Physicist happens upon rain data breakthrough

NASA: A physicist and researcher who set out to develop a formula to protect Apollo sites on the moon from rocket exhaust may have happened upon a way to improve weather forecasting on Earth.

Working in his backyard during rain showers and storms, John Lane, a physicist at NASA's Kennedy Space Center in Florida, found that the laser and reflector he was developing to track lunar dust also could determine accurately the size of raindrops, something weather radar and other meteorological systems estimate, but don't measure.

The special quantity measured by the laser system is called the "second moment of the size distribution," which results in the average cross-section area of raindrops passing through the laser beam.

"It's not often that you're studying lunar dust and it ends up producing benefits in weather forecasting," said Phil Metzger, a physicist who leads the Granular Mechanics and Regolith Operations Lab, part of the Surface Systems Office at Kennedy.

Lane said the additional piece of information would be useful in filling out the complex computer calculations used to determine the current conditions and forecast the weather. "We may be able to refine (computer weather) models to make them more accurate," Lane said. "Weather radar data analysis makes assumptions about raindrop size, so I think this could improve the overall drop size distribution estimates."...

John Lane looks over data recorded from his laser system as he refines his process and formula to calibrate measurements of raindrops. Photo credit: NASA/Jim Grossmann

New insights into cloud formation

Science Daily: Clouds have a profound effect on the climate, but we know surprisingly little about how they form. Erika Sundén has studied how extremely small cloud particles can dispose of excess energy. This knowledge is necessary to understand processes in the atmosphere that affect global climate change.

The models that have been built to describe climate change contain a major source of uncertainty, namely the effects of clouds. The UN Intergovernmental Panel on Climate Change points out in its climate report for 2007 that new knowledge is needed in this field.

It is namely the case that clouds can act in two ways: they may be a mirror that reflects radiation from the sun back into space, and they may be a blanket that seals in the heat emitted by Earth. Mapping the formation and dispersion of clouds may, therefore, be a key step in climate research. "One important stage is understanding the fundamental properties of the particles involved," says Erika Sundén, doctoral student at the Department of Physics, University of Gothenburg.

..."I investigated water clusters that contained a small fraction of ammonia, and compared these with pure water clusters. I was able to show that the ammonia contributed to the stability of the clusters, and prevented them evaporating so rapidly. It may be that ammonia plays an important role in the early stages of cloud formation," she says.

It is not easy to measure the heat capacity of clusters, and an important part of her research has been to develop a method that can be used in future studies. Put simply, you could say that she has created water clusters in air, drawn them into a vacuum, and then examined them as they disintegrate. This method led her to an unexpected discovery.

"The temperature inside these clusters was around -100 °C, so one would expect that their heat capacity would correspond to that of ice. Despite this, the heat capacity of medium-sized clusters was greater, intermediate between that of ice and liquid water. The importance of this for how clouds form will be the subject of further research," she says...

A rolling thunderstorm in the Netherlands, shot by John Kerstholt., Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license

Modelling dam breaks, tsunamis and other geophysical events

CSIRO (Australia): CSIRO mathematicians are creating computational models of events like floods, dam breaks and tsunamis to aid understanding and planning for these phenomena. Catastrophic events like floods, dam breaks, tsunamis, storm surges, volcanic eruptions, and mud slides involve large-scale movement of fluids and solids. They can have serious economic, environmental and humanitarian effects.

These geophysical flow events are difficult to observe and measure. They are also very complex to model because they involve:

• movement of solids and fluids in large volumes over large areas
• many kinds of physical processes
• events occurring over an expanse of time and space.

New geophysical flow modelling techniques developed by CSIRO can be used to assist at-risk regions and nations by accurately visualising potential disaster scenarios to allow evidence-based decision making for emergency services management.

CSIRO has been developing computational fluid dynamics (CFD) methods, specifically particle-based smoothed particle hydrodynamics (SPH) code and granular flow (GF) code, to accurately model events like dam breaks and tsunamis using real three-dimensional (3D) topography obtained from digital terrain models. Using real topographic information means the results can be directly compared with disaster scenarios. Particle-based methods for modelling geophysical flows have numerous advantages over traditional grid or mesh-based continuum methods....Projects currently being undertaking using these methods include:

• refining a 3D simulation of the 1928 St Francis Dam break in California. Results from the computer simulation agree closely with historical data about damage from the real event.
• modelling the hypothetical collapse of China's Geheyan Dam, one of the world's largest dams. This project is a collaboration with the Chinese Academy of Surveying and Mapping.
• simulating a hypothetical flood of the Bellinger River in NSW, due to a storm surge
• predicting areas affected by a hypothetical tsunami inundating the Californian coastline
• dynamic prediction of flooding in several Australian cities due to dam breaks, tsunamis, floods and other disasters….

The St. Francis dam before it was destroyed in 1928