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Transcript of Precipitation Retrieval Accuracies for Geo-Microwave …ipwg/resources/pdf/Staelin_IGARSS GEM...
MIT REMOTE SENSING AND ESTIMATION GROUPhttp://rseg.mit.edu 1
Precipitation Retrieval Accuracies for Geo-Microwave Sounders
David H. Staelin and Chinnawat Surussavadee
Presented at IGARSS ’06
Denver, ColoradoJuly 31, 2006
OUTLINEGeoMicrowave instrument conceptsPrecipitation retrieval methodInstrument optionsMovies: MM5 vs. GEMMovies: GEM and GeoStar comparisonSummary and conclusions
Staelin andSurussavadeeJuly 2006
MIT REMOTE SENSING AND ESTIMATION GROUPhttp://rseg.mit.edu 2
NoddingSubreflector
MIT Lincoln Laboratory 1998 GEM study of 2m dish:Can be integrated on GOES
∆Trms ≅ 0.5K (400 GHz, τ = 0.1s) Weight ~40 kg, 130 watts
8 km200 km
8 km/sec
Geo-Microwave Sensor Concepts
Staelin andSurussavadeeJuly 2006
GeoSTAR’
GEM2 meters
2 m
1.2 mGOES
GEM
GeoSTAR
2 mGEM’
Sketch by Ball Sketch by JPLSketch by MIT Lincoln Laboratory
MIT REMOTE SENSING AND ESTIMATION GROUPhttp://rseg.mit.edu 3
Original 183±7 GHz 5-km image260 oK
220
180
Blurred 30-km image
Sharpened pattern G’(θ)
30 km
Original antenna pattern
Sharpened 30-km image
~22.5 km
Image Sharpening
Requires Nyquist samplingG’(θ) = Fourier transform {W(fθ)}
To minimize MSE:
Noise increase is acceptable
12
2A
N (f )W(f ) 1
T (f )
−
θθ
θ
⎛ ⎞⎜ ⎟= +⎜ ⎟⎝ ⎠
Staelin andSurussavadeeJuly 2006
MIT REMOTE SENSING AND ESTIMATION GROUPhttp://rseg.mit.edu 4
Spatial Resolution (KM) at Nadir
25252525600 rcvrs/band 0.5/D50505050300 rcvrs/band 0.5λ/D
20234651721.2-m dish(E) 0.95λ/D1214283143962-m dish(A-D) 0.95λ/D17183842581292-m dish 1.3λ/D42538018316611853
Frequency Band (GHz)Antenna type
Instrument Options Evaluated
≤ 30 km
Staelin andSurussavadeeJuly 2006
Frequencies studied for GEMApproximate Frequencies (GHz)
118.75 ±0.5, ±1.15, ±1.5, ±2.05 @ 45 km166 @ 30 km; 183.31±1, ±3, ±7, @ 25 km 380.2 ±1.5, ±4, ±9, ±18 @ 15 km 424.76 ±0.6 , ±1, ±1.5, ±4 @ 15 km
MIT REMOTE SENSING AND ESTIMATION GROUPhttp://rseg.mit.edu 5
Clear-air Incremental weighting functions (IWF) for temperature and humidity vs. offset (MHz) from line center (from Klein and Gasiewski, 2000).
Peaks of GEM/GeoSTARweighting functions analyzed here.
Note that high humidity can preclude penetration below ~2 km at 118, 166 GHz.
GEM Channel Selection Issues
−0.05 0 0.05 0.1 0.150
10
20
30
40118.7503 GHz
Altitude (
km
)
Temperature IWF (km−1)
15−21
29−41
70−90
150−250300−500500−900
900−1300← 1300−1700
← 1700−2500← 2500−3500
4000−6000↓
0 0.05 0.1 0.15 0.2 0.250
10
20
30
40424.7631 GHz
Altitude (
km
)
Temperature IWF (km−1)
25−35
60−80
120−180
250−350500−700800−12001200−1800
3500−4500
−2 0 2 4 60
5
10
15
20150−450
650−11501300−20002500−35004000−6000
← 6000−8000
15000−19000
183.3101 GHz
Altitude (
km
)
Water Vapor IWF (K km−1)
−2 −1.5 −1 −0.5 0 0.50
5
10
15
2030−60
300−500
1250−1750
3550−4450
8000−1000017000−19000↑
380.1974 GHz & 340 GHz
Altitude (
km
)
Water Vapor IWF (K km−1)
336−344 GHz
118 GHz (O2) 425 GHz (O2)
183 GHz (H2O) 380/340 GHz (H2O)
Staelin andSurussavadeeJuly 2006
MIT REMOTE SENSING AND ESTIMATION GROUPhttp://rseg.mit.edu 6
Geo-Microwave Precipitation Retrievals
Staelin andSurussavadeeJuly 2006
Rain rate estimate R (mm/h)
118 GHz(4 O2 Channels)166-183 GHz(4 H2O Channels)380 GHz (4 H2O Channels)425 GHz (4 O2 Channels)Land/sea, elevation
R > 8? R
(mm/h)
Neural Net 2
Neural Net 3
Yes
No
8
8
8
Training (NCEP/MM5, 122 global storms)1
Nets 2 and 3 were trained with different R values (NN×1.3 better matches MM5, retrieval colors)
8Neural Net 1
(for categorization)
34
Rain-rate estimates: input = two TB spectra 15 minutes apart at 40° zenith angle. Water-path estimates are based on one spectrum (18 numbers).All networks have 10, 5 and 1 neurons in their input, hidden, and output layers,
respectively.Same general estimator architecture was used for analyzing GeoSTAR options
2
Simulations or observations
MIT REMOTE SENSING AND ESTIMATION GROUPhttp://rseg.mit.edu 7
Rain Rate and Water Path RetrievalsM
M5
Trut
hG
EM re
trie
val
Surface precipitation rate (mm/h)
Rain water path (mm)
Graupel water path (mm)
Snow water path (mm)
Retrievals: 2-m GEM antenna; 118/183/380/425-GHz bands; Front, January 2, 2003
1 2 4 8 1 2 4 1 2 4 1 2 4 8 16 32
Staelin andSurussavadeeJuly 2006
MIT REMOTE SENSING AND ESTIMATION GROUPhttp://rseg.mit.edu 8
MM5 vs. 2-m GEM Rain Rate (mm/h)MM5 Truth 2-m GEM retrieval
European Front, 1003 UTC January 2, 2003, viewed 3 hours at 5-minute intervals
Staelin andSurussavadeeJuly 2006
MIT REMOTE SENSING AND ESTIMATION GROUPhttp://rseg.mit.edu 9
MM5 Truth 2-m GEM retrieval
MM5 vs. 2-m GEM Rain Rate (mm/h)
Typhoon, 1625 UTC December 8, 2002, viewed 3 hours at 5-minute intervalsStaelin andSurussavadeeJuly 2006
MIT REMOTE SENSING AND ESTIMATION GROUPhttp://rseg.mit.edu 10
MM5 Truth 2-m GEM retrieval
MM5 vs. 2-m GEM Snowfall Rate (mm/h)
Moscow snow storm, 1122 UTC, March 23, 2003 Viewed for 3 hours every 5 minutes The retrieved trailing edge position is correct, the leading edge is extended
Staelin andSurussavadeeJuly 2006
MIT REMOTE SENSING AND ESTIMATION GROUPhttp://rseg.mit.edu 11
Spatial Resolution (KM) at Nadir
25252525600 rcvrs/band 0.5/D50505050300 rcvrs/band 0.5λ/D
20234651721.2-m dish(E) 0.95λ/D1214283143962-m dish(A-D) 0.95λ/D17183842581292-m dish 1.3λ/D42538018316611853
Frequency Band (GHz)Antenna type
Instrument Options Evaluated
≤ 30 km
Staelin andSurussavadeeJuly 2006
Frequenciesfor 10 Instrument Options, A-JApproximate Frequencies (GHz) A B C D E F G H I J
52.8, 53.6, 54.4, 55.5 @ 50 km • • • •118.75 ±0.5,±1.15, ±1.5, ±2.05 @ 45 km • • • • • • •166 @ 30 km; 183.31±1, ±3, ±7 @ 30/25 km • • • • • •380.2 ±1.5,±4, ±9, ±18 @ 15 km • • •424.76 ±0.6 ,±1, ±1.5, ±4 @ 15 km • • •
km72 502515
Single dish options
25 km
50
Aperture synthesis
MIT REMOTE SENSING AND ESTIMATION GROUPhttp://rseg.mit.edu 12
Representative Instrument OptionsW
arm
rain
S
tratif
orm
Typh
oon
S
trong
fron
t
Mm/hrMM5 RR 2-m GEM 1.2-m GEM 900-rcvr GS 600-rcvr GS 600-rcvr GS
118/183/380/425 118/183/380/425 54/183@50/25 km 54/118@50 km 54@25 km
Staelin andSurussavadeeJuly 2006
MIT REMOTE SENSING AND ESTIMATION GROUPhttp://rseg.mit.edu 13
GEM vs. GeoStar’ Rain Rate Images2-m GEM 1.2-m GEM MM5 truth GS-900 (55/183) GS-600 (54/118)
Staelin andSurussavadeeJuly 2006
MIT REMOTE SENSING AND ESTIMATION GROUPhttp://rseg.mit.edu 14
Summary and Conclusions
Staelin andSurussavadeeJuly 2006
Image sharpening can improve antenna resolution ~×1.3
Nodding subreflectors greatly reduce antenna scan momentum impact
Both 1.2- and 2-m antenna dishes could be integrated on GOES
Bands near 118, 183, 380, and 425 GHz are adequate (~16 channels)
Geostationary microwave retrievals are feasible for: - surface precipitation rates for rain and snow (mm/h), and - water paths for rain water, snow, and graupel (mm)
The simplest aperture synthesis system comparable to a 1.2-meter antenna uses 900 receivers (300 at 54-GHz, 600 at 183-GHz), each with 4 channels (high cost and risk)
No other global technique for monitoring precipitation evolution is comparable; geostationary microwave (GEM) should be part of PMM