the balloon with hydrogen: - (a) The Balloon Filling Unit must be grounded using the earthing-rod and on metal ground, by connecting the earthing-cable to any earthed screw etc. (b) The balloon filling unit and the gas cylinder should be kept away from fire and electricity. (c) As far as possible, the gas-cylinder is to be put away from the Balloon Filling Unit. (d) The balloon should be filled in open room/area with sufficient ventilation. (e) The gas-valve on cylinder must always be closed when not in use. (f) instead use the handle while doing so. (g) Only use the provided spark-proof tools (hammer, wrench) for setting up the balloon filling-unit. (h) All safety precautions for handling and usage of H2 gas as per IAP / policies letters must be followed at all times.  77 88. The balloon must be handled very carefully on ground to avoid a low altitude burst. The following is to be ensured: - (a) Discard balloons having visible damages as such balloons can lead to an earlier burst than expected. (b) The balloon must be handled very carefully. (c) (d) (e) Being international standard for hydrogen-applications, all threads are left-handed. Troubleshooting 89. There are some errors / error messages of the GRAWMET Software, which can be resolved by local troubleshooting are discussed in the following paragraphs. If troubleshooting is unsuccessful, Central Met Stores needs to be contacted. 90. Errors Concerning the Program Start. Faults occurring during starting of UASS program / GRAWMET software with probable troubleshooting are discussed below. (a) An error message "Sonde COM port is not available!" is displayed when wrong COM port for the radiosonde is selected or the USB cable is not connected to the radiosonde. Ensure that USB cable is connected to the ground station or correct COM ports for the radiosonde are selected (see GRAWMET software manual GRS-KD-0002). If both steps were not successful, replace the USB cable or try another USB port on the ground station. Drivers need to be installed afresh for the USB cable if there is a change in the USB port on the ground station. (b) Error message showing "Initialize GPS Module (Station) failed" appears when GRAWMET cannot find the interface/GPS card. GRAWMET only looks for the interface/GPS card when the Interface card is selected in the cable in the text field Communication.  78 Fig. 2.38 - Program Settings Window (c) whenever GRAWMET software didn't find the receiver card, an error message "Initialize receiver failed" appears. GRAWMET only looks for the receiver card when the ESE-1 is selected as receiver type. To resolve, click on -2 as the receiver type in the text field. Fig. 2.39 - Program Settings Window (d) An error message "No mixer found" appears when there are more than one soundcards installed. Ensure that the correct soundcard is selected from Device Manager and disable all other soundcards which are not needed. If there is an external USB soundcard, ensure that it is connected correctly to your computer. 91. Errors Concerning the Initialisation Process. Faults occurring during Initialisation process with probable troubleshooting are discussed below: - (a) An error message "Probe does not response" appears if GRAWMET cannot detect a radiosonde even after selecting correct radiosonde in GRAWMET software. Reconnect the radiosonde in USB cable and / or Restart GRAWMET. Then try to initialise the radiosonde again. It is also to be ensured that the USB cable is connected to the same USB port every time. Otherwise windows will detect the USB cable as a new hardware device and its driver needs to be reinstalled every time. In this case it is possible that the USB cable gets new virtual COM ports with any number greater than 16 (ports number to be between 1 and 16). If not, change the settings by selecting a COM port Lastly, replace the radiosonde if none of the previous steps was successful, probably due to defected radiosonde, and initialise again.  79 (b) An error message showing "Unexpected error during reading radiosondes. Please look at log file for more details!" appears if wrong COM port for the radiosonde is selected. Check the radiosonde settings and ensure that the correct COM ports for the radiosonde are selected. (c) Error message "EEPROM-Numbers at probe not proper" appears if the wrong COM ports for the radiosonde are selected or the radiosonde is broken. Check the radiosonde settings. Ensure that the correct COM ports for the radiosonde are selected. If not successful, replace the radiosonde and initialise again. (c) Error message "Reference does not exist" appears if the reference measurement on the radiosonde does not work properly. Reconnect/replace the radiosonde and initialise again. (d) Error message: "Illegal sensor at probe was set up!" appears when the radiosonde is defected. In this case replace the radiosonde and initialise again. (e) Error message "Transmit channel number failed" can appear after the Initialisation process when the transmitting frequency could not be transmitted from the ground station to the radiosonde or the wrong radiosonde is selected. Reconnect the radiosonde and initialise again. Ensure that the correct radiosonde is selected from radiosonde settings. (f) Error message: "Initialize GPS messages failed. Try again? appear after changing the COM port settings. Reconnect the radiosonde and initialise again. 92. Errors Concerning the Reception of Data. Faults occurring during reception of data with probable troubleshooting are discussed below. (a) (indicated by gaps in the left box of the raw data table) appears if the wrong input for the soundcard is selected or the soundcard is not supported by GRAWMET. To check the receiving level, have a look at the field "Signal" in the status bar at the bottom of the GRAWMET window. Green or yellow Colors means a sufficient receiving level. Red means an inadequate receiving level. Check whether the receiver is connected to the ground station and whether it is switched on and also, check the connection of the antennas.  80 3 4 1 8 7 2 6 5 Fig. 2.40 - Label wise explanations Label Explanation No. 1 Input power supply voltage with power switch for 110 - 250 V/AC. Do not use a higher or a lower voltage otherwise this can damage the device. 2 Input low potential voltage for 10-32 V/DC for mobile solutions. Do not use a higher or a lower voltage otherwise this can damage the device. 3 USB IN: Connect the computer via USB cable here. 4 USB OUT: Connect the GRAW USB interface cable for the radiosonde here. Alternatively, you can connect the interface cable to a USB port of the PC. 5 ANT.1: Connect the cable from the ANT.1 (omni-directional antenna) here. 6 ANT.2: Connect the cable from the ANT.2 (helical antenna) here. 7 ANT.3: Connect the GPS antenna here. 8 ANT.4: Connect an indoor GPS repeater here to provide indoor GPS. (b) After checking connections, quit GRAWMET software. Ensure that the driver for sound card is installed correctly, correct soundcard is selected from Device Manager and disable all other soundcards which are not needed. If there is an external USB soundcard, ensure that it is connected correctly to your computer. (c) Missing GPS signal (shown by gaps in the right box Place the radiosonde above the repeater antenna, if inside the room (the  81 antenna of the radiosonde has to show to the top). If outside, place the radiosonde to a position the antenna showing to the ground. Ensure that the correct type of radiosonde is selected in radiosonde settings and radiosonde have at least 4 necessary satellites signals to receive a sufficient GPS signal. It can take some minutes until the GPS signal is available (lock in time). Lastly, antennas to be ensured connected correctly at the ground station and outside (e.g. roof). Maintenance 93. The equipment is required to be looked after for optimum use of the system. Checks based on certain time frame are suggested below and records are to be maintained as per Annexure 1: - (a) Daily Checks. Following checks are to be ensured on daily basis: - (i) Physical Check. Check for any physical clinks, bends, damage, ants in wires, antennae. (ii) Connectivity Check. Check for connections between various components. (b) Weekly Checks. Following checks are to be carried out on weekly basis: - (i) Check tightness of connectors of interconnecting cables between various subassemblies. (ii) Check the voltage of batteries of UPS. (iii) Check earthing status by checking voltage difference between earth and neutral of the input to the equipment components. This should be always less than 05 Volt. (iv) Check the voltage of phase, earth and neutral. (c) Monthly Checks. Following checks need to be carried out on monthly basis: -  82 (i) Physical inspection of outdoor components. (ii) Go to rooftop and perform visual inspection for damage Antenna / Cable and GPS Antenna / Cable, if any. (iii) Report any fault/ suspicious or damaged elements to Central Met Stores. (iv) Check the backup time of online UPS APC (1.5 KVA) to know the battery condition. It should be approx. 10 minutes with fully charged battery and with the load of one PC. Actions During Unserviceability 94. During the event of any unserviceability or malfunctioning in equipment operation, following actions will be taken by the unit: - (a) Unit will take the help of user/maintenance manual provided along with the system for identification of fault and its user level rectification (if recommended by the CMS/OEM). (b) Fault will be booked with Central Met Stores through signal / telephone by the concerned unit. In addition, the attached failure/status report (Annexure 2) also is required to be sent to the OEM through email ID [email protected] with a copy to [email protected] during through Central Met Stores. (c) In case of malfunctioning of software/ communication system, required log file as suggested by the OEM need to be made available to AFCNWP / CMS for further dissemination to the OEM. Accounting of Consumables (Sonde, Balloon and Hydrogen Gas) 95. All consumables (Balloon, Sonde and Hydrogen gas) will be accounted as per the present system of accounting. A BOC action of all consumables will be completed in their respective consumable registers immediately after receipt of the same at units. Voucher action will be followed based on receipt of Issue Voucher (IV) from CMS, Requirement of consumables for next year along with existing stock position and consumable pattern during last six months will be communicated to CMS along with annual demand of Met consumables by the concerned units. 96. All maintenance activities are to be recorded in the MME Maintenance register. A copy of maintenance schedule may be pasted in the respective section of the register for ready references. The format of maintenance entry in the register is placed as Annexure 2. The Fault Rectification Register (FRR) is to be used for logging all the faults observed / reported about the Equipment and rectification actions carried out by Unit / PEC Representative. The format of unserviceability record in the FRR register is placed as Annexure 3. The format for batteries replacement dates placed at Annexure 4 is to be included in the MME Maintenance register for future references  83 and proactive action for replacement of the exhausted batteries. This record comprises the batteries issued to Met Section for various types of UPS issued to Met Section by Central Met Stores. LIGHTNING DETECTION SYSTEM Introduction 97. Atmospheric Lightning refers to electrical discharges within a cloud and cloud to ground, known as IC (Intra-Cloud) and CG (Cloud to Ground) respectively. Lightning occurs when electrical fields within a cloud intensify as particles of opposite polarity collect at differing regions. Below the negatively charged thunderstorm cloud base, positive charges begin to gather on the ground. A cloud to ground lightning strike begins as an invisible channel of electrically charged air moving from cloud to ground called a stepped leader as it moves in steps in nanoseconds. When this initial electrical breakdown pulse approaches an object on the ground, a powerful surge of electricity from the ground moves upwards to the cloud (called leader channel) and produces the visible lightning strike. This type of lightning is called negative lightning because negative charges are moving from cloud to ground. Similarly, when lightning occurs from positive charges located at top portion of the cloud, it is called positive lightning. Positive lightning when strikes ground is extremely dangerous as it has exceptionally high current and voltage to make its way from top of the cloud towards the ground. Positive lightning amounts to just 5% of the total lightning strikes. 98. Lightning detection has great value for real time storm tracking, warning, and now casting as well as estimating rainfall. In remote regions where conventional data sources are not available, tracking of thunderstorms and assessing their intensification / track are important challenges in weather prediction. These potentially deadly weather events often occur within 5 to 30 minutes of Intra-Cloud (IC) flash initiation. The lightning sensors installed at various locations detect millions of flashes each day, utilizing time-of-arrival methodology over a broad frequency range of 1 Hz to 12 MHz and employing adaptive digital filtering. The system provides the highest levels of detection efficiency in real time. It has ability to significantly improve severe weather warning times over radar and other technologies, incorporating highly advanced predictive capabilities that are crucial for characterizing severe storm precursors, improving severe storm warning lead times, and comprehensive weather management planning. Working Principle & Components 99. An overview of LDS is illustrated below: -