Scientists from NASA and the U.S. National Oceanic and Atmospheric Administration (NOAA) will spend July in Costa Rica conducting a field study intended in part to test the ability of remote sensing satellites to help unravel the poorly understood early phase of hurricane development.
NASA’s high-flying ER-2, a scientific research aircraft that can fly up to 21.3 kilometers high, will be dispatched from San Jose, Costa Rica, throughout the month to fly over the seasonal waves of moist tropical air that circulate over the eastern Pacific Ocean during hurricane season.
The ER-2 will act like a “virtual satellite,” observing the tropical air waves and their disorganized clusters of thunderstorms from altitudes of 19,800 meters to 21,300 meters , using instruments similar to those on existing NASA satellites, said meteorologist Ramesh Kakar of NASA Headquarters, who leads weather research within the space agency’s Science Directorate.
Tropical waves are common during hurricane season in the tropical regions of the Atlantic and Pacific o ceans. Only about one in every 10 will grow into a tropical depression — a persistent cluster of thunderstorms that can sometimes develop into a hurricane, according to NOAA and NASA scientists. At the moment hurricane forecasters cannot reliably predict which of these waves will develop into depressions, the scientists said.
The ER-2 will examine the tropical waves and surrounding atmosphere with six instruments designed to take measurements similar to those from NASA’s Tropical Rainfall Measuring Mission satellite, the Aqua and Terra Earth-observing satellites and the agency’s forthcoming CloudSat radar satellite, Kakar said.
While the ER-2 is flying over the tropical wave, at least one of NOAA’s two P-3 hurricane research planes will fly through the moist tropical air wave at an altitude of 3,000 meters to 4,300 meters . The P-3s will make direct measurements of temperature, moisture, precipitation and other factors. “We will compare what we are measuring [from the ER-2] to see if it is not too different from what the aircraft is measuring in the storm,” Kakar said.
NOAA and NASA scientists will conduct the study together with scientists from the Costa Rican Centro Nacional de Alta Tecnolog�a (National Center for Advanced Technologies).
NOAA is interested in the early phase of hurricane development because it operates the U.S. National Hurricane Center in Miami, where forecasters attempt to predict the track and intensity of developing storms. Emergency management officials in the United States and the Caribbean Sea area rely on these forecasts to decide whether or not to issue coastal evacuation orders.
For NOAA, the Costa Rica mission is the first step in a multiyear effort by the agency to improve predictions of storm intensities by accumulating observations at all phases of storm development, including the relatively little-studied tropical wave phase.
“We’re pretty good at forecasting storm tracks. We’re not so good at forecasting intensity changes,” said meteorologist Robert Rogers, field program director at the Hurricane Research Division in Miami, which tests sensors and prediction techniques for U.S. forecasters.
Other NOAA scientists will incorporate the results of the Intensity Forecast Experiment into a next-generation, forecasting model called the Hurricane Weather Research and Forecasting model now in development, Rogers said. This new model is meant to improve the intensity and precipitation forecasts issued by the National Hurricane Center. It will depict the atmosphere in blocks of data approximately 10 kilometers across compared to 15-17 kilometers for the existing model, Rogers said.
The goal of identifying which tropical waves are likely to develop into tropical depressions became critical when the National Hurricane Center shifted to issuing five-day forecasts instead of three-day forecasts, Rogers said.
In a matter of hours, tropical waves can develop into tropical depressions marked by persistent thunderstorms. “If you weren’t capable of predicting development of that system by day three , you have no way of forecasting the hurricane by day five ,” Rogers explained.
As computerized forecasting models become more detailed, the role of NOAA’s satellite observations in such forecasting is likely to grow, Rogers predicted. “If you can run your model at resolutions comparable to the resolutions of your observations, then you can really start to use those observations in your model,” he explained. At the moment, much of the data from NOAA’s polar orbiting and geosynchronous satellites is more detailed than demanded by the model.
“There’s so much data from the satellites that we’re not able to use,” Rogers said. “If anything, satellites will become more relevant.”