Study Notes on Bay Area Climate and Weather

Introduction

• Shift in focus from geology to atmospheric studies in the Bay Area.

• Overview of the topics: Climate and Weather in the Bay Area.

Key Factors Affecting Bay Area Climate and Weather

• Importance of understanding factors affecting climate and weather.

• Primary factor identified: Latitude.

• B.A. falls within the mid latitude zone, specifically between 35° N and 55° N.

• Bay Area Latitude: Approximately 38° N.

• Comparison with latitudinal patterns of the Southern Hemisphere.

Latitude and Its Impact on Climate and Weather

• Solar Angle and its correlation with latitude.

  • Definition: Solar angle affects energy received from the sun.

  • Higher solar angles lead to more energy and vice versa.

  • Notable solar angles for 38° N:

    • Maximum: 75.5° (Summer Solstice).

    • Minimum: 28.5° (Winter Solstice).

  • Key Point: Higher solar angle means greater potential energy reaching the Earth's surface.

• Annual solar angle variation influences seasonality:

  • Distinction between colder winters and warmer summers in the Bay Area; this is typical of mid latitude regions.

Climograph Analysis

• Climograph reveals seasonal variation in temperature and rainfall.

• Temperature patterns:

  • Peak temperature starts in June, fluctuating thereafter.

  • Cold winters with defined warm summer months.

• Rainfall patterns:

  • Dry summers and wet winters recognized as typical in the B.A.

  • Noteworthy: Variation between mid latitude norms and patterns observed in B.A.:

    • Dry hot summers (CSB classification).

    • Wet winters contradicting other Northern Hemisphere patterns.

Climate Type Classification

• Bay Area Climate categorized under Koppen climate classification as CSB (Mediterranean climate type).

  • Characteristics of CSB climate:

    • Temperate temperature range.

    • Dry, warm summers.

  • Comparison with Mediterranean climate regions.

• Variations noted across locations (San Francisco, San Jose, Fairfield) in terms of:

  • Rainfall (San Jose being the driest).

  • Temperature variance between locations due to geographic factors.

Circulation Cells and Weather Patterns

• Overview of the Troposphere:

  • Definition: Lowest, densest layer of the atmosphere.

  • Circulation dynamics: horizontal and vertical flow.

• Major atmospheric circulation cells and their functions:

  • Hadley Cell: Tropical low-pressure system.

  • Ferrell Cell: Mid-latitude prevailing winds.

  • Polar Cell: Arctic conditions influence.

• Understanding pressure systems:

  • Low pressure (LP): air rises (Equatorial zone).

  • High pressure (HP): air descends (Subtropical high).

Seasonal Shifts and Climate Effects

• Latitudinal positioning effects during the year:

  • Pressure system movements:

    • Summer Shifts: Subtropical high moves north; increased warmth.

    • Winter Shifts: Subpolar low moves south; rainfall increases.

  • Impacts of seasonal shifts in pressure on Bay Area weather.

• Variability introduced by fluctuating positions of high and low-pressure systems.

Adverse Weather and Air Masses

• Overview of major air masses:

  • Maritime Tropical (MT): Warm, moist air over ocean, high evaporation.

  • Continental Tropical (CT): Warm, dry conditions over land.

  • Maritime Polar (MP): Cold, moist air, contributes to weather patterns but less impactful in Bay Area due to Rocky Mountain blockage.

• Key air masses affecting Bay Area:

  • Interaction between MP, MT, and CT determines weather variability.

• Relative importance of these air masses:

  • Maritime Polar being crucial for weather phenomena affecting the Bay Area.

Conclusion

• Recap of the key climatic influences in the Bay Area:

  • Latitude determines solar angles and seasonal energy reception.

  • Positioning affects large-scale atmospheric circulation and influences local weather patterns.

  • Three main air masses exert influence over weather dynamics in the region.