THE TROPICS, ITS SOILS AND HORTICULTURE - Tropical Fruits - page 15

Fig. 2.3. Solar radiation received at the earth surface at different latitudes and an
atmospheric coef fi cient of 0.6 (Gates, 1966). Solar radiation changes signi fi cantly
between the summer and winter periods as you move away from the equator. The
data in the fi gure are for the northern hemisphere.
MAJOR TROPICAL CLIMATE TYPES
Many geographers and climatologists have classifi ed climates into zones by
temperatures (tropical, temperate and frigid zones), by vegetation or crop
requirements, precipitation, altitude, soils, human responses, or by combining
these factors. A well-recognized classifi cation system is the Köppen system,
named after the Austrian botanist and geographer, Wladimir Köppen. This
classifi cation is based on temperature, rainfall, seasonal characteristics and
the region's natural vegetation and was developed from 1870 to his death in
1940. The newer systems have most often been built upon the 1918 scheme
of the world climactic regions (Table 2.2). Another well-known modifi cation
is that of C.W. Thornthwaite (1948), who based his classifi cation on
distribution of ef ective precipitation (P/E (precipitation/evaporation) ratio),
temperature ei ciency and evapotranspiration. This led to nine moisture and
nine temperature regions. Numerous other classifi cations have been published
based upon similar criteria (Oliver and Hidore, 1984; Schultz, 2005).
The classifi cation systems of Köppen, Thornthwaite and others are
focused on the major factors (temperature, precipitation and evaporation)
that limit vegetation growth and hence horticultural production. The 18°C