2.4: Accessible Descriptions

Figure 1.1 Earth's regional climates

The continental United States is represented by a collection of overlapping photographs, each depicting a different environmental phenomenon. Alaska and Hawaii appear separately in their usual inset positions below and to the left of the mainland.

The images collectively suggest a range of climate-related hazards, including:

• Extreme heat
• Wildfires
• Forest dieback
• Flooding
• Agricultural impacts
• Drought
• Severe storms and hurricanes
• Ecosystem changes
• Melting ice

Western United States

In the Pacific Northwest and northern Rocky Mountain region:

• A large, bright white sun appears in a yellow-orange sky, suggesting extreme heat or heat waves.

Across much of the western United States:

• A large photograph shows a forest wildfire, with flames engulfing a tree and thick smoke filling the air.
• Another image depicts a landscape of dead or burned trees overlooking a body of water, suggesting forest damage from wildfire, drought, pests, or other environmental stress.

These images emphasize the increasing wildfire risk and changes in forest ecosystems.

Central United States

In the northern and central Plains:

• A photograph shows agricultural fields partially submerged, with rows of crops standing in the water.
• This suggests heavy rainfall, flooding, or waterlogged farmland.

In the southern Great Plains and Texas region:

• Aerial imagery shows cattle scattered across dry, pale-colored land, suggesting drought conditions and impacts on livestock and agriculture.

Together, these images contrast excess water in some regions with water scarcity in others.

Eastern United States

Across portions of the Northeast:

• The map is filled with an image of dense green vegetation or evergreen branches, representing forests and ecosystems that may be affected by changing climate conditions.

In the Southeast and Gulf Coast:

• A dramatic storm scene shows strong winds bending palm trees while rain and mist obscure nearby buildings.
• The image resembles a hurricane or tropical storm, with visible impacts on urban areas and coastal vegetation.

This section highlights the increasing risks posed by severe weather and coastal storms.

Alaska and Hawaii Insets

Alaska:

• The inset contains floating chunks of white ice in blue water, representing melting sea ice or glacial ice loss.

Hawaii:

• The islands are shown with small photographic textures that are difficult to distinguish individually but contribute to the overall environmental theme.

Figure 1.1.1 Earth's Latitudes

The image shows a circular view of the Earth focused on the Eastern Hemisphere, including Europe, Africa, and parts of Asia. The background is black, and the continents are outlined in thin, light-colored lines. The globe appears centered, with latitude markings prominently displayed across its surface.

Geographic Content

Visible landmasses include:

• The continents of North America and Europe lie entirely in the northern hemisphere.
• North America lies between 7°N and 85°N, while Europe lies between 35°N and 72°N latitudes.
• Meanwhile, Africa, Asia and South America extend to both sides of the equator.
• Africa extends from 37°N to 35°S, Asia from 10°S to 80°N, and South America from 12°N to 55°S.

Latitude Markings

Across the center of the globe, large white text labels the lines of latitude. These appear diagonally arranged from top to bottom and include:

75° (near the top of the globe, Northern Hemisphere), 60°, 45°, 30°, 15°, 0° – EQUATOR (centered across the middle, clearly labeled “EQUATOR”), 15° (Southern Hemisphere), 30°, 45° (near the bottom edge).

Figure 1.1.4: Sunlight When the Sun is Over the Equator

Diagram of Earth showing how sunlight hits different parts of the planet. The circle represents Earth, with "NP" (North Pole) at the top, "SP" (South Pole) at the bottom, and the Equator marked across the center. Two orange sunlight beams approach from the right. One beam hits the Equator directly, showing concentrated energy in a small area. The other beam hits Earth's upper atmosphere near the North Pole at an angle, spreading the same amount of sunlight over a larger area. This demonstrates why equatorial regions are warmer, and polar regions are colder.

Figure 1.1.5: Global Annual Average Air Temperatures

The image is a global map displaying the annual mean temperature across the Earth’s surface. The continents are shown with thin black outlines over a continuous color gradient representing temperature. The map uses an oval (Robinson-style) projection showing all continents. Below the map is a horizontal color scale (legend) labeled in both degrees Fahrenheit (°F) and degrees Celsius (°C). The title centered beneath the legend reads: “Annual Mean Temperature.”

Color Scale and Temperature Range

The legend shows temperatures ranging from:

• −50°C (−40°F) at the coldest end
• To 30°C (86°F) at the warmest end

Color progression from coldest to warmest:

• Light lavender to pink (extreme cold)
• Cyan (light blue)
• Dark red (hottest)

Both Celsius and Fahrenheit values are displayed along the scale:

• Celsius appears along the bottom (−50 to 30)
• Fahrenheit appears along the top (−40 to 80+)

Temperature Patterns by Region

Equatorial Regions (Hottest Areas)

• Central Africa
• Northern South America (Amazon Basin)
• Southeast Asia
• Northern Australia

These areas are shown in red to dark red, indicating average annual temperatures near 25–30°C (77–86°F).

Subtropical Deserts (Very Hot Areas)

• Sahara Desert (North Africa)
• Arabian Peninsula
• Parts of inland Australia

These regions are among the hottest on the map, shown in dark red, indicating some of the highest annual mean temperatures globally.

Temperate Regions (Moderate Temperatures)

• Most of the United States
• Southern Europe
• Southern South America
• Parts of China and Japan

These areas are shown in green to yellow, representing moderate average temperatures around 5–20°C (40–70°F).

Cold Regions

• Northern Canada
• Greenland
• Northern Europe
• Siberia

These regions appear in blue to dark blue, indicating average annual temperatures below freezing (below 0°C / 32°F).

Polar Regions (Coldest Areas)

• Antarctica
• Arctic Ocean region

These areas appear in purple, magenta, and light lavender, representing extreme cold, approaching −50°C (−58°F) in Antarctica.

Overall Pattern

The map shows a clear latitudinal temperature gradient:

• Warmest temperatures cluster around the Equator.
• Temperatures gradually decrease as you move toward the poles, north or south.
• Antarctica in the Southern Hemisphere is the coldest region overall.
• Land areas generally show more temperature variation than oceans.

Figure 1.1.6: Earth's Orbit Around the Sun

A diagram shows Earth’s orbit around the Sun, illustrating how the tilt of Earth's axis causes seasonal changes. The Sun is at the center with four labeled Earth positions around it, each representing a different season in both hemispheres.

• June 20/21 (top left): Earth's North Pole is tilted toward the Sun. The Northern Hemisphere receives the most direct sunlight, leading to summer there. The Southern Hemisphere receives less sunlight, resulting in winter.
• September 22/23 (bottom left): Earth's axis is not tilted toward or away from the Sun. Both hemispheres receive roughly equal sunlight. This marks the autumn equinox in the Northern Hemisphere and the spring equinox in the Southern Hemisphere.
• March 20 (top right): Similar to September, sunlight is evenly distributed between hemispheres. It is the spring equinox in the Northern Hemisphere and autumn equinox in the Southern Hemisphere.
• December 21/22 (bottom right): Earth's South Pole is tilted toward the Sun. The Southern Hemisphere receives the most direct sunlight and experiences summer, while the Northern Hemisphere receives less sunlight and experiences winter.

Each Earth in the diagram shows a consistent tilt in its axis. Seasons in the Northern Hemisphere are labeled in yellow, and corresponding Southern Hemisphere seasons are labeled in lavender. A red arrow shows Earth’s orbital direction around the Sun.

Figure 1.1.7: Conditions in June

Diagram of Earth tilted on its axis, showing how sunlight reaches different latitudes. The Earth is drawn as a circle tilted to the right. The North Pole (NP) is at the top, the South Pole (SP) is at the bottom, and the Equator is labeled in the center. Two additional latitude lines are shown: 23.5 degrees North (Tropic of Cancer) and 23.5 degrees South (Tropic of Capricorn).

Three horizontal orange bars labeled “Sunlight Beam” enter from the right, representing sunlight:

• The top sunlight beam fully covers the North Pole and the region around 23.5°N, showing that the Arctic is in continuous sunlight—experiencing 24 hours of daylight.
• The middle beam strikes the Equator directly, indicating the highest solar energy concentration in that region.
• The bottom beam misses the South Pole, leaving it in shadow. This shows the Antarctic is in continuous darkness, experiencing 24 hours of night.

This diagram illustrates how Earth's axial tilt affects the distribution of sunlight at the June solstice, causing one hemisphere to experience continuous daylight while the opposite hemisphere has continuous darkness.

Figure 1.1.8: Conditions in December

Diagram of Earth tilted on its axis to illustrate sunlight distribution during the December solstice. Earth is shown as a circle tilted to the left. Labels mark the North Pole (NP) at the top, the South Pole (SP) at the bottom, and the Equator across the middle. Two additional latitude lines are labeled: 23.5 degrees North (Tropic of Cancer) and 23.5 degrees South (Tropic of Capricorn).

Three orange horizontal bands labeled “Sunlight Beam” enter from the right, representing incoming solar radiation:

• The top sunlight beam does not reach the North Pole, indicating that the Arctic Circle is in full darkness, with 24 hours of night.
• The middle beam hits the Equator, showing balanced solar exposure at this latitude.
• The bottom beam directly hits the South Pole, demonstrating that the Antarctic Circle is fully illuminated, with 24 hours of daylight.

This diagram illustrates that at the December solstice, the Southern Hemisphere is tilted toward the Sun, resulting in summer and longer days. The Northern Hemisphere is tilted away from the Sun, experiencing winter and shorter days, including polar night conditions near the Arctic Circle.

Figure 1.2.1: Average monthly temperature in Iquitos, Peru

The image is a line graph showing the average monthly temperature in Iquitos, Peru across the 12 months of the year. The chart displays temperature in both degrees Fahrenheit (°F) and degrees Celsius (°C) on the vertical axis. The horizontal axis shows the months labeled numerically from 01 (January) to 12 (December). A red line with circular markers represents the monthly average temperature. A light red shaded band surrounds the line, indicating the typical temperature range (variation around the average).

Axes and Scale

Horizontal Axis (X-axis)

• Labeled: “Month of the year.”
• Months shown numerically from 01 to 12

Vertical Axis (Y-axis)

Two temperature scales appear on the left:

• Celsius (°C) scale ranging from 0°C to 40°C
• Fahrenheit (°F) scale ranging from 32°F to 104°F
• Tick marks appear at regular 5°C (approximately 9°F) intervals.

Temperature Pattern Throughout the Year

The graph shows very little seasonal variation. Temperatures remain consistently warm year-round. Approximate monthly averages:

• January–March: Around 26°C (79°F)
• April–May: Slight gradual decrease toward 25°C (77°F)
• June–July: Lowest point of the year, approximately 24–25°C (75–77°F)
• August–October: Gradual increase back to about 26–27°C (79–81°F)
• November–December: Slight decrease but remains near 26°C (79°F)

Range (Shaded Area)

The light red shaded region around the line suggests modest variability in temperatures:

• Upper range appears close to 29–30°C (84–86°F)
• Lower range appears around 22–23°C (72–73°F)
• The total annual variation in average temperature is small—approximately 2–3°C (3–5°F).

Key Takeaways

• Iquitos has a tropical climate with consistently high temperatures year-round.
• There is no pronounced winter or summer season.
• The warmest months appear around September–October.
• The coolest months appear around June–July.
• Overall annual temperature variation is minimal.

Figure 1.2.2 Average monthly temperature in San Jose, CA

The image is a line graph showing the average monthly temperature in San Jose, California, over the course of 1 year. The horizontal axis displays the months, numbered from 01 (January) to 12 (December). The vertical axis shows temperature in both degrees Celsius (°C) and degrees Fahrenheit (°F). A red line with circular markers represents the average monthly temperature. A light red-shaded band around the line indicates the typical temperature range (the variation around the monthly average).

Axes and Scale

Horizontal Axis (X-axis)

• Labeled: “Month of the year.”
• Months shown numerically from 01 through 12

Vertical Axis (Y-axis)

Two temperature scales appear on the left:

• Celsius (°C) scale from 0°C to 30°C
• Fahrenheit (°F) scale from 32°F to 86°F

Tick marks appear at regular 5°C (approximately 9°F) intervals.

Monthly Temperature Pattern

The graph shows a clear seasonal variation typical of a Mediterranean climate. Approximate monthly averages:

• January: About 10°C (50°F)
• February: About 11°C (52°F)
• March: About 13°C (55°F)
• April: About 14°C (57°F)
• May: About 16°C (61°F)
• June: About 18°C (64°F)
• July: About 20°C (68°F)
• August: About 20°C (68°F)
• September: About 21°C (70°F) (warmest month)
• October: About 17–18°C (63–64°F)
• November: About 13°C (55°F)
• December: About 10°C (50°F)

Seasonal Trends

• Temperatures gradually increase from winter through late summer.
• The warmest period occurs in July through September.
• Temperatures decline steadily in autumn.
• Winter months (December–February) are the coolest but remain mild compared to colder continental climates.
• The annual variation between the winter and late-summer averages is approximately 10–11°C (18–20°F).

Temperature Range (Shaded Area)

The light red shaded band indicates variability:

• Winter temperatures range roughly from 6–15°C (43–59°F).
• Summer temperatures range roughly from 15–28°C (59–82°F).
• The shaded band is widest during summer months, indicating greater daily variation.

Figure 1.2.3 Average monthly temperature in Tromsø, Norway

The image is a line graph showing the average monthly temperature in Tromsø, Norway, across the 12 months of the year. The horizontal axis displays months, numbered from 01 (January) to 12 (December). The vertical axis shows temperature in both degrees Celsius (°C) and degrees Fahrenheit (°F). A red line with circular markers represents the monthly average temperature. A light red shaded band around the line indicates typical variability around each monthly average. A thin horizontal black line across the graph marks 0°C (32°F), clearly indicating the freezing point of water.

Axes and Scale

Horizontal Axis (X-axis)

• Labeled: “Month of the year.”
• Months shown numerically from 01 to 12

Vertical Axis (Y-axis)

Two temperature scales appear on the left:

• Celsius (°C) scale from approximately −20°C to 20°C
• Fahrenheit (°F) scale from approximately −4°F to 68°F

Tick marks appear at regular 5°C (9°F) intervals.

Monthly Temperature Pattern

The graph shows strong seasonal variation typical of a high-latitude subarctic climate. Approximate monthly averages:

• January: About −10°C (14°F)
• February: About −9°C (16°F)
• March: About −6°C (21°F)
• April: About −2°C (28°F)
• May: About 3°C (37°F)
• June: About 8°C (46°F)
• July: About 12°C (54°F) (warmest month)
• August: About 11°C (52°F)
• September: About 7°C (45°F)
• October: About 0°C (32°F)
• November: About −6°C (21°F)
• December: About −9°C (16°F)

Seasonal Trends

• Temperatures remain below freezing from approximately October through April.
• The coldest months are January and February.
• Temperatures gradually rise in spring, crossing above freezing in May.
• The warmest period is short, centered around July.
• Temperatures decline rapidly after September, dropping below freezing again in October.
• The total annual temperature range is approximately 22°C (40°F) between winter minimum and summer maximum.

Temperature Range (Shaded Area)

The light red shaded band indicates variability around the monthly average:

• Winter ranges extend lower, suggesting frequent very cold days.
• Summer variability is narrower but still cooler than in temperate or tropical regions.
• Even in peak summer, average temperatures remain relatively mild.

Figure 1.2.4: The Climate Zones on Earth

The image is a labeled illustration of Earth as a three-dimensional globe, centered on the Americas. Several major lines of latitude are drawn across the globe and labeled. These lines divide the Earth into three main climate zones in each hemisphere: Arctic (polar), Temperate, and Tropical zones. The oceans are colored blue, and the continents are shown in light green. The background is black.

Labeled Lines of Latitude

Five key latitude lines are shown:

Arctic Circle (67° North)

• Drawn near the top of the globe.
• Encircles the high northern latitudes.
• Marks the southern boundary of the Arctic Zone.

Tropic of Cancer (23° North)

• Drawn in yellow.
• Located north of the Equator.
• Marks the northern boundary of the Tropical Zone.

Equator (0° Latitude)

• Drawn in red.
• Runs horizontally across the center of the globe.
• Divides Earth into the Northern and Southern Hemispheres.

Tropic of Capricorn (23° South)

• Drawn in yellow.
• Located south of the Equator.
• Marks the southern boundary of the Tropical Zone.

Antarctic Circle (67° South)

• Drawn near the bottom of the globe.
• Marks the northern boundary of the Antarctic (southern polar) Zone.

Climate Zones Identified

The globe is divided into horizontal bands:

1. Arctic Zone

• Located north of the Arctic Circle (67° N).
• Labeled near the top of the globe.
• Characterized by very cold temperatures and polar conditions.

2. Northern Temperate Zone

• Located between the Arctic Circle (67° N) and the Tropic of Cancer (23° N).
• Characterized by moderate seasonal variation.

3. Tropical Zone

• Located between the Tropic of Cancer (23° N) and the Tropic of Capricorn (23° S).
• Crosses the Equator.
• Characterized by warm temperatures year-round.
• Labeled on both sides of the globe.

4. Southern Temperate Zone

• Located between the Tropic of Capricorn (23° S) and the Antarctic Circle (67° S).
• Also characterized by moderate seasonal variation.

5. Antarctic (Southern Arctic) Zone

• Located south of the Antarctic Circle (67° S).
• Characterized by polar conditions and very cold temperatures.

Figure 1.3.1 A map of the world's rainforests

The image is a global map showing the distribution of tropical rainforests. The continents are displayed in light gray, and rainforest regions are highlighted in dark green. Several dashed horizontal lines mark key lines of latitude: 66.3° North, 23.5° North, the Equator, 23.5° South, and 66.3° South. The map emphasizes that tropical rainforests are concentrated near the Equator, within the band between the Tropic of Cancer (23.5° N) and the Tropic of Capricorn (23.5° S).

Latitude Markers

Five dashed horizontal latitude lines are labeled:

• 66.3° N (Arctic Circle)
• 23.5° N (Tropic of Cancer)
• Equator (0°)
• 23.5° S (Tropic of Capricorn)
• 66.3° S (Antarctic Circle)

The rainforest regions appear almost entirely between 23.5° N and 23.5° S.

Major Rainforest Regions Highlighted

1. South America (Amazon Basin)

• The largest continuous dark green area appears in northern South America.
• Covers much of Brazil and extends into Peru, Colombia, Venezuela, Ecuador, Bolivia, and surrounding countries.
• Centered on the Equator.
• This represents the Amazon Rainforest, the largest tropical rainforest in the world.

2. Central America

• A narrow band of green runs through southern Mexico and into Central American countries such as Guatemala, Costa Rica, and Panama.
• Connects northward from the Amazon region.

3. Central and West Africa

• A large dark green region appears around the Equator in central Africa.
• Covers parts of the Democratic Republic of the Congo, Republic of the Congo, Gabon, Cameroon, and neighboring countries.
• Represents the Congo Basin rainforest.

4. Southeast Asia

• Extensive green areas appear in:
  • Southern India and Sri Lanka
  • Mainland Southeast Asia
  • The Malay Peninsula
  • Indonesia
  • The Philippines
  • Papua New Guinea

This region is part of the third major global concentration of tropical rainforest.

5. Madagascar

• A smaller green area appears along Madagascar's eastern coast, off the southeast coast of Africa.

Figure 1.3.2 A map of the world's deserts

The image is a global map showing the distribution of the world’s major desert regions. Continents are displayed in light gray with subtle shading. Desert areas are highlighted in bright orange. Dashed horizontal lines mark important latitudes: 66.3° North, 23.5° North (Tropic of Cancer), the Equator, 23.5° South (Tropic of Capricorn), and 66.3° South. The map shows that most deserts occur near 23.5° North and 23.5° South, though some extend into higher latitudes.

Latitude Reference Lines

Five dashed lines appear across the map:

• 66.3° N (Arctic Circle)
• 23.5° N (Tropic of Cancer)
• Equator (0°)
• 23.5° S (Tropic of Capricorn)
• 66.3° S (Antarctic Circle)

Most desert regions cluster near the Tropics rather than near the Equator.

Major Desert Regions Highlighted

North America

• Southwestern United States and northern Mexico (including areas such as the Mojave, Sonoran, and Chihuahuan deserts).
• Located near and just north of 23.5° N.

South America

• A narrow strip along the west coast (the Atacama Desert in Chile and Peru).
• A large desert region in southern Argentina (Patagonian Desert), extending farther south than most tropical deserts.

Africa

• A vast continuous region across North Africa, representing the Sahara Desert, centered around 23.5° N.
• Smaller desert areas in southwestern Africa (the Namib Desert) and southern Africa (the Kalahari region).

Middle East and North Africa

• The Arabian Peninsula extends eastward from the Sahara across Saudi Arabia and surrounding regions.

Central and East Asia

• A large desert region in Mongolia and northern China (Gobi Desert).
• Additional arid regions extend westward into Central Asia.

Australia

• A broad desert region across central Australia, centered near 23.5° S.

Figure 1.3.3 A Map of Global Ocean Currents

The image is a world map in the Robinson projection showing the major global ocean currents. Landmasses are shaded light tan, oceans are light blue-gray, and currents are represented by directional arrows.

• Warm currents are shown in red arrows.
• Cold currents are shown in blue arrows.
• Some neutral or connecting flows appear in black.
• Latitude reference lines are shown at approximately 60°, 30°, 0° (Equator), −30°, and −60°.
• A legend at the bottom indicates red for warm currents and blue for cold currents.

Major Currents by Ocean Basin

Atlantic Ocean

Warm Currents (Red):

• Gulf Stream: Flows northward along the eastern United States, then northeast toward Europe.
• Brazil Current: Flows southward along the east coast of South America.
• North Atlantic Drift: Extension of the Gulf Stream moving toward northwestern Europe.
• Norwegian Current: Continues warm water into the Arctic region.

Cold Currents (Blue):

• Labrador Current: Flows southward from the Arctic along eastern Canada.
• Canary Current: Flows southward along northwest Africa.
• Benguela Current: Flows northward along southwest Africa.

The Atlantic shows a large clockwise circulation (gyre) in the Northern Hemisphere and a counterclockwise circulation in the Southern Hemisphere.

Pacific Ocean

Warm Currents (Red):

• Kuroshio Current: Flows northward along the east coast of Japan.
• East Australia Current: Flows southward along eastern Australia.
• North Pacific Drift: Moves eastward across the northern Pacific.

Cold Currents (Blue):

• California Current: Flows southward along the west coast of North America.
• Peru (Humboldt) Current: Flows northward along the west coast of South America.
• Oyashio Current: Flows southward from the Arctic toward Japan.
• West Australia Current: Flows northward along Western Australia.

The Pacific also shows circular gyres:

• Clockwise in the Northern Hemisphere
• Counterclockwise in the Southern Hemisphere

Indian Ocean

Warm Currents:

• Mozambique Current and related flows moving southward along southeast Africa.
• South Equatorial flows across the basin.

Cold Currents:

• West Australia Current along Western Australia.

The Indian Ocean circulation reverses seasonally in parts due to monsoon winds (not explicitly labeled but implied by current structure).

Equatorial Currents

Across all three major oceans:

• North Equatorial Current flows westward just north of the Equator.
• South Equatorial Current flows westward just south of the Equator.
• Equatorial Countercurrent flows eastward between them.

These currents form part of the tropical circulation system.

Southern Ocean

• The Antarctic Circumpolar Current flows continuously eastward around Antarctica.
• The Antarctic Subpolar Current also circles Antarctica.

These currents connect the Atlantic, Pacific, and Indian Oceans.

Figure 1.3.4 The Rain Shadow Effect

The image is a cross-sectional diagram illustrating the rain shadow effect. It shows a body of water on the left, a mountain in the center, and dry land on the right. Arrows indicate air movement, and text at the top reads: “Rising Air Cools and Condenses.” The diagram demonstrates how mountains affect precipitation patterns by causing moist air to rise, cool, and lose moisture before descending as dry air on the opposite side.

Left Side: Ocean and Moist Air (Windward Side)

• A blue body of water appears on the far left.
• Arrows point from the ocean toward the mountain, indicating moist air moving inland.
• As the air reaches the mountain slope, arrows curve upward, indicating that the air is being forced to rise.
• Blue dots within the rising air represent water vapor and condensation.
• A large gray cloud forms above the mountain slope.
• The text “Rising Air Cools and Condenses” appears above the cloud, indicating that as air rises, it cools and water vapor condenses into clouds and precipitation.
• This side of the mountain is called the windward side, where precipitation occurs.

Mountain Peak

• The mountain is shown in tan color.
• The upper portion of the peak has a small white area, possibly representing snow.
• The cloud sits above the windward slope near the peak.

Right Side: Dry Descending Air (Leeward Side)

• On the right side of the mountain, arrows point downward.
• There are no blue dots or clouds on this side.
• The land appears dry, devoid of vegetation or water.
• The absence of precipitation indicates dry conditions.
• This side of the mountain is called the leeward side, also known as the rain shadow region.

This map depicts the average annual precipitation across parts of Northern California, including the San Francisco Bay Area, based on data collected from 1900 to 1960. The geographic region extends from the coastline near San Francisco and Santa Cruz inland to Livermore, Tracy, and parts of the Central Valley.

Figure 1.3.5 Annual Precipitation over the San Francisco Bay Area

This map depicts the average annual precipitation across parts of Northern California, including the San Francisco Bay Area, based on data collected from 1900 to 1960. The geographic region extends from the coastline near San Francisco and Santa Cruz inland to Livermore, Tracy, and parts of the Central Valley.

Map Overview:

• City names such as San Francisco, Oakland, San Jose, Fremont, Sunnyvale, Santa Cruz, and Livermore are labeled on the map for spatial reference.
• The base map uses colored contours to indicate zones of average annual precipitation in inches.
• The map legend on the right categorizes precipitation into 13 ranges, from 3–4 inches up to 125 inches per year.

Precipitation Ranges and Patterns:

The color-coded contour regions represent the following precipitation ranges (in inches):

• 3–4
• 5–6
• 7–8
• 9–10
• 11–15
• 16–20
• 21–25
• 26–30
• 31–50
• 51–125

Key patterns:

• Lowest precipitation areas (3–10 inches per year) are concentrated in valleys and interior lowlands, especially near San Jose, Fremont, and parts of the East Bay.
• Moderate precipitation zones (15–25 inches) appear in much of the San Mateo Peninsula, Redwood City, and parts of the inland hills near Livermore and Concord.
• Higher precipitation zones (over 30 inches) are found along the coastal mountains, including the Santa Cruz Mountains west of San Jose and near Santa Cruz and parts of the coastal Pacific slope.
• A small area near Big Basin or the Santa Cruz Mountains may reach over 50 inches per year.

Figure 1.3.6: Topography of the San Francisco Bay Area

This is a topographic map of central coastal California, focusing on the San Francisco Bay Area and adjacent terrain. The map uses shaded relief to represent elevation and terrain texture, but does not include contour lines, colors, or elevation labels beyond land shading.

Geographic Scope:

• Several prominent cities are labeled, including San Francisco (located in the northwest corner of the map, near the ocean), San Jose (in the center of the map, inland from the bay), Santa Cruz (in the southwest portion of the map, near the coast), and the Pacific Ocean to the west.
• The San Francisco Bay is visible, extending eastward and splitting into multiple channels.

Topographic Features:

• The Santa Clara Valley, where San Jose is located, is surrounded by mountainous terrain.
• The Santa Cruz Mountains lie west of San Jose and extend southward toward Santa Cruz.
• The Diablo Range lies to the east of the Santa Clara Valley.
• The elevated terrain is represented by darker-shaded areas that form ridges and valleys.
• Lowland valleys and plains are shown in lighter shading and are mainly located around San Jose and east of San Francisco Bay.