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As the ocean cools

Dr Sushil K Sharma
Wednesday, December 06, 2017

AS we approach 2018, the waters in central and eastern equatorial Pacific region, covering about 90 per cent of the entire tropical Pacific Ocean, continue to cool unabated.

This cooling is of gigantic proportions and is expected to progress for the next three months, with the "tongue" of cold waters extending westwards, in the equatorial regions, past Nino 1, Nino 2, Nino 3, Nino 3.4 and Nino 4 regions, covering latitudes 80 degrees West to 170 degrees East, past the International Dateline at 180 Meridian.

Over thirty years of data (1961-1991) was used to derive the average oceanic temperatures of this vast region, with the present situation of oceanic temperatures dropping continually since August 2017, in each successive month, reaching very low threshold anomalies of 0.8C triggering the onset of a La Nina phenomenon.

Both the air temperatures and the deeper waters to hundreds of metres have cooled leading to negative anomalies. The temperatures are expected to cool even more, by as much as 1.2 C (from the 30-year average temperature for the region) creating the La Nina event for our region.

These magnitudes of anomalies are expected to persist for the summer season of December-January-February with the La Nina becoming the main weather and climate driver and modulator for the regional weather; cloudiness, floods, rains, and tropical cyclone genesis areas.

Fiji can expect this wet season summer (November 2017 to April 2018) enhanced activity in cloudiness, rains, thunderstorms, floods, and tropical cyclone genesis northwest of us, in the Coral Sea with the South Pacific Convergence Zone (SPCZ) much more pronounced and positioned over and just to our west.

Much more cloud activity will occur to the northwest and low pressure systems and depressions will run down trough lines in a northwest to southeast manner, across or just to the west. This will keep enhanced rains and cloudiness over Fiji.

Strong equatorial easterlies on the surface levels will keep the northwest monsoon at bay for a while, with strong vertical motion with enhanced convective activity Darwin-north Australia regions providing above average rains, cyclones and cloudiness.

Westerly winds in the troposphere and subsiding air over the eastern Pacific will maintain droughts over the eastern Pacific with colder day time temperatures over the vast tropical oceans. Seas will start to become lower and lower in the vast eastern regions, with elevated seas in the north western Pacific.

This natural 3-7 year natural cycle and variability is often confused as climate-change by novice non-scientists or those specifically uneducated in the hard-core climate-sciences and meteorological fields. Thus it is suggested that great care be taken to delineate what's happening on the ground. A pool of warm water may not necessarily be because of any long-term changes.

Over the next 3-5 months, Fiji can expect more blocked low pressure systems, providing more rains and floods. Convective activity will be greater and enhanced, with rains and floods, especially during periods when the nation is under the eastwards moving Madden-Julian Oscillation (MJO) pulse impact.

Intense cold water upwelling in the eastern Pacific from the great depth of the sea, aided by the Atmosphere-Ocean anticlockwise circulating gyre in the sea and anticyclone aloft in the upper atmosphere, will maintain subsidence with dry conditions aloft, clear skies, and strong easterly trade winds.

An abundant of anchovy and plankton population, upwelled by the very cold, nutrient rich Humboldt current in the sea, will mean an economic boom and a thriving fishing and canning industry, on the Peruvian coastal areas because of more than enough food for fish. The bird population in the coastal areas will increase because of increased food supply.

La Nina is a great "boon" to the livelihood of Peruvian fishermen and women.

The failing of this cold upwelling is called El Nino. La Nina is the brother of El Nino and the two are the opposite of each other. One warms the region, and the other cools it, driving our Walker Circulation, which modulates our weather and climate, in an irregular cyclical manner every 3-7 years. This is the natural variability of our weather and climate system; it is not climate-change.

Brother La Nina has the upper hand at the moment, and will provide this wet season to Fiji, floods, rains and landslides. Do you recall the 2009 and 2012 Western Division floods when Nadi, Ba, and Rakiraki were under water, and boats used where vehicles usually ran.

La Nina and El Nino come and affect us all the time, in a 3-7 year cycle; regulating our dry years and the wet years during our summer wet season (November to April) and the frequency and areal distribution of our tropical cyclones. It also affects our droughts and the events during our dry season.

You may recall that for nearly four years we have not had major floods like the 2009 and the 2012 ones. During this short period, I have seen so many developments in the West, totally in areas that I would not build on, even if someone gave me the land for free.

Fijians appear to have very short memories of floods and their impacts on life, property, health and hygiene. In the Lautoka to Nadi corridor and adjacent areas of those two municipalities, for example, people have literally built in old riverbeds and low-lying areas, which at times get flooded for a number of weeks and are totally under water with slush, mud and slime.

This was never an issue until now because of several factors.These areas have only recently become populated in a geometric fashion.

They have not experienced floods. The onset of the La Nina will surely teach many lessons to these entrepreneurs who have not experienced La Nina rains and floods.

As part of disaster mitigation work, Government should be fully aware of these issues and ensure planning permissions are not provided for big infrastructure projects, buildings, and homes in these areas. These areas can be reserved for other projects.

In any disaster, Government at the end of the day will have to pick up the cost for deaths, flood damages, building and relocation assistance, and the like.

The planet cools and warms simultaneously. We also have floods and droughts simultaneously on our planet. The issue is that these opposing elements are supposed to provide equilibrium to the elements, to ensure momentum, energy, temperature, moisture and heat are all conserved and in equilibrium.

La Nina onset to Fiji means we will have enhanced rains, floods, cloudiness, and intense convective and thunderstorm activity over us. The semi-permanent South Pacific Convergence Zone (SPCZ) will be prominently over and to the west of us.

Most of the cyclones will form to the far northwest of Fiji, in the Coral Sea and move westwards to Australia. Those approaching Fiji will come from the northwest with a lower risk to those coming from the northeast of Fiji.

Higher risk for those in Nadi, Lautoka, Ba, Tavua and Rakiraki, Yasawa and Mamanuca; Western and Northern divisions and lower risk for those in Suva, Navua and Nausori; the Central and Eastern divisions.

It appears at this stage the coming dry season will have above average rains next year (May-October 2018) which will be a relief after the dry of the past 3-4 years.

* Dr Sushil K Sharma is an associate professor of meteorology at the Fiji National University. Opinions expressed are his and not FNU's or this newspaper's.

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