HUMIDITY (3)

LIFTING CONDENSATION LEVEL - LCL
THE ALTITUDE TO WHICH AN AIR PARCEL WOULD NEED TO BE LIFTED FOR CONDENSATION TO OCCUR
VISIBLE EVIDENCE IS THE CLOUD BASE
OCCURS AT SATURATION/DEW POINT TEMPERATURE


DRY ADIABATIC LAPSE RATE (DALR)

TEMPERATURE DECREASE EXPERIENCED BY A RISING UNSATURATED PARCEL – ABOUT 1 DEGREE CELSIUS PER 100 METERS OR 10 DEGREES/1000 METERS
SINKING PARCELS WARM AT THE SAME RATE


DALR PROBLEM

  THE SURFACE TEMP IS 20 DEGREES C & THE DEW POINT IS 5 DEGREES C, HOW MANY METERS MUST THE AIR RISE TO REACH THE LCL?
ANSWER: 15 DEGREES X 100 METERS = 1500 METERS OR 1.5 KILOMETERS


WET ADIABATIC LAPSE RATE
RATE OF TEMPERATURE CHANGE FOR A RISING SATURATED PARCEL OF AIR
ON THE AVERAGE IT IS ABOUT 5 DEGREES C/ 1000 METERS


WALR PROBLEM
AT THE SURFACE THE TEMP IS 25 DEGREES C AND THE DEW POINT IS AT 15 C, WHAT WILL THE TEMP BE AT 4000 METERS ABOVE THE SURFACE?
ANSWER: 0 CELSIUS – [25 – (DALR = 10 DEGREES/1000 METERS) = 15] 15 – (WALR = 5 DEGREES/1000 METERS) = 15 {15 – 15 = 0}


EFFECTS OF VERTICAL MOVEMENT OF AIR
WHEN AIR RISES IT EXPANDS AND COOLS.  AS IT COOLS, ITS RELATIVE HUMIDITY GOES UP
WHEN AIR SINKS IT IS COMPRESSED AND WARMED.  AS IT WARMS ITS RELATIVE HUMIDITY(RH) GOES DOWN
 RATE DEPENDS ON THE AIR’S RH