Weather and navigation data from the high-Arctic ASCOS expedition 2008

Michael Tjernström

The Icebreaker Oden's weather station was mostly located on the 7th deck about 27 m above sea level, on top of the bridge. Sensors were distributed over the 7th deck (temperature, humidity and visibility), on the bridge (pressure) and in the top mast of Oden (2D sonic anemometers for wind speed and direction). In addition to these basic meteorology observations, this data file also contains the ship's navigation information (position, speed, course and heading). Wind information is provided both relative to the ship and corrected “true” winds, taking the vessel's movement into account. Care should always be used when measuring on a ship, especially for wind that more than likely is affected by the flow distortion around the ship. Wind, temperature and relative humidity data was cross-checked with an additional weather station (WeatherPak) and agree as well as can be expected for two different locations on a ship.

Citation

Michael Tjernström (2018) Weather and navigation data from the high-Arctic ASCOS expedition 2008. Dataset version 1. Bolin Centre Database. https://doi.org/10.17043/oden-ascos-2008-weather-navigation-1

References

Tjernström, M. et al. 2014. The Arctic Summer Cloud Ocean Study (ASCOS): overview and experimental design. Atmospheric Chemistry and Physics, 14, 2823–2869. https://doi.org/10.5194/acp-14-2823-2014

Data description

The file zip-file OdenWeatherStation contains ascii and matlab (struct) versions of the data from the Oden weather station that contains reasonably cleaned up and QC:ed data. Unreasonable values have been replaced by NaN. Some of this QC was performed by comparison to the WeatherPak and metalley data, but outisde of the ice camp, a fair amount of subject judgement was applied. Whenever in doubt data has been retianed, so use with some care. 

The data in the file is:

1:  Regular UTC time (DoY_UTC)
2:  Local solar time (DoY)
3:  Year
4:  Month
5:  Day
6:  Hour
7:  Minute
8:  Latitude (deg)
9:  Longitude (deg)
10: Ships speed over ground (knots)
11: Ships course over ground (deg)
12: Ships heading (deg)
13: Wind direction relative to ships bow (deg)
14: Wind speed relative to ship (m/s)
15: Corrected true wind direction (deg)
16: Corrected true wind speed (m/s)
17: West-easts wind speed component (m/s)
18: South-north wind speed component (m/s)
19: Air temperature (degC)
20: Relative humidity over liquid water (%)
21: Relative humidity over ice (%)
22: Specific humidity (g/kg)
23: Visibility (km)
24: Measured pressure (hPa)
25: Surface pressure reduced using normal atmosphere (hpa)
26: Surface pressure reduced using actual atmosphere (hpa)
27: Pressure tendency measured over past 3 hours (hPa/3h)

Comments

ASCOS carried two weather stations: Oden's own weather station and an additional weather station, here referred to as “WeatherPak”. Both were located mostly on Oden's 7th deck about 27 m above sea level, on top of the bridge. Sensors for the Oden weather station were distributed over the 7th deck (temperature, humidity and visibility), on the bridge (pressure) and in the top mast of Oden (2D sonic anemometers for wind speed and direction). In addition to these basic meteorology observations, this data file also contains ships navigation information (position, speed, course and heading). Wind information is provided both relative to the ship (w/ direction 360° for winds on the bow) and corrected “true” winds, taking Oden's movement into account. The WeatherPak station is an integrated unit mounted approximately mid-ship on the forward railing on the 7th deck. Variables measured include wind speed and direction, temperature, relative humidity, pressure, and solar and UV radiation. Also here, winds are given both relative to the ship and as “true winds”. Note that winds from the aft (relative wind direction from approximately 90° to 270° are in the wake of the ship's main mast. Care should always be used when measuring on a ship, especially for wind that more than likely is affected by the flow distortion around the ship. Temperature may show a slight warm bias, especially when the real temperature is low due to heat from the superstructure. Wind, temperature and RH data was cross-checked between the two weather stations and agrees as well as can be expected for two different locations on a ship. WeatherPak wind speeds are systematically lower than for the Oden weather station, by some 30%. It is likely that the Oden wind speeds are higher than reality, because of a Venturi-effect from the ships superstructure, while the WeatherPak wind speed may be low because of the wake from the superstructure. The WeatherPak temperature is consistently about 1 °C warmer than the weather station, which is likely a calibration problem, the RH has poor correlation and the shortwave radiation is slightly low in the 75-125 Wm^-2 range and somewhat too high above 250 Wm^-2.

Original address: http://www.ascos.se/index.php?q=node/233

Files:
OdenWeatherStation.zip (11.13 MB)