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Time to Update World’s Driest and Wettest Locations?

By: Christopher C. Burt, 9:26 PM GMT on March 06, 2013

Time to Update World’s Driest and Wettest Locations?

For several decades now the officially recognized wettest and driest locations in the world (for which at least 30 years of records are available) have been Mawsynram, India with an annual average precipitation of 11872 mm (467.4”) and Arica, Chile with .76mm (.03”) according the to the World Meteorological Organization’s World Weather/Climate Extremes Archive. It seems that perhaps these figures need to be updated in order to reflect more recent data. This blog will look at what might be the ‘newest’ driest location on earth.

Arica: Driest place in the world?

There is no question that locations in the Atacama Desert region of northern Chile are the driest on the planet. Even the driest locations in the Sahara Desert and Antarctica normally receive some measureable precipitation a few times each year or at least every few years. This is not the case in the Atacama where many years often go by without any measureable precipitation whatsoever.



The Atacama Desert of northern Chile is without question the driest region on earth. Photo by Ed Darack.

Arica is a fairly large city (population about 175,000) on the coast of northern Chile near the Peruvian border. Weather records have been maintained here since the late 19th century although I am not sure of the exact year they were established.



The city of Arica has been an important port since the 16th century when the Spaniards used it to ship gold and silver to Europe. It is now a thriving manufacturing center as well. Photo from Wiki commons.

The .76mm (.03”) annual average precipitation that is commonly cited is based on one 59-year period of record that is not specified but mostly likely for a time prior to 1968 when the figure was mentioned in the monograph ‘Weather And Climate Extremes’ and credited to the U.S. Environmental Science Services Administration, 1968. This same publication also credited Arica as having the world’s longest dry period on record when no measureable precipitation was reported for a consecutive 14-year period between October 1903 and January 1918. In spite of its dryness, Arica enjoys an equable climate with little in the way of temperature extremes and frequent fog and cloud cover due to the cold ocean temperature.


A climate table for Arica. Note that the precipitation column is left blank. The city’s extreme range of temperature (33°C/91.4°F to 5.0°C/41.0°F) is similar to what one might find in some California coastal locations.

However, looking at the 30-year POR 1971-2000 (the most recent POR I can find for Arica) the average annual rainfall was 1.46mm (.06”), or double what the published figure has been. There were a couple of intense El Nino episodes during this time that most likely contributed to the wetter-than-normal amounts.



Total monthly precipitation at Arica for the 1971-2000 POR. The greatest calendar day rainfall occurred on January 2, 1997 when 4.2mm (.17”) fell (a further 0.4 mm fell that month as well bringing the monthly total to 4.6 mm). The greatest 24-hour rainfall in Arica's entire POR was 10.0 mm (.39") set in a January year unknown. Chile's greatest 24-hour precipitation record was 290.3 mm (11.43" set at Juan Fernandez (date unknown). 1997-1998 saw the development of one of the strongest El Nino’s on record. Table from Direccion Meteorologica de Chile (Chilean Meteorology Directorate).

The reason this part of Chile is so dry is because of the cool Peruvian Current that sweeps northward along Chile’s coast lowering ocean temperatures and blocking any warm and moist air from the tropical Pacific Ocean. Furthermore, Arica is too far north (18° latitude) to be affected by the winter extra-tropical storms that provide precipitation to the coastal regions of central and southern Chile.



The cool Peruvian Current blocks moist air from the Pacific from reaching the northern Chilean Coast. Map from Wiki commons.

Quillaga: Driest Place on Earth?



A map of Chile illustrating the location of Quillaga in relation to Arica and Maria Elena. From Wiki commons.

Over the past 50 years the Chilean meteorological authorities have expanded their network of weather stations and so we now have 30-year POR precipitation records for other locations in the Atacama Desert region. Some of these appear to be considerably drier than Arica, hard to believe as that might be! There are two sites that are especially noteworthy: Quillaga and Maria Elena that rest about 320 kl (200 miles) south of Arica and 70 kl (45 miles) inland from the Pacific Ocean. A pluviometer was established at Quillaga in 1964. Since 1970 the following comprise the only ‘precipitation’ events measured at the site:

0.4 mm (.02”) June 1984

0.2 mm (.01”) October 1984

1.0 mm (.04”) May 1992

There has been no measurable precipitation since May 1992 (as of the end of 2012), a 20-year dry period, and thus a world record for such. This also means that the average annual precipitation for the 30-year POR of 1971-2000 was a meager 0.05 mm (not 0.5 mm which has been published in some articles). According to climatologist Maximiliano Herrera the official average for the site is 0.2 mm/.008” (compared to 0.76 mm in Arica), the higher figure ostensibly a result of a rainfall sometime during the 1964-1970 period. Maria Elena, which is about 50 miles south of Quillaga, is almost just as dry. However, a rainfall of 0.9mm (.04”) in 2000 has caused its average annual precipitation record to bump slightly higher than Quillaga’s. There has been no measureable precipitation in Maria Elena since the 2000 event. Quillaga has a sad history. It’s agricultural water source, the Loa River, was polluted in 1998. Max relates:

During the El Nino of 1998, rain fell at higher elevations causing poisonous and radioactive traces from copper mines to overflow into the river. This resulted in the death of all sheep, swine, and bees in Quillaga and the destruction of the alfalfa grass. 90% of the inhabitants had to emigrate. Now only 120 people are left. They get some water from Maria Elena by truck twice a week. Before the tragedy of 1998 the village was producing the highest quantity of honey-per-bee in the world, thanks to a technique imported by a Canadian who helped develop the local apiary business.

The New York Times published a story about Quillaga’s plight in March 2009.



The near-ghost town of Quillaga was, for the most part, abandoned after 1998 when toxins from Andean copper mines polluted the Loa River, its only agricultural water source. Photo by Azul Ambientalistas.

Perhaps Quillaga can rebuild itself as a weather tourist destination with the legitimate claim of being the driest inhabited place on earth. I will blog on what might be the wettest place on earth in the weeks to come.

KUDOS: Maximiliano Herrera for much of the information about Quillaga and Maria Elena.

Christopher C. Burt
Weather Historian

Extreme Weather Precipitation Records

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

Christopher,

Thanks for the Pacific Ocean sketch.

I'm assuming the currents noted are ocean currents, not air currents, since your article does not elaborate or clarify.

If so, please explain, " ... the cool Peruvian Current that sweeps northward along Chile’s coast lowering ocean temperatures and blocking any warm and moist air from the tropical Pacific Ocean. "

How can water currents and counter-currents block airflow ?

I'm sure my high-IQ Korean high school girls are bound to ask me this, since I'd like to use your article for an English Geography lesson/discussion for my Senior classes.

Thanks !

Steve
@1 For what it is worth, the Wikipedia article on the Atacama Desert has this to say.

"Geographically, the aridity can be explained by the following reasons:

"The desert is located on the leeward side of the Chilean Coast Range, so little moisture from the Pacific Ocean can reach the desert.
"The Andes are so high that they block convective clouds, which might bring precipitation, formed above the Amazon Basin from entering the desert from the east.
"An inversion layer is created by the cold Humboldt current and the South Pacific High.
"The rain that would change the climate of the land mostly falls at sea instead. Largely this is caused by the cold waters of the Humboldt current just off shore. The temperature change causes most of the clouds and the rain to occur over the ocean instead of over the land. [13] The Humboldt Current transports cold water from Antarctica towards the north the length of the Chilean and Peruvian coasts; this water that makes the western sea breezes cold, reducing evaporation and creating a thermic inversion %u2013cold air immobilized under a cover of tepid air--, preventing the formation of large clouds which produce rain."

edit: added quotes to make it clearer that I'm quoting wikipedia.
Quoting Steve8rox:
Christopher,

Thanks for the Pacific Ocean sketch.

I'm assuming the currents noted are ocean currents, not air currents, since your article does not elaborate or clarify.

If so, please explain, " ... the cool Peruvian Current that sweeps northward along Chile’s coast lowering ocean temperatures and blocking any warm and moist air from the tropical Pacific Ocean. "

How can water currents and counter-currents block airflow ?

I'm sure my high-IQ Korean high school girls are bound to ask me this, since I'd like to use your article for an English Geography lesson/discussion for my Senior classes.

Thanks !

Steve


See Babbit comment. These are ocean currents not atmospheric currents. Ocean currents have far greater effect on atmospheric currents then visa-versa. I'm afraid you will, as a teacher, have to understand this dynamic on your own (I would have to write 1000 words otherwise, so do your research).

Babbit explains just why cold water inhibits moisture from forming. I live in the San Francisco Bay Area where the same influence takes place. Look at the map; the 'California' current lowers sea surface temperatures and hence California is, for the most part, a very dry place. If California had a reverse of this current (moving south to north like the Gulf Stream on the east coast of the U.S.) then we would see year around precipitation and San Francisco would be a very wet place. Likewise in Chile if the ocean current was running north to south then northern Chile would have lots of precipitation.
Thanks for the very informative and thought-provoking post. Based on everything you've written, I'd say you've made a very strong case for moving Quillaga ahead of Arica on the WMO's "Driest places on Earth" list. In fact, in light of the recent data, it seems like a bit of a stretch for Arica to hold on to the title. It'd be very interesting to hear someone defend Arica in this discussion, because, frankly, it doesn't appear they'd have much on which to stand.

(Too, you certainly seem to have an impressive track record, having instigated the overturning of Libya's 90-year-old global land temperature record, and that certainly lends great credibility to your research.)

On a side note, the pollution problems that left Quillaga a virtual ghost town is very sad and tragic, but one we've heard far too many times before.
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