GOES-17、18MCMIPC 系列 ABI 2 级云层和水汽数据集

// Band aliases.
var BLUE = 'CMI_C01';
var RED = 'CMI_C02';
var VEGGIE = 'CMI_C03';
var GREEN = 'GREEN';
// 16 pairs of CMI and DQF followed by Bah 2018 synthetic green.
// Band numbers in the EE asset, 0-based.
var NUM_BANDS = 33;
// Skipping the interleaved DQF bands.
var BLUE_BAND_INDEX = (1 - 1) * 2;
var RED_BAND_INDEX = (2 - 1) * 2;
var VEGGIE_BAND_INDEX = (3 - 1) * 2;
var GREEN_BAND_INDEX = NUM_BANDS - 1;

// Visualization range for GOES RGB.
var GOES_MIN = 0.0;
var GOES_MAX = 0.7;  // Alternatively 1.0 or 1.3.
var GAMMA = 1.3;

var goesRgbViz = {
  bands: [RED, GREEN, BLUE],
  min: GOES_MIN,
  max: GOES_MAX,
  gamma: GAMMA
};

var applyScaleAndOffset = function(image) {
  image = ee.Image(image);
  var bands = new Array(NUM_BANDS);
  for (var i = 1; i < 17; i++) {
    var bandName = 'CMI_C' + (100 + i + '').slice(-2);
    var offset = ee.Number(image.get(bandName + '_offset'));
    var scale =  ee.Number(image.get(bandName + '_scale'));
    bands[(i-1) * 2] = image.select(bandName).multiply(scale).add(offset);

    var dqfName = 'DQF_C' + (100 + i + '').slice(-2);
    bands[(i-1) * 2 + 1] = image.select(dqfName);
  }

  // Bah, Gunshor, Schmit, Generation of GOES-16 True Color Imagery without a
  // Green Band, 2018. https://doi.org/10.1029/2018EA000379
  // Green = 0.45 * Red + 0.10 * NIR + 0.45 * Blue
  var green1 = bands[RED_BAND_INDEX].multiply(0.45);
  var green2 = bands[VEGGIE_BAND_INDEX].multiply(0.10);
  var green3 = bands[BLUE_BAND_INDEX].multiply(0.45);
  var green = green1.add(green2).add(green3);
  bands[GREEN_BAND_INDEX] = green.rename(GREEN);

  return ee.Image(ee.Image(bands).copyProperties(image, image.propertyNames()));
};

var collection = 'NOAA/GOES/17/MCMIPC/';
var imageName = '2020211190617600000';
var assetId = collection + imageName;
var image = applyScaleAndOffset(assetId);
Map.setCenter(-120, 43, 5);
Map.addLayer(image, goesRgbViz);

// Band aliases.
var BLUE = 'CMI_C01';
var RED = 'CMI_C02';
var VEGGIE = 'CMI_C03';
var GREEN = 'GREEN';
// 16 pairs of CMI and DQF followed by Bah 2018 synthetic green.
// Band numbers in the EE asset, 0-based.
var NUM_BANDS = 33;
// Skipping the interleaved DQF bands.
var BLUE_BAND_INDEX = (1 - 1) * 2;
var RED_BAND_INDEX = (2 - 1) * 2;
var VEGGIE_BAND_INDEX = (3 - 1) * 2;
var GREEN_BAND_INDEX = NUM_BANDS - 1;

// Visualization range for GOES RGB.
var GOES_MIN = 0.0;
var GOES_MAX = 0.7;  // Alternatively 1.0 or 1.3.
var GAMMA = 1.3;

var goesRgbViz = {
  bands: [RED, GREEN, BLUE],
  min: GOES_MIN,
  max: GOES_MAX,
  gamma: GAMMA
};

var applyScaleAndOffset = function(image) {
  image = ee.Image(image);
  var bands = new Array(NUM_BANDS);
  for (var i = 1; i < 17; i++) {
    var bandName = 'CMI_C' + (100 + i + '').slice(-2);
    var offset = ee.Number(image.get(bandName + '_offset'));
    var scale =  ee.Number(image.get(bandName + '_scale'));
    bands[(i-1) * 2] = image.select(bandName).multiply(scale).add(offset);

    var dqfName = 'DQF_C' + (100 + i + '').slice(-2);
    bands[(i-1) * 2 + 1] = image.select(dqfName);
  }

  // Bah, Gunshor, Schmit, Generation of GOES-16 True Color Imagery without a
  // Green Band, 2018. https://doi.org/10.1029/2018EA000379
  // Green = 0.45 * Red + 0.10 * NIR + 0.45 * Blue
  var green1 = bands[RED_BAND_INDEX].multiply(0.45);
  var green2 = bands[VEGGIE_BAND_INDEX].multiply(0.10);
  var green3 = bands[BLUE_BAND_INDEX].multiply(0.45);
  var green = green1.add(green2).add(green3);
  bands[GREEN_BAND_INDEX] = green.rename(GREEN);

  return ee.Image(ee.Image(bands).copyProperties(image, image.propertyNames()));
};

var collection = 'NOAA/GOES/17/MCMIPF/';
var imageName = '2020211200032100000';
var assetId = collection + imageName;
var image = applyScaleAndOffset(assetId);
Map.addLayer(image, goesRgbViz);

// Demonstrates displaying GOES-17 Mesoscale images.

// Band names.
var BLUE = 'CMI_C01';
var RED = 'CMI_C02';
var VEGGIE = 'CMI_C03';
var GREEN = 'GREEN';

/**
 * Properly scales an MCMIPM image.
 *
 * @param {ee.Image} image An unaltered MCMIPM image.
 * @return {ee.Image}
 */
var applyScaleAndOffset = function(image) {
  var names = image.select('CMI_C..').bandNames();

  // Scale the radiance bands using the image's metadata.
  var scales = names.map(function(name) {
    return image.getNumber(ee.String(name).cat('_scale'));
  });
  var offsets = names.map(function(name) {
    return image.getNumber(ee.String(name).cat('_offset'));
  });
  var scaled = image.select('CMI_C..')
                   .multiply(ee.Image.constant(scales))
                   .add(ee.Image.constant(offsets));

  return image.addBands({srcImg: scaled, overwrite: true});
};

/**
 * Computes and adds a green radiance band to a MCMIPM image.
 *
 * The image must already have been properly scaled via applyScaleAndOffset.
 *
 * For more information on computing the green band, see:
 *   https://doi.org/10.1029/2018EA000379
 *
 * @param {ee.Image} image An image to add a green radiance band to. It
 *     must be the result of the applyScaleAndOffset function.
 * @return {ee.Image}
 */
var addGreenBand = function(image) {
  function toBandExpression(bandName) { return 'b(\'' + bandName + '\')'; }

  var B_BLUE = toBandExpression(BLUE);
  var B_RED = toBandExpression(RED);
  var B_VEGGIE = toBandExpression(VEGGIE);

  // Green = 0.45 * Red + 0.10 * NIR + 0.45 * Blue
  var GREEN_EXPR = GREEN + ' = 0.45 * ' + B_RED + ' + 0.10 * ' + B_VEGGIE +
      ' + 0.45 * ' + B_BLUE;

  var green = image.expression(GREEN_EXPR).select(GREEN);
  return image.addBands(green);
};


var COLLECTION = 'NOAA/GOES/17/MCMIPM';

// Select a subset of the collection, correct the values, and add a green band.
var START = ee.Date('2020-09-09T21:03:00');
var END = START.advance(10, 'minutes');
var collection = ee.ImageCollection(COLLECTION)
  .filterDate(START, END)
  .map(applyScaleAndOffset)
  .map(addGreenBand);

// Separates the two domains.
var domain1_col = collection.filter('domain == 1');
var domain2_col = collection.filter('domain == 2');

// Note that there are 20 assets, 10 in each domain.
var size = ee.String('sizes: collection = ').cat(collection.size());
var size1 = ee.String('domain1 = ').cat(domain1_col.size());
var size2 = ee.String('domain2 = ').cat(domain2_col.size());
print(size.cat('  →  ').cat(size1).cat(' and ').cat(size2));

// Visualization parameters.
var goesRgbViz = { bands: [RED, GREEN, BLUE], min: 0.0, max: 0.38, gamma: 1.3 };

// Displays a sample image from domain 1 and 2.
Map.addLayer(domain1_col.first(), goesRgbViz, 'Domain 1');
Map.addLayer(domain2_col.first(), goesRgbViz, 'Domain 2');

Map.setCenter(-133, 50, 3);