Nowcasting Aircraft Icing Conditions Using GOES-Derived Cloud Products

Cory A. Wolff

Ben C. Bernstein

Frank McDonough

World Weather Research Program Symposium on Nowcasting and Very Short Range Forecasting

Toulouse, France

September 5-9, 2005

NASA Glenn Research Center

• Instrumented Twin Otter– FSSP, 2D Grey, King

LWC, Nevzorov

• Fly into known icing conditions– Test aircraft response– Document conditions

• NCAR provides short term forecasts & nowcasts

Standard Tools

• NWP Model• Geostationary Satellite

(GOES)– CTT and albedo

• Radar• Surface Observations

– Precipitation type– Cloud base and

coverage

• Pilot Reports

• Effective Radius– Estimate of

drop size– Usually “large”

or “small”

New Tools• Developed at NASA Langley Research Center• GOES Derived Cloud Products (GDCP)

• Phase– Clear– Ice– Liquid (T < 0°C)– Liquid (T > 0°C)

• Liquid Water Path (LWP)– Estimate liquid

water content (LWC) at cloud top

– Trends in LWC often follow LWP

16 February 2005

• Icing encounter near Cleveland, OH

• GDCP useful in nowcasting

1200 UTC Briefing• Snow in region• Upper layer

pulling away at DTX

• Left with warm topped SLW cloud– PIREPs

around DTX

• Flight postponed

• No GDCP yet

Mid-level Drying

CTT: -8 °C

1315 UTC

1415

UTC

1445

UTC

1515

UTC

CLE

First Encounter• Decision to fly made at 1400 UTC

– First daytime GDCP at 1415 UTC– Not available until ~1445 UTC

• Between CLE and SKY (1509 – 1542 UTC)

SKY

CAK

CLE

40.5

41.0

41.5

42.0

-83.0 -82.5 -82.0 -81.5 -81.0

Longitude

La

titu

de

1542 UTC

1509 UTC

Lake Erie

1524 UTC

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

15:10:00 15:20:00 15:30:00 15:40:00

UTC Time

Kin

g L

WC

(g

/m3 )

1524 UTC

1515

UTC

1545

UTC

1615

UTC

CLE

Second Encounter• LWP maximum and brighter clouds had moved

east during performance tests• Between CLE and CAK (1553 – 1629 UTC)

SKY

CAK

CLE

40.5

41.0

41.5

42.0

-83.0 -82.5 -82.0 -81.5 -81.0

Longitude

Lat

itu

de

1629 UTC

1553 UTC

Lake Erie

1609 UTC

1617 UTC

0.0

0.1

0.2

0.3

0.4

0.5

15:52:00 16:02:00 16:12:00 16:22:00

UTC Time

Kin

g L

WC

(g

/m3 )

1609 UTC 1617 UTC

Summary

• Standard encounters– Cloud top had highest LWC

• GDCP were helpful– Extra confidence– Higher LWC found near LWP max

• Effective Radius– GDCP suggested small drops – Aircraft measured MVD: 10 – 18 µm