Climate Flashcards
El Nino
Discuss the ENSO as a driver of climate in the South Pacific.
During El Nino, sea surface temperatures in the central and eastern Pacific Ocean warm, weakening the trade winds.
In the South Pacific this results in drier conditions, increased risk of droughts, and reduced tropical cyclone activity.
La Nina
Discuss the ENSO as a driver of climate in the South Pacific.
During La Nina, sea surface temperatures in the central and eastern Pacific Ocean cool, strengthening the trade winds.
This causes wetter conditions, leading to increased rainfall and more frequent tropical cyclones.
El Nino atmospheric and oceanic circulation patterns
The trade winds (usually east to west across the equatorial Pacific), weaken or reverse. The Walker Circulation, a large-scale atmospheric circulation in the tropics, weakens.
Warm water normally in the western Pacific moves eastward, leading to warmer sea surface temperatures in the central and eastern Pacific.
La Nina atmospheric and oceanic circulation patterns
Trade winds strengthen, and the walker circulation intensifies. Warm water moves westward, leading to colder sea surface temperatures in the central and eastern Pacific.
Atmospheric and ocean dynamics leading to cyclone formation
- Describe the atmospheric and ocean dynamic that leads to cyclone formation, and how the predominance of these conditions changes with ENSO and intensity may change with global warming.
Cyclones typically form over warm waters. As warm, moist air rises from the ocean surface, it creates a region of low pressure. Air from surrounding areas with higher pressure moves in to fill the space, and as it does, it also warms and rises. This helps to form cyclones. Moisture in the mid-levels of the atmosphere helps maintain the cyclone’s energy.
Impact of ENSO on cyclone activity:
- Describe the atmospheric and ocean dynamic that leads to cyclone formation, and how the predominance of these conditions changes with ENSO and intensity may change with global warming.
During El Nino, warmer sea surface temperatures in the central and eastern Pacific can shift cyclone activity eastward, so less around Australia and more towards Mexico and the US. The warmer water can provide more energy for cyclone formation, increasing the intensity of storms in the affected regions. During La Nina, cooler sea surface temperatures in the eastern Pacific and warmer conditions in the western Pacific increase cyclone activity in the western Pacific.
Impact of global warming on cyclone intensity:
- Describe the atmospheric and ocean dynamic that leads to cyclone formation, and how the predominance of these conditions changes with ENSO and intensity may change with global warming.
Global warming is increasing sea surface temperatures. With more heat and moisture available in the atmosphere, cyclones may become more powerful, producing stronger winds, heavier rainfall, and more flooding. As sea levels rise due to global warming, the impacts of cyclones could become more destructive. Coastal areas would be at greater risk of flooding even with less intense storms.
Impact of El Nino
- Discuss the impact of ENSO on the frequency and intensity of meteorological hazards, including fire, floods, and drought.
Drier conditions in regions such as Australia and Southeast Asia. There are fewer floods. The reduced rainfall and higher temperatures create ideal conditions for bushfires to start and spread. The weakening of the trade winds and shifting of rainfall patterns toward the eastern Pacific leave western Pacific regions with less moisture, leading to prolonged droughts that severely impact agriculture, water resources, and ecosystems. El Nino causes increased rainfall and flooding in the eastern Pacific, which are typically dry under normal conditions.
Impact of La Nina
- Discuss the impact of ENSO on the frequency and intensity of meteorological hazards, including fire, floods, and drought.
La Nina typically brings cooler and wetter conditions to regions like Australia which reduces the risk of bushfires. Increased rainfall and flooding in the western Pacific, affecting countries like Australia and Indonesia. The intensified trade winds push warm waters and moisture westward, leading to more tropical cyclones and heavy rainfall in these regions, which increases the flood risk. Drier conditions to the eastern Pacific and regions like South America. Countries like Chile and Peru experience reduced rainfall, leading to droughts and water shortages.
ENSO and hazard activity under global warming
- Discuss the impact of ENSO on the frequency and intensity of meteorological hazards, including fire, floods, and drought.
Fires may become more severe due to rising temperatures and drier conditions during El Nino years. Floods could intensify with La Nina events, as warmer oceans increase evaporation, leading to heavier rainfall. Droughts may become more frequent and prolonged in regions that are already prone to drying out under both El Nino and La Nina phases.
Annual timeframe (ENSO)
- Discuss annual (ENSO), 100’s of thousands of years (Milankovitch cycles), and 100’s of millions of years (plate tectonics super cycle) timeframe climate change drivers.
Short-term variability that impacts global weather patterns and regional climate, influencing rainfall, temperature, and extreme weather events like floods and droughts.
100’s of thousands of years (Milankovitch cycles)
- Discuss annual (ENSO), 100’s of thousands of years (Milankovitch cycles), and 100’s of millions of years (plate tectonics super cycle) timeframe climate change drivers.
Milankovitch cycles are long-term variations in Earth’s orbit and axial tilt that affect the distribution of solar energy received by Earth, driving glacial and interglacial periods over the past several hundred thousand years.
Long-term changes in Earth’s orbit and axial tilt that drive glacial and interglacial periods, significantly impacting the Earth’s ice cover and global temperatures.
- Eccentricity:
- Discuss annual (ENSO), 100’s of thousands of years (Milankovitch cycles), and 100’s of millions of years (plate tectonics super cycle) timeframe climate change drivers.
Changes in the shape of Earth’s orbit around the Sun (from more circular to more elliptical). Greater eccentricity results in more variation in the distance between Earth and the Sun, influencing the severity of seasons.
- Obliquity:
- Discuss annual (ENSO), 100’s of thousands of years (Milankovitch cycles), and 100’s of millions of years (plate tectonics super cycle) timeframe climate change drivers.
Changes in the tilt of Earth’s axis. A greater tilt increases seasonal contrasts, while a smaller tilt reduces the difference between summer and winter.
- Precession:
- Discuss annual (ENSO), 100’s of thousands of years (Milankovitch cycles), and 100’s of millions of years (plate tectonics super cycle) timeframe climate change drivers.
The wobble in Earth’s rotational axis, which affects the timing of seasons relative to Earth’s position in its orbit.
