US 10,649,070 B2 · Method for regional attenuation correction of radar using a microwave links network

Abstract

The complex temporal-spatial variation of raindrop size distribution will affect the precision of quantitative precipitation estimation (QPE) produced from radar data, making it difficult to correct echo attenuation. This invention presents a method for regional attenuation correction of weather radar using a multiple microwave links (ML) network. By measuring the rain attenuation of multiple microwave links in a specific frequency, matching with the weather radar in time and space and processed with discretization. Based on a series of attenuation values of the microwave link network and combined iterations, the attenuation coefficient of each grids is obtained; the total attenuation value of the path is obtained by combining the distance between the radar and each grid point, by which the reginal attenuation of radar echo can be corrected by the ML network efficiently.

A method for regional attenuation correction of a weather radar, comprising

1) constructing a multiple microwave links network, based on the tomographic reconstruction, each microwave link includes a transmitter and receiver;
2) measuring microwave attenuation (A) of the multiple microwave links in specific frequencies (T and Twet), and calculating microwave attenuation (A) by:
A=T−Twet (B)(2)
wherein A (dB) is attenuation induced by rain in a link path, and Twet (dB) is the attenuation reference during the rain, which is calculated by the difference between rainy day and clear day;
3) constructing a joint observation network between the multiple microwave links and observed weather radar data
by matching the observed weather radar data to microwave attenuation data according to location and time information, and
then performing
discretizing the weather radar data observed by presenting in a discrete grid, for a corresponding regional area by
obtaining the attenuation induced by rain is Ai (dB), for an ith link with length Li (km),
Ai=∫LiKjdl (C)
wherein there are M microwave links are provided in the observation area, and the observation area is discretized in N grids;
Kj (dB/km) is a rain attenuation coefficient in each grid;
and
obtaining the rain attenuation of ith link Ai (dB) for a discretized grid area by calculating:
Ai=Σj=1lijKj (D)
wherein lij (km) is a length of the ith link in a jth grid cell, Kj (dB/km) is the rain attenuation coefficient in each grid cell;
4) using a rain attenuation from the multiple microwave links network, wherein rain attenuation of the M microwave links can be expressed in vector form:
LK=A (E)
A=(Ai)M×1 is the total attenuation column vector;
L=(lij)M×N is the distance matrix;
K=(kj)N×1 is the attenuation coefficient column vector,
using a joint iterative reconstruction algorithm to obtain rain attenuation coefficient kj of each grid cell and
converting solution of k to the equation (F) as follows:
{
l
11
⁢
k
1
+
l
12
⁢
k
2
+
…
+
l
1
⁢
j
⁢
k
j
+
…
+
l
1
⁢
N
⁢
k
N
=
A
1
l
21
⁢
k
1
+
l
22
⁢
k
2
+
…
+
l
2
⁢
j
⁢
k
j
+
…
+
l
2
⁢
N
⁢
k
N
=
A
2
⋮
l
i
⁢
⁢
1
⁢
k
1
+
l
i
⁢
⁢
2
⁢
k
2
+
…
+
l
ij
⁢
k
j
+
…
+
l
iN
⁢
k
N
=
A
i
⋮
l
M
⁢
⁢
1
⁢
k
1
+
l
M
⁢
⁢
2
⁢
k
2
+
…
+
l
ij
⁢
k
j
+
…
+
l
MN
⁢
k
N
=
A
M
(
F
)
wherein lij (km) is a length of the ith link in a jth grid cell, M is the number of microwave links and N is a number of the grid cells,
taking Simultaneous Iterative Reconstruction Technique (SIRT) to construct a cost function using the least-square criterion and an iterative formula can be written as
k
j
⁡
(
t
)
=
k
j
⁡
(
t
-
1
)
+
1
M
⁢
∑
i
=
1
N
⁢
⁢
(
A
i
⁡
(
t
)
-
∑
p
=
1
M
⁢
⁢
l
ip
⁡
(
t
)
⁢
k
p
⁡
(
t
-
1
)
)
·
l
ij
⁡
(
t
)
∑
p
=
1
M
⁢
l
ip
⁡
(
t
)
2
(
G
)
5) calculating the path attenuation of the ith link between the weather radar and each grid point:
Att
ij
=
∑
i
=
1
X
⁢
⁢
∑
j
=
1
N
⁢
⁢
k
j
×
d
ij
.
(
12
)
wherein dij is the length of the ith link between the weather radar and the grid point through the jth grid;
6) providing X lines between each grid point and the weather radar, substituting the attenuation coefficients obtained into Eq. (10) and obtaining the path attenuation of the ith link between the weather radar and each grid:
Attij=Σi=1XΣj=1Nkj*dij (10)
wherein dij (km) is the length of a ith link between the weather radar and the grid through a jth grid;
7) calculating corrected radar reflectivity factor zij by summing radar-measured reflectivity factor zmij and total attenuation of two-way path on the ith link between the weather radar and the grid point:
zij=zmij+2×Attij. (13)

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Method for regional attenuation correction of radar using a microwave links network

Life of this patent

Method for regional attenuation correction of radar using a microwave links network

Life of this patent

Abstract

Claims5