1. Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 02: Introduction Jan-19-07 (1 of 14) Outline - The Four Great Realms? - Scales in Physical Geography - Systems in Physical Geography - Weather and Climate Further Reading: Chapters 01 and 02 of the text book
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8. Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 02: Introduction Jan-19-07 (8 of 14) Open and Closed Flow Systems Open Flow System - This is a flow system where there are inputs and outputs of matter and energy. Closed Flow System - This is a flow system with no input or output flows of matter. The flow of materials in the system moves endlessly in a series of interconnected paths or loops. This is also known as a cycle, or a material cycle. Any global material flow system must be closed , since only a minute amount of matter flows from Earth to space or from space to the Earth. The global carbon, nitrogen, and oxygen cycles are all closed matter flow systems. Energy flow systems are always open . All objects that are warmer than the depths of space emit radiant energy, and some fraction of that energy ultimately leaves the Earth.
9. Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 02: Introduction Jan-19-07 (9 of 14) For example: Global Hydrologic Cycle (key component of the global climate system)
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12. Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 02: Introduction Jan-19-07 (12 of 14) Time Cycles Any system can undergo a change in the rates of flow energy or matter within its pathways. Flow rates may grow faster or may slow down. These changes in activity can be reversed at intervals of time – that is, a rate can alternately speed up and slow down during a time cycle. In many natural systems, there is a rhythm of increasing and decreasing flow. The annual revolution of the Earth around the Sun generates a time cycle of energy flow in many natural systems.
13. Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 02: Introduction Jan-19-07 (13 of 14) What is 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.
14. Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 02: Introduction Jan-19-07 (14 of 14) What is 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.