Atmospheric Sounding by TAMDAR Over Keflavík Airport, Iceland – Comparison with Traditional Atmospheric Sounding Methods
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Atmospheric Sounding by TAMDAR over Keflavík Airport, Iceland – Comparison with Traditional Atmospheric Sounding Methods Arnór Tumi Jóhannsson Skýrsla VÍ 2017-002 Atmospheric Sounding by TAMDAR over Keflavík Airport, Iceland – Comparison with Traditional Atmospheric Sounding Methods Arnór Tumi Jóhannsson, Veðurstofa Íslands Skýrsla Veðurstofa Íslands +354 522 60 00 VÍ 2017-002 Bústaðavegur 7–9 [email protected] ISSN 1670-8261 150 Reykjavík 4 Abstract Tropospheric measurements by radiosonde and Tropospheric Airborne Meteorological Data Re- porting (TAMDAR) over Keflavík a irport, I celand, w ere c ompared i n a n e ffort t o a ssess the potential benefit o f i mplementing T AMDAR d ata i n t he o bservations a nd f orecasting system of the Icelandic Meteorological Office ( IMO). D espite a r elatively s mall d ataset a nd consid- erable spatial variability in the data, it was concluded that TAMDAR performs well in mea- suring temperature. Temperature measurements of radiosonde and TAMDAR were generally in good agreement. Furthermore, the results suggest that TAMDAR does well at assessing wind direction. TAMDAR detects variations in relative humidity and is generally in accordance with relative humidity forecasts. The quality of TAMDAR wind speed measurements is difficult to determine, however discrepancies between wind speed measured by radiosonde and TAMDAR can usually be explained to some degree by forecast or observed spatial variability in wind. It is concluded that implementing TAMDAR data into the observations and forecasting system of the IMO would nicely supplement traditional atmospheric soundings to increase the coverage and frequency of atmospheric measurements in Icelandic airspace. Útdráttur Háloftamælingar með veðurkanna (e. radiosonde) voru bornar saman við háloftamælingar fram- kvæmdar af TAMDAR yfir Keflavíkurflugvelli. Tilgangur verkefnisins var að meta mögulegan ávinning þess að innleiða TAMDAR-gögn í athugunar- og spákerfi V eðurstofu Í slands. Þrátt fyrir fremur lítið gagnasafn og mikinn breytileika í rúmi var ályktað sem svo, að hitamælingar TAMDAR væru áreiðanlegar og í góðu samræmi við hitamælingar veðurkanna. Niðurstöður verkefnisins benda til þess að vindáttarmælingar TAMDAR séu almennt góðar. TAMDAR nemur breytingar í loftraka og eru loftrakamælingar í samræmi við spár að allnokkru leyti. Gæði vind- hraðamælinga TAMDAR eru torræð, en yfirleitt má skýra ósamræmi milli vindhraðamælinga veðurkanna og TAMDAR með þeim breytileika sem fram kemur í spám eða athugunum. Inn- leiðing TAMDAR-gagna yrði líkast til ágætisviðbót við þau gögn sem löngum hafa legið til grundvallar háloftaathugunum á Íslandi; slík viðbót yki víðfeðmi og tíðni háloftamælinga yfir Íslandi. Contents List of Figures .................................................................................................. vi List of Tables.................................................................................................... viii List of Acronyms .............................................................................................. ix 1 Introduction................................................................................................ 1 2 The structure of the atmosphere..................................................................... 2 3 Atmospheric dynamics.................................................................................. 5 3.1 Atmospheric forces and the movement of air................................................ 5 3.2 Mid-latitude weather fronts and the Norwegian Cyclone Model ....................... 6 4 Aviation meteorology .................................................................................... 9 5 Atmospheric profiling................................................................................... 10 5.1 Radiosondes ......................................................................................... 12 5.2 TAMDAR ............................................................................................ 14 6 Data ........................................................................................................... 17 7 Results and discussion .................................................................................. 19 7.1 Case 1 - 27 September 2016 ..................................................................... 20 The weather situation.............................................................................. 20 The measurements ................................................................................. 20 7.2 Case 2 - 29 September 2016 ..................................................................... 25 The weather situation.............................................................................. 25 The measurements ................................................................................. 26 7.3 Case 3 - 1 October 2016 .......................................................................... 32 The weather situation.............................................................................. 32 The measurements ................................................................................. 34 7.4 Case 4 - 2 October 2016 .......................................................................... 40 The weather situation.............................................................................. 40 The measurements ................................................................................. 40 7.5 Case 5 - 27 October 2016......................................................................... 47 The weather situation.............................................................................. 47 The measurements ................................................................................. 48 7.6 Spatial and temporal variations in the data ................................................... 54 8 Conclusions................................................................................................. 57 9 References .................................................................................................. 59 Conflict of Interests Declaration.......................................................................... 61 v List of Figures 1 The atmospheric layers and temperature profile ............................................ 4 2 Atmospheric airflow around lows and highs ................................................. 6 3 Formation and structure of a typical mid-latitude cyclone ............................... 8 4 An example of a METAR weather report..................................................... 9 5 An overview of various atmospheric profiling methods................................... 10 6 A radiosonde launch in action................................................................... 12 7 Different configurations of a modern radiosonde........................................... 13 8 A schematic overview of the TAMDAR sensor ............................................. 15 9 A TAMDAR sensor mounted on a jet aircraft ............................................... 16 10 The airspace of interest and colour representation of TAMDAR carrying aircraft . 18 11 Synoptic charts for Iceland on 27 September................................................ 20 12 Tracks of radiosonde and TAMDAR on 27 September ................................... 21 13 Temperature profiles of radiosonde and TAMDAR on 27 September ................. 22 14 Wind profiles of radiosonde and TAMDAR on 27 September .......................... 23 15 Relative humidity profiles of radiosonde and TAMDAR on 27 September .......... 24 16 Synoptic charts for Iceland on 29 September................................................ 25 17 Winds aloft observed over Iceland on 29 September ...................................... 26 18 Tracks of radiosonde and TAMDAR on 29 September ................................... 27 19 Temperature profiles of radiosonde and TAMDAR on 29 September ................. 28 20 Wind profiles of radiosonde and TAMDAR on 29 September .......................... 29 21 Relative humidity profiles of radiosonde and TAMDAR on 29 September .......... 30 22 Forecast relative humidity over Iceland on 29 September ................................ 31 23 Synoptic charts for Iceland on 1 October..................................................... 32 24 Synoptic chart from the UK Met Office showing fronts over the North Atlantic on 1 October......................................................................................... 33 25 Winds aloft observed over Iceland on 1 October ........................................... 33 26 Tracks of radiosonde and TAMDAR on 1 October......................................... 35 27 Temperature profiles of radiosonde and TAMDAR on 1 October ...................... 36 28 Wind profiles of radiosonde and TAMDAR on 1 October................................ 37 29 Relative humidity profiles of radiosonde and TAMDAR on 1 October ............... 38 30 Forecast relative humidity over Iceland on 1 October ..................................... 39 31 Synoptic charts for Iceland on 2 October..................................................... 40 32 Winds aloft forecast over Iceland on 2 October............................................. 41 33 Tracks of radiosonde and TAMDAR on 2 October......................................... 42 34 Temperature profiles of radiosonde and TAMDAR on 2 October ...................... 43 35 Wind profiles of radiosonde and TAMDAR on 2 October................................ 44 36 Relative humidity