Lecture 2: Weather and Climate 19/03

Introduction

  • Greeting and opening statements.

  • Importance of revisiting previous discussions for tutorial preparation.

Contour Lines and Pressure Systems

  • High Pressure vs Low Pressure Regions

    • High Pressure: Marked by higher values (e.g., "1016") on maps (usually associated with clear weather).

    • Low Pressure: Indicated by enclosed circles on maps (usually associated with storms).

  • Geostrophic Approximation

    • Describes the relationship between pressure gradients and the Coriolis force.

    • Without Earth's rotation, air flows directly from high to low pressure; however, due to rotation, air moves parallel to isobars (lines of constant pressure).

    • Winds follow isolines (isobars) rather than moving directly from high to low pressure.

  • Wind Speed and Direction

    • Closer isobars indicate stronger winds (represented by larger arrows).

    • Isobars farther apart indicate weaker winds (smaller arrows).

    • In the Southern Hemisphere, anticyclones (high pressure systems) flow anticlockwise.

    • Low pressure systems flow clockwise.

  • Visualizing Wind Patterns

    • With given isobar maps, students can sketch wind directions based on isobar spacing and identify high and low pressure regions.

    • Notable that winds around Antarctica predominantly flow from west to east due to geographical conditions.

Key Concepts for Tutorial

  • Understand the basics of isobars and their relation to wind patterns.

  • Ability to interpret isobar maps and depict wind directions accordingly.

  • General fact: low-pressure systems connect to strong winds due to isobars being closely packed.

Southern Ocean Winds

  • Analysis of Winds

    • Southern Ocean is recognized as storm center of the world, with intense, localized wind patterns developed around Antarctica.

    • During storms, cold dense air spirals in towards Antarctica.

  • Catabolic Flows

    • Definition: a type of cold air drainage that flows down slopes in Antarctica.

    • Air moves from high altitudes to lower altitudes due to gravity, creating windy conditions near the coast.

    • Significance: air density contributes to strong winds near coastal regions, particularly where sharp topographical gradients occur.

Implications of Circumstances

  • Anticipation of stormy conditions around the Antarctic coastline due to continual air circulation patterns.

  • Catabolic flows play a crucial role in forming local weather conditions.

Historical Context of Meteorological Observations

  • Historical example of Mawson's expedition demonstrating the effects of poor site selection leading to excessive winds.

  • Recognition that certain locations were affected adversely by natural topography and wind patterns.

Anticipating Future Climate Changes

  • Review of the Intergovernmental Panel on Climate Change (IPCC) and its findings on climate change.

    • The most significant scientific effort focused on climate change globally.

    • Strong winds around the coast of Antarctica have increased significantly in the last few decades due to climate change.

  • Projected Changes in Storm Patterns

    • Future projections indicate winds around Antarctica will become even stronger due to climate changes.

    • Previous data depicting changes from 1985 to 2015 suggests increased storm activity.

Temperature Trends

  • Examination of global temperature increases, noting that New Zealand has experienced a rise of approximately 1.3°C compared to historical averages.

  • Discussions regarding thresholds for climate action (1.5°C as critical limit).

  • Observations indicate an accelerated rate of temperature change in recent years, raising concerns about future climate scenarios.

Limitations of Current Meteorological Data

  • Data measurements historically insufficient across Antarctica leading to gaps in understanding climatic conditions.

    • Example given about the small number of weather stations initially established in Antarctica compared to those in New Zealand.

  • Importance of Continued Research

    • Calls for more investment into climate measurement initiatives to gather comprehensive data.

Summary of Spatial Temperature Variability

  • Overview depicting how temperature changes differ by latitude, indicating mid-latitudes and polar regions experience more significant alterations than tropical areas.

Conclusions

  • Recap of the correlation between isobars and wind strength/direction clearance for upcoming tutorial exercise.

  • Encouragement to explore further inquiries and a reminder of the tutorial date.

  • Final thoughts highlight the relationship between strong winds, storms surrounding Antarctica, and climate change induced shifts in weather patterns.