Radiometer Concepts for Coastal and Inland Wet Path Delay Estimation
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Radiometer Concepts for Coastal and Inland Wet Path Delay Estimation Shannon Brown Jet Propulsion Laboratory [email protected] Radiometer Land Contamination. Land contamination can be divided into three categories Far sidelobe contamination Near sidelobe contamination

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Radiometer Concepts for Coastal and Inland Wet Path Delay Estimation Shannon Brown

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

Radiometer Concepts for Coastal and Inland Wet Path Delay Estimation

Shannon Brown

Jet Propulsion Laboratory

[email protected]


Radiometer land contamination

Radiometer Land Contamination

  • Land contamination can be divided into three categories

    • Far sidelobe contamination

    • Near sidelobe contamination

    • Main beam contamination

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)

Mainbeam

Near sidelobes


Main beam contamination

Main 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

~20 km approach estimated for worst case for AMR

10 km approach at Harvest estimated for AMR


Radiometer concepts

Radiometer Concepts

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

    • Real aperture

    • Synthetic aperture

    • > 2.5 m aperture required for < 5 km resolution


Option 1

Option 1

NASA Aquarius Heritage for 2.5 m reflector

Lightweight Rainfall Radiometer – aircraft heritage for synthetic aperture radiometer technology

Visible Camera

LRR


Radiometer concepts1

Radiometer 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)


Move to higher frequency

22.235 GHz (H2O)

118 GHz (O2)

55-60 GHz (O2)

183.31 GHz (H2O)

Move 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


Option 2

Option 2

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


Option 21

Option 2

Modeled Brightness Temperature to PD and CLW

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

  • Sensitivity to high PD decreases with frequency

23.8 GHz

90 GHz

2.6 km

10 km

dTB/dPD

130 GHz

160 GHz

2.1 km

1.5 km


Option 22

Option 2

  • 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)


Option 3

183 + 1

183 + 3

183 + 7

166

Option 3

  • 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

60 GHz Temperature Weighting Functions

183 GHz Water Vapor Weighting Functions

Height (km)


Option 31

Option 3

  • 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


Conclusions

Conclusions

  • 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


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