Desert Climate Dry Tropical Climate (BW)

The dry desert is in Köppen's BWh climate category. It is a Low Latitude climate. The Bstands for Dry Desert climates. All months have average temperatures over 64° F (18° C). The Wstands for desert climate. Finally, the hstands for dry and hot, with average annual temperatures over 64° F (18° C). I guess they're trying to tell us its hot, hot out there.

The description of this awesome biome climate is quite odd, but also as it is odd, it is also very interesting.

Dry Desert climates are formed by high-pressure zones in which cold air descends. Then the descending air becomes warm but, instead of releasing rain, the heat from the ground evaporates the water before it can come down as rain. The ground is super hot because the sun's rays beat down on it directly overhead. Not a lot of atmosphere to protect it from radiant energy.

By the way, approximately 1 in. (2.5 cm) of rain falls in dry deserts per year. The average annual temperature of these miles of hot sand is 64° F (18° C).

The latitude range is 15-28° north and south of the equator. Their global range covers about 1/5 of the earth, including the world's great deserts: Sahara, Sonora, Thar, Kalahari and the Great Australian.

Plants of the Dry Desert have adapted to the lack of water by using dew for moisture and taking in water through their leaves and stems.

Justin S. 2000


Lambert, Wayne. "Desert Land and Climate", World Book Encyclopedia, 1995.

Adams, R. "Desert Life" Academic American Encyclopedia, 1995

Mojave Desert Climate Dry Tropical Climate (BW)

The Mojave Desert is found at elevations of 2,000 to 5,000 feet, and is considered a "high desert". It is a transition desert between the hot Sonoran Desert to the south, and the cold Great Basin Desert to the north. The climate of the Mojave Desert has extreme fluctuations of daily temperatures, strong seasonal winds, and clear skies.

Temperatures have been as low as 8°F in January and as high as 119°F in August. In May the temperature will begin to climb in excess of 100°F and continue into October. The night temperatures in July and August can at times be in the low to mid 90s.

In late winter and early spring the wind is a prominent feature, with dry winds blowing in the afternoon and evening. Winds in excess of 25 mph, with gusts of 75 mph or more are not uncommon. Although it is windy during all months, November, December and January are the calmest.

The humidity is below 40% most of the year. During most winter nights, and during and after summer rains the humidity can get above 50%.

The Mojave Desert lies in the rainshadow of the Coast Ranges and receives an average annual precipitation of 5 inches. Most of the rain falls between November and April. There is, however, a summer thunderstorm season from July to September with violent and heavy rainstorms possible. In 1986 only 1.5 inches of rain fell on the Eastern Mojave Desert, while in 1983 6.5 inches came down. May and June are usually the driest months.

During cycles of El Niño, as we have experienced in recent years, more rain falls on the Mojave Desert than usual. The runoff has resulted in shallow ponds in the normally dry washes and playas. For the last few years there has been more rain overall than the climate of 20 years ago.

The Mojave Desert experienced very heavy rains in the 1950s, when surface runoff resulted in severe erosion of gullies and washes and heavy silt deposits. A long dry period followed, ending with the present wet period.

According to the U.S. Geological Survey, vegetation has grown denser since the early 1970s, most likely due to the increased precipitation. They conclude that the climate of the Mojave Desert hasn't been static, and has experienced many changes this century. Their ongoing research suggests that the recent climate variation has influenced both the landscape and the plants and animals of the desert ecosystem.



A.R. Royo, "The Mojave Desert - Desert USA",

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Sonoran Desert Climate Dry Tropical Climate (BW)

The sunlight of the Sonoran desert changes during the day and it gets hotter. Seasonal temperatures range from an average of 52º F in the winter, to 86º F in the summer. In some seasons the temperatures can reach 32º F at night. In some portions of the desert, near the tip of Mexico, the temperature can reach a high of 134º F in the shade.

The Sonoran desert is one of the wettest deserts in North America and averages from 3 to 16 inches of rain a year. It has two rainy seasons, one in the summer and another in the winter. The summer rains are short and heavy and are often followed by a rainbow. The winter rains are longer and lighter and are more widespread.

There are a lot of sand dunes and grasses in the desert. There are also a lot of cacti, herbs, thorny and thornless shrubs. The creosote bush is the most common plant, and the saguaro cactus is the largest and the most conspicuous plant in the desert.

Many desert animals, such as bighorn sheep, pocket mouse, and pronghorn antelope (an endangered species) use cacti and other vegetation as a shelter from harsh weather and as a source of water. The bighorn sheep has adapted to the desert, because it has big feet, good for the rough terrain, and only needs to drink every few days. The pocket mouse has adapted to the desert, because it is very small, is sand colored, and can run fast from predators. It also doesn't need to drink because it gets all the water it needs from the food it eats and retains its urine.

The latitude of the Sonoran Desert ranges from 25º to 33º North, and the longitude ranges from 105º to 110º West.

The Köppen classification of this climate is BWh, where B stands for a dry climate, BW stands for an arid climate with annual precipitation usually less than 15 inches (40 cm.), and h stands for a dry and hot climate with a average annual temperature over 65° F.

Even though the Sonoran desert is one of the hottest North American deserts, it has lots of diverse vegetation and wildlife due to its two rainy seasons.

by Daniel F. 2003


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Sonoran Desert Climate Dry Tropical Climate (BW)

The Sonoran Desert has many different climates and plants. This desert gets 120 to 300 mm of precipitation each year, mostly as rain. Daytime temperatures can reach or go over 40° C during the summer months of May through September. The rain falls during two wet seasons. One rainy season occurs from December through March and the other from July through September.

Winter rainfall is higher in the western part of the desert, and lowest in the southeast. The Upland Sonoran Desert has regular amounts of winter and summer rainfall. Although winter frosts are common there, they are not extreme. Where the Sonoran desert merges with the Mojave desert in the northwest, summer rainfall is usually scarce. The Arizona Upland has five seasons. There is the summer monsoon from early July to mid-September. Autumn exists from October to November with warm temperatures and low humidity. Winter is from December to February and has mostly sunny, mild days, with some storms with wind, rain and cool temperatures. Spring is from late February to late April. The temperatures are mild with little rain. The fore-summer drought occurs in May and June. The temperature is high and the humidity low. There is no rain in most years.

The Lower Colorado Valley region of the Sonoran desert is the hottest and driest. Annual rainfall is 50 mm or less. Summer temperatures are usually around 50° C. Sand dunes and drought tolerant shrubs with some succulents are found in this region. One of the driest areas in North America lies in the western Sonoran near the Desierto de Altar. The region gets less than 9 cm of rain per year and droughts can last for more than 2 years.

In Sonora, Mexico the desert has a wetter summer rainy season with a drier winter. Drought deciduous plants are common in this area.

The Sonoran desert on Baja has cool moist weather in the winter. Summer isn't quite as hot as most of the Sonoran desert because of the cooling effect of the Pacific Ocean. Moisture from fog and dew allow epiphytes to grow on the desert plants. Many different types of agaves and yuccas grow in this region.

The Köppen classification for the Sonoran Desert is BWh. The B stands for a dry climate where rain evaporates before it falls on the desert floor. There is no water surplus in this type of desert, therefore no permanent streams originate from this zone. W stands for an arid climate. BW, therefore, is an arid climate with an annual precipitation usually less than 40 cm (15 in.). The h designates that the average annual temperature is over 18° C (64.4° F)



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