Global Climates and Biomes

Global Processes determine weather and climate Weather – Happens on a time scale of seconds to days Climate – the average weather that occurs in a given region over a long period of time (decades) Regional differences in temperature and precipitation help determine where earth’s biomes are located on the planet This determines which organisms can survive in particular regions of the earth. To understand these differences, you must understand the processes that affect the distribution of heat and precipitation across the globe.

Distribution of biomes

Processes that affect biome distribution Unequal heating of the Earth by the Sun Atmospheric convection currents Rotation of the Earth Earth’s orbit around the Sun on a tilted axis Ocean currents

Earth’s Atmosphere more densely packed closer to the surface Consists of 5 layers of gases kept in place by gravity. Because gravitational pull weakens as you move farther from the Earth, molecules are: more densely packed closer to the surface less densely packed farther from the surface

Troposphere Layer closest to the Earth’s surface Extends upwards for about 10 miles Densest layer of atmosphere Where weather occurs Air temperature decreases as you move higher into the troposphere

Stratosphere Directly above the troposphere Extends from about 10 to 31 miles upward Less dense than troposphere UV radiation reaches higher altitudes first and warms them which means that higher altitudes are warmer than lower altitudes Ozone (O3)- forms a layer in the stratosphere Very important because ozone absorbs most of the sun’s UV radiation This provides critical protection to organisms on the planet. Stratosphere

Unequal heating of the earth Causes of unequal heating Variation in the angle that the sun ray’s strike the surface Variation in amount of surface area that sun rays are distributed Some areas reflect more solar energy than others

Unequal Heating of the earth Albedo – The percentage of incoming sunlight that is reflected from a surface

Properties of Air The density and temperature of air determines its movement Less dense, warmer air rises Denser, colder air sinks

Properties of air Temperature of air affects how much water vapor it can hold Hot air holds more water vapor Cooler air holds less water vapor Saturation Point – the maximum amount of water vapor that can be in air at a given temperature.

Properties of Air What does this mean? Air will rise and fall based on the density Air will heat and cool based on the pressure This is called Adiabatic heating and cooling Air will hold or release water based upon temperature

Convection currents Atmospheric convection currents – global patterns of air movement that are initiated by the unequal heating of the Earth.

Formation of convection currents

Earth’s Rotation As Earth rotates, its surface moves much faster at the equator than in mid-latitude and polar regions. Earth’s tilting rotation is 23.5 degrees. The faster rotation speeds closer to the equator cause a deflection of objects that are moving directly north or south

Earth’s Rotation and the Coriolis Effect Earth’s rotation has an effect on directions of the prevailing winds Prevailing winds - a wind from the direction that is predominant at a particular place or season

Coriolis Effect Coriolis Effect- the deflection of an object's path due to Earth's rotation. an object that moves along a north-south path will undergo apparent deflection to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

The prevailing winds of the world are produced by a combination of atmospheric convection currents and the Coriolis effect. Hadley Cells – convection currents that cycle between the equator and 30 degrees North and South

Convection currents Hadley Cells: large-scale atmospheric convection cell air rises at the equator and sinks at medium latitudes, about 30° north or south. ITCZ (Intertropical Convergence Zone) occurs along the equator where there is intense sunlight Area between 2 Hadley Cells Intense thunderstorm activity

Rain Shadow Warm, humid air, moves inland from the oceans & hits the windward side of mountains it begins to rise & cool causing precipitation the dry cooler air continues to cross the mountains & experience heating as it descends. This creates distinct climates on both sides of mountains.

Variations in Climate Determine the Dominant Characteristics of Each Organism in each Biome Climate affects the distribution of species around the globe. Organisms possess distinct growth forms due to adaptations to local temperature and precipitation patterns.