Water Vapor Intercomparison Workshop, Boulder, 2-3 October 2003

Refractivity During IHOP_2002

Tammy M. Weckwerth (NCAR/ATD), Crystalyne R. Pettet (NCAR/ATD), Frédéric Fabry (McGill University),

ShinJu Park (McGill University) and James W. Wilson (NCAR/ATD)

Intercomparisons

Fixed and mobile surface stationsFixed and mobile surface stations

AERIBAGOAERIBAGO

SRLSRL

AircraftAircraft

Intercomparisons

Mean Bias Stn-Radar = 1.68 N units

Intercomparisons

Bias is not related to propagation effects since it’s not diurnally dependentBias is worse at higher humidities

Surface Station Intercomparisons

Surface Station Intercomparisons

Surface StationIntercomparisons

22 May 2002

1600 1800 2000 2200 0000

Time (UTC)

240

260

280

300

320

Refr

act

ivity

0200 0400

ISFF1

S-Pol

r = 0.77

N = 283.51N = 288.09

1600 1800 2000 2200 0000Time (UTC)

240

260

280

300

320

Refr

act

ivity

0200 0400

ISFF2

S-Pol

r = 0.85

N = 280.15N = 282.08

1600 1800 2000 2200 0000

Time (UTC)

240

260

280

300

320

Refr

act

ivity

0200 0400

S-Pol

ISFF3

r = 0.86

N = 273.13N = 278.47

1600 1800 2000 2200 0000Time (UTC)

240

260

280

300

320

Refr

act

ivity

S-Pol

Verle

0200 0400

r = 0.99

N = 258.88N = 264.01

1600 1800 2000 2200Time (UTC)

240

260

280

300

320

Refr

act

ivity

0000 0200 0400

Playhouse

S-Pol

r = 0.98

N = 269.88N = 271.14

1600 1800 2000 2200 0000Time (UTC)

240

260

280

300

320

Refr

act

ivity

0200 0400

S-Pol

Homestead

r = 0.92

N = 282.18N = 285.59

1600 1800 2000 2200 0000Time (UTC)

240

260

280

300

320

Refr

act

ivity

0200 0400

Lincoln

S-Pol

r = 0.96

N = 269.74

• Excellent correlations• Radar has negative bias

-100.70 -100.66 -100.62Longitude

250

260

270

280

290

Refr

acti

vit

y

0 2 4 6 8Distance (km)

Refractivity at 000509 UTCMM1 center at 000651 UTC

S-Pol

Probe 1

Mobile Mesonet comparisons

Correlation = 0.81

-100.75 -100.70 -100.65 -100.60Longitude

250

260

270

280

290

Refr

acti

vit

y0 2 4 6 8 10 12 14

Distance (km)

Refractivity at 224830 UTCMM8 center at 224859 UTC

Probe 8

S-Pol

Correlation = 0.88

1600 1800 2000 2200 0000

Time (UTC)

250

260

270

280

290

300

0200 0400

Refr

act

ivit

y

AERI 175 mS-Pol

AERI 310 mAERI 670 m

AERIBAGO comparisons

Correlation=0.42Correlation=0.75Correlation=0.89

SRL comparisons22 May 2002 Scanning Raman Lidar

20 22 24 26 28Time (UTC)

0

500

1000

1500

2000

2500

3000

He

ight

(m A

GL)

250

260

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S-P

ol R

efr

act

ivity

5

6

7

8

9

10

11

12

5.0 6.3 7.6 8.9 10.2 12.0H20 mixing ratio (g kg-1)

H20

mix

ing

ra

tio

(g

kg

-1)

S-Pol N

UWKA comparisons

-100.65-100.60-100.55-100.50-100.45250

260

270

280

290

3000 5 10 15 20 25

Distance (km)

Refractivity at 224230 UTCUWKA Zavg = 163 m AGLUWKA at 224330 UTC

S-Pol

UWKA

Refr

acti

vit

y

Correlation=0.93

Correlation drop occurs between 358 m leg (0.96) and 673 m leg (0.74)

-100.70 -100.60 -100.50 -100.40250

260

270

280

290

3000 10 20 30

Distance (km)

Refractivity at 234830 UTC

UWKA center at 234753 UTCUWKA Zavg = 167 m AGL

Longitude

Refr

act

ivit

y

S-Pol

UWKA

Correlation=0.88

Summary

Radar Refractivity may be a proxy for water Radar Refractivity may be a proxy for water vapor during the warm season.vapor during the warm season.

Radar Refractivity shows excellent correlation Radar Refractivity shows excellent correlation with surface station and aircraft refractivity.with surface station and aircraft refractivity.

Radar Refractivity has a low bias vs fixed Radar Refractivity has a low bias vs fixed surface stationssurface stations

Vertical depth represented appears to be Vertical depth represented appears to be lower levels of the ABL (<~300 m?).lower levels of the ABL (<~300 m?).

Horizontal resolution is approximately 4 km Horizontal resolution is approximately 4 km (although it sometimes appears better).(although it sometimes appears better).

Ongoing Work Evaluate accuracy of low-level refractivity retrievalEvaluate accuracy of low-level refractivity retrieval

Fixed and mobile mesonetsFixed and mobile mesonets Plan to: Add GPS intercomparisonsPlan to: Add GPS intercomparisons Plan to: Add DRI MMR intercomparisonsPlan to: Add DRI MMR intercomparisons

Evaluate layer over which refractivity retrieval is Evaluate layer over which refractivity retrieval is representativerepresentative Aircraft in situ measurementsAircraft in situ measurements SRL intercomparisonsSRL intercomparisons AERI intercomparisonsAERI intercomparisons Plan to: Add Sounding & Dropsonde comparisonsPlan to: Add Sounding & Dropsonde comparisons Plan to: Add horizontal and vertical pointing airborne Plan to: Add horizontal and vertical pointing airborne

DIALDIAL Plan to: Add TAOS intercomparisonsPlan to: Add TAOS intercomparisons Possibly add: MIPS profiling radiometer Possibly add: MIPS profiling radiometer

intercomparisonsintercomparisons Plan to: Evaluate two more days in detailPlan to: Evaluate two more days in detail

Comments and Suggestions?

-100.70 -100.60 -100.50 -100.40250

260

270

280

290

3000 10 20 30

Distance (km)

Refractivity at 234830 UTC

UWKA center at 234753 UTCUWKA Zavg = 167 m AGL

Longitude

Refr

act

ivit

y

S-Pol

UWKA

Correlation=0.882 km 11 km

dryline

S-Pol Refractivity Retrieval

dryline

cool/moist

• Variations in q, T and p• Boundary detection• Advection• Pettet et al., next; Fabry and Park, 1700

warm/dry

Refractivity: One Day After Heavy Rainfall Aircraft in-situ data

Northern edge of aircraft track Ts=45 deg C,Theta60=307 K, q60 = 8.5 g/kg

Southern edge of aircraft track Ts=32 deg C,Theta60=306.2 K, q60 = 11 g/kg

warm/dry

cool/moist

cool/moist

warm/dry

1600 1800 2000 2200 0000Time (UTC)

240

260

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320

Refra

ctivity

S-Pol

Verle

0200 0400

Surface station comparisons

Correlation = 0.99

1600 1800 2000 2200 0000Time (UTC)

240

260

280

300

320

Refra

ctivity

0200 0400

S-Pol

Homestead

Correlation = 0.92

1600 1800 2000 2200Time (UTC)

240

260

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300

320

Refra

ctivity

0000 0200 0400

Playhouse

S-Pol

Correlation = 0.98

-100.68 -100.64 -100.60 -100.56Longitude

250

260

270

280

290

Refr

act

ivit

y2 4 6 8 10 12

Distance (km)

Refractivity at 220029 UTCMM6 center at 215751 UTC

0

Probe 6

S-Pol

Correlation = 0.14

Longitude

250

260

270

280

290

Refr

act

ivit

y0.5 1.0 1.5 2.0 2.5 3.0

Distance (km)

Refractivity at 221830 UTCMM1 center at 221905 UTC

-100.615 -100.605 -100.595 -100.585

Probe 1

S-Pol

Correlation = 0.68