Layers of the Atmosphere Meteorology

hi welcome to Aviation theory in this video we will look at the different layers of the Earth's atmosphere and their main characteristics so let's get started in previous video where we talked about the composition of the atmosphere we said that the behavior of air temperature with altitude changes throughout the atmosphere depending on certain physical phenomena and actually those changes in the temperature lapse rate allow the atmosphere to be divided into several layers each one with unique characteristics with this in mind we can divide the atmosphere vertically into five main layers and four transition layers as we can see here now although there are all these layers we have to say that civil air operations are normally conducted within the troposphere and in some cases within the lower levels of the stratosphere which as we can see are the two main layers that are found closest to the surface so with this being said let's look at brief description of each of these layers their characteristics and Associated phenomena let's start with the troposphere which is the first layer we find from the surface one of its most important characteristics is that the temperature here decreases with altitude starting from an average of 15 degrees Celsius at sea level and reaching values around minus 56 degrees in its upper levels now although the altitude of troposphere varies depending on factors such as latitude season and type of surface on average it is assumed to be around 11 kilometers or 36 000 feet so taking this into account we could say that the average temperature lapse rate within this layer is around 2 degrees per thousand feet or 6.5 degrees per thousand meters however it is important to clarify that this is an average reference value since in reality the temperature in the troposphere can sometimes remain constant with altitude or even increase slightly when there is an inversion but that will be discussed in another video now you might be wondering why does the temperature have this tendency to decrease in the troposphere well in this layer the decrease in temperature with altitude is caused by the warming of the air that is in contact with the Earth's surface for example during the day the surface heats up due to solar radiation and in turn this hot surface heats the air that is directly in contact with it this results in higher temperatures near the surface and colder temperatures at higher levels another characteristic of the troposphere is that most of the air of the entire atmosphere is concentrated in this layer and this air is kept in constant circulation due to temperature differences on the Earth's surface generating wind and convective currents so in general we can say that the air tends to be unstable in this layer now another important thing with respect to the troposphere is that it also contains most of the water vapor and aerosols of the atmosphere this combined with the fact that the air here is unstable and constantly circulating implies that most meteorological phenomena such as thunderstorms and precipitation take place in this layer so having already seen the troposphere let's move on to the first transition layer which is the tropopause this is thin layer that marks the boundary between the troposphere and the stratosphere its main characteristic is that the temperature lapse rate changes abruptly and it now tends to remain constant with altitude now as we said previously the average upper limit of the troposphere is around 11 kilometers or 36 000 feet however since in reality the extension of the troposphere varies this means that the altitude of the tropopause also varies in fact the altitude of the tropopause depends mainly on the average surface temperature of the area this way if there is low surface temperature the air above it will tend to shrink and therefore we will have lower tropopause on the other hand if there is high surface temperature the air above it will tend to expand and therefore we will have much higher tropopause with this in mind it is logical to think that near the equator where the surface temperature is high we will have much higher tropopause than at the poles where the surface temperature is much lower now although in general terms this is true the altitude of the tropopause also depends on the seasons and certain climatic phenomena present in region especially in mid-latitudes but let's go back to the main characteristic of this layer and it is that the temperature stops decreasing with altitude this difference in the temperature lapse rate between the troposphere and Stratosphere causes the tropopause to act as limit for vertical atmospheric circulation this happens because as we said earlier the air in the troposphere is unstable and tends to move both horizontally and vertically however once the air reaches the tropopause and the temperature stops decreasing it becomes more stable restricting the vertical movements and tending to flow horizontally only in simpler words we could say that the tropopause acts as kind of cap that traps water vapor aerosols and the vast majority of associated meteorological phenomena within the troposphere preventing them from extending up to the stratosphere clear example of this is the vertical development of some clouds in these images we can see how the abrupt change in the temperature lapse rate of the tropopause prevents these clouds from continuing to develop vertically into the stratosphere now taking into account all that we have seen so far we could think that the altitude of the tropopause changes gradually and continuously between the Equator and the poles as shown here however in reality things are little different since the distribution of atmospheric circulation at global scale causes the tropopause to suffer breaks in certain areas due to significant differences in the temperature of air masses this way we rather get tropopause like this one as we can see atmospheric circulation within the troposphere is divided into different cells the ones closer to the Equator are known as the Hadley cells the ones located in mid-latitudes are the feral cells and the ones over the poles are called polar cells with this distribution instead of having single tropopause we end up with individual tropical mid-latitude and polar tropoposis tropical tropopause is the highest of all reaching altitudes of around 16 kilometers or 53 000 feet and temperatures of minus 80 degrees Celsius mid-latitudes tropopause is typically found at 11 kilometers or 36 000 feet with temperatures around minus 56 degrees but we have to say that this varies depending on the season and finally polar tropopause is the lowest of all reaching altitudes of around 8 kilometers or 26 000 feet and temperatures of minus 40 degrees now these breaks in the tropopause found at approximately 30 and 60 degrees latitude are also responsible for the formation of jet streams which are narrow bands of high-speed winds specifically depending on the latitude we can find subtropical or polar jet stream in this image we cannot appreciate them very well since we are looking at the atmosphere from the side but here we can see them better from another perspective the presence of these jet streams greatly influences the performance of aircraft flying close to them as they can be used to increase ground speed and reduce flight time and fuel consumption or depending on the situation they can also be detrimental to flight performance if the aircraft flies against them in addition to this these jet strings can also cause severe clear air turbulence which we will discuss in more detail in future video now since these jet streams aren't directly related to the altitude of the tropopause aircraft flying at high altitudes must take into account the altitude of the tropopause as well as the direction and intensity of the jet streams in some cases it is even required to insert this altitude in the flight management systems of some aircraft for more accurate Cruise performance calculations so now that we have seen the most important facts about the tropopause let's move on to the stratosphere this layer is found just above the tropopause and extends up to an altitude of 50 kilometers or 160 000 feet in its lower levels temperature tends to remain constant with altitude and as we said previously this abrupt change of the temperature lapse rate restricts the vertical movement of the air which in turn prevents the formation of significant weather phenomena in this layer however we have to say that the small amounts of water vapor and aerosols present in the stratosphere combined with the low temperatures can generate clouds with little vertical development known as stratospheric clouds or nacreous clouds due to its particular and bright colors now within the stratosphere above an altitude of approximately 20 kilometers or 65 000 feet the temperature begins to increase gradually until reaching values close to zero degrees Celsius at the top of the stratosphere this temperature increase is caused by the presence of the ozone layer the ozone layer is basically concentration of ozone found in the upper two-thirds of the stratosphere but to understand how this influences the behavior of air temperature we first have to look at what is ozone ozone is molecule composed of three oxygen atoms and we have to say that the oxygen in the atmosphere is normally found in the form of molecular oxygen composed of only two oxygen atoms so what actually happens in this layer is that ultraviolet radiation from the Sun breaks the bonds of molecular oxygen releasing the atoms so that they can bind to other oxygen molecules thus forming ozone but the process does not end here the bonds of this new ozone are broken again by the ultraviolet radiation causing the cycle to repeat itself continuously this continuous process releases heat which results in an increase in air temperature in this layer of the atmosphere now it is also worth mentioning that this ozone layer absorbs much of the more energetic ultraviolet radiation from the sun which is harmful to most species living on the surface so it acts as kind of filter so continuing with the layers of the atmosphere just where the stratosphere ends we find the stratopos which is thin transition layer between the stratosphere and the mesosphere located at approximately 50 kilometers or 160 000 feet of altitude its main characteristic is that from this level the temperature stops increasing and tends to remain constant with altitude initially then right above this transition layer we find the mesosphere this layer extends from the stratopos up to an altitude of around 80 kilometers or 260 000 feet the main characteristic of the mesosphere is that the air temperature decreases again with altitude reaching values of around minus 90 degrees at the highest levels making it the coldest layer of the atmosphere we should also mention that it is in this layer where most meteorites from space normally disintegrate which are responsible for meteor showers and shooting stars now right above the mesosphere there is the mesopos which is the transition layer between the mesosphere and the thermosphere and it is found at an altitude of around 80 kilometers or 260 000 feet its main characteristic is that temperature stops decreasing and tends to remain constant initially this brings us to the next layer which is the thermosphere this layer is pretty thick since it extends from the mesopass up to an altitude of approximately 650 kilometers or 350 miles and as its name suggests the temperature here increases with altitude reaching values up to 1500 degrees Celsius however we must say that the altitude to which the thermosphere extends greatly depends on solar activity varying between 500 and 1000 kilometers now this significant increase in temperature with altitude is due to the presence of the ionosphere which is region within the thermosphere where air molecules are ionized by high energy solar radiation this ionosphere also plays very important role in the propagation of some types of radio waves because depending on their frequency some waves pass through it some are absorbed and some bounce back to the surface also this layer is characterized by the presence of auroras in regions close to the poles which are caused by the interaction of the solar wind with ionized air resulting in these exotic and beautiful colors also the thermosphere is where the International Space Station orbits the earth at about 400 kilometers or 215 miles from the surface and you might ask how can it be where the air is at such high temperature well despite its high temperature the air here has very low density which implies that heat transfer is minimal now right above the thermosphere we find the thermopus which is the transition layer between the thermosphere and the exosphere and as we said before its altitude can vary between 500 and 1000 kilometers depending on solar activity from here the temperature remains relatively constant within the exosphere so this brings us to the outer layer of the atmosphere which is the exosphere and it extends from the thermopus until it gradually disappears into space now although there is no exact value it is usually assumed that 10 000 kilometers or 5400 miles is the limit between this layer and space however despite the fact that the air here remains at constant temperature we must say that it is so thin that it simply does not behave like gas anymore and rather behaves as individual particles following ballistic trajectories so the concept of temperature here does not make much sense it is also in this layer where most satellites orbit at altitudes of 2 000 kilometers or 1100 miles on average so with this we have already talked about all the layers of the atmosphere and their characteristics however we must point out again that the troposphere and the stratosphere are the layers where almost all meteorological phenomena take place and are therefore the most important in terms of weather development hope the information presented in this video was useful if so don't forget to share like subscribe and leave comment down below it would help me lot thanks for watching and see you next time