Rainfall Measurements at NASA Wallops Island

Dover NEXRAD = 110 kmWakefield NEXRAD = 165 kmSterling NEXRAD = 215 km

Ali Tokay (JCET/UMBC, NASA/GSFC) and John Gerlach (NASA/WFF),

Annual precipitation = 98.65 cm

15

0

10

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

20

5

Annual precipitation days = 121.75

Wallops Island Precipitation Variability

74.07 cm (-24.58)

20

0

10

200420022001 2003

40

97.94 cm (-0.71) 122.20 cm (+23.54) 129.03 cm (+30.38)

30

Wallops Island Precipitation Days

(110, 61, 18, 4)

15

0

10

200420022001 2003

20

(118, 77, 28, 8) (143, 91, 38, 11) (116, 75, 30, 14)

5

Wallops Island Snowfall

Annual snowfall = 19.88 cm(0.20+3.33+7.64+7.87+0.84)

60

0

40

80

20

1994 2004

Wallops Island Precipitation Type

Concentration (m

-3mm

-1)

0 42 6

Drop Diameter (mm)

104

102

10-2

100

10-4

42 dBZ

August 13, 2004 (5 spectra, 1065 drops m-3, 1.23 g m-3, 25.9 mm h-1)

August 3, 2004 (23 spectra, 969 drops m-3, 1.12 g m-3, 23.6 mm h-1)

July 18, 2004 (10 spectra, 438 drops m-3, 0.58 g m-3, 13.8 mm h-1)

July 28, 2004 (21 spectra, 693 drops m-3, 0.73 g m-3, 16.5 mm h-1)

• Frontal (Cold, warm, stationary)• Solar heating• Coastal low• Tropical cyclones• Winter storms (dry and wet snow)

Wallops Island Precipitation Type• Frontal (cold, warm, stationary)• Solar heating• Coastal low• Tropical cyclones• Winter storms (dry and wet snow)

August 13, 2004 (5 spectra, 1065 drops m-3, 1.23 g m-3, 25.9 mm h-1)

August 3, 2004 (23 spectra, 969 drops m-3, 1.12 g m-3, 23.6 mm h-1)

July 18, 2004 (10 spectra, 438 drops m-3, 0.58 g m-3, 13.8 mm h-1)

October 9-10, 2004 (79 spectra, 666 drops m-3, 1.09 g m-3, 23.3 mm h-1)

July 28, 2004 (21 spectra, 693 drops m-3, 0.73 g m-3, 16.5 mm h-1)

0 42 6

Drop Diameter (mm)

104

102

10-2

100

10-4

42 dBZ

Wallops Island Precipitation Type• Frontal (cold, warm, stationary)• Solar heating• Coastal low• Tropical cyclones• Winter storms (dry and wet snow)

0 205 25

Maximum Particle Width (mm)

104

102

10-2

100

10-4

Parsivel 1 (514 spectra)

Parsivel 2 (494 spectra)

1510

December 26, 2004

Wallops Island - Instruments (NASA)

• Radars - S-band Polarimetric radar (NPOL) - S-band Doppler radar (SPANDAR) - C-band Doppler radar (TOGA)

- UHF reflector - Dual frequency Microwave Link (R. Rincon)

• Precipitation Gauges - Met 1 tipping bucket gauges (14 unit) - Qualimetrics tipping bucket gauges (11 unit) - Geonor weighing bucket gauge - Optical rain gauges (5 unit, R. Rincon)

• Disdrometers - Joss-Waldvogel disdrometers (9 unit, 2 for R. Rincon) - Optical (Parsivel) disdrometers (2 unit) - 2-D video disdrometer (1 unit)

- Video disdrometer (L. Bliven)

Wallops Island - Instruments (Loan, past & present)

• Radars - X-band polarimetric radar (NOAA-ETL, PI: S. Matrosov and B. Martner) - X-band polarimetric radar (Greek Met. Service, PI: E. Anagnostou)

- S-band profiler (NOAA-AL, PI: K. Gage) - 24.5 GHz profiler (Metek)

• Precipitation Gauges - Hydrological services tipping bucket gauges (2 unit) - Geonor weighing bucket gauge - Drop counting gauge (RL, PI: C. Wilson)

• Disdrometers - Pludix (Nubila, PI: F. Prodi) - POSS (2 unit, Canadian Met. Service, PI: P. Joe and B. Sheppard)

Performance of Tipping Bucket Gauges

Julian Day

a

140 180160120

300

200

100

0

b c

238 mm (D1984)

238 mm (D1327)

300

200

100

0

242 mm (HS175)

236 mm (HS6218)

Julian Day

140 180160120

300

200

100

0

Julian Day

140 180160120

139 mm (Q2159)232 mm (Q2192)238 mm (Q2196)

219 mm (Q2220)

446 mm (Q2855)

180 mm (Q2861)

198 mm (Q2862)128 mm (Q2866)

214 mm (Q2881)

240 mm (Q2884)

D1984 Rain Total (mm)

50

10

5

1

20

2

20 rain events

1 50105 202

a bc

D1984 Rain Total (mm)

50

10

5

1

20

2

1 50105 202

HS175

HS6218

D1984 Rain Total (mm)

1 50105 202

50

10

5

1

20

2

Q2196

Q2220Q2855Q2884

€

bias =X1− X2

X1X1>X2

bias (%) gauge1 JW1 JW2 Parsivel1 Parsivel2 POSS1 POSS2gauge1 - 1.82 12.73 14.42 5.73 19.63 25.09 Excellent bias<5%

JW1 1.82 - 11.11 12.83 3.98 18.14 23.70 Very good 5% < bias < 10%JW2 12.73 11.11 - 1.94 7.42 7.91 14.17 Good 10% < bias < 15%

Parsivel1 14.42 12.83 1.94 - 9.22 6.09 12.46 Reasonable 15% < bias < 20%Parsivel2 5.73 3.98 7.42 9.22 - 14.74 20.53 Not acceptable bias > 20%

POSS1 19.63 18.14 7.91 6.09 14.74 - 6.79

POSS2 25.09 23.70 14.17 12.46 20.53 6.79 -

Performance of Impact-type, Laser-Optical, and Radar Disdrometers

2DVD (4387 spectra)

0 2 4 6 8Drop Diameter (mm)

a104

10-4

10-2

100

102

b

JWD (4446 spectra)

0 10 20 30 40

2DVD Rain Total (mm)

0

10

20

30

40

15 rain events

d

0 10 20 30 40

2DVD Rain Total (mm)

0

10

20

30

40

10 rain events

2DVD (2265 spectra)JWD (2274 spectra)

0 2 4 6 8Drop Diameter (mm)

c104

10-4

10-2

100

102 Parsivel (2299 spectra)

Performance of Impact-type, 2-D Video, and Laser-Optical Disdrometers

Wallops Island Data Acquisition Network: Phase I

S

N

MasterSite

650 m 1056 m

1704 m

Microwave linktransmitter tower

Microwave linkreceiver tower

X85

W71Y40

ML tipping bucket rain gauge

TSVO tipping bucket rain gauge

ML optical rain gauge

TSVO 2-D video disdrometer

ML Joss-Waldvogel disdrometer

TSVO Joss-Waldvogel disdrometer

TSVO Geonor precipitation gauge TSVO Parsivel disdrometer

Canadian POSS disdrometer

Small-Scale Variability of Rainfall and

Reflectivity

Distance (km)

0.0 0.5 1.0 1.5 2.00

3

2

4

6

1

5

1 minute

3 minutes

6 minutes

10 minutes

15 minutes

a

Distance (km)

102

1 minute

3 minutes

6 minutes

10 minutes

15 minutes

b

103

104

105

0.0 0.5 1.0 1.5 2.0

Wallops Island Data Acquisition Network: Phase II

S

N

MasterSite

650 m

5288 m

1056 m

369 m

1244 m

4942 m

4296 m994 m

3240 m2048 m

5072 m

369 m

Microwave linktransmitter towerMicrowave link

receiver tower

Y40Z65

W71

V25 V50

ML tipping bucket rain gauge

TSVO tipping bucket rain gauge

ML optical rain gauge

TSVO 2-D video disdrometer

ML Joss-Waldvogel disdrometer

TSVO Joss-Waldvogel disdrometer

X85

TOGA/SPANDAR

1244 m2000 m

60623624

5072

317831092964

TSVO Geonor precipitation gauge

TSVO Parsivel disdrometer

Canadian POSS disdrometer

Wallops Island - Instruments (NOAA)

• Radars - S-band Doppler radar at Dover, Delaware - S-band Doppler radar at Wakefield, Virginia

• Precipitation Gauges - ASOS site - CRN site at Oyster, Virginia

• US NLDN sensor site

• Upper air sounding site

Doppler Radar Rain Gauge

Network

77˚W 76˚W 75˚W78˚W79˚W 74˚W

37˚N

38˚N

36˚N

39˚N

35˚N

Oyster

longitude

WarsawWallops Island

Wallops

Wakefield

Onley

Murfreesboro

Elizabeth City

Petersburg

Holland

Pokomoke City

Newport News

Back Bay Wildlife

Kiptopeke

Salisbury

PainterAshland Shacklefords

Williamsburg

Milford HavenRichmond

Norfolk

Ocean City NPOL [3 + 8 + 9]

NEXRAD [4 + 5 + 6]

SPANDAR [3 + 5 + 5]

Cooperative (6)

ASOS (7)

NASA (5)

small scale network (1)

AWOS (1)

VAES (3)

FMO (1)

Monthly and Daily Rainfall

Statistics

• Standard deviation of daily rain total difference (STRTD)

SDRTD = [Var(G1)+Var(G2)-2Cov(G1,G2)]1/2

• Monthly rainfall bias

• Mean daily rain total difference and its standard deviation

• Pearson correlation coefficient of daily rainfall

€

<ΔRT >=1N

G1−G2G1i =1

N∑

€

bias=G1−G2

G1where G1>G2

where N - number of rainy days with rainfall > 1.2 mm

Oyster, Virginia Climate Reference Network (CRN) site

62 rain days

GCRN Rain Total (mm)

G04B Rain Total (mm)

1 10010

100

10

1

SDRTD = 2.88 mmcorrelation = 0.991<ΔRT> = 3.2%; 18.0%

month G04A mm

G04B mm

GCRN mm

Bias (A,B)

%

Bias (A,CRN)

%

Bias (B,CRN)

% March 04 49.276 --- 42.000 --- 14.77 --- April 04 92.710 --- 82.000 --- 11.55 --- May 04 62.992 --- 62.400 --- 0.94 --- June04 128.778 --- 114.600 --- 11.01 --- July04 257.048 --- 228.800 --- 10.99 ---

September04 52.324 53.086 51.400 1.46 1.77 3.18 October 04 128.778 124.714 129.000 3.15 0.17 3.44

November 04 95.758 97.790 113.800 2.12 18.84 16.37 December 04 69.088 66.802 65.600 3.31 5.05 1.80

Overall 936.752 --- 889.6 --- 5.03 ---

Wakefield, Virginia Automated Surface Observing System (ASOS) site

64 rain days

G01B Rain Total (mm)

G01A Rain Total (mm)

a

1 10010

100

10

1

b

64 rain days

GNWS Rain Total (mm)

G01A Rain Total (mm)

1 10010

100

10

1

c

64 rain days

GNWS Rain Total (mm)

G01B Rain Total (mm)

1 10010

100

10

1

SDRTD = 1.35 mmcorrelation = 0.998<ΔRT> = -4.1%; 7.1%

SDRTD = 2.95 mm = 0.994correlation

<ΔRT> = -15.3%; 27.6%

SDRTD = 2.87 mm = 0.992correlation

<ΔRT> = -10.9%; 27.2%

monthG01Amm

G01Bmm

GNWSmm

Bias(A,B)

%

Bias(A,NWS)

%

Bias(B,NWS)

%May 04 42.672 42.926 53.848 0.59 26.19 25.44June04 191.262 196.088 219.456 2.52 14.74 11.92July04 181.356 186.690 197.358 2.94 8.82 5.71

August04 256.286 260.350 277.114 1.59 8.13 6.44September04 109.474 113.030 121.666 3.47 11.14 7.64October 04 90.424 97.028 97.282 7.30 7.58 0.26

November 04 79.502 90.170 89.154 13.42 12.14 -1.13December 04 68.834 75.946 77.216 10.33 12.18 1.67

Overall 1019.810 1062.228 1133.094 4.16 11.11 6.67

Gauge and 88-D Rainfall Totals in Tropical Storm Guston

Gauge Rain Total (mm)

a

1 10010

100

10

1

b c

13 gauge sites

101

103

94

113

88

67

71

4448

44

4060

108

100

10

1

GaugeRainTotal (mm)

1 10010

GaugeRainTotal (mm)

1 10010

100

10

1

Z =300R 1.4 Z =250R 1.2 Z =229R 1.4

88-D rainfall products - 1.0,1.5, 2.0 km grid spacing, 1.0, 1.5, 2.0 CAPPI

Gauge sites - NASA, ASOS, AWOS, co-op, weather-bug, state

Wallops IslandWallops

Salisbury

Ocean City

EastonWashington

Baltimore

BWI Annapolis

Oyster

Wakefield

Newport News

Ashland

Georgetown

Norfolk

77˚W 76˚W 75˚W78˚W80˚W 73˚W79˚W 74˚W

longitude

38˚N

39˚N

37˚N

41˚N

36˚N

40˚N

Sterling

Proposed Wallops Island Triple Radar Rain Gauge Network

Wallops IslandWallops

Salisbury

Ocean City

EastonSterling

Oyster

Wakefield

Newport News

Norfolk

Elizabeth City

Ashland

Richmond

Georgetown

77˚W 76˚W 75˚W78˚W80˚W 73˚W79˚W 74˚W

longitude

37˚N

38˚N

36˚N

40˚N

35˚N

39˚N

Publications

Journal papers:

Tokay, A., R. Chamberlain, and M. Schoenhuber, 2000: Laboratory and field measurements of raindrop oscillations. Phys. Chem. Earth (B), 25, 867-870.

Matrosov, S. Y., K. A. Clark, B. E. Martner, and A. Tokay, 2002: X-band polarimetric radar measurements of rainfall. J. Appl. Meteor., 41, 941-952.

Rincon, R., and R. Lang, 2002: Microwave link dual-wavelength measurements of path-average attenuation for the estimation of drop size distributions and rainfall. IEEE Trans. Geoscience and Remote Sensing, 40, 760-769.

Gage, K.S., W.L. Clark, C.R. Williams and A. Tokay, 2004: Determining Reflectivity Measurement Error from Serial Measurements Using Paired Disdrometers and Profilers. Geo. Res. Lett., 31, doi:10.1029/020591.

Tokay, A., P. G. Bashor, and K. R. Wolff, 2005: Error Characteristics of Rainfall measurements by collocated Joss-Waldvogel disdrometers. J. Atmos. Oceanic. Technol., 22, 513-527.

Larsen, M. L., A. B. Kostinski, and A. Tokay, 2005: Observations and analysis of steady rain. J. Atmos. Sci., (accepted for publication).

Tokay, A.,and P. G. Bashor, 2005: An experimental study of small-scale variability of rainfall. J. Appl. Meteor. (submitted July 2005).

Goldhirsh, J., 1983: On modeled slant path attenuation distributions, IEEE Trans. Antennas and Propagation, 31, 918-921.

Conference papers and presentations

Tokay, A., K. Chamberlain, P. Bashor, R. Rincon, and D. Wolff, 2000: Measurements of Drop size distribution and drop shape at the NASA Wallops Flight Facility, TRMM science meeting, College Park, Maryland

Tokay, A., K. Chamberlain, P. Bashor, R. Rincon, and D. Wolff, 2001: Drop size distribution measurements at the NASA Wallops Flight Facility, GPM planning meeting,

College Park, Maryland Tokay, A., K. Chamberlain, P. Bashor, R. Rincon, and D. Wolff, 2001: Precipitation measurements at the NASA Wallops Flight Facility. Abstracts, 7th International Conference on Precipitation, Rockport, Maine, 2-2 Tokay, A., K. R. Wolff, P. Bashor, and R. Rincon, 2002: An overview of the precipitation measurements at the NASA Wallops Island. Abstracts, 2nd European Radar Meteorology Conference, Delft, The Netherlands.

Tokay, A., R. Wolff, P. Bashor, and O. Dursun, 2003: On the measurement errors of the Joss-Waldvogel disdrometer. Preprints, 31th International Conference on Radar Meteorology. Seattle, WA, American Meteorological Society, 437-440.

Tokay, D. B. Wolff, P. Bashor, and R. Rincon, 2003: Wallops Island: Proposed ground validation site for the NASA precipitation program, European Global Precipitation Mission (EGPM) meeting in ESA/ESTEC, The Netherlands.

Tokay, A, D. B. Wolff, D. Marks, J. Gerlach, J. J. Wang, P. Bashor, and R. Wolff 2003: Greater Wallops Island: A proposed mid-latitudinal ground validation site

for NASA precipitation program. GPM Ground Validation (GV) meeting in Abingdon, UK.