How Accurate Are Weather Predictions

Introduction

If someone says "Wow. Its raining. What a wonderful climate".

It is not climate but it is weather. 


What is Weather?

Weather is a temporary change in atmosphere.


What is Climate?

But climate is a long time change in atmosphere.


Different between Weather and Climate

For example, Global warming is known as climate change.

But day-to-day changes in atmosphere is known as weather.


What is Weather Forecast

Nowadays we have technologies online to predict weather priorly. But how do we get those data.


Today various alerts like Red, Yellow, Orange alerts issued for various districts.


So, we are very eager to know when will the rains touch its peak.


Which Sectors Weather Forecast play a vital role in Decision Making

  • Agriculture
  • Fishing
  • Construction Works
  • Aviation Industry
  • Shipping Industry
  • Sporting Events
  • Defence & Military


History of Weather Forecasting

Weather forecast data is a very important one,we can't find many people using it in India.


But in foreign countries many people use weather forecasting apps, before leaving their homes.


In India, some 10-15 years back,there was a saying that, if there is an announcement in TV about rain, then it wont rain that day.


But now the weather forecast has become accurate.


How We are Predicting Weather near to Accuracy.

In the history of weather forecasting, lets see about the various technological advancements,

  • Radar Systems,
  • Weather Balloons,
  • Ocean Monitoring Buoys,
  • Satellites.


But how our ancestors predicted weather previously was just by seeing the clouds.


There are various types of clouds in accordance with their height, direction etc.


There are layers of clouds, what is the difference between 2 clouds ?


At what speed clouds are moving.


Like these they have took account of several other factors & predicted weather.


Also with Sun & moon, they have been predicting weather.


For example there is a circle around the moon.


This can say details about the humidity in atmosphere


& with this we can predict weather.


When these advancements start to develop was,


only during 1600 - 1800, many ships start to submerge which caused loss of lives.


and also due to heavy snow fall many people started to die.


In some Asian countries, many floods occurred. In European countries, many cyclones are occurring.


To control these things with advanced technologies was the starting point.


Initially, there was a Doppler radar that functions using the Doppler effect.


Using this, cloud's velocity & distance is known with this rains are forecasted.


This is useful for a short-distance radius of area to predict the weather.


But only after the invention of the satellites,


forecasting of weather went to the next level.


Low Orbiting Satellites

During cold war between America & Soviet Union,


Soviet Union first sent a satellite to space.


Immediately, John F Kennedy announced that, America is going to send Humans to Moon.


Even before this announcement, they have already launched TIROS I & TIROS II.


TIROS I is the first weather satellite that is being sent to space. This satellite sent the photos of clouds.


With these photos, we can know about temperature, wind speed, humidity.


This is the first time in a wide range we have been able to forecast weather.


After TIROS satellite, Nimbus satellites were launched to space for weather forecast.


This was launched in 1969, 3 months prior to moon landing.


Nimbus-3 was the first satellite to send a global set of data to Earth.With the obtained data, they matched it with a huge map and marked those data to visualize them & forecast weather.


With geostationary satellites we can get more accurate global data.


This is similar to making a 3D scan of Earth.


If one satellite does the job then it's a 2D scan.


Likewise, if 2 satellites scan from 2 different angles, towards the equator while rotating along with the Earth.


The position of these satellites is unchanged, on viewing from earth it looks like the satellite is immovable.


So with the same vantage points, these satellites scan the Earth and with this we get a wide range of accurate data about weather.


This satellite takes a photo every 30 seconds. While processing these photos continously it will look like a video.


With this we can know about cloud's direction,air flow & forecast weather.


The next is Polar Orbiting Satellites. This satellite is a very important one. Why because this satellite gives more data than others.


There are many polar orbiting satellites launched to space & are orbiting Earth.


This satellite orbits just above 800km from Earth. This satellite gives us high-resolution photos & data.


This satellite gives data only twice a day but its details are so accurate.


Like peeling an orange using a knife, this satellite., likewise, these satellites, orbit concentrically around Earth to provide various data to us.


Microwaves & Infrareds give us the most critical information about the weather. This is taken using aircrafts & satellites.


Naturally, all objects emit some amount of microwave energy. And also data about microwaves in the atmospheric air is found using these.


Infrared can go through clouds to give us data about temperature & humidity. So with both the microwave & infrared data, we can accurately derive a vertical temperature structure.


The next important thing is Computer models & simulations.


Even though we take all the data, we need to process them first. The process which was used before and now has huge differences.


In those days we can predict weather only for 2-3 days. But now we can predict weather from 10-15 days.


The numerical weather prediction model is an important one.


All data is being given as input & with the help of Artificial Intelligence,which tells what data to consider or not.


This AI keeps updating itself regularly. Each time when the data is given, it predicts by keeping pprevious data too. In this advanced prediction technology, which data to be eliminated & which one to be kept for consideration,self-reading & self-analysis are carried over by this artificial intelligence.


GFS model by America can predict the weather for up to 16 days.


European GFS is different, Indian GFS is different.


Likewise, all major countries have various satellites to predict the weather.


And many countries have a deal, in sharing the data obtained by other countries to effectively forecast data.


Till now we have seen how data is being received, processed & predicted.


By using all the data available from satellites to advanced models, we have been nearing accuracy in forecasting weather effectively.


How Accurate is Forecasting of Weather 

Initially, it was about 20-30% accuracy, but now we have reached an accuracy of about 80-90%.


But why can't we achieve that remaining 10% ? Shall we achieve it in near future ?

Then the answer would be No.


Even with highly advanced technologies, Scientists say, we cant achieve 100% accuracy in prediction of weather.


The reason for this is the Butterfly effect or the Chaos theory.


In 1961, Edward Norton Lorenz an American meteorologist,was running a mathematical weather simulation by inserting some data.


He has a situation to repeat the same data, and when he did so,now the results had a huge varioation than the previous one.


He was so puzzled about what went wrong.


On checking, it was found that rounding of decimal numbers,made those huge variations in weather prediction.


That is, the output had nearly 10,000 units varied than previous one.


So with these simple variations, butter fly effect, chaos theory all start to bloom.


The pendulum is a great example of chaos theory.


It will move in the same direction whenever we move it.When the arms of the pendulum are increased we can't predict its direction.


The initial input is the same, but the output varies.The reason for this may be a small change in input,or it may be due to humidity, wind, temperature.


A goal is set & a ball is to be thrown, if humans throw it may occur some error,so a robot is being used to throw continuosly.


Even with robot the ball will not hit the goal in the same manner,the reason for this is chaos theory.


How do meteorologists approach chaos theory?

In Environmental physics, environment is seen as a fish tank.


The atmosphere is seen as the water in the fish tank. Air flow or a cyclone.,


For instance, if we pour a drop of ink into water, the ink will spread right.


If the water has some sort of flow then the spreading of ink pattern also changes.


Now we cant predict which side the ink is going to spread in water.


We are forecasting weather in these similar terms.


What we are doing is predicting the water flow, ink direction etc., Similarly the same things are done in forecasting too.


All the particles of this Earth follow the law of Physics.


So we can predict a particle's velocity etc. But a small change occuring,which is an uncertainty, that makes a whole lot of difference in outcomes.


In this pendulum, a small force makes a huge change.Likewise a small change can make a huge variation,in butterfly effect, the same thing is said as a small flap of a butterfly can cause huge effects in some other place.


The reason for this is same, a small change in input,but done repeatedly, continuously can cause huge variations.


This is why meteorologists, using AI make several repetitions purposely, this is done to derive at a cluster of results to near the accuracy of prediction.


So with this meteorologists provide predictions that are very close to accuracy.


Even with chaos theory how we are predicting weather accurately is, by using ensemble cluster of possibl;e futures.


Artificial intelligence runs the input data for several times,each time as it runs,there are random changes given,this random changes gives various different outcomes & they would consolidate an average out of it.


This average output is so close to accuracy in predicting weather.Even though we have advanced technologies, Chaos theory being a science concept we need to travel with it.


But with the advanced technologies,we are overcoming all the struggles to near accuracy in predicting weather.


In the last 40 years many lives are being saved & changed for good,So weather forecasting is a fast growing industry today.


So, this is how meteorologists receive, process data & predict weather & issue various alerts to public.


So with this information we can plan our routine & be safe.


There is still more interesting curious stuffs to be known.



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