q SAT = saturation specific humidity

Temp q sat Temp q sat 5 C 5.6 g/kg 25 C 20 g/kg 10 C 7.7 g/kg 30 C 28 g/kg 15 C 11 g/kg 40 C 47 g/kg 20 C 15 g/kg 50 C 80 g/kg @ sea level pressure q SAT = saturation specific humidity SATURATION: Represents the maximum amount of water vapor that can exist in air for a given temperature and pressure.

T=20 C q sat = 15 g/kg q = 7.5 g/kg RH = 50%

Cool to 10 C T=20 C q sat = 15 g/kg q = 7.5 g/kg RH = 50% T=10 C q sat = 7.7 g/kg q = 7.5 g/kg RH = 97%

NOW LET S COOL THE AIR EVEN FURTHER: Cool to 9.5 C T=20 C q sat = 15 g/kg q = 7.5 g/kg RH = 50% T=9.5 C q sat = 7.5 g/kg q = 7.5 g/kg

NOW LET S COOL THE AIR EVEN FURTHER: Cool to 9.5 C T=20 C q sat = 15 g/kg q = 7.5 g/kg RH = 50% T=9.5 C q sat = 7.5 g/kg q = 7.5 g/kg RH = 100%

NOW LET S COOL THE AIR EVEN FURTHER: Cool to 9.5 C T=20 C q SAT = 15 g/kg q = 7.5 g/kg RH = 50% T=9.5 C q sat = 7.5 g/kg q = 7.5 g/kg RH = 100% T DEW = 9.5 C Dew Point Temperature (T DEW ): Temperature to which air must be cooled to reach saturation. When air is at T DEW, the RH=100%

WHAT IF WE COOL THE AIR BELOW T DEW : Cool to 9.5 C Cool to 0 C T=20 C q sat = 15 g/kg q = 7.5 g/kg RH = 50% T=9.5 C q sat = 7.5 g/kg q = 7.5 g/kg RH = 100% T=0 C q sat = 3.5 g/kg q = 3.5 g/kg RH = 100%

WHAT IF WE COOL THE AIR BELOW T DEW : Cool to 9.5 C Cool to 0 C 4 g liquid water for each kg air T=20 C q sat = 15 g/kg q = 7.5 g/kg RH = 50% T=9.5 C q sat = 7.5 g/kg q = 7.5 g/kg RH = 100% T=0 C q sat = 3.5 g/kg q = 3.5 g/kg RH = 100%

Clicker Question Set Clicker Frequency to BB Air Dew Point City Temperature Temperature City A 95 F 75 F City B 50 F 42 F City C 30 F 21 F City D 10 F 10 F Which city has the highest relative humidity? (A) City A (B) City B (C) City C (D) City D

Pacific Ocean San Diego Water Temp = 60 F New Orleans Water Temp = 80 F Gulf of Mexico

San Diego Water Temp = 60 F Pacific Ocean New Orleans Water Temp = 80 F Gulf of Mexico

San Diego Water Temp = 60 F Pacific Ocean New Orleans Water Temp = 80 F Gulf of Mexico AT BOTH LOCATIONS SAN DIEGO NEW ORLEANS During day, land warms to 85 F but ocean temp does not change

San Diego Water Temp = 60 F Pacific Ocean New Orleans Water Temp = 80 F Gulf of Mexico AT BOTH LOCATIONS SAN DIEGO NEW ORLEANS During day, land warms to 85 F T water = 60 F but ocean temp does not change T land = 85 F

San Diego Water Temp = 60 F Pacific Ocean New Orleans Water Temp = 80 F Gulf of Mexico AT BOTH LOCATIONS SAN DIEGO NEW ORLEANS During day, land warms to 85 F T water = 60 F T water = 80 F but ocean temp does not change T land = 85 F T land = 85 F

San Diego Water Temp = 60 F Pacific Ocean New Orleans Water Temp = 80 F Gulf of Mexico AT BOTH LOCATIONS SAN DIEGO NEW ORLEANS During day, land warms to 85 F T water = 60 F T water = 80 F but ocean temp does not change T land = 85 F T land = 85 F Air over water near saturation RH = 100% RH = 100%

San Diego Water Temp = 60 F Pacific Ocean New Orleans Water Temp = 80 F Gulf of Mexico AT BOTH LOCATIONS SAN DIEGO NEW ORLEANS During day, land warms to 85 F T water = 60 F T water = 80 F but ocean temp does not change T land = 85 F T land = 85 F Air over water near saturation RH = 100% RH = 100% @ 60 F, q sat =11 g/kg so, q=11 g/kg

San Diego Water Temp = 60 F Pacific Ocean New Orleans Water Temp = 80 F Gulf of Mexico AT BOTH LOCATIONS SAN DIEGO NEW ORLEANS During day, land warms to 85 F T water = 60 F T water = 80 F but ocean temp does not change T land = 85 F T land = 85 F Air over water near saturation RH = 100% RH = 100% @ 60 F, q sat =11 g/kg @80 F, q sat =22 g/kg so, q=11 g/kg so, q=22 g/kg

San Diego Water Temp = 60 F Pacific Ocean New Orleans Water Temp = 80 F Gulf of Mexico AT BOTH LOCATIONS SAN DIEGO NEW ORLEANS During day, land warms to 85 F T water = 60 F T water = 80 F but ocean temp does not change T land = 85 F T land = 85 F Air over water near saturation RH = 100% RH = 100% @ 60 F, q sat =11 g/kg @80 F, q sat =22 g/kg so, q=11 g/kg so, q=22 g/kg Ocean air moves inland and warms to 85 F As air moves inland, q stays the same. What is RH? @ 85 F, qsat = 25.6 g/kg

San Diego Water Temp = 60 F Pacific Ocean New Orleans Water Temp = 80 F Gulf of Mexico AT BOTH LOCATIONS SAN DIEGO NEW ORLEANS During day, land warms to 85 F T water = 60 F T water = 80 F but ocean temp does not change T land = 85 F T land = 85 F Air over water near saturation RH = 100% RH = 100% @ 60 F, q sat =11 g/kg @80 F, q sat =22 g/kg so, q=11 g/kg so, q=22 g/kg Ocean air moves inland and RH = (q/q sat )x100% warms to 85 F RH = (11/25.6)x100% As air moves inland, q stays RH = 43% the same. What is RH? @ 85 F, qsat = 25.6 g/kg

San Diego Water Temp = 60 F Pacific Ocean New Orleans Water Temp = 80 F Gulf of Mexico AT BOTH LOCATIONS SAN DIEGO NEW ORLEANS During day, land warms to 85 F T water = 60 F T water = 80 F but ocean temp does not change T land = 85 F T land = 85 F Air over water near saturation RH = 100% RH = 100% @ 60 F, q sat =11 g/kg @80 F, q sat =22 g/kg so, q=11 g/kg so, q=22 g/kg Ocean air moves inland and RH = (q/q sat )x100% RH = (q/q sat )x100% warms to 85 F RH = (11/25.6)x100% RH = (22/25.6)x100% As air moves inland, q stays RH = 43% RH = 86% the same. What is RH? @ 85 F, qsat = 25.6 g/kg

Clicker Question Set Clicker Frequency to BB During the night a cloud moves overhead. In general, how does this impact the surface (ground) temperature? (A) Has no impact on the surface temperature (B) The surface temperature will increase (C) The surface temperature will decrease

Clicker Question Set Clicker Frequency to BB If the night is cloudy (not fog), will the clouds help produce radiation fog? (A) Yes (B) No

Radiation Fog in the San Joaquin Valley January 2004 S.F. SNOW FOG L.A.