hey everyone now that we're through winds and pressure and all that good stuff it's time to get into the moisture part of class so the first thing I want to do is go over the hydrologic cycle and its main components with you all so you've probably seen some kind of diagram like this in a previous class or at the K12 levels even before college and I want you to make sure that by the time we're through this unit and the rest of the water stuff in unit 2 that you're very comfortable talking about different components of this cycle so we'll talk about condensation evaporation precipitation water moving in the atmosphere fog Dew and then we'll talk a little bit about other things in terms of how water winds up in rivers and how it gets into the ground we'll talk about some very basics of that not too much detail because that's more for outside of weather and climate so one thing I want to highlight is when we talk about the atmosphere itself we're talking about water that's not up there very long and a small component of the overall total of water on the planet now depending on what source you look at this one says that ocean water is 96 and a half% others say 97% but the total amount of water in the oceans essentially makes everything else look really small because of how much water is there however the water that we're focusing on that I highlighted down here by the atmosphere is really important because that helps redistribute moisture around the planet now it may only be up there for a week maybe two weeks depending on how long it's out over the open ocean or different things but that small percentage of water is going to be what we focus on mainly in weather and climate so just another way to visualize it and every textbook or Source has a slightly different number so the last one I just showed you had 96.5% ocean water this one's 97.2 but again I want to highlight this part of the atmosphere and what a small component it makes up because we're going from fresh water which is only 2.8% down to this part and a lot of that is locked up in ice and Glaciers and of that small subset that's available there's a little bit in the atmosphere a little bit in rivers some in soils and then talk about freshwater lakes and so water on this planet even though it's in abundance in the oceans freshwat is not all that abundant by comparison and so how it moves through the atmosphere and gets redistributed is important for where human beings live and how we take advantage of the water cycle so the first form of water that we talk about in terms of the hydrologic cycle is precipitation without precipitation any form of liquid or solid water falling on the planet we don't have the ability to live as human beings in different areas and the biosphere would look very different so precipitation is any form of water liquid or solid falling from the atmosphere now to get that liquid or solid to actually fall we actually have to change water's States if water just stayed as a liquid or a solid at the surface of the planet it wouldn't move and get redistributed but that takes energy to actually move water from one state to another so I want to focus just on this example and make sure that you pay attention to this diagram because the amount of energy associated with how we change water States influences much of what we're going to talk about the rest of class including how we fuel severe storms and things of that nature so in this sample problem here we could use any amount of water or ice you know to go through this example but I'm going to focus on some things that I'm going to Circle and highlight that I want you to know but in this sample problem we're saying how much energy essentially is it taking to move 10 gram of ice from min-2 cels to 120 cels meaning we're going to go through the different stages from solid to liquid and liquid to gas so to figure this out we're going to figure out the number of calories that it takes the amount of energy that it takes okay we're going to take the number of grams of ice times the specific heat times the change in temperature now what I want you to realize here is how much energy it's taking to change States so we're going to focus mainly on the specific heat component so for example to heat up ice it takes only a half a calorie per gram okay now at the next state we're at 0 degrees Celsius so what is happening here what is happening at 0 degrees Celsius why isn't there a temperature change right here even though we're applying energy if you said 0 deg is the freezing point and that's where we're changing and changing the molecular bonds in water then that's accurate you're now going from solid ice to Melting that ice into a liquid so at those exact points where you're changing that Bond structure of water there's not a temperature change but once you change it to liquid then you can begin to heat it up again and we go on that phase of liquid all the way up until you get to 100 de Celsius which is the boiling point where we begin to evaporate so that stage of just heating up liquid water takes 1 calorie per gram okay notice here that it takes 80 calories per gram to change the molecular structure of water and go from a solid to a liquid we then reach that boiling point and I really want to highlight this point because right here is where that evaporation is occurring so if if you notice that Flatline point where we're changing from a liquid to a gas now that's evaporation that's what I want to focus on because look how much energy it takes relative to the other stages okay 590 calories per gram to convert water from a liquid to a gas and then again once it's a gas right it just takes only a half a calorie per gram to continue to heat it up and to get those molecules moving faster as a gas Okay so focus on how much energy it takes to drive evaporation it's a lot of energy on this planet that we get from the Sun to move water from the liquid state at the surface to the atmosphere so I just showed you how much energy it takes to go through the different stages and to change phases of water evaporation itself is that movement of water from saturated surfaces into a gaseous State and so in this case we're moving water molecules away from the surface and into the atmosphere and that is going to help us fuel our systems for weather and climate note here I said it takes a lot of energy look at this it takes 80% of the radiation that's absorbed at Earth's surface 80% of that goes to evaporating water because it's such an energy intensive process now if you reverse this process and you cool air down or you cool different objects down on which water is located you can move water from a gaseous State back to liquid that is how clouds and other things are formed in the atmosphere it takes energy to hold all of that water and gas form right I just showed you on that chart or that graph how much energy it takes how much is required to move water from liquid to gas so you need energy to maintain that water in gas or vapor form so if temperatures cool down there's not enough energy in that air to hold it in gas form and it therefore goes back from gas to liquid and then condenses out so if this happens in the atmosphere it condenses in the clouds if it happens at the ground it condenses into do or things like that and then if it's freezing then we talk about it going to ice crystals and things like that so what's important to note here is that all that energy that was stored in that vapor form of water that gas form of water when it goes back through the process of condensation that energy is then released back to the surrounding atmosphere so that heats the atmosphere and that helps to provide the energy to fuel things like thunderstorms okay that also means our air pressure drops and so it allows even more water vapor to rise into those low pressure systems that's an example of a positive feedback loop right air pressure dropping leads to more Water Rising which leads to further air pressure drops which leads to even more water being able to rise into the atmosphere so here is that process in place so we have condensation if we're going from gas to liquid or we call it deposition if we're going from gas right to a solid that occurs if the temperature is below 32° F or 0° C it goes right into ice crystals okay so what happens is heating allows that moisture to rise and turn into a vapor with that energy as it rises it gets colder and condenses okay that condensation allows for that energy to release and for the air pressure to drop even further which in turn allows even more moisture to rise and leads to wind and pressure gradients like we talked about earlier in class as that pressure continues to drop so when we talk about the water cycle how we move that water is important and how we move that water is through the combined processes of evaporation which we already mentioned and transpiration so evaporation we already talked about that's going to be related to the net movement of water from saturated areas into the unsaturated atmosphere and it depends on where you're at so the conditions the temperature the existing humidity in the air the wind all of those things matter related to evaporation transpiration we combine with evaporation when we talk about how water is moving from the surfaces of the planet into the atmosphere but it's driven by photosynthesis transpiration is driven by photosynthesis but we combine the two evaporation and transpiration into this one term ET or evapor transpiration because both things are moving water from the surface into the atmosphere so plants running through photosynthesis are going to take in sunlight and carbon dioxide and water and then some of that water is going to get transpired it's going to go through the trees and then it's going to evaporate off of the leaves of trees after it's gone after they've gone through this process of transpiration part of photosynthesis this is the same reason why human beings go through this process evaporation of water and movement of energy through that water into the atmosphere helps trees cool down and our evaporation of sweat helps us cool down because it's removing that energy associated with that liquid to gas change from us which helps us cool down so in some areas it can feel really hot because there's lots of transpiration occurring from different crops I mentioned this when we talked about heat index just briefly earlier in class and we'll talk about it more in the future so in some of these areas where there's not enough water sometimes you have to provide irrigation to crops because they use so much water and sometimes there's not enough rainfall to allow them to continue going through photosynthesis we can also see how important transpiration is and the moisture is in different areas and just how much moisture is produced for example looking here in the eastern part of the United States at the Blue Ridge Mountains you see this hazy this in this photo because there's different chemicals being secreted in things in these areas and the water is condensing around those different particulates at the higher elevations in the Blue Ridge Mountains where it's colder the moisture can't be held as a gas for very long and so you get cond condensation into liquid droplets around the particulates that they can hang on to so this can be really important or more clearly transpiration can be very important in certain areas around the world now evaporation is the dominant thing that gets water up into the atmosphere but there's certain climates like in the Amazon where there's so much vegetation and so many trees that they're putting a ton of water up into the atmosphere so half of the water that falls in the Amazon itself is coming from the trees and transpiration in the jungle itself that's not like that everywhere some places have much less vegetation and rely on evaporating from the oceans and water getting transported to those areas to get their moisture and precipitation so what variables influence the different ET rates or vacat transpiration rates in our different areas well first thing you have to have water that's actually available to move it into the atmosphere so I just said that in the Amazon it's 50 half comes from other water sources half comes from the jungle itself through transpiration well it's different on the planet as a whole on the planet as a whole only about 15% comes from the land and 85% comes from those big water reservoirs in the oceans and we know how important this can be in different areas when we think about the monsoons when winds are blowing from the land out there's almost no precipitation when winds are blowing from the ocean in there's a ton of precipitation in those areas so water moving from the oceans is hugely important for how it gets distributed around the globe and goes through our atmosphere and again just to review what we've already talked about with the monsoons and how the season sits sets up differently during the summer versus the winter the other important factor Beyond availability is temperature again it takes a lot of energy to move water from one state to another and so high temperatures result in more energy being available and therefore high temperatures equal more evaporation so you would expect much more evapor transpiration to occur in the tropics and those areas that are getting a lot more energy from the Sun to drive this process compared to the poles there's a lot less of appapo transpiration as you get to high latitudes or toward 90° and a lot more when you get closer toward the equator again provided that water is actually available humidity also matters if the air is already saturated with humidity you cannot get as much evaporation to occur because there's already molecules taking up space given how much the air can hold at a certain temperature okay and so if there's more water molecules in there it's harder to evaporate things so more saturated air can actually lower the humidity or can actually lower the evaporation into it because the humidity is already so high wind also matters so one way even if the air is somewhat humid one way you can actually evaporate more water into the atmosphere is by having wind that helps to clear out water molecules from over surfaces where evaporation could occur so once the wind blows it clears out some of the molecules and then more molecules can rise into that air and take their place and so wind can help a great deal we know this actually from practical examples I told you I'd give you some applied examples on how they relate to larger scale weather and climate processes so the oldfashioned way of hanging clothes to line dry especially on days where you knew it was going to be sunny that sun can help evaporate off the water but the wind and the breeze blowing through those clothes could cause them to dry even faster it's the same reason why you have your dryers that actually move the clothes around to get that air flow across them to allow more water water molecules to evaporate more quickly if you use a hair dryer it's the same basic principle the air flow helps to move the water molecules and higher the temperature you put that blow dryer on the faster you'll be able to drive that evaporative process and dry your hair because there's extra energy plus there's actual air flow to move the molecules away from the saturated areas in your hair car dryers car washes same basic principle air flow across your car helps to drive the evaporative process more quickly so let's talk for a minute about the difference between types of aapo transpiration there's two different components that we break aapo transpiration down to now the first one is called potential evapo transpiration or you may see me just abbreviate that P this is a function of what could occur if water was completely unlimited now water isn't completely unlimited everywhere so we'll talk about a different kind of evapo transpiration in a second but I want you to realize that potential evapo transpiration tells you what could occur if you had unlimited water given just the temperature humidity and wind conditions of a given area so for example the pet in this area of the Rio Grand is the same across the landscape what could occur is the same because the temperature humidity and wind conditions across this landscape are the same however actual evapo transpiration is likely to be much higher off of the body of water so what's actually occurring matters okay the actual amount of vapo transporation is what does occur in a given area given the temperature humidity wi conditions and the water actually being available okay so pet would be high across this whole landscape AET would only be high coming off of this Lake on the Rio Grand River okay now when we get to climates later on this is going to be really really important because climates when we consider deserts are actually to be classified by comparing pet or what could leave a system compared to what actually falls is precipitation in that region and if what could leave the system or the peak P exceeds what comes into that system you will have water deficits so let me say that one more time if the pet is greater than the amount of water that falls in a given area there will be a water deficit meaning more water is leaving the system than what is coming in so let's consider a landscape like Las Vegas and what this means this is Lake me just outside of Las Vegas so this is created by Hoover Dam on the Colorado River over time the lake is declining and it's going down in terms of its total capacity because there's less snow melts in the Rockies but also because of use plus evaporation on our Big River Basin dams and reservoirs out west so in this landscape pet again is going to be similar across the whole landscape because the temperature and the humidity and the wind speed is going to be similar but the actual a what's going away from Lake me into the atmosphere is going to be high because there's actually water available so this lake is essentially functioning as an unlimited supply of water that allows actual evapo transpiration R rates to meet what potential evapo transpiration is so how do we measure this how do scientists actually figure this out well one way is to look at evaporation pans put a certain amount of water out measure the temperature measure the humidity of the air look look at the wind speeds like you can see on the right hand of this diagram over here okay and this essentially mimics what an unlimited supply of water is so this tells you what the maximum potential of Appo transporation would be by watching how the level of this changes over time with the changing weather and climate conditions of the area we can also measure it by measuring the amount of water in soil so there's agricultural areas where they do these types of experiment and they actually dig out a soil column and put instruments in to weigh that soil column and by understanding how much the we changes based on water coming in and going out that helps tell how much actual vapo transporation is happening across these types of Landscapes so I want to focus on potential of APPA transpiration this tells you what could happen if there was unlimited water note here the potential of Appa transer ation is much greater in the tropics because there's a lot more energy around but I also want you to note things like the potential of app transpiration is really high in places like the Sahara Desert okay but remember this is just talking about potential or what could happen remember there's very little water sources in the Sahara so actual evapo transpiration is much lower but that helps explain water deficits what could come into the Sahara Desert is likely to leave almost immediately which creates a big deficit in desert climate AET or actual vapa transpiration patterns are different so if we look at the United States and North America here you can see that actual evapo transpiration rates are much higher in the southeastern United States this is because water has to actually be available and the water bodies that are adjacent to some of these areas like the Gulf of Mexico or the Gulf Stream coming through the part of the Atlantic that interacts with the southeastern United States those areas all have enough energy to move water into the atmosphere and therefore there's enough water to be evaporated off the land after it falls as precipitation and there's a lot more vegetation in these areas you'll notice in the western half of the United States the only places that show up as having higher evapo transpiration are mountain ranges and areas like that where there's elevation effects resulting in precipitation so talking about precipitation as a whole in the United States which is helping to result in these patterns there's something called the 100th Meridian which is the line for 100° west longitude and that line historically was where it was about 20 in of rain that was essentially the equilibrium line to tell us that east of that line we were generally going going to have a balance or a surplus in terms of water coming in and going out west of that line except for the mountain ranges again west of that line we are largely going to have deficits more water could leave the system more quickly than what could fall or what was falling is rain now we'll talk more as we get to climate change later in class how this is actually shifting further and further east and the PLS and the central part of the US is actually drying out so we can kind of see that here and we'll talk about it more later on in class but this blue line that runs through here is now approximately where the balance is so it's already shifted East with climate change but we're not going to focus on that here because that's not part of this unit yet okay so we can see in the southeastern United States this is looking at precipitation compared to pet so are we getting enough water right to meet the demand of what is going to be evaporated and transpired from that system the air areas that are this whitish cream color are the areas in Balance the green areas and if you're color blind I'm sorry they put this map together this way but again east of this line is where we're seeing all those green colors and a surplus west of that line on this side is where we're seeing mostly deficits except for the mountain ranges that are outlined in blute so this relates to water budgets and again surpluses and deficits we see if we're going to have more water coming in than what's going out then we can have rivers and lakes and things that exist for a longer period of time if more water is leaving the system than what we're getting our Rivers can eventually run dry and our reservoirs can start to decline because there's more water leaving the system than what's coming in if we have enough water falling on the landscape some of it can work its way down into the ground and we can use that as drinking water okay and if there's excess water on the landscape again it winds up in water bodies at the surface like rivers and lakes so to get groundwater flow and to have aquifers that exist below our feet you have to have more water coming in and more infiltration into the soil than what's leaving through evapotranspirative processes and so that matters especially in a place like Southeast Texas because there's quite a few communities in Texas that get their water from groundwater in fact some of the water in Huntsville comes from the ground and a lot of the water historically in Harris County in Montgomery County has come from Wells that are pulling groundwater out and for things like this to exist like the San jento River or the triny river and things we talk about with flooding later on you have to have more water coming into the system than what's leaving and again that's really important for drinking water in human beings because in order to have reservoirs and stuff like that like lake conro Lake Houston Lake Livingston things that help us provide water to communities in Southeast Texas you have to have a consistent supply of water coming in and if you were to have deficits for too long levels in those reservoirs would begin to fall and that could pose problems for future water security so I want to focus on this in terms of Applied examples for different locations and how the water cycle and water budgets relate to different communities in different climates the most similar one to our area in Southeast Texas that I want you to be familiar with is this one right here in Kingsport Tennessee you see that through much of the year there's a surplus those blue areas on the diagram there's more precipitation coming in than what could leave through vapo transpiration however you do get small deficits with the average climate conditions over the summer so this is also why in Southeast Texas you'll often see people in June July and August that may be watering their lawns or things like that you may need to provide a little bit of water to keep the vegetation alive because they might not be getting enough to meet that evapor transport of demand in Ottawa Canada things are a little bit different okay but pretty similar overall even though the temperatures are much cooler the one I really want to focus on to compare to Kingsport Tennessee which is similar to East Texas is Phoenix Arizona Now Phoenix Arizona is out there in the Sonoran Desert and so it's very very dry the water balance is way off because there's a lot more of Appo transpiration that could occur than precipitation and so there's a lot more water that goes away and so you can't sustain surface water in those areas as long if you have these prolonged conditions so I want you to remember the components of the water cycle as we work our way through different things and move through the end of unit two with water in the atmosphere and how it interacts with different things and I want you to remember these water balance examples and how potential evapo transpiration actual evapo transpiration and precipitation matter when we look at different climates and compare them