301 Flashcards
4 factors that control the evolution of clouds
Water Vapour
condensation and ice nuclei
stability
lift
Natural Condensation
Process by which molecules of water vapour are brought together in sufficient numbers to form liquid water
Hygroscopic nuclei
Condensation nuclei which do not require saturation to be impregnated with water
- water soluble substances -sea salt
- products of combustion
Dimensions of hygroscopic nuclei
Aitken nuclei -less than a tenth of a micrometer
Large Nuclei -from 0.1 up to 1 micrometer
Giant nuclei - greater than 1 micrometer
Saturation mixing ratio
the theoretical maximum amount of water vapour that the air at a specific temperature and pressure can hold
4 types of vertical motion that lead to the formation of clouds
Convective lift
Mechanical turbulence
Orographic lift
Large scale lift
2 main processes that initiate convection in the atmosphere
Daytime Heating
Cold Air advection
The intensity and height of mechanical turbulence relies on what three things
the roughness of the underlying surface
the strength of the wind
the instability of the air
5 reasons clouds are important in meteorology
Forms of weather Precipitation formation Effects on the heat budget Atmospheric processes Actual conditions
2 main processes that cloud is produced in the atmosphere
Cooling - adiabatic cooling
-diabetic cooling
Evaporation - addition of moisture to the atmosphere by evaporation into cooler air
3 types of diabatic cooling
Radiation
Advection
Mixing
5 synoptic situations where large scale dynamic lift produce clouds and weather
In the vicinity of low pressure centres and troughs Regions of baroclinic development Warm fronts and trowals Upper short wave troughs Jet stream maximums
6 broad scale processes used to assess presence of boundary layer cloud and weather
Low level convergence Upslope/onshore flows Surface winds (>15kts) Large area with moist surface conditions Evaporation of precipitation cooling by advection or convection
Orographic lift: the extent and rate of ascent of air undergoing orographic lift depend on the:
Slope and height of terrain
the strength of the wind
Orographic lift:
The extent of the cloud that forms depends on:
the type of cloud depends on:
the moisture of the air
the stability of the air
The difference between radiation fog and advection fog
- development
- dissipation -radiation fog dissipates from the bottom up outside in.
- advection will persist until a change in wind speed or direction - advection fog is not fixed to a daily cycle.
2 ways a parcel of air is heated or cooled in an adiabatic process.
Through cooling of expansion and heating of contraction.
Through the the storage and release of latent heat.
What is the dominant process for cloud development in the mid to high latitudes
Large scale dynamic lift
Large scale upward vertical velocity is a result of:
A combination of low level convergence and high level divergence.
Usually in a baroclinic zone.
5 synoptic situations where large scale dynamic lift will often produce clouds and weather
In the vicinity to of low pressure centres and troughs. Regions of baroclinic development Warm fronts and trowals Upper short wave troughs Jet stream maximums
What is the main cause of cloud in the boundary layer
Low level convergence generating upward vertical motion
6 broad scale processes used to assess the presence of boundary layer clouds and precipitation
(Using surface analysis and short range surface prognosis)
Low level convergence Upslope/onshore flow Surface winds >15 it's Large area with moist surface conditions Evaporation of precipitation Cooling by advection/convection
Low level Convergence
position of fronts troughs and lows etc…that might produce low level convergence.
highs and troughs may indicate dissipation
upslope/onshore flows
significant geographic areas of upslope/downslope and onshore/offshore
