Black-Box ExperimentYou are given a sealed box with two electrical terminals. The box contains a resistor in series with either an inductor or a capacitor. When you attach an ac generator with an rms voltage of 0.750 V to the terminals of the box, you nd that the current increases with increasing frequency. (a) Does the box contain an inductor or a capacitor? Explain. (b) When the frequency of the generator is 25.0 kHz, the rms current is 87.2 mA. What is the capacitance or inductance of the unknown component in the box?
Physical Geography Lecture 9 Overview of Weather and Climate Weather: shortterm condition of the atmosphere Meteorology: study of short term atmospheric phenomena that constitude day to day weather Climate: weather over time The day to day changes in the weather are not isolated events but are controlle by larger scale systems air mass interactions rossby waves tropical cyclones Generalized statement of the prevailing weather conditions at a given place based upon statistics of a long period of records Climate is described in terms of energy and moisture inputs Geographical view is that climate is a source of heat energy and water needs for plants Climatology: studies the graphic distribution and character of Earth’s climates Climatic regions are areas with similar weather statistics Factors Affecting Climate Latitude (sun angle) Intensity of radiation and length of day have direct impact on air temperature Seasonality annual variation of sun angle influences seasonal temperature changes Land and Water Distribution Impacts temperature and precipitation. Land and water respond differently in temp to insolation Ocean Currents Warm currents off east coasts of continents in the subtropical and mid latitudes Moderate air temperatures, adds water vapor to air and promotes precipitation Cool and cold currents are located off the west coasts of continents produce arid climates along coasts. Chills overlying air, stabilizing it, and inhibiting precipitation Elevation and Topography Influence atmospheric processes and precipitation Temperatures decrease with elevation Mountains block movement of air masses Orographic precipitation (windward) and Rainshadow (leeward) Pressure and Winds Pressure influences atmospheric stability or instability winds transfer sensible and latent heat from tropics to poles Air masses and air mass movements different temperature and humidity characteristics lead to predictable weather Earth’s Temperature Patterns Thermal Equator: Imaginary line connecting points of highest temperatures for lines of longitude January Temperature Map: Movement of Thermal equator southward more pronounced over large continents Air Masses Large bodies of air that have uniform temperature and humidity characteristics at any given elevation. cover 100,000s of square miles the boundary between two air masses is called a front. Usually the site of pronounced weather changes Temperate and humidity characteristics are derived from source regions Source regions are areas of the earth over which air accumulates large, relatively flat surfaces such as oceans and plains mountainous areas are not good source areas turbulence caused by mountains breakup air masses Classes of Air Masses A, AA Arctic and Antarctic bitterly cold and dry P Polar seasonal changes in temperatures cool to warm in summer cool to bitterly cold in winter T Tropical warm to hot C Continental Dry M Maritime moist Teleconnections: “Links between environmental events, particularly between climatic variations, separated () North Atlantic Oscillation Oscillation of air and ocean masses that affect a large part of Europe and wetern Asia, as well as eastern North America Function of the relative strengths of the Icelandic Low and the Azores High Stronger pressure gradient (high index) leads to more northerly track of intense winter storms most of Europe is spared sever winter storms Weaker pressure gradient (low index) leads to fewer and weaker winter storms higher temperatures in summer colder temperatures in winter El NinoSouthern Oscillation of La Nina El Nino Southern Oscillation Reversal of the “normal” pressure and wind pattern in the southern pacific ocean Occur on average every 5 years (range is 2 to 8 years) Caused drought in Indonesia and Australia Heavy rains and flooding to coastal South American La Nina Event that follows El Nino event Reasserts the “normal” pressure and wind pattern Causes flooding in Australia Lecture 10 Polar Weather Characteristics Weather is dominated by Arctic and Antarctic air masses air masses are cold and dry year round Polar Highs generate the Polar easterlies winds during the winter directs cold air towards the equator to warm up polar easterlies generally cases blowing during the summer least consistent of the planetary winds Katabatic winds example of a smallscale circulation caused by localized pressure and temperature differences occur in Polar Regions and mountains very cold dense air drains off the sides of glaciers, mountains and plateaus can be strong Polar Climates Cold to extremely cold year around and relatively dry Often referred to as polar deserts Tundra climate at least one month where temp average above freezing but under 10º C (50ºF) permafrost underlies many areas short “summers” lead to surface thawing ponded and standing water on the surface Ice cap Climate every month averages below freezing Polar Marine more moderate in winter colder than tundra in summer low annual range of temperature no month below 7ºC (20º F) Mid Latitude Weather Most precipitation in the midlatitudes starts as snow because many clouds form at altitudes were temperatures are below freezing if temperatures near the surface are below freezing it remains as snow If temperatures near the surface are above freezing it melsa and falls as rain Midlatitude weather is dominated by the interactions of large air masses of unlike characteristics Temperature Inversion layer of warm air overlying cooler air at the surface temporary phenomena common in the midlatitudes air at surface cannot rise and mix leads to a buildup of air pollutants at and near the surface serious air pollution episodes Fronts Fronts are best described as transition zones from the surface and extending up into the atmosphere. Surface of Discontinuity. Cold Fronts: cold air masses advance against warm air masses cold air forces warm air aloft 400 km wind (250 miles) Warm Fronts: warm air masses advance against cold air masses warm air moves up and over cold air 1000 km wide (600 miles) Stationary Fronts: air masses are stalled Occluded Fronts: cold front overtakes a warm front. one fronts get lifted Violent Weather of the MidLatitudes and Beyond Thunderstorms: most common storm type in the world caused by convergent, frontal and convectional lifting approximately 1800 in progress at any given time Tornadoes: smallest but most violent storms known to humanity Characteristics of Continental Climate Located from 35 degrees to 60 degrees norther. Large areas of this climate found only in Northern Hemisphere except in highland areas in southern hemisphere no large land masses in southern hemisphere Large annual ranges of temperature Annual moisture surpluses most precipitation is due to cyclonic activity MidLatitude Western Continental Edge Climates Two major climate types Marine (often called marine west coast) climates Mediterranean or dry summer subtropical climates Mediterranean Climates