Processed micro rain radar data from expedition ARTofMELT, Arctic Ocean, 2023

Heather Guy, Ian Brooks

Measurements obtained from the micro rain radar (METEK MRR-2) deployed on the foredeck of the Swedish icebreaker Oden during the expedition ARTofMELT (Atmospheric Rivers and the Onset of Arctic Melt) in the Fram Strait pack ice during the spring transition, 8 May to 14 June of 2023. Measurements ran continuously during the whole expedition.

The raw MRR-2 spectral data have been processed using the software IMProToo, and the output variables include effective reflectivity, Doppler vertical Velocity, Doppler spectral width and signal to noise ratio, in addition to quality control and diagnostic variables, and the spectral reflectivity data both before and after the application of the IMProToo dealiasing procedure.

Citation

Heather Guy, Ian Brooks (2024) Processed micro rain radar data from expedition ARTofMELT, Arctic Ocean, 2023. Dataset version 1. Bolin Centre Database. https://doi.org/10.17043/oden-artofmelt-2023-micro-rain-radar-1

References

Maahn M, Kollias P (2012) Improved Micro Rain Radar snow measurements using Doppler spectra post-processing. Atmospheric Measurement Techniques 5:2661–2673. https://doi.org/10.5194/amt-5-2661-2012

Klugmann D, Heinsohn K, Kirtzel HJ (1996) A low cost 24 GHz FM-CW Doppler radar rain profiler. Contributions to atmospheric physics 69:247–253. https://api.semanticscholar.org/CorpusID:130281635

Data description

This dataset is provided in a zipped file containing 36 NetCDF (.nc) files, one file per day, 2023-05-09 to 2023-06-13 inclusive. The total file size is about 20 GB (compressed 3 GB), or ~580 MB per daily file.

Each file contains 36 variables with dimensions of range and time, where range is the number of the bin above the instrument (31 bins in total). The spectral reflectivities and associated noise masks are included with dimensions velocity (for the dealised spectra) and velocity_noDA for the original raw spectra.

The primary variables for most users are the effective radar reflectivity (Ze), Doppler velocity (W), Doppler spectral width (spectralWidth), and the quality control flag (quality) that indicates which data are good to use. Additional variables include the raw and dealiased Doppler spectra, noise mask, raw Doppler spectral moments (without dealiasing) and spectral statistics.

A detailed list of variables is included below.

Dimensions

• time Measurement time. Following Meteks convention, the dataset at e.g. 11:55 contains all recorded raw between 11:54:00 and 11:54:59 (if delta t = 60s)!
• range Range bins, #
• velocity Doppler velocity bins. If dealiasing is applied, the spectra are triplicated, m s^-1
• velocity_noDA Original, non dealiased, Doppler velocity bins., m s^-1

Variables

Divided into:

• Primary user variables
• Technical, housekeeping and diagnostic variables

Detailed lists:

• Primary user variables
  • time Measurement time, see above
  • day_of_year time as decimal day of year
  • altitude m
  • height height above instrument, m
  • latitude degree_north
  • longitude degree_east
  • SNR signal to noise ratio of the most significant peak, never dealiased!, dB
  • Ze reflectivity of the most significant peak, dBz
  • spectralWidth spectral width of the most significant peak, m s^-1
  • quality Quality flag consists of 18-bits, flag 1 is the least significant. Flags 1-5 can usually be ignored. Flags 8-12 indicate reasons why a spectrum does not contain a peak. Flags 16-18 are serious errors, do not use these data. See flag_meanings for the definition of each bit., bin
  • W Mean Doppler Velocity of the most significant peak, m s^-1
• Technical, housekeeping and diagnostic variables
  • eta_noDA spectral reflectivities NOT dealiased, mm^6 m^-3
  • etaMask_noDA noise mask of eta NOT dealiased, 0: signal, 1: noise, bool
  • eta spectral reflectivities. if dealiasing is applied, the spectra are triplicated, thus up to three peaks can occur from -12 to +24 m s^-1. However, only one peak is not masked in etaMask, mm^6 m^-3
  • etaMask noise mask of eta, 0: signal, 1:noise, bool
  • `TF: Transfer Function (see Metek's documentation)
  • Ze_noDA reflectivity of the most significant peak, not dealiased, dBz
  • spectralWidth_noDA spectral width of the most significant peak, not dealiased, m s^-1
  • skewness_noDA Skewness of the most significant peak, not dealiased
  • skewness Skewness of the most significant peak
  • kurtosis_noDA kurtosis of the most significant peak, not dealiased
  • kurtosis kurtosis of the most significant peak
  • peakVelLeftBorder_noDA Doppler velocity of the left border of the peak, not dealiased, m s^-1
  • peakVelLeftBorder Doppler velocity of the left border of the peak, m s^-1
  • peakVelRightBorder_noDA Doppler velocity of the right border of the peak, not dealiased, m s^-1
  • peakVelRightBorder Doppler velocity of the right border of the peak, m s^-1
  • leftSlope_noDA Slope at the left side of the peak, not dealiased, dB/(m s^-1)
  • leftSlope Slope at the left side of the peak, dB/(m s^-1)
  • rightSlope_noDA Slope at the right side of the peak, not dealiased, dB/(m s^-1)
  • rightSlope Slope at the right side of the peak, dB/(m s^-1)
  • W_noDA Mean Doppler Velocity of the most significant peak, not dealiased, m s^-1
  • etaNoiseAve mean noise of one Doppler Spectrum in the same units as eta, never dealiased, mm^6 m^-3
  • etaNoiseStd std of noise of one Doppler Spectrum in the same units as eta, never dealiased, mm^6 m^-3

Comments

Measurement system

The data were obtained from the NCAS AMOF Micro Rain Radar (METEK MRR-2).

Quality control

The raw data was processed using the IMProToo software (see references). This software applies a noise removal and dealiasing algorithm to the MRR raw spectra data, and a peak detection algorithm that is used for the calculation of the radar moments. A 'quality' flag is included in the file that indicates success of the algorithm at each time/height bin.

Associated raw data and code

IMProToo is available at GitHub. These data were generated using IMProToo v0.107. Raw METEK binary files are available upon request.

The expedition

Data were collected during the ARTofMELT 2023 expedition on board the Swedish icebreaker Oden, which was organized by the Swedish Polar Research Secretariat from 8 May through 14 June, 2023.

Data creators' roles

• Heather Guy (operator and dataset creator)
• Ian Brooks (operator and principal investigator)