scholarly journals Climatic analysis of effective jet streams frequency on extreme precipitations in west of Iran

2020 ◽  
Author(s):  
Shahab Shaffie ◽  
GholamAli Mozaffari ◽  
Younes Khosravi
Keyword(s):  
Geographical Location ◽  
Jet Stream ◽  
The West ◽  
Jet Streams ◽  
Positive Vorticity ◽  
Subtropical Jet Stream ◽  
Unstable Layer ◽  
Four Levels ◽  
Upper Level ◽  
Generalized Distribution

Abstract In this study, the frequency of effective jet streams was analyzed in extreme and widespread precipitations in the west of Iran. For this purpose, the daily precipitation of 69 synoptic and climatic stations over 18,624 days (1961–2010) were selected. Then, 119 days of extreme and widespread precipitation in the study area were chosen based on generalized distribution for conducting related reviews and analyses. The frequency of jet streams in the geographical location from 0° to 120°E and −10° to 80°N were reviewed at four levels (250, 300, 400 and 500 hPa). Due to the large volume of information, only the highest and lowest levels (250 and 500 hPa) in relation to the surface were considered. According to the results, the highest frequency of jet stream was observed at 250 hPa. The second quarter of the jet stream core lay over the west of Iran (which is associated with increasing positive vorticity as well as upper-level divergence and lower-level convergence of the atmosphere). In general, the extension of jet stream up to 500 hPa indicated an unstable layer thickness, which can cause extreme and widespread precipitation in the west of Iran. The results of selected days based on cluster analysis and Lund correlation revealed that in rainy days, the wind speed was more than 50 m/s and the subtropical jet stream speed was over 40 m/s, leading to extreme precipitation in the west of Iran.

scholarly journals Characteristics of Explosive Cyclones over the Northern Pacific

2017 ◽  
Vol 56 (12) ◽  
pp. 3187-3210 ◽  
Author(s):  
Shuqin Zhang ◽  
Gang Fu ◽  
Chungu Lu ◽  
Jingwu Liu
Keyword(s):  
Cold Season ◽  
Early Spring ◽  
Occurrence Frequency ◽  
Northwestern Pacific ◽  
Jet Stream ◽  
Central Pacific ◽  
Positive Vorticity ◽  
Northern Pacific ◽  
Upper Level ◽  
Upper Level Jet

AbstractExplosive cyclones (ECs) over the northern Pacific Ocean during the cold season (October–April) over a 15-yr (2000–15) period are analyzed by using the Final (FNL) Analysis data provided by the National Centers for Environmental Prediction. These ECs are stratified into four categories according to their intensity: weak, moderate, strong, and super ECs. In addition, according to the spatial distribution of their maximum-deepening-rate positions, ECs are further classified into five regions: the Japan–Okhotsk Sea (JOS), the northwestern Pacific (NWP), the west-central Pacific (WCP), the east-central Pacific (ECP), and the northeastern Pacific (NEP). The occurrence frequency of ECs shows evident seasonal variations for the various regions over the northern Pacific. NWP ECs frequently occur in winter and early spring, WCP and ECP ECs frequently occur in winter, and JOS and NEP ECs mainly occur in autumn and early spring. The occurrence frequency, averaged maximum deepening rate, and developing and explosive-developing lifetimes of ECs decrease eastward over the northern Pacific, excluding JOS ECs, consistent with the climatological intensity distributions of the upper-level jet stream, midlevel positive vorticity, and low-level baroclinicity. On the seasonal scale, the occurrence frequency and spatial distribution of ECs are highly correlated with the intensity and position of the upper-level jet stream, respectively, and also with those of midlevel positive vorticity and low-level baroclinicity. Over the northwestern Pacific, the warm ocean surface also contributes to the rapid development of ECs. The composite analysis indicates that the large-scale atmospheric environment for NWP and NEP ECs shows significant differences from that for the 15-yr cold-season average. The southwesterly anomalies of the upper-level jet stream and positive anomalies of midlevel vorticity favor the prevalence of NWP and NEP ECs.

scholarly journals Modified Three-Dimensional Jet Indices and Their Application to East Asia

Atmosphere ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 776 ◽  
Author(s):  
Haishan Li ◽  
Ke Fan ◽  
Zhiqing Xu ◽  
Hua Li
Keyword(s):  
East Asia ◽  
East Asian ◽  
Three Dimensional ◽  
Vertical Direction ◽  
Jet Stream ◽  
Jet Streams ◽  
Zonal Winds ◽  
Subtropical Jet Stream ◽  
Subtropical Jet ◽  
The Relationship

A set of three-dimensional jet indices (jet speed index, jet pressure index, jet latitude index) has been proposed in previous literature to describe the variation of jet streams in both the horizontal and vertical direction. We refer to these indices at the ‘AC’ indices, after the names of the researchers involved. However, the physical meaning of the AC indices and the relationship between AC indices and climate systems are not fully understood. Further study is still needed for applying the indices in East Asia (70°–140° E). In this study, based on the understanding of the physical meaning of the AC indices, latitudinal ranges of East Asian jet streams are determined, and a set of modified AC indices is proposed. Based on the modified AC indices, the linear trends in East Asian jet streams are studied, and the relationship between East Asian jet streams and the climate is researched. The results show that the jet speed index corresponds to the meridional temperature gradient (MTG) of the middle to upper troposphere (500–200 hPa); the jet pressure index corresponds to the pressure level at which the MTG equals zero; and the jet latitude reflects the meridional MTG distribution. The latitudinal ranges of jet streams are determined based on the meridional profiles of climatological zonal-mean zonal winds. Within such a latitudinal range, the climatological zonal-mean zonal winds between 400 and 100 hPa are only westerly, and the maximum wind speed in the vertical direction at every latitude appears between 400 and 100 hPa. The jet streams can be further classified according to the features of the profiles. For East Asia (70°–140° E), jet streams can be classified into winter subtropical jet streams (15°–47.5° N), summer subtropical jet streams (27.5°–60° N), and summer polar front jet streams (60°–87.5° N). The classification of jet streams can be supported by their correspondence to the distribution of tropospheric baroclinicity. A set of modified AC indices can be acquired by using the new ranges of East Asian jet streams in the definition of the original AC indices. Descriptions of jet streams using the modified AC indices are more in accordance with the distributional features of the climatological zonal winds over East Asia, and the physical meanings of the modified AC indices are more definite than the original indices. Using the modified AC indices, we find a significant weakening trend in the strength of the summer subtropical jet stream (−0.13 m/s/10 yr) and a significant northward shift of the winter subtropical jet stream (0.22°/10 yr), and the possible reasons for these trends are studied. Finally, the relationships of East Asian jet streams in winter and summer with atmospheric circulation, temperature, and precipitation are also investigated in this study.

scholarly journals A network-based detection scheme of the jet stream core

2016 ◽  
Author(s):  
Sonja Molnos ◽  
Tarek Mamdouh ◽  
Stefan Petri ◽  
Thomas Nocke ◽  
Tino Weinkauf ◽  
...  
Keyword(s):  
Western Hemisphere ◽  
Jet Stream ◽  
Data Sets ◽  
Jet Streams ◽  
Detection Scheme ◽  
The North ◽  
Eastern Hemisphere ◽  
Subtropical Jet ◽  
Latitudinal Position ◽  
Upper Level

Abstract. The polar and subtropical jet streams are strong upper-level winds with a crucial influence on weather throughout the Northern Hemisphere mid-latitudes. In particular, the polar jet is located between cold Arctic air to the North and warmer sub-tropical air to the South. Strongly meandering states therefore often lead to extreme surface weather. So far algorithms to detect jets' core around the hemisphere, including strong North-South undulations, are lacking. We develop a network-based scheme using Dijkstra's shortest path algorithm to detect the polar and subtropical jet stream core. This algorithm considers not only the commonly used wind strength for core detection but also takes wind direction and climatological latitudinal position into account. Furthermore, it distinguishes between polar and subtropical jet, and between separate and merged jet states. The detection scheme is optimized using simulated annealing and compared against an algorithm developed by Rikus (2015). After the successful optimization process we apply our scheme to climatology data and analyse seasonal data sets. We present probabilistic, regionally distinct positions for both jets for all seasons. This shows that winter is characterized by two well separated jets at mean longitudes of 20° S and 140° N. In contrast, summer normally has a single merged jet over the western Hemisphere and both merged and separated jet states possible in the eastern Hemisphere. With this algorithm it is possible to investigate the position of the jets' cores around the hemisphere and is therefore well suitable for analyses of jet stream patterns in observations or models.

Using reflection seismic method to estimate the fluid dynamics parameters related to wakes

2021 ◽  
Author(s):  
Wenhao Fan ◽  
Haibin Song ◽  
Kun Zhang ◽  
Yi Gong ◽  
Shun Yang ◽  
...  
Keyword(s):  
Potential Vorticity ◽  
Negative Potential ◽  
Distribution Area ◽  
The West ◽  
West Side ◽  
Reflection Seismic ◽  
Vorticity Distribution ◽  
Positive Vorticity ◽  
Coherent Vortices ◽  
Survey Line

<p>In this study, when using reflection seismic data to study the wakes of the Batan Islands, a method for estimating the fluid dynamics parameters such as the relative vorticity (relative Rossby number) and the relative potential vorticity is proposed. Although the relative Rossby number estimation method proposed in this study cannot guarantee absolute accuracy in the calculation value, this method is more accurate in describing the positive and negative vorticity distribution for the wakes, and the resolution of the positive and negative vorticity distribution described by this method is higher than the result of the reanalysis data. For the wakes developed in the Batan Islands, the reflection events in the wake development area have the larger inclination than the reflection events in the western Pacific water distribution area. It is also found that the negative vorticity wakes are mainly distributed on the west side of the island/ridge, and the positive vorticity wakes are mainly distributed on the east side of the island/ridge. This is consistent with the understanding of previous wakes simulations. The strong vorticity values in the study area are mainly distributed at depths above 300m, and the maximum impact depth of wakes can reach 600m. At the downstream position of the wake on the survey line 7, it can be seen that the bottom boundary layer has separated, and there is the negative vorticity wakes on the west side intruding into the positive vorticity wakes on the east side , which is presumed to be caused by the disturbance of the small anticyclone existing near the Batan Islands. For the survey line 7, the negative potential vorticity is mainly distributed on the west side of the island/ridge, and the influence range can reach the sea depth of 600m. In the negative potential vorticity region, there is strong energy dissipation and vertical shear. In this study, we don’t find the existence of submesoscale coherent vortices on the survey line 7, but find the reflection structure similar to filaments on the seismic section. Combined with the analysis of the balanced Richardson number angle of survey line 7, we speculate that the wake in the negative potential vorticity distribution area has the characteristics of symmetrical instability, and the symmetrical instability may destroy the process of filaments forming submesoscale coherent vortices.</p>

scholarly journals Characteristics of mid-latitude planetary waves in the lower atmosphere derived from radiosonde data

2012 ◽  
Vol 30 (10) ◽  
pp. 1463-1477 ◽  
Author(s):  
R. Wang ◽  
S. D. Zhang ◽  
H. G. Yang ◽  
K. M. Huang
Keyword(s):  
Standing Wave ◽  
Zonal Wind ◽  
Lower Stratosphere ◽  
Radiosonde Data ◽  
Wind Component ◽  
Jet Stream ◽  
Fort Worth ◽  
Vertical Wavelength ◽  
Subtropical Jet Stream ◽  
Subtropical Jet

Abstract. The activities of mid-latitude planetary waves (PWs) in the troposphere and lower stratosphere (TLS) are presented by using the radiosonde data from 2000 to 2004 over four American stations (Miramar Nas, 32.9° N, 117.2° W; Santa Teresa, 31.9° N, 106.7° W; Fort Worth, 32.8° N, 97.3° W; and Birmingham, 33.1° N, 86.7° W) and one Chinese station (Wuhan, 30.5° N, 114.4° E). Statistically, strong PWs mainly appear around subtropical jet stream in the troposphere and lower stratosphere. In the troposphere, the activities of the mid-latitude PWs are strong around the centre of the subtropical jet stream in winter and become small near the tropopause, which indicates that the subtropical jet stream may strengthen the propagation of PWs or even be one of the PW excitation sources. Among the three disturbance components of temperature, zonal and meridional winds, PWs at Wuhan are stronger in the temperature component, but weaker in the zonal wind component than at the other four American stations. While in the meridional wind component, the strengths of PW spectral amplitudes at the four American stations decrease from west to east, and their amplitudes are all larger than that of Wuhan. However, the PWs are much weaker in the stratosphere and only the lower frequency parts remain. The amplitudes of the PWs in the stratosphere increase with height and are strong in winter with the zonal wind component being the strongest. Using the refractive index, we found that whether the PWs could propagate upward to the stratosphere depends on the thickness of the tropopause reflection layer. In the case study of the 2000/2001 winter, it is observed that the quasi 16-day wave in the troposphere is a quasi standing wave in the vertical direction and propagates upward slowly with vertical wavelength greater than 24 km in the meridional component. It propagates eastward with the zonal numbers between 5 and 8, and the quasi 16-day wave at Wuhan is probably the same quasi 16-day wave at the three American stations (Miramar Nas, Santa Teresa and Fort Worth), which propagates steadily along the latitude. The quasi 16-day wave in the stratosphere is also a standing wave with vertical wavelength larger than 10 km in the zonal wind component, and it is westward with the zonal number 1–2. However, the quasi 16-day wave in the stratosphere may not come from the troposphere because of the different concurrent times, propagation directions and velocities. By using the global dataset of NCEP/NCAR reanalysis data, the zonal propagation parameters of 16-day waves in the troposphere and stratosphere are calculated. It is found that the tropospheric 16-day wave propagates eastward with the zonal number 6, while the stratospheric 16-day wave propagates westward with the zonal number 2, which matches well with the results of radiosonde data.

A Role for Barotropic Eddy–Mean Flow Feedbacks in the Zonal Wind Response to Sea Ice Loss and Arctic Amplification

2019 ◽  
Vol 32 (21) ◽  
pp. 7469-7481 ◽  
Author(s):  
Bryn Ronalds ◽  
Elizabeth A. Barnes
Keyword(s):  
Sea Ice ◽  
North Atlantic ◽  
Zonal Wind ◽  
Jet Stream ◽  
Arctic Amplification ◽  
Mean Flow ◽  
Jet Streams ◽  
The North ◽  
Wind Response ◽  
The North Pacific

Abstract Previous studies have suggested that, in the zonal mean, the climatological Northern Hemisphere wintertime eddy-driven jet streams will weaken and shift equatorward in response to Arctic amplification and sea ice loss. However, multiple studies have also pointed out that this response has strong regional differences across the two ocean basins, with the North Atlantic jet stream generally weakening across models and the North Pacific jet stream showing signs of strengthening. Based on the zonal wind response with a fully coupled model, this work sets up two case studies using a barotropic model to test a dynamical mechanism that can explain the differences in zonal wind response in the North Pacific versus the North Atlantic. Results indicate that the differences between the two basins are due, at least in part, to differences in the proximity of the jet streams to the sea ice loss, and that in both cases the eddies act to increase the jet speed via changes in wave breaking location and frequency. Thus, while baroclinic arguments may account for an initial reduction in the midlatitude winds through thermal wind balance, eddy–mean flow feedbacks are likely instrumental in determining the final total response and actually act to strengthen the eddy-driven jet stream.

Orientalist Approaches in Advertising

2021 ◽  
pp. 974-990
Author(s):  
Simge Kırteke
Keyword(s):  
Geographical Location ◽  
Geographic Location ◽  
Semiotic Analysis ◽  
Demographic Structure ◽  
The West ◽  
Advertising Campaign

Brands offer indicators to audiences through advertisements in many topics such as political, ideological, economic, and cultural. In particular, while creating their advertisements, international brands make use of the indicators that assume the cultural and demographic structure of the geographic location they are published in and carry out advertising campaigns under the influence of Orientalism. With these advertisements, it is presented how the West shows the East with an Orientalist perspective to the audiences that the advertisement reaches both in the geographical location where it is published and in the international geography. Within the scope of this study, the Nike brand, which emerged in Western societies and became a big name in the international arena, the advertising campaign with the slogan “What will they say about you?” and the SHE (Saudi Heroines Empowering a Nation) advertisement were examined and compared with the method of semiotic analysis, and their relationships with Orientalism were explained.

scholarly journals Characterization of silage production and the use by dairy farmers in the West of Santa Catarina state

2018 ◽  
Vol 39 (4) ◽  
pp. 1639 ◽  
Author(s):  
Adenor Vicente Wendling ◽  
Luiz Carlos Pinheiro Machado Filho
Keyword(s):  
Production Systems ◽  
Soil Analysis ◽  
Geographical Location ◽  
Dairy Farming ◽  
Production Volume ◽  
Structured Interviews ◽  
The West ◽  
Santa Catarina ◽  
Silage Production ◽  
Santa Catarina State

Silage has been widely used in dairy production. However, little is known about its use at production level. The goal of this study was to characterize production and usage of silage for the dairy farming in Western Santa Catarina state. Thirty farms were selected randomly by their geographical location, in 11 municipalities of the West of Santa Catarina state, and they were invited to participate in the research. Out of these 30 farms, 6 did not have any dairy activity, and 2 preferred not to participate in the research, thus were not included. Semi-structured interviews and on-site visits were then performed. All data were analyzed with the software R version 3.2.2. 95% of the farmers produced and fed silage to animals. Out of the 22 farmers participating in the study, 82% provided silage for dairy cows during the whole year; in 86% of these farms, the silage was fed right after milking, in an average amount of 6.06 ± 0.63 kg DM (dry matter) AU-1 (animal unit, 500 kg) day-1. The average area used for maize production was 8.46 ha, representing 59% of the area destined to dairy farming. The average silage production was 8.8 and 7.6 t ha-1 year-1 in the season and off-season crop respectively, without significant differences. In most silage production areas, the no-tillage system is adopted, with the use of pesticides, chemical fertilization and transgenic seeds, without soil covering or crop rotation. Farms that fertilized maize based on soil analysis had the greatest silage yield, compared to the ones that fertilized without relying on soil analysis. The use of different types of pesticides and fertilizer quantities was not correlated to the silage production volume. Overall the production systems and the quantity of silage produced and fed to the cows do not follow technical criteria; thus silage yield and use could be improved if following strategies to better allocate crop inputs.

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