Each year, dozens of typhoons initiate in the tropics of the Pacific Ocean and churn westward toward Asia. These whirling tempests pose a problem for communities along the entire northwestern Pacific, with the Philippines bearing the brunt of the battering winds, waves, and rain associated with typhoons. In 2013, for instance, deadly supertyphoon Haiyan directly struck the Philippines, killing more than 6,000 people.
“On average,” said Mitsuteru Sato, a professor at Hokkaido University, “the Philippines will be hit [by] about 20 typhoons a year.”
Though scientists have improved typhoon tracking over the past 20 years, errors for intensity-related metrics, like pressure and wind speed, have counterintuitively increased, Sato said. In other words, scientists today forecast intensity with less certainty than in decades past, in spite of sophisticated models and expensive meteorological satellites.
Studies suggest that by measuring the lightning occurrence number (the number of strokes from cloud to ground or cloud to ocean), scientists may be able to forecast just how intense a typhoon might be about 30 hours before a storm reaches its peak intensity, said Sato. Today Sato and colleagues are using an inexpensive, innovative network of automated weather stations that more accurately measure a typhoon’s lightning occurrence number to convert that information into a prediction of how intense an incoming storm might be.
As a typhoon’s thunderclouds rise high into the atmosphere, its water-rich updrafts force ice and water particles to collide and become either positively or negatively charged, explained Kristen Corbosiero, an atmospheric scientist at the University at Albany. Lightning is nature’s attempt to neutralize the charge differences.
Lightning is controlled by a typhoon’s track, seawater temperature, and other variables, said Sato. Determining how these factors affect the complex interplay between lightning and storm intensity is the goal of the new Pacific-centric lightning monitoring system designed to detect and geolocate much weaker lightning than detected by existing global lightning monitoring networks.
This system includes six stations residing on Philippine islands and five stations distributed throughout the northwestern Pacific region. Each station, which monitors an area of about 2,000 kilometers, comes equipped with several sensors that measure rain, very low frequency signals produced by lightning, and other weather-related phenomena. The off-grid stations use solar power, storing energy in batteries for overcast days. An internal computer sends data over 3G cellular networks. The cost for each station totals about $10,000, substantially less expensive than meteorological satellites.
Because this system should more accurately measure the number of lightning flashes, Corbosiero said, “it does certainly have potential to improve forecasts.”
“If We Can Make the Precise Predictions, We Can Save Lives”
Sato, Takahashi, and their colleagues in the Philippines hope to refine and begin applying the lightning detection and forecasting system within the next 1–2 years, as data arrive from the nascent network of stations.
The network’s focus on the Philippines is key to its value: The Philippines’ furious rainy season means more data. More data contribute to more precise forecasts about a storm’s strength at landfall. More accurate forecasts will give emergency managers the information they need to inform the public about the risks of rain, storm surges, and wind. Combined, rainfall and storm surges can cause more damage than winds alone, said Corbosiero.
Perhaps more important, improving the accuracy of forecasts will help people believe that a storm is coming, said Takahashi. “In many, many cases, the people don’t believe” forecasts, he said. “They don’t want to evacuate.”
An additional consideration, said Takahashi, is integrating alert systems with lightning monitoring and forecasting. In developed and developing countries alike, everyone has a smartphone. With smartphones, “we can distribute this precise information directly to the people,” he said, “and precise information is the necessary condition to make [the people] believe.”
“If we can make the precise predictions,” Takahashi said, “we can save [lives].”
—Alka Tripathy-Lang (@DrAlkaTrip), Science Writer