The
Year
of Sun and Rain
Cloudbridge
is
located at about 9 degrees north of the equator, in the tropics, so
does not suffer the drastic seasonal temperature changes that
characterize the temperate and cold zones. Instead of the cold
winter and warm summer familiar to Europeans and North Americans, Costa
Rica has a rainy season (from mid-May to end-November, roughly) and dry
season (from December to April).
Temperatures
Tropical temperatures are fairly
constant all year round: instead of varying by
season, they vary with altitude. Cloudbridge, at about 1700 meters
(5577 feet), enjoys a cooler temperature than the coast. The
average temperature is fairly constant all year round. During the day
it varies by about 10 degrees centigrade, from about 15ºC (59ºF) at night
to about 25ºC (77ºF) in the day after several
hours of sunshine. By comparison, in the lowlands the daily range is
approximately
20ºC
to 30ºC (68ºF
to 86ºF).
 Winds
Because Costa
Rica is located in the northern hemisphere, its climate is
influenced by the dominant north easterly trade winds. The country is
too far
south to be affected by hurricanes, except rarely. Cloudbridge,
sheltered north and south by mountain ridges, is sheltered
from the strong winds that swirl around the peaks. Cerro Ventisqueros,
visible from Casa Amanzimtoti, takes its name from the high winds that
twist about it.
Rainfall:
Pacific versus Caribbean
The mountain
ranges that run down the center of the country create two distinct
rainfall systems.The Pacific (often called tropical) side is
characterised by
a well-defined dry season,while the Caribbean (characterized as
equatorial), with the permanent influence of the north easterly trade
winds, has no dry season.
On the Caribbean side, the coast lowlands and northern plains
experience a notable decrease of rainfall during March and April and
sometimes September, while on the mountains and slopes exposed to the
trade winds it can rain all year long without appreciable interruption.
Little
Summers
Cloudbridge is
on the Pacific side of the Talamanca mountain range. The climate of the
Pacific is marked by the presence of a "dry" season that lasts for four
months (and more in some zones). At Cloudbridge, there is no pure dry
season -- it rains, at least for an hour or two, almost every day. The
reason lies in the height of the Talamanca mountains. Further north,
the warm moist air driven westward by the
trade winds
loses its moisture as it crosses the cordilleras and the resulting dry
air gusts down the Pacific slopes drying out
everything in its path. With such low moisture content, few clouds form
to block the sunshine and the prevailing winds keep Pacific breezes
from bringing moisture onshore, thus, further promoting the dryness.
The southern half of the Pacific slope is not
normally as strongly influenced by these effects because
the lofty Talamanca mountain range blocks the drying winds to
some degree, allowing moisture to be brought in from the Pacific
Ocean and causing occasional showers even in the dry season.
As the trade wind belt moves northward in response
to
global climatic conditions (principally, the angle of the sun and area
of greatest surface heating), Costa Rica enters its rainy season as
moist air flows in from both oceans and convection currents cause
showers to occur. At Cloudbridge, rain falls almost every day, starting
in the early afternoon -- but occasionally one experiences heavy rain
lasting two days or more when
air from the Pacific, being drawn in continuously towards a
hurricane-related extreme
low pressure center out in the Caribbean, is backed up against the
Pacific-facing slopes of the cordilleras and drops its moisture. We
keep rainfall records at Cloudbridge -- see the Research section of
this web site.
Blessedly, the rainy period is interrupted by "veranillos," or little
summers.
The veranillos last for one to two weeks, almost always in July, when
precipitation decreases considerably in all the Pacific Zone. When one
occurs early (end of June), its known popularly as "Veranillo de San
Juan." If it occurs in July or the beginning of August, sometimes with
alternating dry and rainy days, people refer to it as the canicula.
Rain is Life
The annual differences in rainfall from one part of the
country to another, together with the change in average temperature
from warm to cool as one moves from sea level up into the mountains,
are the basis for the variety of life zones (tropical dry forest,
tropical wet forest, premontane rain forest, etc.) that exist in Costa
Rica, and also are intimately linked with such biological events as
flowering and fruiting of plants and breeding and migration of animals.
|
