عنوان مقاله [English]
The Gap winds are low-level winds associated with geomorphological features such as mountain passes, canyon valleys, and gaps Gap winds are usually significant when there is a considerable pressure gradient on two side of the gap. The Gap winds, in addition to intrinsic values for study, also have practical aspects, including in the field of wind energy use, architecture and development plans and plans, maritime transport (if they are located in the vicinity of water areas), air transport, operations Military. In the present study, for the first time in Iran, the mechanism of formation of Gap Lut wind in the form of climate has been studied and the characteristics of this wind have been introduced including hourly, daily, monthly and seasonal behavior. Due to the wind in the eastern part of the desert plain, Lut desert and Jazmourian plain, the name of this wind, which is known as mountain wind in Shahdad region, was named Koloja wind. Ko, from the beginning of Kavir letter, Lu, from Lut and Ja, from Jazmourian.
The data studied in this study include three main categories, which are:
First, for the initial identification of the characteristics of meteorological quantities and their statistical analysis, the data of 75 meteorological stations have been used in the country at intervals of 3 hours and in the period from the beginning of establishment until 2018.
reanalysis data (Era-Interim) of European Center for Medium-Scale Atmospheric (ECMWF) were used to study, the meteorological parameters and structure of patterns like sea level pressure, geopotential height and temperature for standard pressure levels, relative and Specific humidity in low-troposphere, wind field, relative vorticity, wind, vertical velocity, convergence and cross section of the relevant quantities were studied by temporal and spatial intervals 3-hour and 0.125 degree resolution (in terms of latitude and longitude during the period of 1987-2019
The study of 10 m surface wind pattern with a scale of 10 km in the eastern regions of Iran shows a northerly wind with a sharp and specific pattern in these areas. This north wind is divided into two branches, western and eastern, on the north of Khorasan. This wind on the eastern borders of Iran on the Sistan plain is known as the 120-day wind. The western branch of this wind, which blows on areas east of the desert plain, Lut desert, Jazmourian, is less known in Iranian sources. The monthly pattern of both branches of this north wind is relatively the same and their peak activity is in August. The strengthening of surface heating conditions, both in the field of sea and land, has caused a spatial expansion in August; Increase the altitude and relative integrity of these two winds. This wind also has a specific daily pattern. The peak of north wind strengthening in both branches is 12 and 18 UTC. The presence of a high-pressure belt is in the areas between 50 and 70 degrees north with a European high-pressure core in the north of the Caspian Sea and west of the Urals. This high-pressure belt, in contrast to the low-pressure belt prevailing in the subtropical region over the Middle East, causes wind conditions to blow from the north to the eastern regions of Iran. Existence of high Pamir-Hindu Kush-Himalayan mountain system in the east of the region, especially its western massif, Pamir on the one hand, and the existence of lower and of course important mountain systems such as North Khorasan, South Khorasan as a secondary induction plays an important role in channeling the north wind. And have a bias towards the northeastern regions of Iran. In the southern part of low-pressure belt, the presence of low desert zones as well as the warm water zone of the Oman-Persian Gulf has provided the conditions for the formation of a large low-pressure center on this water zone. In addition, on the flat and desert areas of the region, the increase in solar radiation (snsible heat flux) caused by short-wave solar radiation, which is accompanied by a deep high-altitude system in the middle and upper troposphere, leads to the formation of local independent low-pressure cells such as Gang, Rigistan. , Baluchistan, Sistan, Lut, Jazmourian.
The mountainous region not only lead to the formation of high pressures affecting the wind and strengthen its intensity, but also the topographic arrangement of the eastern region of Iran in the form of parallel meridian mountain ranges on both sides of Lut plain, is the main cause of strong winds in Koloja. The combination of regional and local synoptic conditions along with the mountain walls on both sides of the flat desert area of Lut has provided the conditions for the Bernoulli effect and the creation of a wind chat during the day in this area.
The direction of the wind is slightly variable, depending on the surface topography and the rough arrangement of the stations. Shahdad station can be considered the best place to study the wind conditions. Warm season rosewind show a stronger role of this wind in the hot season than the cold season at all stations. This issue has the role and effect of different spatial radiation pattern conditions as well as the uneven role in pressure distribution compared to cold season synoptic patterns. The windrose show the 24-hour variations of wind behavior of Koloja. The behavior of this wind shows that this wind is highly dependent on daily radiation and heating conditions. At night, especially at 3 UTC, in all control stations, especially the southern stations located in the desert and lowlands, the prevailing wind is the wind that blows from the surrounding highlands and does not indicate the direction corresponding to the Koloja wind. The core of the speed of this wind is at an altitude of 1500 meters above sea level. Depending on the height of the study area, this accelerating current is formed at an altitude of 1000 meters above the surface (low level jet stream).