In this episode, we're going to cover the chapter of weather and climate gateway 1. So a couple of things that we will go through today would be things like monsoon, climograph, study tips in general, as well as some of the typical question types that you will notice that are associated with this particular component of the chapter. So yeah, watch all the way to the end and hopefully this video will be useful in your revision. and most importantly if you have any questions do feel free to put them down in the comments below or you can DM me on Instagram and I'm more than willing to help.
Alright so without further ado let's start! Alright, so in this chapter of weather and climate, the overarching question is variable weather and changing climate, a continuous challenge? Alright, so in order to answer this question, we need to first have a solid foundation of what weather and climate actually means. And we're spending an entire episode on this because you need to know the different elements that contribute to weather and climate.
And most importantly, we're gonna look at some of the typical question types so you're more prepared for your examinations. And yeah, without further ado, let's start with Climograph. For Climograph itself, the very important thing is to look at the axis.
Sometimes it can change position and you don't wanna end up reading off the data that's actually not representative of what you're supposed to describe. So I've seen answers like, oh the temperatures are high at around 650 degrees Celsius. It doesn't make sense. All right but anyway, back to this, some of the common points that I tend to ask my students to take note of when they're asked to describe about the climatic characteristics of a climograph would be these six points.
So just take a quick look. First one would be mean annual temperature. Now when you are describing the mean annual temperature, of course the most important thing is to calculate it.
Sometimes they do have the mean annual temperature stated there, if not you can actually calculate it with your calculator. Just add up every single month's temperature and divide it by 12. And a very important thing to note as well is this. Now this is from a textbook and actually for core and elective geography you have this in the last chapter of a physical geography textbook and you will notice that they have tables. provided as well as the descriptive words.
So all those descriptive words are important. So in this case, let's say the mean annual temperature is above 30 degrees Celsius, so it's considered as high. Alright and then the next one we have annual temperature range. So you're going to look at the difference between the warmest and the coolest months and you look at the temperature itself. So in this case, the descriptive word would be small annual temperature range.
So use the right descriptive word and then you support it with statistics. from the figure itself. Okay so after which you can talk about the warmest and coolest months followed by in terms of rainfall, you can consider general trend.
So if you look at Singapore's rainfall pattern, you will notice that it's high throughout the entire year. So in this case, you have to say it's constantly high throughout the entire year. That's the general trend.
But for this particular climograph, you should notice that it's actually a monsoon climate. So therefore, it experiences distinct wet and dry seasons. where the wet seasons are in the middle of the year and the dry seasons are at the start and end of the year. So in this case, stated over here at a general trend.
And then after which, talk about the total annual rainfall. Basically you just add up every single bar and then you got to tell me whether it's high, moderate or low and you support with the stats and don't forget the units. All right and lastly the wettest and the driest months.
So the wettest month being July at 650 mm whereas the driest months are January and February at around 20 mm. So just make sure that whenever you write a description, support with statistics from the Clamor graph. Alright when it comes to the four factors affecting temperatures of a location, we have latitude, altitude, distance from the sea as well as cloud cover.
So what I will do is I'll go through each of them in detail and hopefully this will help you in your revision. So first of all we have latitude. Now As latitude increase, temperatures decrease in general.
That's something that's written in a textbook but what you can do is you can be a little bit more precise. In this case, as latitude increase, the mean annual temperature decreases. So I would say that out of all the factors, this is the most important because it determines the climatic zones around the world. So what do I mean by this? Basically, if you look at the countries that are nearer to the equator, they're experiencing equatorial climate and therefore the temperatures are generally higher and that is because of the latitude.
Alright so I would say that most of the climatic zones around the world, the temperature characteristics are determined by the latitude. So that's why out of all the factors this is the most important. Now in terms of the explanation I would say that for latitude itself you just have to visualize.
In this case if you have the earth and then it's tilted as X is at 23.5 degrees when the Sun rays hit the earth surface you will notice that at higher latitudes the sun's solar angle is actually smaller than that of the solar angle at lower latitudes. And because of the difference in the solar angle, you would notice that at higher latitudes, look at this part that's shaded in green, the solar energy is actually spread out over a wider area whereas for lower latitudes, the solar energy is actually concentrated over a smaller area. And since it's concentrated over a smaller area, therefore the mean annual temperatures are generally higher as compared to areas of higher latitude. So that's one explanation which is with reference to solar anger and concentration of solar energy. Alright, second explanation which is not really in the textbook but it's also good to consider would be the distance traveled by the sun rays.
So if you look at this diagram itself, you will notice at lower latitudes the distance traveled by the sun rays are generally shorter and therefore less solar energy is dissipated into space. as compared to higher latitudes and that's why you'll notice that the mean annual temperatures are generally higher at lower latitudes. Alright so next we have altitude. Alright so for altitude itself it's actually pretty straightforward.
As altitude increase, the mean annual temperature decreases. So the higher you go, the lower the temperatures. So in this case they actually did a scientific calculation and it is proven that every 1000 meters increase in altitude, the temperature is actually decreased by 6.5 degrees Celsius. So I actually tried it on the plane, it's kind of accurate so I mean you can try it out as well. Alright so next we just have to explain why is this the case but before that let me just quickly show you this diagram that you're familiar with that's in your textbook.
So what you see over here is actually the solar radiation that's received by the earth. So whatever that's received directly from the sun is actually a shortwave radiation and whatever that's reflected from the earth's surface is actually known as longwave radiation. So knowing this, alright, the explanation is pretty straightforward.
So basically in terms of altitude, the higher you go, you're further away from the surface of the ground that's heated up by the shortwave radiation and therefore temperatures are lower. So that's one. But apart from that, we also have to understand longwave radiation. So in this case, we have to recognize that the air differs in density when it's at different altitudes. So at lower altitudes, due to the pull of gravity, all the air molecules are pretty much compact together and therefore the air is denser.
And then at higher latitudes, I mean at higher altitudes, you will notice that the air is less dense. So key understanding is that dense air absorbs heat more easily as compared to less dense air and therefore at higher altitudes, air is less dense. you will notice that yeah it absorbs heat less easily so therefore the temperatures are lower.
Alright so now for distance from the sea we have basically the understanding is that the further you are from the sea which is further inland there is a difference in the temperature characteristic in this case as distance from the sea increase or further inland um basically the annual temperature range will increase as well so when we talk about annual temperature range, we're looking at the temperature throughout the entire year, right? So the warmest and the coolest months, the difference in the temperature, actually it differs between the coastal area and inland area. So what exactly is the explanation? Now, keyword over here is specific heat capacity.
Now, I won't go into the technical definition of it, but just understand that for specific heat capacity. Basically the land mass as compared to the sea, it is faster in heating up and cooling down. So what does this mean? In the summer months, the land will be warmer because it heats up faster than the sea and then during winter months, the land will be cooler because it cools down faster than the sea.
Alright so in this case, using all this understanding, we have to look at summer and winter months. Alright so since in the summer months, the land heats up faster. So if you have inland area and coastal area and undersea, what you do notice is that since the land heats up faster, the sea is now therefore cooler.
So during the summer months, The cool air from the sea will influence the coastal area's temperature and this is actually known as the maritime effect. And basically because of this, the coastal temperatures will become lower than that of the inland area during summer. Okay, so coastal area cooler, inland warmer.
Alright, so now next we have winter months. So winter months, you do notice that the land cools down faster. So in this case, you have the land.
all right and you have the sea so that's inland that's coastal and that's the sea all right so in this case if the land itself is cooler than the sea so now the sea is warmer right so the sea can actually influence the coastal temperatures through maritime effect and because of this the coastal area experiences warmer temperatures as compared to inland areas so therefore coastal area warmer inland cooler and because of summer and winter months uh difference you do notice that for coastal areas in general, they experience a smaller annual temperature range as compared to an inland area with larger annual temperature range. So I hope this is pretty straightforward. I think this formula is actually clearer as compared to the textbook.
So yeah, you can actually craft this on your own during your revision. Alright, so yeah, distance from the sea do play a role but do take note they don't just affect temperature. but they affect the annual temperature range. Okay so next and lastly out of all the four factors we have the easiest of all which is cloud cover.
Now cloud cover is something that's very straightforward because we actually because we actually experienced this in Singapore. So if you look at Singapore's temperature day and night time temperature you do notice that the difference is very minor right. So the reason is because of the cloud cover. So as cloud cover increase the annual temperature range actually decreases. So what do I mean by this?
Just compare the day and night time temperature, the warmest time of the day and the coolest time of the day and you look at the range. So what is the explanation? So just look at Singapore's case, thick cloud cover.
So during the day what we do notice is that the temperatures are not extremely high. Of course it's high because it's we're living within the equatorial region but it is not extremely high, unbearably high and the reason is simply because the thick cloud cover actually reflects the solar energy back into space. So we are receiving part of the solar energy and then at night this cloud cover, what it does is that it absorbs the heat that's reflected from the earth's surface. So we have understood from the diagram that we saw just now that this heat that's reflected from the earth's surface is actually the long wave radiation. So in this case since it absorbs the long wave radiation, it actually prevents it from escaping into the space and therefore the nighttime temperature is not extremely cold and therefore if you look at the day and nighttime temperature this will actually result in small diurnal temperature range and if you compare it to a place like a desert whereby the cloud cover is very limited due to low evaporation rates then in this case you will notice that the diurnal temperature range is extremely high because during the daytime they're receiving most of the solar energy and then at night most of all this heat are reflected back into space.
So therefore within a day you can notice that it can go up to let's say 50 degrees Celsius uh journal temperature range. Okay so I hope all these four factors are straightforward and easy to understand for you. In exams sometimes they do ask uh straightforward questions like uh they will just show you a map with an inland and coastal area and ask you to justify why they have different mean annual temperature range. That's one.
So Alternatively, what you do notice is that they can actually ask a question whereby they give you a map of two cities that are located at the same latitude and you're supposed to justify why they have different temperature characteristics. So in this case then you have to look out for clues to see if whether these two cities differ in altitude or they differ in terms of whether they're inland or coastal area. So things like that to look out for and nothing fancy, nothing difficult.
So try your best to make sure that you can address the question for this particular component. And next what we're going to do is we're going to focus on relative humidity as well as rainfall. Alright so I'm not very sure about most of you but I do understand that some students, especially core geography students, they tend to look at this particular section about relative humidity and they just scan through it without really paying attention to it.
So what I would like to say is that yes, typically for core geography students, you will notice that when it comes to relative humidity, the type of questions that can be asked are very descriptive kind of questions. So they can and give you a map showing the variation in terms of the RH values of a region. So usually it's a chloropleth map and they will ask you to just describe the distribution.
Alternatively they can give you a graph and ask you to describe the relationship between a relative humidity and temperature. So it's more of description questions rather than using it to explain but for elective geography students this is important because apart from all the description questions that core geography students might get. For elective geography student, you have GI for weather and climate and therefore you need to know the steps, the use of sling psychometer to actually collect the RH data and of course know how to present them and things like that. So just be mindful that RH is actually something that Oh yeah, by the way, RH is basically a short form of relative humidity.
And yeah, just understand that it's not something that you should just scan through or glance through but instead do pay some attention to it. Alright, so just to give you a quick summary on relative humidity so you can have a better understanding, the general relationship between temperature and relative humidity is an inverse relationship whereby as temperature increase, relative humidity will decrease or vice versa. And what exactly is relative humidity?
Now basically it's the ratio between the actual amount of water vapor in the air to the maximum amount of water vapor the air can hold and you multiply it by 100% and basically RH is presented in a percentage form. Basically the explanation is pretty straightforward. As temperature increases, the air is now warm.
So warm air basically can hold more water vapor because if you look at this horrible diagram that I drew, if you think about the air molecules of a warm air parcel, you do notice that there's a lot of space between the air molecules and therefore these spaces allows more water vapor to be held. So therefore you will notice that warm air can actually hold more water vapor since there are more spaces between the air molecules. So as temperature increase, the maximum amount of water vapor the air can hold will now increase. Right?
So since this is the case, take a look at this formula again. All right, the actual amount of water vapor in the air stays the same but because of the increase of temperature, the maximum amount of water vapor the air can hold is now increased. So if the denominator of a fraction increases basically the entire equation. decreases. Therefore as temperature increase, the RH will actually decrease.
So same idea, as temperature decreases, the relative humidity will actually increase. Now let's try to apply what we've learned so far. If you recall about the four different factors that affect temperature, particularly altitude, think about the relationship between altitude and temperature. And now think back at what we've just discussed about temperature and relative humidity. So apply all of it together.
So basically the explanation for the formation of rainfall goes to something like this. As the earth's surface is heated up, evaporation will occur. So this warm air now expands and it rises and as it rises it starts to cool down because as altitude increase temperatures decrease. So as it cools it will actually reach a point where it reaches dew point temperature.
Now this is the time where I need to explain what does dew point temperature mean. So if you recall what we've just mentioned, as temperature decreases, relative humidity increases. So what is the limit of RH?
Now in this case, temperatures can decrease until a point where RH is at 100%. So for 100% to occur, you first need to make sure that this ratio is actually one, right? So that means the actual amount of water vapor in the air is equal to the maximum amount of water vapor the air can hold.
So in this case, when RH is at 100%, basically it means that the air can no longer hold any more water vapor and therefore the air is saturated. So if the air is saturated, the temperature at which this occurs is actually known as dew point temperature. Okay, so back to our explanation. As the warm air or warm water vapor expands and rises, it rises and it cools to dew point temperature. Okay, so it reaches the point where RH is at 100%.
So what happens when the relative humidity is at 100%? Basically condensation starts to occur. Now here's something about condensation that we need to recall when we study in primary school. We understand that if you go to a very cold room, when you leave the room especially for those who wear spectacles, you'll realize there's condensation on your glass surface.
In this case, the explanation is because all this water vapor in the air actually condenses on a surface to form tiny water droplets. So same idea of how clouds are formed. You have water vapor in the air and condenses onto a surface. to form tiny water droplets and if you have a lot of tiny water droplets, basically can form a cloud itself.
So the key understanding is that there must be a condensation nuclei, a surface for the water vapor to condense on. So if you're looking at the atmosphere itself, you don't have a glass surface but what you do have are tiny little particles known as dust, right? We have dust particles in the air. So basically water vapor can actually condense onto the dust particles to form tiny water droplets which can actually help to form a cloud if sufficient amount of condensation has happened.
So if you really understand the entire process and you try to visualize, you will realize that the explanation of rain, oops, the explanation of rainfall is actually closely related to relative humidity. So please do not skip the part on relative humidity because I truly believe that it is very important for you to truly understand the formation of rainfall and it also helps you in your explanation for the next two types of rainfall that we're going to talk about which are um, Convectional rain as well as Relieve rain. Alright so what I have with me over here are the two different types of rainfall that you must learn how to explain in detail. So we have Convectional rain, something that's close to our hearts and you have Relieve rain.
And now when it comes to convectional rain, like I said, it's something that's close to our hearts because as Singaporeans, we experience convectional rain on a very frequent basis. And the reason is because we're located within the tropical region or if we want to be explicit, we're actually located at the equatorial region where the earth's surface is intensely heated up. So if The earth's surface is intensely heated up due to our low latitude. You notice that there's a lot of evaporation that's going on and because of this it facilitates the formation of cumulonimbus clouds. So this long term is something that is very important for you to know.
So do try and remember the spelling. All right so cumulonimbus clouds are basically towering clouds that can reach very high altitudes. So in this case, What you do notice is that when the clouds can no longer hold the moisture, you will deposit as short intense sudden burst of rain.
It is very high intensity but short in duration and it's something that we always see in Singapore. So that's typical of a convectional rain but we do not experience something called relief rain. So let me explain this.
to you and why is it the case that Singapore doesn't experience relief rain. Basically there are three different criteria. Number one, you need a large water body like a sea or an ocean. Number two, you need a landform such as mountain range. And number three, you need prevailing winds that are blowing across the large water body towards the mountain range.
So If you imagine this is the mountain range and this is the ocean and this is where the winds are blowing from. So as the wind blows across the water body, it can pick up the moisture and as it moves towards the mountain range, it's an obstacle. So now it has nowhere else to go but it's being forced up. So as it forces its way up, altitude increases right?
So temperature starts to decrease. So it reaches a point where it reaches dew point temperature. So if you recall what we mentioned just now at dew point temperature, condensation starts to occur and that's where clouds starts to appear. So over time when the clouds can no longer withstand the weight, what happens is that it will rain and basically it rains on the side of the mountain range that's facing the ocean and it's facing where the wind is blowing from and therefore we call this side the windward side. So basically relief rain occurs on the windward side.
of the landform or you can say the mountain range. And then as all the moisture are being deposited, the wind continues on the leeward side but this wind is now dry winds and therefore on the leeward side which is the opposite side of the mountain range, you notice that there's barely any vegetation because there's limited moisture available. Alright so nothing difficult or fancy as well so I hope this convectional rain and relief rain explanation is clear to you. and do look out for for the diagrams that are drawn in the textbook to help you better visualize the entire process. So next we're going to talk about air pressure.
So in this case when we look at air pressure, let's look at the relationship between altitude and air pressure. So what we have over here is that as altitude increase, air pressure decreases. So how do we explain this?
If we look at this as a landform itself, so basically as altitude increase, you do notice that air becomes less dense and as denser at lower altitudes because there's overlying mass exerting its force on it and therefore it results in higher pressure. Okay so as altitude increase air pressure decreases. So common question that you get every single year from student is this. You see at higher altitudes temperature decreases.
So technically speaking air pressure should be higher and yet we say that as altitude increase, air pressure is lower. So it doesn't seem to make sense, right? Now I try and understand why students think this way and I realize that it is because one of the explanations for air pressure and temperature's relationship is that as temperature increases, air pressure decreases and vice versa.
So basically as temperature increase, right, the warm air, it will start to expand and it rise and basically leaves behind a zone of low pressure. So that's something that we all can associate with. So this phenomenon, it's often observed at sea level and that's why surface winds tend to blow from a region of higher pressure to lower pressure.
However, we have to also recognize that this relationship itself is applicable only at sea level and not applicable at different altitudes. So we do not confuse them. Alright, so when you're trying to look at the relationship between altitude and air pressure, this is the main relationship.
But if you're looking at the relationship between temperature and air pressure, they are basically inverse. Alright, so do not confuse them. And yeah, I hope this actually clarifies your doubt and query because every single year I do get students asking the same question. Alright, so for land and sea breeze, there are a couple of things that I will like all of you to just pay attention to. Instead of giving you the full explanation, I guess it's straightforward when you're reading through the text.
I would say a couple of things for you to consider when you're explaining the land and sea breeze would be number one, think about the specific heat capacity. Basically like I mentioned just now, land is faster in heating up and cooling down as compared to the sea. And therefore when you're looking at land and sea breeze, we're looking at during the day, the land is basically warmer than the sea. And during the night time, The land is basically cooler than the sea because of the specific heat capacity. So because of this, it actually affects the movement of this localized winds.
So during the day, since we say that the land is warmer than the sea, you do notice that it's actually experiencing a zone of low pressure. So the sea would definitely be experiencing a zone of higher pressure because the temperatures above the sea are generally cooler. So in this case, Air moves from high to low pressure and you therefore notice that you experience sea breeze whereby the wind is actually blowing from the sea towards the land. So basically it affects the movement of the localized winds during day and night.
And next thing that I would like to address would be the wind speed. So if you look at land and sea breeze and if you compare it to monsoon winds, you do notice that differ in terms of wind speed. So why is that the case? Reason is because of the pressure gradient.
So pressure gradient refers to the difference between the high pressure and low pressure region for the air to move. So in this case, you are looking at the pressure gradient between the land and the sea. And since the temperature difference is not that drastic, since they're within the same localized area, then in this case you will notice that the pressure gradient is much gentler and therefore those wind speeds are generally slower. And if you compare it to monsoons, it's completely different.
So if you try and understand about monsoon, this time around we're looking at the seasonal differences between the northern and the southern hemisphere. Since monsoon winds are generated due to the difference in temperatures of the different hemispheres they're experiencing different seasons, the temperature difference will be huge, right? So in this case, the pressure gradient would definitely be way higher and therefore we would say that it has a steeper pressure gradient which results in faster moving winds as compared to land and sea breeze. So if you actually encounter a question that requires you to compare between monsoon as well as land and sea breeze, this is something for you to consider.
Basically the wind speed differs. Okay now when it comes to studying of monsoons, I tend to notice this from my students that they actually memorize the entire chunk of explanation from the textbook. So they study in this way, southwest monsoons. So southwest monsoons takes place between June and September. So when I first hear students mention their explanation with southwest monsoon or northeast monsoon, I would know that they actually memorize it rather than...
studying in a very logical manner. So I'm going to teach you how to study in a logical manner and here is what I have the entire thought process. So now whenever you are required to explain about monsoon, try and adopt this. So first of all, understand that monsoons are generated due to seasonal differences between the hemisphere. So identify the season of the hemisphere by looking at the time of the year.
So in this case, if it happens between June to September, then we understand that in the northern hemisphere it is actually summer and southern hemisphere is actually is experiencing winter. So the season will actually determine the temperatures right. So if northern hemisphere is summer that means temperatures are generally higher than that of southern hemisphere. So the temperature would then affect the air pressure.
So northern hemisphere, warmer and therefore lower air pressure because now all the air molecules are rising and it leaves behind a zone of lower pressure. Whereas in the southern hemisphere, it's cooler. It's actually experiencing winter. So all the air molecules are actually sinking and as it sinks, it exerts pressure onto the ground and therefore it creates a zone of higher pressure. So since we know the air pressure, next we would definitely know the wind direction.
So is it blowing from north to south or is it blowing from southern hemisphere up to the northern hemisphere? Since it's higher to lower pressure, of course it's blowing from the southern hemisphere to the northern hemisphere from an area of higher pressure experiencing winter to an area of lower pressure experiencing summer. So we conclude June to September the winds are generally moving northwards. So now as we move on we got to think about Coriolis effect. Basically what Coriolis effect does is that it actually deflects the wind.
So we understand that the winds are generally deflected to its left in the southern hemisphere and to its right in the northern hemisphere. So in this case you follow how the winds are moving. So we have the earth right if this is the southern and this is the northern hemisphere we know that in general it should move in this direction but due to the spinning of the earth which results in Coriolis effect basically in the southern hemisphere the winds are deflected to its left.
However once it crosses the equator it deflects to its right. All right so in this case you Therefore, you notice that between June to September, you get winds that are blowing from north, south, east, west, from the southwest towards the northeast, right? And therefore, we call this the southwest monsoon in June to September.
Let's move on. If the question only requires you to talk about monsoon winds, the direction of it, you just end off here. But if the question actually asks you to explain about why certain countries experience high amounts of rainfall during certain times of the year and obviously the country experiences monsoon, then you have to mention that it picks up the moisture as it blows across large water bodies.
So if you want to explain about why certain parts of India, especially the eastern coast, experience high amounts of rainfall during June to September, then in this case you have to mention that the wind blows across the Indian Ocean or you can even be more specific it blows across the Bay of Bengal and it picks up the moisture and deposits onto the coastal area therefore resulting in high amounts of rainfall. Okay so yeah and something that you should also notice is that every time June to September countries like Bangladesh or certain parts of India will experience severe flooding due to the monsoon rains. So that's basically the explanation.
So a direct opposite will be true from October to February where you notice that everything we've mentioned is the reverse. Alright so in this time around from October to February start and end of the year so therefore the northern hemisphere is experiencing winter whereas the southern hemisphere is experiencing summer so it's a row reversal so now this time around the winds are blowing southwards. So go through this whole thought process to help you come up with the explanation. and you realize that a thought process like this is easy because you just need to remember certain keywords season temperature air pressure wind direction so it's much better than you trying to memorize the entire chunk of information from a textbook okay so i hope this is useful and you will notice that for gateway one the last part is actually talking about all the different uh climatic types three main types in general so we have covered equatorial climate which is basically uh like singapore we have high mean annual temperatures as well as high total amount of annual rainfall. And then you have monsoon climatic types which means that they have very distinct wet and dry seasons and they have relatively high temperatures.
And the last one is marine west coast. Basically for this type they are located at higher latitudes and therefore their climatic conditions are very different. They have four seasons so they have a larger annual temperature range and then you have constant amounts of rainfall as well.
So pretty interesting for this particular climatic type for you to better understand the differences between tropical equatorial region, monsoon region with areas that are located at higher latitudes. Okay, so I hope this video is useful in helping you understand Gateway 1 in detail. So what will be coming up would be Gateways 2 and 3. So do look out for that and yeah, all the best for your revision and we'll see each other again. Bye!