`cpomsec_interp` documentation

`cpomsec_interp` interpolates Antarctic Ice Sheet surface elevation trends from CPOM. Get the data here and follow the SEC link.

## Contents

## Syntax

dhdt = cpomsec_interp(lati,loni) dhdt = cpomsec_interp(xi,yi) dhdt = cpomsec_interp(...,'sensor',satellite) dhdt = cpomsec_interp(...,'method',InterpolationMethod) sigma = cpomsec_interp(...,'variable',VariableName)

## Description

`dhdt = cpomsec_interp(lati,loni)` gives values of surface elevation change in m/yr at the geolocations `lati,loni`.

`dhdt = cpomsec_interp(xi,yi)` as above, but for polar stereographic (ps71) coordinates `xi,yi` in meters.

`dhdt = cpomsec_interp(...,'sensor',satellite)` specifies a sensor for which the trends were obtained. Options are:

`'cs2'`CryoSat-2: 2010-07-12 to 2015-04-01 (default)`'env'`Envisat: 2002-04-09 to 2010-10-18`'ers2'`ERS-2: 1995-05-13 to 2003-07-04`'ers1'`ERS-1: 1991-08-03 to 1996-06-02

`dhdt = cpomsec_interp(...,'method',InterpolationMethod)` specifies an interpolation method for interp2. Default is `'linear'`, but wherever there are grid cells with missing or wildly inaccurate grid cell, note that linear interpolation will result in a larger area of missing or inaccurate data. Depending on what you're doing, you may wish to go with `'nearest'` instead.

`sigma = cpomsec_interp(...,'variable',VariableName)` specifies any of the following datasets:

`'dhdt'`(m/yr) rate of surface elevation change (SEC) with time (default)`'min_time'`(decimal year) the earliest time in the time-series used to calculate dh/dt`'max_time'`(decimal year) last time in the time-series used to calculate dh/dt`'slope'`(degrees) calculated slope in grid cell from plane fit model processing`'total_measurements_used'`total number of contributing measurements used to calculate dh/dt after iterative plane fit editing`'total_sat_measurements'`total number of contributing satellite measurements used to calculate dh/dt before iterative plane fit`'rms'`(m) r.m.s of the surface corrected elevation residuals to the fit`'chisqr'`(m) unreduced chi-sq goodness of fit statistic of dh/dt calculation`'sigma'`(m/yr) 1-sigma uncertainty estimate statistic of dh/dt calculation

## Example

Below we make a map of surface elevation change for West Antarctica for the epoch 2010 to 2015.

In addition to standard Antarctic Mapping Tools functions, I'm also using the `cmocean` function (Thyng et al., 2016) to make the fancy red-white-blue colormap and `modismoaps` to underlay a MODIS Mosaic of Antarctica image.

% Make a 1500 km wide grid at 2 km resolution: [lat,lon] = psgrid('west antarctica',1500,2); % Get a value of dh/dt at each grid point: dhdt = cpomsec_interp(lat,lon); % Eliminate all data points where uncertainty exceeds 3 m/yr: sigma = cpomsec_interp(lat,lon,'variable','sigma'); dhdt(sigma>3) = NaN; % Make a map: h = pcolorps(lat,lon,dhdt); set(h,'facealpha',0.8) % makes the trend map semitransparent axis tight off % eliminates white space, turns off tick labels caxis([-2 2]) % sets color axis limits cb = colorbar; ylabel(cb,'dhdt (m yr^{-1})') modismoaps % underlays MODIS Mosaic of Antarctica map mapzoomps('ne') % places an inset map in the upper right corner cmocean('-balance') % sets colormap to cmocean with red on bottom scalebarps('color','white') scarlabel({'Pine Island Glacier';'Thwaites Glacier';'Crosson Ice Shelf';'Dotson Ice Shelf'},... 'fontangle','italic','fontsize',10,'color','yellow')

## Requirements:

To use this function you must have:

1. Antarctic Mapping Tools for Matlab, found here.

2. Surface Elevation Change (SEC) data from CPOM, found here.

## Citations:

If you use this function, please cite the following:

Shepherd, A., Hogg, A., Muir, A., McMillan, M. (2016): Antarctic-CCI-SEC-v1.0, Surface Elevation Changes of the Antarctic Ice Sheet from Satellite Radar Altimetry, Released 29

Greene, C. A., Gwyther, D. E., & Blankenship, D. D. Antarctic Mapping Tools for Matlab. Computers & Geosciences. 104 (2017) pp.151-157. http://dx.doi.org/10.1016/j.cageo.2016.08.003

## Author Info

The `cpomsec_interp` function and this documentation were written by Chad A. Greene of the University of Texas at Austin, May 2018.