Earth: The Water Planet

Planetary Temperature and Energy in the Climate System

• Sources?• Geothermal Heat Flow (cooling of Earth’s

hot interior)– 0.075 W/m^2 (Watt = Energy Flux, J/s)– 100’ x 100’ = 1000m^2 = 75 Watt total

• Solar radiation– ~1366 W/m^2 incoming (what sets this?)– ~1000 W/m^2 reaches surface

• Remember: Conserve Energy

The Water Planet

The Fate of Solar Insolation

19%

6%

25%

45%

5%planetary albedo = 30%Earth and Atmosphere absorb 45% + 25% = 70% of solar insolation

Solar Energy Drives Hydrologic Cycle

Hydrologic Cycle Questions• How does the WATER Cycle compare to the Hydrologic

Cycle?• On an annual, global average, how do ET and P

compare? P >> ET, P > ET, P = ET, P < ET • What about over land?• Amazon rainforest: how does total P compare to

moisture flux from oceans (more, equal, less) – and why?

• As we will learn, most rainfall on land soaks into the ground, only impermeable areas (rock, urban areas) or particularly intense rainfall cause direct runoff. Given this why do we have rivers?

Hydrologic Cycle

Hydrologic Cycle: Conservation of Mass

Atmosphere12.7

Ocean1,335,040

Surface Water300

Groundwater15,300

413

73373

{40}

113

30-38

2-10

{+40}{-40}

Reservoir Volumes: 1000 km3 Fluxes: 1000 km3/yr

Residence Time = Volume/Flux (yr)

Discussion of Reading

• Any questions, points of clarification in (a) A&A chap 1, (b) Allen, 2008?

• What are some Big Questions in Geomorphology?• What are the Guiding Principles to the Study of

Geomorphology outlined by Anderson and Anderson?

Willett, 1999 JGR

Beaumont et al., 2001 Nature

Numerical Simulations: Strong Climate-Tectonics Coupling

Overview/Guidelines (Chapter 1)• Many interacting processes: wind, rain, runoff, ice,

heat/cool, freeze/thaw, chemical attack – all modulated by life; all event-driven, variable

• Interaction of different timescales• Hillslopes and Channels (+ floodplains)

• Our Approach: • Conservation (of mass [water, sediment, atoms],

energy, momentum)• Transport Rules (flow of water, mud, ice, transport of

sediment, etc)• Event Size, Frequency and Duration (storms, floods,

climate variations, etc)

NET RADIATION (INCOMING SHORTWAVE MINUS OUTGOING LONGWAVE)

http://geography.uoregon.edu/envchange/clim_animations/

AIR TEMPERATURE (Mean Monthly)

PRECIPITABLE WATER VAPOR (in air column)

PRECIPITATION (Mean Monthly)

EFFECTIVE PRECIPITATION (Ppt - Evap)

Atmospheric Rivers

Simplest Model: Q = C R_i A(Storm Response)

What Sets Flood Discharge (thus shear stress exerted on the bed)?

Runoff Essentials

• Simple Empirical Model: Q = C R_i A

• Runoff Pathways – basic properties and controls, hydrograph implications

• Infiltration Capacity (velocity)

• The Importance of Saturation State

• The Variable Source Area Concept

Runoff Essentials

• Simple Empirical Model: Q = C R_i A

• Runoff Pathways – basic properties and controls, hydrograph implications

• Infiltration Capacity (velocity)

• The Importance of Saturation State

• The Variable Source Area Concept

What is Hydraulic Head?

• The total force driving flow of groundwater• Why does Water stay still in a cup or bowl?• What can make water in pipes flow?

– Elevation: flow downhill (gravity)– Pressure: use pumps to create pressure and

drive water uphill (or just faster)• Elevation Head + Pressure Head

– GW Elevation head = elevation * density * gravity (potential energy per unit volume)

– GW Pressure head = weight of overlying water (per unit volume)

Darcy’s Law

• Darcy’s law provides an accurate description of the flow of ground water in almost all hydrogeologic environments.

• = the basis of a pretty good job

Darcy’s Law

V = – K (∆h/∆L)

Q = VA (A = cross-section area)

Q = – KA (∆h/ ∆L)

Q/A = – K (∆h/ ∆L)

Darcy’s Experiment (1856):Flow rate determined by Difference in Hydraulic Head per flow path length { h/l = (h1 – h2)/l }

Group Project: Sketch Out What Darcy Did to Discover His Famous EquationExtra Credit to first Team that can make a sketch of experimental data that would supportDarcy’s Law and satisfactorily explain it to me

Sketch of Experimental Data

?

?

h/l

Runoff Essentials

• Simple Empirical Model: Q = C R_i A

• Runoff Pathways – basic properties and controls, hydrograph implications

• Infiltration Capacity (velocity)

• The Importance of Saturation State

• The Variable Source Area Concept

Next: Controls on Hydrographs

San Gabriel Mtns: Mean Daily Q

Mean Daily Runoff = Q/A = ~225 mm/yr(~33% of MAP)

San Gabriel Mtns: Q10

Hydrologic Process Transforms Distribution of Rainfall

Hurricane Irene Hydrological Response

North Carolina

Maryland

New Jersey

Pennsylvannia

New York

Massachusetts

New Hamshire

From Perron et al., Nature 2009

Predicted Lc

Obs

erve

d A

c 1/

2