Weather, Climate and Ecosystems

Transcription

1 Weather, Climate and Ecosystems Dennis Baldocchi University of California, Berkeley 2/1/2013 Weather, Climate and Ecosystems: Outline Concepts Atmospheric Meteors and Composition Greenhouse-Effect Principles Seasons Global and Regional Circulation Climate Climate Forcing and Variability Global Temperature, Precipitation and Radiation Maps 1

2 Weather and Climate Meteors Electromagnetic Radiation Solar (shortwave) and Terrestrial (longwave) f(season, clouds) Temperature Air, soil, vegetation Wind Velocity and Direction Moisture Gaseous: vapor pressure, Relative Humidity, dew point Liquid: Rain, dew, clouds Solid: snow, sleet, frost, hail, rime, clouds Pressure Many Ecological Processes are a Function of, or Correlate with, Climate and Weather Photosynthesis = f(sunlight, temperature, humidity, rainfall) Evaporation = f(sunlight, temperature, humidity, rainfall) Respiration = f(temperature, rainfall) Decomposition =f(temperature, rainfall) Ecosystem Structure and Function = f(sunlight, temperature, rainfall) Soil Formation and Nutrition= f(temperature, rainfall) 2

3 Weather vs Climate Weather is the Recent Condition of the Atmosphere, yesterday, today, tomorrow Weather is Chaotic, can Exhibit Extreme Behavior Climate is the Average Condition of the Atmosphere over long-time durations, e.g. 30 years, Century, Millennium Climate is relatively stable, e.g. summers are hot, winters are cold Weather/Climate Concepts Atmosphere is a Dynamic and Complex System Multiple Positive and Negative Feedbacks that operate across a Spectrum of Time and Space Scales Non-Linear Processes Sensitivity to Initial Conditions Experiences Strange Attractors, so is Phase Space is Constrained Thresholds and Tipping Points 3

4 Chemistry and Physics of the Atmosphere Atmospheric Composition Nitrogen % Oxygen % Argon 0.934% Carbon Dioxide % Water Vapor 0.1 to 4% Trace Gases Nitrous Oxide, CO, Methane, Ozone, VOCs 4

5 Partial Pressure Law Total Pressure is the sum of the partial pressures of its components P=p n2 +p o2 +p ar +p h2o +p co2 + P at sea level, kpa P equal mass of overhead atmosphere time acceleration due to gravity, per unit area P M g A Atmospheric Temperature Profile 5

6 Solar Constant 1366 J m -2 s -1 or W m -2 Amount of Energy Available to Drive Work by the Climate System and Life Comparison between Planck s Law for Sun and Earth Planck's Law 1e+15 1e+14 1e+13 1e+12 Sun, T = 5800 K Earth, T = 298 K 1e+11 Energy (T, ) 1e+10 1e+9 1e+8 1e+7 1e+6 1e+5 1e+4 1e+3 1e-8 1e-7 1e-6 1e-5 1e-4 1e-3 Wavelength, m 6

7 Many Atmospheric Trace Gases Absorb & Re-emit Infrared Radiation Absorption Cross-Section (cm -1 /(molecule cm -2 ) 1e-17 H 2 O CO 2 1e-18 1e-19 1e-20 1e Wavelength (microns) HI-Tran Database 7

8 Trenberth et al 2009 BAMS 8

9 Basic Earth/Sun Geometry Lutgens/Tarbuck, Atmosphere Natural Solar Forcing of Climate Variability Over Geological Time Zachos et al Science

10 Natural Forcing of the Climate System, last Million Years Source Rob Rohde, Timing of Ice Ages MilankovitchTheory states Glaciers form when solar intensity is weak during summer of northern latitudes, as when Earth is less tilted with orbital plane (e.g. Obliquity with 41 ky cycles) Isotope show ice-ages grow and wane with 41 ky cycle for Early Pleistocene (1-3 Million ybp) and 100ky cycle in late Pleistocene (0-1 Million ybp) Eccentricity of Earth s orbit with 100 ky cycle has a weak forcing on summer insolation The integral of solar radiation (time x intensity), not peak irradiance, controls 41 ky timing of ice age of the Early Pleistocene (1 to 3 million ybp) This corresponds with Obliquity, which has 41 ky cycle instead of 100 ky with Eccentricity because Summers are shorter when Earth is closer to Sun and Radiation is greatest 10

11 Lapse Rates, Temperature Decreases with Height Dry Adiabatic Lapse Rate 9.8 C km -1 Moist Adiabatic Lapse Rate 6 C km -1 Change in Internal Energy Equals Change in Work Done on the Air Parcel Adiabatic Lapse Rate, Lifted Condensation Level and Clouds 11

12 Concepts of Thermal Stratification near neutral stability unstable thermal stratifiation stable thermal stratification Tparcel < Tair Height, m T z Height, m Tparcel > Tair T z Height, m T z Temperature Orographic Precipitation Air Lifted by a Mountain, Cools, Can Condense, Form Clouds and Rain/Snow 12

13 Succession of Weather Fronts off the Pacific Coast of North America Role of High and Low Pressure Zones on Weather High and Low Pressure Systems in Northern Hemisphere Anti-Cyclonic Circulation: Air is Divergent High Cyclonic Circulation Air is Convergent LOW 13

14 Convergence: Air Rises, Temperature Decreases, Vapor Condenses, Clouds Form, Rain Possible LOW Divergence: Air Sinks, Temperature Warms Cloud Formation is Suppressed High 14

15 Cold and Warm Fronts and Rain Two Ways to Lift Parcels of Air, Form Clouds and Rain Large Scale Patterns Dominating Weather in California Aleutian Low Steer Storm Tracks during Winter North Pacific High Block Storms during Summer 15

16 Rainfall Periodicity and Scale Weltzin et al 2003 Bioscience Differential Solar heating causes Air to rises at equator and subsided at poles This is superimposed upon the Earth s rotation and the Coriolis Force which determines wind direction Circulation cells help explain global distribution of rainfall From Chapin 16

17 La Nina El Nino 17

18 Climate Distribution IPCC dataset 18

19 IPCC dataset 19

20 Summary Solar Energy Drives Weather and Climate Trace Gases that absorb and re-radiate energy warm the atmosphere and Earth s surface above its radiative equilibrium value Differential heating of the Earth and its Rotation causes circulation of the air Different declination, relative to the Sun, causes the seasons. Discussion Points Next Ice Age? Would Occur within next 1500 Years if CO 2 did not rise above 280 ppm? Will Future Generations Hate or Thank Us With 7+ Billion People Living on Earth what would happen if we did not stave off the Next Ice Age? Is our Fossil Fuel Emissions a form of GeoEngineering to Prevent the Next Ice age? Tzedakis et al Nature Geoscience 20