QuikSCAT image of Tropical Storm Parma.

On October 5, 2009, Typhoon Parma was parked over the South China Sea off the northern tip of Luzon Island, the Philippines. Though the storm had degraded into a tropical storm, with relatively weak winds of 100 kilometers per hour (60 miles per hour or 55 knots), Parma had almost no forward motion, said the Joint Typhoon Warning Center. This image, made from data from NASA’s QuikSCAT satellite taken on October 5, shows that the storm was primarily over open water, but areas of rain and wind still cover parts of Luzon and Taiwan.

The image illustrates windspeed, in color, and wind direction, with small barbs. Areas of heavy rain are depicted with white barbs. Parma has a circular core of strong winds with a weaker eye region. QuikSCAT monitors wind speed over the ocean by sending pulses of microwave energy through the atmosphere to the ocean and measuring the energy that bounces back from the wind-roughened surface. The energy of the microwave pulses changes depending on wind speed and direction, giving scientists a way to monitor wind around the world. Intense rain rippling on the ocean’s surface and the relative rarity of the extreme winds seen in a tropical cyclone make it difficult to accurately measure wind speeds above 50 knots using the satellite scatterometer. QuikSCAT images provide, instead, a valuable picture of the wind structure within the storm.