Winter is (not) coming: bushfires and other disasters

 

Introduction: the dipole of the Indian Ocean

Recently we all have read a lot about the fires in Australia which are damaging the entire ecosystem.

Unfortunately fires are intrinsic in that area. In the past, other events like this occurred, like for instance the terrible fire in february 2009.

During the month of  december 2019  the precipitations in Australia have been very low and this caused a strong and extended drought.

The lack of precipitations  and the increase of  the average temperatures represent a very bad combination, so this raises the risk of fires.

One of the most important  meteorological factors at stake is the dipole of the Indian Ocean.

As my physics professor used to say, dipole is just a system made of  two electrical charges with opposite sign.

In this case the word “dipole” refers to the difference between the superficial temperature of the sea in different regions.

This year temperatures were much higher in the western part of the indian ocean.

In the eastern part the trend was the opposite, so that’s why  there were intense rainfall events in eastern Africa while drought prevailed in Asia and Australia.

With the increase of greenhouse gases emissions, the countries close to the african coast will experience more intense rainfall events.

 

The problems related to bushfires

 Now that we know what are bushfires influenced by, we need to talk about one of the main risks related to them.

Indeed bushfires can also create their own clouds, called “ pyrocumulonimbus” , kind of large smoke plumes.

 

How is it possible?

First, a plume of warm and turbulent air rises.

Because of the turbulence, cold air is mixed in the plume. As the plume rises, the  atmospheric  pressure is reduced so the volume of the plume increases and it cools down.

Once the moisture in the clouds condenses, the clouds are formed: a lot of clouds, an “empire of  clouds”. If you don’t know this song from Iron Maiden please check the album “ The book of souls” as soon as possible.

 

Due to this condensation, latent heat is released, so this makes the cloud warmer.

The upper part of these clouds still remain cold and collisions of  ice particles take place  increasing the electrical charge: this is how the thunderstorm starts.

 

Lighting might be produced and therefore create new fires, "setting fire to the rain.”  

(sorry Adele)

Of course these clouds are very dangerous as in this way fires can spread very quickly. Foreseeing these kind of events is not easy due to the complex iteractions between different variables (relative humidity, atmospheric pressure).

Limiting the greenhouse gases emissions is important to improve the air quality and to control the temperature.

A lot of researchers are rightly focused about the impact of fossil fuels on air pollution, but there is another big problem related to oil and gas industry: coastal erosion.

 

A case study: the Wetlands in Louisiana

Wetlands started disappearing below the Gulf of Mexico more than 15 years ago.

Indeed a lot of canals cross the wetlands, enhancing the erosion process.

The coast of Louisiana was actually created by the Mississipi river.

The embankments constructed during the thirties stopped all the flood events which  used to transport sediments towards the wet zones. At the end of the sixties  some navigable canals were dredged, oil and gas societies started opening canals for wells and pipelines. The subsequent waste of wetlands was huge, due to the increase of the sea level and subsidence (sinking of the ground’s surface).

 

What are the possible solutions for erosion?

 

There is the possibility of alternating embankments and spillways. This technique has already shown some good result for the remediation of marshes, but even with  these interventions the coast will never be like before.

Recently also geotextiles, green belts and artificial reefs are being used to mitigate coastal erosion. Green belts are just a barrier of trees which can protect the coast from the waves.

Artificial reefs  can be made of polythene bags filled with sand, but also concrete, scrap tires, construction rubble. In the Philippines there are even a lot of articial reefs  made of  waste tires. These innovative methods for erosion prevention are taking the lead, as classic techniques like seawalls reduce the coastal erosion but might  damage the beach (down drift erosion).

What is important  to highlight is that there is no best method, every area has its own conditions and characteristics.

To find the most suitable methods the hydrodinamics of the site needs to be evaluated carefully; the interactions between water and sediments have to be well known.

From this point of view, modeling might really help us to understand what will happen to the coast and to prevent the risks.

On one hand we want to take into account as many parameters as possible to get  accurate predictions, on the other side taking into account a large amount of variables might increase the possibility of making mistakes ( wrong measurements, uncertainty) .

Both coastal erosion and air pollution are strongly influenced by atmospheric pressure, wind, temperature and of course relative humidity.

By getting a deeper understanding of how these parameters vary in different environmental conditions, we can definitely  improve the risk prevention.

When it comes to something like bushfires it is always harder to make predictions, but now thanks to the new technologies  available it is possible to collect a lot of updated environmental data.

The further step might  be forming  a network of institutions in charge of understanding what these numbers are trying to tell us before nature does it. By creating a big database it could be possible to  spot some anomalies  in advance. If we know that a specific combination of relative humidity and pressure lead  to a storm  in a certain area 3 years ago, the recurrence of the same conditions  (even in a different location) will definitely ring a bell.  

 

 

Giulia Ioselli