radiometer concepts for coastal and inland wet path delay estimation shannon brown

Barcelona, July 25, 2007WATER HM Meeting

Radiometer Radiometer Concepts for Coastal Concepts for Coastal and Inland Wet Path and Inland Wet Path

Delay EstimationDelay Estimation

Shannon Brown

Jet Propulsion Laboratory

[email protected]

Barcelona, July 25, 2007WATER HM MeetingRadiometer Land Contamination

Land contamination can be divided into three categories Far sidelobe contamination Near sidelobe contamination Main beam contamination

Near sidelobes

Mainbeam

Far sidelobes

Far sidelobe contamination

Correctable to acceptable levels (~ 1mm)

Near sidelobe contamination

More difficult, but correction is possible (~2-4 mm)

Main beam contamination

Very difficult to correct (20-40 mm)

Barcelona, July 25, 2007WATER HM MeetingMain Beam Contamination

Along track averaging can improve coastal approach for preferred land/ground track orientations

Additional improvements may be made through correction algorithms based on pattern weighted main beam land fractions

10 km approach at Harvest estimated

for AMR

~20 km approach estimated for worst

case for AMR

Barcelona, July 25, 2007WATER HM MeetingRadiometer Concepts

Option 1: Maintain traditional channel set, but increase antenna dimensions

Real aperture Synthetic aperture > 2.5 m aperture required for < 5 km resolution

Barcelona, July 25, 2007WATER HM MeetingOption 1

NASA Aquarius Heritage for 2.5 m reflector

Lightweight Rainfall Radiometer – aircraft heritage for synthetic aperture radiometer technology

Visible Camera

LRR

Barcelona, July 25, 2007WATER HM MeetingRadiometer Concepts

Option 1: Maintain traditional channel set, but increase antenna dimensions

Real aperture Synthetic aperture > 2.5 m aperture required for < 5 km resolution

Pros: Proven retrieval algorithm Retrievals in all non-precipitating conditions High sensitivity to PD over the range of PDs

Cons: Complications from large real aperture required Synthetic aperture technique proven in aircraft demonstration,

but not yet in space Difficult to get PD in inland areas (i.e. rivers)

Barcelona, July 25, 2007WATER HM MeetingMove to Higher Frequency

Maintain 18-34 GHz channel set for open ocean retrievals

Maintain AMR heritage 1m reflector

Option 2: Include 1-2 higher frequency window channels for coastal PD extrapolation

Option 3: Include temperature and vapor sounding channels for PD retrievals over land and ocean

22.235 GHz (H2O)

55-60 GHz (O2)118 GHz (O2)

183.31 GHz (H2O)


Add 1 or 2 channels between 90-150 GHz to improve the extrapolation of PD from the last uncontaminated ocean pixel to the coast


Modeled Brightness Temperature to PD and CLW

23.8 GHz 90 GHz

130 GHz 160 GHz

90 GHz TB ~8x more sensitive to CLW than 23.8 GHz TB

Sensitivity to high PD decreases with frequency

10 km 2.6 km

2.1 km 1.5 km

dTB/dPD


Add 1 or 2 channels between 90-150 GHz to improve the extrapolation of PD from the last uncontaminated ocean pixel to the coast

Pros: Relatively small perturbation to add two channels in this

frequency range These channels will have < 5 km resolution with 1 m reflector

Cons: These channels will loose sensitivity to PD for high PD values Performance can be affected in variable cloud conditions near

coast Not likely to be able to get PD in inland areas (i.e. rivers)


Add temperature and water vapor sounding channels to retrieve PD over land and coast (channels near 50 or 118 GHz and channels near 183 GHz)

Will likely need 2-3 temperature sounding channels and 4 water vapor sounding channels

183 + 1

183 + 3

183 + 7

166

Hei

gh

t (k

m)

60 GHz Temperature Weighting Functions 183 GHz Water Vapor

Weighting Functions


Add temperature and water vapor sounding channels to retrieve PD over land and coast (channels near 50 or 118 GHz and channels near 183 GHz)

Pros: Should be able to retrieve PD over land or water High resolution < 5 km

Cons: Reduced accuracy in clouds Reduced sensitivity to PD in moist conditions Uncertain with what accuracy this can be done

Barcelona, July 25, 2007WATER HM MeetingConclusions

Option 1: Large antenna Scientific Risk: Low Engineering Risk: Medium

Option 2: Higher frequency window channels Scientific Risk: Medium Engineering Risk: Low

Option 3: Temperature and water vapor sounding channels Scientific Risk: Medium Engineering Risk: Medium

radiometer concepts for coastal and inland wet path delay estimation shannon brown

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