Teleconnections

It became clear after the collecting of weather data during the International Geophysical Year of 1957 that variations like that of the Southern Oscillation are not confined to the Pacific ocean (Figure 12.17). That year happened to be a major El Niño year (Figure 10.16) and the IGY involved collecting data worldwide. The data showed that the Walker circulation in the Pacific intermeshes with similar east-west circulations right round the globe at low latitudes, as well as with the meridional Hadley cells. So pressure anomalies at Darwin coincide with anomalies far away,

Table 12. 1 Association of high values of the Southern Oscillation Index * with large areas of high rainfall in the eastern states of Australia during the period 1933-87

Table 12. 1 Association of high values of the Southern Oscillation Index * with large areas of high rainfall in the eastern states of Australia during the period 1933-87

Notes:

* The annual SOI is the average of the monthly SOIs, as defined in Section 12.7

t 'Low' rainfall means that the annual total at a place was within the lowest three deciles of measurements there (Section 10.4). The deciles were obtained by ranking the annual rainfalls in ascending order to determine the smallest 30 per cent of the fifty-five values, t 'Normal' rainfall here means that the annual total at each place fell in the middle four deciles § 'High' rainfall means that the annual total at each place fell within the highest three deciles

|| This figure was derived from fifty-five annual totals of rainfall at each of many places within the easternstates of Australia. For each place, the fifty-five values were ranked and divided into deciles, so that a decile could be allotted for each year. In any particular year the appropriate decile value for every place was mapped, allowing calculation of the average decile for the whole region for that year. In the fourteen years with low SOI values, 47 per cent of the region, on average, had low rainfall, 41 per cent had normal rainfall, and 11 per cent had high rainfall. The most likely rainfall regime is highlighted in bold.

Notes:

* The annual SOI is the average of the monthly SOIs, as defined in Section 12.7

t 'Low' rainfall means that the annual total at a place was within the lowest three deciles of measurements there (Section 10.4). The deciles were obtained by ranking the annual rainfalls in ascending order to determine the smallest 30 per cent of the fifty-five values, t 'Normal' rainfall here means that the annual total at each place fell in the middle four deciles § 'High' rainfall means that the annual total at each place fell within the highest three deciles

|| This figure was derived from fifty-five annual totals of rainfall at each of many places within the easternstates of Australia. For each place, the fifty-five values were ranked and divided into deciles, so that a decile could be allotted for each year. In any particular year the appropriate decile value for every place was mapped, allowing calculation of the average decile for the whole region for that year. In the fourteen years with low SOI values, 47 per cent of the region, on average, had low rainfall, 41 per cent had normal rainfall, and 11 per cent had high rainfall. The most likely rainfall regime is highlighted in bold.

\

-Darling River „

I

/'M

/

XSOI

>

J

J,

Was this article helpful?

0 0
Renewable Energy Eco Friendly

Renewable Energy Eco Friendly

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable.

Get My Free Ebook


Post a comment