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.