Focus on the Terrestrial Cryosphere Cold land areas where water is either seasonally or permanently frozen. Terrestrial Cryosphere 0.25 m Frost Penetration One Year in Ten 0 E C Mean Temperature during Coldest Month 100 Days of Ice on Navigable Waterways Most Mountain Regions Over 1000 m in Elevation Most Mountain Regions Over 1000 m in Elevation

Focus on the Terrestrial Cryosphere Spatial extents of frozen and thawed areas vary significantly on daily, seasonal, and interannual time scales. Terrestrial Cryosphere Over 30% of Earth’s land surface has seasonal snow. 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. Seasonally and permanently frozen soils occur over ~35% of Earth’s land surface.

Cold Land Processes Process-Oriented State Variables Snow and Freeze/ Thaw Processes Snow Water Equivalent (Depth and Density) Snow Water Equivalent (Depth and Density) Snow and Frozen Soil Internal Energy (relative to melting point) Snow and Frozen Soil Internal Energy (relative to melting point) Snow Wetness (Liquid Water Content) Snow Wetness (Liquid Water Content) Snow Grain Size, Albedo Snow and Soil Surface Temperature Snow and Soil Surface Temperature Soil Moisture Cold Land/Atmosphere Energy Exchanges Cold Land/Atmosphere Energy Exchanges Boundary Layer Turbulence and Stability Boundary Layer Turbulence and Stability Liquid Water Movement through Snow and Soil Liquid Water Movement through Snow and Soil Water Vapor Movement through Snow and Soil Water Vapor Movement through Snow and Soil Effects of Clouds on Radiation Energy Fluxes Effects of Clouds on Radiation Energy Fluxes Precipitation Characteristics Energy Sink FEEDBACKSFEEDBACKS

Cold Land Processes Focus on Improving Observation of Processes A tremendous gap exists between the scales of our process-oriented understanding, and the scales of synoptic weather and climate.

Snow Accumulation/ Ablation Soil Freeze/Thaw Transitions Most of our knowledge of cold land hydrologic processes is limited to local and hillslope scales. Cold Land Processes Focus on Improving Observation of Processes Snow Energy and Mass Exchanges Infiltration, Unsaturated Flow Evapotranspiration Overland Flow Saturated Flow

Snow Accumulation/ Ablation Soil Freeze/Thaw Transitions 100 km Focus 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 bin/uawxstn/wxtail5.plhttp:// bin/uawxstn/wxtail5.pl

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