[Music] foreign [Music] and I welcome you on board for the first flight in the series of flights to study meteorology for dgca CPL and atpl examination today we will fly through the first topic which is atmosphere so fasten your seat belts as we are ready for takeoff meteorology is a scientific study of atmosphere and weather you cannot think of Aviation without understanding meteorology and the regions are self-explanatory flying is inherently hazardous activity and history of Aviation is full of accidents and incidents with advancement of Technology design deficiency and material failures of airplanes have reduced drastically but we have no control over whether presently there are two major factors which lead to accidents and incidents in the field of Aviation first is human factor and the other is weather weather plays a major role in safe flying operations weather conditions like visibility rain snow thunderstorm icing Crosswinds clouding turbulence wind shear all these have severe impact on safety of flying sometimes extreme weather conditions May impose a complete stoppage of flying or forcing a pilot to divert to alternate Aerodrome knowledge of meteorology and its impact on Aviation arms you with the required knowledge which will help you in taking timely and safe decisions in flying having understood the importance of studying meteorology for flying let's progress on to our first topic of atmosphere remember information or data covered in this video under red outline is to be remembered for the purpose of examination atmosphere is gaseous volume surrounding any planet you need to know the atmosphere since airplanes fly in it atmosphere starts immediately after the surface of Earth and continues upwards towards space boundary of atmosphere atmosphere starts from ground level and extends up to 800 kilometer into space atmosphere up to 80 kilometer is called homosphere and above 80 kilometer it is called hydrosphere as the name suggests the composition of atmosphere is homogeneous below 80 kilometer and heterogeneous above 80 kilometer composition of atmosphere apart from water vapor and dust particles atmosphere is composed of following gases nitrogen 78 percent oxygen 21 percent Argon decimal 95 percent carbon dioxide decimal zero three percent and traces of many other gases the ratio of nitrogen and oxygen is 4 is to 1 by volume and three is to 1 by weight which means that oxygen is heavier than nitrogen if you want to know more about it then go through the atomic number of oxygen and nitrogen temperature pressure humidity and density varies vertically as well as horizontally in atmosphere atmosphere is a poor conductor of heat and electricity remember our atmosphere is heated mainly from the below from RE radiation of Earth and not much from the solar radiation which comes from above you can correlate it with real life situation that whenever there is a fog it does not disappear at the time of sunrise but at a later time like 9 or 10 o'clock since by this time atmosphere gets heated up from below from the Earth's surface greenhouse gases water vapor carbon dioxide and methane gases these are called greenhouse gases greenhouse gases cause Greenhouse Effect and are responsible for keeping the temperature of the earth to an average of 15 degree at mean sea level without this greenhouse effect the temperature would drop to as low as minus 18 degree Centigrade on Earth and that will be too low to sustain the life on Earth but excess of greenhouse gases are causing global warming these gases do not absorb the solar radiation from the sun which is short wave but when Earth is cooling down by radiating energy it absorbs them and re-radiate a portion of it back towards the Earth which is long wave thus causing warming effect if you have studied the means displacement law in physics in class 12 you would know that higher the temperature of a body shorter is the wavelength of radiation and vice versa and of course the sun is much much hotter than earth that is why the solar radiation is of short wavelength and Earth radiation is of long wave radiation dry and saturated air atmosphere holds a large amount of water vapor water vapor is lighter than air in terms of weight this you can correlate it whenever you see a boiling water the water vapor goes in upward Direction and not in downward Direction saturated air means it is already saturated with water and does not want any more of it dry air is dry and can take more water warmer the air more amount of water vapor the air can hold you can remember it by thinking that during warm or summer season your body wants to hold or take more water colder the air less water it can hold you can correlate it with the fact that in Winters your body does not want to hold more water hot weather can be very humid since it can hold more water and in Winters you feel dry since air holds less water when the relative humidity of air is hundred percent it is called saturated air and whenever the relative humidity is less than 100 percent it is called dry or unsaturated air ozone layer ozone layer is responsible for protection of living beings on Earth from harmful effect of UV rays it is found between 10 to 50 kilometer and its maximum concentration is between 20 to 25 kilometer layers of atmosphere generally we know that as we go higher in the sky the temperature decreases and that is why we visit Hill stations in summer to get rid of high temperature in the planes but does the temperature keep reducing forever as we go up well the answer is no temperature reduction with height stops at a given height which is called tropopause based on height above Earth versus temperature profile the atmosphere has been divided into many layers let us understand what these layers are with the help of a diagram these layers are troposphere Stratosphere mesosphere and thermosphere troposphere is the lowest portion of atmosphere it extends from ground level up to a height of 11 kilometer or 36090 feet in troposphere temperature reduces with increase in height the rate of reduction of temperature with height is called lapse rate in the troposphere lapse rate is 6 decimal 5 degree per kilometer or one decimal 98 Degrees per thousand feet troposphere consists of 3 4 of total atmosphere in terms of weight and most of the weather phenomena occurs in troposphere tropopause is drop of top of troposphere where the reduction of temperature with height stops the height of tropopause is 16 to 18 kilometer over equator and 8 to 10 kilometer over the poles the height of tropopause over equator is higher because equator is warmer as compared to poles equator receives more solar radiation and therefore the air rises to higher height and reduces the temperature of atmosphere due to expansion Cooling at ground level equator is warmer than poles but at tropopause it is other way around since height of tropopause is higher at Equator the temperature is colder due to lapse rate as compared to a temperature at tropopause over the poles there are two reasons where tropopause abruptly changes height and these are called breaks or folds first is at 40 degree latitude and second at 60 degree latitude most of the weather phenomena like clouding jet streams clear air turbulence all these occur below the tropopause so hence this layer of atmosphere is the most important to study from the perspective of Aviation next is Stratosphere Stratosphere extends from tropopause up to a height of 50 kilometer from 11 to 20 kilometer the temperature is fixed at -56 decimal 5 degree and thereafter it starts increasing slowly with increase in height it is a very stable region with very low humidity and almost no weather rather any atmospheric reason where temperature is either stable or increase with height also called inversion is a stable region sometimes neck race clouds also called mother of pearl clouds are seen in Upper Stratosphere in higher latitude in Winters stratopause is the upper boundary of Stratosphere next is mesosphere mesosphere extends from stratopause to a height of 80 kilometer temperature starts reducing again with increase in height like proposed like troposphere on rare occasions noctilucent clouds are seen in Upper mesosphere in polar regions the top of the mesosphere is called mesopause the last sphere is thermosphere thermosphere extends from mesopause to the end of the atmosphere where temperature increases with height till atmosphere ends at approximately 800 kilometer International standard atmosphere parameters like temperature pressure density lapse rate Etc are never constant in actual atmosphere and Vary from place to place so there was a need to standardize the atmospheric conditions for the purpose of testing and evaluation of aircraft and engine performance for this International civil aviation organization standardized the definition of atmosphere which is known as International standard atmosphere and they are important from the exam perspective and these standard definition of atmosphere are as follows air is considered to be dry mean sea level temperature is 15 degree Celsius mean sea level pressure is 1013 decimal to 5 hectopascal or 29 decimal 92 inches of mercury or 760 mm of mercury all are same mean sea level density is one decimal 2 to 5 kg per meter cube lapse rate in the atmosphere is 6 decimal 5 degree per kilometer or one decimal nine eight degrees per thousand feet till 11 kilometer of height which is the height of proper pause temperature at tropopause is minus 56 decimal 5 degree and it remains constant up to a height of 20 kilometers atmosphere and flying now let us see how understanding of atmosphere will affect our flying activity with a lapse rate of 6 decimal 5 degree per kilometer it is likely that any height above 3 or 4 kilometer the ambient temperature is likely to be below zero degree centigrade and that is freezing level we will require additional oxygen above 3 kilometer or ten thousand feet of height we need pressurized cabin since air pressure and density reduces with height we will encounter most of the weather below tropopause below 11 kilometer so airliner when flying above 11 kilometer will have a smooth ride clear of clouding turbulence and weather aircraft and engine performance deteriorates with increase in height since we have lesser amount of air to produce lift and thrust respectively all airplanes will have a ceiling height above which the engine will not be able to produce required thrust to sustain flight our aircraft instruments will get affected by change in static pressure temperature density Etc and the instruments design have to cater for it in case of air conditioning or pressurization failure it is very important to descend to a lower altitude sharply so hope this video has helped you in understanding atmosphere which is the first chapter in meteorology with this we have arrived at our destination hope to see you on board again for the next flight like share subscribe and comment if you wish happy Landings foreign [Music]