Calculating sigma in Google Earth Engine

Question

I'm trying to calculate this formula in GEE:

∑ U(U-5)^2 (u is wind speed greater than 5)

when I use (.add) in my code it just give me a pixels that are greater than 5 in both of them at the same but maybe in first image in one pixel we don't have wind greater than 5 but in other we have, I want one image that have all of them at the same time:

var Windspeed = ee.ImageCollection('NASA/GLDAS/V021/NOAH/G025/T3H')
.filter(ee.Filter.date('2020-01-01'))
.select('Wind_f_inst')
.mean();

var gt = Windspeed.gt(5);
var  u = Windspeed.mask(gt); 

var Windspeed1 = ee.ImageCollection('NASA/GLDAS/V021/NOAH/G025/T3H')
.filter(ee.Filter.date('2020-01-02'))
.select('Wind_f_inst')
.mean();

var gt1 = Windspeed1.gt(5);
var  u1 = Windspeed1.mask(gt1); 
  
var windt = u.add(u1)  



var WindVis = {
  min: 46.05683272577041,
  max: 101.32877871485076,
  palette: ['1303ff', '42fff6', 'f3ff40', 'ff5d0f'],
};


Map.centerObject(table);
Map.addLayer(
    windt.clip(table), WindVis,
    'U2');

Answer 1

I'm not sure I understood what you're asking, but I think you want to mask out pixels where both windspeeds are below 5.

var mask = Windspeed.gt(5).or(Windspeed1.gt(5))
var u = Windspeed.updateMask(mask)
var u1 = Windspeed1.updateMask(mask)
var windt = u.add(u1)

https://code.earthengine.google.com/7e51711467144c7479fa1302f2cf917f