Issues Magazine

Satellites, Climate and Extreme Events

By Alexander Held

Data from satellites is essential to Australia’s monitoring, forecasting and long-term planning for both weather and climate.

Australia is one of the top users of satellite data worldwide. Even though Australians don’t own or operate any “Earth-observing” or “global positioning or navigation” satellites, this data has been widely embraced ever since the first such satellites were launched in the 1970s. The total area we regularly map and monitor from space has been estimated as close to one-eighth of the Earth’s surface.

Australia’s use of satellite imagery has been largely driven by our need to monitor both our weather and our vast and often uninhabited territory, which includes 36,000 km of coastline, the wider marine exclusive economic zone and our Antarctic jurisdiction. Google Earth, which is based on high resolution satellite data, is a popular way to view locations or to get driving directions via a personal GPS, which also uses satellite data.

Over the next five years more than 100 new Earth-observation satellites will be launched by several countries, some of which will replace ageing or faulty ones or enhance those currently in space. These will have on-board more than 200 new and better quality instruments to map and measure various variables of the Earth.

Vital to the optimal use of these new satellite measurements is a healthy national research and development system that continues to develop new information from this data and further enhances current government programs with new information. Access to these vast amounts of imagery data, used for national mapping programs by our government, is often for free and is made possible only because of well-cultivated international partnerships with those governments that operate such satellites and that have collectively invested hundreds of billions of taxpayer-funded dollars in these systems.

Many small North American and European companies are now joining the space sector and launching their own Earth-observing satellites. The latest endeavours are by new start-ups such as PlanetLabs, SkyBox and UrteCast, which are building very small microsatellites and launching several at the same time. The objective is that they will form a small “constellation” or “swarm”, circling the Earth at a distance of about 600 km, and with relatively simple cameras will collect imagery of the Earth at a spatial resolution close to 1 metre on a very frequent basis for sale to non-government organisations, community organisations, conservation groups and the public.

In Australia, satellite data is used for many purposes across government and the private sector. Close to 100 state and federal programs worth hundreds of millions dollars rely on a steady supply of satellite imagery to fulfil their objectives, as well as research by agencies such as CSIRO and universities to further improve the quality of satellite data.

Satellite-based atmospheric measurements and land and marine imagery are considered to be the world’s most comprehensive environmental and weather monitoring data sources. In the area of weather forecasting alone, it is anticipated that we will be ultimately using some 20 different satellite data streams in near real-time as routine input to Australia’s new generation weather forecasting models, such as the Australian Community Climate and Earth System Simulator.

Data from other satellites is used for tracking cyclones, detecting and tracking bushfires, measuring sea levels and currents, mapping the extent of floods and for general geological mapping and environmental monitoring. On a day-to-day basis, terabytes of raw data is downlinked many times each day from the various orbiting satellites to receiving stations operated by the Bureau of Meteorology and Geoscience Australia, as well as by state agencies, the CSIRO and some universities.

Satellite data has nearly doubled the skill and the lead time for advanced and accurate weather forecasts, and the prediction of where cyclones will land. News and emergency warnings on the television now show maps issued by the Bureau of Meteorology that show the predicted trajectory of the cyclones in coming days. Excellent examples of these kinds of images can be found at http://www.bom.gov.au/australia/satellite and http://www.bom.gov.au/cyclone.

The production of these maps uses not only data on cloud formation, temperature and movement, as measured from geostationary satellites some 36,000 km away, but also measurements from other polar-orbiting satellites 700 km away that can accurately measure cloud heights, wind speeds, wind direction and rainfall. The resulting cyclone-track maps and estimated rainfall rates help state-based emergency agencies and governments provide much better advanced warnings and evacuation orders ahead of time, and thus minimise personal injury and reduce damage to infrastructure and valuable assets.

Wind-based damage to cities, infrastructure and crops can all be mapped from space with specialised imaging systems. During cyclones or severe storm events, flooding often occurs inland in especially vulnerable and low-lying areas close to river floodplains or large river systems. Here, state and federal emergency management agencies use satellite imagery to map the extent of the flooding and even the movement of flood waters in some of our larger river basins, all which helps them better plan rescue missions or longer-term reconstruction activities in affected areas.

In 2014 a new satellite mission called the Global Precipitation Mission will be launched by NASA and Japan’s space agency. This will provide even more accurate estimates of rainfall intensity for use in improved flood forecasting. CSIRO, the Bureau of Meteorology and Geoscience Australia aim to work with the US and Japan to secure access to this and other relevant satellites to further improve severe weather and flood forecasts into the future.

Satellite data is also used to detect and track bushfires across the continent. Bushfires are now mapped from space on a day-to-day basis; in particular, we detect the so-called active fire “hotspots” using dedicated satellites with thermal cameras on board. Such data is used for both tactical fire management in peri-urban zones and in remote areas across Australia.

Normally fire suppression and emergency management are the responsibility of individual states unless they become “mega-fires” covering very large regions, or when local agencies are not able to fully cover all fire fronts. Remote sensing data is therefore used both on a tactical, near real-time basis, and to build wider “situational awareness” of the different fires around the country so that state and federal agencies can plan their daily firefighting operations.

Remote sensing data helps protect high-value conservation areas from fire impacts. With an increase in arson during the dry season, fire frequency has increased to such an extent in some parts of Australia that ecosystems and certain flora and fauna species can be severely affected in their recovery to pre-fire conditions. Conservation groups are developing large-scale fire-suppression programs and enclosures, and are using historical and more recent satellite data to see if the impacts of these new fire-suppression measures have a positive effect in terms of land-cover dynamics and recovery after fire.

In 2003 CSIRO, together with the Department of Defence and Geoscience Australia, developed a bushfire-tracking system and dedicated online data portal called Sentinel Hotspots. The system uses the moderate resolution imaging spectrometer sensor on-board NASA’s Aqua and Terra satellites, thus achieving full continental coverages up to four times every 24 hours at a spatial resolution of about 1 km. Once downlinked into a satellite station operated by Geoscience Australia in Alice Springs, the system analyses the imagery automatically and within about 40 minutes places the hotspot location on the Sentinel online portal. At present, the Sentinel system is run by Geoscience Australia (http://sentinel.ga.gov.au) and continues to be used on a 24/7 basis by federal and state fire management agencies, natural resource managers, ecologists and the general public as fire conditions develop across the country. Other state-based or regional systems, such as FireWatch in Western Australia and the Northern Australia Fire Information system in the Northern Territory use similar approaches.

This Australian concept has also been adopted internationally. In 2006 the Asia- Pacific Regional Space Agencies Forum established the Sentinel Asia disaster-monitoring system, which applies very similar approaches for bushfire mapping but also covers several other types of disasters of importance for that region.

This part of the world has been disproportionately affected by a number of large-scale natural disasters over recent decades, particularly considering its high population levels (nearly four billion). According to official statistics in 2011, disasters occurring in Asia constitute 39% of the worldwide total. The region has sustained 53% of global fatalities, and is home to 88% of the total people affected by such disasters.

The Sentinel Asia partnership includes over 15 regional member governments and relevant agencies, supplying and using space-based information to help countries in the Asia-Pacific region monitor the progression of impending disasters and assess the impacts of floods, rainfall, landslides, earthquakes and other natural disasters.

The original implementation of Sentinel Asia is largely supported by the Japan Aerospace Exploration Agency and CSIRO, and was established to provide satellite information on disasters and promote much better cooperation among the different countries’ disaster management communities. These include the Asian Disaster Reduction Center and its member countries, as well as international organisations such as the United Nations Economic and Social Commission for Asia and the Pacific, the United Nations Office for Outer Space Affairs, the Association of South-East Asian Nations and the Asian Institute of Technology in Bangkok. Vital imagery and data was recently collected and freely provided by Sentinel Asia in support of emergency agencies in the Philippines following the Haiyan typhoon disaster late last year.

To support this cooperation and the implementation of the Sentinel Asia project, the membership has been open to all regional space agencies, disaster management organisations and regional/international organisations that are prepared to contribute their experiences and technical capabilities, and that wish to participate in technical aspects of disaster information-sharing activities.

Returning to Australia, the AusCover remote sensing data facility (www.auscover.org.au) of the Terrestrial Ecosystem Research Network (www.tern.org.au) of Australia, which I currently lead, has been providing free and open access to satellite-derived information since 2009, at regional and continental scales, mostly for use in fire ecology studies and assessment of fire impacts on protected areas, among other uses.

A key satellite-derived data product called the fire-severity index, developed and produced for AusCover by Dr Stefan Maier at Charles Darwin University in Darwin, allows local land managers and ecologists to monitor the effect of often unplanned fires and to strategically implement controlled burns during less damaging times of year. Similarly the grass curing index produced by another partner, the Bureau of Meteorology, provides a way to evaluate the dynamics of grass drying and fire-risk as dry seasons and summers progress across the continent.

Such derived datasets provide emergency managers, ecosystem researchers and conservation managers with greater information about the effects of fires on ecological communities, and improve estimates of carbon emissions resulting from fires in different types of ecosystems. These space-derived imagery and datasets are also used to regularly map how much area has been burned each year, which contributes to calculations made by the climate-science community and the government of Australia’s annual greenhouse gas emissions due to fire.