Precipitations above normal level in first month of autumn

October 28, 2018 - 21:8

TEHRAN — Most of provinces in the country have met above-normal-average rainfall and normal temperatures during the first month of the new crop year (September 23-October 22), head of the national center for drought and crisis management, affiliated to Iran Meteorological Organization (IMO), has said.

During the Iranian calendar month of Mehr (September 23-October 22), the country received 10.4 millimeters of rainfall, which, compared to its 6.8 millimeter long-term average level in the aforesaid period, has seen a 6 millimeter increase, ISNA quoted Sadeq Ziaeian as saying on Sunday.

Ziaeian went on to say that the country has experienced an increase in precipitation by 3.1 millimeters compared to the 7.3 millimeter reported last year over the first month of the crop year. 

Mazandaran province got some 127 mm of rain, while its long-term average rainfall rate is reported to be 74 mm, so the province with 53 mm increase in rainfall hit the record high for the highest precipitation rate nationwide, over the same period, he noted.

Moreover, the provinces of Ardebil, East Azarbaijan, West Azarbaijan, and Zanjan have faced rainfall shortages by 13.6, 8, 5.5, and 5.6 mm, respectively, he added.
The capital also experienced 12 mm increase in rainfall in comparison to the same period last year and this amount reaches to 13 percent when comparing to its long-term mean, he highlighted.

Iran met normal average temperature last month

Elsewhere in his remarks, Ziaeian said that the temperature condition throughout the country, except for a limited number of provinces has reported normal during the first month of autumn.

Khuzestan and Ilam provinces with 1.5°C and 1.6°C temperature rise, saw the biggest variations in mean temperatures, he lamented.

Compared to the long-term mean, Khorasan Razavi and South Khorasan had 1.5°C and 1.4°C decrease in temperature over the aforementioned period, he added.

The capital also has faced a temperature drop by 0.5°C last month, compared to its long-term average, he concluded.

Recent increased rainfall unrelated to cloud seeding 

A weatherman with the IMO, Ahad Vazifeh, rejected all the claims saying cloud seeding is the major reason behind the recent floods hitting over 9 provinces in the country, YJC reported.

“By entering the second half of the year, rainfall is expected to increase particularly, so that flooding has occurred in some provinces,” he noted.

According to the reports published by the IMO, the precipitation rate is anticipated to face a significant increase, and flood prone areas already has been warned, he added.
He went on to say that currently, cloud seeding is nearly impossible in the country since it needs the necessary infrastructure.

He further warned that by improper employing of cloud seeding techniques quite the reverse outcomes can lead to less precipitation or extreme precipitation and floods.

Using cloud seeding technique to increase precipitation amounts is extremely costly, so in order to avoid the problem of precipitation shortages, we need to properly apply water consumption policies, Vazifeh concluded.

Cloud seeding, a form of weather modification, is a method to change the amount or even type of precipitation. Rainfall occurs when super cooled droplets of water – those that are still liquid but are at a temperature below the usual freezing point of zero centigrade – form ice crystals. Now too heavy to remain suspend in the air, these then fall, often melting on their way down to form rain.

Even in dry areas the air usually contains some water. This can be made to come together and form ice crystals by seeding the atmosphere with chemicals such as silver iodide or dry ice. They work to promote rainfall by inducing nucleation – what little water is in the air condenses around the newly introduced particles and crystallizes to form ice. The ‘seeds’ can be delivered by plane or simply by spraying from the ground.


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