Ola Persson
Wind profiler consensus data was obtained using a Doppler radar wind profilers transmitting at 449MHz. Using the Doppler shift of the return signals and algebra, the wind speed and direction as a function of height, can be estimated. The wind profiler is sensitive to water vapor in the atmosphere and hence performs best in moist air. It was deployed on top of the port three containers located on the roof of the foredeck lab at the icebreaker Oden and operated from the start of the ice drift through the rest of the expedition.
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Citation
Ola Persson (2018) Wind profiler consensus data from the high-Arctic ASCOS expedition 2008. Dataset version 1. Bolin Centre Database. https://doi.org/10.17043/oden-ascos-2008-wind-consensus-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
This zip_file contains the half-hour consensus profile data from the 449 MHz wind profiler on the Oden during ASCOS. Version 1 contains netcdf files of the consensus half-hourly wind profile/signal-to-noise. It only contains data from the drift portion of the cruise (YD228–245; Aug. 15 – Sep. 1). Data from the return cruise is available but have not yet been corrected for ship motion. The radar altitude was estimated at 10 m mean sea level, which should be added to the height data, which is given as above ground level (radar level).
During the drift, various radar parameters were used between YD228 and YD234. The consensus data for YD228 and YD234 through YD243 and YD245 are calculated after the spectral data has undergone subjective hand-editing. The consensus data for the other days (YD229–233, YD244) have not undergone the hand-editing nor the Weber-Wurtz automated editing (see below), though it has been scrutinized and subjectively validated as “usable” by an experienced engineer and been compared favorably with sounding data. The computation of the moments and the consensus data from the spectra uses a wavelet/multi-peak picking technique optimized to identify the wind signal in the spectra. Consensus data that have been run through the Webber-Wurtz editing software have also been calculated. Though the Weber-Wurz consensus profiles show greater amounts of data, the hand-edited consensus data given here is of higher quality. The Weber-Wurtz edited data are not included in this zip_file, though they can be requested by contacting the PI [Dr. Ola Persson ([javascript protected email address])].
The consensus wind profiles from the low mode (Mode 1) and the high mode (Mode 2) are given in two different files. The low mode gives data from 144 m – 4028 m, with 30 m resolution. The high mode gives 97 m resolution data in the range of 469–8081 m. In comparisons with each other and with rawinsonde data, the following observations have been made:
1) in the overlap range, differences between the two modes are on the order of the RMS difference between the sonde and the wind profiler data (~ 1-2 m/s).
2) The vertical average of Mode 1 does not always produce the Mode 2 values.
3) Mode 2 looks smoother and seems to have fewer data gaps in the overlap range (generally due to edited data points in mode 1),
4) Mode 1 has more variability than Mode 2 but is more like the sondes in this respect.
5) The differences between the modes are likely due to the larger volume for mode 2 and the effect of pulse coding for mode 1 to get the lower range and higher resolution.
6) Because of the different resolution of the two wind profiler modes and the conceptual sampling differences between half-hourly averages of volumes and the more localized in time and space sondes, one mode isn't obviously more correct than the other
USAGE RECOMMENDATIONS: If you are looking for winds at low level and/or need high vertical resolution, use Mode 1. Otherwise use Mode 2. If there is a gap in the Mode 1 data within the overlap height range, check Mode 2. If a data set with the greatest height range coverage is needed, the user can combine the two modes, noting the slight differences in the sampling times. The data is free to use, but it is recommended to contact the PI in advance.
Each daily consensus netcdf file contains:
a) station name – SMLO - Oden's WMO signature
b) various header information
c) lat,lon at the time of the profile
d) ships heading at the time of the profile
e) data processing information
f) beam-orientation information
g) half-hourly profiles of wind speed, wind direction, vertical velocity, and signal-to-noise ratio
h) data from either Mode 1 or Mode 2
Specific variable information and units are found in the netcdf header information. The netcdf global attribute information is given below.
Comments
Two Doppler wind profilers were used in ASCOS; one radar profiler transmitting at 449MHz and one SODAR (SOund Detection and Ranging) transmitting audible sound pulses at several wave lengths. Both work from the same principles, transmitting beams at an angle to the vertical in different directions. Using the Doppler shift of the return signals and algebra the wind speed and direction can be estimated. Both instruments are phased-array instruments, meaning that there are no moveable parts generating the different beams at different angles; this is instead accomplished electronically.
The 449MHz wind profiler is sensitive to water vapor in the atmosphere and hence has the best results in moist air, and was deployed at the start of the ice drift on top of the port three containers located on the roof of the foredeck lab and operated through the rest of the expedition. Its return signal strength can, in addition to the Doppler information, be used to analyze the vertical structure of the atmosphere but only in a relative sense since the water vapor content is variable.
The SODAR is sensitive to water vapor fluctuations (turbulence) and its return signal can therefore, in addition to the Doppler information, be used to derive information about turbulence in the boundary layer. The SODAR is sensitive to ambient noise and hence was deployed on the ice and only operated during the ice drift.
Original address: http://www.ascos.se/index.php?q=node/281
Files:
ASCOS_data_449windprofiler_consensus_netcdf_v1.ZIP (651.3 KB)
