Context: The coastal town of Malibu in California, the US is presently gripped in wildfires. The wildfires in the region are becoming more frequent and the wildfire season has lengthened, attributed to two major reasons- Santa Ana winds and Climate change.
Relevance of the Topic: Prelims: Geophysical Phenomenon- Santa Ana Winds
What are Santa Ana Winds?
- Santa Anas are dry, warm (often hot) local winds that blow westward through Southern California, toward the coast.
- The winds are usually seasonal, and typically occur between October and March and peak in December.
- Santa Ana winds are driven by differences in the atmospheric pressure.
- Santa Ana winds blow when high pressure builds over the Great Basin (area between the Rocky Mountains and Sierra Nevada) and the pressure is low over California’s coast.
- The difference in pressure triggers the movement of powerful winds from the Basin’s inland deserts, east and north of Southern California, over the mountains toward the Pacific Ocean.
- As they flow downwards and cross desserts, they become very dry, warm, and gain speed.
- Impact: The lack of humidity in Santa Ana winds dries out vegetation, making it highly inflammable. The wind also fan the flames and help spread them.
Role of Climate Change
- Wildfire season in California has lengthened in recent years in the past two decades and the yearly peak has shifted from August to July.
- The wildfires have also become more intense in the past few years.
- Five of the 10 largest California wildfires (over 20 years) occurred in 2020 alone.
- Rise in global temperatures over the years has led to warmer springs and summers, and early spring snow melts. Such conditions cumulatively cause longer and more intense dry seasons, putting more moisture stress on vegetation. As a result, forests have become more vulnerable to fires.