Precipitation increases by 44% within a month

January 21, 2020 - 19:23

TEHRAN – The latest statistics released by the Ministry of Energy shows that the country received 77.6 billion cubic meters in precipitations over the Iranian calendar month of Azar (November 22-December 21, 2019), which is 44 percent more than a month before.

Since the beginning of the current water year (September 23, 2019) till the end of Azar, the country’s rainfall reached up to 144.4 billion cubic meters.

However, the total rainfall was reported to be 87.6 millimeters during autumn, while it was recorded at 92.1 mm in the same period last year. 

Moreover, the long term average rainfall was estimated at 62.3 mm.

Following above-normal precipitations in the country speculations have gone rife linking increased precipitations of the current year with the start of a 30-year or even a century-long wet spell. However, the claims have been scientifically rejected by meteorologists and climatologists.

Eminent meteorology professor Hossein Ardakani said in May 2019 that a wet spell is defined as a period of consecutive rainy years and that experiencing one year of above-normal precipitations followed by years of lower-than-normal precipitations does not mean a wet spell.

Receiving higher precipitations in the country depends on various factors such as teleconnection patterns, he added.

According to the U.S. Climate Prediction Centre the term "teleconnection pattern" refers to a recurring and persistent, large-scale pattern of pressure and circulation anomalies that spans vast geographical areas.

Teleconnection patterns are also referred to as preferred modes of low-frequency (or long time scale) variability.

Although these patterns typically last for several weeks to several months, they can sometimes be prominent for several consecutive years, thus reflecting an important part of both the interannual and interdecadal variability of the atmospheric circulation. 

Many of the teleconnection patterns are also planetary-scale in nature and span entire ocean basins and continents. For example, some patterns span the entire North Pacific basin, while others extend from eastern North America to central Europe. Still, others cover nearly all of Eurasia.

Teleconnection patterns reflect large-scale changes in the atmospheric wave and jet stream patterns, and influence temperature, rainfall, storm tracks, and jet stream location/ intensity over vast areas. Thus, they are often the culprit responsible for abnormal weather patterns occurring simultaneously over seemingly vast distances.

Ardakani said that over the past two decades the number of years with lower-than-normal precipitations were high and now it appears that teleconnection patterns can positively affect the number of years with increased precipitations in the next 10 to 20 years in Iran.


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