GEOG 14 Module 3
What Köppen climate do the following California places enjoy? Los Angeles, San Diego, San Francisco, Crescent City, Fresno, Death Valley, Tahoe?
Los Angeles, San Francisco, Crescent City, and Tahoe all enjoy a Mediterranean Koeppen climate (Csb) with mild summers. San Diego and Fresno both enjoy Steppe (BS), semiarid climates that include scrub. Death Valley enjoys a true hot Desert climate (Bwh).
What Köppen climate do the following California places enjoy? Los Angeles, San Diego, San Fransisco, Crescent City, Fresno, Death Valley, Tahoe?
Los Angeles, San Francisco, Crescent City, and Tahoe all enjoy a Mediterranean Köppen climate (Csb) with mild summer. San Diego and Fresno both enjoy Steppe (BS), semiarid climates that include scrub. Death Valley enjoys a true hot Desert climate (Bwh).
Stable Atmosphere; Fair Weather
Moist dry air parcels have adiabatic rates higher than environmental lapse rate More Dense; High Pressure < Compressional Heating < Clear (@ surface)
Keeling Curve
a graph made over the span of 50 years that shows the increase of carbon dioxide
Who was Svante Arrhenius (1859-1927)?
a. 1896: Greenhouse Effect (carbon dioxide, water vapor) b. positive radiative forcing (net gain in radiation)
Macro climate
consists of patterns on the global, regional, and landscape level
What are climate regions?
regions with similar climate characteristics
Ice cores from Dome C in Antarctica
- proxy data back to 800,000 years - change in global temp correlates with change in greenhouse gas concentrations - today, increase in temperature closely follows increase in CO2
Mauna Loa Observatory
- world's oldest continuous CO2 monitoring station - primary benchmark site for the measurement of CO2
What elements of weather and climate are used to classify climates, according to the Köppen classification system?
A - Tropical Moist Climates (not present in California - All months of the year have an average temperature above 18 degrees Celcius B - Dry Climates - Verly low precipitation levels C - Moist Mid-Latitude Climate (Mediterranean) - Mild winters D - Moist Mid-Latitude Climate (Microthermal) - Cold winters E - Polar Climates - Average monthly temperature is always less than 10 degrees Celcium H - Highland Climate - Cold winters. Often mild summers. Mountainous.
What is a climograph? What 3 characteristics are used to classify places into climate regions?
A climograph is a graph used to show annual variations and patterns in temperature and precipitation for particular weather stations in California. The three characteristics used by climographs to classify places into climate regions are commonly average monthly high and low temperatures, average monthly precipitation, and seasonality-- the annual variations in temperature and precipitation throughout the year or across seasons.
Köppen Climate Zones or Groups
A. Tropical Humid Climates B. Dry Climates* C. Mild Midlatitude Climates* D. Severe Midlatitude Climates E. Polar Climates H. Highland Climates* *California's main climate groups
Which of California's climates shows the least seasonality of temperature? Which shows the most variation or seasonality of temperature? Use the climographs in Selby or the more general climographs included in the slides.
According to Selby's climographs, Morro Bay shows to have the least seasonality of temperature. The location shown with the most variation in seasonality of temperature is White Mountain (Barcroft).
Based on the map for state-wide precipitation (see the presentation slide), which geomorphic regions discussed in the last module receive the highest amount of average annual precipitation? Which receives the lowest amount of average annual precipitation? Can you explain this pattern?
According to the map for California's state-wide precipitation, it is most likely to rain in the Northern Coast Ranges and the Southern Cascades. It is least likely for precipitation to occur in the lower Central Valley and in the Mojave Desert. The high elevation of these mountainous regions explain their heavy annual rainfalls as orographic lifting occurs in these areas of high humidity; once this dense air has moved over the mountains, it drops in temperature and dries, leaving rainshadow desert areas.
Unstable Atmosphere; Stormy Weather
Air parcel is warmer and less dense than surrounding atmosphere (@ surface) Less Dense; Low Pressure > Expansion > Cooling to the dew point; Condensation, clouds, precipitation
How do the Aleutian Subpolar Lows affect the weather and climate in California? Give an example and describe the impact of elevation.
Aleutian Subpolar lows will often display their action during the wintertime, typically through precipitation. During mid-winter, East Pacific or Hawaiian Highs will weaken and move south as the winter sun shifts in this direction. This process makes way for disruptions and polar front systems near the Aleutian Subpolar Low. Aleutian Subpolar Lows bring about low pressure, thus resulting in stormy winter weather.
What is climate change?
Any significant change in the Earth's climate over a long period.
What is climate?
Climate is defined as weather statistics for a long period of time in a certain location on the map, whereas weather refers to the state of a location's time or place. Examples of weather contributions would be how dry, rainy, windy, or sunny a place is.
What explains the diversity or range of climates in California?
Latitude is one of the contributing factors to the diversity and range of climates in California's weather system. Latitude affects California's temperature, precipitation, humidity, and radiation exposure. Distance between a particular region in California and mountain ranges or the ocean plays a role in that region's weather conditions. Elevation of specific regions affect their weather as well; increase in elevation, like in mountain ranges, pairs with a decrease in air pressure thus resulting in colder weather. Because air molecules are spread out further in areas of lower elevation, the temperature decreases.
What is a rainshadow? How do they influence weather and climate conditions in parts of California? What parts of California fall within rainshadows?
Rainshadows are results of the reverse process of orographic lifting and precipitation. Wind will blow up the side of a mountain and will come to a summit, eventually blowing down the mountain's other side. Rather than expansion in orographic lifting, the air will compress due to the weight of the above increasing air volume. Now, the air will heat up at the dry adiabatic rate of 10 degrees C/100m. Ice crystals will then melt and evaporate, lowering the air's humidity and thus causing difficulty for clouds to form. These conditions attribute to the lack of rain in these downwind mountain slopes and therefore create rainshadow areas and deserts. The Central Valley of California's midsection lies in the rainshadow of the Coast Ranges. The Modoc Plateau, right of the Southern Cascades, lies in the Klamath Mountain's rainshadow. Both the Mojave and Colorado Deserts lie in the rainshadow of the Peninsular Transverse Ranges. Basin and Range lies within the rainshadow of the Sierra Nevadas; ranges within Basin and Range form individual rainshadow areas of their own. Rainshadow has affected and currently influences the weather of California regions such as 1900's Death Valley, the driest place in the state and one of the driest in the world, where 5cm (2 inches) of rain was the average annual precipitation. Select southeastern California desert areas are equally as dry as Death Valley, all falling within the rainshadow sides of major mountain barriers.
What are Santa Ana wins? What causes them? What is their impact on California's weather and climate conditions?
Santa Ana winds are hot, dry winds that blow smog and haze toward the coast and, often, out to sea. These winds occur when wind shifts from the north to the northeast, then further east within a few days as high pressure drifts even further east to inland Nevada. California might experience Santa Ana winds blowing compressed hot air from the north when, ironically, much of the United States feel the first chill of fall and winter air masses from the north.
Which of California's climates shows the least seasonality of precipitation? Which shows the most seasonality of precipitation? Again, use the climographs in Selby or the more general climographs included in the presentation slides.
Selby's climographs display that Death Valley shows the least seasonality of precipitation with an average of 2.24 inches of rainfall a year. Crescent City, however, is shown to have the most seasonality of precipitation averaging at 70.77 inches of annual rainfall.
Describe the impact of the California current on weather and climate in the state. Which regions are most directly impacted?
The California current impacts the state's west coast as cold water flows down the Pacific Ocean, dropping the temperature of the Pacific's water.
We can identify the 4 broad climates across California: (1) Desert, (2) Steppe, (3) Mediterranean, and (4) Highland. Describe their general location and try to connect them to the geomorphic regions we have studied.
The Desert climate of California covers the southern San Joaquin Valley and southeastern California, and hotter of these desert climates are among lower desert valleys from Death Valley to the Colorado River as well as in the Coachella and Imperial Valleys. California's Steppe climates are scattered among its southern inland valleys and extreme southern coastal strip. The Mediterranean climate of cismontane California covers low and middle elevations along the coast up to its mountain slopes stretching from Oregon's border to southern California. Highland climates in California can be found only on the state's highest peaks and ridges above the tree line; when winter and spring snow melts in highland climate areas, this water will often drain into forests of lower elevations and allowing for short and harsh growing seasons.
What is a marine layer? What areas are affected?
The marine layer is the blanket of thick haze and smog trapped in the cooler surface air that flatlanders, or inhabitants of coastal stations to the west and south near sea level, witness when summer afternoon temperatures are higher in southern California mountain locations like Palomar, Julian, Idyllwild, Big Bear, Lake Arrowhead, Wrightwood, Mount Wilson, and Mount Pinos. Processes called inversions often cause marine layers as afternoon temperatures during the summer get hotter in the mountains than in the coastal plains near sea level.
Compare and contrast the temperature and precipitation patterns shown in the climographs for two coastal California cities: San Diego and Crescent City see Selby pp. 136-139 or the slides). What similarities and differences do you observe? Try to explain the similarities and differences.
The similarities between Crescent City and San Diego include their average range of temperature. These two cities experience likened January temperatures with Crescent City reaching 44 degrees fahrenheit and 55 degrees in San Diego. Their average summer temperatures are in relatively close proximity with each other as Crescent City has an August of 56 degrees fahrenheit while, during this month, San Diego will reach about 71 degrees fahrenheit. Also, according to Selby's climographs, both Crescent City and San Diego will experience little to no snowfall with snowfall in Crescent City's recorded at an average of 0.0 inches and 0.7 in San Diego. Despite what both these locations have in common, Crescent City and San Diego are located on the opposite sides of California. With Crescent City up north in the Klamath Mountains and San Diego in southern California right across from Tijuana, Mexico, these two cities could not get much further away from each other. Elevation levels of Crescent City and San Diego are much different from each other as well, as Crescent City stands at an elevation of 43 feet (13.1064 meters) while San Diego only reaches a height of 15 feet (4.572 meters). In addition, the levels of precipitation in these two cities contrast quite a bit from each other. Selby's climographs report that Crescent City will endure an average rainfall of 70.77 inches a year while San Diego will only experience an annual precipitation of about 10.13 inches.
What is orographic lifting and precipitation? Where does it occur in California?
When air mass is forced into a mountain range, it is pushed up the mountain size. As this air mass rises, the above air pressure weighing it down decreases. The air mass expands due to this lowering pressure and cools at a wet adiabatic rate of 10 degrees c/1000m. The air might then reach saturation as cooler air holds less water vapor than warmer air. Because of this property of cold air, clouds are formed while latent heat, resulting of higher-energy water vapors condensing to form lower-energy liquid water drops, is released. Release of this latent heat then leads to further up-drafting. Precipitation will follow in areas such as the Klamaths or Cascades, or the Coast Ranges or Sierra Nevada, or the Transverse Peninsular Ranges where the air mass is forced to rise along windward slopes and the greatest precipitation totals are common, thus concluding orographic lifting and precipitation. These mentioned mountain west-facing slopes will experience more rain than downwind regions or east-facing slopes.
What are the key characteristics of each in terms of temperature, precipitation and their seasonal variation or seasonality? What distinguishes them from one another?
True, hot desert climates experience precipitation that is less than half of potential evapotranspiration (the process by which water is transferred from the land to the atmosphere by evaporation from the soil and other surfaces and by transpiration from plants) and the average monthly temperature, even in the coldest months, is above freezing. Hotter desert climates have maximum average temperatures exceeding 38 degrees celsius (100 degrees fahrenheit) for a minimum of three months. Select locations with Desert climates are the only places in California that experience, though with meager totals, peak precipitation during the late summer rather than in the winter. In regards to precipitation, steppe climates experience more than half of, but still less than, potential evapotranspiration rates. Intermediate Steppe climates fall between true desert and more humid climate groups; these conditions produce sustaining grasslands and are somewhat wetter and typically cooler than California's true deserts. Mediterranean climates, including several coastal areas from central California to Mexico, might experience summers with no rainfall between the months of May and October. Air masses will have an annual battle that will normally come at the end of this drought season when soil and plants are at their driest. Due to the timing of the first Santa Ana and other down-slope winds, arriving before the first major rainfall of the season, the months of September through December bring to California some of the most hazardous fire seasons in the world. Highland climates, or tundra climates, are similar to those of the worldwide arctic or alpine class. The warmest months of these climates are often less than 10 degrees celsius, or 50 degrees fahrenheit, with bitterly cold winters. Highland winters are typical of high winds and temperatures below -18 degrees celsius, or 0 degrees fahrenheit, making for hostile locations. These harsh climates can only be found on California's highest peaks and ridges above tree lines. When winter and spring snows melt, draining water into forests and lower elevations, short and harsh growing seasons occur where weather will swing between extreme conditions in low-pressure air. At any time, brief periods of frost or violent thunderstorms might halt the summer drought.
How do high pressure systems affect the weather and climate parts of California?
Typically, high pressure makes for heavy, dense air that will sink toward California's surface, creating a heat wave. Compression heats this surface air making its parcels want to expand and rise; however, heavy and dense air parcels come and fall around those of the surface air and squeeze them together, stopping their rising and expansion. High pressure, dominating drier southern California, makes for fair weather in contrast to stormy low-pressure weather.
What do we want to understand about each climate?
Where are they located? - latitude, position on a landmass (coastal or inland? east or west coast?) What are their key characteristics? - temperature, precipitation and their seasonal variation What are the main controls on each climate? - latitude, land & water heating differences, atmospheric circulation patterns, oceanic circulation patterns, topography, elevation, storms
What are the most important controlling influences for each?
• All of California's climates fall into Köppen types B, C and H. - (Dry, Mild Midlatitude, Highland) • Not surprisingly, California's driest regions have Dry climates: - Desert (arid) - Steppe (semi-arid) • California's Desert climate regions are surrounded by transitional semi-arid Steppe climate regions. • California's coastal areas enjoy Mild Midlatitude climates. - Mediterranean (semi-arid) - Marine West Coast • California's eastern mountain ranges generally belong to Highland climate regions.
Climate Change in California
• Normal weather patterns less reliable; • Anomalous weather patterns & events more common - record-breaking temperatures (both hot and cold) occurred in past 30 years - longest drought (late 1980s - early 1990s) - record-breaking precipitation, floods, snowfall (1995, 1997, 1998) - in some areas, driest and wettest years in history • Models indicate anthropogenic (human-caused) forcing will cause 25%-100% increase in extreme wet and dry precipitation events
Steppe Climate
• Transition between desert & humid climates • Greater precipitation than deserts, but still semi-arid. • All of California's desert climate regions have these transitional climates on their margins
