Lomas

Lomas (Spanish for "hills"), also called fog oases and mist oases, are areas of fog-watered vegetation in the coastal desert of Peru and northern Chile. About 100 lomas near the Pacific Ocean are identified between 5°S and 30°S latitude, a north-south distance of about 2,800 kilometres (1,700 mi). Lomas range in size from a small vegetated area to more than 40,000 hectares (99,000 acres) and their flora includes many endemic species. Apart from river valleys and the lomas the coastal desert is almost without vegetation. Scholars have described individual lomas as "an island of vegetation in a virtual ocean of desert."

According to the Köppen Climate Classification system, the coastal desert of Peru and the Atacama desert of Chile feature the rare mild desert climate, abbreviated "Bwn" on climate maps. Temperatures are mild year round and precipitation is nearly non-existent, averaging 3 millimetres (0.12 in) to 13 millimetres (0.51 in) per year in most locations. Many years have no precipitation at all. The Atacama Desert of Chile is commonly known as the driest non-polar place in the world.Arica, Chile, in the middle portion of the coastal desert, went a record 173 months without measurable precipitation in the early 20th century.

Occasional rainfall is caused by El Niño. For example, in March 2015, the desert in Chile received about 25 millimetres (0.98 in) in one day which caused flooding. After the rare rains the desert briefly blooms with flowers. With the sparse precipitation, the coastal desert is almost devoid of vegetation except in lomas and along rivers which originate in the Andes and cross the desert to the Pacific.

The moisture for the vegetation in the lomas comes from fog which rolls in from the nearby Pacific Ocean and embraces mountains which come down near the sea. The cold waters of the Humboldt Current run offshore. During the austral winter thick stratus clouds creep inland to an altitude of 1,000 metres (3,300 ft) most days from May until November. The coastal fog and mist is called garua in Peru and camanchaca in Chile. During this season the vegetation in the lomas is lush and green and many species of flowers bloom. In the austral summer from December to April, the weather is mostly sunny and the lomas become dryer. The moisturizing impact of the fog is increased by the mild temperatures throughout the year and high average humidity of the coastal deserts. For example, Lima, Peru, located at 12°S latitude has average monthly temperatures ranging from 17 °C (63 °F) to 23 °C (73 °F), very cool for locations in the tropics. Lima's average humidity is 84 percent, more than double the average humidity in most deserts.

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Wikipedia