The Effects of North Atlantic Oscillation on the atmospheric middle level Anomaly and precipitation of Iran.Case study: west of Iran.

Nejad, Meysam Toulabi; Hejazizadeh, Zahra; Bosak, A.; bazmi, nasrin

doi:10.29252/jgs.18.49.19

Cited by 3 publications

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“…Dry periods are usually accompanied by westward displacement of a subtropical high, while wet periods are associated with eastward displacement of the high-pressure system toward the Arabian Sea. The Southern Oscillation Index (SOI) in its positive phase can decrease precipitation in the northwest of Iran [11]. Research has also confirmed that the late withdrawal of the Indian monsoon is associated with a delay in the onset of fall precipitation over Iran.…”

Section: Introductionmentioning

confidence: 99%

Changing Causes of Drought in the Urmia Lake Basin—Increasing Influence of Evaporation and Disappearing Snow Cover

Habibi

Babaeian

Schöner

2021

Water

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The water level of the Urmia Lake Basin (ULB), located in the northwest of Iran, started to decline dramatically about two decades ago. As a result, the area has become the focus of increasing scientific research. In order to improve understanding of the connections between declining lake level and changing local drought conditions, three common drought indices are employed to analyze the period 1981–2018: The Standard Precipitation Index (SPI), the Standard Precipitation-Evaporation Index (SPEI), and the Standardized Snow Melt and Rain Index (SMRI). Although rainfall is a significant indicator of water availability, temperature is also a key factor since it determines rates of evapotranspiration and snowmelt. These different processes are captured by the three drought indices mentioned above to describe drought in the catchment. Therefore, the main objective of this paper is to provide a comparative analysis of drought over the ULB by incorporating different drought indices. Since there is not enough long-term observational data of sufficiently high density for the ULB region, ECMWF Reanalysis data version 5(ERA5) has been used to estimate SPI, SPEI, and SMRI drought indicators. These are shown to work well, with AUC-ROC > 0.9, in capturing different classes of basin drought characteristics. The results show a downward trend for SPEI and SMRI (but not for SPI), suggesting that both evaporation and lack of snowmelt exacerbate droughts. Owing to the increasing temperatures in the basin and the decrease in snowfall, drought events have become particularly pronounced in the SPEI and SMRI time series since 1995. No significant SMRI drought was detected prior to 1995, thus indicating that sufficient snowfall was available at the beginning of the study period. The study results also reveal that the decrease in lake water level from 2010 to 2018 was not only caused by changes in the water balance components, but also by unsustainable water management.

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Section: Introductionmentioning

confidence: 99%

Changing Causes of Drought in the Urmia Lake Basin—Increasing Influence of Evaporation and Disappearing Snow Cover

Habibi

Babaeian

Schöner

2021

Water

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“…However, SLP over the past few decades reduces from 2 to 8 mbar in the sixth decade (Figure 4(f)). In January, the decrease in SLP is most likely due to a reduction in the intensity and extent of the Azore sub-tropical high pressure and its retreat on Iran (Alipour & Zalnezhad 2018;Toulabi Nejad et al 2018). The SLP reduction and Azore high-pressure retreat on the south and southwest regions of Iran lead to an increase in the Sudan low power, the intensification of instability, ascendant mechanism, and the creation of suitable conditions for precipitation.…”

Section: Analysis Of Sudan Low Slp Changesmentioning

confidence: 99%

Sudan low changes affecting rainy days in southwestern Iran over six decades (1957–2019)

Mohammadi

Hombari

Pazhoh

2021

Journal of Water and Climate Change

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The present study evaluated the dynamic changes in Sudan low systems during six decades (1957–2019), which were classified based on solar cycles. Rainfall days were extracted in January using data from 42 synoptic stations in the south and southwest regions of Iran. Then, the rainy days due to the Sudan low system were separated from the precipitation of the other atmospheric systems using the visual analysis of the maps. The synoptic analysis indicated that the sea level pressure has been decreasing at all sampling stations from the first to the sixth decade. Furthermore, decreasing elevation to −80 m (negative anomaly) in the 500 hPa level atmosphere from the first decade to the sixth decade, indicated further atmospheric instability and more strengthening of the Sudan low compared to previous decades. The contribution of advection moisture to the area increased within the region at 700 hPa. This implies that the role of the transferred moisture from the intertropical convergence zone is increasing in the systems transferred from Sudan and in the study area. In general, the share of Sudan low precipitation is increasing in the south and southwest regions of Iran. This result is a positive effect of the climate change on the study area.

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Persistence and spatial–temporal variability of drought severity in Iran

Noorisameleh

Gough

Mirza

2021

Environ Sci Pollut Res

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The Effects of North Atlantic Oscillation on the atmospheric middle level Anomaly and precipitation of Iran.Case study: west of Iran.

Cited by 3 publications

References 0 publications

Changing Causes of Drought in the Urmia Lake Basin—Increasing Influence of Evaporation and Disappearing Snow Cover

Changing Causes of Drought in the Urmia Lake Basin—Increasing Influence of Evaporation and Disappearing Snow Cover

Sudan low changes affecting rainy days in southwestern Iran over six decades (1957–2019)

Persistence and spatial–temporal variability of drought severity in Iran

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