We have entered a new era in measuring precipitation from space… now being able to measure global precipitation of all types… from light drizzle to heavy downpours to falling snow!
NASA and the Japan Aerospace Exploration Agency have released the first images captured by their newest Earth-observing satellite… the Global Precipitation Measurement (GPM) Core Observatory… which launched into space Feb. 27.
The images show precipitation falling inside a March 10 cyclone over the northwest Pacific Ocean… approximately 1,000 miles east of Japan. The data were collected by 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.
The satellite's capabilities are apparent in the first images of the cyclone. Cyclones such as the one imaged -- an extra-tropical cyclone -- occur when masses of warm air collide with masses of cold air north or south of the tropics. These storm systems can produce rain… snow… ice… high winds and other severe weather.
In these first images… the warm front ahead of the cyclone shows a broad area of precipitation -- in this case, rain -- with a narrower band of precipitation associated with the cold front trailing to the southwest. Snow is seen falling in the northern reaches of the storm.
The GMI instrument has 13 channels that measure natural energy radiated by Earth's surface and also by precipitation itself. Liquid raindrops and ice particles affect the microwave energy differently… so each channel is sensitive to a different precipitation type. With the addition of four new channel… the GPM Core Observatory is the first spacecraft designed to detect light rain and snowfall from space.
In addition to seeing all types of rain… GMI's technological advancements allow the instrument to identify rain structures as small as about 3 to 9 miles across. This higher resolution is a significant improvement over the capability of an earlier instrument flown on the Tropical Rainfall Measurement Mission in 1997. The DPR instrument adds another dimension to the observations that puts the data into high relief. The radar sends signals that bounce off the raindrops and snowflakes to reveal the 3D structure of the entire storm. Like GMI… its two frequencies are sensitive to different rain and snow particle sizes. One frequency senses heavy and moderate rain. A new… second radar frequency is sensitive 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. 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.
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