The primary Advanced Tiros-N Operational Vertical Sounder (ATOVS) sounding products include temperature, which is defined at 40 levels (surface to 0.1 mb), and moisture, which is defined at 15 levels (surface to 200 mb). Secondary derived products include layer mean virtual temperature (derived from geopotential thickness), layer precipitable water (PW), and total precipitable water (TPW). The average horizontal resolution for this product group is currently 40 km, but will increase to 16 km for the moisture products as Advanced Microwave Sounding Unit (AMSU)-B observations are integrated into ATOVS(planned for spring 2000).