Met Quiz 3

• Virga is wisps or streaks of hydrometeors falling out of a cloud but evaporating or sublimating before reaching the earth's surface as precipitation
• A mixed cloud is a region of the cloud where ice crystals and supercooled water droplets can coexist. Temperatures are colder than the melting point 0°C and warmer than ‑36°C
• A glaciated cloud is a region of the cloud where only ice crystals exist. This typically occurs in the upper troposphere where temperatures are below -36°C. Spontaneous freezing occurs at temperatures below -36°C.
• The three important factors in the production of raindrops is cloud liquid water content, cloud thickness, and updraft intensity
• In a warm cloud, cloud droplets grow to a raindrop size within approximately a half hour due to the collision/coalescence process.
• The ice-crystal growth process based on ice crystals growing faster and larger than supercooled drops makes the precipitation process more efficient
• A falling raindrop partially flattens itself due to form drag (dynamic pressures about drop deforms the drop)
• A continuous and steady precipitation of small droplets from stratus clouds is called drizzle
• A particle consisting of a homogeneous conglomeration of ice crystals and supercooled drops (accretion process) is called graupel or a snow pellet
• Precipitation in the form of frozen raindrops reaching the ground is called sleet.
• Sleet requires a deep surface layer of freezing air with a melting layer directly above
• Freezing rain are rain drops freezing upon impact on the ground or objects
• A common geometric shape of an ice crystal is hexagonal
• An observation used to measure the intensity of falling snow (heavy, moderate or light snow) is based on visibility.
• A snow shower is a sudden brief fall of snow from cumuliform clouds
• A snow squall a heavy snow shower
• Hail can form in cumulonimbus clouds having strong to moderate updrafts and large supercooled liquid water contents (large cloud-drop sizes). The ice particle is suspended for many minutes in the strong updraft growing though accretion to large sizes
• Conventional radar gathers information about precipitation in clouds by measuring the amount of transmitted radiation scattered back by precipitation particles.
• A hook-shaped or comma shape echo on a conventional radar screen often indicates the possible presence of a tornado-producing thunderstorm
• The Doppler radar gathers information about the radial movement of precipitation particles towards and away from the radar.
• On a Doppler radar screen, a tornado might appear as a region of rapidly changing radial wind speeds.
• Isobars are lines on a weather map that connect places of equal pressure
• An instrument used to measure air pressure is called a barometer
• A mercury barometer showing the height level of mercury rising in time means air pressure is increasing or rising in time.
• A mercury barometer showing the height level of mercury falling in time means air pressure is decreasing or falling in time.
• The vertical component of the pressure gradient force is nearly in balance with gravitational force. This is why the pressure can be considered equivalent to the weight of the air above.
• The atmospheric pressure value at any location can be directly related to the weight of the air from above
• The height of a pressure level in the upper and middle troposphere over the tropics is typically higher than over the Polar Regions because air is overall less dense and distributed more in the vertical over the tropics than over the Polar Regions
• An object or air parcel with a force acting in the same direction of its motion will only speed up.
• An object or air parcel with a force acting in the opposite direction of its motion will only slow down.
• An object or air parcel with a force acting perpendicular (right angles) to its motion will only change direction.
• The pressure gradient force will move air from high to low pressure
• The horizontal component of the pressure gradient force is responsible for generating wind (Air initially at rest can speed up due to this force)
• The closer the spacing of isobars the stronger the pressure gradient force
• The Coriolis force exists because we are viewing motions in an accelerating or rotating reference frame
• The Coriolis force can only change the direction of a moving air parcel
• The Coriolis force in the northern hemisphere deflects to the right of motion
• The boundary layer represents the friction layer near the earth’s surface
• The layer of air from the earth's surface up to about 1.5 km feels the earth's rough surface through frictional effects and is called the boundary layer
• No wind means no Coriolis or friction force since they are dependent on wind speed