scholarly journals Investigation of the North Atlantic Oscillation and Indian Ocean Dipole Influence on Precipitation in Turkey with Cross-Spectral Analysis

Atmosphere ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 99
Author(s):  
Umut Sakine Demir ◽  
Abdullah Cem Koc
Keyword(s):  
Spectral Analysis ◽  
Phase Shift ◽  
Indian Ocean ◽  
North Atlantic ◽  
Indian Ocean Dipole ◽  
Maximum Phase ◽  
The North ◽  
The Indian Ocean ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

Predicting the future behavior of precipitation is of the utmost importance for planning agriculture or water resource management and in designing water structures. Determining the relationships between precipitation and the oceans may enable more accurate predictions. Therefore, oceanic and other persistent indices called teleconnection patterns can be used, namely the North Atlantic oscillation (NAO) and the Indian Ocean dipole (IOD). The NAO affects the precipitation patterns in the Atlantic Ocean and Mediterranean countries, such as in Turkey. The IOD is related to temperature and precipitation in the Indian Ocean coastal countries and in some areas far from the Indian Ocean. In this study, the effects of the NAO and IOD indices on precipitation in Turkey were investigated by means of cross-spectral analysis between the monthly total precipitation (mm) and monthly NAO and IOD index values. Phase shift values were also calculated for the selected periods and their accuracy was evaluated statistically, using the determination coefficient (R2) and Akaike information criterion (AIC) as performance criteria for the linear model. The results indicated strong correlations for the 13-, 14-, 16-, and 22–23-month periods between the NAO index and precipitation values; and for the 13-, 14-, 16–17-, and 20–21-month periods between the IOD index and precipitation values. After cross-spectral analysis between the NAO and IOD indices and precipitation values, the maximum phase shift values increased as the periods increased, while the maximum phase shift value for each period was almost half of the period value. Moreover, the maximum cross-power spectral density (CPSD) values increased as the periods increased. High CPSD values were observed in the west of Turkey for the NAO and in the east of Turkey for the IOD.

scholarly journals The Linear Sensitivity of the North Atlantic Oscillation and Eddy-Driven Jet to SSTs

2019 ◽  
Vol 32 (19) ◽  
pp. 6491-6511 ◽  
Author(s):  
Hugh S. Baker ◽  
Tim Woollings ◽  
Chris E. Forest ◽  
Myles R. Allen
Keyword(s):  
Indian Ocean ◽  
North Atlantic Oscillation ◽  
North Atlantic ◽  
High Sensitivity ◽  
Internal Variability ◽  
The North ◽  
The Indian Ocean ◽  
The North Atlantic ◽  
The North Atlantic Oscillation ◽  
The Impact

Abstract The North Atlantic Oscillation (NAO) and eddy-driven jet contain a forced component arising from sea surface temperature (SST) variations. Due to large amounts of internal variability, it is not trivial to determine where and to what extent SSTs force the NAO and jet. A linear statistical–dynamic method is employed with a large climate ensemble to compute the sensitivities of the winter and summer NAO and jet speed and latitude to the SSTs. Key regions of sensitivity are identified in the Indian and Pacific basins, and the North Atlantic tripole. Using the sensitivity maps and a long observational SST dataset, skillful reconstructions of the NAO and jet time series are made. The ability to skillfully forecast both the winter and summer NAO using only SST anomalies is also demonstrated. The linear approach used here allows precise attribution of model forecast signals to SSTs in particular regions. Skill comes from the Atlantic and Pacific basins on short lead times, while the Indian Ocean SSTs may contribute to the longer-term NAO trend. However, despite the region of high sensitivity in the Indian Ocean, SSTs here do not provide significant skill on interannual time scales, which highlights the limitations of the imposed SST approach. Given the impact of the NAO and jet on Northern Hemisphere weather and climate, these results provide useful information that could be used for improved attribution and forecasting.

scholarly journals Origin of Indian Ocean multidecadal climate variability: role of the North Atlantic Oscillation

2021 ◽  
Author(s):  
Tiejun Xie ◽  
Jianping Li ◽  
Kaiqi Chen ◽  
Yazhou Zhang ◽  
Cheng Sun
Keyword(s):  
Indian Ocean ◽  
North Atlantic ◽  
Climate Model ◽  
Indian Ocean Region ◽  
Multidecadal Variability ◽  
The North ◽  
Ocean Region ◽  
The Indian Ocean ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

AbstractThe multidecadal variability of Indian Ocean sea surface temperature (IOSST) has an important impact on both the regional Indian Ocean climate and the global climate. Here, we explore multidecadal variability in the annual IOSST. Observational analysis shows that the annual IOSST multidecadal variability is not only related to the Pacific Decadal Oscillation (PDO), but also to the North Atlantic Oscillation (NAO). The NAO leads by 15–20 years the detrended annual IOSST in which the PDO signal of the same period has been removed. Further analysis reveals that the NAO leads the annual IOSST multidecadal variability through its leading effect on the Atlantic Multidecadal Oscillation (AMO). The AMO affects the vertical wind anomaly in the Indian Ocean region through the Atlantic–Indian Ocean multidecadal teleconnection (AIMT), which in turn affects the net longwave radiation in the Indian Ocean region, thus driving the annual IOSST multidecadal variability. A Hasselmann model based on NAO and PDO further verify the joint influence of the NAO and PDO on the multidecadal variability of the IOSST. A PDO-based linear model and a climate model that incorporates the NAO signal are also constructed for the annual IOSST. Results show that the climate model with the NAO signal can better simulate the annual IOSST. This again verifies that the NAO is part of the annual IOSST multidecadal variability source, indicating that the annual IOSST variability may be due to the combined influences of the NAO and PDO.

scholarly journals The Meridional Shift of the Midlatitude Westerlies over Arid Central Asia during the Past 21 000 Years Based on the TraCE-21ka Simulations

2020 ◽  
Vol 33 (17) ◽  
pp. 7455-7478
Author(s):  
Nanxuan Jiang ◽  
Qing Yan ◽  
Zhiqing Xu ◽  
Jian Shi ◽  
Ran Zhang
Keyword(s):  
Indian Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Last Deglaciation ◽  
The Past ◽  
The North ◽  
External Forcings ◽  
The Indian Ocean ◽  
The Last Deglaciation ◽  
The North Atlantic

AbstractTo advance our knowledge of the response of midlatitude westerlies to various external forcings, we investigate the meridional shift of midlatitude westerlies over arid central Asia (ACA) during the past 21 000 years, which experienced more varied forcings than the present day based on a set of transient simulations. Our results suggest that the evolution of midlatitude westerlies over ACA and driving factors vary with time and across seasons. In spring, the location of midlatitude westerlies over ACA oscillates largely during the last deglaciation, driven by meltwater fluxes and continental ice sheets, and then shows a long-term equatorward shift during the Holocene controlled by orbital insolation. In summer, orbital insolation dominates the meridional shift of midlatitude westerlies, with poleward and equatorward migration during the last deglaciation and the Holocene, respectively. From a thermodynamic perspective, variations in zonal winds are linked with the meridional temperature gradient based on the thermal wind relationship. From a dynamic perspective, variations in midlatitude westerlies are mainly induced by anomalous sea surface temperatures over the Indian Ocean through the Matsuno–Gill response and over the North Atlantic Ocean by the propagation of Rossby waves, or both, but their relative importance varies across forcings. Additionally, the modeled meridional shift of midlatitude westerlies is broadly consistent with geological evidence, although model–data discrepancies still exist. Overall, our study provides a possible scenario for a meridional shift of midlatitude westerlies over ACA in response to various external forcings during the past 21 000 years and highlights important roles of both the Indian Ocean and the North Atlantic Ocean in regulating Asian westerlies, which may shed light on the behavior of westerlies in the future.

scholarly journals The Role of an Indian Ocean Heating Dipole in the ENSO Teleconnection to the North Atlantic European Region in Early Winter during the Twentieth Century in Reanalysis and CMIP5 Simulations

2021 ◽  
Vol 34 (3) ◽  
pp. 1047-1060
Author(s):  
Manish K. Joshi ◽  
Muhammad Adnan Abid ◽  
Fred Kucharski
Keyword(s):  
Indian Ocean ◽  
North Atlantic ◽  
Enso Event ◽  
Late Winter ◽  
Early Winter ◽  
The North ◽  
The Indian Ocean ◽  
The North Atlantic ◽  
Dipole Response

AbstractIn this study the role of an Indian Ocean heating dipole anomaly in the transition of the North Atlantic–European (NAE) circulation response to El Niño–Southern Oscillation (ENSO) from early to late winter is analyzed using a twentieth-century reanalysis and simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5). It is shown that in early winter a warm (cold) ENSO event is connected through an atmospheric bridge with positive (negative) rainfall anomalies in the western Indian Ocean and negative (positive) anomalies in the eastern Indian Ocean. The early winter heating dipole, forced by a warm (cold) ENSO event, can set up a wave train emanating from the subtropical South Asian jet region that reaches the North Atlantic and leads to a response that spatially projects onto the positive (negative) phase of the North Atlantic Oscillation. The Indian Ocean heating dipole is partly forced as an atmospheric teleconnection by ENSO, but can also exist independently and is not strongly related to local Indian Ocean sea surface temperature (SST) forcing. The Indian Ocean heating dipole response to ENSO is much weaker in late winter (i.e., February and March) and not able to force significant signals in the North Atlantic region. CMIP5 multimodel ensemble reproduces the early winter Indian Ocean heating dipole response to ENSO and its transition in the North Atlantic region to some extent, but with weaker amplitude. Generally, models that have a strong early winter ENSO response in the subtropical South Asian jet region along with tropical Indian Ocean heating dipole also reproduce the North Atlantic response.

scholarly journals North Atlantic Oscillation Response to Anomalous Indian Ocean SST in a Coupled GCM

2005 ◽  
Vol 18 (24) ◽  
pp. 5382-5389 ◽  
Author(s):  
Jürgen Bader ◽  
Mojib Latif
Keyword(s):  
Indian Ocean ◽  
North Atlantic Oscillation ◽  
General Circulation Model ◽  
North Atlantic ◽  
General Circulation ◽  
Circulation Model ◽  
Atlantic Sector ◽  
The North ◽  
The Indian Ocean ◽  
The North Atlantic

Abstract The dominant pattern of atmospheric variability in the North Atlantic sector is the North Atlantic Oscillation (NAO). Since the 1970s the NAO has been well characterized by a trend toward its positive phase. Recent atmospheric general circulation model studies have linked this trend to a progressive warming of the Indian Ocean. Unfortunately, a clear mechanism responsible for the change of the NAO could not be given. This study provides further details of the NAO response to Indian Ocean sea surface temperature (SST) anomalies. This is done by conducting experiments with a coupled ocean–atmosphere general circulation model (OAGCM). The authors develop a hypothesis of how the Indian Ocean impacts the NAO.

Submarine gravity measurements in the Atlantic Ocean, Indian Ocean, Red Sea and Mediterranean Sea

1957 ◽  
Vol 239 (1217) ◽  
pp. 202-213 ◽  
Keyword(s):  
Indian Ocean ◽  
Atlantic Ocean ◽  
Mediterranean Sea ◽  
Red Sea ◽  
North Atlantic ◽  
Isle Of Wight ◽  
The North ◽  
Gravity Measurements ◽  
The Indian Ocean ◽  
The North Atlantic

The results are given of fifty-eight gravity measurements made at sea in H. M. Submarine Acheron between April and October 1955. Of these, six lie in the North Atlantic, eight in the South Atlantic and thirty-seven in the Indian Ocean. The remainder are in the Red Sea (four), the Mediterranean Sea (two) and off the Isle of Wight (one).

scholarly journals Whaling Bans – Another Inch Forward

Oryx ◽  
1981 ◽  
Vol 16 (2) ◽  
pp. 123-124
Author(s):  
Richard Fitter
Keyword(s):  
Indian Ocean ◽  
North Atlantic ◽  
Sperm Whales ◽  
Whale Watching ◽  
Remarkable Feature ◽  
International Whaling Commission ◽  
Conspicuous Feature ◽  
The North ◽  
The Indian Ocean ◽  
The North Atlantic

At this year's International Whaling Commission meeting, where ‘horse trading’ between whalers and conservationists was again a conspicuous feature, sperm whales got a respite, but at the expense of the North Atlantic fin whales. For the British ngo-s, banded together in Wildlife Link (which includes ffPS), the main disappointment was the failure of all three major proposals to halt whaling altogether. They now look to a future where hunting has been given up for lack of whales to hunt, and whale-watching takes over. A remarkable feature of the meetings was the leadership of the Seychelles Government, which last year succeded in getting the Indian Ocean Sanctuary for whales.

Sign in / Sign up

Export Citation Format

Share Document