How to extract values from metadata in sentinel 2 images

Question

I am trying to composite an image with the mean value of the METADATA layer "CLOUDY_PIXEL_PERCENTAGE" for every pixel.

My goal is to do this for monthly mean values, but I can't find the way to simply extract the values of this metadata expressed by a percentage (which I know is the format of this layer)

Does anybody know how to?

Answer 1

On EARTH ENGINE, if u want to check a pixel for cloud, you can use the QA60 band of the Sentinel-2 image.

The QA60 band is meant to be read in binary form. In its binary form, the 10th bit( 0 or 1 ) represents whether the pixel has cloud or not, whereas the 11th bit ( 0 or 1 ) represents whether the pixel has cirrus clouds or not.

The below code will return you a raster image of the same footprint as your original image with pixel values 1 or 0, where 1 denotes that the pixel contains cloud and 0 otherwise.

function cloudPixels(image) {
  var qa = image.select('QA60');
  var cloudBitMask = Math.pow(2, 10);
  var cirrusBitMask = Math.pow(2, 11);   //for cirrus clouds
  var cloudMask = qa.bitwiseAnd(cloudBitMask);
  var cirrusMask = qa.bitwiseAnd(cirrusBitMask);    //return this variable to get cirrus cloud pixels
  return cloudMask;
}