Surface Water Balance (1)Surface Water Balance (1)

Review of last lecture: Surface energy balanceReview of last lecture: Surface energy balance

dT/dt

SWdn =Scos

SWup =SWdn

LWdn =Tair4

LWup=Ts4

LH=CdLV(qsurface- qair) SH=CdCpV(Tsurface- Tair)

Fc = - dT/dz

Incoming shortwave + Incoming longwave = Reflected shortwave + Emitted longwave + Latent heat flux + Sensible heat flux + Subsurface conduction

• What is sensible heat flux? What is latent heat flux?• Bowen ratio B= SH/LH = Cp(Tsurface - Tair) / L(qsurface - qair) provides a simple way for estimating SH and LH when the net radiative flux Fr is available LH=Fr/(B+1), SH=Fr B/(B+1)• Factors affecting soil thermal conductivity• Other heat sources: precipitation, biochemical, anthropogenic

The global water cycleThe global water cycle

Components of global water cycleComponents of global water cycle

• Ocean water• Land soil moisture, rivers, snow cover, ice

sheet and glaciers• Sea ice• Atmosphere water vapor, clouds, precipitation• Water in biosphere (including human beings)

Component I: Ocean Component I: Ocean Covers 70% of the Earth’s surfaceCovers 70% of the Earth’s surface

Observed Changes in Global Sea LevelObserved Changes in Global Sea Level

Observed Changes in Sea Level Observed Changes in Sea Level Largest in the western part of ocean basinLargest in the western part of ocean basin

Observed Changes in Ocean Heat ContentObserved Changes in Ocean Heat Content

Component II: LandComponent II: LandSoil moistureSoil moisture

Component II: LandComponent II: Land>1000 major rivers flow on the seven continents>1000 major rivers flow on the seven continents

Amazon river (#1) Yangtze river (#4)Mississippi river (#6)

Component II: LandComponent II: LandSnow coverSnow cover

Observed Changes in Snow Cover: Observed Changes in Snow Cover: Significant meltingSignificant melting

Component II: LandComponent II: LandIce sheetIce sheet

Retreat of Greenland Ice Sheet – a huge contributor to sea level rise today

Greenland is responsible for about 10% of the observed global sea level riseand accelerating. Greenland holds 7 m of sea level equivalent.

Component II: LandComponent II: LandGlaciersGlaciers

Retreat of Mountain Glaciers: a major contributor to sea level rise

IPCC (2001)

Glacier retreat is a world-wide phenomena.

Will affect water supply for millions:• Kenya/Tanzania• Northern India• Andes Mountains

Melting in Glacier National ParkMelting in Glacier National Park

Component III: Sea iceComponent III: Sea ice

Observed Changes in Arctic Sea Ice: Observed Changes in Arctic Sea Ice: Significant meltingSignificant melting

Reduced Arctic sea ice: A result of warming that leads to more warming

Component IV: AtmosphereComponent IV: AtmosphereWater vapor flows in the atmosphereWater vapor flows in the atmosphere

Observed Changes in Water Vapor Observed Changes in Water Vapor Significant increaseSignificant increase

Component IV: AtmosphereComponent IV: AtmosphereClouds drifts with the windsClouds drifts with the winds

Component IV: AtmosphereComponent IV: AtmospherePrecipitation drives many atmospheric circulations Precipitation drives many atmospheric circulations

which in turn transport water around the worldwhich in turn transport water around the world

Hadley Circulation

MonsoonsWalker Circulation

Observed Changes in Precipitation: Observed Changes in Precipitation: Significant change in many placesSignificant change in many places

A significant fraction of the human body A significant fraction of the human body is water (~75%)is water (~75%)

The remaining: fat, protein, carbonhydrate, other solids

So the water in our bodies may come from …So the water in our bodies may come from …

A stream in the Niagara Fall …

A white cloud over the tropical Pacific …

A raindrop in the Amazon rainforest …

Therefore we need to protect the environment because any pollution we put into the environment may someday come back into our bodies

An ice sheet in the Arctic Ocean…

Summary:Summary:Components of global water cycleComponents of global water cycle

• Ocean water• Land soil moisture, rivers, snow cover, ice

sheet and glaciers• Sea ice• Atmosphere water vapor, clouds, precipitation• Water in biosphere (including human beings)