Scientists expect sand flow on East Coast to slow

The following news pieces have been picked up by various sources from a paper published late last year in the Journal of Geophysical Research, Oceans titled “Tropical and extratropical-origin storm wave types and their influence on the East Australian longshore sand transport system under a changing climate” by Ian Goodwin, Thomas Mortlock and Stuart Browning. Thomas Mortlock is a member of the Risk Frontiers’ team and Ian Goodwin and Stuart Browning are members of the Marine Climate Risk Group at Macquarie University.  Click here to read entire article.

Aerial view of Byron Bay. Source: Swellnet Analysis

Scientists expect sand flow on East Coast to slow. Swellnet Analysis. https://www.swellnet.com/news/swellnet-analysis/2016/07/27/scientists-expect-sand-flow-east-coast-slow

Why Qld beaches will lose their sand to NSW. The Chronicle. http://www.thechronicle.com.au/news/why-qld-beaches-will-lose-their-sand-nsw/3084034/#/0

Gold Coast at threat of severe erosion and property damage, research shows. Gold Coast Bulletin. http://www.goldcoastbulletin.com.au/lifestyle/beaches-and-fishing/gold-coast-at-threat-of-severe-erosion-and-property-damage-research-shows/news-story/46326698783e430830f4e668b0086191

Solving the Puzzle of Hurricane History

This article was posted on the NOAA website on 11 Feb 2016.

If you want to understand today, you have to search yesterday.”  ~ Pearl S. Buck

One of the lesser-known but important functions of the NHC [National Hurricane Centre, Miami, Florida] is to maintain a historical hurricane database that supports a wide variety of uses in the research community, private sector, and the general public.  This database, known as HURDAT (short for HURricane DATabase), documents the life cycle of each known tropical or subtropical cyclone.  In the Atlantic basin, this dataset extends back to 1851; in the eastern North Pacific, the records start in 1949.  The HURDAT includes 6-hourly estimates of position, intensity, cyclone type (i.e., whether the system was tropical, subtropical, or extratropical), and in recent years also includes estimates of cyclone size.  Currently, after each hurricane season ends, a post-analysis of the season’s cyclones is conducted by NHC, and the results are added to the database. The Atlantic dataset was created in the mid-1960s, originally in support of the space program to study the climatological impacts of tropical cyclones at Kennedy Space Center.  It became obvious a couple of decades ago, however, that the HURDAT needed to be revised because it was incomplete, contained significant errors, or did not reflect the latest scientific understanding regarding the interpretation of past data.  Charlie Neumann, a former NHC employee, documented many of these problems and obtained a grant to address them under a program eventually called the Atlantic Hurricane Database Re-analysis Project.  Chris Landsea, then employed by the NOAA Hurricane Research Division (HRD) and now currently the Science and Operations Officer at the NHC, has served as the lead scientist and program manager of the Re-analysis Project since the late 1990s.

In response to the re-analysis effort, NHC established the Best Track Change Committee (BTCC) in 1999 to review proposed changes to the HURDAT (whether originating from the Re-analysis Project or elsewhere) to ensure a scientifically sound tropical cyclone database.  The committee currently consists of six NOAA scientists, four of whom work for the NHC and two who do not (currently, one is from HRD and the other is from the Weather Prediction Center).

Over the past two decades, Landsea, researchers Andrew Hagen and Sandy Delgado, and some local meteorology students have systematically searched for and compiled any available data related to each known storm in past hurricane seasons.  This compilation also includes systems not in the HURDAT that could potentially be classified as tropical cyclones.  The data are carefully examined using standardized analysis techniques, and a best track is developed for each system, many of which would be different from the existing tracks in the original dataset.  Typically, a season’s worth of proposed revised or new tracks is submitted for review by the BTCC.  Fig. 1 provides an example set of data that helped the BTCC identify a previously unknown tropical storm in 1955.

 

Figure 1. Surface plot of data from 1200 UTC 26 Sep 1955, showing a previously unknown tropical storm.

The BTCC members review the suggested changes submitted by the Re-analysis Project, noting areas of agreement and proposed changes requiring additional data or clarification. The committee Chairman, Dr. Jack Beven, then assembles the comments into a formal reply from the BTCC to the Re-analysis Project. Occasionally, the committee’s analysis is presented along with any relevant documentation that would help Landsea and his group of re-analyzers account for the differing interpretation.   The vast majority of the suggested changes to HURDAT are accepted by the BTCC.  In cases where the proposed changes are not accepted, the BTCC and members of the Re-Analysis Project attempt to resolve any disagreements, with the BTCC having final say.

In the early days of the Re-analysis Project, the amount of data available for any given tropical cyclone or even a single season was quite small, and so were the number of suggested changes.  This allowed the re-analysis of HURDAT to progress relatively quickly.  However, since the project has reached the aircraft reconnaissance era (post 1944), the amount of data and the corresponding complexity of the analyses have rapidly increased, which has slowed the project’s progress during the last couple of years.

The BTCC’s approved changes have been significant. On average, the BTCC has approved the addition of one to two new storms per season.  One of the most highly visible changes was made 14 years ago, when the committee approved Hurricane Andrew’s upgrade from a category 4 to a category 5 hurricane.  This decision was made on the basis of (then) new research regarding the relationship between flight-level and surface winds from data gathered by reconnaissance aircraft using dropsondes.

Figure 2 show the revisions made to the best tracks of the 1936 hurricane season, and gives a flavor of the type, significance, and number of changes being made as part of the re-analysis.  More recent results from the BTCC include the re-analysis of the New England 1938 hurricane, which reaffirmed its major hurricane status in New England from a careful analysis of surface observations.  Hurricane Diane in 1955, which brought tremendous destruction to parts of the Mid-Atlantic states due to its flooding rains, was judged to be a tropical storm at landfall after re-analysis.   Also of note is the re-analysis of Hurricane Camille in 1969, one of three category 5 hurricanes to have struck the United States in the historical record.  The re-analysis confirmed that Camille was indeed a category 5 hurricane, but revealed fluctuations in its intensity prior to its landfall in Mississippi that were not previously documented.

The most recent activity of the BTCC was an examination of the landfall of the Great Manzanillo Hurricane of 1959.  It was originally designated as a category 5 hurricane landfall in HURDAT and was the strongest landfalling hurricane on record for the Pacific coast of Mexico. A re-analysis of ship and previously undiscovered land data, however, revealed that the landfall intensity was significantly lower (140 mph).  Thus, 2015’s Hurricane Patricia is now the strongest landfalling hurricane on record for the Pacific coast of Mexico, with an intensity of 150 mph.

Figure 2. Revisions made to the best tracks of the 1936 hurricane season

The BTCC is currently examining data from the late 1950s and hopes to have the 1956-1960 re-analysis released before next hurricane season.  This analysis will include fresh looks at Hurricane Audrey in 1957 and Hurricane Donna in 1960, both of which were classified as category 4 hurricane landfalls in the United States.   As the re-analysis progresses into the 1960s, the committee will be tackling the tricky issue of how to incorporate satellite images into the re-analysis, including satellite imagery’s irregular frequency and quality during that decade. The long-term plan is to extend the re-analysis until about the year 2000, when current operational practices for estimating tropical cyclone intensity became established using GPS dropsonde data and flight-level wind reduction techniques.

https://noaanhc.wordpress.com/2016/02/11/solving-the-jigsaw-puzzle-of-hurricane-history/

 

Stationarity of major flood frequencies and heights on the Ba River, Fiji, over a 122-year record

Paper by John McAneney, Robin van den Honert and Stephen Yeo published in International Journal of Climatology.

ABSTRACT: The economic impact of natural disasters on developing economies can be severe with the recovery diverting scarce funds that might otherwise be targeted at development projects and stimulating the need for international aid. In view of the likely sensitivity of low-lying Pacific Islands to anticipated changes in climate, a 122-year record of major flooding depths at the Rarawai Sugar Mill on the Ba River in the northwest of the Fijian Island of Viti Levu is analysed. Reconstructed largely from archived correspondence of the Colonial Sugar Refining Company, the time series comprises simple measurements of height above the Mill floor. It exhibits no statistically significant trends in either frequency or flood heights, once the latter have been adjusted for average relative sea-level rise. This is despite persistent warming of air temperatures as characterized in other studies. There is a strong dependence of frequency (but not magnitude) upon El Niño-Southern Oscillation (ENSO) phase, with many more floods in La Niña phases. The analysis of this long-term data series illustrates the difficulty of detecting a global climate change signal from hazard data, even given a consistent measurement methodology (cf HURDAT2 record of North Atlantic hurricanes) and warns of the strong dependence of any statistical significance upon choices of start and end dates of the analysis.

Click here to read entire paper.

Earthquake Scenario, Melbourne, Mw 5.5, 6.0 & 7.0

Report by Dr Valentina Koschatzky, Dr James O’Brien, Prof. Paul Somerville for Bushfire and Natural Hazards CRC. 

Despite its low seismic activity, Australia is more vulnerable to earthquakes than one would expect due to the concentration of population and the large stock of buildings which are structurally unable to withstand even moderate seismic shaking. This was demonstrated by the 1989 M5.6 Newcastle earthquake, one of the costliest natural disasters in Australia, despite its low magnitude. One question elicited by these circumstances is: what would happen if one of Australia’s main cities were hit by an earthquake similar to the Newcastle earthquake? An example of a near miss is the 1954 M5.6 Adelaide earthquake, whose epicentre, far from developed areas at the time, would lie in densely developed areas were it to occur today. Providing realistic estimates for natural disaster scenarios is essential for emergency managers. A systematic approach to developing such scenarios can reveal blind spots and vulnerabilities in planning. Following the Adelaide Scenario delivered in 2015 we now look into a series of realistic disaster earthquake scenarios for the city of Melbourne.

click here to read entire report

Australia’s unique approach to understanding natural disaster risks

Article by Kevin Roche published in Asia Pacific Fire,  January 5, 2017. 

Five of Australia’s six most costly natural hazard events have come from different perils: a tropical cyclone, an earthquake, a flood, bushfire and a convective storm. Over the last 20 years, a unique approach to understanding these risks has developed in Australia through a close relationship between the insurance and academic sectors. And by doing so Australia has been at the cutting edge in applying advances in technology and science to the benefit of the broader community. Here we explore a little of this history and explain how it has helped communities and emergency services better manage the risks they face.

Click here to read entire article.

Researchers are studying the effects on wave direction as the tropics spread south

Thomas Mortlock is interviewed for this article in Forge Magazine.

Macquarie University at forefront of marine science.

Macquarie University’s pioneering research in marine science is helping planning authorities and coastal communities to better understand the threat of storm-related beach erosion.

The university’s Marine Climate Risk Group is fusing paleoclimatology (the study of past climates) with cutting-edge coastal modelling techniques to understand how the predicted southward expansion of the tropics will affect storm activity, wave patterns and sand movement.

The Marine Climate Risk Group is led by Associate Professor Ian Goodwin, and its research is now part of Macquarie University’s Marine Research Centre (MQ Marine).  Established in July 2015, MQ Marine is driving multidisciplinary research on oceans and marine ecosystems, and is adding to Macquarie University’s outstanding global reputation in marine science.

Click here to read entire article.