ATSC 113 - Snow Sports Exam
Questions with Complete Answers
What is pressure at sea level? - Answer-Typically around 100.0 kPa or 1000 hPa
What is the next atmospheric level that meteorologists care about besides sea level? -
Answer-85.0 kPa is about 1500 m, and is about couple hundred meters above North
Shore mountains;
After that is 70.0 kPa, at around 3000 m
100 kpa is 0m, 90 kpa is 1000m
What is mid-mountain? - Answer-The middle of typical skiing elevation range
What is a pressure-level map? - Answer-A map that visualizes what the weather
condition looks like at a certain pressure surface (85.0 kpa is most common)
What happens to pressure as you get higher in atmosphere? - Answer-pressure
decreases
How are pressure level maps shown? - Answer-animated loops, starting with an
analysis map at the time the Numerical Weather Prediction (NWP) model was made.
- have black contours that show lines of constant temperature every 2C
What is an NWP? - Answer-
How are pressure-level maps plotted with wind? - Answer-They use wind barbs
They have a plain edge, that show where wind is coming from, an orientation of
direction (like an arrow)
Short line means 10 km/h winds, full lines are 20 km/h winds and dlags mean 100 km/h
winds
What are wind speeds on pressure-maps best thought of? - Answer-estimates of wind
speed in the "free atmosphere" (excluding the effects of friction from the surface) at that
elevation
What is high pressure associated with? - Answer-Light winds, especially near center of
high pressure systems and less guaranteed on the edge
When there is a _______ gradient winds will be light - Answer-Weak pressure gradient,
which means less difference between pressure (air flow that causes wind) (isobars are
further apart)
,What are scenarios where a high pressure system doesn't have light winds? - Answer-
When a high pressure system approaches from the west or a low pressure system
departs to the east/south east and create a string pressure gradient
Also outflow winds
What are low-level wind maps? - Answer-Indicate areas of light wind, at a surface level
(ie 85.0 kpa)
What are some uses for temperature forecasts? - Answer-What to wear appropriately
for skiing, whether precipitation will fall as rain/snow, and to identify fronts
At what rate do temperature contours change for? - Answer-A change for every 2C
What are the two steps of temperature forecasting in the mountains? - Answer-Vertically
adjust (or interpolate) the temp from a low-level pressure map (like 85.0 kPa) to the
elevation you are concerned about → gives the free-air temperature
Make adjustments to temperature based on heating/cooling that may be occurring at
ground surface.
What is interpolation? - Answer-The process of estimating the quantity in between
locations with known quantity
What is free-air temperature? - Answer-The temperature at a particular level of the
atmosphere (assuming no heating/cooling effects from the surface)
What are dry adiabatic conditions? - Answer-Conditions where temperature decreases
with a height increase with 10 deg C per 1000 m
When can we assume a dry adiabatic lapse rate? - Answer-when the modelled
atmosphere is not close to saturation (below 80% relative humidity) AND
(a) if the winds are moderate or strong (~40 km/h or greater) or
(b) in the daytime during the spring, or
(c) in some cases during the afternoon on sunny winter days.
When can we assume a wet adiabatic lapse rate? - Answer-When the atmosphere is
saturated (100% relative humidity), which causes the temperature to decrease more
slowly with height.
What are wet adiabatic conditions? - Answer-Under wet adiabatic conditions,
temperature decreases at a rate of approximately 6°C per 1000 m (6°C/km) in mild air,
but the rate of decrease varies with temperature
What are stable conditions? - Answer-when the lapse rate is more stable than the wet
adiabatic lapse rate, meaning that the temperature decreases very slowly with height, or
even increases with height (called inversion)
, When/where does inversion occur? - Answer-Inversions typically occur locally within
valleys in the overnight and morning period in the winter, and during Arctic air outbreaks
How do we find free-air temperature? - Answer-1. If RH > 80%, use wet-air tool, if less
than use dry-air tool
2. Start from correct pressure level (85 kpa, 70 kpa)
3. Move parallel to green lines to correct height
4. Look to orange line to see new temperature
What are sources of heating and cooling within the troposphere? - Answer-The initial
source of heating and cooling is the ground surface.
During daylight, the sun heats up the ground which in turn heats up the air next to the
surface
At night, especially with clear skies, the surface cools radiatively (loses heat energy),
with the largest amount of cooling right at the ground surface.
What are the factors that affect heating and cooling? - Answer-Sun angle, cloud cover,
wind speed
What is sun angle and how does it affect heating and cooling? - Answer-The angle at
which the sun's rays hit strike the earth's surface; some parts of the earth get more sun
(midlatitudes where sun is perpendicular) and some get less sun (higher/lower altitudes)
As winter has much less daylight hours and less intensity than spring, the heating
adjustement daytime temperature is small (0-3C), while for spring it can be big (4-10C)
At night, sun angle is not a factor as there is no solar radiation
What is cloud cover and how does it affect heating and cooling? - Answer-Cloud cover
reduces the incoming solar radiation hitting the ground, and so it reduces daytime
heating measurement
The actual amount depends on the fraction of cloud cover and heights of clouds, but
roughly partly cloudy skies = half the sun's energy makes to the surface
During the night, if there are no clouds the ground radiates the heat back into space.
If there are clouds, they absorb the energy and re-radiate it back to the earth, meaning
surface still stays somewhat warm
What is wind speed and how does it affect heating and cooling? - Answer-During the
day, wind shear can cause mechanical mixing, which brings cooler from just above the
surface right down to the surface, so that the mountain slope-air temperature is closer to
the free air temperature (higher wind speed → greater effect)
At night, wind shear turbulence mixes warmer air closer to surface, reducing the
radiative cooling effect (means once again mountain slope is closer to free air)
Questions with Complete Answers
What is pressure at sea level? - Answer-Typically around 100.0 kPa or 1000 hPa
What is the next atmospheric level that meteorologists care about besides sea level? -
Answer-85.0 kPa is about 1500 m, and is about couple hundred meters above North
Shore mountains;
After that is 70.0 kPa, at around 3000 m
100 kpa is 0m, 90 kpa is 1000m
What is mid-mountain? - Answer-The middle of typical skiing elevation range
What is a pressure-level map? - Answer-A map that visualizes what the weather
condition looks like at a certain pressure surface (85.0 kpa is most common)
What happens to pressure as you get higher in atmosphere? - Answer-pressure
decreases
How are pressure level maps shown? - Answer-animated loops, starting with an
analysis map at the time the Numerical Weather Prediction (NWP) model was made.
- have black contours that show lines of constant temperature every 2C
What is an NWP? - Answer-
How are pressure-level maps plotted with wind? - Answer-They use wind barbs
They have a plain edge, that show where wind is coming from, an orientation of
direction (like an arrow)
Short line means 10 km/h winds, full lines are 20 km/h winds and dlags mean 100 km/h
winds
What are wind speeds on pressure-maps best thought of? - Answer-estimates of wind
speed in the "free atmosphere" (excluding the effects of friction from the surface) at that
elevation
What is high pressure associated with? - Answer-Light winds, especially near center of
high pressure systems and less guaranteed on the edge
When there is a _______ gradient winds will be light - Answer-Weak pressure gradient,
which means less difference between pressure (air flow that causes wind) (isobars are
further apart)
,What are scenarios where a high pressure system doesn't have light winds? - Answer-
When a high pressure system approaches from the west or a low pressure system
departs to the east/south east and create a string pressure gradient
Also outflow winds
What are low-level wind maps? - Answer-Indicate areas of light wind, at a surface level
(ie 85.0 kpa)
What are some uses for temperature forecasts? - Answer-What to wear appropriately
for skiing, whether precipitation will fall as rain/snow, and to identify fronts
At what rate do temperature contours change for? - Answer-A change for every 2C
What are the two steps of temperature forecasting in the mountains? - Answer-Vertically
adjust (or interpolate) the temp from a low-level pressure map (like 85.0 kPa) to the
elevation you are concerned about → gives the free-air temperature
Make adjustments to temperature based on heating/cooling that may be occurring at
ground surface.
What is interpolation? - Answer-The process of estimating the quantity in between
locations with known quantity
What is free-air temperature? - Answer-The temperature at a particular level of the
atmosphere (assuming no heating/cooling effects from the surface)
What are dry adiabatic conditions? - Answer-Conditions where temperature decreases
with a height increase with 10 deg C per 1000 m
When can we assume a dry adiabatic lapse rate? - Answer-when the modelled
atmosphere is not close to saturation (below 80% relative humidity) AND
(a) if the winds are moderate or strong (~40 km/h or greater) or
(b) in the daytime during the spring, or
(c) in some cases during the afternoon on sunny winter days.
When can we assume a wet adiabatic lapse rate? - Answer-When the atmosphere is
saturated (100% relative humidity), which causes the temperature to decrease more
slowly with height.
What are wet adiabatic conditions? - Answer-Under wet adiabatic conditions,
temperature decreases at a rate of approximately 6°C per 1000 m (6°C/km) in mild air,
but the rate of decrease varies with temperature
What are stable conditions? - Answer-when the lapse rate is more stable than the wet
adiabatic lapse rate, meaning that the temperature decreases very slowly with height, or
even increases with height (called inversion)
, When/where does inversion occur? - Answer-Inversions typically occur locally within
valleys in the overnight and morning period in the winter, and during Arctic air outbreaks
How do we find free-air temperature? - Answer-1. If RH > 80%, use wet-air tool, if less
than use dry-air tool
2. Start from correct pressure level (85 kpa, 70 kpa)
3. Move parallel to green lines to correct height
4. Look to orange line to see new temperature
What are sources of heating and cooling within the troposphere? - Answer-The initial
source of heating and cooling is the ground surface.
During daylight, the sun heats up the ground which in turn heats up the air next to the
surface
At night, especially with clear skies, the surface cools radiatively (loses heat energy),
with the largest amount of cooling right at the ground surface.
What are the factors that affect heating and cooling? - Answer-Sun angle, cloud cover,
wind speed
What is sun angle and how does it affect heating and cooling? - Answer-The angle at
which the sun's rays hit strike the earth's surface; some parts of the earth get more sun
(midlatitudes where sun is perpendicular) and some get less sun (higher/lower altitudes)
As winter has much less daylight hours and less intensity than spring, the heating
adjustement daytime temperature is small (0-3C), while for spring it can be big (4-10C)
At night, sun angle is not a factor as there is no solar radiation
What is cloud cover and how does it affect heating and cooling? - Answer-Cloud cover
reduces the incoming solar radiation hitting the ground, and so it reduces daytime
heating measurement
The actual amount depends on the fraction of cloud cover and heights of clouds, but
roughly partly cloudy skies = half the sun's energy makes to the surface
During the night, if there are no clouds the ground radiates the heat back into space.
If there are clouds, they absorb the energy and re-radiate it back to the earth, meaning
surface still stays somewhat warm
What is wind speed and how does it affect heating and cooling? - Answer-During the
day, wind shear can cause mechanical mixing, which brings cooler from just above the
surface right down to the surface, so that the mountain slope-air temperature is closer to
the free air temperature (higher wind speed → greater effect)
At night, wind shear turbulence mixes warmer air closer to surface, reducing the
radiative cooling effect (means once again mountain slope is closer to free air)
