Impact of the Indian Ocean high pressure system on winter precipitation over western and southwestern Australia

Hameed, Sultan; Iqbal, Muhammad Jawed; Rehman, Saqib-Ur; Collins, Daniel J.

doi:10.22499/2.6103.002

Cited by 20 publications

(8 citation statements)

References 33 publications

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“…They investigated the impact of the longitudinal displacement of the Aleutian Low on the circulation in the North Pacific, thus introducing the concept that the movements of the atmospheric pressure centers can be used as indicators of regional circulation changes. This concept has been successfully applied to explain the variability in many geophysical systems [2,3,12] and will also prove useful in the present investigation, where we will see that the longitudinal displacements of the Azores High pressure center significantly impact circulation over North Africa, and therefore, precipitation amounts over the Sahel region.…”

Section: The Atmospheric Centers Of Actionmentioning

confidence: 80%

“…The Azores High is located to the west of North Africa and this configuration is similar to that of the Indian Ocean High with respect to western Australia. It has been shown that east-west shifts in the position of the Indian Ocean High significantly influence rainfall in southwestern Australia where a multidecadal drought is in progress [12]. Thus, there are similarities between the relationships between the longitudinal displacements of the two subtropical highs and drought in the continents to their east.…”

Section: Influence Of the Azores Highmentioning

confidence: 99%

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Relationship of Sahel Precipitation and Atmospheric Centers of Action

Hameed

Riemer

2012

Advances in Meteorology

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The dynamics associated with drought in the Sahel have attracted considerable attention in the recent literature. This paper evaluates Sahel precipitation using the paradigm of the atmospheric centers of action, that is, the extended semipermanent highs and lows that dominate regional circulations and are evident in sea level pressure patterns. We find that Sahel precipitation is significantly influenced by changes in the Azores High and the South Asia Low. Specifically, about 50 percent of the variance of July to September rainfall over the Sahel is explained by changes in the Azores High Longitude position and South Asia Low pressure. In contrast, the contribution of the Southern Oscillation to Sahel precipitation is smaller in comparison. Results presented in this paper suggest that a key test for a climate model in simulating variability of Sahel rainfall is the accuracy with which the model simulates the dynamics of South Asia Low and the Azores High.

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Section: The Atmospheric Centers Of Actionmentioning

confidence: 80%

Section: Influence Of the Azores Highmentioning

confidence: 99%

Relationship of Sahel Precipitation and Atmospheric Centers of Action

Hameed

Riemer

2012

Advances in Meteorology

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“…Rossby et al [13] found not only the intensities but also the locations of the sea level pressure centers influence the associated regional climate. Hameed et al [14] investigated the center of high pressure over the subtropical Indian Ocean and found its association with the winter (May-August) rainfall declined over Southwest Western Australia (SWWA) over the period from1951-2008. We have observed that during above average of MSLP categories (high anticyclones frequency composite maps) the average rainfall over the coherent districts was below average while during below average of MSLP categories (lowest anticyclones frequency composite maps) the average rainfall over the coherent districts (Fig.…”

Section: Resultsmentioning

confidence: 99%

The Impact of Subtropical Indian Ocean Anticyclone over Tasmania Precipitation

Usmani

Saqib-Ur-Rehman

Khan

et al. 2019

CJAST

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Aims: To explore the association between observed frequency of anticyclones over subtropical Indian Ocean (10°S-50°S, 102.5°E-142.5°E) and average autumn rainfall over the districts of Tasmania. Methodology: We have divided the rainfall amounts over nine districts of Tasmania into three categories (Above average, average and below average rainfall) by using z-scores technique for each autumn (March-May) month for the period of 1951-2016. We have also categorized the calculated frequency of anticyclone over the subtropical Indian Ocean in a similar fashion. Results: Our analysis suggests inverse association between each category of average rainfall and the corresponding frequency of anticyclones for each month of autumn. This association revealed that during below average rainfall, the high frequencies of anticyclones were occupied over the most of the area of subtropical Indian Ocean that resulted less rainfall in the districts while during above average autumn rainfall, the high frequencies of anticyclones observed in the west of 110°E this enabled more autumn rainfall over the districts. We have also found the negative correlation coefficients between mean sea level pressure over the same domain of Indian Ocean and average rainfall over each district in each month of the autumn (March-May). Conclusion: The slightly shift of Mean Central Pressure (MCP) to the north from the west coast of Tasmania from March-May enabled the extra-tropical activity of rainfall systems. This causes enhanced rainfall during average and above average rainfall conditions than March-April over nine districts of Tasmania.

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“…We also analyzed the influence of the eastward (IOHLN) and southward (IOHLT) shifts of the high pressure centers on the southwest coastal division runoff variability. The term IOHP has been frequently used in many studies [e.g., Hameed et al 2011, Rehman and. As shown in Figure 8a,b, during the early winters when the MCP of the IOHP was at a maximum, the component bar has the lowest mean principal component score, which shows that less streamflow occurred for the southwest coastal division.…”

Section: Impact Of Iohp and Iohln On The Streamflow Variabilitymentioning

confidence: 99%

Influence of Indian Ocean high pressure on streamflow variability over southwestern Australia

Rehman

2014

Annals of Geophysics

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The seasonal and interannual variability of the southwestern Australia streamflow was examined based on re-analysis dataset from the National Centers for Environmental Prediction / National Center for Atmospheric Research, plus monthly streamflow data from 17 meteorological stations obtained from the Department of Water of the Australian Water Resource Council (1976-2008). Significant findings reveal that since the middle of the last century, the early winter (May-August) streamflow variability over southwestern Australia has been associated with variability in the intensity of the Indian Ocean high pressure (IOHP) system, as well as the zonal movement of the high pressure system across the Indian Ocean. Of note, however, the emphasis in the previous studies has linked the ongoing winter drought in western Australia to changes in sea level pressure, both on a local basis and over larger areas. We introduce objective indices for the area-weighted pressure of the IOHP, and the IOHP area-weighted latitude (IOHLT) and longitude (IOHLN) positions. When the IOHP is shifted to the east, there is less streamflow in the southwestern Australian rivers that are examined in this study. The situation is reversed when the IOHP is shifted to the west, when there is more streamflow in the southwestern Australian rivers. The characteristics of the streamflow pattern are determined for the river catchment areas located around the coastal region over southwestern Australia using principal component analysis. The first principal component taken into consideration describes 84.43% of the total variance. The multiple correlation between the loading of the first principal component scores of the streamflow and the IOHP and IOHLN is 0.54, while the correlation between the southern oscillation index is 0.44. Centers of action indices explain 29% of the streamflow variability, while the southern oscillation index explains only of the 19% streamflow variability. This discovery is of real importance for the definition of the physical mechanism of seasonal (May-August) streamflow variability of southwestern Australian and the IOHP.

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Impact of the Indian Ocean high pressure system on winter precipitation over western and southwestern Australia

Cited by 20 publications

References 33 publications

Relationship of Sahel Precipitation and Atmospheric Centers of Action

Relationship of Sahel Precipitation and Atmospheric Centers of Action

The Impact of Subtropical Indian Ocean Anticyclone over Tasmania Precipitation

Influence of Indian Ocean high pressure on streamflow variability over southwestern Australia

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