4 Meteorology

4 METEOROLOGY Weather ☆ Meteorology is the study of atmosphere and focuses on weather processes and forecasting. ☆ Forecast is the prediction of future weather with the use of weather instruments. Weather forecasting was not available before the 1950s. ☆ Climate is the change in atmosphere over a long period while weather is something that can change pretty often. ☆ The Sun provides almost all of earth's energy and when this energy evaporates water, clouds are formed which are responsible for precipitation; this energy also provides heat which affects surface and atmospheric temperature. ☆ Weather is the result of heat, Earth’s air, and water’ the difference in Earth’s surface causes uneven heating in the atmosphere and heat redistributes this. ☆ Weather usually moves in all directions. ☆ In the United States, it moves from the west to east often because that is the direction that the jet stream blows. ☆ Jet Streams are fast flow, narrow air currents in our atmosphere. Weather Instruments Wind Vane - a weather instrument that measures wind direction; measured in cardinal directions. Barometer - a weather instrument that measures atmospheric pressure; measured in millibars. Anemometer - a weather instrument that measures wind speed; measured in knots. Hygrometer - a weather instrument that measures humidity; measured in percentage. Thermometer - a weather instrument that measures temperature; measured in Kelvin, Fahrenheit, and Celsius. Rain Gauge - a weather instrument that measures precipitation; measured in millimeters. Station Models ☆ A station model is a symbolic illustration which shows the weather conditions over a specific area. ☆ It includes the temperature, present weather, visibility, dew point, wind speed, amount of cloud cover, barometric pressure, barometric trend, precipitation, and wind direction. Moisture ☆ Moisture is a product of evaporation; it is the water vapor diffused into the atmosphere. ☆ Temperature, exposure of the surface area, and other substances present in the liquid affect evaporation rates. ☆ Coagulation is the process in which the atmosphere is naturally cleaned. Droplets and aerosols attract and act as a natural phenomenon to clear the air of pollutants. ☆ Humidity is the amount of water vapor or moisture present in the air. ☆ In warmer temperatures, water molecules in the air move quicker and don't easily condense. In cooler temperatures, water molecules in the air move slower and condense easily. ☆ Relative humidity represents the percentage of water vapor in air. When air temperature changes, so does the humidity. ☆ Dew point indicates the temperature at which water evaporates and moisture is formed. The higher the dew point, the higher the moisture content. ☆ As temperature and the dew point get closer together, the air becomes closer to saturation. Therefore, the chances of precipitation increases. ☆ The humidity is higher in warmer weather conditions than cool weather conditions. ☆ The higher the temperature, the more capable it is to hold water vapor. As air warms, the capacity increases, as it cools, the capacity decreases. ☆ When warm air is forced upward, expanded, and cooled, clouds are formed. When the air cools, the water vapor needed for saturation decreases and the relative humidity increases. ☆ These water molecules consensus into tiny droplets, and when the cloud is saturated enough, it is suspended in the form of precipitation. ☆ Clouds are classified by shape and height which are determined by temperature, pressure, and humidity. ☆ Some extend higher than others which are low and flat; some more dense and the other thin. ☆ The main types of clouds are Stratus (formed at low altitudes and associated with rain and snow), Cumulus (puffy with flat bases and found higher up), and Cirrus (fibrous and curly clouds made of ice crystals; indicate storms). Pressure and Wind ☆ Wind is the horizontal movement of air caused by the difference in pressure. ☆ Wind is named after the direction it blows from. ☆ The movement of wind is caused by the uneven heating of Earth; This is due to a low pressure system. ☆ When warm equatorial wind rises above the surface and moves to the poles, cool air moves to the surface and towards the equator at the same time. ☆ Warm, expanding air has low atmospheric pressure. Cooler air is denser and tends to sink, bringing about high atmospheric pressure. ☆ Wind results from air moving from regions of high pressure to regions of low pressure. Sea Breeze: - Land heats up faster than water because land has a lower specific heat. - Radiation and conduction from the land's surface heat the air over land. The heated air expands and becomes less dense which causes it to rise. - The result is a breeze that comes from the water to replace the rising air over the land. - Sea breezes are light winds that blow from the water to the land. The breeze will continue throughout the evening Land Breeze: - At night time, land cools off faster than water because it has a lower specific heat. When the land cools, the air above also cools. The air over the water is now warmer than the air over the land, so the air above the water begins to rise. This causes the wind to change direction (blows from land to water) Coriolis Effect: ⎼ The tendency of an object moving across the Earth to move in a curved path. ⎼ Due to the Earth’s rotation, the paths in the Northern Hemisphere curve right and paths in the Southern hemisphere curve left. ⎼ The Coriolis effect causes wind directions to be altered. ⎼ Wind moves away from a high pressure area in a clockwise pattern. ⎼ Wind moves toward a low pressure area in a counterclockwise pattern. ⎼ Prevailing winds flow from high to low pressure and are deflected by this effect. - Pressure is caused by the weight of the atmosphere pushing down. The higher the altitude, the lower the pressure. The higher the temperature, the higher the pressure. Low pressure is associated with clouds and precipitation along with temperature changes. High temperature is associated with dry and clear weather with a stable temperature and sunshine. Air Masses and Fronts 1. 2. 3. 4. 5. - Air masses are large bodies of air that have properties similar to the part of where they develop. cA (Continental Arctic) - cold, dry air masses formed in the arctic and antarctic regions. cP (Continental Polar) - cold, dry air masses formed over dry lands. cT (Continental Tropic) - hot, dry air masses formed over deserts and plains. mT (Maritime Tropic) - hot, humid air masses. mP (Maritime Polar) - cold, humid air masses. A boundary between two air masses has different moisture levels, temperature, and density. This is called a front. 1. Warm Front - when a cold air mass is advancing into a warm air mass from southwest to northeast. 2. Cold Front - when a warm air mass is advancing into a cold air mass. 3. Stationary Front - a front where neither the cold air mass or warm air mass is strong enough to advance, so the air shows no change. 4. Occluded Front - warm air gets trapped between cold air masses. The warm air is cut off from the air and pushed upwards as the temperature increases. It causes storms and precipitation.