Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an...

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Aircraft Icing Aircraft Icing

Transcript of Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an...

Page 1: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft Icing

Page 2: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft Icing

Aircraft icing is the accretion of supercooled liquid water (SLW) on the airframe. The accumulation of ice on the aircraft can increase drag and reduce the airfoil lift of the wing resulting in requirements for additional power to stay aloft

Page 3: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft IcingThis SLW can be in the form of cloud droplets or This SLW can be in the form of cloud droplets or freezing rain/drizzle. Types of icing encountered freezing rain/drizzle. Types of icing encountered are: are:

Rime Rough, milky, opaque ice formed by instantaneous freezing ofsmall supercooled water droplets.

Clear A glossy, clear or translucent ice formed by the relatively slowfreezing of large supercooled water droplets.

Mixed Mixture of rime and clear ice.

Page 4: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft IcingIcing can adversely affect the flight characteristics of an aircraft. The severity of icing experienced by an aircraft is classified below

Light

The rate of accumulation may create a problem if flight isprolonged in this environment (over one hour). Occasionaluse of deicing/anti-icing equipment removes/preventsaccumulation. It does not present a problem if thedeicing/anti-icing equipment is used.

ModerateThe rate of accumulation is such that even short encountersbecome potentially hazardous and use of deicing/anti-icingequipment or diversion is necessary.

SevereThe rate of accumulation is such that deicing/anti-icingequipment fails to reduce or control the hazard. Immediatediversion is necessary.

Page 5: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft IcingThe severity of icing depends upon The severity of icing depends upon supercooled liquid water content (SLWC), supercooled liquid water content (SLWC), temperature and droplet size. temperature and droplet size. While aircraft icing occur between 0°C and -20°C, studies found the optimum temperature for aircraft icing is -4°C to -7°C. Drizzle-size cloud droplets (> 50 micro m) and weak vertical motion are other factors favourable for aircraft icing.

Page 6: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft IcingIcing is very variable in both space and time in any cloud system, and any forecast must necessarily be of probabilistic.

Type of cloud Probabilityof icing

Intensity Water content(g/m3)

Cu Cb Ns High May be severe 0.2 - 4.0Sc AcAc with As

50% Rarely more thanmoderate

0.1 - 0.5

As Low Moderate or light 0.1 - 0.3St Low Light 0.1 - 0.5

Page 7: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft Icing

Note: In supercooled Sc relatively large liquid water contents may persist over many tens of miles near the upper boundary of the cloud layer. Moderate or severe icing can occur in these circumstances if an aircraft remains at this particular height.

Page 8: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft Icing

Cloud base temperature and the heights above cloud base have an important effect on the risk and severity of ice accretion in convective cloud

Page 9: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Icing Situations

Situation Associated clouds Temperatures Icing

Frontal surface (in winter) Area near the freezing point line severe

Icing rain Especially with As, Ns Less than 0°C severe

Warm sector of unsettled nature Unsettled or convective clouds (Cu, Cb, Ac flo) Between 0 and -15°C severe to moderate

Unsettled sky Convective clouds Cu, Cb Between 0 and -15°C severe to moderate

Varying nature Ascend clouds along relief Between 0 and -15°C severe to moderate

Varying nature St or icing fog with undercooled water content Between 0 and -10°C severe to moderate

Stable atmosphere (Lee waves) Stable lenticular Ac Between 0 and -10°C moderate

Warm sector with stable natureStratiform clouds St, Sc (possibly, As, Ns; Ac overflowing)

Between freezing point and minus 10°C (if Ac, between 0 and -15°C)

moderate to light

Anticyclonic system Clear sky Less than 0°C light

Anticyclonic system Icing fog Less than 0°C light

Anticyclonic system Sky clear but layers with different temperature and moisture

Less than 0°C light

Page 10: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft IcingIcing in Frontal System

A typical mid-latitude frontal system involves the interaction of several air masses, creating sectors where certain characteristics predominate. These include the warm sector, the overrunning sector, and the cold advection sector

Page 11: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft Icing

Page 12: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft Icing

Identification of Icing from Upper-air Observations

Analysis of upper-air data is a key initial step in the icing assessment processIcing associated with fronts and depressions is very variable and each case should be treated on its merits.

Page 13: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft IcingIdentification of Icing from Upper-air ObservationsDiagnosis of icing from upper-air charts (suggested by UCAR)

(1) Analyze individual levelsAnalyze individual levels:Beginning with the highest level chart and working downward, do a quick hand or computerized analysis of each chartAssess the cloud phase in each layer and begin thinking about the icing situation. In cloudy areas (dewpoint depression is ≤

5°C):

Page 14: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft IcingIdentification of Icing from Upper-air ObservationsDiagnosis of icing from upper-air charts (suggested by UCAR)

(2) Compare between levels:Compare between levels:–Compare the adjacent-level analyses side-by-side and look

for vertical continuities and discontinuities of features from one layer to the next.

–Assess the approximate freezing (0°C) levels and whether there are multiple freezing layers. Multiple freezing layers can indicate the presence of inversions and melting layers, which are frequent contributors to icing conditions

Page 15: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft IcingIdentification of Icing from Upper-air Observations

Quick hand analysis of 250 hPa chart

Page 16: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft IcingIdentification of Icing from Upper-air Observations

Quick hand analysis of 500 hPa chart

Page 17: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft IcingIdentification of Icing from Upper-air Observations

Quick hand analysis of 700 hPa chart

Page 18: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft IcingIdentification of Icing from Upper-air Observations

Quick hand analysis of 850 hPa chart

Page 19: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft IcingThe specific features to examine in each level is also suggested by UCAR

Page 20: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft IcingThe specific features to examine in each level is also suggested by UCAR

Page 21: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft IcingThe specific features to examine in each level is also suggested by UCAR

Page 22: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft IcingThe specific features to examine in each level is also suggested by UCAR

Page 23: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft IcingIdentification of Icing from Upper-air Observations

Page 24: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft IcingComparing charts at different level show dry air behind trough at 500 hPa have near saturation at lower level. These saturated conditions at 700 hPa, together with temperature around 0°C and -15°C suggested that there is a potential for icing near the cloud top.Another possible area is found behind the area of cold advection at 850/700 hPa. While it is dry at 850 hPa, it is near saturation at 700 hPa. Icing is also probable near cloud top.

Page 25: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Night Icing Detection Night Icing Detection -- using using satellite derived product satellite derived product

Ellrod & Nelson (Ellrod & Nelson (Remote Sensing of Remote Sensing of Aircraft Icing Regions Using GOES Aircraft Icing Regions Using GOES Multispectral Imager DataMultispectral Imager Data), suggested that ), suggested that multiple IR channels of satellite imagery multiple IR channels of satellite imagery were useful in detecting icing. were useful in detecting icing.

Page 26: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

The occurrence of icing requires:The occurrence of icing requires:

the presence of Supercooled Liquid Water the presence of Supercooled Liquid Water (SLW) in clouds. SLW clouds appear (SLW) in clouds. SLW clouds appear cooler in shortwave IR. Typically, cooler in shortwave IR. Typically, temperature in longwave IR temperature in longwave IR –– temperature temperature in shortwave IR > 2in shortwave IR > 2��is an indication of is an indication of SLWSLWtemperatures in the 0 to temperatures in the 0 to ––1717��rangerange

Page 27: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Color Criteria Interpretation

temperature in longwave IR < -40� even lower temperature than condition (b)

-40�=< temperature in longwave IR =< - 17� lower temperature than condition (b)

-17� < temperature in longwave IR < 0�and temperature in longwave IR – temperature in shortwave IR > 2�

condition (a) and (b) satisfied => icing is possible

-17� < temperature in longwave IR < 0�andtemperature in longwave IR – temperature in shortwave IR =< 2�

condition (b) only

0�=< temperature in longwave IR =< 10� higher temperature than condition (b)

temperature in longwave IR > 10� even higher temperature than condition (b)

Page 28: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Limitation

can only be applied during nighttimecan only be applied during nighttimeSLW clouds may not appear cooler in SLW clouds may not appear cooler in shortwave IRshortwave IRavoid using data over the area covered by avoid using data over the area covered by solar radiationsolar radiation

Page 29: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Upper images: Visible, showing brighter reflected solar radiation in the eastern part during sunrise. Lower images: Night icing detection, no icing (blue in color) can be depicted over region to the east of the red line due to presence of reflected solar radiation.

20050315 1925UTC 20050315 2025UTC 20050315 2125UTC 20050315 2213UTC 20050315 2249UTC

Page 30: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

LimitationLimitation

effective for effective for stratiformstratiform clouds that do not clouds that do not have higher level cloud cover have higher level cloud cover playing a sequence of imagery might help playing a sequence of imagery might help to depict underlying icing areato depict underlying icing areaIn deep convective, SLW could be In deep convective, SLW could be brought by brought by updraughtsupdraughts to great heightsto great heights

Page 31: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft IcingA cloud scheme was developed that explicitly represents the physical processes that transfer water from one phase to another.

–Condensation, the transition from water vapor to liquid water, increases the liquid water available for icing.

Page 32: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft Icing

–Evaporation, the transition from liquid to vapor, lowers the amount of liquid available for icing.

–Riming, the transition from liquid water to ice, reduces the amount of liquid water in the cloud as ice crystals nucleate within the cloud.

Page 33: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft Icing

–Melting, the transition from ice to liquid water, acts to provide liquid water for icing. Also, melting removes ice from airframes at flight levels having temperatures warmer than 0° C

–Deposition, the transition from water vapor to ice, is the mechanism by which ice crystals grow within a cloud, frost forms on airframes, and carburetor icing develops within engines.

Page 34: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft Icing

–Sublimation, the transition from ice to water vapor, can remove ice from airframes in mid flight if the aircraft is flown into a cloud-free area with temperatures colder than 0° C.

Page 35: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft Icing

–Physical processes that transfer water from one phase to another

Page 36: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft IcingCurrent Icing Potential (CIP)

The Current Icing Potential (CIP) product has been implemented in US Aviation Weather Center (AWC) to identify area of icing potential.

The CIP refines the model temperature and relative humidity fields by using satellite images, surface observations and pilotreports of icing to delineate areas of potential icing conditions.

The CIP is presented as an icing potential by using fuzzy logic to weight the various indicators of icing existence.

Page 37: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft IcingCurrent Icing Potential (CIP)

Page 38: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft IcingExperimental Future Icing Potential (FIP) have also been developed at AWS

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Thank YouThank You

Page 40: Aircraft Icing - World Meteorological · PDF fileAircraft Icing Aircraft icing is ... of an aircraft. ... Quick hand analysis of 250 hPa chart. Aircraft Icing. Identification of Icing

Aircraft IcingAircraft IcingThe new combined product, Icing Enhanced Cloud-top Altitude Product (ICECAP) shows potential icing regions color-coded with cloud top heights over the Continental United States (CONUS) at a resolution of 4 km.