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MAGIC Ship Motion Corrections for the ARM Radars. David Troyan First MAGIC Workshop. Ship Motion. There are three primary angular variables that indicate the ship’s location relative to the Earth-based vertical coordinates: Pitch: Rotation about the minor axis (bow up is positive)
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MAGIC Ship Motion Corrections for the ARM Radars David Troyan First MAGIC Workshop
Ship Motion • There are three primary angular variables that indicate the ship’s location relative to the Earth-based vertical coordinates: • Pitch: Rotation about the minor axis (bow up is positive) • Roll: Rotation about the major axis (port up is positive) • Yaw: Heading angle rotation (clockwise is positive) • Heave is the distance of rise and fall from a standard calm sea • Heave velocity is rate of heave change • Sway, and Surge are not used in the transforms
Ship Motion Applied to Radars • Shipboard Radars: KAZR – Ka-Band ARM Zenith Radar (not stabilized) MWACR – Marine W-Band ARM Cloud Radar (stabilized) • Correction to the Doppler Velocity: • KAZR: Determining the vertical velocity that would have been measured at each sample time if the radar beam was vertical Geometric correction Contribution to horizontal wind • KAZR and MWACR: Adding the ship heave velocity to the vertical velocity component to determine the corrected, Earth-relative, vertical velocity
Ship Motion Applied to Radars II • Correction to the height coordinates • Geometric correction • Time varying • Implications are that height dependent variables – e.g. cloud base height, cloud tops – are not on a uniform grid • Both KAZR and MWACR
Examples of Differences Original Motion Corrected Difference KAZRGE 2012-12-11 Range (m/s): -6(Blue) to 2 (Red) Range (m/s): -6(Blue) to 2 (Red) Range (m/s): -1.5(Blue) to 1.5 (Red) Original Motion Corrected Difference MWACR 2012-12-11 Range (m/s): -6(Blue) to 2 (Red) Range (m/s): -6(Blue) to -6 (Red) Range (m/s): -1.5(Blue) to 1.5 (Red)
Data Status and Future Work • Data is located in the Evaluation Area on the ARM data page (listed under shipcor) • Datastream names are magkazrshipcor1ci, magkazrshipcor1ge, magmwacrshipcor1 • Available time is from 9/22/12 to 1/8/13 • Please evaluate these data and provide feedback (especially for the height field issue) • Additional instruments will be corrected for height fields: VaisalaCeliometer (VCEIL) High Spectral Resolution Lidar (HSRL) MicropulseLidar (MPL)