1 00:00:00,300 --> 00:00:17,100 Elements of weather. We know that temperature, atmospheric pressure, winds, humidity, clouds, and precipitation are the elements of weather. 2 00:00:18,379 --> 00:00:20,899 Let us know more about them. 3 00:00:23,309 --> 00:00:23,929 Temperature. 4 00:00:23,929 --> 00:00:33,130 The degree of heat of an object or the degree of heat at a place is known as temperature. 5 00:00:34,070 --> 00:00:43,210 Thus, the quantity by which you can compare the hotness or coldness of bodies is called temperature. 6 00:00:44,869 --> 00:00:48,009 Temperature is measured in degree Celsius. 7 00:00:49,530 --> 00:00:52,350 Celsius is also called centigrade. 8 00:00:52,350 --> 00:00:58,960 Temperature is measured by an instrument called the thermometer. 9 00:01:00,600 --> 00:01:05,120 Temperature on a Celsius scale is read in degree Celsius. 10 00:01:06,200 --> 00:01:12,079 Following are the factors on which atmospheric temperature of a place depends. 11 00:01:12,959 --> 00:01:16,620 a. Nearness of the place to the Earth's surface. 12 00:01:17,579 --> 00:01:20,379 b. Latitude of the place. 13 00:01:21,200 --> 00:01:23,900 c. Altitude of the place. 14 00:01:23,980 --> 00:01:28,540 d. Height of the place above sea level 15 00:01:28,540 --> 00:01:32,840 e. Distance of the place from the sea 16 00:01:32,840 --> 00:01:39,000 The earth's surface gets heated due to the heat of the sun. 17 00:01:39,840 --> 00:01:44,000 Hence, the air near its surface gets heated first. 18 00:01:44,420 --> 00:01:48,859 Then, layer by layer, the air becomes warm. 19 00:01:49,799 --> 00:01:53,799 Hence, the temperature near the earth's surface is higher. 20 00:01:53,980 --> 00:01:58,599 and decreases as we go further away from the earth. 21 00:02:01,530 --> 00:02:02,810 Atmospheric Pressure 22 00:02:02,810 --> 00:02:08,150 You might have enjoyed boating with your parents several times. 23 00:02:09,050 --> 00:02:12,090 Have you observed that when you sit on a boat, 24 00:02:12,949 --> 00:02:15,849 its one side is pressed down sideways? 25 00:02:17,110 --> 00:02:20,909 Actually, it happens due to the weight of your body, 26 00:02:21,349 --> 00:02:24,250 which you exert on the side of the boat. 27 00:02:24,250 --> 00:02:30,830 You must have read in your science textbook that any object has weight. 28 00:02:32,229 --> 00:02:34,509 Air also has weight. 29 00:02:35,750 --> 00:02:44,569 It is a highly compressible mixture of gases which applies pressure on the Earth's surface by exerting its weight. 30 00:02:44,569 --> 00:02:49,189 Thus, atmospheric pressure is defined as 31 00:02:49,189 --> 00:02:56,629 the pressure exerted by the vertical column of air lying above a particular area. 32 00:02:57,849 --> 00:03:01,689 Atmospheric pressure is measured by using a barometer. 33 00:03:01,889 --> 00:03:11,189 The unit of measurement of atmospheric pressure is millibar, written as mb. 34 00:03:11,189 --> 00:03:16,490 The variation in the atmospheric pressure from one place to another 35 00:03:16,490 --> 00:03:18,949 affects all weather changes. 36 00:03:20,389 --> 00:03:24,689 For example, the rising pressure makes the weather fine 37 00:03:24,689 --> 00:03:30,930 while decreasing air pressure makes the weather cloudy and rainy. 38 00:03:31,370 --> 00:03:38,729 All these variations or changes in atmospheric pressure depend upon some factors. 39 00:03:38,729 --> 00:03:42,289 Let us know about these factors. 40 00:03:43,530 --> 00:03:48,830 Following are the factors on which atmospheric pressure of a place depends. 41 00:03:49,909 --> 00:03:51,469 1. Temperature 42 00:03:51,469 --> 00:03:53,789 2. Altitude 43 00:03:53,789 --> 00:03:57,210 3. Density of the air 44 00:03:57,210 --> 00:04:02,150 Let us discuss these factors one by one. 45 00:04:04,069 --> 00:04:05,770 1. Temperature 46 00:04:05,770 --> 00:04:12,550 There is an inverse relationship between air pressure and temperature. 47 00:04:13,569 --> 00:04:20,810 When the temperature of a place rises, the volume of the surrounding air starts to increase. 48 00:04:21,949 --> 00:04:24,930 This makes the air less dense. 49 00:04:26,209 --> 00:04:32,589 Due to the lower density, the air exerts a lesser pressure on the surface. 50 00:04:32,589 --> 00:04:37,509 When the temperature falls, the air becomes denser. 51 00:04:38,089 --> 00:04:41,930 That is, the weight of air increases. 52 00:04:43,129 --> 00:04:49,750 Due to the higher density, the column of air exerts a greater pressure on the surface. 53 00:04:50,509 --> 00:04:57,610 So, we can say that the hotter the place, the lesser the atmospheric pressure 54 00:04:57,610 --> 00:05:03,410 and the colder the place, the higher the atmospheric pressure. 55 00:05:05,329 --> 00:05:06,930 2. Altitude 56 00:05:06,930 --> 00:05:13,189 Air is compressible and it concentrates near the Earth's surface. 57 00:05:14,069 --> 00:05:23,389 The upper layers of the atmosphere exerts more pressure on the lower layers on the surface of the Earth, 58 00:05:24,470 --> 00:05:27,110 thus increasing the density of air. 59 00:05:27,610 --> 00:05:33,329 Therefore, the atmospheric pressure near the Earth's surface is greater. 60 00:05:34,230 --> 00:05:40,870 As we move upwards from the Earth's surface, the air becomes lighter, 61 00:05:41,709 --> 00:05:45,569 which results in a low atmospheric pressure condition. 62 00:05:46,889 --> 00:05:53,550 This clearly indicates that the rate of atmospheric pressure varies inversely with height. 63 00:05:54,829 --> 00:05:57,009 3. Density of air 64 00:05:57,009 --> 00:06:02,129 The dense air is heavier than the thin air. 65 00:06:02,930 --> 00:06:07,350 Therefore, it exerts more pressure on the Earth's surface, 66 00:06:08,009 --> 00:06:13,769 while thin air exerts less pressure on the surface. 67 00:06:14,509 --> 00:06:19,529 The dense air is generally found near the surface of the Earth, 68 00:06:20,110 --> 00:06:22,850 especially at the ocean's surface. 69 00:06:22,850 --> 00:06:29,829 That is why we find more atmospheric pressure at the sea level 70 00:06:29,829 --> 00:06:33,930 than at the top of hills or mountains. 71 00:06:35,550 --> 00:06:36,629 Wind 72 00:06:36,629 --> 00:06:40,069 Air always remains in motion. 73 00:06:40,949 --> 00:06:46,329 Sometimes it moves horizontally and sometimes vertically. 74 00:06:47,310 --> 00:06:51,269 The horizontal movement of air is called wind. 75 00:06:51,269 --> 00:06:59,389 Air moves horizontally from an area of high pressure to an area of low pressure. 76 00:07:00,529 --> 00:07:10,910 Thus, the air moving in a direction which is essentially parallel, horizontal, with the Earth's surface is called wind. 77 00:07:11,350 --> 00:07:17,050 The speed of wind is measured in kilometers per hour. 78 00:07:17,050 --> 00:07:25,069 The instrument used to measure the speed of wind is called an anemometer. 79 00:07:27,480 --> 00:07:28,060 Humidity 80 00:07:28,060 --> 00:07:33,680 We know that water vapor is always present in the atmosphere. 81 00:07:34,839 --> 00:07:38,560 The amount of this water vapor is called humidity. 82 00:07:39,439 --> 00:07:47,560 The moistness or the dryness of the air depends upon the atmospheric humidity. 83 00:07:48,560 --> 00:08:03,560 Weather is said to be humid when the water vapour content in air is higher and it is dry weather when the water vapour content in the air is lower. 84 00:08:05,000 --> 00:08:09,319 Rainfall depends on the level of atmospheric humidity. 85 00:08:09,319 --> 00:08:18,920 Rainfall is high in areas like Mumbai because it is near the Arabian Sea. 86 00:08:18,920 --> 00:08:24,740 It is low in areas which are far away from water bodies. 87 00:08:26,660 --> 00:08:33,600 The instrument used to measure humidity of a place is a dry and wet bulb thermometer. 88 00:08:34,539 --> 00:08:37,059 Humidity is given in percentage. 89 00:08:37,059 --> 00:08:48,360 clouds water from the water bodies like lakes rivers seas and oceans evaporates due to the 90 00:08:48,360 --> 00:08:59,759 sun's rays and form vapor this vapor mixes with the atmosphere it rises higher and higher along 91 00:08:59,759 --> 00:09:00,820 with the air. 92 00:09:02,220 --> 00:09:03,620 Due to the low temperature 93 00:09:03,620 --> 00:09:06,080 at higher altitudes, 94 00:09:06,580 --> 00:09:07,460 the water vapor 95 00:09:07,460 --> 00:09:09,919 gets converted into water 96 00:09:09,919 --> 00:09:11,980 droplets around 97 00:09:11,980 --> 00:09:13,220 dust particles. 98 00:09:14,379 --> 00:09:16,080 This process is known 99 00:09:16,080 --> 00:09:17,559 as condensation. 100 00:09:18,879 --> 00:09:19,759 These water 101 00:09:19,759 --> 00:09:21,919 particles float in the 102 00:09:21,919 --> 00:09:24,139 atmosphere. A collection 103 00:09:24,139 --> 00:09:26,080 of such minute water 104 00:09:26,080 --> 00:09:28,220 particles is known as 105 00:09:28,220 --> 00:09:29,100 a cloud. 106 00:09:31,580 --> 00:09:44,299 Precipitation. The wind blows the clouds from one place to another. We get rainfall from the clouds. This is called precipitation.