Climate and Weather Notes PDF

Climate and Weather and Biomes NOTES Prof. T. Maenza-Gmelch The troposphere is composed of 78% nitrogen (N₂) and 21% oxygen (O₂) and CO2 (0.035%). Barometric pressure is the weight of air. Barometric pressure drops with increasing altitude. Why do you think this is the case? Earth’s Ene...

Climate and Weather and Biomes NOTES Prof. T. Maenza-Gmelch The troposphere is composed of 78% nitrogen (N₂) and 21% oxygen (O₂) and CO2 (0.035%). Barometric pressure is the weight of air. Barometric pressure drops with increasing altitude. Why do you think this is the case? Earth’s Energy Budget (fate of the 340 W/m² of incoming solar radiation): Earth’s energy budget refers to the balance between the energy the Earth receives from the sun and the energy Earth radiates back into space after this energy is distributed through the Earth systems: water, ice, atmosphere, crust, biosphere -29 percent is reflected back to space by clouds, atmospheric particles (aerosols) and bright ground surfaces like sea ice and snow -23 percent of incoming solar energy is absorbed by clouds, atmospheric gases -48 percent passes through the atmosphere and is absorbed by the surface So, generally, 70% of insolation is absorbed and 30% is reflected back to space. What is the fate of the absorbed heat? How is it used? 1 heat the Earth’s surface 2 evaporation of water 3 energy for photosynthesis What is a greenhouse gas? Gases that capture/trap long-wave radiation (heat) at the Earth’s surface. Examples are: water vapor (H20) nitrous oxide (N20) methane (CH4) ozone (03) carbon dioxide (CO2) plus others. What is the greenhouse effect? Energy capture by gases in the atmosphere. Ozone (03): Ozone at ground level is smog. This is bad for breathing. Ozone in the troposphere is a greenhouse gas. Ozone in the stratosphere is good. The stratospheric ozone layer shields living creatures from harmful UV radiation. We can damage the ozone layer by adding certain chemicals to the atmosphere. CFCs were banned after we found that CFCs can breakdown the ozone layer. The Energy budget can change: increased CO2 (traps outgoing heat at the Earth’s surface = global warming) melting of glaciers and sea ice (changes the albedo of the Earth’s surface from a light reflecting surface to a dark surface = absorb more heat = global warming) volcanoes erupt (aerosols from the ash that stay in the stratosphere reflect incoming solar radiation = global cooling) Let’s revisit: Fate of the absorbed heat at the Earth’s surface: Heats surface Evaporates water Provides energy for photosynthesis a closer look at water evaporation…….. Much of the incoming solar radiation is used to evaporate water. Every gram of evaporating water absorbs 580 calories of energy from the sun as it transforms from liquid water to water vapor. So water vapor contains a huge amount of stored energy know as latent heat. The water vapor then blows around the Earth’s atmosphere carrying the latent heat with it. When water vapor condenses back to liquid water, the 580 calories of heat energy are released. Solar energy is converted to latent heat during evaporation. The heat is stored in water vapor. Convection current: refers to the movement of air based on this principle: warm air rises and cool air sinks! (By the way, this applies to water too.) If you need to…watch this: https://www.youtube.com/watch?v=bN7E6FCuMbY Weather vs. Climate: Weather: local conditions at a given time (humidity, temperature, precipitation, winds, cloud cover); occurs in the troposphere. Climate: average conditions expected for a given place at a given time. Coriolis Effect: the deflection of a body of air to the right in the Northern Hemisphere and to the left in the Southern Hemisphere, caused by the rotation of the earth. https://www.youtube.com/watch?v=i2mec3vgeaI The climate of an area is influenced by: latitudinal distribution of sunlight (most important) proximity to ocean elevation presence of mountains Latitudinal distribution of sunlight differs from equator to poles = unequal distribution of heat energy. The shape and tilt of the earth, causes the sun’s beam to hit various places at different angles. The beam is more concentrated at the equator and more dispersed toward the poles. Insolation = incoming solar radiation This differential solar energy input to various parts of the earth drives all of our weather systems, ocean currents and distribution of life. Climate of the tropics and subtropics is largely determined by circulation cells. Hadley Cell: An air circulation cell; the circulation of air that rises at the equator, spins poleward, sinks at subtropical latitudes, and returns to the equator. The law of gases and other helpful facts: A gas allowed to expand becomes cooler A gas compressed becomes warmer Atmospheric pressure near the ground is greater than at higher altitudes As hot air rises it expands and cools Cool air holds less moisture than warm air The hot/moist air at the equator rises (updrafts). It cools and releases moisture (rains). The resulting cool/dry air moves poleward (N and S). At subtropical latitudes (20-30º N and S) the cool/dry air descends (downdrafts). (By the time it reaches the earth’s surface it is hot, as well as dry; forming the earth’s major desert regions.) The warm/dry air returns to the equator (the trade winds). As they cross the ocean, they pick up moisture. They arrive at the equator as warm/moist air. Climate of temperate and polar latitudes is largely determined by air masses. Airmass: A large body of air that has characteristic properties of temperature and humidity. Airmasses drive much of the weather in temperate latitudes such as in North America: Continental polar/Arctic forms over N. Canada and the Arctic; can pour cold/dry air down the continent Maritime polar brings cold/wet air from North Pacific and Labrador. Maritime tropical brings warm/wet air from Pacific or Gulf of Mexico. Continental tropical pushes north form Mexico and southwest US; brings warm/dry air. A jet stream runs between two airmasses of different temperatures. Our jet stream (northern hemisphere polar jet stream) is a river of air (wind) in the troposphere (generally about 7 miles above Earth’s surface) that moves fast across the continent from west to east. Jets streams play a key role in determining the weather because they usually separate colder air and warmer air, generally push air masses around, moving weather systems to new areas and even causing them to stall (ex., stalled rain causes floods). -The bigger the temp/pressure difference between two air masses, the faster the jet stream air moves. The less difference between the airmasses = slower and weaker wind. -The faster the wind, the stronger and therefore maintains its path (stable). If it is slow, it is weak: it destabilizes and so wiggles or bends. http://commons.wikimedia.org/w/index.php?title=File%3AAerial_Superhighway.ogv Traditionally, the Artic is very cold compared to the mid-latitudes so there is a great temp and pressure difference and so the jet stream is strong. The Arctic is warming due to climate change. What do you think will happen to NY winters? Weather map symbols: Front: the boundary between two different air masses How to read weather maps: https://www.youtube.com/watch?v=9NZz-EeveJ8 just watch up to 2:46 Rules: -The higher the temperature, the higher the air pressure. -Air wants to move from regions of high pressure to low pressure (or hot to cold) in order to equalize. This creates the wind. \ -Wind does not flow directly from the hot to the cold area, but is deflected by the Coriolis Effect and flows along the boundary between the two airmasses. Oceanic influences on climate: Ocean currents are created from the movements of the earth, air, and solar energy. Currents can transport heat. Coastal regions are especially influenced by currents. Oceans moderate the temperatures of adjacent lands. The Gulf Stream is an Atlantic Ocean current that originates in the Gulf of Mexico and follows the eastern coastline before crossing the Atlantic Ocean to Western Europe. It transports a lot of heat from the equator to northern latitudes: Great Ocean Conveyor Belt: constant motion in the ocean in the form of a global ocean conveyor belt caused by a combination of thermohaline currents (thermo = temperature; haline = salinity) in the deep ocean and wind-driven currents on the surface Cold, salty water is dense and sinks to the bottom of the ocean while warm water is less dense and remains on the surface The ocean conveyor gets its “start” in the Norwegian Sea, where warm water from the Gulf Stream heats the atmosphere in the cold northern latitudes. This loss of heat to the atmosphere makes the water cooler and denser, causing it to sink to the bottom of the ocean. As more warm water is transported north, the cooler water sinks and moves south to make room for the incoming warm water. This cold bottom water flows south of the equator all the way down to Antarctica. Eventually, the cold bottom waters return to the surface through mixing and wind-driven upwelling, continuing the conveyor belt that encircles the globe. noaa.gov Oceans “communicate” with the atmosphere by transferring heat and moisture = “teleconnections”. http://www.ncdc.noaa.gov/teleconnections/ Example of how oceans communicate with atmosphere: El Niño–Southern Oscillation (ENSO): higher than normal SSTs in the eastern equatorial Pacific Ocean. Higher than normal sea surface temperatures (SSTs) in the eastern equatorial Pacific Ocean. These higher SSTs have the potential to affect weather around the world by altering atmospheric circulation. The primary effect on North America is a strengthened jet stream. There is a fluctuation between unusually warm (El Niño) and cold (La Niña) conditions in the tropical Pacific; El Niño and La Niña typically recur every 2 to 7 years. Global effects of ENSO: El Niño warming brings drought to Australia, Indonesia, and neighboring countries. But the central Pacific and the west coast of South America are often inundated with heavy rains. These changes in the location and intensity of rainfall and associated latent heat release into the atmosphere lead to widespread changes in atmospheric circulation and weather patterns outside the tropical Pacific referred to as teleconnections. Greater likelihood of a major Atlantic hurricane striking the United States during La Niña versus El Niño years. During El Niño, primary production in the tropical Pacific, which accounts for 10% of the total in the world ocean, significantly decreases in response to weakened upwelling. This reduced productivity affects the mortality, fecundity, and geographic distribution of marine mammals, sea birds, and commercially valuable fish species. Elevated temperatures associated with strong El Niño events lead to bleaching of tropical corals. The most massive and widespread episode of bleaching occurred during the 1997–1998 El Niño, when 16% of the world’s reef-building coral died (superimposed on GW). Forest fires, like those that burned out of control over large drought-affected regions of Central America, the Amazon, and Indonesia during the 1997–1998 El Niño, result in catastrophic changes in ecosystem structure and function as habitat is destroyed and endemic populations are decimated. ENSO variability affects agriculture, power generation, fresh water resources, public health and safety (creates conditions favorable for the spread of diseases such as hantavirus, malaria, dengue fever, and cholera), forestry, fisheries, transportation, tourism, financial markets, and many other spheres of climate-sensitive human endeavors. Influence of mountains on climate: Rain shadow: In certain geographic areas, as air is forced to rise over a mountain in its path, it releases moisture* (it rains); this side of the mountain has luxurious vegetation. On the other side of the mountain is desert. *Explanation: for every 300m rise in elevation, temperature drops 1.5-3.0 º C. Since cold air holds less moisture than warm air, it rains. Effect of weather and climate on US economy, human health and quality of life: http://www.ncdc.noaa.gov/ Crop Moisture Stress Index (CMSI) Residential Energy Demand Temperature Index (REDTI) Air Stagnation Index U.S. Wildfires U.S. Wind Climatology Apparent Temperature Heat Stress Index U.S. Billion-Dollar Weather and Climate Disasters Northeast Index to Potential Ozone Exposure (provided by the NERCC) West Nile Virus Mosquito Crossover Dates* Classification and global distribution of biomes: Augustin de Candolle (French plant physiologist) drew the first world vegetation maps in 1855. These maps revealed that forest types appear to grow in belts that circle the earth. Climate (rainfall and temperature) is a major factor in determining growing conditions over large geographical areas. Geology, fire, soils, topography, etc., cause local variation to the overall growing conditions. A biome is defined by particular climatic conditions and specifically adapted vegetation. Terrestrial Biomes: Tundra Boreal forest Temperate forest Grasslands Chapparal (scrub land) Desert Tropical forest Tundra: Windy; cold (average temp –5 º C) low, treeless (too windy) vegetation (grass, sedge, shrubs like willows and alders) high latitudes and high altitudes brief summer (May-August) water is held as ice on soil surface and in soil for most of the year (Permafrost) productivity of tundra is 65 NPP for comparison, tropical rain forest is 900 NPP (NPP is net primary productivity NPP = Carbon produced in PS – Carbon used in cellular respiration measured in grams of carbon/m²/year roughly equal to the total amount of plant growth) Boreal forest: located just south of the tundra very cold winters; warm summers trees can survive but almost all species are needle-leaf types like pine, spruce, fir – not broad-leaf trees like maples and oaks The needle leaves are adapted to this environment in the following ways: thin leaves reduce heat and moisture loss, they are tough, stay on all year, do PS all year, and the cone shape of the tree easily sheds snow. Temperate Forest: located just below the boreal forest biome can be evergreen (aka needle-leaf) or can be deciduous (aka broad-leaf) hot summers; cool winters; precipitation varies but it is always enough to support tree growth Examples are the temperate rain forests of the PNW, giant redwood forests in CA, deciduous forests of Europe, eastern US, some parts of Asia (like Japan). Grasslands: The temperature of the grassland biome is the same as that of the temperate forest biome but, the amount of precipitation is different: there is less rain in the grassland biome; not enough to support tree growth. Grasses and forbs (herbs, ie, wildflowers) exist, the wetter the area the taller the grass. For example, short-grass prairie gets 40 mm/yr of rain and plants rarely exceed 0.5m in height; tall- grass prairie gets 80 mm/yr and plants can be > 2 m high. Chapparal: “Scrub lands” found in Israel, California coast, part of S. Africa, Australia. (LA and San Fransisco lie within the chapparal biome). Mild/wet winter; summer drought; “Mediterranean”. The summer drought is the key to shaping the vegetation-it prevents trees from getting established. Chapparal plants have certain adaptations to moisture stress: deep roots or widely spread roots and small, thick leaves with a waxy coating Desert: Deserts are areas where dry air descends: about 30 º N and S latitudes. Cloudless skies, sunny. Plants and animals must excel at water conservation. Tropical Forests: constant daily temperatures in soil, air, and water (from one month to the next; daily temperatures vary only +/- 2 º C) however, the temperature change from day to night is large: +/- 7 º C) rainfall ranges from 2000mm to 15,000mm per year depending on geographic location no winter or summer, but rainfall can be concentrated into a wet season followed by a dry season The length and intensity of the dry season determine what kind of tropical forest it is; there are three kinds of tropical forests: tropical rain forest (rains daily) (broad-leaved evergreen) tropical seasonal forest (2-4 month droughts) (semi-deciduous)\ tropical dry forest (up to 8 months of drought) (deep-rooted deciduous trees and shrubs)