Focus on the Terrestrial Cryosphere

Cold land areas where water is either seasonally or permanently frozen.Cold land areas where water is either seasonally or permanently frozen.

Terrestrial CryosphereTerrestrial Cryosphere

0.25 m Frost Penetration One Year in Ten0.25 m Frost Penetration One Year in Ten

0C Mean Temperature during Coldest Month0C Mean Temperature during Coldest Month

100 Days of Ice on Navigable Waterways100 Days of Ice on Navigable Waterways

Most Mountain RegionsOver 1000 m in ElevationMost Mountain Regions

Over 1000 m in Elevation

Focus on the Terrestrial Cryosphere

Spatial extents of frozen and thawed areas vary significantly on daily,Spatial extents of frozen and thawed areas vary significantly on daily,seasonal, and interannual time scales.seasonal, and interannual time scales.

Terrestrial CryosphereTerrestrial Cryosphere

Over 30% of Earth’s land surface has seasonal snow.Over 30% of Earth’s land surface has seasonal snow.

On average, 60% of Northern Hemisphere has snow cover in midwinter.On average, 60% of Northern Hemisphere has snow cover in midwinter.

About 10% of Earth’s land surface is covered permanently by snow and ice.About 10% of Earth’s land surface is covered permanently by snow and ice.

Seasonally and permanently frozen soils occur over ~35% of Earth’s land surface.Seasonally and permanently frozen soils occur over ~35% of Earth’s land surface.

Cold Land Processes

Process-OrientedProcess-OrientedState VariablesState Variables

Snow and Freeze/Snow and Freeze/Thaw ProcessesThaw Processes

Snow Water Equivalent(Depth and Density)

Snow Water Equivalent(Depth and Density)

Snow and Frozen SoilInternal Energy

(relative to melting point)

Snow and Frozen SoilInternal Energy

(relative to melting point)

Snow Wetness(Liquid Water Content)

Snow Wetness(Liquid Water Content)

Snow Grain Size, AlbedoSnow Grain Size, Albedo

Snow and Soil Surface Temperature

Snow and Soil Surface Temperature

Soil MoistureSoil Moisture

Cold Land/AtmosphereEnergy Exchanges

Cold Land/AtmosphereEnergy Exchanges

Boundary LayerTurbulence and Stability

Boundary LayerTurbulence and Stability

Liquid Water Movementthrough Snow and Soil

Liquid Water Movementthrough Snow and Soil

Water Vapor Movementthrough Snow and Soil

Water Vapor Movementthrough Snow and Soil

Effects of Clouds onRadiation Energy Fluxes

Effects of Clouds onRadiation Energy Fluxes

Precipitation CharacteristicsPrecipitation Characteristics

Energy Sink

FEEDBACKS

Cold Land Processes

Focus on Improving Observation of ProcessesFocus on Improving Observation of Processes

A tremendous gap exists A tremendous gap exists between the scales of our between the scales of our process-oriented process-oriented understanding, and the scales understanding, and the scales of synoptic weather and of synoptic weather and climate.climate.

SnowAccumulation/

Ablation

SnowAccumulation/

Ablation

SoilFreeze/ThawTransitions

SoilFreeze/ThawTransitions

Most of our knowledge of Most of our knowledge of cold land hydrologic cold land hydrologic processes is limited to local processes is limited to local and hillslope scales.and hillslope scales.

Cold Land Processes

Focus on Improving Observation of ProcessesFocus on Improving Observation of Processes

Snow Energy and Mass ExchangesInfiltration, Unsaturated FlowEvapotranspirationOverland FlowSaturated Flow

SnowAccumulation/

Ablation

SnowAccumulation/

Ablation

SoilFreeze/ThawTransitions

SoilFreeze/ThawTransitions100 km

Focus on Improving ObservationsFocus on Improving Observations

Cold Land Processes

This Class - Weather

• basics– density, pressure

• cloud formation• storms and cyclones

– air masses

Weather and climate

• Weather – state of atmosphere at specific place and time

• Climate – long-term (30 year) average of weather patterns

Basics – density of air

• Less dense air rises• More dense air sinks

• Warm air is less dense than cold air• Humid air is less dense than dry air

Density increases caused by -

• temperature• pressure• water vapor content

Density decreases caused by -

• temperature• pressure• water vapor content

Density differences drive air motion

High pressure

• descending air • descending air compresses and warms• warming air inhibits the formation of clouds• sky is sunny• flows clockwise in N. hemi

Low pressure

• rising air• rising air expands and cools – adiabatic

expansion• cooling air creates clouds as water vapor

condenses, releases latent heat energy• flows anticlockwise in N. hemi

• High pressure areas have clear weather

• Low pressure areas have stormier weather.

Where are the high and low pressure zones?

ITCZ water vapour – rising air warm, also lots of water

Deserts of the World

• 30˚ N and S

weather

Air masses

• Large homogenous body of air• Same temperature, humidity, and density• Can move within or between circulation cells• Need energy to mix two air masses

– Creates turbulence

• Front – boundary between two air masses

Cloud formation - convection

• Ground is heated by sunlight.

• Warm air rises.• At height, condenses to

form tiny water droplets, which are buoyed up by the rising warm air.

Cloud formation – orographic effects

• Air is forced to rise up along a mountain.

• Rising air cools and condenses.

Cloud formation – cold fronts

• Cool air mass advances.• Warmer air masses are

forced upward.• Warmer air mass cools

as it rises and condenses.

• Cold fronts

Cirrus clouds

• high pressure zone

Cumulus cloud

Cumulonimbus clouds

• cold front• low pressure zone

web cam tucson’s weather - 11

web cam tucson’s weather - 13

Tucson’s weather

• University of Arizona’a weather station• http://www.atmo.arizona.edu/cgi-bin/uawxstn

/wxtail5.pl

weather

weather

weather

satellite image of clouds at 7:30 Feb 18

Storms

• Regional disturbances in the atmosphere• Characterized by strong winds and

precipitation

Cyclones

• Rotating masses of low-pressure air with converging and ascending winds

• Extratropical– between two air masses • Tropical– within one warm humid air mass

Extratropical cyclones

• Form at polar front - boundary between Ferrel cells and polar cells

• Occur mainly in winter– Temperature and density differences are greatest

• Move eastward• 1,000 – 2,500 km wide• Last 2 – 5 days

weather

Extratropical cyclone clouds

storm1

storm2

storm3

Tropical cyclones

• Form between 10º and 25º • Tropical storm or tropical depression - winds < 119

km/hr• Hurricane - winds > 119 km/hr• Create intense rainfall and storm surge• 1,000 km wide• Last 3 hours - 3 weeks (5 – 10 days)

Tropical cyclone (Hurricane Andrew)

Fig 8.22/tropical development

ITCZ water vapour

Fig 8.23b/global tropical cyclone map

floods - weather’s biggest killer

• deep snow cover• frozen ground• wet or saturated soil• full reservoirs• high river and stream levels• ice-covered rivers• widespread heavy rain

Fig 8.15/extratropical cyclone development

ITCZ water vapour – rising air warm, also lots of water

temperatures

weather

http://www.nohrsc.nws.gov/%7Ecline/clp.html