Download hourly relative humidity using GLDAS using Google Earth Engine

Question

Does anyone know how I can download hourly GLDAS relative humidity (%) using Google Earth Engine? The only output that I am able to get is specific humidity at a specific location, and am having trouble converting this. Is there a way of just obtaining RH straight from GLDAS?

Answer 1

If I understand this post correctly, it could be approximated like this:

var image = ee.ImageCollection('NASA/GLDAS/V20/NOAH/G025/T3H').first()

// https://earthscience.stackexchange.com/a/2361
var relativeHumidity = image.expression(
  '0.263 * p * q * (exp(17.67 * (T - T0) / (T - 29.65))) ** -1', {
    T: image.select('Tair_f_inst'),
    T0: 273.16,
    p: image.select('Psurf_f_inst'),
    q: image.select('Qair_f_inst')
  }
).float()

Map.addLayer(relativeHumidity, {min: 0, max: 100}, 'relativeHumidity')

https://code.earthengine.google.com/cdc1f107bfc53595b6ac7d3ce2b09a55

It get some values > 100, but maybe that's error from the approximation? At least this could give you a starting point.