3D Global Precipitation Measurement
March 25, 2014

First Images From NASA-JAXA Global Precipitation Measurement Core Observatory

April Flowers for redOrbit.com - Your Universe Online

The first images captured by the newest Earth-observing satellite operated as a joint mission between NASA and the Japan Aerospace Exploration Agency (JAXA) have been released. The images are from the Global Precipitation Measurement (GPM) Core Observatory, which launched on February 27 of this year.

The focus of the image set covers precipitation falling inside a cyclone that occurred on March 10 over the northwest Pacific Ocean, about 1,000 miles east of Japan. The GPM Core Observatory's two instruments — JAXA's Dual-frequency Precipitation Radar (DPR), which imaged a three-dimensional cross-section of the storm; and, NASA's GPM Microwave Imager (GMI), which observed precipitation across a broad swath — collected the data and imagery.

"It was really exciting to see this high-quality GPM data for the first time," said GPM project scientist Gail Skofronick-Jackson at NASA's Goddard Spaceflight Center. "I knew we had entered a new era in measuring precipitation from space. We now can measure global precipitation of all types, from light drizzle to heavy downpours to falling snow."

The first images of the cyclone make the new satellite's capabilities clear. The March 10 cyclone was an "extra-tropical" cyclone, which happens when masses of warm air collide with masses of cold air north or south of the tropics. Storm systems such as these are capable of producing rain, snow, ice, high winds, and other severe weather. The images reveal the warm front ahead of the cyclone associated with a broad area of precipitation — rain — with a narrower band of precipitation associated with the cold front trailing to the southwest. In the northern reaches of the storm, snow is seen.

[ Watch the Video: GPM’s Stormy New View ]

NASA's GMI instrument has 13 channels that measure natural energy radiated by the surface of the planet, as well as by precipitation itself. Microwave energy is affected differently by liquid raindrops and ice particles, so each channel is sensitive to a different precipitation type. The GPM Core Observatory, with the addition of four new channels, has become the first spacecraft designed to detect light rain and snowfall from space.

Additionally, GMI's advanced technology allow the instrument to identify rain structures as small as approximately 3 to 9 miles across. This is a significant improvement over the capability of an earlier instrument flown on the Tropical Rainfall Measurement Mission in 1997.

"You can clearly see them in the GMI data because the resolution is that much better," said Skofronick-Jackson.

JAXA's DPR instrument adds a new dimension to the images that puts the data into high relief. The radar bounces signals off the raindrops and snowflakes to reveal the 3D structure of the storm in its entirety. Like the GMI instrument, DPR's two frequencies are sensitive to different rain and snow particle sizes. The original frequency senses heavy and moderate rain, while the newer, second radar frequency is tuned to lighter rainfall and snowfall.

"Both return independent measurements of the size of raindrops or snowflakes and how they are distributed within the weather system," said DPR scientist Bob Meneghini. "DPR allows scientists to see at what height different types of rain and snow or a mixture occur -- details that show what is happening inside sometimes complicated storm systems."

Combined, the data from the two instruments contribute to more accurate precipitation estimates. The combined data is used by researchers to calculate the rain rate, which is how much rain or snow falls to Earth. Rain rate is one of the Core Observatory's essential measurements for understanding where water is on Earth and where it's going.

"All this new information comes together to help us better understand how fresh water moves through Earth's system and contributes to things like floods and droughts," said Skofronick-Jackson.

These initial images were captured during the first few weeks after launch, as mission controllers at NASA Goddard Mission Operations Center were testing the spacecraft and its instruments to ensure they were healthy and functioning as expected. The sensors are calibrated by the engineering team, and the data returned is verified by the Goddard team at the Precipitation Processing System.

Once validated, the initial science data from the GPM Core Observatory will be released for free online in September.

Image 2 (below): On March 10 the Core Observatory passed over an extra-tropical cyclone about 1,055 miles (1,700 km) east of Japan's Honshu Island. Formed when a cold air mass wrapped around a warm air mass near Okinawa on March 8, it moved NE drawing cold air over Japan before weakening over the North Pacific. Credit: NASA/JAXA