Methods of estimating precipitation characteristics

• US 7,417,577 B2
• Filed: 10/21/2004
• Issued: 08/26/2008
• Est. Priority Date: 10/21/2003
• Status: Expired due to Fees

• Current Assignee: Novimet SA
• Original Assignee: Centre National De La Recherche Scientifique
• Inventors: Testud, Jacques, Ney, Richard, LeBouar, Erwan
• Primary Examiner(s): Gregory; Bernarr E
• Application Number:
  US10/576,374
• Publication Number:
  US 20070103359A1
• Time in Patent Office: 1,405 Days
• Field of Search: 342 26 R- 26 D, 342/27, 342/28, 342/175, 342/176, 342/179, 342188-197, 702 1- 3, 731/701.6, 731/701.7
• US Class Current: 342/26.00R
• CPC Class Codes: G01S 13/95 for meteorological use
• CPC Class Codes: G01S 13/951 ground based
• CPC Class Codes: G01S 17/95 for meteorological use
• 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

A method of estimating precipitation characteristics including acquiring a radar image including at least a vertical plane of a precipitation zone; processing a vertical profile to generate digital signals representative of reflectivity in vertical direction z; integrating the signals representative of reflectivity by assimilation of a reflectivity vertical profile in an aggregation model to generate a signal representative of the profile in the vertical plane of a mean particle diameter weighted by mass of each particle; and determining concentration of the solid particles on the basis of signals previously determined.

Claims

1. A method of estimating precipitation characteristics comprising:

acquiring a radar image including at least a vertical plane of a precipitation zone;

processing via a computation unit a vertical profile of said precipitation zone to generate digital signals representative of reflectivity in vertical direction z;

integrating via the computation unit the signals representative of reflectivity by assimilation of a reflectivity vertical profile in an aggregation model to generate a signal representative of the profile in the vertical plane of a mean particle diameter weighted by mass of each particle; and

determining via the computation unit and displaying on a display device connected to the computation unit, concentration of the solid particles on the basis of signals representative of the profile in a vertical plane of a mean particle diameter weighted by mass of each particle.

2. The method according to claim 1, wherein integrating comprises determining variable Z(h) of the radar image observable in mm⁶/m³ as a function of altitude h on the basis of the radar image, and determining the mean diameter Dm(h) of the particles with the following equation:

$\begin{array}{cc}\frac{\mathrm{\delta <br><br>}<br><br><br><br>D_m}{\mathrm{\delta <br><br>}<br><br><br><br>h}\equiv <br><br>-0.25<br><br>k_{\mathrm{eff}}<br><br>{\mathrm{aD}}_m^{b-5}<br><br>{{10}^{-}}^{18}<br><br>Z+\left(\frac{11<br><br>\mathrm{\delta <br><br>}<br><br><br><br>Z}{6<br><br>Z<br><br><br><br>\mathrm{\delta <br><br>}<br><br><br><br>h}\right)<br><br>D_m& \left(2\right)\end{array}$

where;

Z is the radar image to be inverted in mm⁶/m<sup>−

3</sup>;

D_m is in meters (m);

a and b are coefficients specific to aggregate particles;

k_eff is the coefficient of effectiveness of aggregation to be adjusted.

3. The method according to claim 2, wherein the coefficient k_eff is equal to 0.3.

4. The method according to claim 2, wherein the coefficient a is equal to 35184.

5. The method according to claim 2, wherein the coefficient b is equal to 3.16.

6. The method according to claim 1, wherein the integration constant is determined so that the value D_m(h) at the top of a cloud corresponds to the predetermined value for the total number of particles at the top of the cloud.

7. The method according to claim 1, wherein the profile of the total number of particles n_t(h) is determined by the following equation:

n_T(h)=x.Z(h)/D_m(h)⁶.

8. The method according to claim 1, wherein x is equal to 25.4 10⁻

18.

9. The method according to claim 1, wherein meteorological parameter N_O(h) is determined by the following equation:

N_O(h)=y.Z(h)/D_m(h)⁷.

10. The method according to claim 1, wherein y is equal to 102 10⁻

18.

11. The method according to claim 1, wherein the meteorological parameter corresponding to the profile of the ice water content IWC(h)(in g/m³) is determined by the following equation:

IWC(h)=wZ(h)/D_m(h)³.

12. A method according to claim 11, wherein w is equal to 1.25 10⁻

12.

13. A profile determined according to claim 1, wherein the meteorological parameter corresponding to a profile of solid precipitation rate R(h)(mm/h equivalent melted) is determined by the following equation:

R(h)=r.Z(h)/D_m(h)^2.35.

14. The method according to claim 1, wherein characterized in that r is equal to 4.698 10⁻

10.

15. A method of estimating precipitation rate for solid precipitation comprising:

an acquisition step comprising acquiring a radar image including at least a vertical plane of a precipitation zone and processing via a computation unit a vertical profile of said precipitation zone to deliver digital signals representative of reflectivity in the vertical direction z;

an integration step comprising integrating via the computation unit signals representative of reflectivity by assimilation of the reflectivity vertical profile in an aggregation model to deliver a signal representative of the profile in the vertical plane of a mean particle diameter weighted by mass of each particle; and

a determination and displaying step comprising determining via the computation unit and displaying on a display device connected to the computation unit, concentration of the solid particles on the basis of signals representative of the profile in a vertical plane of a mean particle diameter weighted by mass of each particle.

16. The method according to claim 15, wherein the integration step comprises determining variable Z(h) of the radar image observable in mm⁶/m³ as a function of the altitude h on the basis of the radar image, and determining the mean diameter Dm(h) of the particles with the following equation:

$\begin{array}{cc}\frac{\mathrm{\delta <br><br>}<br><br><br><br>D_m}{\mathrm{\delta <br><br>}<br><br><br><br>h}\equiv <br><br>-0.25<br><br>k_{\mathrm{eff}}<br><br>{\mathrm{aD}}_m^{b-5}<br><br>{{10}^{-}}^{18}<br><br>Z+\left(\frac{11<br><br>\mathrm{\delta <br><br>}<br><br><br><br>Z}{6<br><br>Z<br><br><br><br>\mathrm{\delta <br><br>}<br><br><br><br>h}\right)<br><br>D_m& \left(2\right)\end{array}$

where;

Z is the radar image to be inverted in mm⁶/m<sup>−

3</sup>;

D_m is in meters (m);

a and b are coefficients specific to aggregate particles;

k_eff is the coefficient of effectiveness of aggregation to be adjusted.

17. The method according to claim 15, wherein the integration constant is determined so that the value D_m(h) at the top of a cloud corresponds to the predetermined value for the total number of particles at the top of the cloud.

18. The method according to claim 15, wherein the profile of the total number of particles n_t(h) is determined by the following equation:

n_T(h)=x.Z(h)/D_m(h)⁶.

19. The method according to claim 15, wherein meteorological parameter N_O(h) is determined by the following equation:

N_O(h)=y.Z(h)/D_m(h)⁷.

20. The method according to claim 15, wherein the meteorological parameter corresponding to a profile of ice water content IWC(h)(in g/m³) is determined by the following equation:

IWC(h)=wZ(h)/D_m(h)³.