Chapter 5: Hydrological Cycle

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Chapter 5 Hydrological Cycle

• This chapter discusses
• Water Storages and Fluxes
• Precipitation
• Evaporation
• Runoff

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Hydrologic Cycle
MOVEMENT of Water and Energy Between Stores
1. Most Rapid Movement In Vapor Phase, in the
Atmosphere 2. Most Water and Energy Storage In
Liquid Phase, in the Oceans 3. Most of Water
useful to Humanity in Rivers, Lakes,
Subterranean Water, and Ice and Snow, as Fresh
Water 4. Hydrologists Focus of Interest is on
Movement of Fresh Water Between these last-named
marginal fresh water stores
5. At all Spatial Scales, such Movement is a
Combination of Physically Determined Mean
Movements , with imposed Statistically
Constrained Turbulent Fluctuations
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Hydrological Cycle
MOVEMENT of Water and Energy Between Stores

• 6. Our Main Allies when describing such Movement
  are
• Mass and Energy Conservation Laws
• Diffusion Equations for Mass and Energy Movement
• Experimental Studies (to define parameters)

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Where is the Water?
Location of Water in Global Systems
Water Volumes (106 km3) Oceans 1348 Ice
Snow 27.8 Groundwater 8.062 Surface
Water 0.225 Atmosphere 0.013
But human impact is mainly through Mobile Fresh
Water
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How Much Does the Water Move?
1. The following traditional, simple model is
second order Ocean (Evaporation)
Atmosphere (Rainfall) Rivers
(Runoff) Ocean
2. Actual Hydrological Cycle
3. Residence Time Storage / Flux
S 0.013x106 km3, P 107x0.7A75x0.3A, A
4pr2, t S/P 9.5 days
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How Much Does the Water Move?
3. Geographical Distribution of Exchanges
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Zonal Mean Precipitation
http//www.atmo.arizona.edu/students/courselinks/s
pring03/atmo421/prec.html
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Annual Mean Precipitation
http//www.atmo.arizona.edu/students/courselinks/s
pring03/atmo421/prec.html
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Geographic Distribution of Annual P-E (mm)

• Evaporation excess nearly ubiquitous over
  sub-tropical oceans, with a sharp contrast at
  coastal regions.
• Equatorial ocean evaporation minimum consistent
  with other findings (e.g. Seager et al., 2003).
• Tropical land areas show richest excess in
  precipitation.
• Major desert regions, tundra, and mountainous
  regions all indicate deficit to
  marginally-balanced conditions.
• Mid-latitude and boreal coastal/maritime
  environments exhibit adequate precipitation
  supply over evaporation.

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Precipitation
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Precipitation
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Water Research Plans

• What are the causes of
• water cycle variations?
• Are variations in the global
• and regional water cycle predictable?
• How are water and
• nutrient cycles linked?

Water and Energy Cycle Research Challenge
Document and enable improved water and energy
cycle consequence predictions (floods and
droughts) of earth system variability and change
Interdisciplinary Research

• Interdisciplinary Linkages
• Aerosols link to precipitation development,
  interaction with energy/radiation cycles
• Carbon link to transpiration and radiation
  absorption
• Weather and Climate water and energy are at the
  heart of weather and climate physics
• Modeling, Assimilation, and Computing essential
  tools for integration and prediction
• Technology development of new observation
  technology
• Applications consequences of change delivered
  through water energy cycle

By courtesy of Paul Houser
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ROLES OF AGENCIES IN THE WATER CYCLE PROGRAM
UNDERSTANDING NSF, NASA, DOE
USDA USGS APPLICATIONS EPA BoR USACE
PREDICTION NOAA, DOE, NASA
OBSERVATIONS NASA, NOAA (DOE, USGS, USDA)
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Water Cycle Observation

• Input - Output Storage Change
• Transport Evaporation - Precipitation Runoff
  - P ?Land Storage ?Water Vapor

The availability of new observations strongly
motivates advances in understanding, prediction,
and application.
We must define a integrated water energy
observation system that can not only detect
global mean trends but also local variation of
extremes
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Water Cycle Observation Strategy
Future Water Cycle Mission Observation of water
molecules through the atmosphere and land surface
using an active/passive hyper spectral microwave
instrument.
ICEsat Aquarius Jason NPOESS SMOS Landsat/SPOT Geo
stationary DMSP NOAA Hydro Altimetry Etc.
Primary missing global observations
Precipitation, Soil Moisture, Snow
Need a strategy to compare and integrate and make
sense of existing observations
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Some Examples of Field Programs

• Cabauw
• Type Short Grass
• Cover 16.6
• Precip 776 mm
• Data Jan 87 - Dec 87

• BOREAS (NSA-OJP)
• Type Evergreen Needleleaf
• Cover 6.5
• Precip 242 mm
• Data Jan 94 - Dec 96

• ARM-CART (E13)
• Type Mixed Crop / Farm Land
• Cover 8.1
• Precip 600 mm
• Data Apr 95 - Aug 95

• Tucson
• Type Semi-Desert
• Cover 9.2
• Precip 275 mm
• Data May 93 - Jun 94

• ABRACOS (Reserva Jaru)
• Type Evergreen Broadleaf
• Cover 9.7
• Precip 1600 mm
• Data May 92 - Dec 93