Climate Controls and Temperature Changes Over Time

As most people know Fiji is a South Pacific volcanic island. This has effects on both the meso and micro-scale climate controls in the area.

Location of Fiji, in relation to Australia in the South Pacific Ocean. This location has significant meso-scale climate controls effecting it. Image: http://www.etravelblackboard.co.nz/article.asp?id=63145

Some of the greater meso-scale climate controls that have influence on Fiji are primary related to its location. Being a small island submits the area to have a climate that is at the will of the ocean surrounding it. Temperature fluctuations, as a result of seasonality, are barely noticeable. This is the result of the temperature being controlled by the surrounding waters. Water takes a very large amount of energy before it begins to gain sensible heat and it also doesn't lose it as easily, which is the opposite of how land reacts.

As discussed in the previous blog, Fiji is also greatly influenced by the ITCZ, and more specifically the SPCZ. This is what causes the heavy rain season on the island. While the SPCZ resides over Fiji very large amounts of rain occur, during the Northern Hemisphere winter months (November to April), and when the ITCZ begins to move back to the North the rainfall begins to lessen.

Suva's micro-scale climate controls are greatly related to the topography of the island. The island has a mountainous center and causes a barrier for the East to West wind movement. 

Map of Fiji showing the island of Viti Levu with Suva on the East side of the  mountain range. Winds move  East to West in the area and find the barrier of the mountains on the island. This has influences on the rainfall and storm development. Image: http://www.worldaccomodation.com/angol/continent/southpacific/fijiislands/vacationrentals.php

The mountains, with Mt. Victoria being the highest point, causes Orographic lifting to the air masses that move over the area. This result in the majority of the precipitation falling out of the air mass before it moves over the range. As a result, Suva receives significantly more rainfall than that of the West side of the island. About 117 inches a year compared to cities in the West like Nadi which receives about 71 inches of precipitation. 

Data gathered from the Hong Kong University

(http://www.hko.gov.hk/wxinfo/climat/world/eng/australia/pacific/nadi_e.htm)

Suva, though not being a large city, still produces a small heat island from the impermeable surfaces and buildings causing different energy balances than that of the natural environment. This isn't nearly as noticeable as other cities because of the size and the surrounding ocean. 

This is a graph of the average temperatures of July. A linear regression is added to each. From 1970 to 2012 there has been a slight increase in the average temperature. Only about a single degree centigrade. Data gathered from NOAA.

This is a graph of the average Temperatures of January. A linear regression was applied to both plots. From 1970 to 2012 January also showed an increase to overall temperature. The regressions so about 2.1 degree centigrade change for the maximum and a 1.5 degree centigrade change for the minimums.  Data gathered from NOAA.

From the graphs we can see a trending upward line. There could be a few factors resulting in this increase. It could be showing the overall climate change of the world increasing in temperature over this area. Or it could just be the result of micro-scale climate controls. Considering we can't really test to find out if this is the result of something like urban heat island or a warming trend in this area as the result of global climate change we can't make conclusions on it. We can just accept that there was a significant change of temperature in Suva from 1970 to now.


Contrary to the tropical island climate of Fiji, North Dakota is a land locked state in the U.S.A. This is nearly the polar opposite of Fiji sharing little to no similarities.

Location of North Dakota, residing in the North central of the United States.  

Being a land locked location with only a few sources of water around the state North Dakota is greatly influenced by seasonality. With the land gain and losing energy much more quickly than water, North Dakota has massive swings in temperature over the year. With highs around 85F in the summer, it is similar to Suva's highs, but through the transition to the winter, North Dakota drops to about 28F. The difference in temperatures being 57F compared to Suva's 10F degree fluctuations.

As we have seen Fiji is influenced by the ITCZ, whereas North Dakota is influenced by Polar air fronts. North Dakota is very far north and as a result can have long periods of dryness where as Suva receives moisture everyday. This is the result of the latitude of North Dakota, being far enough North to experience polar air masses dominating the area. On occasion a mid latitude cyclone can make it's way far enough North to deliver the moist maritime front to the polar front result in precipitation, but it doesn't occur very often. There are also Pacific fronts that occasionally come through. The result is cold dry winters. 

On a micro-scale view we can see that North Dakota doesn't have much in the terms of elevation change. The mountain range in Suva causing the rain shadow in the West of the island is something that is unknown to North Dakota. It isn't Nebraska, but there are definitely no mountains. It would probably be to dry for the hills in the Southwest to create any rain shadow.

Southwest North Dakota in the Badlands area. The topography is pleasent to look at, but doesn't influence the climate in the same way that the mountains in Fiji do. Image: http://wikitravel.org/upload/en/thumb/8/82/Badlands1.jpg/250px-Badlands1.jpg

The view of the mountains from Suva. Rarely is very clear to see the extent of how far they continue back. Considerably larger than North Dakota terrain. Image: http://mw2.google.com/mw-panoramio/photos/medium/69556144.jpg

An Island in the South Pacific

Fiji being a South Pacific island doesn't have as many air mass influences as we have seen in Colorado. The island is East of Australia and Indonesia with Suva sitting at about 18 degrees South of the equator. This puts it in the prevailing winds of the Southeast Trades. This causes the air masses to be mT or maritime tropical over the entirety of the year. However, even though it is mT throughout the year there are other factors that effect the island that create significant changes in the weather showing up in seasonal weather patterns.

The general prevailing winds of the world. Sitting above the Tropic of Capricorn , you can see the East  to West winds of the Southeast Trades. Image : http://www.fccj.us/gly1001/tests/10Ch18L.htm

The Intertropical Convergence Zone (ITCZ) has great effect on Fiji. Residing in the South Pacific with little land to heat up and move the ITCZ results in a very significant affect on the weather of Fiji. It is known as the South Pacific Convergence Zone (SPCZ). It is a branch off the ITCZ. It has very little dependence on land heating and thus tends to stay in the same location year round. Convergence of the trade winds to the monsoon winds cause the convergence zone to form. 

The SPCZ over the Pacific Ocean in February. There is massive convergence over the islands in the South Pacific. This is  where Fiji resides and is what causes the seasonal weather that the islands face. Image: http://www.nrlmry.navy.mil/~chu/chap2img/fig204.jpg

This is the SPCZ during August over the Pacific Ocean. You can still see that it is still occurring, but is not as big. Image:  http://www.nrlmry.navy.mil/~chu/chap2img/fig204.jpg

From this we can see how the ITCZ effects Fiji. Large amounts of rainfall occur from November to April, and it tends to be dry from May to October. This coincides with the ITCZ. There are other things that determine the weather of the main island, Viti Levu, with the capital Suva on it. 

Being formed by volcanic processes the island is essentially a large mountain in the ocean. The ridge sits in the center of the island and causes localized weather on either side. Suva sits on the windward side of the mountain ridge and the storms also flow from East to West on the island. This causes large amounts of rain to fall on the East side of the mountain ridge causing it to be much more tropical, while the leeward side of the mountain ridge has a climate that is much dryer. This is very similar to what we experience in the lee of the Rockies. 

There may be very slight adiabatic heated winds on the lee side of the mountain ridge in Nadi, but they are probably less extreme than the Rockies. The highest point sits at 4340' so there is height for the air to heat up on the decent. Sitting in the SPCZ is unique, being the largest water convergence zone and it causes most of the weather in Fiji. 

This shows the SPCZ during the rainy months of the year. It passes right through the South Pacific and shows the convergence area. It shows the very low sea pressure areas. Storms form with this convergence.  Image: http://www.niwa.co.nz/sites/default/files/imported/__data/assets/image/0010/37945/olr_600.gif

These factors explain why Fiji experiences the weather it does. Being a volcanic island with a large mountain ridge residing in the middle, with mT air masses year round, and residing the area of the SPCZ, the weather and climate of Fiji is governed by these factors.