Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Introduction to G410 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. Date 5400’ T min/max 4300’ T min/max 3120’ T min/max RH 5420’ RH 3120’ Wind avg/max Wind Dir. Hr prec 3120’ Tprec 3120’ 24 hr snow Notes Introduction to G410 Daily 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 G410 MOUNTAIN WEATHER FORECAST FOR THE OLYMPICS WASHINGTON CASCADES AND MT HOOD AREA NORTHWEST WEATHER AND AVALANCHE CENTER SEATTLE WASHINGTON 340 PM PST MON JAN 5 2009...corrected WEATHER SYNOPSIS FOR MONDAY AND TUESDAY Strong 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 G410 BACKCOUNTRY AVALANCHE FORECAST FOR THE OLYMPICS WASHINGTON CASCADES AND MT HOOD AREA NORTHWEST WEATHER AND AVALANCHE CENTER SEATTLE WASHINGTON 915 AM PST MON JAN 5 2009 ZONE AVALANCHE FORECASTS CASCADE PASSES, STEVENS, SNOQUALMIE AND WHITE PASSESAVALANCHE 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 class 1) Textbook – Avalanche handbook 2) Calculator 3) Pencil and eraser 4) Lecture 7:30 pm – 9:30 pm Bring to field 1) Backpack 2) Transceiver 3) Shovel 4) Probe 5) 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 = maritime c = continental T = tropical A = arctic P = polar As these air masses move around the Earth, they acquire additional attributes. 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 Each mountain range varies w/respect to elevation 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 Mountain Climates of Western North America • 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. 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 • Precipitation is highly seasonal • Influenced by Aleutian Low & Pacific High •These two semi-permanent pressure systems move in tandem.. • Northward shift in summer • Southward shift in winter 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 Introduction to the Atmosphere Synoptic (large-scale) weather systems • Monsoons • High & low pressure centers • Fronts Introduction to the Atmosphere Composition A. Three gases Nitrogen (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 - visibility Serves 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 RH 100 es e = actual water vapor pressure es= water vapor pressure that would have if it were saturated at its current temperature Introduction to the Atmosphere 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 Water phase changes in atmosphere Water vapor Liquid water Solid water Water changes between phases • Phase changes release or store large quantities of heat, called • Heat must be supplied to change solid to liquid or solid to vapor • Heat is liberated with reverse phase • Amount of heat required to evaporate water is equal to the amount of heat liberated when water vapor condenses. Latent 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 • • Stratosphere • Mesosphere • Thermosphere • Defined by air temperature w/r to height Vertical structure, exponential decrease of air density and pressure with height. Introduction Atmospheric Structure 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. P RT P = pressure = air density R = gas constant T = absolute temperature Introduction Atmospheric Structure Atmospheric stability resistance to vertical motion. • Stable atmosphere = horizontal clouds • Unstable atmosphere = vertical clouds In general, clouds form as a result of warm air rising, cooling, and expanding Introduction Atmospheric Structure Unstable atmosphere = vertical motions & vertical clouds These types of layered clouds are called cumulus clouds 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 3000 m 4º RH = 100% 2000 m 10º RH = 100% 1000 m 20º RH < 100% 30º RH < 100% Surface 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 clouds 1) 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 Introduction Atmospheric Structure Surface Energy Budget Amount of heat and moisture transferred between the lower atmosphere & Earth’s surface. Net solar and terrestrial radiation (R) at the Earth’s surface must be transformed into: Latent heat flux (L) used to evaporate or condense water Ground heat flux (G), used to warm or cool the ground Sensible heat flux (H), used to warm or cool the atmosphere Heat Definitions Latent Heat: the amount of heat energy released or absorbed when a substance changes phases (ice to vapor, or rain to ice) Sensible 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”) Introduction Atmospheric Structure Net all-wave radiation term, R All 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. Hot objects emit at short wavelengths Cold objects emit at long wavelengths Introduction Atmospheric Structure Radiation from the Sun is called shortwave radiation. Radiation emitted from objects or gases at normal terrestrial temperatures are called longwave radiation. Longwave Radiation (LWR): heat you can’t see Shortwave radiation (SWR): visible light Introduction Atmospheric Structure Net radiation, R Both 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 R a) incoming short wave radiation b) outgoing short wave radiation (fraction of the incoming shortwave radiation) c) incoming long wave radiation emitted by gases and clouds in the atmosphere d) 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? Processes affected by energy exchanges Snow formation in the atmosphere Snowpack metamorphism Surface hoar formation Near-surface facet formation Temp regimes and gradients