Method for determining the precipitation ratio by double polarization radar and meteorological radar for implementing such process
First Claim
1. Method for determining the precipitation rate and reflectivity factor of a hydrometeor using pulsed radar operating at a wavelength which is attenuated by the said hydrometeor, the said radar being a dual polarization radar delivering a double series of measurements of the attenuated reflectivity factor (ZHa (r), ZVa (r)) for the various range gates according to each of the polarizations, the said method being characterized in that it comprises the following steps:
- A) in each range gate of the radar, determining a first estimate of the precipitation rate (Rs) on the basis of the reflectivity factor measured for a single polarization, by a combination of the equations connecting the reflectivity factor with the precipitation rate and the attenuation coefficient for a single polarization with the precipitation rate;
B) on the basis of the said first estimate of the precipitation rate, obtaining an estimated value of the unattenuated differential reflectivity factor (ZDRs);
C) from the said estimated value of the unattenuated differential reflectivity factor (ZDRs) and the radar measurement of the attenuated differential reflectivity factor (ZDRa), deducing an estimated value of the differential polarimetric attenuation (ADP); and
D) attempting to obtain equality between the integral (I1 (r, R)) of the precipitation rate estimated in step A for a single polarization of the radar and the integral (I2 (r, R)) of the precipitation rate deduced from the said differential polarimetric attenuation (ADP), by iterative adjustment of one of the parameters (α
, β
) in the equation connecting the reflectivity factor with the precipitation rate, so as to make it possible to extract the corrected values of the unattenuated reflectivity factor (ZHs (r)) and the precipitation rate (Rs (r)).
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Abstract
A method for determining precipitation rate including on the basis of the signals received on the two polarization channels H and V of the radar, in firstly determining an estimate of the precipitation rates R.sub.α in each range gate i along the radar beam for a single polarization, then a first estimated value (I1) of the integral of the precipitation rates and, finally, on the basis of the attenuated reflectivity coefficient (ZHα (r)), an estimate of the unattenuated differential reflectivity coefficient (ZDRs (r)). Furthermore, the measured value of the attenuated differential reflectivity coefficient (ZDRs (r)) is determined, and the integral (I2) of the precipitation rates is deduced therefrom, then is compared with the first estimated value (I1) so as to iteratively adjust a parameter (α) of the method when applied to the polarization H alone. When α has been adjusted, corrected values of the unattenuated reflectivity coefficient and the precipitation rate are provided.
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Citations
20 Claims
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1. Method for determining the precipitation rate and reflectivity factor of a hydrometeor using pulsed radar operating at a wavelength which is attenuated by the said hydrometeor, the said radar being a dual polarization radar delivering a double series of measurements of the attenuated reflectivity factor (ZHa (r), ZVa (r)) for the various range gates according to each of the polarizations, the said method being characterized in that it comprises the following steps:
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A) in each range gate of the radar, determining a first estimate of the precipitation rate (Rs) on the basis of the reflectivity factor measured for a single polarization, by a combination of the equations connecting the reflectivity factor with the precipitation rate and the attenuation coefficient for a single polarization with the precipitation rate; B) on the basis of the said first estimate of the precipitation rate, obtaining an estimated value of the unattenuated differential reflectivity factor (ZDRs); C) from the said estimated value of the unattenuated differential reflectivity factor (ZDRs) and the radar measurement of the attenuated differential reflectivity factor (ZDRa), deducing an estimated value of the differential polarimetric attenuation (ADP); and D) attempting to obtain equality between the integral (I1 (r, R)) of the precipitation rate estimated in step A for a single polarization of the radar and the integral (I2 (r, R)) of the precipitation rate deduced from the said differential polarimetric attenuation (ADP), by iterative adjustment of one of the parameters (α
, β
) in the equation connecting the reflectivity factor with the precipitation rate, so as to make it possible to extract the corrected values of the unattenuated reflectivity factor (ZHs (r)) and the precipitation rate (Rs (r)). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification