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Much work has been done to build arrangements between volcanology and meteorology to handle the aviation risks from volcanic ash. This workshop will discuss how to approach collaborative arrangements for other volcanic hazards to the public, particularly where a multi-disciplinary approach is required. These hazards include tsunamis, ashfall, rainfall-induced dome collapses, lahars, pumice, glacial floods, and gas. They threaten a range of sectors including marine users, land transport users, agriculture, and residential communities. Approaching these hazards in an integrated fashion with the hydrometeorological community will help provide consistent and coherent warnings, create a focus on the capacity development required, and ultimately build a safer world consistent with the Sendai Framework and the recent UN call to provide universal coverage for early warning systems.The workshop featured a range of multi-disciplinary presentations on this theme, and discuss and draft a vision for future seamless multi-hazard warnings for volcanic eruptions and for secondary hazards.

Identifying the spatial extent of volcanic ash clouds in the atmosphere and forecasting their direction and speed of movement has important implications for the safety of the aviation industry, community preparedness and disaster response at ground level. Nine regional Volcanic Ash Advisory Centres were established worldwide to detect, track and forecast the movement of volcanic ash clouds and provide advice to en route aircraft and other aviation assets potentially exposed to the hazards of volcanic ash. In the absence of timely ground observations, an ability to promptly detect the presence and distribution of volcanic ash generated by an eruption and predict the spatial and temporal dispersion of the resulting volcanic cloud is critical. This process relies greatly on the heavily manual task of monitoring remotely sensed satellite imagery and estimating the eruption source parameters (e.g. mass loading and plume height) needed to run dispersion models. An approach for automating the quick and efficient processing of next generation satellite imagery (big data) as it is generated, for the presence of volcanic clouds, without any constraint on the meteorological conditions, (i.e. obscuration by meteorological cloud) would be an asset to efforts in this space. An automated statistics and physics-based algorithm, the Automated Probabilistic Eruption Surveillance algorithm is presented here for auto-detecting volcanic clouds in satellite imagery and distinguishing them from meteorological cloud in near real time. Coupled with a gravity current model of early cloud growth, which uses the area of the volcanic cloud as the basis for mass measurements, the mass flux of particles into the volcanic cloud is estimated as a function of time, thus quantitatively characterising the evolution of the eruption, and allowing for rapid estimation of source parameters used in volcanic ash transport and dispersion models.

Volcanic ash clouds often become multilayered and thin with distance from the vent. We explore one mechanism for the development of this layered structure. We review data on the characteristics of turbulence layering in the free atmosphere, as well as examples of observations of layered clouds both near-vent and distally. We then explore dispersion models that explicitly use the observed layered structure of atmospheric turbulence. The results suggest that the alternation of turbulent and quiescent atmospheric layers provides one mechanism for the development of multilayered ash clouds by modulating vertical particle motion. The largest particles, generally &gt, 100μm, are little affected by turbulence. For particles in which both settling and turbulent diffusion are important to vertical motion, mostly in the range of 10–100 μμm, the greater turbulence intensity and more rapid turbulent diffusion in some layers causes these particles to spend greater time in the more turbulent layers, leading to a layering of concentration. The results may have important implications for ash cloud forecasting and aviation safety.

More than 30 years after the first major aircraft encounters with volcanic ash over Indonesia in 1982, it remains challenging to inform aircraft in flight of the exact location of potentially dangerous ash clouds on their flight path, particularly shortly after the eruption has occurred. The difficulties include reliably forecasting and detecting the onset of significant explosive eruptions on a global basis, observing the dispersal of eruption clouds in real time, capturing their complex structure and constituents in atmospheric transport models, describing these observations and modelling results in a manner suitable for aviation users, delivering timely warning messages to the cockpit, flight planners and air traffic management systems, and the need for scientific development in order to undertake operational enhancements. The framework under which these issues are managed is the International Airways Volcano Watch (IAVW), administered by the International Civil Aviation Organization (ICAO). ICAO outlines in its standards and recommended practices (International Civil Aviation Organization 2014a, b) the basic volcanic monitoring and communication that is necessary at volcano observatories in Member States (countries). However, not all volcanoes are monitored and not all countries with volcanoes have mandated volcano observatories or equivalents. To add to the efforts of volcano observatories, a system of Meteorological Watch Offices, Air Traffic Management Area Control Centres, and nine specialist Volcanic Ash Advisory Centres (VAACs) are responsible for observing, analysing, forecasting and communicating the aviation hazard (airborne ash), using agreed techniques and messages in defined formats. Continuous improvement of the IAVW framework is overseen by expert groups representing the operators of the system, the user community, and the science community. The IAVW represents a unique marriage of two scientific disciplines, volcanology and meteorology, with the aviation user community. There have been many multifaceted volcanic eruptions in complex meteorological conditions during the history of the IAVW. Each new eruption brings new insights into how the warning system can be improved, and each reinforces the lessons that have gone before. The management of these events has improved greatly since the major ash encounters in the 1980s, but discontinuities in the warning and communications system still occur. A good example is a 2014 ash encounter over Indonesia following the eruption of Kelut where the warnings did not reach the aircraft crew. Other events present enormous management challenges—for example the 2010 Eyjafjallajokull eruption in Iceland was, overall, less hazardous than many less publicised eruptions, but numerous small to moderate explosions over several weeks produced widespread disruption and a large economic impact. At the time of writing, while there has been hundreds of millions of US dollars in damage to aircraft from encounters with ash, there have been no fatalities resulting from aviation incidents in, or proximal to volcanic ash cloud. This reflects, at least in part, the hard work done in putting together a global warning system—although to some extent it also reflects a measure of good statistical fortune. In order to minimise the risk of aircraft encounters with volcanic ash clouds, the global effort continues. The future priorities for the IAVW are strongly focused on enhancing communication before, and at the very onset of a volcanic ash-producing event (typically the more dangerous stage), together with improved downstream information and warning systems to help reduce the economic impact of eruptions on aviation.

The Australian Bureau of Meteorology monitors, researches, predicts and communicates Australia’s weather and climate. Australia’s mean temperature has risen by over 1°C since 1910, leading to an increase in the frequency of extreme heat events. Extreme heat can profoundly impact human health, infrastructure and the environment. Research conducted at the Bureau and elsewhere shows that climate change is impacting the intensity and frequency of extreme heat events. One way that the Bureau has responded to this challenge is by providing a forecast service specifically targeted at identifying heatwaves. The heatwave service identifies areas expected to be impacted by three or more consecutive days of unusually high maximum and minimum temperatures on a national map. The service has been developed with clear impact-based categories of heatwave severity. This heatwave service is now available operationally on the Bureau’s website during the heatwave season (nominally November to March) and is proving a valuable tool for engaging the community, including emergency services, with forecasts and warnings of extreme heat.

A critical factor in successfully monitoring and forecasting volcanic ash dispersion for aviation safety is the height reached by eruption clouds, which is affected by environmental factors, such as wind shear and atmospheric instability. Following earlier work using the Active Tracer High Resolution Atmospheric Model for strong Plinian eruptions, this study considered a range of eruption strengths in different atmospheres. The results suggest that relatively weak volcanic eruptions in the moist tropics can trigger deep convection that transports volcanic material to 15–20 km. For the same volcanic strength there can be ~9 km difference between eruption heights in moist tropical and dry subpolar environments (a larger height difference than previously suggested), which appears consistent with observations. These results suggest that eruption intensity should not be estimated from eruption height alone for tropospheric eruptions and also that the average height of volcanic eruptions may increase if the tropical atmospheric belt widens in a changing climate. Ash aggregation is promoted by hydrometeors (particularly liquid water), so the smaller modelled eruptions in moist atmospheres, which have a relatively small ash content for their height and water content, result in a relatively small proportion of fine ash in the dispersing cloud when compared to a dry atmosphere. This in turn makes the ash clouds much more difficult to detect using remote sensing than those in dry atmospheres. Overall, a weak eruption in the tropics is more likely to produce a plume above cruising levels for civil aviation, harder to detect and track, but with a lower concentration of fine ash than a mid-latitude or polar equivalent. There is currently no defined ‘acceptable’ concentration of ash for aircraft, but as these results suggest low-grade encounters in the tropics from undetected clouds are likely, it would be desirable to explore that issue.

The plume height represents a crucial piece of evidence about an eruption, feeding later assessment of its size, character, and potential impact, and feeding real-time warnings for aviation and ground-based populations. There have been many observed discrepancies between different observations of maximum plume height for the same eruption. A comparison of maximum daily height estimates of volcanic clouds over Indonesia and Papua New Guinea during 1982–2005 shows marked differences between ground and satellite estimates, and a general tendency towards lower height estimates from the ground. Without improvements in the quality of these estimates, reconciled among all available methods, warning systems will be less effective than they should be and the world's record of global volcanism will remain hard to quantify. Examination of particular cases suggests many possible reasons for the discrepancies. Consideration of the satellite and radar cloud observations for the 1991 Pinatubo eruptions shows that marked differences can exist even with apparently good observations. The problem can be understood largely as a sampling issue, as the most widely reported parameter, the maximum cloud height, is highly sensitive to the frequency of observation. Satellite and radar cloud heights also show a pronounced clumping near the height of the tropopause and relative lack of eruptions reaching only the mid-troposphere, reinforcing the importance of the tropopause in determining the eruption height in convectively unstable environments. To reduce the discrepancies between ground and satellite estimates, a number of formal collaboration measures between vulcanological, meteorological and aviation agencies are suggested.

During volcanic eruptions, volcanic ash transport and dispersion models (VATDs) are used to forecast the location and movement of ash clouds over hours to days in order to define hazards to aircraft and to communities downwind. Those models use input parameters, called “eruption source parameters”, such as plume height H, mass eruption rate Ṁ, duration D, and the mass fraction m63 of erupted debris finer than about 4ϕ or 63 μm, which can remain in the cloud for many hours or days. Observational constraints on the value of such parameters are frequently unavailable in the first minutes or hours after an eruption is detected. Moreover, observed plume height may change during an eruption, requiring rapid assignment of new parameters. This paper reports on a group effort to improve the accuracy of source parameters used by VATDs in the early hours of an eruption. We do so by first compiling a list of eruptions for which these parameters are well constrained, and then using these data to review and update previously studied parameter relationships. We find that the existing scatter in plots of H versus Ṁ yields an uncertainty within the 50% confidence interval of plus or minus a factor of four in eruption rate for a given plume height. This scatter is not clearly attributable to biases in measurement techniques or to well-recognized processes such as elutriation from pyroclastic flows. Sparse data on total grain-size distribution suggest that the mass fraction of fine debris m63 could vary by nearly two orders of magnitude between small basaltic eruptions (∼ 0.01) and large silicic ones (> 0.5). We classify eleven eruption types; four types each for different sizes of silicic and mafic eruptions; submarine eruptions; “brief” or Vulcanian eruptions; and eruptions that generate co-ignimbrite or co-pyroclastic flow plumes. For each eruption type we assign source parameters. We then assign a characteristic eruption type to each of the world's ∼ 1500 Holocene volcanoes. These eruption types and associated parameters can be used for ash-cloud modeling in the event of an eruption, when no observational constraints on these parameters are available.

The hazards wrought on society by volcanoes have been studied, discussed and reported extensively. Danger from volcanoes can occur on the land, on the sea and as this Special Issue highlights, in the air as well. The great eruptions of Vesuvius in AD 79 (Etienne 1992), Pelein 1902 (Fisher and Heiken 1982) and Krakatau in 1883 (Self and Rampino 1981) caused widespread devastation and killed thousands of people. During the eruption of Vesuvius, the town of Pompeii was destroyed by pyroclastic flows and the mummified remains of some of the inhabitants bear testament to the dangers and rapidity of volcanic hazards. It is reported that 36,000 people lost their lives in the aftermath of the climactic eruption of Krakatau; many of these unfortunate people were killed by the tsunamis that followed the collapse of several km 3 of rock into the sea. Shipping was particularly vulnerable during the eruptions of Krakatau and continued to suffer for more than 1 year following the major eruption. Atmospheric hazards from eruptions have also been studied, and a good example of the consequences of sustained eruptive activity on society is the 1763 Laki fissure eruption. Over a period of several months, the Laki eruption generated sufficient quantities of hazardous gases (SO2, HCl and HF) to kill more than 50% of the Icelandic livestock and severely affected the health and well-being of the population (Thordarson et al. 1996). Impacts on human health from several different volcanic erup- tions are described by Baxter (2005). Societal vulnerability and risk from volcanic erup- tions on land, on the sea and in the atmosphere are serious (Blong 1984)—considerable resources are expended to guard against and respond to these hazards. In the modern era, since the introduction of transcontinental air travel, a new threat from volcanoes has emerged: volcanic ash in the upper troposphere, where jet aircraft fly, can cause jet engine failure (loss of power), damage to turbine blades and pitot static tubes, with the possibility of the loss of the aircraft and lives (Casadevall et al. 1996). The increase in passenger air traffic (growing at an average of 5% per year, globally) (ESCAP 2005) coupled with the

Two significant eruptions occurred at Miyakejima volcano on 18 and 28 August 2000 and were detected by multiple satellite sensors. For both eruptions, the cloud can be observed with high confidence for 2 days. Using Total Ozone Mapping Spectrometer (TOMS), MODerate resolution Infrared Spectroradiometer (MODIS), Advanced Very High Resolution Radiometer (AVHRR) and High Resolution Infra Red Radiation Sounder (HIRS) imagery, constraints are placed on the masses and distributions of ash and SO2 released by the eruptions. The 18 August eruption at 08:02 UTC (17:02 JST) emitted an ash cloud of at least 511 kt and a sulfur dioxide (SO2) cloud of 43 kt to a height of approximately 16 km asl, which then drifted south. The 28 August eruption (19:35 UTC, 04:35 JST) was smaller, with a cloud containing a minimum of 0.2 kt of ash and 21 kt of SO2 at a height of 5 km to the northeast of the volcano associated with a low-temperature pyroclastic surge. The 18 August eruption probably represents a vent-clearing phase, given the magmatic nature of the erupted products, the significant amounts of ash produced and the prodigious gas emission rates in the following passive degassing phase, while the 28 August eruption was mostly phreatic, with a cold-surge component not easily detectable by any of the sensors used. Comparisons of detection ability of the sensors were also made. The results suggest that the ultraviolet sensor TOMS more regularly detected SO2, as it is less susceptible to interference of water vapour and other species, as is observed with the infrared sensor MODIS. TOMS was able to detect SO2 for a total of 5 days for both eruptions combined, whereas HIRS detected SO2 for 3 days of the first eruption and MODIS detected the gas cloud for 1 day of each eruption. AVHRR was the most consistent when detecting ash and was able to see ash clouds not detected by the other sensors because of its more serendipitous overpass timing.

Devastating eruptions occurred at Manam, Papua New Guinea, from October 2004 to January 2005. An unprecedented set of pilot reports were obtained; ground-, air-, and satellite-observed eruption heights differed greatly. Satellite postanalysis and satellite CO2 slicing techniques give consistent heights. The climactic eruption, on 27 January 2005, reached 21–24 km MSL; four other eruptions reached 16.5–19 km. Tracking of these ice-rich clouds was done by monitoring strong “ice” signatures on 11–12-μm infrared imagery (for two eruptions), by using reflectance-based techniques (during the daytime), and by using SO2 detection (available only in postanalysis). A remote lightning detection network could not detect the eruption clouds, despite detecting lightning from thunderstorms in the area. The eruptions appeared to enhance the nocturnal cycle of (ash contaminated) deep convection above the island, consistent with previous work on diurnal volcanic cumulonimbus at Mount Pinatubo. The communications and infrastructure challenges of the region strongly affected the performance of the volcanic ash warning system, but can be partially addressed with the development of appropriate strategies. A strategy of gradual advisory cessation at the end of each event generally worked well but failed where numerical modeling and satellite observation were insufficient. An aircraft apparently encountered SO2 from the cloud over Dili, Timor-Leste; no engine damage was reported, but no close inspection was made at the time. It is suggested that maintenance guidelines be developed to help clarify the risk of volcanic ash damage from encounters with clouds where only SO2 odor is observed.

Monitoring of Asian dust at two stations in Changchun, Jilin Province in northeast China, and Kagoshima, southwest Japan, is discussed. In Changchun, interval records were made with digital and video cameras from 18 March 2003. In Kagoshima, a web camera system to monitor volcanic clouds has been working since December 2000, which also provides data for studies of dust. A heavy dust episode on 11 November 2002, affecting both stations, was detected using 11 and 12 μm channels of NOAA/AVHRR. We observed dust in Changchun on 26 March, 7, 14–16 April, 1–2, 8, 10, 19 May, 8, 23 June, and 12 July in 2003. The observed images corresponded well to NOAA/AVHRR imagery and with 8.6, 11 and 12 μm Terra/MODIS results, although conditions were too cloudy for satellite verification in some cases.

The advection and dispersion of Asian dust events from China to the Pacific Ocean around Japan during 2000–2002 were investigated using the meteorological satellite data of NOAA/AVHRR and GMS-5/VISSR. Aerosol vapour index images, taking the brightness temperature difference between 11 and 12 μm, are very effective for monitoring the Asian dust phenomenon in the East Asia region, with their capacity for detection during the day or night. We discuss the dust events, focusing on the advection patterns shown in satellite images, which are classified into three types as ‘dry slot’, ‘high-pressure wedge’ and ‘travelling high’, based on synoptic patterns. The results are compared with suspended particulate matter concentrations measured at Japanese surface stations and with ground-based observations of Sakurajima volcano by a web camera system at Kagoshima in Kyushu, Japan. We found that the passage of cold fronts caused a rapid increase of suspended particulate matter (SPM) concentrations, which exceeded 100 μg m −3 , and that deep low-pressure complexes strengthened the dust phenomenon. The ‘high-pressure wedge’ type is seen much more clearly in satellite images than the ‘travelling high’ type, but SPM concentrations and visibility were similar in both owing to the differences in the vertical distribution of the dust and in viewing conditions.

We examined recent volcanic cloud events in the Western Pacific and Indonesian area, to validate the performance of remote sensing techniques used to support the International Airways Volcano Watch (IAVW). Five events were considered, during which eruptions from eight volcanoes injected ash into the upper troposphere or lower stratosphere. For one of the eruptions, at Miyakejima, Japan, at least five aircraft encountered volcanic ash clouds, and the cost to three operators alone exceeded US $12,000,000 in aircraft repairs, diversions, and lost operating time. We performed ‘reverse’ absorption and ‘pattern analysis’ using GMS-5/VISSR, MODIS and AVHRR data, and we examined TOMS SO2 and Aerosol Index data, surface-based observations, pilot reports, and dispersion model output. Our results verify that the introduction of ‘reverse’ absorption using the geostationary GMS-5 platform significantly enhanced our capacity to monitor volcanic ash clouds in the region. In one case, we tracked an eruption cloud for approximately 80 h. The primary impediment to remote monitoring is the presence of overlying cloud, or substantial amounts of ice within the volcanic clouds. TOMS data showed success in identifying volcanic clouds during these conditions, but was limited by the infrequency of observations. More effective future operation of the IAVW relies on developing complementary methods of volcanic cloud remote sensing, and greatly increasing the amount and quality of available surface and air observations, including observations of precursor activity. An understanding of the likely future limitations of remote sensing techniques will aid in the refining of IAVW procedures.

The risks to safe and efficient air travel from volcanic-ash hazards are well documented and widely recognized. Under the aegis of the International Civil Aviation Organization, globally coordinated mitigation procedures are in place to report explosive eruptions, detect airborne ash clouds and forecast their expected movement, and issue specialized messages to warn aircraft away from hazardous airspace. This mitigation framework is based on the integration of scientific and technical capabilities worldwide in volcanology, meteorology, and atmospheric physics and chemistry. The 2010 eruption of Eyjafjallajokull volcano in Iceland, which led to a nearly week-long shutdown of air travel into and out of Europe, has prompted the aviation industry, regulators, and scientists to work more closely together to improve how hazardous airspace is defined and communicated. Volcanic ash will continue to threaten aviation and scientific research will continue to influence the risk-mitigation framework.

The recent paper by Simpson et al. [Remote Sens. Environ. 72 (2000) 191.] on failures to detect volcanic ash using the ‘reverse absorption’ technique provides a timely reminder of the danger that volcanic ash presents to aviation and the urgent need for some form of effective remote detection. The paper unfortunately suffers from a fundamental flaw in its methodology and numerous errors of fact and interpretation. For the moment, the ‘reverse’ absorption technique provides the best means for discriminating volcanic ash clouds from meteorological clouds. The purpose of our comment is not to defend any particular algorithm; rather, we point out some problems with Simpson et al.'s analysis and re-state the conditions under which the ‘reverse’ absorption algorithm is likely to succeed.

Although significant progress has been made in recent years, estimating volcanic ash concentration for the full extent of the airspace affected by volcanic ash remains a challenge. No single satellite, airborne or ground observing system currently exists which can sufficiently inform dispersion models to provide the degree of accuracy required to use them with a high degree of confidence for routing aircraft in and near volcanic ash. Toward this end, the detection and characterization of volcanic ash in the atmosphere may be substantially improved by integrating a wider array of observing systems and advancements in trajectory and dispersion modeling to help solve this problem. The qualitative aspect of this effort has advanced significantly in the past decade due to the increase of highly complementary observational and model data currently available. Satellite observations, especially when coupled with trajectory and dispersion models can provide a very accurate picture of the 3-dimensional location of ash clouds. The accurate estimate of the mass loading at various locations throughout the entire plume, however improving, remains elusive. This paper examines the capabilities of various satellite observation systems and postulates that model-based volcanic ash concentration maps and forecasts might be significantly improved if the various extant satellite capabilities are used together with independent, accurate mass loading data from other observing systems available to calibrate (tune) ash concentration retrievals from the satellite systems.

Major disruptions of the aviation system from recent volcanic eruptions have intensified discussions about and increased the international consensus toward improving volcanic ash warnings. Central to making progress is to better discern low volcanic ash loadings and to describe the ash cloud structure more accurately in three-dimensional space and time. Here, dispersed volcanic ash observed by the Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) space-based lidar near 20 000–40 000 ft [~(6–13) km] over Australia and New Zealand during June 2011 is studied. This ash event took place 3 weeks after the Puyehue-Cordon Caulle eruption, which disrupted air traffic in much of the Southern Hemisphere. The volcanic ash layers are shown to exhibit color ratios (1064/532 nm) near 0.5, significantly lower than unity, as is observed with ice. Those optical properties are used to develop an ash detection algorithm. A “trajectory mapping” technique is then demonstrated wherein ash cloud observations are ingested into a Lagrangian model and used to construct ash dispersion maps and cross sections. Comparisons of the model results with independent observations suggest that the model successfully reproduces the 3D structure of volcanic ash clouds. This technique has a potential operational application in providing important additional information to worldwide volcanic ash advisory centers.

The ASHE Ecuador (2004-2012) collaboration between Ecuador, Canada, and the United States demonstrated the capability to use real-time infrasound to provide low-latency volcanic eruption notifications to the Volcano Ash Advisory Center (VAAC) in Washington DC. The Atmospheric dynamics Research Infrastructure in Europe (ARISE, 2012-2018) supported by the European Commission fosters integrating innovative methods for remote detection and characterization of distant eruptive sources through collaborations with the VAAC Toulouse and the Comprehensive Nuclear-Test-Ban-Treaty Organization (CTBTO). The ASHE Asia project proposes an international collaboration between the Earth Observatory of Singapore, the VAAC Darwin, National Data Centers in Japan, Korea, and Palau, and will receive the support of ARISE, to provide improved early notification of potentially hazardous eruptions in Asia and the Western Pacific using a combination of established technologies and next-generation mobile sensing systems. The increas...

[1] Headline-making firestorms in southeast Australia in 2003, responsible for at least 500 destroyed buildings and four lost lives, culminated with pyro-cumulonimbus (pyroCb) “eruptions” that ravaged Canberra on 18 January. Here we reveal that in their 3-hour lifetime, the Canberra pyroCbs also produced a stratospheric smoke injection that perturbed the hemispheric background analogous to the theorized “nuclear winter.” We use an unprecedented array of data to analyze the Canberra pyroCbs' distinctive stratospheric impact, microphysics, energetics, and surface manifestations—including suppressed precipitation, an F2 tornado, and black hail.

[1] Several observers reported interesting convective phenomena in the months and years following the 15 June 1991 climactic eruption of Mount Pinatubo, Philippines. The observed phenomena included deep convection resulting from (1) lower level eruptions, (2) secondary phreatic explosions, and (3) enhanced surface heating. We have compared radar records and satellite imagery to obtain a more coherent understanding of these “volcanic-cumulonimbi” from 17 June to 30 September 1991 and to identify observational challenges for future events. Geostationary satellite imagery analysis for the period shows that the dominant localized effect on convection following the eruption was to bring the afternoon/evening peak in the diurnal convective cycle over the mountain forward by 2–3 hours. We examined four cases in detail and identified a number of possible interactions between the volcano and the meteorological environment. For three of these cases, the volcanic emissions apparently mixed with cumulonimbi developing around the volcano; on 21 June 1991, microphysical analyses clearly show a strong reduction in cloud top effective particle radius caused by the additional aerosols in the cloud, while on the two other occasions, there was a slight or barely detectible reduction. In the fourth case, for a cumulonimbus developing above a major secondary phreatic explosion, no unusually small cloud top effective radii were found, perhaps because the ash injected into the cloud was dominated by giant cloud condensation nuclei. These cases verify that volcanic emissions can be released through the depth of the troposphere and lower stratosphere from relatively small eruptions. Future major tropical eruptions and their aftermaths should be studied using intensive ground- and satellite-based observations to explore these phenomena further.

Silicate dusts, volcanic ash clouds and Asian dust, are well detected by the 'split-window' method, which calculates the brightness temperature difference of the 11 and 12 μm bands. Volcanic plumes containing less ash are enhanced by the difference of the visible and near infrared bands of NOAA/AVHRR data. In order to supplement these difference images and improve the discrimination of volcanic ash- rich/poor plumes and of Asian dust from various meteorological clouds, various combinations of AVHRR imagery were investigated. It was found that the differences of the 3.7 and 11 μm bands and of the 1.6 μm and visible bands are useful to distinguish between thick clouds and dusts. Colour composite images containing the 1.6 or 3.7 μm bands are useful for distinguishing the objects from any meteorological clouds, because these bands are sensitive to droplet size.

The eruption of Miyakejima volcano started on 8 July 2000. As of September 2002, SO2 emissions measured by COSPEC average 11000 t/day. As the volcanic gas tends to behave together with the plume, we may infer the advection of the gas from the observation of the plume. Ground observations have been performed from Mikurajima using CCD cameras since September 2000. These pictures clarify the vertical structure of volcanic clouds. The horizontal dispersion of the clouds is well shown in NOAA/AVHRR, Terra/MODIS and other satellite images. Ash-rich clouds at the first stage are well detected by the difference image of NOAA/AVHRR 5 and 4, while vapor-rich clouds are insensitive to the difference. Instead, the latter are detected by the difference of AVHRR 1 and 2, and discriminated well from meteorological clouds in many cases. MODIS data is sensitive to the ash and sulfates of Miyakejima plumes in the 8.6 mm channel, and can detect the fine structure of the plumes with its high-resolution visible channels. Miyakejima plumes contain large quantities of volcanic gases, and their daily monitoring using satellites and ground observations in conjunction with upper wind data helps to understand high concentration events of sulfur dioxide downstream from the volcano.

When forecasting the weather, simple outcome statements do not always adequately describe what could eventuate for a particular location. Importantly, some weather situations are finely balanced, and cannot be forecast five days in advance; sometimes forecasting 24 hours ahead is difficult, particularly if tropical cyclones are present. To address these weather forecasting complexities, the Bureau of Meteorology is moving towards providing more probability based guidance, such as more information on potential rainfall ranges, wind speed probabilities, wave height probabilities, tropical cyclone formation risk and potential tropical cyclone tracks. For response planning purposes these changes will bring their own challenges. For example, previous chances of a tropical cyclone impact have been described with yes or no forecasts. In the future these risks could be described in percentages. Responding to a 5% risk suggests that 19 out of 20 responses could be perceived to be unnecessary, while on the other hand not responding to a 5% risk could be assessed as dangerous. Developing these new information types is only part of the process. To achieve better practice, it will also be critical to create presentation strategies that express the content in a usable manner, work with clients so they gain maximum benefit from the guidance, and enable clients to develop response plans that are aligned with the forecasts. The Bureau of Meteorology is seeking to work in a closer partnership with the resource sector on this to help maximise operational efficiencies, while ensuring a safe working environment.

Erratum to ‘A multidisciplinary effort to assign realistic source parameters to models of volcanic ash-cloud transport and dispersion during eruptions’ by Mastin et al. [J. Volcanol. Geotherm. Res. 188(2009)1–21] L.G. Mastin ⁎, M. Guffanti , R. Servranckx , P. Webley , S. Barsotti , K. Dean , A. Durant , J.W. Ewert , A. Neri , W.I. Rose , D. Schneider , L. Siebert , B. Stunder , G. Swanson , A. Tupper , A. Volentik , C.F. Waythomas h