Global Patterns in Physical Conditions and Biomes — Quick Notes Weather/Climate section 4 due sep 8

Global patterns in physical conditions

Humboldt’s travels showed plant communities in similar climates look similar, despite different species; climate helps predict both species richness and appearance.

Climate patterns are driven by uneven solar energy input. The Equator is warmer because sunlight hits more directly there.
Two effects of solar-angle:
- Radiation is dispersed over a larger area near the poles.
- Radiation is concentrated on a smaller area at the Equator.
Direct sunlight at the Equator hits a smaller surface area; oblique sunlight near the poles hits a larger area and travels through more atmosphere, dissipating more energy.
The amount of sunlight hitting the Equator is fairly constant; at higher latitudes, seasons arise from the tilt of the Earth’s axis and its orbit.
Key angles and dates:
- Axial tilt: 23.5^{\circ}
- Solstices: NH summer and NH winter (longest/shortest days)
- Equinox: September equinox — 12 h day, 12 h night everywhere
The tilt remains fixed relative to the orbital plane, so seasonal changes come from the changing angle of sunlight with latitude.

Uneven heating drives global air and water circulation; primary pattern is the Hadley Cell.
The Earth operates with a 6-cell system: three circulation cells in each hemisphere (Hadley, Ferrel, Polar).
These cells distribute heat, drive weather systems, and determine surface wind patterns.
Poles (final diagram) indicate a cold, dry climate due to descending dry air.

Earth’s rotation deflects moving air masses to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.
Resulting large-scale winds:
- Trade winds: easterly winds blowing from about 30° toward and along the Equator (east to west).
- Westerlies: westerly winds around 60° latitude (west to east).
Deflection arises from rotation and conservation of angular momentum; affects both air masses and ocean currents.

Biomes: broad groups based on dominant life forms; many classification schemes exist. World Wildlife Fund classifications modernized to reflect conservation priorities.
Historically 14 terrestrial biomes; a 10-biome map is commonly used. Olson et al. (2001) expanded this to 867 distinct ecoregions,
each with a distinct assemblage of natural communities and species.
Purpose for conservation: maps guide global priorities and resource allocation, but are too coarse for regional planning.
Atlas of Global Conservation (Nature Conservancy): provides maps of biomes, ecoregions, habitats, and threats (habitat loss, climate change, pollution).
Ecoregion maps support biodiversity protection by identifying representative, unique, and highly diverse areas and by linking them to threats.

A systematic approach uses maps and data to target ecoregions that meet criteria (e.g., biome of interest, high mammal diversity, endangered vertebrates, habitat loss, few existing preserves).
GIS tools help identify where investments will yield the most conservation benefit ("bang for the buck").
Conservation planning benefits from data-rich resources like the Atlas of Global Conservation to inform strategy.

Global climate patterns arise from differential solar input and axial tilt, creating latitudinal heating gradients that drive Hadley circulation and wind patterns.
The Coriolis effect shapes trade winds and westerlies, influencing regional climates and biogeography.
Biomes categorize broad climate-driven life-form groups; ecoregions refine this into detailed units for conservation planning.
Conservation planning relies on integrated maps (biomes, ecoregions, habitats, threats) and GIS to target priorities effectively.