the average or normal weather of a particular large region of Earth's surface over a year's time mainly involves the region's 1) amount of available water and 2) temperature
1. Water Cycle - 98% of Earth's water is found in oceans; 2% in glaciers, rivers, lakes, clouds, and ground - evaporation and transpiration both add water vapor to the atmosphere - condensation of water vapor into liquid forms clouds, which lead to precipitation - precipitation returns water to Earth as either: - Runoff - excess water that can not infiltrate ground - water collects as rivers and streams - Groundwater - infiltration of water into the Earth - zone of aeration, pores in rock filled with air - zone of saturation, pores in rock filled with water - the water table is the boundary between the two zones - Infiltration – the downward movement of water through the soil. - porosity - the percent of open space in a given volume of rock or soil - porosity increases with increasing sediment size or sediment roundness - permeability = the relative ease at which water flows through a rock or soil - permeability increases with increasing sediment size or sediment roundness
- capillarity - the upward movement of water from the water table toward plant roots - capillarity increases as sediment size decreases
2. Water Budget - a mathematical system accounting for an area's yearly water supply - involves water in the upper 100 mm of soil = root zone * NOT GROUNDWATER* - water added to soil through precipitation (P) - water lost from soil through evapotranspiration (E ) 1. Recharge - water added to storage (0 —> 100) 2. Usage - water removed from storage (100— > 0) 3. Deficit - storage is zero but potential transpiration requires more water 4. Surplus - storage is 100 with excess water becoming runoff
- ratio of P/E is a good indication of an area's climate with respect to water availability 0.4 or lower = arid climate 0.8 to 1.2 = subhumid climate 0.4 to 0.8 = semiarid climate over 1.2 = humid climate
3. Insolation and Temperature - the electromagnetic spectrum is the total amount of energy given off by the sun - many short-wave energies (ex: X-rays) are absorbed by the atmosphere's ozone layer - of the insolation that actually strikes Earth, visible light is the most abundant - this short-wave energy is mostly used to heat the surface of Earth and its atmosphere - as the angle or duration of insolation increases, temperature increases - due to tilt of Earth's axis, angle and duration of insolation vary with two factors:
1. Latitude - as latitude increases, angle of insolation decreases: temp decrease - as latitude decreases, angle of insolation increases: temp increase'
2. Season - summer solstice - N. Hemisphere tilted toward sun - increased insolation and longer daylight hours
- winter solstice - N. Hemisphere tilted away from sun - decreased insolation and shorter daylight hours
- equinox - N. Hemisphere tilted neither toward or away - equal insolation and equal day/night hours
4. Terrestrial Radiation - long wave energy (infrared heat) given off by Earth in response to receiving insolation - terrestrial radiation can not pass beyond atmosphere, so atmosphere retains this heat - this heat warms the Earth's atmosphere - if atmosphere heats up too much, leads to Greenhouse Effect (= global warming) - there is a time delay or lag between when Earth receives insolation (short-wave) and it gives off terrestrial radiation (long wave) 1. Daily temperature delay = time lag between maximum insolation (12:00 noon) and maximum daily temperature (about 2:00 PM) 2. Seasonal temperature delay = time lag between maximum insolation (June) and maximum yearly temperature (about August) - radiative balance is when the amount of energy gained by the Earth (insolation) equals the amount of energy lost by the Earth (terrestrial radiation) - measurements show Earth is not in radiative balance
5. Other Factors Affecting Climate 1. Altitude - as altitude increases, the average temperature decreases - thus, two locations at the same latitude but different altitudes may experience very different climates 2. Latitude - as latitude increases, the average temperature decreases - mid latitudes regions (ex: New York State) are called temperate 3. Mountain Ranges - mountain ranges can modify climate by controlling and changing wind patterns - on windward side: climate usually cold and wet - on leeward side: climate usually warm and dry 4. Proximity to large bodies of water - water heats up slowly and cools down slowly because of its high specific heat a) locations next to water = maritime climate - in summer, water is cooler and in winter, water is warmer - yearly temperatures are moderate (= cooler summer and warmer winter) b) locations far from water = continental climate - in summer, no cool water and in winter, no warm water - yearly temperatures are extreme (= hotter summer and colder winter) 5. Ocean currents - bring cool or warm water that affects local weather of coastal locations - El Nino - cold water to South America replaced with warm water - La Nina - cold water brought to eastern Pacific 6. Planetary wind belts - affect local moisture and temperature patterns - high pressure at N and S Poles; low pressure at Equator - if winds prevail from tropical area, warm and moist (mT) air mass is seen - if winds prevail from polar area, cold and dry (cP) air mass is seen - Coriolis effect bends winds to right (east) in N. Hemisphere