Fundamentals Of Meteorology PDF

FUNDAMENTALS OF METEOROLOGY CAMILLE RAFAL Instructor 1 College of Arts and Sciences Department of Physical Sciences COLLEGE OF ARTS & SCIENCES Department of Physical Sciences Unit III: Seasonal and Daily Temper...

FUNDAMENTALS OF METEOROLOGY CAMILLE RAFAL Instructor 1 College of Arts and Sciences Department of Physical Sciences COLLEGE OF ARTS & SCIENCES Department of Physical Sciences Unit III: Seasonal and Daily Temperature 1. Seasons in the Northern Hemisphere 2. Seasons in the Southern Hemisphere 3. Local Seasonal Variations 4. Daily Warming and Cooling of Air Near the Surface 5. Applications of Air Temperature Data  Learning Objectives At the end of this topic, you should be able to: 1. explained why seasons change and how it affects the weather; 2. described the seasonal and hourly variations of air temperature; and 3. assessed the local diurnal cycle of temperature. COLLEGE OF ARTS & SCIENCES Department of Physical Sciences Why Earth has Seasons? Our seasons are regulated by the amount of solar energy received at Earth’s surface. This amount is determined primarily by the angle at which sunlight strikes the surface, and by how long the sun shines on any latitude (daylight hours). Why Earth has Seasons? The 23.5° tilt is the key reason for the changing seasons. In June, the Northern Hemisphere is tilted toward the sun: summer. In December, the Northern Hemisphere is tilted away from the sun: winter. Seasons in the Northern Hemisphere Seasons in the Northern Hemisphere Summer Solstice On June 21, the Northern Hemisphere is tilted toward the sun, receiving the most direct sunlight of the year. The sun is directly overhead at 23.5°N latitude (Tropic of Cancer) at noon. This marks the astronomical start of summer and the longest day of the year. Seasons in the Northern Hemisphere Longer Daylight On June 21, latitudes in the Northern Hemisphere experience more than 12 hours of daylight. The farther north you go, the longer the daylight, with 24 hours of daylight at the Arctic Circle (66.5°N) and beyond. The North Pole has continuous sunlight from March 20 to September 22. Seasons in the Northern Hemisphere Autumnal Equinox By September 22, the sun is directly over the equator, marking the autumnal equinox. Days and nights are of equal length around the world. At the North Pole, the sun sets for six months, leading to long periods of darkness and cold Seasons in the Northern Hemisphere Winter Solstice On December 21, the Northern Hemisphere is tilted away from the sun, marking the shortest day of the year. The sun is directly overhead at 23.5°S (Tropic of Capricorn). Solar energy is spread over a larger area, and the sun remains low in the sky, resulting in colder temperatures. Seasons in the Southern Hemisphere Seasons in the Southern Hemisphere Winter Solstice On June 21, the Southern Hemisphere is tilted away from the sun, marking the winter solstice. Days are short, nights are long, and sunlight hits the surface at a low angle, resulting in cooler temperatures. This is the astronomical start of winter in the Southern Hemisphere. Seasons in the Southern Hemisphere Summer Solstice On December 21, the sun is directly over the Tropic of Capricorn (23.5°S), marking the start of summer in the Southern Hemisphere. This is the opposite of the Northern Hemisphere, which experiences winter during this period. Travel to the Southern Hemisphere in December to enjoy warm, summer-like conditions while it’s winter up north! Seasons in the Southern Hemisphere When it’s summer in the Northern Hemisphere, it’s winter in the Southern Hemisphere, and vice versa. Seasons in the Southern Hemisphere Due to Earth’s elliptical orbit, spring and summer in the Southern Hemisphere are about a week shorter than in the Northern Hemisphere. This slightly offsets the additional solar energy the Southern Hemisphere receives when it’s closer to the sun. Local Seasonal Variations  Climate of the Philippines The climate of the Philippines is tropical and maritime. It is characterized by high temperatures, high humidity, and abundant rainfall throughout the year. Similar to the climate of Central American countries. COLLEGE OF ARTS & SCIENCES Department of Physical Sciences  Climate of the Philippines Temperature The mean annual temperature across the Philippines (excluding Baguio) is 26.6°C. Coolest month: January, with an average of 25.5°C. Warmest month: May, with an average of 28.3°C. Temperature variation is primarily influenced by altitude, not latitude. COLLEGE OF ARTS & SCIENCES Department of Physical Sciences  Climate of the Philippines Humidity Humidity refers to the moisture content in the air. Due to the country’s high temperatures and proximity to surrounding bodies of water, the Philippines experiences high relative humidity. Average monthly relative humidity: 71% in March (lowest) 85% in September (highest) COLLEGE OF ARTS & SCIENCES Department of Physical Sciences  Climate of the Philippines Rainfall Rainfall is the most important climatic element in the Philippines. Rainfall distribution varies across regions, influenced by: Direction of moisture-bearing winds. Location of mountain systems. Mean annual rainfall: Ranges from 965 mm to 4,064 mm. Areas with highest rainfall:Baguio City, Eastern Samar, Eastern Surigao. Lowest rainfall: Southern Cotabato General Santos City: Receives only 978 mm annually. COLLEGE OF ARTS & SCIENCES Department of Physical Sciences  Climate of the Philippines The Seasons The climate of the Philippines is categorized into two major seasons: Rainy Season: June to November Dry Season: December to May Cool Dry Season: December to February Hot Dry Season: March to May COLLEGE OF ARTS & SCIENCES Department of Physical Sciences  Climate of the Philippines Climate Types The Philippines has four distinct climate types based on rainfall distribution: Type I: Two distinct seasons (dry and wet). Type II: No distinct dry season; rainfall is evenly distributed throughout the year. Type III: Rainfall more or less evenly distributed, but with a pronounced dry period. Type IV: Rainfall is evenly distributed throughout the year with no significant dry season. COLLEGE OF ARTS & SCIENCES Department of Physical Sciences Daily Warming and Cooling of Air Near the Surface  Daytime Warming ▪ Sunlight warms the ground, and the ground warms the air in contact with it by conduction. ▪ Air is a poor heat conduction. ▪ Near surface, convection can also help to redistribute the heat. In calm weather, the thermal convection effect is small and do not effectively mix the air near the surface. ▪ Thus, there is a substantial temperature difference above the ground on windless day. Daytime Warming ▪ On windy days, turbulence eddies are able to mix hot, surface air with cooler air above. ▪ This form of mechanical stirring, called forced convection, helps the thermals to transfer heat away from the surface more efficiently. Daily Temperature Variations ▪ Around noon, the sun’s rays are most intense. ▪ However, even though incoming solar radiation decreases in intensity after noon, it still exceeds outgoing heat energy from the surface for a time. ▪ This situation leads to energy surplus for 2-4 hours after noon. ▪ It leads to a lag between the time of maximum solar heating and the time of maximum air temperature. Daily Temperature Variations Daily Temperature Variations ▪ The exact time of the maximum temperature varies. ▪ Tmax is about 3-5pm during summer cloud-free days. ▪ If there is afternoon cloudiness or haze, Tmax usually occurs an hour or two later. ▪ Tmax also depends on surface type and cover 1. Absorption characteristics (Strong absorbers enhance surface heating) 2. Vegetation/moisture (Available energy partially used to evaporate water) ▪Tmax also depends on wind. Strong mixing by wind will mix heated air near ground to higher altitudes.  Nighttime Cooling ▪ At night, both ground and air above cool by radiating infrared energy, a process called radiational cooling. ▪ Ground, a better radiator than air, is able to cool more quickly. ▪ After sunset, surface is cooler than the air above it. Measured increase in air temperature above the ground is known as radiation inversion or nocturnal inversion. Nighttime Cooling Temperature gradient is smaller in windy night than calm night. Evening length, water vapor, clouds, and vegetation affect earth’s nighttime cooling.  Cold Air Near the Surface Night time radiational cooling increases air density. Cold, heavier air settles to the valley bottom. It leads to a thermal belt of warmer air between lower and upper cooler air.  Cold Air Near the Surface On the valley floor, cold and dense air cannot rise. Smoke and other pollutants are trapped. Thus, valley bottom is colder and more frequently polluted than nearby hillsides. Applications of Air Temperature Data Protecting Crops from the Cold Night Air ▪ On cold nights, many plants may be damaged by low temperatures. ▪ To protect small plants or shrubs, cover them with straw, cloth, or plastic sheeting. This prevents ground heat from being radiated away to the colder surroundings. ▪ The lower branches of fruit trees are the most susceptible to damage. Increasing the air temperature close to the ground may prevent damage. We can increase near-ground temperature by using orchard heaters. It can warm the air around the trees by setting up convection currents close to the ground. Protecting Crops from the Cold Night Air ▪ Another way to protect trees is to mix the cold air at the ground with the warmer air above, thus raising the temperature of air next to the ground. This can be accomplished by using wind machines. Daily (Diurnal) Range of Temperature ▪ Greatest variation in daily temperature occurs at the earth’s surface. It becomes smaller as we move away from the surface. ▪ By day, clear summer skies allow the sun’s energy to quickly warm the ground. At night, the ground cools rapidly by radiating infrared energy to space. Daily (Diurnal) Range of Temperature ▪ The largest diurnal range of temperature occurs on high deserts, where the air is fairly dry, often cloud-free. There is little water vapor to radiate much infrared energy back to the surface. ▪ Clouds are good reflectors of incoming solar radiation, and so they prevent much of the sun’s energy from reaching the surface during daytime. ▪ If the clouds persist into the night, they tend to keep nighttime temperatures higher, as clouds are excellent absorbers and emitters of infrared radiation. Measuring Air Temperature ▪ Thermometers were developed to measure air temperature. ▪ Liquid-in-glass thermometers are often used for measuring surface air temperature because they are easy to read and inexpensive to construct. ▪ Thermometers have a glass bulb attached to a sealed tube about 25 cm long. When the temperature rises (decreases), the liquid in the bulb expands (contracts). Hence, the length of the liquid in the tube represents the air temperature. Maximum Thermometer ▪ Maximum thermometer looks like any other liquid-in-glass thermometer with one exception: ▪ It has a small constriction within the bore just above the bulb. ▪ As the air temperature increases, the mercury expands and freely moves past the constriction up the tube, until the maximum temperature occurs. ▪ However, as the air temperature begins to drop, the small constriction prevents the mercury from flowing back into the bulbs. ▪ Thus, the end of the stationary mercury column indicates the maximum temperature for the \day. Maximum Thermometer Minimum Thermometer ▪ A minimum thermometer measures the lowest temperature during a given period. ▪ It is similar to other liquid-in-glass thermometers except that it contains a small barbell-shaped index marker in the bore. ▪ As the air temperature drops, the contracting liquid moves back into the bulb and brings the index marker down the bore with it. ▪ When the temperature stops decreasing, the liquid and the index marker stop moving down the bore. ▪ When the temperature increases, the alcohol expands and moves freely up the tube past the stationary index marker. ▪ Because the index marker does not move as the air warms, the minimum temperature is read by observing the upper end of the marker. Other Thermometers ▪ Electrical thermometer: Since the resistance of the material chosen for these thermometers changes as the temperature changes, the resistance can be calibrated to represent air temperature. ▪ Infrared sensors (Radiometers): By measuring both the intensity of radiant energy and wavelength of maximum emission of a particular gas (either H2O or CO2), radiometers in orbiting satellites are able to estimate the air Temperature from Atmospheric temperature at selected levels in the Infrared Sounder on Aqua Satellite atmosphere. Other Thermometers ▪ Bimetallic thermometer: It consists of two different metal (brass and iron) welded together to form a single strip. As the temperature changes, the brass expands more than the iron, causing the strip to bend.The small amount of bending is amplified through a system of levers to a pointer on a calibrated scale.  Summary 1. Daily variation in air temperature near the earth’s surface is controlled mainly by the input of energy from the sun and output energy from the surface. 2. On a clear, calm day, surface air warms as long as heat input (sunlight) exceeds heat output (convection and radiated infrared energy). 3. Surface cools at night as long as heat output exceeds input. 4. Coldest air is normally found at the surface, for the ground at night cools more quickly than the air above. 5. Greatest daily variation in air temperature occurs at the earth’s surface.  ACTIVITY 2 Temperature Diurnal Cycle DEADLINE: SEPT 23. 2024 Objectives: Understand the daily temperature variation (diurnal cycle). Explore factors influencing temperature changes throughout the day. Learn how temperature is measured and the instruments used. Formatting: Use A4 paper, Times New Roman, size 12 font, and justified alignment for your report. COLLEGE OF ARTS & SCIENCES Department of Physical Sciences  ACTIVITY 2 Temperature Diurnal Cycle Instructions: Data Gathering: Utilize weather apps or online platforms to gather hourly temperature data for a 24- hour period. Graphing: Plot the recorded temperature data on a graph with the time of day on the x-axis and temperature on the y-axis. Identify and mark key features of the temperature curve, such as: Time of Maximum Temperature (Tmax): The point at which the temperature is highest Time of Minimum Temperature (Tmin): The point at which the temperature is lowest COLLEGE OF ARTS & SCIENCES Department of Physical Sciences  ACTIVITY 2 Temperature Diurnal Cycle Analysis: (5-10 Sentences only) (You must elaborate the graph you created) Discuss the observed diurnal temperature pattern and compare it with theoretical expectations. Discuss how factors such as cloud cover, wind, and surface type affect the temperature cycle: Cloud Cover: Clouds can block solar radiation, leading to cooler daytime temperatures and warmer nighttime temperatures. Wind: Wind can enhance cooling during the day by mixing air and dissipating heat, and it can prevent temperature extremes at night. Surface Type: Different surfaces absorb and radiate heat differently. For instance, urban areas with asphalt and concrete heat up more during the day and cool down faster at night compared to rural areas with vegetation. COLLEGE OF ARTS & SCIENCES Department of Physical Sciences  ACTIVITY 2: RUBRICS Criteria Excellent (4 points) Good (3 points) Fair (2 points) Poor (1 point) Accurate and complete data Accurate data but may miss Incomplete data or missing Data is incomplete or Data Gathering for a full 24-hour period minor details several hours highly inaccurate Clear, accurate graph with Graph is mostly clear with Graph is unclear or missing Graph is incomplete or Graphing well-labeled axes and key minor issues important labels poorly labeled features Identification of Key Accurately identifies and Identifies Tmax and Tmin Identifies Tmax and Tmin Does not correctly identify Features marks Tmax and Tmin with minor errors with several errors Tmax or Tmin Thorough discussion that Analysis of accurately compares Good discussion with some Basic discussion with Limited or inaccurate Temperature observed data with minor inaccuracies significant gaps discussion Pattern theoretical expectations Comprehensive discussion Discussion of Good discussion with minor Basic discussion with Limited or inaccurate of cloud cover, wind, and Influencing Factors gaps several inaccuracies discussion surface type impacts Perfect adherence to Formatting and Noticeable formatting Poor formatting and formatting instructions (A4, Minor formatting errors Presentation errors presentation TNR, 12, Justified) COLLEGE OF ARTS & SCIENCES Department of Physical Sciences  LONG EXAM SEPT 23. 2024 Coverage: Units II & III 50 items 1-30 Multiple choice 31-40 Identification 41-50 Essay COLLEGE OF ARTS & SCIENCES Department of Physical Sciences Get in Touch With Us Send us a message or visit us City of Batac, Ilocos Norte, Philippines (63) 77-600-0459 [email protected] Follow us for updates facebook.com/MMSUofficial www.mmsu.edu.ph