For absolutely stable air both dry and moist lapse rates are higher than the ELP e.g. DALR = 100C/1000m MALR= 60C/1000m ELR = 40C/1000   For absolutely unstable air both moist and dry lapse rates are lower than the ELP e.g MALR =60C/1000m DALR=100C/1000m ELR= 110C/1000m For Conditionally unstable air, the ELP lies between the moist and dry lapse rates e.g. DALR=100C/1000m ELR = 70C/1000m MALR = 60C/1000m

SO WHAT CAN CAUSE THE AIR’S STABILITY TO CHANGE? Changing the environmental lapse rate will potentially change stability. This can happen by: 1. Cooling of the air aloft (a) winds bringing in colder air (cold air advection) (b) clouds or air emitting infrared radiation to space (radiational cooling) 2. Warming of the surface air (a) daytime solar heating of the surface (b) winds bringing in warm air (warm advection) (c) air moving over a warm surface

Environmental lapse rate 1. Cooling of the air aloft (a) winds bringing in colder air (cold air advection) (b) clouds or air emitting infrared radiation to space (radiational cooling) 2. The warming of the surface air (a) daytime solar heating of the surface (b) winds bringing in warm air (warm advection) (c) air moving over a warm surface

HOW HIGH THE MOON? I MEAN HOW HIGH THE CLOUD?

The predominate cloud type for High clouds. Each type’s symbol is found in the table.

The predominate cloud type for medium clouds. Each type’s Symbol is found in the table.

The predominate cloud type low clouds The predominate cloud type low clouds. Each type’s symbol is found in the table.

1mμ =one millionth of a meter or one micrometer

1mμ =one millionth of a meter or one micrometer

Water vapor pressure higher over liquid than ice

THE ICE CRYSTAL PROCESS Or BERGERON PROCESS The greater number of water Molecules around the liquid droplet causes molecules to diffuse from the liquid droplet toward the ice crystal. The ice crystal absorbs the water vapor and grows larger, while the water droplet grows smaller.

SOME TERMS Condensation nuclei = 0.2 μm (more over the land than ocean) Cloud Droplet = about 20 μm Typical Raindrop = about 2000 μm   Collisions/coalescence = collisions between cloud droplets makes bigger droplets Ice nuclei: needed to commence the freezing process at sub 0 temperatures Deposition nuclei: nuclei that allow water vapor to deposit on their surfaces Freezing nuclei: promote freezing of super cooled droplets by way of a liquid phase Accretion: Ice crystals collide with supercool droplets – forms graupel Aggregation: ice crystals collide and stick together – results in snowflake Rime: the deposit of ice crystals formed by the freezing of supercooled fog or cloud droplets on objects whose surface temperature is below freezing. This can happen on trees, like pine where the needles act as freezing nuclei

NOTE: This is a chart from the U.S. Weather Service which does not use the metric system so the measurement is in “inches” rather than “centimeters”

* US Weather Service does not use the metric system, so the distance is in miles.

HAILSTONE PHOTGRAPHED WITH REGULAR LIGHT SHOWING LAYERS HAILSTONE PHOTGRAPHED WITH POLARIZED LIGHT SHOWING LAYERS

NOTE THE WEATHER SYMBOL CODES FOR THE PRECIPITATION TYPES

A MORE COMPLETE SET OF SYMBOLS FOR PRECIPITATION