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ADDS - Icing Help Page (2 of 4)
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Current Icing Product

Introduction:

The Current Icing Product (CIP) is a supplementary (for increased situational awareness) weather product that provides a graphical view of the current icing environment. Input from weather sensors is provided to software models to produce this automatically generated graphical weather product. The CIP is updated hourly, and provides current information via icing severity graphics and icing probability graphics. It is important to note that all CIP products are not forecasts, but presentations of current conditions at the time of the analysis ("Nowcast" information). CIP is not to be used as a forecast for icing conditions.

NOTE: Pilots of aircraft that are not certified for flight into known or forecast icing conditions should be especially cautious of areas displaying any type of icing severity, regardless of the probability indicated on CIP graphics.

Selecting CIP Graphics:

To retrieve a CIP graphic on the ADDS icing page, select the specific graphic from the left-side pull-down menu. The requested graphic should appear as an image embedded directly in the icing page. The right-side pull-down menu allows you to select a specific altitude, with a graphic every 2000 feet, starting at 1000 feet and ascending to FL290. Besides the individual altitudes, you can select a composite, maximum value of all altitudes, labeled "max." This image provides a quick overview of the regional icing threat. The Flight Path Tool allows access to CIP icing probability data for different altitudes in 1000 foot increments, as well as vertical cross sections for a specific route and a closer look at specific geographic areas.

Overview of CIP Display:

All graphics display icing severity in five categories consistent with other weather reports: none, trace, light, moderate, and heavy. Users should always keep in mind that the five levels of icing severity depicted on the CIP graphic are general terms that are not specific to a type of aircraft, flight condition (e.g., speed, angle of attack, vertical speed, etc.), and are only intended to depict general icing conditions for supplementing flight planning and situational awareness. Essentially, light icing to one aircraft in one situation might not necessarily be light icing to a different aircraft in another situation.

On icing severity graphics (sample shown in Fig. 2), the scale is from trace (very light blue) to heavy (dark blue). On the icing probability graphics (sample shown in Fig. 1), the scale is from 0 to 85%, using cool to warm colors with warmer colors indicating higher icing likelihood. Probabilities range from 0% (no icing expected) to 85% (near certain icing). Probabilities do not reach 100% because the data available do not allow for a diagnosis with absolute certainty.

Users can also "filter" or "mask" icing graphics by selecting icing probabilities that are less than 25% or less than 50% (sample shown in Fig. 3). Either selection uses a gray color to show areas where the icing probability is less than the icing probability selected.

Supercooled Large Droplet (SLD) Icing:

SLD icing conditions are characterized by the presence of relatively large, super cooled water droplets indicative of freezing drizzle and freezing rain aloft. These conditions, which are outside the icing certification envelopes (FAR Part 25 Appendix C), can be particularly hazardous to aircraft. SLD icing threats are indicated on all Icing Severity graphics by a red hatched region (sample shown in Fig. 4). PIREPS:

Pilot reports (PIREPs) of icing that occur within 1000 feet of the selected altitude are overlaid on the single-level graphics (legend found at the bottom of each graphic). On the composite graphic, PIREPs for all altitudes are shown (except negative icing reports, which are omitted for the sake of clarity).
Fig.1: Icing probability
Fig.1: Icing probability
Fig.2: Icing severity
Fig.2: Icing severity
Fig.3: Masked icing severity
Fig.3: Masked icing severity
Fig.4: Severity with SLD overlay
Fig.4: Severity with SLD overlay
Additional Information:

Those interested to learn more details of the science used to create CIP are invited to read the following paper:
Bernstein, B.C., F. McDonough, M.K. Politovich, B.G. Brown, T.P. Ratvasky, D.R. Miller, C.A. Wolff and G. Cunning, 2005: Current Icing Potential (CIP): Algorithm description and comparison with aircraft observations. J. Appl. Meteor., 44, 969-986.
 

Example event: 16 Feb 2005

On 16 Feb 2005, a cold front moved through the Great Lakes region and into the Appalachians leaving widespread icing conditions in its wake. As part of the development work behind the CIP product, researchers from NASA and NCAR purposefully fly into known icing conditions. This event was chosen because a team of researchers flew into the clouds and icing conditions in the area around Cleveland, Ohio on this day. They encountered primarily small supercooled water drops between 5500 and 6000 feet MSL that produced periods of moderate icing. Photos of this icing encounter are shown at right. Note the build-up of ice on the leading edge of the wing of the NASA Glenn Research Center Twin Otter.

A series of graphics created from CIP data at 1500 UTC are shown above. The small graphics here display the region around Cleveland whereas clicking on the figure produces the graphic for the entire CIP domain. Note the yellow and orange hues on Fig. 1 denoting the highest probability for icing south and east of Cleveland. Likewise, note the region of moderate icing severity in Fig. 2 but lower probability and decreased severity to the north and west (over Lake Erie). When the Twin Otter briefly flew northwest of Cleveland, the crew confirmed the sharp decrease in icing severity combined with significantly less liquid water content but roughly constant temperature and droplet sizes. The SLD product at the same altitude (not shown) did not depict any large drops in the region around Cleveland and none was found by the research aircraft. A SLD plot from 9000 feet seen in Fig. 3 shows SLD diagnosed well to the south and east of Cleveland, but the research aircraft did not fly in those areas so it was not confirmed.

Fig.5: Icing accumulates while in cloud. Photo credit: NASA Glenn Research Center
Fig.5: Icing accumulates while in cloud. Photo credit: NASA Glenn Research Center
Fig.6: After ascending above cloud. Photo credit: NASA Glenn Research Center Fig.6: After ascending above cloud. Photo credit: NASA Glenn Research Center

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