2.0 Precipitation Flashcards
general term for all form of moisture originating from clouds and falling to the ground.
precipitation
consists of waterdrops under 0.02 in diameter and intensity is usually less than 0.04 in/br
drizzle
consists of drop usually greater than 0.02 in diameter. 0.25 in upper limit of raindrop size.
rain
is the ice coating formed when drizzle or rain freezes as it comes in contact with cold objects at the ground.
glaze
frozen raindrops that fall as small globose, ice pellets with a diameter of 5mm or less
sleet
precipitation in the form of ice crystals resulting from sublimation
snow
made up of a number of ice crystals fused together
snowflake
precipitation in the form of balls or lumps of ice over 0.2 in diameter.
hail
types of precipitation
convective precipitation
cyclonic precipitation
orographic precipitation
factors determining precipitation
climate
geography
ocean surface
forms of precipitation
liquid
solid
types of liquid precipitation
rainfall
drizzle
types of solid precipitation
snow
hail
sleet
caused by natural rising of warmer lighter air at colder denser surrounding
covective precipitation
results from lifting of air converging into a low-pressure area or cyclone
cyclonic precipitation
occurs when heavily moisture laden air stops due to topographic conditions (mountains)
orographic precipitation
weather system for precipitation
atmospheric front
cyclone
anticyclones
interface b/w two distinct air masses
front (atmospheric front)
large low pressure region with circular wind motion
cyclone
regions of high pressure, usually of large areal extent
anticyclones
amount of precipitation, in the form of rain (water from clouds), that descends onto the surface of Earth, whether it is on land or water.
Rainfall
falling snowflakes or snow crystals or also the accumulation of snow during a specified period of time.
Snowfall
The formation of snow requires at least 3 conditions
1) atmospheric moisture and
2) mechanisms to convert this water vapor into precipitation (i.e. vertical motion of air),
3) temperatures (T) below 0oC.
instruments in measuring snowfall
- 4” Diameter CoCoRaHS Rain Gauge(Outer Cylinder for winter weather)
- Snow Measuring Board(16”x16” piece of ½ or ¾ plywood painted white)
- Snow ruler or Yardstick(Measure in 10th`s of an inch)
- CoCoRaHS “Snow-Swatter” and Spatula(Helps with taking core samples)
simplest averaging method but can only be relied on small, flat areas
Arithmetic mean method
a graphical technique that considers the weights of each rain gages based on the relative measurements of their respective area coverage. done by connecting the rain gages with a line and drawing a perpendicular bisector
Thiessen polygon method
graphical technique that involves drawing isohyets or contours that are equal to the respective rainfall gage over an area based on point measurements. most technical method as it also takes the topography of the area into consideration, but doing so makes it the most accurate method among the three basic averaging methods
Isohyetal method
methods in estimating rainfall average
arithmetic mean method
thiessen polygon method
isohyetal method
methods in estimation of missing data
arithmetic mean method
normal ratio method
defined as a change in the amount of precipitation that falls naturally in a certain location
Variation of precipitation
occur seasonally or within a single storm, and distributions vary with storm type, intensity, duration, and time of year
Time variations of precipitation
In general, precipitation is heaviest at the equator and decreases with increasing latitude.
True
The main source of moisture for precipitation is evaporation from the surface of large bodies of water. Therefore, precipitation tends to be heavier near coastlines.
True
Precipitation in the form of ice crystals, mainly of intricately branched, hexagonal form and often agglomerated into snowflakes, formed directly from the freezing of the water vapor in the air.
Snow/Snowfall
______________ occurs through a process called the ______________, which involves the interplay between temperature, humidity, and the presence of ice nuclei
Snowfall formation, Bergeron-Findeisen process
measureing instrument used to measure areas, usually irregular regions on a map
planimeter
used when the annual precipitation at each index stations is less than or more than 10% of that for the station with the missing record
normal ratio method
used when the normal annual precipitation at each of the index stations is within 10% of that for the station with the missing record
arithmetic mean method
step-by-step explanation of howsnowflakes are formed
atmosphere
supercooling
ice nuclei
supersaturation
deposition
vapor diffusion
crystal growth
aggregation
precipitation
Snowfall begins in the Earth’s atmosphere, where conditions are crucial for the formation of snowflakes. The temperature and humidity levels play significant roles in determining the type of precipitation that will form.
atmosphere
When the temperature in the atmosphere is below freezing (0 degrees Celsius or 32 degrees Fahrenheit), water vapor can remain in a liquid state even below its freezing point. This phenomenon is known as _______
supercooling
For snowflakes to form, _______< are required. These are microscopic particles, such as dust, pollen, or other solid particles, which can act as a surface for water vapor to freeze upon. Ice nuclei provide a nucleus for the formation of ice crystals.
ice nuclei
occurs when the air is holding more moisture than it can actually accommodate at a given temperature. In supercooled conditions, water vapor can exist in a supersaturated state without immediately condensing into liquid droplets.
Supersaturation
When supersaturated air encounters an ice nucleus, water vapor molecules start to deposit directly onto the surface of the ice nucleus, bypassing the liquid phase. This process is called ________, where water vapor changes directly into solid ice crystals without becoming a liquid first
deposition
As the ice crystals grow, they start to consume surrounding water vapor through a process called __________. The water molecules diffuse from regions of higher concentration (surrounding air) to regions of lower concentration (ice crystal surface) and attach to the growing ice crystal.
vapor diffusion
As water molecules continue to deposit onto the ice crystal, it grows into a hexagonal structure due to the arrangement of water molecules in a hexagonal lattice. The specific growth pattern of the ice crystal determines the unique shape of each snowflake.
crystal growth
As the ice crystals fall through the atmosphere, they may collide with other ice crystals, causing them to stick together. This process is known as aggregation, where smaller ice crystals combine to form larger snowflakes. The resulting snowflake can have complex and intricate structures
aggregation
Once the snowflake becomes too heavy for the updrafts in the atmosphere to support, it falls to the ground as snow. The size, shape, and density of the snowflake determine whether it falls as light, fluffy snow or heavy, wet snow.
precipitation
basic shapes of snow crystals/snow flakes
plate
column
dendrite
dimensions of snow crystals
very fine <_0.2
fine 0.2 - 0.5
medium 0.5 - 1.0
coarse 1.0 - 2.0
very coarse 2.0 - 5.0
extreme >_5
snowfall formation
water vapor + nucleus + T<0°C + saturation
nucleation
ice crystal
snow crystal
snowfall key statistics
average snowfall
below-average snowfall
avove-average snowfall
snowfall variability
low variability
high variability
snowfall frequency
increased frequency
decreased frequency
snowfall intensity
heavy snowfall
light snowfall
indicates the typical amount of snow that falls in a given period, such as annually or monthly. It provides a baseline understanding of the expected snowfall in a region
Average Snowfall
indicate drier or milder conditions than usual. It could impact winter activities, water resources, and ecosystems dependent on snowpack.
Below-average snowfall
suggests wetter or colder conditions. It can affect transportation, infrastructure, and pose challenges for snow removal efforts
Above-average snowfall
helps identify the range or spread of snowfall amounts over time.
Snowfall Variability
suggests relatively consistent snowfall patterns from year to year. This can aid in planning and managing snow-related activities.
Low variability
indicates significant fluctuations in snowfall amounts. It may result in unpredictable winter conditions and can impact agriculture, tourism, and other sectors sensitive to snowfall
High variability
measures how often snowfall events occur within a specific timeframe, such as the number of snow days per month or year.
Snowfall Frequency
indicate a colder climate or more frequent winter storms. This can have implications for winter sports, transportation disruptions, and increased snow accumulation.
Increased frequency
suggest changing climate patterns or milder winters. It may affect winter tourism, water resources, and ecological systems adapted to snowy conditions
Decreased frequency
refers to the rate at which snow accumulates during a snowfall event, often measured in inches per hour.
Snowfall Intensity
can lead to rapid snow accumulation, blizzard conditions, and potential disruptions to daily life, including transportation and power outages
Heavy snowfall
typically accumulates at a slower rate and may have less immediate impact, but it can still cause slippery conditions and require snow removal efforts.
Light snowfall
key factors that influences the snow cover distribution
climate
temperature
precipitaion
topography
latitude
seasonal variations
climate change
three spatial scales
macroscale
mesoscale
microscale
is important for various applications, such as snowpack monitoring, avalanche forecasting, and winter recreation planning
open environment
is influenced by several factors, including the density and type of vegetation, wind patterns, topography, and snowfall characteristics
forested environment
crucial for various disciplines, including agriculture, forestry, and ecology. It helps inform management practices, climate change assessments, and conservation efforts, considering the effects of changing snow patterns on plant communities and ecosystems.
effect of vegetation
snow distribution refers to small variations in snow depth and cover within a local area
microscale
concerned with the processes and phenomena that occur at this intermediate scale
mesoscale
the focus is on understanding the large-scale weather systems and atmospheric patterns that influence snowfall and snow accumulation over large regions
macroscale
key factors involved in blowing snow
loose snow
wind
wind erosion
saltation and suspension
snowdrifts and snowbanks
reduced visibility
blowing snow factors
shear velocity
threshold wind speed
transport rates (satltation, suspension, surface creep or creep flow)
refers to the phenomenon where loose snow on the ground is lifted into the air and carried by strong winds, creating a swirling cloud of snow particles
Blowing snow
occurs when the snow on the ground is loose and dry.
loose snow
responsible for lifting the loose snow particles from the ground and carrying them into the air
wind
As the wind flows over the surface, it creates turbulence and eddies that lift the loose snow particles
wind erosion
In _________ , the wind carries larger snow particles, causing them to bounce and roll along the ground, creating a “skipping” motion. In _________, smaller snow particles become entrained in the air and are transported by the wind, forming a visible cloud of blowing snow
saltation and suspension
refers to the accumulated layers of snow on the ground, typically in mountainous or winter environments. It is formed by successive snowfall events and can undergo various transformations due to processes such as compaction, settling, melting, and refreezing.
snowpack
key aspects of snowpack
snow accumulation
snow density and layers
snow compaction
snow settlement
snow metamorphism
snowmet and refreezing
snow water equivalent (SWE)
snowpack characteristics
grain shape
grain size
liquid water content
temperature
snow water equivalent (snow depth × (snow density / water density))
