Friday, 17 June 2011

Smouldering mega fire in North Carolina Wildlife Refuge

A peat fire has been burning in North Carolina since May 4 inside the Alligator River National Wildlife Refuge. It is only 75% contain so far, and the higher summer temperatures are arriving fast. It could burn for several more months.

It is believed to had started with a lightning strike [ref]. A recent local article reports "crews pump millions of gallons of water on stubborn ground fire that is part of the larger Pains Bay fire"

This brings reminisces of the 2008 Evans Road fire in the Pocosin Lakes National Wildlife Refuge (NC, not far from Alligator River National Wildlife Refuge). The initial flaming fronts were controlled within days, but the smouldering fire burned for 6 more months and consumed the organic soil down to 1 m deep (see hanging tree in the 2008 photo). 16000 ha were destroyed (2 times the year average for North Carolina). More than 400 firefighters stopped this smouldering mega fire by flooding and excavating the peat. Estimated costs in suppression alone are near $20 million. It was also believed to had started with a lightning strike.

Note that as opposed to flaming fires of forest land that can regrow in 50 to 100 years, peat is a pre-fossil fuel (or ancient carbon as Andy Revkin labelled in his twit), it takes >10,000 year to form. Thus peat fires are a net source of carbon emissions and provide a positive feedback to climate change. This accidental fossil-fuel burning taking place now releases carbon that will not be recaptured by new peat until the year 12011. By then, the Earth climate system had plenty of time to response and lead to a possible global change. I discussed this a recent talk I gave at the last European Geoscience Union, see previous blog entry here and insert below. The title was "Climate Feedbacks on Smouldering Earth".

Climate Feedbacks on Smouldering Earth (talk at EGU Vienna 2011)

Wednesday, 15 June 2011

Bifurcations and Forecasting Scenarios - in CO2 emissions

I was quickly reading over a new paper on renewable energy policy [Krey and Clarke 2011], and realized that there is a visual link between global CO2 emission predictions and a bifurcation diagram.

The bigger plot below shows "Historic and projected global fossil and industrial CO2 emissions across all scenarios between 1900 and 2100",  Figure 1 in Krey and Clarke 2011. The red-frame insert is the bifurcation diagram of the the logistic equation taken from here.

From Wikipedia: bifurcation diagram shows the possible long-term values (equilibria/fixed points or periodic orbits) of a system as a function of a bifurcation parameter in the system. It is usual to represent stable solutions with a solid line and unstable solutions with a dotted line.

Granted that the link is more visual than fundamental, and requires an artistic licence of some degree. Note that the first bifurcation starts at the point separating historical values from projected (aka predicted) values. Thus, history is the stable solution, and forecasts are unstable solutions, the source of the uncertainty. This could hint towards a new topic for the application of NKS (New Kind of Science) approach and his reliance on cellular automata similar to the logistic equation to explain complex systems.

Wednesday, 8 June 2011

Inaugural Lecture on Multiscale Modelling of Tunnel Fires

Last Wednesday 1 June, I gave this Inaugural Lecture on Multiscale Modelling of Tunnel Fires at the I Fire Engineering Conference at Universidad Politecnica de Valencia.

The lecture is based on the PhD thesis of Francesco Colella (2010), my second PhD student.

Multiscale Modelling of Tunnel Fires


Tunnels represent a key part of the world infrastructure with a role both in people and freight transport. Past events show that fire poses the most severe threat to safety in tunnels. Indeed in the past decades over four hundred people worldwide have died as a result of fires in road, rail and metro tunnels. In Europe alone, fires in tunnels have brought vital parts of the road network to a standstill and have cost the European economy billions of euros. Within this safety strategy, the ventilation system plays a crucial role because it takes charge of maintaining tenable conditions to allow safe evacuation and rescue procedures as well as fire fighting. Throughout most of a tunnel network the ventilation behaviour may be approximated with a simple 1D flow model. However, there are some important - but relatively small - regions of the tunnel that require CFD analysis. The multi-scale model is the ideal tool for such tunnel studies as it allows accurate flow field predictions in some locations, yet allows simplifications where highly detailed data are not required. It is shown that the accuracy of the multi-scale model is as high as the full CFD approach. The 100 times lower computational time is of great advantage because many ventilation scenarios can be explored and extensive sensitive parametric studies can be conducted.