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MOTIVATION FOR THIS STUDY CONCLUSIONS Air traffic at busy airports can be significantly disrupted because low visibility due to fog makes it unsafe to take off, land and taxi on the ground. In this poster we show how automa@c profiling Lidar ceilometer measurements (CL31/CL51) on most airports, can be used to provide prefog alert informa@on, and hence help airport weather forecasters to beJer predict those low visibility condi@ons. This research was carried out prior to a field campaign at Paris CDG airport (France). Ref: Haeffelin, M., Laffineur, Q., BravoAranda, J.A., Drouin, M.A., CasqueroVera, J.A., Dupont, J.C., and De Backer, H.: RadiaDon fog formaDon alerts using aGenuated backscaGer power from automaDc Lidars and ceilometers, Atmos. Meas. Tech. Discuss., doi:10.5194/amt2016182, in review, 2016. Mar@al Haeffelin (IPSL), Quen@n Laffineur (RMIB), JuanAntonio BravoAranda (IPSL), MarcAntoine Drouin (LMD), JuanAndrés CasqueroVera (LMD, UGR), JeanCharles Dupont (IPSL), Hugo De Backer (RMIB) Contact : [email protected]ffelin@ipsl.polytechnique.fr PHYSICAL PRINCIPLE PARAFOG: PreFOG alert tool based on ceilometer measurements Fog alert levels β aG (aJenuated backscaJer) profiles can be used to track progressive hygroscopic growth of fog condensa@on nuclei β aG vs VIS β aG vs RH METHODOLOGY Reference β aG profiles are found in dry (RH) condi@ons ! RH<75% β aG profiles show well mixed condi@ons and liJle aJenua@on ! RH>75% β aG profiles show aJenua@on due to scaJering by moist aerosols FOG ALERT LEVELS Temporal gradient of β aG /β Ref ra@o Al@tude of maximum gradient Alert levels defined based on ra@o gradient and β aG thresholds FOG ALERT OCCURRENCE FOG ALERT STATISTICS At what al@tude do alerts occur? What is the temporal dura@on of alerts? How are alert dura@ons affected by reference condi@ons? Prefog alert occurrences and dura@ons depend on the cooling processes leading to supersaturated condi@ons, and on the reference condi@ons that can be found. Acknowledgments : TOPROF COST ac@on; MétéoFrance; STCE. RelaDve humidity (RH), Visibility and β aG measured at 20 m agl Frequency of occurrence of each alert level (low, moderate, severe, and fog level alerts) for each al@tude agl and each @me before fog occurrence @me. For each height / Dme interval, the sum of occurrences of all alert levels = 100% (incl. no alert). REALTIME FOG ALERTS AT CDG AIRPORT CL31, RH and VIS measurements at CDG airport are analyzed in real@me (5 min) by PARAFOG

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MOTIVATION FOR THIS STUDY

CONCLUSIONS

Air traffic at busy airports can be significantly disrupted because low visibility due to fog makes it unsafe to take off, land and taxi on the ground. In this poster we show how automa@c profiling Lidar ceilometer measurements (CL31/CL51) on most airports, can be used to provide pre-‐fog alert informa@on, and hence help airport weather forecasters to beJer predict those low visibility condi@ons. This research was carried out prior to a field campaign at Paris CDG airport (France). Ref: Haeffelin, M., Laffineur, Q., Bravo-‐Aranda, J.-‐A., Drouin, M.-‐A., Casquero-‐Vera, J.-‐A., Dupont, J.-‐C., and De Backer, H.: RadiaDon fog formaDon alerts using aGenuated backscaGer power from automaDc Lidars and ceilometers, Atmos. Meas. Tech. Discuss., doi:10.5194/amt-‐2016-‐182, in review, 2016.

Mar@al Haeffelin (IPSL), Quen@n Laffineur (RMIB), Juan-‐Antonio Bravo-‐Aranda (IPSL), Marc-‐Antoine Drouin (LMD), Juan-‐Andrés Casquero-‐Vera (LMD, UGR), Jean-‐Charles Dupont (IPSL), Hugo De Backer (RMIB)

Contact : [email protected]@ipsl.polytechnique.fr

PHYSICAL PRINCIPLE

PARAFOG: Pre-‐FOG alert tool based on ceilometer measurements

Fog alert levels

βaG (aJenuated backscaJer) profiles can be used to track progressive hygroscopic growth of fog condensa@on nuclei

βaG vs VIS βaG vs RH

METHODOLOGY Reference βaG profiles are found in dry (RH) condi@ons !  RH<75% βaG profiles show

well mixed condi@ons and liJle aJenua@on

!  RH>75% βaG profiles show aJ enu a@on d u e t o s caJer i ng by mo i s t aerosols

FOG ALERT LEVELS Temporal gradient of βaG/βRef ra@o Al@tude of maximum gradient Alert levels defined b a s e d o n r a @ o grad ient and βaG thresholds

FOG ALERT OCCURRENCE

FOG ALERT STATISTICS

At what al@tude do alerts occur?

What is the temporal dura@on of alerts? How are alert dura@ons affected by reference condi@ons?

Pre-‐fog alert occurrences and dura@ons depend on the cooling processes leading to supersaturated condi@ons, and on the reference condi@ons that can be found.

Acknowledgments: TOPROF COST ac@on; Météo-‐France; STCE.

RelaDve humidity (RH), Visibility and βaG measured at 20 m agl

F r e q u e n c y o f o c cu r r en ce o f each alert level (low-‐, moderate-‐, severe-‐, and fog-‐level alerts) for each al@tude agl and each @me b e f o r e f o g occurrence @me. For each height / Dme interval, the sum of occurrences of all

alert levels = 100% (incl. no alert).

REALTIME FOG ALERTS AT CDG AIRPORT

CL31, RH and VIS measurements at CDG airport are a n a l y z e d i n real@me (5 min) by PARAFOG

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