sample of computing extents from rutger's snowcover site.

read snowcover file.ipynb

{
 "metadata": {
  "name": ""
 },
 "nbformat": 3,
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 "worksheets": [
  {
   "cells": [
    {
     "cell_type": "markdown",
     "source": [
      "# Questions about NetCDF CDR data vs. File downloaded from Rutger's snow website.\n"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# require numpy and h5py\n",
      "import numpy as np\n",
      "import h5py\n"
     ],
     "language": "python",
     "outputs": [],
     "prompt_number": 14
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# use the Rutgers netcdf file\n",
      "fn = '/Users/savoie/projects/sota/snowcover/input_data/nhsce_v01r01_19661004_20131202.nc'"
     ],
     "language": "python",
     "outputs": [],
     "prompt_number": 15
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "nc = h5py.File(fn, 'r')\n",
      "lats = nc['latitude']\n",
      "lons = nc['longitude']\n",
      "area = nc['area']\n",
      "time = nc['time']\n",
      "data = nc['snow_cover_extent']"
     ],
     "language": "python",
     "outputs": [],
     "prompt_number": 65
    },
    {
     "cell_type": "markdown",
     "source": [
      "## The area of the grids in the files are 88x88\n",
      "This is different from the 89x89 I expect from the documentation on the website.\n",
      "[http://climate.rutgers.edu/snowcover/docs.php?target=vis]"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "print(area.shape)\n",
      "print(data.shape)"
     ],
     "language": "python",
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "(88, 88)\n",
        "(2461, 88, 88)\n"
       ]
      }
     ],
     "prompt_number": 66
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "print( time[:])\n",
      "print(dict(time.attrs.items())['units'])"
     ],
     "language": "python",
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "[    7    14    21 ..., 17213 17220 17227]\n",
        "days since 1966-10-03\n"
       ]
      }
     ],
     "prompt_number": 61
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "def compute_area(idx):\n",
      "    # return the sum of the area grid * snow_cover_extent grid\n",
      "    griddata = area * data[idx, :, :]\n",
      "    return np.sum(griddata)"
     ],
     "language": "python",
     "outputs": [],
     "prompt_number": 62
    },
    {
     "cell_type": "markdown",
     "source": [
      "## Here's the first 10 values in `wkcov.nhland.txt` from  \n",
      "[http://climate.rutgers.edu/snowcover/files/wkcov.nhland.txt]\n",
      "\n",
      "\n",
      "    1966  40  15187919\n",
      "    1966  41  22836856\n",
      "    1966  42  26497731\n",
      "    1966  43  26952159\n",
      "    1966  44  30329648\n",
      "    1966  45  36078179\n",
      "    1966  46  36287197\n",
      "    1966  47  35991970\n",
      "    1966  48  38597502\n",
      "    1966  49  40541181\n"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "## here are the same values comptued from the NetCDF file."
     ],
     "language": "python",
     "outputs": [],
     "prompt_number": 63
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "for i in np.arange(10):\n",
      "    print \"{:8.0f}\".format(compute_area(i))\n"
     ],
     "language": "python",
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "15187923\n",
        "22836860\n",
        "26497726\n",
        "26952160\n",
        "30329638\n",
        "36078196\n",
        "36287192\n",
        "35991976\n",
        "38597520\n",
        "40541208\n"
       ]
      }
     ],
     "prompt_number": 64
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "## so I'm confused and can't reconcile the data from the rutgers text file and the data in the netcdf file."
     ],
     "language": "python",
     "outputs": []
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [],
     "language": "python",
     "outputs": []
    }
   ]
  }
 ]
}