 |
 |
|
|
Abstract:
Atmospheric aerosol particles, both natural and anthropogenic, play an important role on the radiation balance of the earth-atmosphere system. They affect the energy budget directly by scattering and absorbing sunlight and indirectly by modifying the radiative properties and lifetime of clouds. It is generally believed that the aerosol radiative forcing at the TOA is comparable in magnitude to current anthropogenic greenhouse gas forcing but opposite in sign. However, current estimates of global aerosol radiative forcing at the TOA are based on model simulations where there are too few observations to constrain the model input and its assumptions of various aerosol related chemical, microphysical, meteorological and radiative processes. Therefore, our quantitative understanding of aerosol forcing still remains uncertain. Satellite remote sensing is a powerful tool for monitoring the spatial distribution of aerosols and for studying the role of aerosols on climate. We present an overview of the different methods used to study the radiative effects of aerosols and examine the potential of using satellite measurements for studying air quality.
Abstract:
If the wind blows steadily from the north in the Southern Hemisphere, the action of the Coriolis force results in surface waters being pushed in an eastward direction. Along a north-south oriented coastline, the water pushed offshore is replaced by nutrient-rich cold water from the deep, resulting in a bloom of phytoplankton in the surface waters. This talk will look at the response of the micro-organisms off the NSW coast to a northerly and southerly wind. Numerical simulations will be shown to illustrate the process.
About the speaker:
Mark did a Mechanical Engineering degree at Sydney University, a Masters in Oceanography from the University of Hawaii, and a PhD in Biological Sciences from Warwick University in the UK. He has worked at CSIRO, and, since 2001, at UNSW, on the effects of physical processes on aquatic ecosystems. An engineer at heart, with a passion for oceanography, he tries not to be too much of a reductionist when looking at the fascinating biological systems in our marine waters.
Abstract:
The talk will discuss how the concept of 'logistic regression' can be used to generate probability forecasts of binary [yes/no] weather events that can be used operationally in weather forecasting. Examples will be given for fogs, frost and also snow/rain, conditional on it precipitating in the first place. Since the concept can be adapted to any variable that can be considered a yes/no, there are endless opportunities for the concept to be applied to research in this field, and beyond. An advantage of probability forecasts is that they can be utilised by different users to suit their own circumstances. A disadvantage being that they are not clear cut, as is the case of a yes/no forecast. These pluses/minuses will be explored via a couple of examples, showing how an intelligent use of probability forecasts will generate greater economic value over any categorical yes/no forecast.
Abstract:
The first in-depth hail climatology for New South Wales, based on reports of hailstones from 1791 to 2003 is described. The focus is on the greater Sydney area, which experiences an average of 10 hailstorms per year with the hail season lasting from August to February, and hailstorms generally occurring during the late afternoon between 2pm and 6pm. However a statistically significant decrease in the annual hailstorm frequency from 1989 to 2003 compared to the preceding 36 years was found together with a season shift to November to March. Hailstorms occur most frequently between October and February and during the late afternoon between 3pm and 7pm in NSW. The magnitude of hailstorms, as measured by hailstone size, reveals an average maximum hailstone size per storm of 4.0cm. The most active hail fall regions are located in the Northern Tablelands, Northern Rivers as well as parts of the Northwest Slopes. In metropolitan Sydney, the most hail-prone suburbs are concentrated over the most densely populated areas and corridors.
A study investigating the potential use of weather radar to estimate hail damage to buildings is described. Comparisons of the radar reflectivity with hail damage in the form of insurance claims and calls for assistance to the State Emergency Services are presented for recent severe hailstorms including the April 1999 Sydney hailstorm. The area defined by a radar reflectivity equal to or greater than 55dBZ appears to be a good approximation of the damage and hail swath on ground. The preferred area for hail damage is to the left of the storm path, as defined by the centroid of the 55dBZ hail cells and corresponds well with larger hailstone sizes. Merging hail cells appear to cause a substantially higher emergency response intensity. Hail damage threshold to buildings could be identified.
About the speaker:
Sandra Schuster is currently finishing a PhD with Risk Frontiers, the Natural Hazards Research Centre at Macquarie University. She is supervised by Emeritus Professor Russell Blong, Professor John McAneney and Dr Milton Speer. The work being presented here is part of her thesis; the investigation of severe hailstorms in metropolitan Sydney using observations, weather radar, insurance claims and emergency calls.
Sandra graduated in Meteorology/Atmospheric Physics from the University of Kiel, Germany. She has worked in Germany, Cambridge UK (British Antarctic Survey) and the Arctic. Her research topics considered sea ice and climatic changes in Polar Regions. This involved simulations with global climate models (GCMs) as well as drilling holes to measure the sea ice thickness on the North Pole.