Weather and climate researchers are gaining unprecedented insights into rainfall-producing cloud systems over the tropical land masses and oceans from instruments flying aboard the Tropical Rainfall Measuring Mission -- a joint NASA and Japanese Space Agency spacecraft. Initial information received from the rainfall-measuring observatory is exceeding expectations for accuracy and resolution, scientists say.
Today, NASA is releasing the first images from the spacecraft's Lightning Imaging Sensor, managed by NASA's Marshall Space Flight Center in Huntsville, Ala., along with images from four other instruments flying aboard the craft. In a preliminary finding, images from the lightning sensor indicate that 98 percent of lightning occurs over land and very little occurs over the oceans.
"We believe that the increased lightning activity over land is primarily due to enhanced convection -- continual overturning of the atmosphere that occurs as water, evaporated from the Earth's surface, carries excess heat energy into the upper atmosphere," said Dr. Hugh Christian, the principal investigator for the Lightning Imaging Sensor at the Global Hydrology and Climate Center in Huntsville.
"Specifically, convection is just much stronger over land. This results in greater ice production and, consequently, more lightning," said Christian.
"The beauty of this mission is that the unique array of instruments aboard the spacecraft allows us to test this hypothesis time and again," he said. "This mission will enable us to gain fundamental insights into the properties of these convective storms and thus better estimate the effects on global weather patterns."
The small, sophisticated lightning sensor looks at both day and night cloud-to-ground, cloud-to-cloud and intra-cloud lightning, as well as its distribution around the globe.
The sensor is helping to pave the way for a future space-based lightning mapper that could deliver day and night lightning information to a forecaster's workstation within 30 seconds of occurrence -- providing an invaluable tool for storm "nowcasting" and giving people more advance warning of severe storms.
The Lightning Imaging Sensor was developed at Marshall with contributions from Lockheed Martin in Palo Alto, Calif., and Kaiser Electro-Optics Inc., in Carlsbad, Calif.
As part of the Tropical Rainfall Measuring Mission, the Lightning Imaging Sensor will contribute to NASA's Earth Science Enterprise, aimed at gaining a better understanding of how the Earth functions as a system, and how this system is being influenced by the rapid growth of the human population.
The suite of instruments was launched on an H-II rocket from the Tanegashima Space Center in Tanegashima, Japan, on Nov. 27, 1997, and is scheduled to collect information for three years. The Tropical Rainfall Measuring Mission is dedicated to studying the properties of rain that falls within a zone from 35 degrees above to 35 degrees below the equator.