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Daily telemetry observations Go to www.nwac.us and click on Weather and Snowpack Information. Go to Alpental and make a table in your notebook that records the following data. Next go to Snoquamlie Pass, record 300’ data only. Introduction to G410. Daily weather and avalanche forecasts - PowerPoint PPT Presentation
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Introduction to G410Daily telemetry observationsGo to www.nwac.us and click on Weather and Snowpack Information.
Go to Alpental and make a table in your notebook that records the following data. Next go to Snoquamlie Pass, record 300’ data only.
Date 5400’ Tmin/max
4300’ Tmin/max
3120’ Tmin/max
RH 5420’
RH 3120’
Wind avg/max
Wind Dir.
Hr prec3120’
Tprec3120’
24 hr snow
Notes
Introduction to G410Daily weather and avalanche forecasts
Go to www.nwac.us and click on Forecasts
Read weather and avalanche forecast on a daily basis.
Add notes that help explain your telemetry data
Introduction to G410MOUNTAIN WEATHER FORECAST FOR THE OLYMPICS WASHINGTON CASCADES AND MT HOOD AREANORTHWEST WEATHER AND AVALANCHE CENTER SEATTLE WASHINGTON340 PM PST MON JAN 5 2009...corrected
WEATHER SYNOPSIS FOR MONDAY AND TUESDAYStrong and moist post frontal flow continues Monday afternoon. However the westerly flow is producing widely varying precipitation patterns with the concentration of the heavy precipitation in the north central Cascades, especially Stevens and Snoqualmie Passes where heavy precipitation has been occurring since the warm front passes early Monday morning.
Introduction to G410BACKCOUNTRY AVALANCHE FORECAST FOR THE OLYMPICS WASHINGTON CASCADES AND MT HOOD AREANORTHWEST WEATHER AND AVALANCHE CENTER SEATTLE WASHINGTON915 AM PST MON JAN 5 2009
ZONE AVALANCHE FORECASTSCASCADE PASSES, STEVENS, SNOQUALMIE AND WHITE PASSES-
AVALANCHE WARNING FOR MONDAY THROUGH TUESDAY....
Monday morning: HIGH avalanche danger below 7000 feet. Monday afternoon: HIGH avalanche danger above 4000 feet and CONSIDERABLE below.Monday night: Slowly decreasing HIGH avalanche danger above 4-5000 feet and CONSIDERABLE below.Tuesday and Tuesday night: Significantly increasing danger Tuesday morning becoming EXTREME above 4000 feet and HIGH below.
Introduction to G410
Bring to class1) Textbook – Avalanche handbook2) Calculator3) Pencil and eraser4) Lecture 7:30 pm – 9:30 pm
Bring to field1) Backpack2) Transceiver3) Shovel4) Probe5) Warm clothing -- see list on web site.
Mountain Weather and Energy Flux
Four factors that affect the formation and release of avalanches
Variations in solar heating create our dynamic atmosphere
Reasons Snow Important
•10% of the Earth's surface is covered by glacial ice, with snow covering the glacial ice.
* Small changes in climate can have very large effects on precipitation as snow, the amount of water stored as snow, and the timing and magnitude of snowmelt runoff.
Hydrologic Cycle
10% of the Earth's surface is covered by glacial ice, with snow covering the glacial ice.
Small changes in climate can have very large effects on precipitation as snow, the amount of water stored as snow, and the timing and magnitude of snowmelt runoff.
Phase diagram – H20
The phase diagram is divided into three regions, each of which represents a pure phase.
The line separating any two regions indicates conditions under which these two phases can exist in equilibrium.
Phase diagram – H20 Lets change pressure, and see how the boiling point and freezing (melting), point of water deviate from normal magnitudes.
Here we change the phase of a material without a change in temperature
General Circulation
Unequal heating between equator and pole causes circulation cells
Location of cells correspond to alternating belts of high and low pressure regions.
Cells also correspond to wind.Easterly winds from equator to 30° latitude (trade winds) and 60° to poles.
Westerly winds from 30° to 60°.
Jet Streams
Strong air currents produced by pressure gradient between poles and equator.
Location, strength and orientation vary with season and day to day.
Summer and Winter positions
Jet Streams
Air Masses
Regional scale volume of air with horizontal layers of uniform temperature and humidity.
Form during episodes of high pressure
Location name = origin
M = maritime
C = continental
T = tropical
P = polar
A = Arctic
Air Masses and Fronts
m = maritimec = continentalT = tropicalA = arctic P = polar
Mountain Climates of Western North America
• Four mountain ranges parallel west coast of North America
Coast Ranges Alaska Range Cascades Range Sierra Nevada
• Ranges - perpendicular to the prevailing westerly winds of the mid-latitudes
Mountain Climates of Western North America
Coast Range: Elevation varies from N to S. Olympic Mtns are highest portion of Coast Range in the USA
Cascades: Highest peaks are volcanoes. The mean crest elevation is considerably below the elevations of these isolated volcanoes.
North Cascades- somewhat higher elevations and heavy winter snowfalls produce extensive glaciation
Each mountain range varies w/respect to elevation
• Significant barriers to maritime air masses moving into the continent from the Gulf of Alaska and northern Pacific
• Moist air carried inland from the Pacific Ocean is lifted:
• First over the Coast Range• Then over the Cascades
Range
Mountain Climates of Western North America
• Low precipitation or rain shadows on the lee side of mountain ranges
West slope of Olympic Mts: 150” (381cm)Sequim, WA = 16 “ (41 cm)
•Supports different ecosystem, semi-arid
shrub/steppe.
Mountain Climates of Western North America
Coast Mountains: 2.3 SWE (1-7-2007; Hurricane Ridge, Olympic National Park, Washington)
Cascades Crest: 2.85 SWE (1-7-2007; Alpental Ski Area, Washington)
Eastern Washington: 0.12 SWE (1-7-2007; Mission Ridge Ski Area, Washington)
Mountain Climates of Western North America
Winter
• Storms develop in the area of the Aleutian Low & bring near continuous drizzle, rain and moderate coastal winds along the west coast of N. America
• Southwestery winds to the south of low pressure storm systems bring the heaviest precipitation
•Maritime influence moderates the temperatures
Mountain Climates of Western North America
Spring
• Pacific High moves northward and intensifies
• Milder, drier weather to the Coast and Cascades Ranges
• Clockwise circulation exposes the coast to winds out of the NW
• High pressure suppresses cloudiness and precipitation
Mountain Climates of Western North America
Synoptic (large-scale) weather systems• Monsoons• High & low pressure centers• Fronts
Introduction to the Atmosphere
Composition
A. Three gasesNitrogen (78%)Oxygen (21%)Argon (1%)
Introduction to the Atmosphere
B. Other gases• Water vapor (0 - 4% vol)• Carbon dioxide (0.034% vol)
Water vapor and CO2 absorb radiation emitted by the Earth’s surface and reradiate it back towards the Earth
C. Aerosols: natural or man-made• Rain, snow, ice, dust, pollen,• Carbon, Acids
Affect transmission of light - visibilityServes as a nuclei for condensation of
water vapor
Introduction to the Atmosphere
D. Humidity• Water content varies
over time and space• Amount of water vapor
depends on air temperature
• Warm air holds more water vapor than cooler air
• High humidity areas are found in warm equatorial regions
Introduction to the Atmosphere
Relative humidity
Ratio of actual water content of air to the water vapor content of saturated air at the same temperature
e = actual water vapor pressure
es= water vapor pressure that would have if it were saturated at its current temperature
Introduction to the Atmosphere
€
RH =100e
es
Relative Humidity• Percentage value• Water vapor content at
saturation rises with T, but actual vapor content does not
• Diurnal variations are present
• Relative humidity reaches max just before sunrise when temp is lowest.
• Relative humidity reaches min in mid-afternoon, when temp is highest.
Introduction to the Atmosphere
Introduction to the Atmosphere
Latent HeatLatent Heat: the amount of heat energy released or absorbed when a substance changes phases (ice to vapor, or rain to ice)
Introduction Atmospheric Structure
Vertical structure, exponential decrease of air density and pressure with height.
Air pressure: Mass per unit volume of atmosphere
• Millibars or pounds/sq inch
• Air pressure is the measure of weight of a column of air above that level
• Temperature, density, and pressure are closely related.Gas laws exponential decrease of air density and pressure
with height.
Introduction Atmospheric Structure
€
P = ρRT P = pressure
= air density
R = gas constant
T = absolute temperature
Atmospheric stability resistance to vertical motion.
• Stable atmosphere = horizontal clouds
• Unstable atmosphere = vertical clouds
Introduction Atmospheric Structure
In general, clouds form as a result of warm air rising, cooling, and expanding
Unstable atmosphere = vertical motions & vertical clouds
These types of layered clouds are called cumulus clouds
Introduction Atmospheric Structure
Stable atmosphere = horizontal clouds
These types of layered clouds are called stratus clouds
Air Parcel
• We used the term “parcel” when talking about moving air up or down in the atmosphere– Just a balloon-like volume of air that does not mix
with the surrounding air• New term: Adiabatic - a process in which no heat is
exchanged between an air parcel and the surrounding environment.
– If it rises, the air inside expands and cools– If it sinks, the air inside compresses and warms
Adiabatic Process
• The rate at which a parcel cools as it rises or warms as it sinks depends on whether or not the air is saturated
• Average rate = 6.5º C per 1000 m
• If the air is unsaturated (RH<100%), this rate is 10º C per 1000 m is is called the dry adiabatic lapse rate
Introduction Atmospheric Structure
Adiabatic change in the atmosphere as a parcel of air rises or sinks.
Moist Adiabatic Lapse Rate• If an unsaturated parcel of air rises and
cools, it will eventually cool to its dew point where it will be saturated (RH=100%)
• Further cooling results in condensation– This is when a cloud begins to form– Also, condensation represents a phase change
of water from a gas to a liquid. Latent heat is released
So if the air still continues to rise, will it still cool at the dry adiabatic rate?
Moist Adiabatic Lapse Rate
No, the rate will be less due to the release of latent heat So, rising saturated air does not cool as
quickly as rising unsaturated air In fact, it cools at an average rate of 6ºC
per 1000 m which is called the moist adiabatic lapse rate
Lapse Rates
RH < 100%
RH = 100%
RH = 100%
RH < 100%1000 m
Surface
2000 m
3000 m
30º
4º
10º
20º
Determining Stability
• If a parcel rises and cools, and is then colder than the surrounding air, it will sink back to its original position – stable
• If the parcel is warmer than the surrounding air, it will continue to rise - unstable
Review:Cloud Development and Stability
4 major ways air is forced to rise and produce clouds1) Heating at the surface (convection)
2) Topography (mountains, hills, etc.)
3) Convergence of surface air (air flows come together)
4) Uplift along fronts
Cloud Development and Stability
Convection Hot surface heats air Warm air rises Cooler air from above
sinks to replace it
• If the condensation level is low:
• One thermal may cause a cumulus cloud
• If high:• May take several
thermals
Sinking air at sides causes lots of blue sky in between clouds
Surface Energy Budget
Amount of heat and moisture transferred between the lower atmosphere & Earth’s surface.
Introduction Atmospheric Structure
Net solar and terrestrial radiation (R) at the Earth’s surface must be transformed into:Latent heat flux (L) used to evaporate or condense waterGround heat flux (G), used to warm or cool the groundSensible heat flux (H), used to warm or cool the atmosphere
Heat Definitions
Latent HeatLatent Heat: the amount of heat energy released or absorbed when a substance changes phases (ice to vapor, or rain to ice)
Sensible HeatSensible Heat: the heat that is transported to a body that has a temperature different than it’s surroundings (the heat difference you can “feel” or “sense”)
Net all-wave radiation term, RAll objects emit radiation.
The wavelength depends on the temperature of the radiating body
The Sun (6,000°C) emits most radiation in the wavelength range of .015-3 micrometers.
Human vision responds to the visible spectrum (0.36-0.75 micrometers).
Terrestrial objects have much lower temperatures and radiate energy at 3-100 micrometer wavelength.
Introduction Atmospheric Structure
Hot objects emit at short wavelengths
Cold objects emit at long wavelengths
Radiation from the Sun is called shortwave radiation.
Radiation emitted from objects or gases at normal terrestrial temperatures are called longwave radiation.
Introduction Atmospheric Structure
Longwave Radiation (LWR): heat you can’t see
Shortwave radiation (SWR):
visible light
Net radiation, RBoth short wave and long wave radiation can be directed
upward from the ground or downward from the atmosphere
Four components of the net all-wave radiation term Ra) incoming short wave radiationb) outgoing short wave radiation (fraction of the incoming shortwave
radiation)c) incoming long wave radiation emitted by gases and clouds in the
atmosphered) outgoing long wave radiation emitted by the Earth’s surface and
objects on it.
Introduction Atmospheric Structure
Diurnal Variations in R
Introduction Atmospheric Structure
Diurnal Variations in R
Both solar terms begin at sunrise and end at sunset.
Short wave R peaks at midday
At night, short wave R is zero
Why the lag between svr and T?
Introduction Atmospheric Structure
Processes affected by energy exchanges
Snow formation in the atmosphere
Snowpack metamorphism Surface hoar formation Near-surface facet formation Temp regimes and gradients