Rovaniemi airport EFRO

Visibility <1000m ( synoptical obs.)1970-2000

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EFRO

EFHK

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Photo: Sippo Nevalainen

Rovaniemi is situated in North Finland(They say, that Santa lives next to us…)

EFRO Arctic Circle latitude 66,3

Runway 3kmx60m21: heading direction 210 03: heading direction 030

Altitude differences:

03 : 633ft21 : 609ftmidpoint: 642ft !Altitude fromEFKE:n 600ft

@ The Comet program

In Finnish sky :During wintertime no convective clouds (cumulus, cumulonimbus),

but stratiform clouds…

Stratus can be very local http://komfortabc.hu/ido/felhoatlasz/site3b.php

Stratus has a very low cloudbasehttp://propogodu.ru/2/20/

http://mmem.spschools.org/grade5science/weather/stratocumulus.html

Stratocumulus

Photo: Tapani Kuoksa

EFRO in wintertime

Rime and frost are typical for cold and humid climate

http://fi.wikipedia.org/wiki/Huurre

http://fi.wikipedia.org/wiki/Tykky

http://fi.wikipedia.org/wiki/Kuura

AGA 3-10 includes national regulations for runway friction

Measured or calculated coefficient Estimated braking action Code

0.40 and above Good 50.39 to 0.36 Medium to good 40.35 to 0.30 Medium 30.29 to 0.26 Medium to poor 20.25 and below Poor 1Unreliable Unreliable 9

2.3.3 Each airport maintenance shift shall have a nominated person responsible for ensuring that runway inspections and friction measurements are carried out and their results reported appropriately. The airport manager or a person designated by him shall select and list those members of airport staff who are qualified to perform friction measurements and runway inspections, and friction assessments where necessary.

2.3.5 The verbal assessment corresponds to the measured friction

Friction is reported for every third of runway lenght

How to improve friction?

• 3.2.3 Apart from urea, only such chemicals shall be used for friction improvement that have been determined to meet the current applicable SAE Aerospace MaterialSpecification or any equivalent European standard.

• 3.2.4 If sand is used, grain size must be such that all particles pass a 4 mm sieve. If any oversized particles, stones, solid pieces or foreign objects are found in the material, that load of sand shall not be spread over areas used by turbojet aircraft unless it is sieved again.

• 3.2.5 When sand is no longer needed, it shall be removed from the pavement

AGA M3-10

Monitoring and measuring friction

• 2.1.5 For monitoring the changing runway conditions, every airport shall have a surface temperature meter or ice warning system with sensor(s) permanently installed on runway surface and a display located in the airport maintenance duty room.

AGA M3-10

Airport runway maintenance uses Vaisala Rosa DM32 program

-some theoretical examples when slippery conditions appear – or not

-real examples by Rovaniemi airport collected by Tapani Kuoksa

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Radiative cooling during a cloudless calm night

18 24 03 06

Ilman lämpötila

Kastepiste

Pintalämpötila

Air temperature

Dew point

Surface

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Warming after a lond cold period

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Air temperature

Dewpoint

Surface

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0oC

-8C 1km 2km 3km

Influence of topography Air temperatureDew pointSurface

3.7.2008Air temperature

Dew point

Surface

Relative humidity

CloudinessRainfallWarningAlarm

In July afternoon. Runway temperature can reach +42 oC

1.10.2007

An autumn day: During early morning air temperature sinks near zero, surface tempeperature below zero and is colder than dewpoint. On the runway there developes hoar frost and a warning is on. After sunrise temperature rises , the most rapid rise takes place in runway temperature, and runways is getting dry.

21.10.2007

In the morning on 20.10. there is hoar frost on the runway. When surface temperature rises higher than dewpoint temperature, hoar frost will evaporate. After 16:00 o’clock all temperatures drop below zero, warning is on. Sweepers keep friction moderate.

8.12.2007

Air temperature goes at 2 o’clock below zero. Runway is wet, chemicals added on the surface and freezing point dropped toward -4oC. Action helped, no warning.

10.12.2007

Earlier event continues….. Chemical added again at 13:10 . Purple curve shows how freezing point decreases ( -10 oC), runway surface becomes wet and salty.

15.12.2007

When surface temperature is several degrees below dew point temperature, it causes heavy formation of hoar frost. Sometimes display shows runway surface state ”snowy”, even there has not been snowfal. .Instrumental false alarm!

16.12.2007

Event continues… mild weather, chemicals added at 13.10.Decrease of freezing point stops hoar frost formation, state of runway is ”wet”.

15.1.2008

Friction measured at 17:00 and 21:00 0,30. After 01:10 surface temperature remains below dew point temperature, when temperature is rising. A rapid sweeper drive at 05:00, result is better friction 0.45

23.1.2008

In the morning hoar frost warning. Rapid sweeper drive keeps friction good ( at 13.00 26,40,43) and at 20.26 (44,55,57) During night runway temperature drpops below dewpoint temperature and frost formation gets stronger, friction at 05.18 o’clock 34,34,45)

12.4.2005

Example of too late chemical spreading. Friction at 21:00 good ” 5 ”, runway wet. Right time should have been at 01:00. Luckily this time chemical had enough effect and friction was. 0.40.