Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

A significant increase in lightning during rains

Tags:
  1. Jun 13, 2018 #1

    Wrichik Basu

    User Avatar
    Gold Member

    This year in Kolkata, we are facing severe trouble from lightning. In the previous years when it rained, lightning was much less. This time, even before it starts raining, lightning starts, and it reaches the ground, taking lives. As soon as the clouds start appearing, lightning bolts reach out to the ground or tall buildings. Till date, 28 people have lost their lives due to lightning in Kolkata and surrounding regions.

    Pollution is a increasing problem in almost all metropolitan cities, including Kolkata. Can this sudden increase in lightning strikes be accounted by the pollution? Or is their some other explanation for this rise?
     
  2. jcsd
  3. Jun 13, 2018 #2
    Has the temperature this year been higher generally?
    The are many factors which contribute to formation and intensity of thunderstorms, but higher temperature is a big factor.
     
  4. Jun 13, 2018 #3

    davenn

    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    a strange comment to make ??

    you are not going t o get lightning without thunderstorm clouds

    rootone's comments are good. Changes to local climate may well be increasing the formation of thunderstorms
    I doubt that increased air pollution is the cause. You still need the storms to build up before there will be any lightning


    Dave
     
  5. Jun 14, 2018 #4

    Tom.G

    User Avatar
    Science Advisor

    Hey you nay-sayers, try a Google search for Clear Sky Lightning.
     
  6. Jun 14, 2018 #5

    Wrichik Basu

    User Avatar
    Gold Member

    It's much more humid than last year, but temperature is a bit less than last year, around 35° at the most.
     
  7. Jun 14, 2018 #6
    Humidity is also a significant factor.
    Thunderstorms hardly ever happen in desert regions no matter how hot it gets.
     
  8. Jun 14, 2018 #7

    davenn

    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    Clear sky / clear air lightning still comes from a storm cell
    It is just a discharge that leaves the side (usually ) of a cell and comes to ground or dissipates in the air
    It can travel for several km or so horizontally from the cell

    Being a storm chaser, I am VERY aware of them and the need to keep on the lookout for obvious safety reasons
    I have observed a number of clear air strikes over the years but their origin has always been identified

    The point is, there is STILL a storm close at hand probably well within 10km from your location
    so you are not going to be unaware of an approaching storm


    Dave
     
  9. Jun 14, 2018 #8
    Did wind speed pick up just before the lightning began? Was the air dusty before precipitation started?
     
  10. Jun 14, 2018 #9

    Wrichik Basu

    User Avatar
    Gold Member

    No to first one. Yes to the second one.
     
  11. Jun 14, 2018 #10

    OmCheeto

    User Avatar
    Gold Member

    According to the BBC, a very severe lightning storm to your south two months ago was attributed to an unusual weather pattern:

    BBC; "...this year cold winds from the Arabian sea collided with warmer winds from northern India and produced conditions that led to the formation of more clouds than usual, Mr Sanku said.
    This increased the chance of lightning strikes."

    I call it severe, as there were 37,000 lightning strikes recorded in 13 hours. That's very roughly 1 strike per second!

    In a chart [figure 8] published by the Royal Meteorological Society in 2015 [ref], India gets an average of 120,000 lightning strikes per year.
    This means that that one storm accounted for nearly 1/3 of an average year's lighting for the whole country.
     
    Last edited: Jun 15, 2018 at 12:38 AM
  12. Jun 15, 2018 at 12:33 AM #11

    davenn

    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    nice find Om :smile:
     
  13. Jun 15, 2018 at 1:52 AM #12

    OmCheeto

    User Avatar
    Gold Member

    On the other hand, there may be a relation between pollution and lightning:

    https://www.telegraphindia.com/calcutta/smell-of-lightning-in-the-air-237394
    Anirban Middey of the National Environmental Engineering Research Institute, Nagpur, has shown that an increase in the load of aerosols, or tiny particulate matter (PM), in the atmosphere and clouds of ice crystals and water stimulates lightning discharge.


    Anirban Middey's paper discussing this:
    The reciprocal relation between lightning and pollution and their impact over Kolkata, India​


    Unfortunately, the paper is behind a paywall, so I can't see how significant the relationship is.
    Glossing over the references listed in the paper, it does make a bit of sense.
    It's kind of like cloud seeding.
    More seeding/pollution makes more clouds.
    More clouds make more lightning.
    Just a laymanish interpretation, of course.
     
  14. Jun 15, 2018 at 2:40 AM #13

    OmCheeto

    User Avatar
    Gold Member

    This is interesting. I googled: pollution's effects on cloud formation
    and the first hit was an article about a NASA study.
    It's actually more complicated, and interesting, than I would have imagined.

    Formation of clouds linked to air pollution
    by Nasa on 13 July 2006
    “When the overall mixture of aerosol particles in pollution absorbs more sunlight, it is more effective at preventing clouds from forming. When pollutant aerosols are lighter in color and absorb less energy, they have the opposite effect and actually help clouds to form,” said Lorraine Remer of NASA’s Goddard Space Flight Center, Greenbelt, Md.​

    Here's another article by NASA, published about 20 years earlier:

    Atmospheric Aerosols: What Are They, and Why Are They So Important?
    Aug. 1, 1996
    The sulfate aerosols absorb no sunlight but they reflect it
    The sulfate aerosols also enter clouds where they cause the number of cloud droplets to increase but make the droplet sizes smaller.​

    Now all we have to do is figure out what kind of pollutants make up the pollution in Kolkata, and how droplet size affects things.
     
  15. Jun 15, 2018 at 6:27 AM #14
    If it is really a sudden increase then it is most likely just some kind of special weather condition. But for example for us in Middle Europe the climate changed so that way back a few decade ago only around half of the rain during summer was from storms, right now it is around 90%. Also thunderstorms starts early, last year we had one in February, but in March it's already nothing uncommon now. In the past the first ones were expected at the end of May.
     
  16. Jun 15, 2018 at 6:53 AM #15
    Another NASA article, this one on the effect of Saharan sandstorms on Florida weather.

    Not all of the lightning storms that pop up in the American southwest involve precipitation, but rather are generated by dust storms. I'm wondering , could a similar mechanism have played a role in exacerbating this year's storms in India?
     
  17. Jun 16, 2018 at 5:12 AM #16

    davenn

    User Avatar
    Science Advisor
    Gold Member
    2017 Award

    good article :smile:

    I have never seen one that doesnt
     
  18. Jun 16, 2018 at 8:30 AM #17

    Wrichik Basu

    User Avatar
    Gold Member

    Dust storms are common to the central and western India, including our capital New Delhi. In Kolkata, dust storms are started by high velocity winds from a nearby storm carrying water for precipitation. Hence, in most cases, storms are accompanied by rain. But this year, something has happened so as to change the weather abruptly. For the last three days, we are facing extremes of temperatures. Today, it went up to 41°C, highest in this year. The next storm may be dangerous.
     
  19. Jun 16, 2018 at 10:33 AM #18

    jim mcnamara

    User Avatar

    Staff: Mentor

    @OmCheeto - consider taking that 120K lightning strikes per year in India total as an underestimate, possibly by orders of magnitude.

    https://earthobservatory.nasa.gov/IOTD/view.php?id=85600 Cool map!
    Also, Kolkata has a monsoon season, with higher levels of lightning, the map averages that out over a year. I'll get to that.

    Let's use 10 lightning strikes per year per km2 as a conservative interpretation of the map. The surface area of India is: 3,287,259 km2
    so:
    10 * 3287259 = 32872590, let's use 30 million as a really conservative number, for an India-wide estimate of total lightning events.

    From here: https://www.nssl.noaa.gov/education/svrwx101/lightning/types/
    Let's use a factor of 5 air to ground events per 10 lightning events:
    So our 30 million becomes less, 15 million.

    The reason I think this is not a terrible estimate is that one flash can mean a larger number of actual ground strikes, e.g., ~1.45 strikes per flash of cloud to ground per:
    https://www.nasa.gov/centers/goddard/news/topstory/2003/0107lightning.html

    You will also notice there are significant pinkish areas of >=15 times the lightning events we used above. The very light pink stuff on the map. West Bengal has several pink areas, seen when you click to enlarge the map. Perhaps someone else who is local can do a somewhat better napkin estimate for lightning events per year using the map and getting pink to match geography correctly.
    @Wrichik Basu ?

    The other factor is seasonality. I cannot quantify that either, but consider that most rain events in West Bengal occur in the rainy season - (monsoon) from June - September. So in June/July you would expect about 3 times as many lightning strikes as in a non-monsoon month. As a guess. There are months with very little rain - January and December: https://weather-and-climate.com/ave...Temperature-Sunshine-fahrenheit,kolkata,India
     
  20. Jun 16, 2018 at 3:01 PM #19

    OmCheeto

    User Avatar
    Gold Member

    Thanks! I was very suspicious of that 120K number.

    30,000,000/120,000 = 250

    My guess now is that those are daily lightning strikes by year.
    Though, it was not obviously presented that way when I reread that section several times.

    "Figure 8 demonstrates the annual number of lightning fatalities and lightning flashes in India from 1998 to 2005"
     
  21. Jun 17, 2018 at 12:23 AM #20

    Wrichik Basu

    User Avatar
    Gold Member

    Maybe yes, but I can say that the weather department in Kolkata has no information. Perhaps earth scientists monitoring the weather will be able give better answers.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted