CarpeDiem Project, Bologna 1/12/2004

WP-6 Anomalous Propagation

PBEZTPPI06_VRG-043 PBEZTPPI06_VRG-112

RADAR OBSERVATIONS & ANOMALOUS PROPAGATION

CarpeDiem Project, Bologna 1/12/2004

CarpeDiem Project, Bologna 1/12/2004

World-wide VRG 1km, August (ITU, 1997)

Weather Radar anomalous propagation (AP)BARCELONA RPC COMPUTED FROM RADIOSONDE OBSERVATIONS (RAOB):

- 00 Z & 12Z (41.38ºN, 2.12ºE)

- VAISALA RS-80 SONDES

- 10 S SAMPLING

- 1997 TO 2002 (2485 OBS)

85% VALID RAOB PROFILES (Ns, VRG,..)

- POSTPROCESSING

- STATISTICAL ANALYSIS

- COMPARISON VRG vs Ns

RAOB DATA

READ RAOB

QUALITY CONTROL

WRITE RPC REPORT

RPC REPORT

PROCESS RPC

RAOB PROCESSING

BLOCK DIAGRAM

CarpeDiem Project, Bologna 1/12/2004

CarpeDiem Project, Bologna 1/12/2004

Radar beam blockage and anaprop in complex terrain

±0.05º

YEARLY DIURNAL RANGESUMMER DIURNAL RANGE

±0.10º±0.05º

CarpeDiem Project, Bologna 1/12/2004

NEXRAD beam blockage

correction sensitivity analysis

(Bech et al. JTECH 2003)

Use of NWP forecasts & RAOB to monitor AP

Different MASS model domains.

Modified refractivity forecast and observed profile.

VRG = N / z ITU (1997), Steiner and Smith (2002)

ID = 78 z - M Johnson et al. (1999)

November 2002 to February 2003 (183 cases)

Forecasts of refractivity profiles based on 12 & 24 H MASS model output 00 & 12 Z

RAOB

CarpeDiem Project, Bologna 1/12/2004

Use of NWP forecasts & RAOB to monitor APCarpeDiem Project, Bologna 1/12/2004

CarpeDiem Project, Bologna 1/12/2004

P´i = P´i0 + P´i

NAME P´ i0 P i Cases ME MAE

A P i-1 P i - P i-1 180 9,92 10,00

B O i-1 P i - P i-1 164 0,03 4,98

C (O i-1 + O i-2 ) / 2 P i – (P i-1 + P i-2 ) / 2 151 0,01 4,44

D O i-2 P i - P i-2 162 0,07 5,14

E (O i-1 + O i-2 ) / 2 P i - P i-1 155 -0,02 4,83

F O i-1 P i – (P i-1 + P i-2 ) / 2 159 0,04 4,63

G (O i-1 + O i-2 + O i-3 ) / 3 P i – (P i-1 + P i-2 + P i-3 ) / 3 139 -0,20 4,13

H (O i-1 + O i-2 + O i-3 + O i-4 ) / 4 P i – (P i-1 + P i-2 + P i-3 + P i-4 ) / 4 128 -0,21 3,87

I (O i-1 + O i-2 + O i-3 + O i-4 + O i-5 ) / 5 P i – (P i-1 + P i-2 + P i-3 + P i-4 + P i-5 ) / 5 127 -0,29 3,96

DUCTING INDEX MODIFIED FORECASTS

PART 4. Forecasting RPC

CarpeDiem Project, Bologna 1/12/2004

CarpeDiem Project, Bologna 1/12/2004

Ground clutter and beam blocking – representativeness of different datasets to reproduce the beam path

N gradient (RAW)

-1000-800

-600-400-200

0200

400600

0 200 400 600 800 1000

height (m m.s.l.)

dN/d

h (k

m-1

)

9 July 2003, 00:00 UTC

RAW

0

25

50

75

100

125

0 25 50 75 100 125

distance from radar (km)

heig

ht (m

m.s

.l.)

LOWER LIMIT OF 3 dB - BEAM

datasets:

RAW RADIOSOUND. DATA

TEMP DATA

LOKAL MODEL DATA (LM)

CarpeDiem Project, Bologna 1/12/2004

N gradient (lokal model)

-1000-800-600-400-200

0200400600

0 200 400 600 800 1000

height (m m.s.l.)

dN/d

h (k

m-1)

LM

0100200300400500600

0 25 50 75 100 125

distance from radar (km)

heig

ht (m

m.s

.l.)

TEMP

0

25

50

0 25 50 75 100 125

distance from radar (km)

heig

ht (m

m.s

.l.)

N gradient (TEMP)

-1000-800-600-400-200

0200400600

0 200 400 600 800 1000

height (m m.s.l.)

dN/d

h (k

m-1

)

CarpeDiem Project, Bologna 1/12/2004

• Clutter echoes may be cleaned BUT echo heights may still be affected for some applications requiring precise height measurements (VAD assimilation,..).

• VRG induced errors comparable to antenna alignment errors.

• Beam blockage vs VRG variability simulated with an interception function.

• Blockage corrections were generally robust.

SUMMARY (1/2)

•Original model forecasts were biased towards subrefraction.

•Model output anticipated correctly average conditions & tendency.

• New modified forecasts improved significantly verification scores.

• In some cases RAOB persistency yielded better results than NWP forecasts.

SUMMARY (2/2)