SESE 104 Meteorology Lecture Notes PDF

BSEd (Sci) SESE 104: Meteorology Course Content (Lecture Notes) E. Air Masses, Fronts, Cyclones, Storms, and Typhoons 1. Air Masses and Fronts An air mass is a huge body of air, so large that it often stretches for several thousand miles....

BSEd (Sci) SESE 104: Meteorology Course Content (Lecture Notes) E. Air Masses, Fronts, Cyclones, Storms, and Typhoons 1. Air Masses and Fronts An air mass is a huge body of air, so large that it often stretches for several thousand miles. Air masses generally have similar temperature and moisture properties throughout. Air masses are determined by their source region. The area over which an air mass gets its characteristic properties of temperature and moisture is called its source region. By temperature, air masses can be cold or warm air, depending on where they form. While humidity, air masses can be dry or moist, also influenced by their source region. Table 1. Source Regions Source Region Characteristics Polar air mass (P) form over polar ice caps and are very cold Tropical air mass (T) form in lower latitudes and are usually warm occur in land masses and usually contain less Continental air mass (c) moisture, meaning they tend to be dry originate over a large body of water and are also Maritime air mass (m) known as oceanic air masses because they form over water, they are moist Type of Air Masses The four major types of air masses are: a. Continental Polar (cP). These air masses are cold and dry, as they form over cold, dry land in the polar regions. They can bring cold, dry weather with clear skies. b. Continental Tropical (cT). These air masses are hot and dry as they form over hot desert regions. They can bring heat waves and drought conditions. c. Maritime Polar (mP). These air masses are cold and humid, as they form over cold ocean waters in the polar regions. They can bring cold, damp weather with fog and drizzle. d. Maritime Tropical (mT). These air masses are warm and humid as they form over warm ocean waters in the tropics. When they move over land, they can bring heavy rainfall and high humidity. Weather Fronts The influence of different air masses causes day-to-day changes in the weather as they pass over the land. The front is the boundary where these different air masses meet. Fonts can either be Warm, Cold, Occluded or Stationary. Types of Weather Fronts Fronts can either be Warm, Cold, Occluded or Stationary. a. Cold front. Symbolized on a weather map as a line with triangles. Cold fronts are often colored blue. The presence of a cold front means that cold air is advancing and pushing underneath warmer air. This is because the cold air is 'heavier' or denser than the warm air. Cold air is thus replacing warm air at the surface. The tips of the 'triangles' indicate the direction of movement of the cold air. b. Warm front. Symbolized on a weather map as a line with semicircles. The semicircles can be thought of as half-suns. Warm fronts are often colored red. The presence of a warm front means that warm air is advancing and rising over cold air. This is because warm air is 'lighter' or less dense than cold air. Warm air is replacing cooler air at the surface. The edges of the 'suns' indicate the direction of movement of the warm air. 30  BSEd (Sci) SESE 104: Meteorology Course Content (Lecture Notes) c. Occluded front. Symbolized on a weather map as a line with both semicircles and triangles. They are often colored purple. These are slightly more complex than cold or warm fronts. The word occluded means 'hidden', and an occlusion occurs when the cold front 'catches up' with the warm front. The warm air is then lifted from the surface and, therefore, hidden. An occlusion can be thought of as having the characteristics of both warm and cold fronts. d. Stationary front. The stationary front is a type of weather front that does not move or moves very slowly. It is symbolized on a weather map as a line with alternating triangles and semicircles pointing in opposite directions. Stationary fronts are often colored alternating red and blue. Stationary fronts can cause periods of prolonged precipitation as the warm and cold air masses remain in contact with each other. They can also lead to the formation of other weather systems, such as low-pressure systems. Table 2. Fronts and Their Characteristics Type of front Symbol Characteristics Cold air advancing and pushing Cold front underneath warm air Warm air advancing and rising over cold Warm front air Cold front catches up with warm front, Occluded front lifting warm air from the surface Stationary front Does not move or moves very slowly Fig.1. Weather map 31  BSEd (Sci) SESE 104: Meteorology Course Content (Lecture Notes) 2. Cyclones, Storms, and Typhoons Cyclone The name "cyclone" comes from the Greek word "cyclos," which refers to a snake's coils. Henry Paddington coined it because the tropical storms in the Bay of Bengal and the Arabian Sea appear like coiled serpents of the sea. Caused by atmospheric disturbances surrounding a region of low pressure that is characterized by rapid and frequently destructive air circulation. Frequently accompanied by severe weather and storms. In the Northern hemisphere, the air cycles counterclockwise, while in the Southern hemisphere, the cycle is clockwise. They occur in various regions and known by different names depending on location: Indian Ocean and South Pacific Cyclones Northwest Pacific Ocean Typhoon Atlantic and Eastern Pacific Oceans Hurricane In general, Cyclones are classified as (i) extratropical cyclones and (ii) tropical cyclones. Tropical Cyclones Extratropical Cyclones Formation Warm tropical oceans (near the Cooler regions farther from the equator). equator where warm and cold air meet. Power It gets energy from warm ocean Powered by the difference in water. The heat from the ocean temperature between warm air and makes the air rise, and as the air cold air. When these two types of air rises and cools, it powers the storm. clash, it creates a storm. Appearance Have a circular shape with a clear, Have a more uneven, comma-shaped calm center called the eye, structure, with warm air on one side surrounded by strong winds and and cold air on the other. They do rain. not have an eye. Wind Have their strongest winds near the The winds can also be strong, but Strength center. The winds can become they are spread out across a larger extremely powerful, especially in area, especially around cold and hurricanes and typhoons. warm fronts. Movement They move from east to west and Move from west to east in the mid- often turn toward the poles (north latitudes, driven by global wind or south) as they travel. patterns. Effects Cause heavy rain, strong winds, and Bring rain, snow, and wind, along flooding. They can also bring a with temperature changes. In dangerous storm surge (a rise in sea winter, they can cause blizzards. level). 32  BSEd (Sci) SESE 104: Meteorology Course Content (Lecture Notes) Anatomy of a Cyclone Anatomy of a Cyclone a) The Eye. A tropical cyclone's calm, clear central part is called the eye or the calm central core. The climate here is mild and much lower than elsewhere, and clouds are also often absent. The average pressure on Earth is around 1,000 millibars, but during a cyclone, In the eye, it can drop to 960 millibars or even lower during more giant storms like super typhoons, where it can drop as low as 880 millibars. The rapid variations in pressure close to the eye provide a powerful force that propels the strong winds in the surrounding eyewall. b) The Eyewall. The eyewall, which experiences the strongest winds and most rain, is the most hazardous area of a tropical cyclone. From the surface, towering clouds reach 15,000 meters (49,000 feet). The sharp drop in pressure close to the eye causes the high winds here; the greatest winds are seen around 300 meters (1,000 feet) above the ground. Because of friction, winds slow down close to the surface, and the winds get weaker as pressure drops further up. Winds turn toward the center of the eye due to friction at the surface, creating moist air from the sea. The cooling air forms the storm's towering clouds and heavy rainfall as it climbs, producing strong updrafts (vertical wind speeds) in the eyewall. The eye is wider at the storm's peak than at the surface because air spirals outward as it climbs in the eyewall. The Coriolis force, which causes winds in the upper portion of the cyclone to move in the opposite direction from those at the surface, influences this outward flow. c) Rainbands. Rainbands are spiraling bands of rain and clouds that encircle a tropical cyclone's core. They can range from hundreds of kilometers from the center of the storm and are made of areas of heavy rain and thunderstorms. They can produce rain and, at times, even hail and gusts of wind, and in extreme cases, cause tornadoes. Rainbands may spin around the storm or stay in place depending on how the storm moves. As a cyclone approaches land, these rainbands may cause flooding and severe rain in areas distant from the storm core. FORMATION OF CYCLONES a. It begins in the warm ocean currents—it starts in oceans with warm waters with temperatures not less than 26.5°C or 80°F. These occur in 5 and 20 latitudes south of the equator. Heat from the warm ocean is necessary for a storm to be created. The heat forces the above air over the warmed ocean to rise. b. Rising Warm, Moist Air—Warm air rises, and contracts and water vapor turns to water through condensation to form clouds. Latent heat is then released, warming the surrounding air and causing it to rise even higher. This cycle of uplift and condensation 33  BSEd (Sci) SESE 104: Meteorology Course Content (Lecture Notes) of warm, moist air goes on and on, resulting in a significant pressure low over the ocean surface. c. A Low-Pressure Area—A rising air mass produces a low-pressure area at the base, which forces warm, moist air from other places to rush in. Air then enters and starts spinning around due to a force known as the Coriolis effect, which results from the rotation of the Earth. In the Northern Hemisphere, the air spirals counterclockwise, while in the Southern Hemisphere, it spirals clockwise. d. Formation of a Cyclone. As more warm air is drawn into the cyclone and starts ascending, the cyclone becomes well-defined. The circular motion increases, and the storm becomes larger and denser. e. Intensification of the Cyclone. As long as the cyclone is still over, warm waters will intensify because of energy drawn from the ocean. The air in the center of the storm warms up, and the pressure lowers further, resulting in swift winds. The stiffer the wind, the further the center pressure drops in a self-reinforcing cycle that may result in a full-fledged storm. f. Movement. Tropical cyclones' movement is generally shifted by extratropical general wind currents, such as trade winds, into a westward movement. Westerly winds will generally cause them to bend north or south as they continue moving northward. g. Landfall and Weakening. A cyclone begins to dissipate as it crosses land or into cold waters. This is because there will be less warmth in the ocean, so it cannot again draw energy from the warm ocean. On land, friction slows down the winds; once the warm ocean that fueled it is no longer available, the cyclone gradually weakens and dissolves. Storm Storms are violent weather phenomena because they are characterized by low pressure, cloud cover, high winds, heavy precipitation, and occasionally thunder and lightning. It is a general term that refers to weather disturbances, from light rainstorms to vital phenomena like tropical cyclones, tornadoes, and thunderstorms. In meteorology, "storm" refers to strong winds (103–117 km/h or 64–73 mph), heavy rain, and sometimes lightning and thunder. NOTE: A cyclone is a specific type of weather system with rotating winds and low pressure, while a storm is a general term for various types of atmospheric disturbances, including cyclones. Storm formation: Regions where the air pressure is lower than that of the surrounding air. The movement of two air masses—one cold and the other warmer—causes it to form. Cold masses descend while warm air ascends; this lowers pressure and produces a low-pressure zone. Typhoon Typhoons are tropical cyclones in the western Pacific Ocean, especially in Asia, near nations like China, Japan, and the Philippines. The term "typhoon" also refers to storms that form in a particular area but are the same as cyclones. Typhoons are large, intense storms with a round shape and revolving winds that can reach speeds up to 120 km/h (75 mph). They can cause significant damage through landslides, flooding, and storm surges and bring powerful winds and heavy rain. Like all tropical cyclones, 34  BSEd (Sci) SESE 104: Meteorology Course Content (Lecture Notes) typhoons develop over warm ocean waters and intensify due to atmospheric heat and moisture. The Philippines is susceptible to tropical cyclones because of its geographic location. The Philippines is located in the Pacific Typhoon Belt, one of the most active tropical cyclone regions; most typhoons form over the warm waters of the western Pacific, and the Philippines is frequently correct in their path. An average of 20 typhoons each year, five of which have the potential to be destructive, strike the nation. These typhoons can cause flooding and heavy rains across large areas, along with strong gusts that can kill many people and destroy property and crops. At first, the typhoons were known by international names. To provide Filipinos with a familiar and unique memory, the Philippine Atmospheric, Geophysical, and Astronomical Services Administration (PAGASA) gives typhoons Filipino names. Since 1963, storms that enter the Philippine Area of Responsibility (PAR) have been given local names, according to PAGASA. Typhoon naming did not involve the public until 1998. That year, PAGASA started a campaign called "Name A Bagyo," Filipinos were asked to offer local typhoon names. Out of all the nominations, a committee chose 140 names for Philippine typhoons. There were 25 names from A to Z in each of the four groups that were created from the list of names. If all 25 typhoon names are utilized within the year and another storm enters the nation, ten more auxiliary names were created, each beginning with the letters A through J. The alphabetically organized list of names, including male and female names and gender- neutral ones, shows how many typhoons reach the PAR year. Every four years, they switch up the names they employ. Auring, Bising, Crising, Dante, and other names from 2017 are therefore used in 2021 and will be used in 2025 and 2029. Cyclones, Storms, and Typhoons’ Impact Mitigation Understanding the damage these typhoons cause each year can help people prepare for catastrophes at home. While it may be impossible to fully anticipate or prepare for the next tragedy, learning about these previous catastrophes can help us understand what might happen next and how it might affect our future. Mitigation is a primary prevention of an adverse event or decreasing the negative consequences of this event. It could refer to activities taken to minimize the adverse impacts of risks. a. Environmental Protection: Mangroves and coastal forests should be preserved because they usually delimit the danger and impact of storm surges and coastal erosion. Their roots anchor the soil and also take moisture, protecting inland areas from severe flooding. Additionally, coral reefs should also preserve because they help dissipate wave energy, protect coastal areas from storm damage, and replenish beach sand to buffer against storm impacts. b. Climate Change Mitigation: Reducing greenhouse gas emissions through transitioning to renewable energy sources (Solar Energy, Wind Energy, Geothermal Energy, Hydropower, etc.). Additionally, Community engagement and education initiatives, including those about cyclone risks and community- based disaster preparedness efforts, can empower individuals and strengthen community resilience. c. Evacuation Plans: Communities should create detailed evacuation routes, with clear signages showing where to go during a typhoon. Drills and rehearsals ensure people know how to react and where to gather. 35  BSEd (Sci) SESE 104: Meteorology Course Content (Lecture Notes) d. Land Use Planning: Mapping will identify flood-prone areas, enforcing building codes for weather-resistant structures, and maintaining setback zones along coastlines and floodplains can minimize damage from storms. e. Early Warning Systems: Early detection of typhoons through satellites and weather radars allows authorities to send warnings via SMS, loudspeakers, or radios. Communities are informed in time to evacuate or prepare their homes. F. Atmospheric Optics 1. Light, Color and Atmospheric Optics The color of our world is defined by the interaction of objects with light. In fact, the reason we can see anything at all is due to the interactions of objects with light. This phenomenon includes the formation of rainbows, aurora borealis, blue skies and the color of sunsets. Those phenomena are all the result of different wavelengths of light within the electromagnetic spectrum. The visible light spectrum is the segment of the electromagnetic spectrum that the human eye can view. More simply, this range of wavelengths is called visible light. All electromagnetic radiation is light, but we can only see a small portion of this radiation—the portion we call visible light. Electromagnetic Spectrum Cone-shaped cells in our eyes act as receivers tuned to the wavelengths in this narrow band of the spectrum. Other portions of the spectrum have wavelengths too large or too small and energetic for the biological limitations of our perception. The cone is responsible for colors, while the rod is responsible for dark and depth vision at night. The rod is actually so sensitive that it cannot even see red. Red, green, and blue are considered the primary colors of light because when combined in equal intensity, they can produce any other color in the visible spectrum. Therefore, white light consists of all visible lights. This is due to the way our eyes perceive color. The colors we perceive in our environment are a result of light reflecting off objects. When light strikes an object, some wavelengths are absorbed while others are reflected. The reflected wavelengths are the ones that our eyes detect as color. For example, a red car appears red because it primarily reflects red light while absorbing other colors. Color perception 36  BSEd (Sci) SESE 104: Meteorology Course Content (Lecture Notes) 2. Blue Skies and Red-Orange Sunset Sunlight reaches Earth's atmosphere and is scattered in all directions by all the gases and particles in the air. Blue light is scattered in all directions by the tiny molecules of air in Earth's atmosphere. Blue is scattered more than other colors because it travels as shorter, smaller waves. This is why we see a blue sky most of the time. Closer to the horizon, the sky fades to a lighter blue or white. The sunlight reaching us from low in the sky has passed through even more air than the sunlight reaching us from overhead. As the sunlight has passed through all this air, the air molecules have scattered and re-scattered the blue light many times in many directions. Also, the surface of Earth has reflected and scattered the light. All this scattering mixes the colors again, so we see more white and less blue. Rayleigh Scattering What makes a red sunset? The angle of sunlight as it enters the atmosphere also affects the color of the sky. During sunrise or sunset, when the Sun is close to the horizon, the light must travel through more of the atmosphere than it does when the Sun is overhead. This results in more scattering of light, including longer wavelengths such as yellow, orange, and red, which creates colorful sunrise and sunset skies. Midday vs. Sunset/Sunrise Danger signals are usually red for the same reason. These signals are visible to an observer even from a long distance, as the red light scatters the least. They are also visible in the presence of smoke, fog or smog. Stop sign Traffic light Police siren Ancient Beliefs on the Color of the Sky Spiritual. In Inuit legend, the Northern Lights are believed to be the dancing spirits of deceased loved ones. They are seen as a sign of good fortune and a connection to the spiritual world. Timekeeping. The Egyptians used the position of the Sun in the sky and its color to determine the time of day. They divided the day into twelve hours, each associated with a specific constellation. The color of the sky could provide additional clues, such as a red sky at dawn or sunset indicating the beginning or end of the day. 37  BSEd (Sci) SESE 104: Meteorology Course Content (Lecture Notes) Harvest. In Greek mythology, the goddess Demeter, associated with agriculture and harvest, was often connected to the colors of the sky. A bright blue sky could be seen as a sign of a bountiful harvest, while a stormy sky might be interpreted as a warning of crop failures. Weather Prediction. In European folklore, there were similar beliefs about the predictive power of the sky. A red sky at sunset was often associated with fair weather the following day, while a red sky in the morning was said to bring wind and rain. 3. Rainbow Formation A rainbow is an arch of colors formed in the sky in certain circumstances, caused by the refraction and dispersion of the sun's light by rain or other water droplets in the atmosphere. Raindrops act as prisms when the sun shines in one part of the sky and rains in another. All rainbows are circular, but usually, the ground gets in the way. Rainbows look flat because we do not have any visual clues as to where the back of the rainbow is. Key Concepts in Rainbow Formation: a. Refraction- is the change in the direction of light as it moves from one medium (such as air) into another medium (such as water), where it travels at a different speed. This bending occurs because light slows down when it enters a denser medium (like water), and the change in speed causes the light to bend. When sunlight enters a raindrop, it refracts (bends) at the surface where the air and water meet. This is the first step in splitting the white light into component colors. The angle of refraction depends on the wavelength (or color) of the light, with shorter wavelengths (like blue and violet) bending more than longer wavelengths (like red). This bending initiate the separation of Rainbow Formation colors in the spectrum. b. Dispersion-is the process by which white light splits into different colors (wavelengths) because each light color refracts by a different amount when it passes through a medium. When sunlight enters the raindrop, the different colors of light bend at different angles. For example, violet light bends more than red light. This causes the light to fan out into its constituent colors inside the raindrop. The separation of colors due to different bending angles allows the distinct bands of colors in a rainbow to form. Dispersion is what gives the rainbow its characteristic "ROYGBIV" pattern. c. Reflection- is the process by which light bounces off a surface. In the case of a rainbow, after the light has refracted inside the raindrop, it hits the inner surface of the droplet and is reflected toward the front. This reflection inside the raindrop brings the light back to the observer similarly. In this process, there is no internal reflection, so the light cannot escape from the raindrop in a way that people on the ground can see. The 38  BSEd (Sci) SESE 104: Meteorology Course Content (Lecture Notes) value of internal reflection is in the ability of observer to see the light which undergoes refraction and dispersion. d. Second Refraction—occurs when light that has undergone reflection inside a raindrop emerges from the droplet. After leaving the droplet, it turns again, further separating the color bands. This second bending further increases the extent of color separation carried out by the first reflection. The different wavelengths (colors) of light exit the raindrop at slightly different angles, spreading the colors out even more. This creates the distinct arc of colors that we see in a rainbow. e. Order of Colors- it is determined by the angles at which the different wavelengths of light are refracted and reflected. Red light, which has a longer wavelength, is bent the least and exits the droplet at the highest angle, forming the outermost color of the rainbow. Violet light, with the shortest wavelength, is bent the most and exits at the lowest angle, forming the innermost color. The standard order of colors in a rainbow is red, orange, yellow, green, blue, indigo, and violet (ROYGBIV). This sequence is consistent because of the specific way in which each color interacts with the water droplets based on its wavelength and refractive properties. Conditions for Rainbow Formation: a. Presence of Water Droplets Water droplets in the atmosphere, typically after or during rain, serve as the medium through which light is refracted (bent), reflected (bounced back), and dispersed (split into colors). These droplets act as mini prisms that cause the sunlight to undergo this process, which leads to the spectrum of colors we see in a rainbow. When light from the sun passes through a water droplet, it slows down and, therefore, bends when it passes from air into the water. The light then reflects off the back of the droplet before being refracted again as it recedes out further. These two refractions and reflections cause the dispersion of colors, thereby producing the rainbow. b. Sunlight Light is a key factor in the formation of a rainbow; the light has to be direct. Refraction of sun rays is possible if the solar rays hit the water droplets at a particular angle. Usually, to get the desired rainbow, the sun has to be rather low, at 42 degrees or lower. As the sun rises higher in the sky, the light coming through travels through the atmosphere at a steeper path, substantially reducing chances of refraction by water droplets at the right angles to make a visible rainbow. c. Observer's Position The location of the observer is critical. A rainbow is formed only when the person’s back is towards the sun, and he or she faces the rain. The sunlight enters the water droplets in front of the observer, and after refraction and reflection within the droplets, the light exits back toward the observer's eyes. This alignment allows the sunlight to interact with the water droplets to reach the observer. If an observer faces the sun, they will not be able to see the light reflected in the opposite direction. 39  BSEd (Sci) SESE 104: Meteorology Course Content (Lecture Notes) Types of Rainbows (A) Primary Rainbow. A primary rainbow is created when sunlight enters a water droplet, undergoes a single internal reflection, and then exits the droplet. (B) Secondary Rainbow. A secondary rainbow forms under special conditions when light undergoes two internal reflections inside the water droplet before exiting. This means that the light bounces twice off the inside of the droplet, and with each reflection, some light is lost. This makes the secondary rainbow fainter than the primary one. Rainbows hold various forms of significance, from cultural and symbolic meanings to scientific importance: a. Scientific Importance. Rainbows help us understand the behavior of light—specifically, how light can be refracted, reflected, and dispersed. They demonstrate the visible spectrum and how white light is composed of different colors. Rainbows are natural examples of the physical principles of optics. Studying them can help students and scientists explore concepts like refraction, dispersion, and wavelength differences. b. Environmental Indicators. In the natural world, the appearance of a rainbow is often a sign that rain has stopped or is lessening. Rainbows usually appear when the sun shines through lingering moisture in the air. A study in 2022 explored how climate change will increase rainfall visibility and comes with a previous that the frequency of witnessing rainbows will be 5% higher by 2100, especially in higher latitudes and altitudes. This is about rainfall and cloud cover due to the effects of global warming. However, this pattern is likely to be less noticeable in places with less rainfall, such as the Mediterranean. This study gives both good and bad news. On the one hand, the fact that with the help of climate change, we might see more and more rainbows seems encouraging, as more people will have more chances to enjoy this incredible phenomenon of nature. However, it points out the negative effect of climatic change on weather around the globe in general. Those areas with more rainbows can also receive more rain counterparts, such as rainfall and cloud cover, while those with few rainbows may be going through effects of low rainfall, such as drought. It could only be that with the more rainbows as a mere consolation, there are deeper bad omens for the environment. c. Cultural and Symbolic Importance. In different countries and ethnic histories, the rainbow is associated with hope, unity, and universal restoration. Usually, it is encountered after storms, symbolizing rebirth after a stormy period of life. Promises or connections, and in many mythologies, rainbows are symbols of bridges or passage to other realms. The same is true in biblical usage with reference to covenant in Christianity. 3 Learning Activities 1 SUMMATIVE TEST End of Week 10 – 12 40