.. _drifter_eke:

Surface Current Variance from Drifter Data
==========================================

Description
-----------
Contains information about current variance (eddy kinetic energy) derived from
residuals with respect to the time-mean, seasonal, spatial gradient, and
SOI-related currents. The file contains the following variables:

* Lon (1x720): longitude (degrees), negative=West.
* Lat (1x317): latitude (degrees), 73S to 85N.
* Up2bar (317x720): Zonal Velocity Variance, mean(u' ^2) (m^2/s^2).
* Vp2bar (317x720): Meridional Velocity Variance, mean(v' ^2) (m^2/s^2).
* rA (317x720): Variance ellipse semimajor axis (m^2/s^2).
* rB (317x720): Variance ellipse semiminor axis (m^2/s^2).
* angle (317x720): Orientation angle of variance ellipse (degrees, 0=east/west).
* N (317x720): Number of drifter-days per square degree.

Note that Up2bar+Vp2bar=rA+rB, which is twice the eddy kinetic energy.

For more information, see: http://www.aoml.noaa.gov/phod/gdp/mean_velocity.php

The global near-surface current climatology described here is publicly available
through the `Gulf of Mexico Research Initiative Information & Data Cooperative (GRIIDC)`_, and through
`NOAA/AOML`_ at
http://www.aoml.noaa.gov/phod/dac/drifter_variance.nc.

This climatology was developed by Rick Lumpkin (NOAA/AOML) and Lucas Laurindo
(Univ. Miami), in collaboration with Arthur Mariano (Univ. Miami), Mayra Pazos
(NOAA/AOML), and Erik Valdes (CIMAS/AOML). Previous versions were developed with
Gregory Johnson (NOAA/PMEL), Silvia Garzoli (NOAA/AOML), Jessica Redman (CIMAS),
and Zulema Garraffo(Univ. Miami).

Source
------
`NOAA/AOML`_

Release Policy
--------------
Please cite as reference:
Laurindo, L., A. Mariano, and R. Lumpkin, 2017: An improved near-surface
velocity climatology for the global ocean from drifter observations Deep-Sea
Res. I, 124, pp.73-92, doi:10.1016/j.dsr.2017.04.009.

References
----------
`Laurindo et al. (2017)`_

`bibtex file`_

MPAS-Analysis Tasks
-------------------
- :ref:`task_climatologyMapEKE`

.. _`Gulf of Mexico Research Initiative Information & Data Cooperative (GRIIDC)`: http://dx.doi.org/10.7266/N7SJ1HN5
.. _`NOAA/AOML`: http://www.aoml.noaa.gov/phod/dac/dac_meanvel.php
.. _`NOAA/AOML`: http://www.aoml.noaa.gov/phod/dac/dac_meanvel.php
.. _`Laurindo et al. (2017)`: https://doi.org/10.1016/j.dsr.2017.04.009
.. _`bibtex file`: https://web.lcrc.anl.gov/public/e3sm/diagnostics/observations/Ocean/EKE/obs.bib