Earth’s deadliest natural disaster so far in 2013 is the deadly flooding in India’s Himalayan Uttarakhand region, where torrential monsoon rains have killed at least 556 people, with hundreds more feared dead. At least 5,000 people are missing. According to the Indian Meteorological Department, Uttarakhand received more than three times (329%) of its normal June rainfall from June 1 – 21, and rainfall was 847% of normal during the week June 13 – 19. Satellite estimates indicate that more than 20″ (508 mm) or rain fell in a 7-day period from June 11 – 17 over some regions of Uttarakhand, which lies just to the west of Nepal in the Himalayas. According to Dr. Dave Petley’s Landslide Blog, Earth’s deadliest landslide since the August 2010 Zhouqu landslide in China hit Uttarakhand’s Hindu shrine in Kedarnath, which is just a short distance from the snout of two mountain glaciers. The shrine is an important pilgrimage destination this time of year, and was packed with visitors. Hindu devotees visit Uttarakhand in huge numbers for the char-dham yatra, or a pilgrimage to the four holy sites of Gangotri, Kedarnath, Yamnotri and Badrinath. Apparently, heavy rainfall triggered a collapse event on the mountain above Kedarnath, which turned into a debris flow downstream that struck the town. The main temple was heavily damaged, and numerous building in the town were demolished.

According to Aon Benfield’s May Catastrophe Report, Earth’s deadliest natural disasters of 2013 so far:

Winter weather, India, Banglaadesh, Nepal, 1/1 – 1/20, 329 deaths
Earthquake, China, 4/20, 196 deaths
Flooding, Southern Africa, 1/10 – 2/28, 175 deaths
Flooding, Argentina, 4/2 – 4/4, 70 deaths
Flooding, Kenya, 3/10 – 4/30, 66 deaths

Figure 1. Indo-Tibetan Border Police (ITBP) arrive to rescue stranded Sikh devotees from Hemkunt Sahib Gurudwara, a religious Sikh temple, to a safe place in Chamoli district, in northern Indian state of Uttarakhand, India, Monday, June 17, 2013. AP photo.

Figure 2. Satellite-estimated rainfall for the 7-day period June 11 – 17, 2013, from NASA’s TRMM satellite exceeded 20 inches (508 mm) over portions of India’s Uttarakhand province, leading to catastrophic floods. Image credit: NASA.

An unusually early arrival of the monsoon
The June 2013 monsoon rains in Uttarakhand were highly unusual, as the monsoon came to the region two weeks earlier than normal. The monsoon started in South India near the normal June 1 arrival date, but then advanced across India in unusually rapid fashion, arriving in Pakistan along the western border of India a full month earlier than normal. Fortunately, no more heavy rain is expected in Uttarakhand over the next few days, as the monsoon will be active only in eastern India. Heavy rains are expected again in the region beginning on June 24. Wunderblogger Lee Grenci’s post, Summer Monsoon Advances Rapidly across India: Massive Flooding Ensues, has more detail on the meteorology of this year’s monsoon. There is criticism from some that the devastating floods were not entirely a natural disaster–human-caused deforestation, dam building, and mining may have contributed. “Large-scale construction of dams and absence of environmental regulations has led to the floods,” said Sunita Narian, director general of Delhi based advocacy group Centre for Science and Environment (CSE).

Figure 3. The summer monsoon arrived in southwest India right on schedule (June 1) in South India, but it spread northward much faster than usual, reaching Pakistan a full month earlier than normal. Solid green contours indicate the progress of the 2013 summer monsoon (each contour is labeled with a date). You can compare this year’s rapid advance to a “normal” progression, which is represented by the dashed, red contours (also labeled with dates).

Monsoons in India: a primer
Disastrous monsoon floods are common in India and surrounding nations, and 60,000 people–an average of 500 people per year–died in India due to monsoon floods between 1900 – 2012, according to EM-DAT, the International Disaster Database. The monsoon occurs in summer, when the sun warms up land areas more strongly than ocean areas. This happens because wind and ocean turbulence mix the ocean’s absorbed heat into a “mixed layer” approximately 50 meters deep, whereas on land, the sun’s heat penetrates at a slow rate to a limited depth. Furthermore, due to its molecular properties, water has the ability to absorb more heat than the solid materials that make up land. As a result of this summertime differential heating of land and ocean, a low pressure region featuring rising air develops over land areas. Moisture-laden ocean winds blow towards the low pressure region and are drawn upwards once over land. The rising air expands and cools, condensing its moisture into some of the heaviest rains on Earth–the monsoon. Monsoons operate via the same principle as the familiar summer afternoon sea breeze, but on a grand scale. Each summer, monsoons affect every continent on Earth except Antarctica, and are responsible for life-giving rains that sustain the lives of billions of people. In India, home for over 1.1 billion people, the monsoon provides 80% of the annual rainfall. The most deadly flooding events usually come from monsoon depressions (also known as monsoon lows.) A monsoon depression is similar to (but larger than) a tropical depression. Both are spinning storms hundreds of kilometers in diameter with sustained winds of 50 – 55 kph (30 – 35 mph), nearly calm winds at their center, and generate very heavy rains. Typically, 6 – 7 monsoon depressions form each summer over the Bay of Bengal and track westwards across India.

The future of monsoons in India
A warming climate loads the dice in favor of heavier extreme precipitation events. This occurs because more water vapor can evaporate into a warmer atmosphere, increasing the chances of record heavy downpours. In a study published in Science in 2006, Goswami et al. found that the level of heavy rainfall activity in the monsoon over India had more than doubled in the 50 years since the 1950s, leading to an increased disaster potential from heavy flooding. Moderate and weak rain events decreased during those 50 years, leaving the total amount of rain deposited by the monsoon roughly constant. The authors commented, “These findings are in tune with model projections and some observations that indicate an increase in heavy rain events and a decrease in weak events under global warming scenarios.” We should expect to see an increased number of disastrous monsoon floods in coming decades if the climate continues to warm as expected. Since the population continues to increase at a rapid rate in the region, death tolls from monsoon flooding disasters are likely to climb dramatically in coming decades. However, my greater concern for India is drought. The monsoon rains often fail during El Niño years, and more than 4.2 million people died in India due to droughts between 1900 – 2012. Up until the late 1960s, it was common for the failure of the monsoon rains to kill millions of people in India. The drought of 1965 – 1967 killed at least 1.5 million people. However, since the Green Revolution of the late 1960s–a government initiative to improve food self-sufficiency using new technology and high-yield grains–failure of the monsoon rains has not led to mass starvation in India. It is uncertain whether of not the Green Revolution can keep up with India’s booming population, and the potential that climate change might bring more severe droughts. Climate models show a wide range of possibilities for the future of the Indian monsoon, and it is unclear at present what the future might hold. However, the fact that one of the worst droughts in India’s history occurred in 2009 shows that serious droughts have to be a major concern for the future. The five worst Indian monsoons along with the rainfall deficits for the nation:

1) 1877, -33%
2) 1899, -29%
3) 1918, -25%
4) 1972, -24%
5) 2009, -22%

References
Goswami, et al., 2006, ” Increasing Trend of Extreme Rain Events Over India in a Warming Environment”, Science, 1 December 2006:Vol. 314. no. 5804, pp. 1442 – 1445 DOI: 10.1126/science.1132027

Wunderground’s climate change blogger Dr. Ricky Rood wrote a nice 3-part series about the challenges India faces due to climate change after he completed a 2009 trip there.

Jeff Masters

from:    http://www.wunderground.com/blog/JeffMasters/show.html