Researchers construct a model of impact for El Nino / La Nina events

The 1997 El Nino seen by TOPEX/Poseidon. 

Credit: NASA

A small team made up of researchers from the U.S. and Europe has constructed a model that helps map parts of the world that are most at risk of flooding due to El Niño/La Niña events.

In their paper published in Proceedings of the National Academy of Sciences, the team describes how they compared weather data over the past half century with economic impacts of actual floods to create a model that may soon be used to help predict flooding events in the future.

By now, most everyone has heard about El Niño/La Niña weather events, El Niño is where warm water west of South America causes more rain to fall in some places.

La Niña is where the same waters are cooler than normal resulting in different changes to rain patterns.

Perhaps less well known is that such events have a worldwide impact, causing more flooding than normal in some parts of the world and less in others.

Ofen the flooding results in damage to property and loss of life, thus it would be a good thing if forecasts could be made, warning people in areas most at risk.

Unfortunately, up till now, such forecasts have not been available because such events don't always cause the same types of flooding in the same places.

In this new effort, the researchers sought to provide a model for building such a forecasting ability by using data over a long period of time.

"El Niño Southern Oscillation (ENSO) is the most dominant interannual signal of climate variability and has a strong influence on climate over large parts of the world."

"In turn, it strongly influences many natural hazards (such as hurricanes and droughts) and their resulting socioeconomic impacts, including economic damage and loss of life."

"However, although ENSO is known to influence hydrology in many regions of the world, little is known about its influence on the socioeconomic impacts of floods (i.e., flood risk)."

The research team obtained weather data for the years 1959 to 2000, pulling out periods of El Niño/La Niña weather events which they then compared with reports of damage due to flooding.

Next they compared those results with flood reports during normal times and used what they found to create a model.

The model showed that during El Niño events, 34 percent of the Earth's surface had higher or lower than normal amounts of flooding, that number jumped to 38 percent for La Niña weather events.

The model also showed which parts of the planet are more susceptible on average, to flooding due to such events.

The Southwest in the U.S. for example and parts of South America, both experience more flooding during El Niño events, while places like the Sahel in Africa, and most of Australia experience less.

The research team acknowledges that their model is still in its infancy but believe that over time, as more research is conducted, it will improve to the point that it will be useful in helping areas prepare for flooding during El Niño/La Niña weather events.

More information: Strong influence of El Niño Southern Oscillation on flood risk around the world, PNAS, Philip J. Ward, DOI: 10.1073/pnas.1409822111

TRMM satellite: System 91W's deadly Philippine flooding calculations

NASA/JAXA's TRMM satellite data was used to calculate the extremely high rainfall totals of over 1,168 mm (about 46 inches) that fell from Jan. 10-17, 2014, near northeastern Mindanao, Philippines. 

Credit: SSAI/NASA, Hal Pierce

People in the southern Philippines are used to heavy rainfall this time of the year but rainfall totals have recently been exceptionally high.

A tropical low known as System 91W, located northeast of Mindanao has been an almost permanent feature on weather maps for the past week.

NASA and the Japan Aerospace Exploration Agency's TRMM satellite has provided data on rainfall and flooding that was used to create a map of the event.

System 91W has caused nearly continuous rain in the area of northeastern Mindanao triggering floods and landslides that have caused the reported deaths of 34 people.

The Tropical Rainfall Measuring Mission or TRMM satellite data was used in a TRMM Multi-Satellite Precipitation Analysis (TMPA), produced at NASA's Goddard Space Flight Center, in Greenbelt, Md.

The TMPA combines the rainfall estimates generated by TRMM and other satellites. The analysis was done for the period from January 10-17, 2014.

Extremely high rainfall totals of over 1,168 mm (about 46 inches) for that week were found near northeastern Mindanao. This past Monday, January 13, a landslide on Dinagat Island caused the deaths of six people in this area.

Heavy rain amounts (calculated from satellite data), flood inundation calculations (from a hydrological computer models) and landslide potential maps are updated as often as every three hours globally.

Results are shown at the "Global Flood and Landslide Monitoring" TRMM web site pages: trmm.gsfc.nasa.gov.

System 91W, known locally as "Agaton," continues to drop heavy rainfall on parts of the Philippines, and warnings remained in effect on January 17-18.

Philippines warnings in effect include Public Storm Warning Signal #1 for southern Leyte, Surigao del Norte and Sur, Siargao Island, Dinagat Province, Agusan del Norte and Sur, Davao Oriental and Compostella Valley.

On January 17 at 1500 UTC/10 a.m. EST, System 91W was centered near 9.7 north latitude and 127.6 east longitude, about 370 nautical miles/425.8 miles/685.2 km east-northeast of Zamboanga, Philippines.

Satellite data indicated that convection continued to flare up along the northern quadrant of the storm. The Joint Typhoon Warning Center gives System 91W a high chance for becoming a tropical depression in the next 24 hours.

Residents of the Philippines should be on guard for more heavy rainfall, flash floods, and mudslides as System 91W lingers.

Floodwater inundates cotton crops: NSW Australia

Floodwater inundates cotton crops around the northern New South Wales town of Moree, Australia. 

Moree has been cut off by floodwaters, isolating up to 10,000 people.

NASA Image: Hudson River Flood Sept 2011

This NASA satellite image, obtained by Reuters on September 2, 2011, and taken August 31, 2011, shows the Hudson River (C) flowing into New York Harbour, filled with sediment from upriver streams and rivers affected by the rains of Hurricane Irene. 

Residents of several U.S. Northeast states approached the Labour Day holiday weekend mired in mud and stuck in the dark on Thursday nearly a week after Hurricane Irene swallowed parts of the region with flooding.

(Photo: Reuters)

Hurricane Irene: Hurricanes explained

Hurricanes start when strong clusters of thunderstorms drift over warm ocean waters.
In the Atlantic and eastern Pacific they are called hurricanes, but in the western Pacific they are called typhoons.

In the Bay of Bengal and Indian Ocean they are known as cyclones.

The very warm air from the storm combines with the moist ocean surface and begin rising. This creates low pressure at the surface.

As trade winds hit those within the storm, the whirling winds cause the storm to start spinning. Rising warm air leaves low pressure above the surface.

Air rises faster and faster to fill this low pressure, in turn drawing more warm air off the sea and sucking cooler, drier air downwards.

As the storm moves over the ocean it picks up more warm, moist air. Wind speeds start to increase as more air is sucked into the low-pressure centre.

It can take hours or several days for a depression to grow into a fully-formed hurricane.

Hurricanes are made up of an eye of calm winds and low pressure surrounded by a spinning vortex of high winds and heavy rainstorms.

When a hurricane hits land it often has devastating effects.

The Saffir-Simpson scale was devised to measure hurricanes around the Americas and is increasingly used to categorise typhoons and cyclones, too, although some regions still use different scales.

The effects:
Category 1:

• Minor flooding
• Little structural damage
• Storm surge 1.2-1.5m above normal

Category 2:

• Roofs damaged
• Some trees damaged
• Storm surge 1.8-2.4m above normal

Category 3:

• Houses damaged
• Severe flooding
• Storm surge 2.7-3.7m above normal

Category 4:

• Some roofs destroyed
• Major structural damage to houses
• Storm surge 4-5.5m above normal

Category 5:

• Serious damage to buildings
• Severe flooding further inland
• Storm surge more than 5.5m above normal

NASA ASTER Image: Flooding in Pakistan

Though many areas in northwest Pakistan were bracing for heavy rain and additional flash flooding on August 4, 2010, the city of Kheshgi, in northwest Pakistan, had clear skies.

This image, taken by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA’s Terra satellite reveals a city awash in flood water.

Thick with mud, the Kabul River is pale green in this false color image. Clearer water is dark blue. The river flows through its usual channel, but in places, water seeps over the channel and across the landscape. The buildings and roads of Kheshgi are silver. Spots of turquoise blue—shallow, muddy water or water-logged ground—covers several sections of the city.

On the south side of the Kabul River, water flows down the hills, washing over neighborhoods. The bare ground in the hills is brown and tan. Plant-covered land, red in this image, is divided into long, narrow rectangles, pointing to agriculture. Geometric shapes under the water near the river are probably submerged fields of crops. Thousands of acres of crops had been lost in floods throughout Pakistan, said the United Nations.

Kheshgi is in the Nowshera district in the Khyber Pakhutnkhwa province. As of August 2, Khyber Pakhutnkhwa was the hardest hit province in Pakistan, said the United Nations, and Nowshera was the most impacted district in the province. Nowshera reported 500,000 people displaced with 161 dead, said the Government of Khuber Pakhtunkhwa.

Chile Earthquake: Tsunami reaches Japan

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Borneo mega-dams proposal raises fears for tribes, wildlife

A massive tract of Borneo jungle, an area the size of Singapore, will soon disappear under the waters of the Bakun dam, a multi-billion-dollar project nearing completion after years of controversy.

The dam, which forced thousands of indigenous people off their ancestral lands, has struggled through setbacks and delays since its approval in 1993, as well as fierce criticism over its environmental impact.

But even before the turbines of the 2.2 billion dollar hydro-electric facility begin to turn, activists have sounded the alarm over plans for 12 more mega-dams on Malaysia's half of Borneo which it shares with Indonesia.

Balan Balang, an elderly chief of the Penan tribe, sighs as he talks of the Murum dam, the first of the dozen dams envisioned for Sarawak state, which will drown the hunting grounds and burial sites of his people.

"This government is very bad. In the old days people would fight us using machetes or spears. But now they just sign away our lives on pieces of paper," said the headman, who sports the elongated earlobes distinctive to his tribe.

"My people never want to leave our place. We want to die in our place," he said, after a long journey from his rainforest home to seek help from indigenous lawyers in Miri, a coastal town in Malaysian Borneo.

Human rights activists are intent on avoiding a repeat of the botched relocation of some 15,000 indigenous people in the Bakun area who they say have made an unhappy transition to life in resettlement areas.

Balan Balang's village is outside the Murum resettlement area, but some 1,500 people -- mostly Penan but including another of Sarawak's tribes, the Kenyah -- will be forced to abandon their homes for an uncertain future.

The chief, who is not sure of his birth date but reckons he is "between 70 and 80 years old", has seen much hardship during his long life.

As a young boy he watched fearfully as Japanese warplanes flew overhead during the World War II occupation, while rampant logging later degraded the jungles where his people forage for food, wild game, and materials for shelter.

"Now the rivers are all polluted. The wildlife has slowly disappeared -- wild boar, deer, gibbons. Even the broad-leafed plants that we use for roofing, and rattan which we use to make mats and baskets, is gone," he said.

But what brought him to Miri are new threats to his way of life, the dam project as well as plantation firms who want to clear what is left of the jungle and grow palm oil and foreign timber species.

"Our people oppose our area being included for the dam because that's where we come from, our ancestors lived and died and were buried there. For us we have no other place, that is our only place," he said.

Global Warming: Flooding in Venice

Flooding: Half of Venice underwater

The city has for years been wrestling with the problems posed by the threat of rising sea levels. Last year local authorities confirmed they were looking at a scheme to raise the city's buildings to meet the problem.

Much of the historic Italian city of Venice, including St. Mark's Square, was underwater Monday following a meteorological depression combined with natural tide waters, officials said.

The tide monitoring centre said 45 percent of the Renaissance city was swamped when the lagoon rose 131 centimetres (more than four feet).

Venice was flooded 50 times between 1993 and 2002, with the worst 'acqua alta' on November 4, 1966, when the city was submerged by 1.94 metres of water amid catastrophic flooding throughout the country.

In February 1986, levels reached 1.58 metres above normal, and in December 2008 waters surged 1.56 metres.

The city has for years been wrestling with the problems posed by the threat of rising sea levels. Last year local authorities confirmed they were looking at a scheme to raise the city's buildings to meet the problem.

Under Operation "Rialto", local officials and engineers were looking at using piston-supported-poles placed at the bottom of each structure to lift buildings by up to a metre.

In April 2007, the United Nations cultural organisation UNESCO warned that Venice was one of its designated World Heritage sites that was threatened by climate change.