Radar Refractivity: validation
and application to forecasting
Crystalyne R. Pettet, Tammy M. Weckwerth,
and James W. Wilson—NCAR/ATD
Frédéric Fabry and ShinJu Park—McGill
University
Validation
Sfc comparisons
12
320
22 Verle
11
320
21
11
300
22 Rusty
11
22
11
ISFF1
32
2
260
20
Lincoln
Verle
8
240
1600
246
254
262
270
278
286
294
1800
246
320
40 km
S-Pol
2000
33
-3
33
0
33
5
33
4
33
10
31
11
33
-1
33
2
20
0000
278
286
g kg-1
S-Pol
2000
32
-2
0000
2200
33
7
0200
4
1800
q
33
3
q
20
33
3
30
11
Lincoln
280
1600
2200
Time (UTC)
6
g kg-1
r = 0.94
N = 282.17
N = 280.85
4
2
1800
30
oC
25
S-Pol
2000
35
320
2200
0000
0200
20
15
0400
30
300
12
q
oC
25
0000
10
T
8
280
20
260
240
1600
35
30
oC
25
S-Pol
6
Homestead
r = 0.95
N = 285.59
N = 283.61
1800
g kg-1
4
2000
0200
40 km
35
0000
2200
20
2 15
0400
0200
12
320
10
8
30
300
ISFF1
q
oC
25
10
8
30
oC
25
280
6
g kg-1
35
T
UWKA
4
S-Pol
2000
8
294 N units
2 15
0400
12
31
10
32 MM9 31
4
MM1 10
P-3
240
1600
10
35
Time (UTC)
320
T
2
15
0400
0200
ISFF2
Time (UTC)
33
-1
r = 0.97
N = 272.10
N = 269.50
0000
12
6
240
280
2200
oC
240
Playhouse
r = 0.99
N = 271.14
N = 268.52
300
2000
T
2 15
0400
10
q
1800
1800
20
Time (UTC)
Time (UTC)
262
270
254
0200
T
1600
300
260
12
260
40 km
2200
280
34
0
30
20
4
8
260
320
g kg-1
300
S-Pol N varies
most strongly
with moisture
35
25
q
40 km
4
6
r = 0.99
N = 264.01
N = 260.88
260
g kg-1
r = 0.91
N = 278.82
N = 272.63
Time (UTC)
12
10
20
32
4
280
30
oC
6
240
1600
35
25
S-Pol
31
10
T
8
280
MM1 & MM5
31
31
9
31
6
31
9
10
P-3
10
q
32
9
33
2
Playhouse21 ISFF2
22
11
21
11
21
11 S-Pol 11 Homestead
T
300
Surface Station
Intercomparisons
22 May 2002
22 ISFF3
11
ISFF3
6
20
2 15
0400
260
240
1600
1800
g kg-1
4
S-Pol
r = 0.92
N = 288.19
N = 282.48
2000
2200
Time (UTC)
0000
0200
20
2
15
0400
Sfc comparisons
30
340
Surface Station
Intercomparisons329
14 June 2002
22 ISFF3
11
22 Verle
11
21
11
22 Rusty
11
ISFF1
320
20
Lincoln
S-Pol
300
40 km
254
262
270
278
286
High
correlation
between
S-Pol N
and
station N
294
340
254
Playhouse
320
33
0
33
4
33
10
20
12
1600
1800
2000
30
340
25
g kg-1
oC
10
20
8
r = 0.93
N = 301.62
N = 294.46
ISFF2
320
14
12
S-Pol
25
g kg-1
oC
10
20
q
300
8
15
T
15
6
6
1800
Time (UTC)
262
270
r = 0.99
N = 312.50
N = 305.64
1400
14
10
280
2000
1000
1200
1400
1600
1800
2000
Time (UTC)
278
286
30
294 N units
30
340
14
12
g kg-1
10
300
8
T
33
7
280
1000
Homestead
25
oC
320
r = 0.97
N = 311.93
N = 302.74
12
q
S-Pol
20
14
g kg-1
10
1200
32
-2
1400
1600
1800
25
oC
20
320
P-3
1200
1200
1000
2000
1400
1400
1600
1800
2000
30
11
30
340
r = 0.95
N = 313.66
N = 306.72
14
UWKA
ISFF1
g kg-1
12
25
oC
10
8
20
r = 0.69
33
N = 318.66
3
N = 306.66
280
10
280
Time (UTC)
31
10
q
32 MM9 31
4
MM1 10
33
3
320
q
14
25
12
o
-1
C
g kg
S-Pol
20
300
15
10
8
T
6
Time (UTC)
1800
40 km
2000
20
15
6
10
1600
15
6
10
30
S-Pol
33
-1
T
8
T
Time (UTC)
Lincoln
300
300
15
6
340
1000
40 km
1600
1200
q
31
11
33
-1
15
Time (UTC)
30
S-Pol
33
-3
33
5
1400
246
8
10
1000
10
34
0
33
2
q
280
280
246
S-Pol
300
40 km
1200
oC
20
6
T
1000
25
T
MM1 & MM5
31
31
9
31
6
31
9
10
r = 0.93
31
N = 307.76
10
N = 300.77
20
32
4
q
Verle 32
2
12
10
P-3
340
14
g kg-1
33
2
Playhouse21 ISFF2
22
11
21
11
21
11 S-Pol 11 Homestead
22
11
ISFF3
320
r = 0.99
N = 302.16
N = 295.80
10
280
1000
1200
1400
1600
Time (UTC)
1800
2000
246
0
254
2
235940-001339 UTC
r = 0.92
MM1 N = 276.98
S-Pol N = 275.59
290
280
262
4
Mobile mesonets
270
278
Distance (km)
286
6
294
8
246
254
262
270
278
33
7
270
32
-2
33
-3
-100.70
-100.68
0
280
2
235119-000118
UTC
33
MM9 N
=
262.54
-1
270 S-Pol N = 260.24
33
2
294 N units
10
34
0
260
286
-100.66
-100.64
33
33 Longitude 5
33
0
33
4
Distance (km) 10
4
6
31
11
-100.62
8
-100.60
33
3
10
31
10
MM9
32
31
4
MM1 10
P-3
30
11
33
-1
20
UWKA
20
33
3
260
40 km
250
-100.78
246
-100.76
254
-100.74
-100.72
-100.70
262 Longitude
270
278
286
40 km
-100.68
294
246
254
262
270
278
286
294 N units
S-Pol N compares favorably with areas of
relatively constant mobile N
Mobile
22 - 23mesonets
May 2002
290
0
285
280
2
203239-203849 UTC
r = 0.94
MM1 N = 270.66
S-Pol N = 270.63
4
Distance (km)
6
8
10
32
9
22 ISFF3
11
275
270
22 Verle
11
265
33
2
260
-100.82
290
285
280
0
-100.80
2
203243-203857
22 RustyUTC
r = 0.92
11
MM5 N = 273.23 22
S-Pol N = 270.55 11
-100.78
-100.76
21 ISFF2-100.74
Playhouse
22
Longitude11
21
11
21
11 S-Pol 11 Homestead
Distance (km)
4
621
8
11 ISFF1
Lincoln
P-3
-100.72
MM1 & MM5
31
31
9
31
6
31
9
10
31
10
10
32
2
20
20
32
4
275
40 km
270
40 km
265
260
-100.82
246
-100.80
254
262-100.78270 -100.76
278
Longitude
-100.74
286
294-100.72
246
254
262
270
278
S-Pol N gradients are smoothed
286
294 N units
40 km
246
254
262
270
278
40 km
UWKA
286
Distance (km)
20
10
294
246
254
262
270
278
286
294 N units
30
300
234439-235230 UTC
r = 0.89
290 z = 168 m AGL = 0.05 z i
UWKA N = 274.71
S-Pol N = 271.75
280
34
0
32
-2
33
-3
270
260
33
0
250
-100.75
33
7
33
-100.70-1
-100.65
33
2
33
4
33
5
33
3
33
10
31
11
-100.60
-100.55
Longitude
20
31
10
32 MM9 31
4
MM1 10
P-3
-100.50
-100.45
30
11
33
-1
20
33
3
S-Pol N gradient smoothed
over ~10 km
40 km
246
254
262
270
278
286
294
UWKA
40 km
246
254
262
270
278
286
S-Pol N compares favorably with areas of
relatively constant UWKA N
294 N units
AERI—Atmospheric Emitted
Radiance Interferometer
AERI 22 May
1000
800
600
400
200
0
0.0
2.4
4.8
3
7.2
4
9.6
12.0 14.4
Time (UTC)
16.8
19.2
5 6 7 8 9 10 11 12
H20 mixing ratio (g kg -1)
21.6
24.0
AERI
S-Pol and AERI N 7 June - 13 June 2002
340
320
300
280
260
6/7
6/9
z = 44 m AGL; r = 0.91
z = 88 m AGL; r = 0.92
z = 132 m AGL; r = 0.92
6/11
UTC Date
z = 176 m AGL; r = 0.91
z = 220 m AGL; r = 0.89
z = 265 m AGL; r = 0.87
6/13
z = 310 m AGL; r = 0.83
z = 355 m AGL; r = 0.80
z = 400 m AGL; r = 0.77
• Transition between 220-355 m from high to
low r values
P-3
22 - 23 May 2002
0
300
290
280
10
Distance (km)
30
40
20
50
60
201500-202429 UTC
r = 0.98
z = 1228 m MSL = 0.57 z i
P3 N = 267.09
S-Pol N = 271.68
32
9
22 ISFF3
11
270
22 Verle
11
260
250
33
2
P-3
Playhouse21 ISFF2
22
11
21
11
21
-100.8
-100.6
11 S-Pol 11 Homestead
Longitude
-101.0
21
11
22 Rusty
11
-100.4
ISFF1
• If CBL is well-mixed,
N represents at least
half the depth of the
CBL.
22
11
20
Lincoln
MM1 & MM5
31
31
9
31
6
31
9
10
31
10
32
2
20
32
4
40 km
246
254
262
270
278
286
294
40 km
246
254
262
270
278
286
294 N units
AERI—diurnal and height
differences
S-Pol and AERI N Composite
320
z = 44 m AGL
z = 88 m AGL
z = 132 m AGL
z = 220 m AGL
310
300
290
280
0
5
10
15
Hour of Day (UTC)
20
• N bias is strongest at night and improves
with mixing of CBL
• Strongest relationship occurs at low levels
AERI—diurnal and height
differences
S-Pol and AERI N Composite
320
z = 44 m AGL
z = 88 m AGL
z = 132 m AGL
z = 220 m AGL
310
300
290
280
0
5
10
15
Hour of Day (UTC)
20
• Low levels—strong relationship from one hour
after sunrise until 2 hours after sunset
• Increasing height—strong relationship begins
later in the morning and drops off by 2200 UTC
Soundings
• Similar results to AERI—lowest 200-250 m
S-Pol and ISS N 14 June 2002
330
z = 40 m; r = 0.90
z = 220 m; r = 0.92
z = 450 m; r = 0.77
320
S-Pol
310
300
290
280
270
12
16
14
Time (UTC)
18
SRL
• Strong correspondence between SRL mixing ratio
magnitude, surface station mixing ratio, and S-Pol
N
Forecasting Utility
Boundary development
CI—10 June 2002
a) 2018 UTC
CI—
10 June
2002
Z
b) 2018 UTC
N
36
17
36
17
37
16
37
16
35
16
36
15
35
17
35
17
35
16
35
18
35
17
20
36
16
36
15
35
17
-5
5
15
36
16
40 km
25
35
45 dBZ
Z
c) 2047 UTC
266
274
282
290
298
N
37
15
35
15 35
17
35
17
35
15
36
17
36
17
20
36
15
36
15
35
17
-5
5
15
35
17
36
15
40 km
25
35
45 dBZ
Z
e) 2108 UTC
266
274
282
290
298
306
314 N units
N
f) 2108 UTC
37
16
37
16
37
15
37
15
35
16
35
17
35
17
36
17
35
16
36
17
37
16
20
37
15
35
17
-5
5
15
25
35
17
36
17
36
17
20
37
15
40 km
-15
36
17
36
17
20
40 km
37
16
314 N units
36
16
37
15
-15
306
d) 2047 UTC
36
16
36
15
35
18
35
17
20
40 km
-15
35
17
40 km
35
45 dBZ
266
274
282
290
298
306
314 N units
CI—12-13 June 2002
CI—
12-13
June 2002
a) 2347 UTC
33
17
34
16
-5
5
15
5
33
18
15
32 33
17 17
35
45 dBZ
Z
15
25
274
282
290
266
314 N units
N
33
17
33
18
35
17
298
306
314 N units
N
40 km
32 33
17 17
45 dBZ
306
40 km
20
34
17
35
35
17
34
12
f) 0021 UTC
33
17
298
34
14
33
16
33
12
5
266
33
18
20
33
16
33
18
290
33 33
17 17
33
16
25
34
15
-5
282
d) 0001 UTC
35
17
40 km
20
33
16
274
33
16
34
12
-5
266
34
16
34
13
33
17
34
14
e) 0021 UTC
-15
45 dBZ
Z
40 km
33 33
17 17
33
16
35
33
17
35
14
34
15
25
20
33
16
33
17
33
17
35
17
34
13
c) 0002 UTC
-15
33
18
N
40 km
20
33
16
35
14
34
15
b) 2346 UTC
33
17
20
33
16
-15
Z
40 km
33
16
33
18
34
15
34
17
33
12
274
282
290
298
306
314 N units
Summary
• Radar refractivity shows excellent
correlation with refractivity calculated from
other datasets
• Vertical depth represented by radar
refractivity is typically below 200-250 m
AGL, but may be dependent upon the
extent of vertical mixing
• Horizontal scale of refractivity varies, and
appears to be as high as 2 km at times
and lower than 4 km at other times
Summary
• Radar refractivity shows great promise as
a potential nowcasting and forecasting tool
For more information…
• Contact me at pettet@ucar.edu to get a
pdf of the manuscript that has been
submitted to JAM that this talk is based
on.