Global Precipitation Measurement – Dual Frequency Precipitation RadarYong Xiang TeohEECS823December 11, 2014

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GPM Mission• International partnership in between NASA and JAXA• Constellation of satellites including the GPM Core Observatory• Core Observatory is the successor to TRMM• Launched to the orbit from Tanegashima Space Center, Japan

on February 28, 2014• Near global coverage every three hours

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GPM Core Observatory• Dimension: 6.5 x 4.9 x 11.6 m• Orbit:• Circular, non-sun synchronous• 65 degrees inclination• Altitude: 407km• Orbit time: 93 minutes

• Science Instruments:• GPM Microwave Imager (GMI)• Dual Frequency Precipitation Radar

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Dual Freq. Precipitation Radar• Consists of Ku-PR and Ka-PR• Ku-PR is similar to TRMM PR• Ka-PR is based upon Ku-PR design with antenna size designed

to match the Ku-PR measurement footprint• Both use phased array, slotted wave guide antenna• Electronically steerable• Dual frequencies provide differential reflectivities:• Drop size distributions (DSD)• More accurate rainfall estimates

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Dual Frequency Measurement

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DPR SpecificationsKu-PR Ka-PR

Frequency 13.6GHz 35.5GHz

Swing angle 17deg 8.5degSwath width 245km 120kmRange resolution 250m 250m/500m

Beam Width 0.71deg 0.71deg

Footprint 5km 5km

Peak Transmit Power 1013W 146W

PRF VPRF (4206Hz±170Hz) VPRF (4275Hz±100Hz)

Pulse width 2 x 1.667μs 2 x 1.667μs/2 x 3.234μs

Detection threshold <18 dBZ (<0.5 mm/hr) <12 dBZ (<0.2mm/hr)6

Scan Pattern

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Measured Data

A extra-tropical cyclone observed over the northwest Pacific Ocean off the coast of Japan captured by DRP on March 10, 2014

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Measured Data

3D precipitation structures of Typhoon No.11 “HALONG” captured by DPR on August 9, 2014

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References

• Everett, D.F., Bidwell, S.W., Flaming, G.M., Rykowski, T.B., Stocker, E.F., Braatz, L.E., “Engineering of the global precipitation measurement system”, 2003

• Flaming, G.M., “Global Precipitation Measurement Update”, July 25, 2005

• Furukawa, K., Kojima, M., Miura, T., Hyakusoku, Y., Iguchi, T., Hanado, H., Nakagawa, K., Okumura, M., “Proto-flight test of the Dual-frequency Precipitation Radar for the Global Precipitation Measurement”, July 24, 2011

• Iguchi, T., “Spaceborne Precipitation Radars in TRMM and GPM”, • “Global Precipitation Measurement”, http://pmm.nasa.gov/GPM• “Global Precipitation Measurement/Dual-frequency Precipitation

Radar”, http://global.jaxa.jp/projects/sat/gpm/ 10