Arida's Climate
| Arida is somewhat warmer than Earth but like Earth there are wide variations
in temperature caused by geologic and historic factors. Because of its
gravity being 1.22 that of Earth’s, the atmosphere on Arida has a pressure
of 15 pounds per square inch at sea level, about 1.2 times that of earth.
Arida is considerably drier than Earth, with the area to the east of Unola
Ocean but west of the Chieftain Mountains being the one relatively moist
area on the planet. The Unola Ocean covers about 40 percent of the surface,
but the Upper and Lower Mammoth Lakes add another 10 percent for an overall
total of 50 percent of the planet’s surface. |
The axis of Arida is tilted at 5 degrees to the planet’s orbit, causing
a distinct summer and winter season, but the mean differences in temperature
and precipitation are not as great as those on Earth.
Because of the relatively high surface temperature of much of the planet
– ranging from 100 degrees at the equator to 35 degrees at the north and
south poles – there has been and continues to be some loss of atmosphere
to space, but as the planet cools this loss has tended to decrease with
time. |
Air and water currents
| There are three main currents in the Unola Ocean, but the two on the
east side exert the major influence on planetary climate. The south flowing
Angelica Current originates in the relative cooler waters of the north
Unola Ocean but warms up as the water flows towards the equator. The north
flowing Red Devil Current originates off The Eyes islands in an active
volcanic region so it is considerably warmer than the Angelica with an
average temperature of about 74 degrees. The two currents meet off the
eastern coast of Frog Island, creating the Frog Eddy, a large body of warm
water rotating in a clockwise direction. |
| Beyond the temperate zones, near the polar regions known as the Northern
and Southern Badlands, we find the Badlies, dry but cold air masses circulating
east-to-west. To the west of Unola Ocean, a dry warm wind blows off the
Devil’s Ear Range; it is called the Devil’s Blowout. The Beta Current is
a cold water current flowing from south to north along the western side
of the Unola Ocean. |
|
The warm, roiling waters of the Frog Eddy provide a major part of the
atmopsheric moisture for Arida. The evaporation gives rise to the Southeast
Chieftain winds which blow steadily off the Unola Ocean towards the Chieftain
Mountains. As they come up against the mountains, which rise to 11,000
meters, much of their moisture is dropped on the Verdant Plain which lies
between the Unola Ocean and the Chieftain Mountains. This is the one area
of Arida where there is a tropical rainforest, but just a relatively short
way to the east Mount Dagger rises to 11,500 meters and is capped with
snow all year round.
To the east of the mountains is a rain shadow area, where the now-dry
winds blow from west to east, towards the Omega Desert. These are the Omega
Trade winds, and they set the pattern for the west-to-east circulation
of the planetary weather systems. |
Rainfall
| The vast majority of the surface of Arida gets less than five inches
of rain per year. The main exception is found in the Verdant Plain on the
eastern shore of Unola Ocean, where the Southeast Chieftain winds drop
as much as 40 inches of rain in some parts, allowing for the formation
of tropical rainforests on the western side of the Chieftain Mountains.
This is the only part of Arida where the rainfall generally exceeds 20
inches a year. |
|
On the further reaches of the eastern shore the rainfall decreases
to between 5 and 10 inches per year for a distance of several hundred miles
from the ocean. However, as the Omega Trades get further from the ocean,
they lose most of their moisture leaving the interior dry and desert-like.
On the northeastern shore, the rainfall is between 10 and 20 inches per
year tapering off in the north.
Of note are the lake effect areas on the eastern edges of the Upper
and Lower Mammoth lakes. Due to evaporation from these large bodies of
water and the west-to-east flowing of planetary winds, there is a temperate
zone on the eastern edges of each set of lakes, where the rainfall averages
5 to 10 inches a year. |
|
Temperature
|
Most of the planet Arida has a mean average annual temperature of between
60 and 70 degrees, considerably higher than that of Earth. This is because
of the greater density of the atmosphere, which traps considerably more
of the solar energy than that of Earth, but its also because of the
planet's average Albedo of 0.2, meaning that 80 percent of the radiation
from Venda is absorbed. While the Albedo varies from 0.05 in the Verdant
Zone west of the Chieftain Mountains to 0.4 in the Omega Desert, the planet’s
mean is quite low, which means that most of the radiation from the star
Venda is absorbed.
The average annual temperature varies only slightly between summer and
winter because of the slight (5 percent) tilt of Arida’s axis. Because
the temperature variation is within 10 degrees in summer and winter, the
mean average annual temperature is a sufficient guide to the climatic conditions. |
|