Make your own free website on Tripod.com
Lightning
Monitoring and Detection

HOME

Why Lightning Occurs
Types of Lightning
Prevention Techniques
Monitoring and Detection
Further Information

The best way to warn and understand about lightning is to monitor its formation and occurrence.

Good monitoring could give sufficient time to warn the public of the possibility of a lightning storm.  

The monitoring of weather using satellite imaging along with other methods of protection can be combined to increase the effectiveness of monitoring.

There are three types of monitoring devices, space, ground and air based.

picture62.jpg

Space Based Sensors

Space based sensors provide several times more information than ground based sensors.  Where ground and airborne can only usually detect cloud to ground lightning it is the space based sensors that are capable of detecting other types of lightning along with increasing its range, as these can detect over the ocean where others can not.  It is space based sensors that will enable the first global database of lightning activity which could then be used for detection and analysis of the storms.

Lightning Imaging Sensor:

The LIS is onboard an observatory that is orbiting the earth.  This sensor comprises of an imager which has a resolution of 4-7km over an area of 600 x 600km on the earths surface.  The speed the satellite is orbiting the earth allows 90 seconds possible observation time for each point on the earths surface that it passes over.  This is sufficient enough to estimate the flashing rate of a storm.  The LIS records the time of occurrence, the radiant energy and determines the location.  Weak lightning signals that occur during the day are difficult to detect due to background illumination, however this device contains a real time processor which removes the background signal which leaves this machine with a 90% detection efficiency.  The LIS data from three months has been combined to form a lightning climatology map, as shown below.  This is very useful illustration of the distribution of lightning which may then lead to the possibility of prediction of such storms as it shows where they are most likely to occur.  Overall this is an extremely useful instrument which provides a lot of reliable data.

picture72.jpg
Lightning Climatology Map

Ground Based Sensors

One of the most common ground based methods of monitoring is the Advanced Lightning Direction Finder which detects cloud to ground lightning and then determines their location by triangulation of two or more lines of bearing.  The ALDF ignore any other kinds of lightning only detecting 90% of cloud to ground lightning with a range of 100km.

There is a ground based instrument that can detect all types of lightning called Lightning Detection and Ranging.  It consists of seven antennas which detect electromagnetic pulses at 66MHz which allows it to detect 99% of all lightning types within 10km.  The range on this instrument however, is not very good as it means that at 90km the location point can vary by 10km which is clearly a large value and as the accuracy gets worse as the distance increases this becomes very inaccurate when it comes to locating storms that are happening further away.

 

Summary

Out of all the methods of monitoring and detecting lightning it is the space based instruments that are the most useful, being able to detect both the type and location of the lightning fairly accurately, where as ground based systems can only usually detect cloud to ground lightning which only constitutes 25% of all lightning.  The data collected from these space based instruments is very useful and has enabled the plotting of things such as the seasonal lightning summary shown earlier in figure 3 which can then be used in further research.  Although this is the case the information collected from ground and air based monitoring devices is also important as it is after all the cloud to ground lightning that causes the most damage and so every bit of information that is found out about this is important and may well prove useful.