Two people have died following landslides in the resort of Santa Ana in Cagayan Province on northeastern Luzon Island, the Philippines, on Tuesday 7 November 2017. The deceased have been named as Albert Ravelo, 47, and Richard Perez, 23, both of whom were killed when mudslides struck their homes early in the morning. A total of seven houses and ten other structures have been destroyed in a series of landslips and floods in the town, caused by heavy rains associated with the onset of the Northern Monsoon. Landslides are a common problem after severe weather events, as excess pore water pressure can overcome cohesion in soil and sediments, allowing them to flow like liquids. Approximately 90% of all landslides are caused by heavy rainfall.
House destroyed by a landslide in Santa Ana in Cagayan on 7 November 2017. Gerlie Rambunay/Rappler.
Monsoons are tropical sea breezes triggered by heating of the land during the warmer part of the year (summer). Both the land and sea are warmed by the Sun, but the land has a lower ability to absorb heat, radiating it back so that the air above landmasses becomes significantly warmer than that over the sea, causing the air above the land to rise and drawing in water from over the sea; since this has also been warmed it carries a high evaporated water content, and brings with it heavy rainfall. In the tropical dry season the situation is reversed, as the air over the land cools more rapidly with the seasons, leading to warmer air over the sea, and thus breezes moving from the shore to the sea (where air is rising more rapidly) and a drying of the climate.
Diagrammatic representation of wind and rainfall patterns in a tropical monsoon climate. Geosciences/University of Arizona.
Southeast Asia has two distinct Monsoon Seasons, with a Northeast Monsoon driven by winds from the South China Sea during the Southern Hemisphere Summer and a Southwest Monsoon driven by winds from the southern Indian Ocean in the Northern Hemisphere Summer. Such a double Monsoon Season is common close to the equator, where the Sun is highest overhead around the equinoxes and lowest on the horizons around the solstices, making the solstices the coolest part of the year and the equinoxes the hottest.
The winds that drive the Northeast and Southwest Monsoons in Southeast Asia. Mynewshub.
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