What is an air parcel in meteorology?
A small volume of air that moves through the atmosphere adiabatically without mixing or exchanging heat/moisture with its surroundings.
What does “adiabatic” mean?
A process where no heat is exchanged between an air parcel and its environment.
What is the dry adiabatic lapse rate?
The rate at which unsaturated air cools when it rises — 10°C per kilometer.
What is the moist adiabatic lapse rate?
The rate at which saturated air cools as it rises — typically 6–8°C per kilometer
Why is the moist adiabatic lapse rate smaller than the dry one?
Because condensation releases latent heat, which offsets some of the cooling.
What is the Lifting Condensation Level (LCL)?
The height at which a rising air parcel cools to its dewpoint and condensation begins (cloud base forms).
How can you estimate the LCL (in km)?
(T_surface – T_dewpoint) ÷ 10°C per km.
What are Cloud Condensation Nuclei (CCN)?
Tiny atmospheric particles (like dust or salt) that provide surfaces for water vapor to condense upon.
What are Ice-Nucleating Particles (INP)?
Particles that promote ice crystal formation in cold clouds.
What are the four main causes of lift that form clouds?
1) Fronts, 2) Topography, 3) Convective thermals, 4) Surface boundaries
How do warm fronts cause clouds?
Warm air slides gently over cooler air, forming layered clouds — from stratus and nimbostratus to cirrostratus and cirrus.
What weather often precedes a warm front?
High clouds (cirrus) followed by thickening and lowering cloud layers, steady rain, and temperature increase after the front passes.
How do cold fronts cause clouds?
Cold air pushes under warm air, forcing it to rise steeply — producing cumulus or cumulonimbus and possibly showers or storms.
What is a rain shadow?
A dry region on the leeward side of mountains caused by air descending, warming, and drying after rising and condensing on the windward side.
Describe the temperature changes of air moving over a mountain.
Cools at 10°C/km (dry) or 5°C/km (moist) on ascent, warms at 10°C/km on descent → ends up warmer and drier.
What is the planetary boundary layer (PBL)?
The layer of the atmosphere directly influenced by the Earth’s surface — heating, cooling, and friction effects dominate.
What is a convective boundary layer?
A daytime boundary layer where thermals rise and mix air due to surface heating, often forming fair-weather cumulus.
How do horizontal convective rolls form?
Wind shear in the boundary layer organizes thermals into parallel rolls, producing lines of stratocumulus clouds (cloud streets).
What is a sea breeze and when does it occur?
A daytime onshore wind caused by land heating faster than the sea, creating pressure differences that drive air inland.
What is a land breeze and when does it occur?
A nighttime offshore wind caused by land cooling faster than the sea, reversing the pressure gradient.
What are surface boundaries in meteorology?
Zones of air convergence near the surface (like fronts or sea breezes) that cause air to rise and clouds to form.
What is an outflow boundary?
A cool, dense air mass spreading out from a thunderstorm that can trigger new convection when it lifts warmer surrounding air.
What is the environmental lapse rate?
The actual rate at which temperature decreases with height in the surrounding atmosphere.
What happens when environmental lapse rate > dry adiabatic lapse rate?
The atmosphere is unstable — rising air continues to rise.
