 My dear students, dear formers, and my friends, I invite you all for this online course on weather forecast in agriculture and agro-adversaries. This is a practical output from the field of agricultural metrology. Why this is required? You may ask certain questions on this topic. This is mostly required considering number one. The cultivable area comes down. There is threatening from the change in the weather and climate. And the third dimension is the food demand from the increasing population. So, this topic is being discussed timely in this online course. Now, let me say something on this. Shall we go rightly to the topic without understanding the basic things, we must have some understanding on the basic aspects of metrology. And you may ask sometimes why this course is necessary, why should I understand, this is mostly required to reduce the crop production risk under open field conditions. Now, let me start some basic aspects of atmosphere, how crop interacts with weather may be positive or negative, how this risk is being reduced by management like weather forecast and advisories. And I also like to focus certain case studies also. Now, let us start some basic aspects of metrology so that you can understand the topic very well. Now, let me say about atmosphere. This is four mostly important you have to understand. If I say atmosphere, it is a component of your earth. Earth has three sectors, one is atmosphere, another one is your hydrosphere and the third one is earth itself lithosphere. There is always interaction may be positive or may be negative between earth and atmosphere, between earth and ocean, between ocean and atmosphere, between atmosphere and earth. So, triple interaction always going on whether it gives positive or negative way out to adapt to these situations. Suppose there is no atmosphere to the earth, can we have life? There is no life because the gaseous component that envelops our atmosphere is up to a depth of 10,000 kilometers. So, it is a gaseous component. This regulates the radiation or energy and light to your earth from the atmosphere. It is an intermittent interface layer between your sun and your earth if there is no atmosphere. What will happen in the day? The day temperature goes up to 95 degree centigrade. See how much? Similarly, after all outgoing radiation, the night temperature would fall to minus 100 and 45 degree centigrade. Hence, there is no life. So, this is very very important. The presence of atmosphere is very important considering this aspect. Now, I like to say certain things about the atmosphere. The atmosphere has deep blanket of gaseous. The total mass estimated to be 56 into 10 to the power of 1410. Since it is a gaseous component, it contains nitrogen up to 78 percent by volume, oxygen by 20.9 percent by volume, argon 0.93 percent by volume, carbon dioxide 0.03 percent by volume and in addition to these gases, neon, helium, methane, kryptin and hydrogen present at negligible level. These are all gaseous components. In addition, you have solid components also like aerosol and water vapor present at the atmosphere. You can ask question, is it constant up to the level of the atmosphere or will it be varying at the different heights? I say this is constant up to 80 to 100 kilometer. So, now you could understand, appreciate some physics of the atmosphere. Now, let me say how the atmosphere arranged in layers based on the temperature. This is very, very important. You see from the bottom, you can see here, it goes from here. The lowest layer is troposphere. It is 60 to 18 kilometer at equator, 8 kilometer from the poles because of the arrangement of the earth's shape and size. This troposphere contains 70 percent of the total gases, water vapor, aerosol and there is a decrease in temperature at every kilometer height. The decrease is 6.5 degree centigrade per kilometer. This continues up to minus 28 degree centigrade. So, there is a temperature decrease with height at the troposphere. The next two troposphere, there is a media or a middle component that we call it as your tropopause. The tropopause here, it is above the troposphere where the warm air start is coming there after that. So, after the tropopause, you have a stratosphere. This is 50 kilometer from the your troposphere. Here in the temperature though it is increasing as compared to your troposphere, it is constant up to 20 kilometer and exceed up to 50 kilometer. Then after that, there is stratopause. This is maximum temperature with the absorption of UV rays. So, first troposphere, decrease in temperature with height, then stratosphere. Here temperature gets warmed and stratopause, maximum temperature with the absorption of UV rays. Then next one is your mesosphere. Here is around 80 kilometer from the earth. Temperature decreases to a minimum of minus 90 degree around 80 kilometers height. Then after that there is mesopause. Then there is a thermosphere. The density is less. Oxygen, nitrogen present. Molecular and atoms of oxygen present. Temperature increase with height. Temperature is up to 980 degree centigrade. Then thereafter your exosphere. It has got height of 10,000 kilometers beyond that there is space. So, this is very important one for these things. Okay, we have understood the layers of atmosphere by text. Now, let me see through pictorial representation also. In the left side Y axis, how the pressure gets varied. That pressure means atmospheric pressure gets varied with altitude. And also there is a change in temperature as I indicated earlier in our earlier discussion. With height the temperature gets decreased at the troposphere level. Then beyond that there is increase in the temperature. So, this is very important basically for other things. Now we can see why this atmosphere is there. What we enjoy today? Weather and climate. The birthplace of weather is the atmosphere. Because the simple interaction between the land atmosphere and between the land and ocean and between ocean and your atmosphere. So, the birthplace of weather is your atmosphere. That too the pertinent layer is a troposphere. The lower most layer of the atmosphere. Can we say, define the weather? Yes, weather is day to day change in the atmosphere. What is the common of the day to day change? It is nothing but heat and moisture. See, change in heat and moisture in the atmosphere we call it weather that is a short time change. So, the weather is nothing but today we have example rainy weather. Commonly we get rainfall. Then dry weather, windy weather or misty weather or fog weather. So, the weather refers to a day of change in the atmosphere. Let us go to the other common climate. People will use wrongly the word climate or day to day change in the atmosphere. I can quote some example. Two fellows are going on a street. One fellow is saying that today the climate is very good. This is a wrong wading. Today the weather is very good. Climate does not reflect weather. Both are entirely different. Then how to define the climate? So, average of composite weather. So many months of weather, so many years of weather. So, average of composite weather of larger region may be a district, may be a state, may be a country computed from the data of more than 30 years. The old meteorological organization prescribes that climate must be characterized by taking 30 years data. Now, I want to quote some example. Simple thumb rule. Say they say climate of different areas but I have developed my own based on the annual total evaporation and also total annual rainfall. Now, air heat climate. You can say it is a dry climate. When the annual rainfall is 50 percent lesser than or 50 percent of the PET suppose PET is annually 2000 millimetre if the rainfall is 1000 millimetre then we can call it is air heat climate lesser than 50 percent then semi air heat climate when the annual rainfall is 50 to 79 percent of the annual PET we call it as semi air heat climate then sub humid climate when annual rainfall is 80 to 90 percent of the annual PET then we call it as sub humid climate here there are two sub types based on the temperature one is dry another one is wet the annual rainfall is 80 to 90 percent of the annual PET but when the temperature is more than 30 degrees centigrade we call it as dry sub humid when the temperature is lesser than 20 degrees centigrade we call it as wet sub humid climate then the other climate is humid climate here the annual rainfall is 100 percent to annual PET economically we can call it as break even point rainfall and PET are in equal per humid climate when annual rainfall is more than annual PET so these are some example for climate so today's class I have given certain basic aspects of atmosphere with this we will be seeing some interesting subject in the next class thank you very much