Robust attenuation correction system for radar reflectivity and differential reflectivity

• US 9,465,106 B2
• Filed: 03/15/2013
• Issued: 10/11/2016
• Est. Priority Date: 03/27/2012
• Status: Active Grant

• Current Assignee: Colorado State University Research Foundation
• Original Assignee: Colorado State University Research Foundation
• Inventors: Venkatachalam, Chandrasekaran, Lim, Sanghun
• Primary Examiner(s): Sotomayor, John B
• Assistant Examiner(s): WINDRICH, MARCUS E
• Application Number:
  US13/842,065
• Publication Number:
  US 20130271313A1
• Time in Patent Office: 1,306 Days
• Field of Search: 342 26 R- 26 D
• US Class Current: 1/1
• CPC Class Codes: G01S 13/95 for meteorological use
• CPC Class Codes: G01S 13/951 ground based
• CPC Class Codes: G01S 13/958 Theoretical aspects
• 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

Embodiments of the invention are directed toward attenuation correction of radar data. Atmospheric attenuation is a function of atmospheric water drop size and temperature. A number of different theoretical models are available to mathematically describe the particle drop shape that influences attenuation estimation. Each of these models has proven effective in different scenarios. It can be difficult, however, to predict which theoretical model to use. The total differential phase gives an idea of the attenuation, but it depends on the model. Moreover, the total attenuation along a rain path must be apportioned to different parts of the radar path in order to correct for attenuation along a radar path. Embodiments of this invention allows for a system to apportion the attenuation to different parts of the radar beam. Embodiments of the invention also allow for optimization of a number of different theoretical models for both drop size and temperature.

Claims

1. A weather radar system comprising:

a transmitter configured to transmit a weather radar signal into a region of interest;

a receiver configured to receive echoes scattered from the region of interest, and

a computer system coupled at least with the receiver, wherein the computer system is configured to

calculate a plurality of attenuation pairs from the received echoes, wherein each attenuation pair comprises a cumulative attenuation and a differential attenuation from the received echoes;

solve a cost function for each of the attenuation pairs, wherein the cost function is a function of the cumulative attenuation and the differential attenuation, and wherein the cost function returns a cost function value for each attenuation pair; and

determine the attenuation pair associated with the minimum cost function value.

2. The weather radar system according to claim 1, wherein either or both of the cumulative attenuation and the differential attenuation is independent of radar system bias.

3. The weather radar system according to claim 1, wherein the cumulative attenuation of the plurality of attenuation pairs is calculated between an estimated maximum cumulative attenuation value and an estimated minimum cumulative attenuation value.

4. The weather radar system according to claim 1, wherein the differential attenuation of the plurality of attenuation pairs is calculated between an estimated maximum differential attenuation value and an estimated minimum differential attenuation value.

5. The weather radar system according to claim 1, wherein the cost function is a function of the differential propagation phase.

6. A method for determining attenuation in a radar signal, the method comprising:

transmitting a radar signal into the atmosphere from a weather radar system;

receiving echoes from the atmosphere in response to the radar signal at the weather radar system;

calculating, with a computer system, a plurality of attenuation pairs from the received echoes, wherein each attenuation pair comprises a cumulative attenuation and a differential attenuation from the received echoes;

solving, with the computer system, a cost function for each of the attenuation pairs, wherein the cost function is a function of the cumulative attenuation and the differential attenuation, and wherein the cost function returns a cost function value for each attenuation pair; and

determining, with the computer system, the attenuation pair associated with the minimum cost function value.

7. The method for determining attenuation in a radar signal according to claim 6, wherein either or both of the cumulative attenuation and the differential attenuation is independent of radar system bias.

8. The method for determining attenuation in a radar signal according to claim 6, wherein the cumulative attenuation of the plurality of attenuation pairs is calculated between an estimated maximum cumulative attenuation value and an estimated minimum cumulative attenuation value.

9. The method for determining attenuation in a radar signal according to claim 6, wherein the differential attenuation of the plurality of attenuation pairs is calculated between an estimated maximum differential attenuation value and an estimated minimum differential attenuation value.

10. The method for determining attenuation in a radar signal according to claim 6, wherein the cost function is a function of the differential reflectivity.

11. The method for determining attenuation in a radar signal according to claim 6, wherein the cost function is a function of the differential reflectivity and proportional to a reflectivity factor.

12. The method for determining attenuation in a radar signal according to claim 6, further comprising determining a plurality of model coefficients from the attenuation pair.

13. The method for determining attenuation in a radar signal according to claim 6, wherein the cost function comprises:

14. A method for processing radar data, the method comprising:

transmitting a radar signal into the atmosphere from a weather radar system;

receiving echoes from the atmosphere at the weather radar system in response to the radar signal, wherein the echoes comprise echoes having a first polarization and echoes having a second polarization;

reconstructing, with a computer system, a first reflectivity factor from the received echoes with the first polarization;

reconstructing, with the computer system, a second reflectivity factor from the received echoes with the second polarization;

determining, with the computer system, a differential reflectivity from the received echoes that is proportional to a ratio of the first reflectivity factor and the second reflectivity factor; and

determining a differential propagation phase that is nonlinearly proportional to a reflectivity value of the received echoes.

15. The method according to claim 14, wherein either or both the first reflectivity factor and the second reflectivity factor are determined from:

16. A method comprising:

transmitting a weather radar signal into the atmosphere from a weather radar system;

receiving echoes from the atmosphere in response to the radar signal at the weather radar system;

determining, with a computer system, a plurality of cumulative attenuation values for a plurality of different models;

determining, with the computer system, a plurality of differential attenuation values for a plurality of different models;

determining, with the computer system, an optimal cumulative attenuation value from the plurality of cumulative attenuation values;

determining, with the computer system, an optimal differential attenuation value from the plurality of cumulative attenuation values; and

determining, with the computer system, a differential reflectivity based on the optimal cumulative attenuation and the optimal differential attenuation.

17. A method comprising:

transmitting a weather radar signal into the atmosphere from a weather radar system;

receiving echoes from the atmosphere in response to the radar signal at the weather radar system;

calculating, with the computer system, a plurality of attenuation pairs from the received echoes, wherein each attenuation pair comprises a cumulative attenuation and a differential attenuation from the received echoes;

solving, with the computer system, a cost function for each of the attenuation pairs, wherein the cost function returns a cost function value for each attenuation pair; and

determining, with the computer system, the attenuation pair associated with the minimum cost function value.