natural environments: the atmosphere gg 101 – spring 2005 boston university myneni lecture 02:...
Post on 22-Dec-2015
215 views
TRANSCRIPT
Natural Environments: The AtmosphereGG 101 – Spring 2005
Boston University
MyneniLecture 02: Introduction
Jan-21-05(1 of 11)
Outline
- Context: where does this course material fit?
- Conceptual model: the four great realms
- Methodology: the systems approach
- characterizing the system (dynamics, interactions, scales)
- System Processes: weather and climate
Further Reading: Chapters 01 and 02 of the text book
Natural Environments: The AtmosphereGG 101 – Spring 2005
Boston University
MyneniLecture 02: Introduction
Jan-21-05(2 of 11)
The subject matter of this course: 1. Radiation and energy balance of the Earth 2a. Weather: patterns and processes
2b. Circulation of the atmosphere & oceans 3. Climate and climate change
may be thought of as belonging to Physical Geography.
What is Physical Geography?
It is the study of processes and patterns at the interface between physical systems (oceans, atmosphere, ecosystems, hydrology, geologic substrate) and human activity (how do humans shape the environment and environmental processes?) withemphasis on natural and physical systems.
Natural Environments: The AtmosphereGG 101 – Spring 2005
Boston University
MyneniLecture 02: Introduction
Jan-21-05(3 of 11)
Example of a physical geography problem
The global carbon cycle and climate – human actions such as burning of fossil fuels anddeforestation result in carbon dioxide inputs to the atmosphere, where it acts as a greenhousegas, causing harmful climatic changes.
Therefore, this is an example of processes that occur at the interface of human activities, the atmosphere and the biosphere and its study belongs to the domain of Physical Geography.
Natural Environments: The AtmosphereGG 101 – Spring 2005
Boston University
MyneniLecture 02: Introduction
Jan-21-05(4 of 11)
A Simple Model of the Earth System – The Four Great Realms
Lithosphere - All processes associated with the solid earthHydrosphere - All processes associated with waterAtmosphere - All processes associated with the gases that envelope the earthBiosphere - All processes that involve living organisms
Natural Environments: The AtmosphereGG 101 – Spring 2005
Boston University
MyneniLecture 02: Introduction
Jan-21-05(5 of 11)
Systems Approach
- Methodology to help simplify/understand complex systems (e.g., atmosphere)
- Several key components
- Reservoirs (of materials or energy) - Pathways or flows - Inputs and outputs (open vs. closed systems)
Natural Environments: The AtmosphereGG 101 – Spring 2005
Boston University
MyneniLecture 02: Introduction
Jan-21-05(6 of 11)
For example: Global Hydrologic Cycle(key component of the global climate system)
Natural Environments: The AtmosphereGG 101 – Spring 2005
Boston University
MyneniLecture 02: Introduction
Jan-21-05(7 of 11)
System Interactions and Dynamics
EquilibriumWhen interactions between subsystems exactly balance one another (what comes in goes out) Example – Thermostat
Quasi-equilibriumWhen interactions aren’t exactly balanced at one point in time, but balance out over a long time Example – Surface Temperature
FeedbacksChanges in the system that lead to further changes in the system
Positive FeedbackWhen changes in the system lead to additional changes that re-enforce the initial changeExample - Credit Cards
Negative FeedbackWhen changes in the system lead to additional changes that dampen the initial changeExample – Students Attitude and Classroom Ambience
Natural Environments: The AtmosphereGG 101 – Spring 2005
Boston University
MyneniLecture 02: Introduction
Jan-21-05(8 of 11)
Cooler temperatures
More snow cover
Less energy absorbed from the sun
Warmer temperatures
Less snow cover
More energy absorbed from the sun
Positive Feedback: Ice-Albedo Feedback
Natural Environments: The AtmosphereGG 101 – Spring 2005
Boston University
MyneniLecture 02: Introduction
Jan-21-05(9 of 11)
Space and Time Scales
Spatial scales Global – Long term climate changes Continental – El Nino Southern Oscillation (ENSO) Regional – Geographic shifts in climate regimes (e.g. dust bowl of the 1930’s) Local – Extreme events (e.g., short duration droughts; Hurricanes)
Time scales Short – Atmospheric disturbances (hourly to weekly) Seasonal – Land vegetation Interannual - ENSO Decadal – Solar influences Long scale – Ocean related Very very long scale – distribution of continents
Natural Environments: The AtmosphereGG 101 – Spring 2005
Boston University
MyneniLecture 02: Introduction
Jan-21-05(10 of 11)
Weather?
Large scale fluctuations in the atmosphere fromhour-to-hour or day-to-day
Weather systems arise mainly due to atmosphericinstabilities, the evolution of which is governedby non-linear chaotic dynamics.
That is why weather is not really predictablebeyond a week or two into the future.
Super Typhoon Lupit (26W) west of the
Philippine Islands (Nov-26-2003) as seen by the NASA’s MODIS satellite sensor.
Natural Environments: The AtmosphereGG 101 – Spring 2005
Boston University
MyneniLecture 02: Introduction
Jan-21-05(11 of 11)
Climate?
Climate is defined as averaged weather, typically defined in terms of mean and other statistical quantities (higher order moments), that measure variability over a period of time and over a geographical region (space).
Climate = What you expect,Weather = What you get.