GPM GMI update
Chris Kidd
RFI issues
Two main sources:• Reflection from broadcast satellites - affects 18.7 GHz primarily to varying degrees - can be predicted to some extent• Surface emissions - spurious emissions from surface emitters - affects primarily 6.9 and 10.7 GHz, but also 18.7GHz
20140305-S061920
V10 H10
V18 H18
secondary RFI – sidelobe/2nd satellite
Strong RFIover ice
20140307-S060554
V10 H10
V18 H18
Strong RFIfrom ice (?)
20140309-S0055206
V10 H10
V18 H18
subtle RFI – H channel only
Broadcast RFI• Ice appears to provide a very good reflector of 18.7
GHz RFI (ice structure?)• Water surfaces more variable – presumably due to
wave orientation• Some land surfaces also reflect – more subtle
• Possible to forward-calculate satellite-surface-satellite path to identify regions of possible RFI
• Obvious RFI is good – subtle RFI is bad.
Surface RFIPrimarily at 10GHz• Initial study by the Office of Communication, Ofcom,
(UK), found that at 10.67 GHz licenses had been issued within ITC regulations (low-power (mW) motion detection systems).
18 GHz sources• Some broadcast bands, but usually satellite-ground,
occasionally associated with ship-based radars. Mobile phones are <3 GHz, possibly communication links at 18 GHz (Spanish?).
V10 H10
V18 H18
20140308-S234218
V10 H10
V18 H18
20140309-S224904
20140309-S224904
V18
Kartoum
El Obeid
Abu Zabad
Shendi
Wad Medani
Atbara
GMI quicklook images:
• Daily global asc/desc image• TRMM false-colour scheme• 1/8 degree resolution (2880x1440)
ftp://meso-a.gsfc.nasa.gov/kidd/GMIql
quick-look_GMI_20140517_dsc.jpg
16 May 2014
SSMIS F16 15:00 GMI 15:30 Radar 15:30
MHS N18 16:00 MHS N18 MSPPS 16:00 SSMIS F17 16:00
Precip retrievals 7 April 2014
Constellation x-track – ideal (!)
My Best Guess as of 5/9/14GMI Calibration Error over Ocean
Standard10V 3.0K Windsat10H 1.6K "18V 2.5K "18H 0.0K "23V 0.2K "36V -1.3K "36H -1.3K "89V 3.8K Metop A or B89H 4.2K "166V -3.4K "166H -1.4K "±3 --2.0K "±7 -2.9K "
Tom Wilheit 2014
GMI vs TMI
GMI - TMI double differences
Ver 10v 10h 18v 18h 23v 36v 36h 89v 89h --- --- --- --- --- --- --- --- --- --- V01D 4.3 3.1 3.3 2.7 1.9 2.3 1.2 1.0 1.0 V02A 4.2 3.2 3.1 2.8 1.7 2.1 1.2 0.8 0.9
Rachael Kroodsma (NASA PPS)
Solar intrusion (V)
Tom Wilheit 2014
Solar intrusion (H)
Tom Wilheit 2014
Additional slides…
20140308-S051249
V10 H10
V18 H18
Strong RFInot ice (?)
20140311-S040553
V10 H10
V18 H18
Very subtle RFI – V&H channel
Kidd, 2006
Kidd, 2006
20140310-S045852
V10 H10
V18 H18
Strong RFIfrom ice (?)
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