in this research, their effects on the flight of airplanes were investigated. The study area is the country of Iran, and the flight routes of Kermanshah, Ahvaz and BandarAbbas to Tehran. The research data includes maps of the Vertical Transect (profile) of the jet stream, the daily average of the Zonal wind (U-Wind) and meridional wind (V-Wind) components for the winter period of 2018 through NOAA/NCEP environmental databases. Also, flight route information was received from FlightRadar24 and Flightaware systems. First, by using Vertical Transect maps, the days containing strong U-Wind were extracted, and the average position of the core of the jet streams in the Zonal and meridional wind components, the Tropospheric level of 200 HP was detected. The list of flights was prepared, and the Zonal Wind maps were produced. Finally, the height of the flights was compared with the level of the currents of the jet streams, and the influence or lack of influence of the jet streams on the flights was studied. According to the results of the research, all the jet streams caused turbulence for all flights, and they caused a decrease in the speed of flights between Ahvaz and BandarAbbas to Tehran and an increase in the speed of flights between Kermanshah and Tehran according to the direction and type of jet streams. It was also found that all the jet streams had a speed of more than 90 knots, so the capacity to create tension and turbulence such as CAT was seen in them

In this study, the effect of jet width on baroclinic instability is discussed, while a baroclinic instability problem is solved using a quasi-geostrophic (QG) model on a β-plane. To solve the QG equations on the β-plane, the finite difference method is applied in the vertical and meridional directions. Boundary conditions in this problem are considered for both vertical and meridional directions. Indeed, two hard boundaries at the surface of the Earth and tropopause are chosen for the vertical, with non-flux conditions at the upper and lower boundaries along the meridian. After discretization along both meridian and vertical directions, the equation takes the form of Sturm–Liouville, particularly the eigenvalue of the resulting Sturm – Liouville equation is the imaginary part of the phase velocity. Using the Matlab software, the eigenvalue instability equation can be solved. In this study, the effect of jet stream width on baroclinic instability is investigated. In addition, jet streams with different widths are defined and the growth rate of atmospheric waves is calculated. The jet stream equation has a sinusoidal shape in the meridional direction, but an exponential form in the vertical, in which the jet width is adjusted using the sine-wave parameter. Once built according to the desired width, the problem is solved and the rate of the growth of atmospheric waves is obtained. The jet has a limited effect on the growth of atmospheric waves. The effect of the jet on the baroclinic instability is such that a disturbance with meridional wavenumber is imposed on the problem. The meridional wavenumber causes a decrease of the growth rate at the desired zonal wavenumber. For this reason, we conclude that the jet has a limited effect on the growth rate of baroclinic instability. The effect of the width on baroclinic instability is identified in a two-dimensional model, in which the vertical extent is an independent variable in the problem, such that the solution is very similar to the combination of Eady (1949) and Charney (1947) models. Using a quasi-terrestrial linear model, they concluded that jet streams width, increases the growth rate of waves. Their results are inconsistent with ours due to application of one-dimensional model in their study. They noted that jet stream introduces increasing or decreasing wind shear, and with increasing wind shear, an increasing growth rate of baroclinic instability is observed. However, this result cannot be generalized for a two-dimensional problem, in which for a range of latitudes, which is called a channel, the jet velocity at the bottom of the channel starts from a minimum, but increases to the maximum value in the middle of the channel and again decreases to the same value at the top of the channel. However, in a one-dimensional problem, only the jet stream core is considered, such that baroclinic instability is solved only on the vertical direction in the jet core. Thus, the effect of jet stream on baroclinic instability in a two-dimensional framework is conducted here. The instability problem is solved using the jet stream shown in Figure 1. According to Lindzen (1993), in the presence of a jet stream, the meridional wavenumber is equivalent to the inverse of the width of the jet, which increases as the jet width decreases, such that an increase in the meridional wavenumber is associated with a slowdown of the jet stream, following Eady (1949). Initially, by reducing the jet width to 2400 kilometers, the growth rate also decreases. However, reduction of the jet width to a certain extent (i. e., 3240 km) results in a decrease of the growth rate, while further decrease of the jet width is associated with an increase of the growth rate (e. g., for jet stream with widths of 2400 and 1710 km). Thus, the widest jet stream is associated with the maximum growth rate for wavenumbers between 6 and 13, while the narrowest jet stream is associated with the maximum growth rate for wavenumbers between 13 and 20. The relationship between the jet bandwidth and velocity of the jet center based on observational data over the Pacific is discussed below. A linear relationship (34) is obtained between velocity of the jet core and the observed jet width. Velocity of the jet core increases with the decline of the jet width (Table 4). Width and velocity of the jet in Table 4 are plotted in the numerical scheme, in which real and imaginary parts of the phase velocity are calculated when the jet core velocity is increased following a decrease of the jet width, which results in an enhancing of the growth of atmospheric waves. Therefore, under real conditions, in which width and velocity of the jet core are represented in Table 3, a meridional constraint can no longer be introduced.

In this study, the frequency and location of jet streams associated with heavy rainfalls have been analyzed using environmental to circulation approach. Based on the threshold of the upper 99 percent, 125 days of the super and overall heavy rainfall was selected from the IRIMO data base (including 1437 synoptic, climatic, and rain gage stations). jet stream frequencies and their locations have been detected from 0o to 120o E and 0o to 80o N in five levels (250, 300, 400, 500 and 600 hPa level) at 00:00, 06:00 and 12:00 UTC. The results of this study have shown that jet streams at 00:00 have a remarkable frequency at all levels with the exception of the 250 hPa level. Generally, jet streams are mostly extended from 250 to 600 hPa levels that have provided baroclinic conditions for Iran’s super heavy rainfalls. In this study, the northern half of Saudi Arabia was a major location where jet streams occur or are visible.

Introduction: The El Nino and La Nina each favor a different location for the dips and bulges of the polar jet stream. They also affect the strength of the subtropical jet stream. In this way, they influence the weather in middle latitudes. The influence is greatest in the winter months when the coupling of the tropical and mid-latitude patterns is the best. In most El Nino winters, the warming of the air due to strong convection over warm water over the eastern and central Tropical Pacific helps energies the polar and subtropical jet streams to the north. A strong low pressure develops over the Aleutians. The polar jet stream curves to the north into northwestern North America, while the subtropical jet stream ripples across northern Mexico or the southern United States. During La Nina winters, on the other hand, the polar jet stream is strong and the subtropical jet stream weaker in the vicinity of North America (D’Aleo & Grube, 2002).The effect of ENSO on precipitation and temperature has been studied in detail by a number of Iranian researchers (Khosh Akhlagh, 1998; Azizi, 2000; Ghayor and Asakereh, 2001; Nazem al-Sadat and Ghassemi, 2003; Masoudian 2005, Khorshid Doost and Ghavidel Rahimi, 2006; Yar Ahmadi and Azizi 2007; Hagh Negahdar et al.; 2007). Most of these researches have attributed the increase and decrease of autumn rainfall to El Nino and La Nina respectively. Although it seems that seasonal distribution of rainfall during different ENSO phases does not follow any particular pattern, different patterns can be seen in each of the two compared phases. Givi et al (2009) indicated the positive and negative anomalies of precipitation in each El Nino and La Nina year. Not enough studies have been done on different phases of ENSO that affect the climate of Iran. This study aims to provide a more comprehensive analysis of changes in the 200Hpa jet stream in relation to various ENSO phases (for September, October, November and December).

Introduction: According to the definition of World Meteorology Organization (WMO), as the speed of the air mass is more than 30 meters per second, the jetstream will arise. The core of the jetstream is with baroclinic atmosphere due to the large difference in temperature and wind speed. There are two west jetstreams in the northern hemisphere. The northern jet stream is called polar front jetstream and the southern is called subtropical jetstream. Polar Front jet stream produce intense temperature gradient by polar air mass and tropical Polar Front jet stream is produced by strong temperature gradient of polar and subtropical air. The subtropical jetstream is produced by temperature gradient in tropopause as limited to the upper troposphere.

In this research in order to identify the most effective jet stream pattern, creating pervasive rain falls in Iran during the period 1971 to 2008, from turning approach to the environmental approach was used. For this purpose, first of all, an elemental analysis with component based approach on wind speed data with the balance of 300 HP for 12 of Zolo was done by demystified data of United States of America Atmospheric Prediction Center. The analysis showed that 8 main components are able to explain 85% of the diffraction of data. Then, by applying a hierarchical cluster analysis with Ward's method on the scores 8, mentioned component during the 3098 days under study, eight prevailing jet stream was detected on Iran. Then for every pattern, using the interclass correlation, one day with the most correlation was chosen as the day of an agent of that pattern. The next step is to determine the most effective model jet stream leading to rainfall, the amount of rainfall of 32 synoptic stations in the center of provinces, along with maps in heights, Omega, 1000, and 500 hp and map the convergence of moisture flux for levels of 700 and 850 hp for each of the days of the agent was investigated. The results showed that the pitch of strong jet stream in fourth pattern with a speed of 65 meters per second at the level of 300 hPa in southern of Iran along with formation of through cold Chali on the Caspian Sea, simplify the conditions for the convergence of the lower levels of Iran atmosphere, and influx of moisture from the Mediterranean Sea along with along with unstable conditions of high atmosphere, causing pervasive rain in Iran

Introduction: Zayanderood basin is one of the major internal river basins in the central Iran, where Zayanderood River is the only permanent river. Fluctuations in rainfall in recent years have affected different areas of Iran. Because of the dependence of the provinces of Isfahan, Yazd, and Kerman on water resources of this basin, changes and fluctuations in precipitation within this watershed have had many social and economic consequences with bad outcomes in regional, national and international dimensions. Therefore, knowledge of mechanisms governing the procurement and availability of water resources in the basin can be helpful to develop strategies to deal with social and economic stresses. This can happen with more confidence, planning and proper management of water resources in the basin.

This study was on dust in Kermanshah synoptic station in March 27, 2003. Mean daily 500hpa geopotential height, mean sea level and 250hpa wind field maps analysis showed a middle atmospheric trough over Black Sea and the north of the Mediterranean Sea which is consistent with a middle atmospheric low pressure over Iraq, east of Turkey and north of Saudi Arabia. In addition, the divergence of subtropical jet stream in 200hpa level and polar front jet stream in 250hpa level is the most important reason for convergence and induced upward motions over deserts in Iraq, Syria and Jordan, between 35-50 ° longitudes and 30-35 o latitudes. The intensity of dust was related to the vertical angle between the center of the surface low pressure and 500hpa level low geopotential height.