Drought Monitoring with MODIS NDVI and DeepSeek

// Define the region of interest (Rif Mountains and Middle Atlas)
var roi = ee.FeatureCollection('users/yourusername/Rif_MiddleAtlas'); // Replace with your asset ID

// Define the date range
var startDate = '2020-01-01';
var endDate = '2023-12-31';

// Load the MODIS NDVI dataset
var modis = ee.ImageCollection('MODIS/061/MOD13A1')
  .filterDate(startDate, endDate)
  .filterBounds(roi);

// Function to mask clouds (example, requires adaptation to MODIS QA)
var maskClouds = function(image) {
  return image.updateMask(image.select('NDVI').gt(-10000)); //Simple mask assuming NDVI values below -10000 are invalid.
};

// Apply cloud masking
var modisMasked = modis.map(maskClouds);

// Function to calculate mean NDVI for each image and year
var calculateMeanNDVI = function(year) {
  var start = ee.Date.fromYMD(year, 1, 1);
  var end = ee.Date.fromYMD(year, 12, 31);
  var annualNDVI = modisMasked.filterDate(start, end).select('NDVI');
  var meanNDVI = annualNDVI.mean().multiply(0.0001); // Scale factor for MODIS NDVI
  return meanNDVI.reduceRegion({
    reducer: ee.Reducer.mean(),
    geometry: roi,
    scale: 250,
    maxPixels: 1e9
  }).set('year', year);
};

// Generate a list of years
var years = ee.List.sequence(2020, 2023);

// Map the function over the years
var annualNDVIValues = years.map(calculateMeanNDVI);

// Print the results
print(annualNDVIValues);

// Convert the results to a FeatureCollection
var annualNDVICollection = ee.FeatureCollection(annualNDVIValues);

// Export the table to Google Drive
Export.table.toDrive({
  collection: annualNDVICollection,
  description: 'MODIS_NDVI_Annual_Means',
  fileFormat: 'CSV'
});