Vertical stratification of submicrometer aerosol particles measured during the high-Arctic ASCOS expedition 2008

Caroline Leck, Joseph Sedlar, Erik Swietlicki, Staffan Sjögren, Barbara Brooks, Sarah Norris

The atmospheric thermodynamic structure and aerosol particle concentrations, in several size ranges, across a multitude of surface conditions over the Arctic Ocean pack ice, was profiled using a helicopter based onboard Swedish icebreaker Oden during the Arctic Summer Cloud Ocean Study (ASCOS) expedition in summer 2008.

Aerosol sources are known to be few in summer high Arctic while the cloud cover is generally at a maximum during this season. Until now, a large deficiency has been an inability to relate Arctic aerosol and cloud properties because of the difficulties in performing in situ measurements within the harsh Arctic environment.

The ultrafine particle (diameters between 3⁠ – ⁠15 nm) concentrations were typically a few hundred per cm³, but reached as high as 1500 cm⁻³ and were often found within the shallow Arctic boundary layer, while occasional elevated concentrations were measured at higher altitudes. The accumulation mode particle concentrations were generally less than 1 cm⁻³ within the well-mixed boundary layer. Such low levels can be explained by the presence of a moist boundary layer combined with in general weak local sources. In addition, largest accumulation mode numbers were found at and above former cloud tops.

Citation

Caroline Leck, Joseph Sedlar, Erik Swietlicki, Staffan Sjögren, Barbara Brooks, Sarah Norris (2022) Vertical stratification of submicrometer aerosol particles measured during the high-Arctic ASCOS expedition 2008. Dataset version 1. Bolin Centre Database. https://doi.org/10.17043/oden-ascos-2008-aerosol-stratification-1

References

Kupiszewski P, Leck C, Tjernström M, Sjogren S, Sedlar J, Graus M, Müller M, Brooks B, Swietlicki E, Norris S, Hansel A (2013) Vertical profiling of aerosol particles and tracer gases over the central Arctic Ocean during summer. Atm Chem Phys 13: 12405⁠ – ⁠12431. https://doi.org/10.5194/acp-13-12405-2013

Data description

The Quality Controlled data are provided in one xls spreadsheet file and one matlab mat file. Additional material in the form of photographs taken from the helicopter and image files with graphs that illustrate the data is also provided along with a readme file in pdf format. The dataset contains the following items:

• ASCOS08_QCdata_072011.xls: Data from the helicopter flights. See below for details.
• ASCOS08_QCdata_072011_heli.mat: Data from the helicopter flights. See below for details.
• ASCOS08_Flight_Schedule_QC_072011.xls: Flight schedule for the Quality Controlled data files.
• ASCOS_QC_Heli_graphs.zip: Graphical representations (png files) of the data in ASCOS08_QCdata_072011.xls.
• ASCOS_PhotosHeliFlights.zip: Photographs (jpg files) on ambient sampling conditions during the helicopter flight when available.
• ASCOS_Heli_readme.pdf: Provides details on the aerosol and meteorological instrumentation and measurements.

The files ASCOS08_QCdata_072011.xls and ASCOS08_QCdata_072011_heli.mat contain data from the helicopter flights during the period 10 Aug⁠ – ⁠7 Sept 2008. All data is given with 1 second time resolution. Columns labeled “mean” or “med” represent 11 seconds running mean/med values. Height was calculated using observed pressure and temperature. Data time is given in MatLab datenum format. Data entries labeled -99999 indicate missing data. The data are provided in two file formats, to enable use in either excel or matlab.

The files include the following data columns:

1. time (YY-MM-DD Hour:Min:Sec).
2. lat (°): latitude
3. lon (°): longitude
4. w_e (0=west 1=east)
5. z (m): height
6. P_ptu (hPa): Pressure
7. P_ptu mean (hPa): Pressure
8. P_ptu med (hPa): Pressure
9. T_tc (Celsius): Temperature
10. T_tc mean (Celsius): Temperature
11. T_tc med (Celsius): Temperature
12. RH_ptu (%): Relative humidity
13. RH_ptu mean (%): Relative humidity
14. RH_ptu med (%): Relative humidity
15. WVmr_calc (gkg-1) : Water Vapor mixing ratio
16. WVmr_calc mean (gkg-1) : Water Vapor mixing ratio
17. WVmr_calc med (gkg-1) : Water Vapor mixing ratio
18. ucpc (particles by number per cm3, Diameters > 3nm)
19. ucpc_mean (particles by number per cm3, Diameters > 3nm)
20. ucpc_med (particles by number per cm3, Diameters > 3nm)
21. cpc (particles by number per cm3, Diameters > 14nm)
22. cpc_mean (particles by number per cm3, Diameters > 14nm)
23. cpc_med (particles by number per cm3, Diameters > 14nm)
24. clasp (particles by number per cm3, Diameters > 300nm)
25. clasp_mean (particles by number per cm3, Diameters > 300nm)
26. clasp_med (particles by number per cm3, Diameters > 300nm)

Comments

Details of the measurements

For vertical and horizontal profiling of aerosol, trace gases and meteorological parameters, 70 flights, and about 40 hours of helicopter time, were performed. The aerosol particle size concentrations were measured at 1 Hz in several size ranges using two Condensation Particle Counters ((Ultrafine)UCPC diameters >3nm and CPC diameters >14nm) and an Optical Particle Spectrometer (CLASP): diameters >300nm). The meteorological mapping was performed (logged at 2-3 Hz) with Thermoelements and a T, P and RH sensor PTU300 (Vaisala, Finland). More details concerning the instrumental set up is given below. The helicopter was very successfully deployed but its inability to penetrate cloud meant restricted measurements to clear sky episodes. The ideal solution would have been to use an all-weather (de-iced) helicopter, which was unfortunately not possible.

The helicopter was flown perpendicular to the wind direction to the ship, and turned slightly upwind before the return flight. This method was chosen in order to ensure unpolluted air to be sampled, as well as not to disturb the measurements onboard the ship. The air was sampled through an inlet isokinetically at helicopter air speed of 70 km/h, which the pilot maintained manually.

Flights are labeled according to date [MMDD] and flight number [nr] for each day. Certain flight numbers for a particular day are not included for use, indicating that these flight data were either: 1) not quality-controlled because the flight was a reconnaissance rather than research flight; 2) instruments were not operational.

A data logging system was implemented within the cabin of the helicopter for aerosol and meteorological profiling measurements. Measurements were logged onto the hard disk of a Lenovo Thinkpad X61s PC laptop via National Instruments data acquisition software LabVIEW. First hand draft graphs of each of the Quality Controlled flights together with real time photos, when available, are also attached.

All flights (#70)
Flight0804nr1, Flight0804nr2, Flight0804nr3, Flight0804nr4, Flight0804nr5, Flight0805nr1, Flight0805nr2, Flight0806nr1, Flight0806nr2, Flight0806nr3, Flight0807nr1, Flight0807nr2, Flight0807nr3, Flight0808nr1, Flight0809nr1, Flight0809nr2, Flight0810nr1, Flight0810nr2, Flight0810nr3, Flight0811nr1, Flight0815nr1, Flight0816nr1, Flight0817nr1, Flight0820nr1, Flight0820nr2, Flight0820nr3, Flight0820nr4, Flight0820nr5, Flight0821nr1, Flight0822nr1, Flight0824nr1, Flight0824nr2, Flight0824nr3, Flight0824nr4, Flight0824nr5, Flight0825nr1, Flight0825nr2, Flight0825nr3, Flight0826nr1, Flight0826nr2, Flight0826nr3, Flight0826nr4, Flight0827nr1, Flight0827nr2, Flight0827nr3, Flight0827nr4, Flight0828nr1, Flight0828nr2, Flight0828nr3, Flight0829nr1, Flight0829nr2, Flight0829nr3, Flight0830nr1, Flight0830nr2, Flight0830nr3, Flight0831nr1, Flight0831nr2, Flight0831nr3, Flight0831nr4, Flight0901nr1, Flight0901nr2, Flight0901nr3, Flight0901nr4, Flight0903nr1, Flight0904nr1, Flight0905nr1, Flight0905nr2, Flight0906nr1, Flight0907nr1, Flight0907nr2

Flights Quality Insured (#45)
Flight0810nr3, Flight0815nr1, Flight0816nr1, Flight0817nr1, Flight0820nr1, Flight0820nr3, Flight0820nr4, Flight0820nr5, Flight0821nr1, Flight0822nr1, Flight0824nr1, Flight0824nr3, Flight0824nr4, Flight0824nr5, Flight0825nr1, Flight0825nr2, Flight0825nr3, Flight0826nr1, Flight0826nr2, Flight0826nr3, Flight0826nr4, Flight0827nr3, Flight0827nr4, Flight0828nr1, Flight0828nr3, Flight0829nr1, Flight0829nr2, Flight0829nr3, Flight0830nr1, Flight0830nr2, Flight0830nr3, Flight0831nr1, Flight0831nr2, Flight0831nr3, Flight0831nr4, Flight0901nr1, Flight0901nr2, Flight0901nr3, Flight0901nr4, Flight0903nr1, Flight0905nr1, Flight0905nr2, Flight0906nr1, Flight0907nr1, Flight0907nr2

Roles of data creators

Caroline Leck was overall responsible for planning and implementation of the helicopter flights and for the data evaluation and quality ensuarance of the aerosol observations. The meteorological observations were managed, evaluated and quality ensured by Joseph Sedlar. Erik Swietlicki was responsible for designing and setting up the aerosol instrumentation. Staffan Sjögren and Sarah Norris managed the aerosol observations. Barbara Brooks was responsible for one of the instruments that measured particles in the helicopter, but she was not present onboard during the expedition.

Related study

The Kupiszewski et al. (2013) study sheds light on the characteristics of Arctic aerosol particles and their vertical distribution throughout the lower atmosphere during a three-week period when the Swedish icebreaker Oden was anchored to a drifting ice floe, north of 87°.

Origin of the dataset

The dataset was originally made available on 12 July 2011, under the title ASCOS Helicopter profiling of aerosol and meteorological parameters, to participants in the ASCOS expedition and their collaborators, on a website that is now obsolete.

Original address: http://www.ascos.se/index.php?q=node/393