Question

Is it possible the dry bulb, wet bulb and dew point temperatures for atmospheric air to be the same?

Answer 1

Yes...!! It's possible.

Dry bulb temperature, wet bulb temperature and dew point temperature for atmospheric air is same when the relative humidity is 100 percent.

NOTE:

• 
  T Pr Isothermal Saturation DBT adiabatic Saturation WBT DPT Isobaric Saturation. 7b
  
• Dew point temperature (DPT) is the saturation temperature corresponding to pressure Pv (i.e, saturation achieved isobarically)
• Wet bulb temperature (WBT) is the saturation temperature corresponding to pressure Pv' (i.e, saturation achieved adiabatically)
• Dry bulb temperature (DBT) is the saturation temperature corresponding to pressure Pvs (i.e, saturation achieved isothermally)

We know that, for unsaturated air, DBT > WBT> DPT.

But, for saturated air, DBT=WBT=DPT

Saturated air means it's relative humidity is 100 percent.

Hope this will helps....!!!