Annual Fluctuations and Displacements of Inter Tropical Convergence Zone (ITCZ) within the Range of Atlantic Ocean-India

Abstract

Inter Tropical Convergence Zone (ITCZ) is one of the major systems in making the general circulation of atmosphere. Many climatologists believe that the starting point of the general circulation of atmosphere is from this system. It seems that the annual displacement of this system is coordinated with the sun. In this study we have tried to investigate the annual and seasonal displacement of this system within the range of Middle East, especially within the range of longitude of Iran in a long period of time (statistical period of 66 years). This is the first study in the field of ITCZ monthly and annual longterm changes in Iran. In this study, not only his exact position on Africa and South West Asia ITCZ is determined, it also shows the change in the period of 66 years. These results can also be used on regional climate changes. For this purpose topographic and surface level pressure maps are 1000 and 850 hpa and they were approximately extracted monthly for 12 months of the year from 1948 to 2013 and also they were extracted from the National Oceanic and Atmospheric Administration Site in America within the range of 30˚ west to 110˚ east, and they were extracted by using the flow map of location (ITCZ). Due to the sudden displacement in the ITCZ bar path in the two seasons of summer and winter, on the Middle East region, the direct impact of this displacement on sudden changes of seasons, the start and end of untimely rains, its impacts on agricultural products and water recourses of the country so all these reasons are essential that this phenomenon should be studied carefully. Studies have shown that ITCZ is not a coordinated solar system and its displacement is not coordinate with the apparent annual displacement of the sun. October is the only month of ITCZ that within the range of 10 northern degrees in all the ranges of longitude 20˚ west to 110˚ east has an approximate orbital shape. In 6 months of the year (from November to April) (ITCZ) within the range of 30˚ east or 110˚ east, it is entirely located in the Southern Hemisphere and on the contrary in 5 months from May to September (ITCZ) within the range of 30˚ 13east to 110˚ east, it is entirely located in the Northern Hemisphere. And in this period, ITCZ has its highest Northern movement on the Earth. So that at the foot of the Himalayas it moves to 30˚ north. Within the range of Africa, ITCZ never enters the Southern Hemisphere at any time of the year. And the interesting phenomenon of severe refraction in the way of ITCZ, during the cold period, is within the range of Ethiopia and ITCZ has approximately redirected for Meridian and enters the Southern Hemisphere.

Hydro-climatic variability in the southwestern Indian Ocean between 6000 and 3000 years ago

“…1b). This observation is further supported by analyses of the low-level wind trajectory cluster composites of February in those years when the southern boundary of the ITCZ was anomalously north or south (Lashkari et al, 2017;Freitas et al, 2017) of its long-term mean February position ( Fig. S1a, b in the Supplement).…”

Spatiotemporal Trends and Variations of the Rainfall Amount, Intensity, and Frequency in TRMM Multi-satellite Precipitation Analysis (TMPA) Data

“…The corresponding statistical and significance test results are generated in Table 1. A hemispheric asymmetry can be observed through the results: the means of all the parameters are higher in the NH than SH for ocean (3.58 mm/day, 13.45%, 23.87 mm/day in the NH vs. 2.50 mm/day, 11.17%, 19.18 mm/day in the SH for MR, RF and CR, respectively) due to the NH-deflection of ITCZ [38]; and inverse phenomena can be observed for land (2.10 mm/day, 5.61%, 34.24 mm/day in the NH vs. 3.29 mm/day, 8.31%, 37.11 mm/day in the SH for MR, RF and CR, respectively) because the maritime continent and Amazon rainforest are mainly distributed in the SH [39,40]. The mean values of MR calculated in this study are comparable to those of GPCP V2.3 (2.95 mm/day for tropical, 3.0 mm/day for ocean, and 2.81 mm/day for land) [37].…”

Investigation of Vorticity during Prevalent Winter Precipitation in Iran

“…However, the divergence of air ow in the low-pressure west of the Persian Gulf caused decreased air ow on the surface and vorticity advection of −2.5 × 10 −5 S −1 (m/s) on Iran's southern half. However, Lashkari showed that in a lowpressure ow, depending on the density of air and the input ow of air to its east, convergence occurs, and in its western part, divergence occurs due to the high speed of air ow [42][43][44][45]. Such a situation is clearly shown in Figure 3(a).…”