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 (?)