1. Natural Environments: The Atmosphere GG 101 – Spring 2005 Boston University Myneni Lecture 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

2. Natural Environments: The Atmosphere GG 101 – Spring 2005 Boston University Myneni Lecture 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?) with emphasis on natural and physical systems.

3. Natural Environments: The Atmosphere GG 101 – Spring 2005 Boston University Myneni Lecture 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 and deforestation result in carbon dioxide inputs to the atmosphere, where it acts as a greenhouse gas, 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.

4. Natural Environments: The Atmosphere GG 101 – Spring 2005 Boston University Myneni Lecture 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 earth Hydrosphere - All processes associated with water Atmosphere - All processes associated with the gases that envelope the earth Biosphere - All processes that involve living organisms

5. Natural Environments: The Atmosphere GG 101 – Spring 2005 Boston University Myneni Lecture 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)

6. Natural Environments: The Atmosphere GG 101 – Spring 2005 Boston University Myneni Lecture 02: Introduction Jan-21-05 (6 of 11) For example: Global Hydrologic Cycle (key component of the global climate system)

7. Natural Environments: The Atmosphere GG 101 – Spring 2005 Boston University Myneni Lecture 02: Introduction Jan-21-05 (7 of 11) System Interactions and Dynamics Equilibrium When interactions between subsystems exactly balance one another (what comes in goes out) Example – Thermostat Quasi-equilibrium When interactions aren’t exactly balanced at one point in time, but balance out over a long time Example – Surface Temperature Feedbacks Changes in the system that lead to further changes in the system Positive Feedback When changes in the system lead to additional changes that re-enforce the initial change Example - Credit Cards Negative Feedback When changes in the system lead to additional changes that dampen the initial change Example – Students Attitude and Classroom Ambience

8. Natural Environments: The Atmosphere GG 101 – Spring 2005 Boston University Myneni Lecture 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

9. Natural Environments: The Atmosphere GG 101 – Spring 2005 Boston University Myneni Lecture 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

10. Natural Environments: The Atmosphere GG 101 – Spring 2005 Boston University Myneni Lecture 02: Introduction Jan-21-05 (10 of 11) Weather? Large scale fluctuations in the atmosphere from hour-to-hour or day-to-day Weather systems arise mainly due to atmospheric instabilities, the evolution of which is governed by non-linear chaotic dynamics. That is why weather is not really predictable beyond 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.

11. Natural Environments: The Atmosphere GG 101 – Spring 2005 Boston University Myneni Lecture 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.