TES HDO / H20 (Surface- 550 hPa)

HDO measurements tell us about ice cloud formation and evaporation. Delta-d is the measure of HDO depletion compared to standard mean sea water concentrations of HDO. Air at high latitudes is HDO depleted due to the presence of stratospheric air. This is the first map of HDO ever made. + click for a larger view

When cloud ice forms HDO is concentrated in the ice and the air is HDO depleted. If the ice falls out then air will have lower HDO. If the ice evaporates the HDO amounts in air increase.