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 Earthís, 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 planetís surface.  The axis of Arida is tilted at 5 degrees to the planetís 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 Ė ranging from 100 degrees at the equator to 35 degrees at the north and south poles Ė 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 Devilís Ear Range; it is called the Devilís 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 planetís 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 Aridaís 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.

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