Topic 1_Ch 3_"Behaviour of the Atmosphere"

Topic 1: Composition & Behaviour of the Atmosphere

Chapter 3: Behaviour of the Atmosphere

• Introduction

  • The kinetic theory of matter aids in understanding the characteristics of different states of matter.

  • Key Concepts:

    • All matter consists of moving molecules.

    • The phase of matter (gas, liquid, solid) depends on the attraction between molecules.

    • Temperature reflects the average kinetic energy of molecules.

The Kinetic Theory of Matter

• Phases of Matter:

  • Solids:

    • Molecules are highly attracted and can only vibrate in fixed positions.

  • Liquids:

    • Molecules have moderate attraction, allowing more freedom of movement.

  • Gases:

    • Very low attraction allows molecules to move independently.

• Fluids:

  • Gases and liquids are classified as fluids due to their ability to flow, but their behaviors differ significantly.

The Ideal Gas Law

• Relation Between Temperature, Pressure, and Density:

  • Describes how atmospheric conditions react to changes in parameters.

Boyle’s Law

• Constant Temperature:

  • When temperature remains constant, an increase in the volume results in a decrease in pressure, and vice versa.

  • Relationship: Volume and pressure are inversely proportional.

  • Equation: (PV)_time1 = (PV)_time2

Charles’ Law

• Constant Pressure:

  • When pressure is constant, an increase in temperature leads to an increase in volume.

  • Volume and temperature are directly proportional.

Constant Volume Law

• When Volume is Held Constant:

  • An increase in temperature results in an increase in pressure.

  • Pressure and temperature are directly proportional.

Air Density and the Ideal Gas Law

• Dry Air Constant (Rd):

  • Rd = 287 J ∙ kg–1 ∙ K–1

• Density of Air:

  • Density decreases with increased water vapor content.

• Virtual Temperature (Tv):

  • Represents the temperature at which dry air would have the same density as actual air.

  • Equation: Tv = T (1 + 0.61r)

Understanding Gas Behavior

• Key Properties of Gases:

  1. At constant temperature, an increase in pressure leads to an increase in density (compressibility of air).

  2. At constant pressure, increased temperature results in decreased density (warm air is less dense).

Hydrostatic Balance

• Forces in the Atmosphere:

  1. Gravity pulls downwards.

  2. Pressure Gradient Force (PGF) pushes upwards from high to low pressure areas.

• Wind Formation:

  • Motion from the PGF leads to wind creation.

• Hydrostatics:

  • Study of stationary fluids where PGF counteracts gravity.

Variations in Pressure

• Incompressible Fluid:

  • Density remains constant irrespective of depth.

• Compressible Fluid (Air):

  • Density changes with altitude.

The Hypsometric Equation

• Fundamentals:

  • Connects pressure and height; layers of air have noticeable thickness differences.

• Impact of Temperature on Thickness:

  • Thicker layers result from warmer temperatures.

Observations and Data Normalization

• Pressure Observations:

  • Shifts in height alter pressure readings; station pressure needs adjustment to sea level for comparison.

Influence of Temperature on Pressure Distribution

• Thermal Systems:

  • Thermal low-pressure systems occur from heating; high-pressure systems result from cooling.

• Dynamic Systems:

  • Dynamic low-pressure arises from cooling; high-pressure forms from warming.

Weather Maps

• Compilation and Data Collection:

  • Weather observations are synchronized globally by the WMO, covering both land and ocean.

• Data Collection Stations:

  • 10,000 land stations and around 7,000 commercial ships collect data.

Upper-air Observations

• Radiosondes:

  • Transmit essential parameters every few seconds; they float down to collect data.

• Surface Charts:

  • Illustrate sea level pressure variations with isolines (isobars) and station models.