Chapter 8
Climatic Classification
2. What is the goal of any climatic classification system?
Answer: The goal of any climatic classification system is to summarize and simplify our conception of
the various climate types in order to better understand them. The climatic classification procedure should
have an appropriate number of classes to differentiate the climatic types without being confusing and
cumbersome. The climatic classification should minimize within group variability and maximize between
group variability.
4. What is the goal of the Köppen Climatic Classification System?
Answer: The goal of the Köppen Climatic Classification system is to delineate climate zones based on
the distribution of natural vegetation using monthly temperature and precipitation data. This classification
system is founded on the idea that most vegetation types respond strongly to temperature and moisture
variations. The Köppen system is the most widely used climatic classification system.
6. In the Köppen system, what does the third letter usually represent?
Answer: The third letter in the Köppen climatic classification system usually represents the
characteristics of summer temperatures for mesothermal and microthermal climates. The letter “a” is used
for hot summers, “b” for warm summers, “c” for mild summers, and the rare “d” for cool summers.
8. How did Köppen define “dry” when he devised the arid or “B” climatic type?
Answer: Köppen defined a “dry” B climatic type based on the relationship between evapotranspiration
and mean precipitation. A “dry” climate is one in which mean evapotranspiration exceeds mean
precipitation frequently. Regions that receive the majority of their precipitation in the summer months
will have a very different water balance than regions with a wintertime peak of precipitation. These
climatic differences will be expressed through differences in the type and distribution of natural
vegetation.
10. In what part of the world is the Holdridge Life Zones Classification most applicable? Why?
Answer: The Holdridge Life Zones Classification is most applicable in tropical areas. Although this
classification system was intended to be used for global application, it has been proven to be most useful
in ecological and alpine applications in tropical areas. The Holdridge system is ideally suited for tropical
areas because it defines life zones on their biotemperature; temperature that is related to the dormancy of
plants. This variable is the most appropriate to define the complex vegetation regimes in tropical areas.
12. How does a genetic classification system differ from an empirical classification system?
Answer: A genetic classification is used to categorize climates solely on the basis of the forcing
mechanisms that create the climate. Genetic classifications simply consider the causes involved in the
climate classification. Empirical classifications require climate data to classify the climate types based on
predetermined class boundaries. This type of classification ensures that two locations with similar climatic
conditions will be categorized in the same group. These systems are ideal in regions with high-quality and
abundant climate data and are less subjective than genetic classification methods.
© 2012 Jones and Bartlett Learning, LLC
14. What are the four types of fronts? How does each form and what are the general characteristics of
each?
Answer: A cold front forms when a colder air mass displaces a warmer air mass toward its source region.
Cold fronts are associated with a relatively narrow zone of convective cloud cover that produces brief but
intense rainfall. Warm fronts form when a warmer air mass is displacing a colder air mass poleward.
Warm fronts generally produce moderate intensity rainfall across widespread areas that last for long
durations. Stationary fronts are created when neither the cold or warm air mass is pushing the other
backward. A wide variety of weather can be found along a stationary front, but usually clouds and
prolonged precipitation are found there. The winds on both sides of a stationary front are often parallel to
the front. Occluded fronts are formed when a cold front catches up to a warm front as a midlatitude
cyclone migrates. Occluded fronts are usually associated with abundant clouds but neither intense
precipitation nor severe weather is common.
16. How would weather conditions (winds, temperature, moisture, clouds, and precipitation) change for a
location if a midlatitude cyclone tracked over it with the core of the system passing to the north of the
location?
Answer: The appearance of high cirrus clouds to the west would be the first sign of the approaching
cyclone. As the warm front progresses, the cloud deck will become thicker and more extensive until light
precipitation begins. As the warm front gets closer precipitation rates and temperatures will increases as
the winds change from an easterly to a southerly direction. The region will experience relatively warm
conditions, clear skies and southerly winds as the warm front passes over region. The approach of the cold
front is marked by cloudy conditions, a noticeable wind shift, intense precipitation and possible severe
weather. Temperatures decrease rapidly and the skies quickly clear as the winds change from a southerly
to northerly direction due to the cold frontal passage. Weather conditions generally remain cool and dry
until the next midlatitude cyclone approaches the region.
18. Why is it necessary to use cluster analysis after doing eigenvector analysis for climatic classification?
Answer: Once the climatic data have been subjected to eigenvector analysis the clustering procedure can
quantitatively group the resulting loadings and scores matrix into major climatic types. Points (stations)
will be placed into the same category whose loadings are similar to each other. Boundaries can then be
drawn to separate the different climatic regions. The eigenvector scores can be clustered to identify time
periods (months or days) that have similar temporal properties of the atmospheric variable being
analyzed, such as temperature or pressure. The researcher determines the optimal number of clusters to
select for the climatic classification.
© 2012 Jones and Bartlett Learning, LLC