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