Adaptive specific differential phase in dual-polarization radar

• US 20090315762A1
• Filed: 03/16/2009
• Published: 12/24/2009
• Est. Priority Date: 03/14/2008
• Status: Active Grant

• Current Assignee: Colorado State University Research Foundation (Colorado State University System)
• Original Assignee: Colorado State University Research Foundation (Colorado State University System)
• Inventors: Wang, Yanting, Venkatachalam, Chandrasekaran
• Granted Patent: US 7,898,459 B2
• Time in Patent Office: Days
• US Class Current: 342/26.R
• CPC Class Codes: G01S 13/951 ground based
• CPC Class Codes: G01S 7/025 involving the transmission of linearly polarised waves
• CPC Class Codes: Y02A 90/10 Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation

Abstract

Systems and methods are provided for adaptively estimating the specific differential phase (K_dp) from dual-polarization radar data in the complex domain. Some embodiments adapt for wrapped differential propagation phases by estimating the specific differential phase in the complex domain. Some embodiments adapt for measurement fluctuations and/or spatial scale in making such estimations. Some embodiments also provide for determining the presence of storms cells using the dispersion of the differential propagation phase shift over a subset of bins.

Claims

1. A dual-polarization radar system comprising:

a dual polarization radar receiver;

a processor coupled with the receiver;

memory configured to store information including raw data received from the receiver, data processed by the processor, and processing code executable by the processor, the processing code including;

instructions to receive raw dual polarization data as a function of range from the dual polarization receiver;

instructions to determine a differential propagation phase shift as a function of range from the raw dual polarization data; and

instructions to estimate the complex specific differential phase from the differential propagation phase shift by estimating the derivative of the differential phase shift data with respect to range in the complex domain.

2. The dual-polarization system according to claim 1, wherein the instructions to estimate the complex specific differential phase further comprises solving the following Lagrangian:

3. The dual-polarization system according to claim 2, wherein the weighting parameter w⁻

1 is set to the standard deviation of the measured differential phases in the complex domain.

4. The dual-polarization system according to claim 2, wherein the scaling factor q⁻

1 is set to reflect the varying spatial scale of the measured differential phases in adaptation to the storm intensity.

5. The dual-polarization system according to claim 2, wherein the weighting parameter w⁻

1 and the scaling factor q<sup>−

1</sup> are evaluated for dual-polarization radar system.

6. The dual-polarization system according to claim 1, wherein the memory includes processing code including instructions to estimate the specific differential phase in the complex domain in response to the wrapped differential propagation phase shift.

7. The dual-polarization system according to claim 1, wherein the memory includes processing code including instructions to adapt the differential propagation phase shift data in response to spatial scale.

8. The dual-polarization system according to claim 1, wherein the memory includes processing code including instructions to adapt the differential propagation phase shift data in response to measurement fluctuations.

9. The dual-polarization system according to claim 1, wherein the memory includes processing code including instructions to identify the presence of storm cells in the differential propagation phase shift data.

10. A method for calculating the specific differential phase from the differential propagation shift between two polarizations, the method comprising:

receiving differential propagation phase shift data as a function of range in the complex domain from a dual polarization radar system;

determining the complex specific differential phase from the differential propagation phase shift data by calculating the derivative of the differential phase shift data with respect to range in the complex domain; and

converting the complex specific differential phase into the radial domain.

11. The method according to claim 10, further comprising identifying the presence of storm cells within the differential propagation phase shift data.

12. The method according to claim 11, wherein the determining the complex specific differential phase from the differential propagation phase shift data occurs only on the differential propagation phase shift data where storms cells have been identified.

13. The method according to claim 11, wherein the presence of a storm cell is identified using a dispersion of a subset of the differential propagation phase shift data.

14. The method according to claim 10, wherein the complex specific differential phase is determined by solving the following Lagrangian:

15. The method according to claim 14, wherein the weighting parameter w⁻

1 is set to the standard deviation of the measured differential phases in the complex domain.

16. The method according to claim 14, wherein the scaling factor q⁻

1 is set to reflect the varying spatial scale of the measured differential phases in adaptation to the storm intensity.

17. The method according to claim 14, wherein the weighting parameter w⁻

1 and the scaling factor q<sup>−

1</sup> are evaluated for dual-polarization radar system.

18. A method for determining the presence of storm cell from differential propagation phase shift data, the method comprising:

receiving range profiles of differential propagation phase shift data from a radar system, wherein the range profiles of differential propagation phase shift data comprises an array of differential propagation phase shift data arranged in bins corresponding to range;

when the dispersion at a first consecutive subset of bins is greater than a first threshold, indicating the first cell of the first sequential number of bins as the start of a rain cell; and

when the dispersion at a second consecutive subset of bins is less than a second threshold, indicating the first cell of the second sequential number of bins as the end of a rain cell.

19. The method according to claim 18, wherein the number of bins within the first sequential number of bins is greater than the number of bins within the second sequential number of bins.

20. The method according to claim 18, wherein the first threshold and the second threshold are the same.

21. The method according to claim 18, wherein the first threshold equals about 0.98.

22. The method according to claim 18, further comprising indicating that the bins between the first bin within the first consecutive subset of bins and the first bin within the second consecutive subset of bins as part of a rain cell.

23. The method according to claim 18, wherein the indicating the first cell of the sequential number of bins as the end of a rain cell when the dispersion at the consecutive subset of bins is less than a second threshold and the co-polar correlation coefficient of the differential propagation phase shift data is less than a third threshold.

24. The method according to claim 23, wherein the third threshold is about 0.9.

25. A system comprising:

means for receiving dual-polarization echo data from a dual polarization radar receiver;

means for determining a differential propagation phase shift as a function of range from the raw dual polarization data; and

means for determining the complex specific differential phase from the differential propagation phase shift by estimating the derivative of the differential phase shift data with respect to range in the complex domain.

26. The system according to claim 25, further comprising means for adapting the differential phase shift data for spatial scale.

27. The system according to claim 25, further comprising means for adapting the differential phase shift data for measurement fluctuations.

28. The system according to claim 25, further comprising means for determining the presence of storm cells within the differential phase shift data.

29. A dual-polarization radar system comprising:

a dual polarization radar receiver;

a processor coupled with the receiver;

memory configured to store information including raw data received from the receiver, data processed by the processor, and processing code executable by the processor, the processing code including;

instructions to determine a differential propagation phase shift as a function of range from raw dual polarization data received from the dual polarization receiver, wherein the differential propagation phase shift data comprises an array of data arranged in bins corresponding to range;

instructions for indicating the first bin of a first sequential number of bins as the start of a rain cell when the dispersion over the first sequential number of bins along a range is greater than a first threshold; and

instructions for indicating the first bin of a second sequential number of bins as the end of a rain cell when the dispersion over the second sequential number of bins along a range is less than a second threshold.

30. The dual-polarization radar system according to claim 29, wherein the processing code includes instructions to indicate bins sequentially between bins identified as the start of a rain cell and bins identified as the end of a rain cell as rain cell bins.