Journal articles on the topic 'Thunderstorms Australia Observations'

The impact of thunderstorms on the wildfire situation in Australia in 2017–2020 was investigated using data from the ISS LIS and MODIS space-based observations. To determine lightning-caused wildfires, a Geographic Information System (GIS) method was carried out, which consisted of a combined investigation of the spatial and temporal distributions of strikes and ignition hotspots. The seasonal variability of thunderstorms and wildfire activity was analyzed. It was established that the maximum seasonal distribution of thunderstorm activity does not coincide with wildfire activity. The interannual changes in strikes were recorded, but this was not revealed for the major vegetation types. Of 120,829 flashes, recorded by the ISS LIS sensor, only 23 flashes could be characterized as lightning-caused wildfire events, i.e., the frequency of lightning ignition was equal to 0.00023 fires/stroke. The lightning ignitions usually took place along the boundary of a thunderstorm, in semiarid areas covered by open scrublands. During the dry Australian period (April–September), very few lightning events were detected by the ISS LIS sensor, while fire activity was quite high. Additionally, it was concluded that the impact of thunderstorms on the fire situation is too small to explain the numerous wildfires during the wet period.

On 16 December 2015 a severe thunderstorm and associated tornado affected Sydney causing widespread damage and insured losses of $206 million. Severe impacts occurred in Kurnell, requiring repairs to Sydney's desalination plant which supplies up to 15% of Sydney water during drought, with repairs only completed at the end of 2018. Climatologically, this storm was unusual as it occurred during the morning and had developed over the ocean, rather than developing inland during the afternoon as is the case for many severe storms impacting the Sydney region. Simulations of the Kurnell storm were conducted using the Weather Research and Forecasting (WRF) model on a double nested domain using the Morrison microphysics scheme and the NSSL 2-moment 4-ice microphysics scheme. Both simulations produced severe storms that followed paths similar to the observed storm. However, the storm produced under the Morrison scheme did not have the same morphology as the observed storm. Meanwhile, the storm simulated with the NSSL scheme displayed cyclical low- and mid-level mesocyclone development, which was observed in the Kurnell storm, highlighting that the atmosphere supported the development of severe rotating thunderstorms with the potential for tornadogenesis. The NSSL storm also produced severe hail and surface winds, similar to observations. The ability of WRF to simulate general convective characteristics and a storm similar to that observed displays the applicability of this model to study the causes of severe high-impact Australian thunderstorms. References J. T. Allen and E. R. Allen. A review of severe thunderstorms in Australia. Atmos. Res., 178:347–366, 2016. doi:10.1016/j.atmosres.2016.03.011. Bureau of Meteorology. Severe Storms Archive, 2020. URL http://www.bom.gov.au/australia/stormarchive/. D. T. Dawson II, M. Xue, J. A. Milbrandt, and M. K. Yau. Comparison of evaporation and cold pool development between single-moment and multimoment bulk microphysics schemes in idealized simulations of tornadic thunderstorms. Month. Wea. Rev., 138:1152–1171, 2010. doi:10.1175/2009MWR2956.1. H. Hersbach, B. Bell, P. Berrisford, S. Hirahara, A. Horanyi, J. Munoz-Sabater, J. Nicolas, C. Peubey, R. Radu, D. Schepers, et al. The ERA5 global reanalysis. Quart. J. Roy. Meteor. Soc., 146:1999–2049, 2020. doi:10.1002/qj.3803. Insurance Council of Australia. Victorian bushfire losses push summer catastrophe bill past $550m, 2016. E. R. Mansell, C. L. Ziegler, and E. C. Bruning. Simulated electrification of a small thunderstorm with two-moment bulk microphysics. J. Atmos. Sci., 67:171–194, 2010. doi:10.1175/2009JAS2965.1. R. C. Miller. Notes on analysis and severe-storm forecasting procedures of the Air Force Global Weather Central, volume 200. Air Weather Service, 1972. URL https://apps.dtic.mil/sti/citations/AD0744042. H. Morrison, J. A. Curry, and V. I. Khvorostyanov. A new double-moment microphysics parameterization for application in cloud and climate models. Part I: Description. J. Atmos. Sci., 62:1665–1677, 2005. doi:10.1175/JAS3446.1. H. Morrison, G. Thompson, and V. Tatarskii. Impact of cloud microphysics on the development of trailing stratiform precipitation in a simulated squall line: Comparison of one- and two-moment schemes. Month. Wea. Rev., 137:991–1007, 2009. doi:10.1175/2008MWR2556.1. J. G. Powers, J. B. Klemp, W. C. Skamarock, C. A. Davis, J. Dudhia, D. O. Gill, J. L. Coen, D. J. Gochis, R. Ahmadov, S. E. Peckham, et al. The Weather Research and Forecasting Model: Overview, system efforts, and future directions. Bull. Am. Meteor. Soc., 98:1717–1737, 2017. doi:10.1175/BAMS-D-15-00308.1. H. Richter, A. Protat, J. Taylor, and J. Soderholm. Doppler radar and storm environment observations of a maritime tornadic supercell in Sydney, Australia. In Preprints, 28th Conf. on Severe Local Storms, Portland OR, Amer. Meteor. Soc. P, 2016. W. C. Skamarock, J. B. Klemp, J. Dudhia, D. O. Gill, Z. Liu, J. Berner, W. Wang, J. G. Powers, M. G. Duda, D. Barker, and X.-Y. Huang. A description of the advanced research WRF Model version 4. Technical report, 2019. Storm Prediction Center. The Enhanced Fujita Scale (EF Scale), 2014. URL https://www.spc.noaa.gov/efscale/. R. A. Warren, H. A. Ramsay, S. T. Siems, M. J. Manton, J. R. Peter, A. Protat, and A. Pillalamarri. Radar-based climatology of damaging hailstorms in Brisbane and Sydney, Australia. Quart. J. Roy. Meteor. Soc., 146:505–530, 2020. doi:10.1002/qj.3693.

Abstract Previous total lightning climatology studies using Tropical Rainfall Measuring Mission (TRMM) Lightning Imaging Sensor (LIS) observations were reported at coarse resolution (0.5°) and employed significant spatial and temporal smoothing to account for sampling limitations of TRMM’s tropical to subtropical low-Earth-orbit coverage. The analysis reported here uses a 16-yr reprocessed dataset to create a very high-resolution (0.1°) climatology with no further spatial averaging. This analysis reveals that Earth’s principal lightning hotspot occurs over Lake Maracaibo in Venezuela, while the highest flash rate density hotspot previously found at the lower 0.5°-resolution sampling was found in the Congo basin in Africa. Lake Maracaibo’s pattern of convergent windflow (mountain–valley, lake, and sea breezes) occurs over the warm lake waters nearly year-round and contributes to nocturnal thunderstorm development 297 days per year on average. These thunderstorms are very localized, and their persistent development anchored in one location accounts for the high flash rate density. Several other inland lakes with similar conditions, that is, deep nocturnal convection driven by locally forced convergent flow over a warm lake surface, are also revealed. Africa is the continent with the most lightning hotspots, followed by Asia, South America, North America, and Australia. A climatological map of the local hour of maximum flash rate density reveals that most oceanic total lightning maxima are related to nocturnal thunderstorms, while continental lightning tends to occur during the afternoon. Most of the principal continental maxima are located near major mountain ranges, revealing the importance of local topography in thunderstorm development.

Abstract Rain drop size distributions retrieved from polarimetric radar measurements over regularly occurring thunderstorms over the islands north of Darwin, Australia, are used to test if aerosol contributions to the probability distributions of the drop size distribution parameters (median volume diameter and normalized intercept parameter) are detectable. The observations reported herein are such that differences in cloud properties arising from thermodynamic differences are minimized but even so may be a factor. However, there is a clear signature that high aerosol concentrations are correlated with smaller number concentrations and larger drops. This may be associated with enhanced ice multiplication processes for low aerosol concentration storms or other processes such as invigoration of the updrafts.

Severe surface wind gusts produced by thunderstorms have the potential to damage infrastructure and are a major hazard for society. Wind gust data are examined from 35 observing stations around Australia, with lightning observations used to indicate the occurrence of deep convective processes in the vicinity of the observed wind gusts. A collation of severe thunderstorm reports is also used to complement the station wind gust data. Atmospheric reanalysis data are used to systematically examine large-scale environmental measures associated with severe convective winds. We find that methods based on environmental measures provide a better indication of the observed severe convective winds than the simulated model wind gusts from the reanalysis data, noting that the spatial scales on which these events occur are typically smaller than the reanalysis grid cells. Consistent with previous studies in other regions and idealised modelling, the majority of severe convective wind events are found to occur in environments with steep mid-level tropospheric lapse rates, moderate convective instability and strong background wind speeds. A large proportion of events from measured station data occur with relatively dry environmental air at low levels, although it is unknown to what extent this type of environment is representative of other severe wind-producing convective modes in Australia. The occurrence of severe convective winds is found to be well represented by a number of indices used previously for forecasting applications, such as the weighted product of convective available potential energy (CAPE) and vertical wind shear, the derecho composite parameter and the total totals index, as well as by logistic regression methods applied to environmental variables. Based on the systematic approach used in this study, our findings provide new insight on spatio-temporal variations in the risk of damaging winds occurring, including the environmental factors associated with their occurrence.

This paper investigates 7 MHz ionospheric radio wave propagation between pairs of distant countries that simultaneously lie on the terminator. This is known as greyline propagation. Observations of amateur radio beacon transmitters recorded in the Weak Signal Propagation Reporter (WSPR) database are used to investigate the times of day that beacon signals were observed during the year 2017. The WSPR beacon network consists of thousands of automated beacon transmitters and observers distributed over the globe. The WSPR database is a very useful resource for radio science as it offers the date and time at which a propagation path was available between two radio stations, as well as their precise locations. This paper provides the first systematic study of grey-line propagation between New Zealand/Eastern Australia and UK/Europe. The study shows that communications were predominantly made from the United Kingdom (UK) to New Zealand at around both sunset and sunrise times, whereas from New Zealand to the UK, communication links occurred mainly during UK sunrise hours. The lack of observations at the UK sunset time was particularly evident during the UK summer. The same pattern was found in the observations of propagation from Eastern Australia to UK, and from New Zealand and Eastern Australia to Italy and the surrounding regions in Europe. The observed asymmetry in reception pattern could possibly be due to the increase in electromagnetic noise across Europe in the summer afternoon/evening from thunderstorms.

Abstract. Cloud chemistry simulations were performed for a Hector thunderstorm observed on 16 November 2005 during the SCOUT-O3/ACTIVE campaigns based in Darwin, Australia, with the primary objective of estimating the average NO production per lightning flash in this unique storm type which occurred in a tropical island environment. The 3-D WRF-Aqueous Chemistry (WRF-AqChem) model is used for these calculations and contains the WRF nonhydrostatic cloud-resolving model with online gas- and aqueous-phase chemistry and a lightning-NOx (LNOx) production algorithm. The model was initialized by inducing convection with an idealized morning sounding and sensible heat source, and initial condition chemical profiles from merged aircraft observations in undisturbed air. Many features of the idealized model storm, such as storm size and peak radar reflectivity, were similar to the observed storm. Tracer species, such as CO, used to evaluate convective transport in the simulated storm found vertical motion from the boundary layer to the anvil region was well represented in the model, with a small overestimate of enhanced CO at anvil altitudes. The lightning detection network (LINET) provided lightning flash data for the model and a lightning placement scheme injected the resulting NO into the simulated cloud. A lightning NO production scenario of 500 moles flash−1 for both CG and IC flashes yielded anvil NOx mixing ratios that compared well with aircraft observations and were also similar to those deduced for several convective modeling analyses in the midlatitudes and subtropics. However, these NO production values were larger than most estimates for tropical thunderstorms and given several uncertainties, LNOx production may have been as large as 600 moles flash−1. Approximately 85% of the simulated LNOx mass was located above 7 km in the later stages of the storm, which was greater than amounts found for subtropical and midlatitude convection. Modeled upper tropospheric NO2 partial columns were also considerably greater than most satellite observations of tropical marine convective events, as tropical island convection, such as Hector, is more vigorous and more productive of LNOx. Additional research is needed to investigate whether LNOx production per flash increases in storms with greater wind shear, such as this Hector storm, which showed significant variation in wind direction with altitude.

Abstract A trend of increasing rainfall over much of north and northwest Australia over recent decades has contrasted with decreases over much of the rest of the continent. The increases have occurred during the summer months when the rainy season is dominated by the Australian monsoon but is also affected by other events such as tropical cyclones, Madden–Julian oscillations, and sporadic thunderstorms. The problem of diagnosing these trends is considered in terms of changes in the timing of the rainy season. While numerous definitions for rainy/monsoon season onset exist, most are designed to be useful in a predictive sense and can be limited in their application to diagnostic studies, particularly when they involve predetermined threshold amounts. Here the authors define indices, based on daily rainfall observations, that provide relatively simple, robust descriptions of each rainy season at any location. These are calculated using gridded daily rainfall data throughout the northern Australian tropics and also for selected stations. The results indicate that the trends in summer rainfall totals over the period from 1950 to 2005 appear to be mainly the result of similar trends in average intensity. Furthermore, the links between the September–October average Southern Oscillation index indicate that ENSO events affect season duration rather than average intensity. Because duration and average intensity are derived as independent features of each season, it is argued that the trends in rainfall totals are largely unrelated to trends in ENSO and most likely reflect the influence of other factors. Finally, diagnosing these features of the rainy season provides a basis for assessing the confidence one can attach to different climate model projections of changes to rainfall.

Abstract. Cloud chemistry simulations are performed for a Hector storm observed on 16 November 2005 during the SCOUT-O3/ACTIVE campaigns based in Darwin, Australia, with the primary objective of estimating the average production of NO per lightning flash during the storm which occurred in a tropical environment. The 3-D WRF-AqChem model (Barth et al., 2007a) containing the WRF nonhydrostatic cloud-resolving model, online gas- and aqueous-phase chemistry, and a lightning-NOx production algorithm is used for these calculations. An idealized early morning sounding of temperature, water vapor, and winds is used to initialize the model. Surface heating of the Tiwi Islands is simulated in the model to induce convection. Aircraft observations from air undisturbed by the storm are used to construct composite initial condition chemical profiles. The idealized model storm has many characteristics similar to the observed storm. Convective transport in the idealized simulated storm is evaluated using tracer species, such as CO and O3. The convective transport of CO from the boundary layer to the anvil region was well represented in the model, with a small overestimate of the increase of CO at anvil altitudes. Lightning flashes observed by the LIghtning detection NETwork (LINET) are input to the model and a lightning placement scheme is used to inject the resulting NO into the simulated cloud. We find that a lightning NO production scenario of 500 moles per flash for both CG and IC flashes yields anvil NOx mixing ratios that match aircraft observations well for this storm. These values of NO production nearly match the mean values for CG and IC flashes obtained from similar modeling analyses conducted for several midlatitude and subtropical convective events and are larger than most other estimates for tropical thunderstorms. Approximately 85% of the lightning NOx mass was located at altitudes greater than 7 km in the later stages of the storm, which is an amount greater than found for subtropical and midlatitude storms. Upper tropospheric NO2 partial columns computed from the model output are also considerably greater than observed by satellite for most tropical marine convective events, as tropical island convection, such as Hector, is more vigorous and more productive of lightning NOx.

Abstract Thunderstorm-affected communities develop an awareness of “hotspot” regions that historically experience more frequent or intense storm activity across many years. A scientifically based understanding of this localized variability has significant implications for both the public and industry; however, a lack of sufficiently long and robust observational datasets has limited prior research at the mesogamma spatial scale (2–20 km). This is particularly true for coastal environments, where hotspot activity has been documented in very few locales (e.g., Florida, southern Appalachian coastal plains, and the Iberian Peninsula), despite 45% of the global population living within 150 km of the coast. The Coastal Convective Interactions Experiment (CCIE) focuses on quantifying hailstorm hotspot activity for the coastal South East Queensland (SEQ) region of Australia and understanding the meteorological conditions that result in the spatial clustering of hailstorm activity. An automated thunderstorm identification and tracking technique applied to 18 years of radar data identifies not only the hailstorm hotpots well known to experienced local forecasters but an apparent link between localized maxima and the presence of sea-breeze activity. These climatological findings provided the motivation and guidance for a two-season field campaign to investigate the role of the sea breeze in thunderstorm development. Details of the experiment strategy and equipment specifications are presented alongside preliminary results. Significant complexities were observed within sea-breeze and thunderstorms circulations, limiting the application of standard concepts for idealized gravity current interactions. Furthermore, a multi-instrument case study of a sea-breeze–thunderstorm cold pool interaction identifies the comparatively low sea-breeze buoyancy as the primary contributor toward inhibiting new convective initiation, despite the vorticity balance argument favoring deeper updrafts.

Abstract. Regional reanalyses provide a dynamically consistent recreation of past weather observations at scales useful for local-scale environmental applications. The development of convection-permitting models (CPMs) in numerical weather prediction has facilitated the creation of kilometre-scale (1–4 km) regional reanalysis and climate projections. The Bureau of Meteorology Atmospheric high-resolution Regional Reanalysis for Australia (BARRA) also aims to realize the benefits of these high-resolution models over Australian sub-regions for applications such as fire danger research by nesting them in BARRA's 12 km regional reanalysis (BARRA-R). Four midlatitude sub-regions are centred on Perth in Western Australia, Adelaide in South Australia, Sydney in New South Wales (NSW), and Tasmania. The resulting 29-year 1.5 km downscaled reanalyses (BARRA-C) are assessed for their added skill over BARRA-R and global reanalyses for near-surface parameters (temperature, wind, and precipitation) at observation locations and against independent 5 km gridded analyses. BARRA-C demonstrates better agreement with point observations for temperature and wind, particularly in topographically complex regions and coastal regions. BARRA-C also improves upon BARRA-R in terms of the intensity and timing of precipitation during the thunderstorm seasons in NSW and spatial patterns of sub-daily rain fields during storm events. BARRA-C reflects known issues of CPMs: overestimation of heavy rain rates and rain cells, as well as underestimation of light rain occurrence. As a hindcast-only system, BARRA-C largely inherits the domain-averaged bias pattern from BARRA-R but does produce different climatological extremes for temperature and precipitation. An added-value analysis of temperature and precipitation extremes shows that BARRA-C provides additional skill over BARRA-R when compared to gridded observations. The spatial patterns of BARRA-C warm temperature extremes and wet precipitation extremes are more highly correlated with observations. BARRA-C adds value in the representation of the spatial pattern of cold extremes over coastal regions but remains biased in terms of magnitude.

AbstractA major thunderstorm asthma epidemic struck Melbourne and surrounding Victoria, Australia, on 21 November 2016, which led to multiple deaths, a flood of residents seeking medical attention for respiratory problems, and an overwhelmed emergency management system. This case day had all the classic ingredients for an epidemic, including high rye grass pollen concentrations, a strong multicellular thunderstorm system moving across the region, and a large population of several million people in the vicinity of Melbourne. A particular characteristic of this event was the strong, gusty winds that likely spread the pollen grains and/or allergenic contents widely across the region to increase population exposure. This exploratory case study is the first to examine the usefulness of low-to-middle-atmospheric thermodynamic information for anticipating epidemic thunderstorm asthma outbreaks by allowing the forecast of strong downdraft winds. The authors investigated the utility of several mesoscale products derived from atmospheric soundings such as downdraft convective available potential energy (DCAPE) and indices for predicting surface wind gusts such as microburst wind speed potential index (MWPI) and a wind gust index (GUSTEX). These results indicate that DCAPE levels reached “high” to “very high” thresholds for strong downdraft winds in the lead-up to the thunderstorm, and the MWPI and GUSTEX indices accurately predicted the high maximum surface wind observations. This information may be useful for diagnostic and prognostic assessment of epidemic thunderstorm asthma and in providing an early warning to health practitioners, emergency management officials, and residents in affected areas.

Abstract. This paper describes lightning characteristics as obtained in four sets of lightning measurements during recent field campaigns in different parts of the world from mid-latitudes to the tropics by the novel VLF/LF (very low frequency/low frequency) lightning detection network (LINET). The paper gives a general overview on the approach, and a synopsis of the statistical results for the observation periods as a whole and for one special day in each region. The focus is on the characteristics of lightning which can specifically be observed by this system like intra-cloud and cloud-to-ground stroke statistics, vertical distributions of intra-cloud strokes or peak current distributions. Some conclusions regarding lightning produced NOx are also presented as this was one of the aims of the tropical field campaigns TROCCINOX (Tropical Convection, Cirrus and Nitrogen Oxides Experiment) and TroCCiBras (Tropical Convection and Cirrus Experiment Brazil) in Brazil during January/February 2005, SCOUT-O3 (Stratospheric-Climate Links with Emphasis on the Upper Troposphere and Lower Stratosphere) and TWP-ICE (Tropical Warm Pool – International Cloud Experiment) during November/December 2005 and January/February 2006, respectively, in the Darwin area in N-Australia, and of AMMA (African Monsoon Multidisciplinary Analyses) in W-Africa during June–November 2006. Regional and temporal characteristics of lightning are found to be dependent on orographic effects (e.g. S-Germany, Brazil, Benin), land-sea breeze circulations (N-Australia) and especially the evolution of the monsoons (Benin, N-Australia). Large intra-seasonal variability in lightning occurrence was found for the Australian monsoon between the strong convection during build-up and break phases and the weak wet monsoon phase with only minor lightning activity. Total daily lightning rates can be of comparable intensity in all regions with the heaviest events found in Germany and N-Australia. The frequency of occurrence of such days was by far the largest in N-Australia. In accordance with radar observed storm structures, the intra-cloud stroke mean emission heights were found distinctly different in Germany (8 km) as compared to the tropics (up to 12 km in N-Australia). The fraction of intra-cloud strokes (compared to all strokes) was found to be relatively high in Brazil and Australia (0.83 and 0.74, respectively) as compared to Benin and Germany (0.67 and 0.69, respectively). Using stroke peak currents and vertical location information, lightning NOx (LNOx) production under defined standard conditions can be compared for the different areas of observation. LNOx production per standard stroke was found to be most efficient for the N-Australian and S-German thunderstorms whereas the yield from Brazilian and W-African strokes was nearly 40% less. On the other hand, the main NO contribution in Brazil was from intra-cloud (IC) strokes whereas in Benin it was due to cloud-to-ground (CG) components. For the German and Australian strokes both stroke types contributed similar amounts to the total NO outcome.

Abstract. This paper describes lightning characteristics as obtained in four sets of lightning measurements during recent field campaigns in different parts of the world from mid-latitudes to the tropics by the novel VLF/LF (very low frequency/low frequency) lightning detection network (LINET). The paper gives a general overview on the approach, and a synopsis of the statistical results for the observation periods as a whole and for one special day in each region. The focus is on the characteristics of lightning which can specifically be observed by this system like intra-cloud and cloud-to-ground stroke statistics, vertical distributions of intra-cloud strokes or peak current distributions. Some conclusions regarding lightning produced NOx are also presented as this was one of the aims of the tropical field campaigns TROCCINOX (Tropical Convection, Cirrus and Nitrogen Oxides Experiment) and TroCCiBras (Tropical Convection and Cirrus Experiment Brazil) in Brazil during January/February 2005, SCOUT-O3 (Stratospheric-Climate Links with Emphasis on the Upper Troposphere and Lower Stratosphere) and TWP-ICE (Tropical Warm Pool-International Cloud Experiment) during November/December 2005 and January/February 2006, respectively, in the Darwin area in N-Australia, and of AMMA (African Monsoon Multidisciplinary Analyses) in W-Africa during June–November 2006. Regional and temporal characteristics of lightning are found to be dependent on orographic effects (e.g. S-Germany, Brazil, Benin), land-sea breeze circulations (N-Australia) and especially the evolution of the monsoons (Benin, N-Australia). Large intra-seasonal variability in lightning occurrence was found for the Australian monsoon between the strong convection during build-up and break phases and the weak active monsoon phase with only minor lightning activity. Total daily lightning stroke rates can be of comparable intensity in all regions with the heaviest events found in Germany and N-Australia. The frequency of occurrence of such days was by far the largest in N-Australia. In accordance with radar observed storm structures, the intra-cloud stroke mean emission heights were found distinctly different in Germany (8 km) as compared to the tropics (up to 12 km in N-Australia). The fraction of intra-cloud strokes (compared to all strokes) was found to be relatively high in Brazil and Australia (0.83 and 0.82, respectively) as compared to Benin and Germany (0.64 and 0.69, respectively). Using stroke peak currents and vertical location information, lightning NOx (LNOx) production under defined standard conditions can be compared for the different areas of observation. LNOx production per standard stroke was found to be most efficient for the N-Australian and S-German thunderstorms whereas the yield from Brazilian and W-African strokes was nearly 40% less. On the other hand, the main NO contribution in Brazil was from intra-cloud (IC) strokes whereas in Benin it was due to cloud-to-ground (CG) components. For the German and Australian strokes both stroke types contributed similar amounts to the total NO outcome.

Abstract The charge distributions in a thundercloud play an important role in the initiation and propagation of lightning discharges. To further understand the effects of charge distributions on lightning discharge, the authors conducted a very high-frequency (VHF) lightning observation campaign during the 2006/07 monsoon in Darwin, Australia, using a VHF broadband digital interferometer (DITF). A C-band polarimetric weather radar to estimate the precipitation profiles such as hydrometeor classification was operated by the Bureau of Meteorology (BOM) Research Centre. Cloud-to-ground (CG) and intracloud (IC) flashes were initiated from the outer and the inner parts of the upper side of the graupel regions, respectively. In the cases of CG flashes, the negative leaders travel first about 10 km horizontally through positive charge regions and then begin to bend toward the ground when they reach the edge of the positive charge regions where there is no graupel region underneath. In contrast, in the cases of the IC flashes the negatively charged graupel regions block the downward developments of negative leaders. It is noted that positive charge regions could facilitate the extension of the horizontal negative leader. These results may suggest that lightning flash types are closely dependent on their initiation locations and the surrounding charge distributions. The experimental results are consistent with other previous observation results and charge model simulations.

On 15 April 2009, the Automatic Weather Station (AWS) at Scottsdale, in north-eastern Tasmania, recorded a wind gust of 54 ms-1 (194 kmh-1) as an active squall line crossed the state. Investigation of the environment, instrumentation, and damage resulted in the conclusion that this was a genuine wind gust caused by a tornado passing very close to the anemometer. This was the first direct AWS observation of a tornado in Australia, and one of very few such observations in the world. In this report, we document the weather event which produced the tornado, briefly outline the synoptic situation leading to its occurrence, document additional background observations that provide context for the event, and discuss the nature of the observations made by the AWS and the method by which the wind gust observations were verified.The squall line was part of a cold front that crossed northern Tasmania on the morning of 15 April 2009. At 300 hPa, the orientation of the short-wave trough associated with the cold front changed from positively to strongly negatively tilted as it moved over central Victoria and Tasmania. The orientation of the trough and position of a jet streak within it suggested strong upper divergence and strong vertical motion. These contributed to thunderstorm development and resulted in very substantial vertical wind shear through the lower half of the troposphere, which in turn contributed to the organisation of the severe convection. Near the surface, low cloud base and strong vertical windshear in the lowest kilometre provided conditions conducive to tornado development.

Local severe storms are extreme weather events that last only for a few hours and evolve rapidly. Very often the mesoscale features associated these local severe storms are not well-captured synoptically. Forecasters have to predict the changing weather situation in the next 0-6 hrs based on latest observations. The operational process to predict the weather in the next 0-6 hrs is known as “nowcast”. Observational data that are typically suited for nowcasting includes Doppler Weather Radar (DWR), wind profiler, microwave sounder and satellite radiance. To assist forecasters, in predicting the weather information and making warning decisions, various nowcasting systems have been developed by various countries in recent years. Notable examples are Auto-Nowcaster (U.S.), BJ-ANC (China-U.S.), CARDS (Canada), GRAPES-SWIFT (China), MAPLE (Canada), NIMROD (U.K.), NIWOT (U.S.), STEPS (Australia), SWIRLS (Hong Kong, China), TIFS (Australia), TITAN (U.S.) (Dixon and Wiener, 1993) and WDSS (U.S.). Some of these systems were used in the two forecast demonstration projects organized by WMO for the Sydney 2000 and Beijing 2008 Olympic. A common feature of these systems is that they all use rapidly updated radar data, typically once every 6 minutes.The nowcasting system SWIRLS (“Short-range Warning of Intense Rainstorms in Localized Systems”) has been developed by the Hong Kong Observatory (HKO) and was put into operation in Hong Kong in 1999. Since then system has undergone several upgrades, the latest known as “SWIRLS-2” to support the Beijing 2008 Olympic Games. SWIRLS-2 is being adapted by India Meteorological Department (IMD) for use and test for the Commonwealth Games 2010 at New Delhi with assistance from HKO. SWIRLS-2 ingests a range of observation data including SIGMET/IRIS DWR radar product, raingauge data, radiosonde data, lightning data to analyze and predict reflectivity, radar-echo motion, QPE, QPF, as well as track of thunderstorm and its associated severe weather, including cloud-to-ground lightning, severe squalls and hail, and probability of precipitation. SWIRLS-2 uses a number of algorithms to derive the storm motion vectors. These include TREC (“Tracking of Radar Echoes by Correlation”), GTrack (Group tracking of radar echoes, an object-oriented technique for tracking the movement of a storm as a whole entity) and lately MOVA (“Multi-scale Optical flow by Variational Analysis”). This latest algorithm uses optical flow, a technique commonly used in motion detection in image processing, and variational analysis to derive the motion vector field. By cascading through a range of scales, MOVA can better depict the actual storm motion vector field as compared with TREC and GTrack which does well in tracking small scales features and storm entity respectively. In this paper the application of TREC and MOVA to derive the storm motion vector, reflectivity and QPF using Indian DWR data has been demonstrated for the thunderstorm events over Kolkata and New Delhi. The system has been successfully operationalized for Delhi and neighborhood area for commonwealth games 2010. Real time products are available on IMD website

Abstract One event of a tropical thunderstorm typically observed in northern Australia, known as Hector, is investigated using high-resolution model output from the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5) observations from a ground-based weather radar located in Berrimah (Australia) and data from the Tropical Rainfall Measuring Mission (TRMM) satellite. The analysis is carried out by tracking the full life cycle of Hector from prestorm stage to the decaying stage. In both the prestorm stage, characterized by nonprecipitating cells, and the triggering stage, when the Hector storm is effectively initiated, an analysis is performed with the aid of high-spatial-and-temporal-resolution MM5 output and the Berrimah ground-based radar imagery. During the mature (“old”) stage of Hector, considering the conceptual model for tropical convection suggested by R. Houze, TRMM Microwave Imager satellite-based data were added to ground-based radar data to analyze the storm vertical structure (dynamics, thermodynamics, and hydrometeor contents). Model evaluation with respect to observations (radar reflectivity and TRMM data) suggests that MM5 performed fairly well in reproducing the dynamics of Hector, providing support to the assertion that the strength of convection, in terms of vertical velocity, largely contributes to the vertical distribution of hydrometeors. Moreover, the stages of the storm and its vertical structure display good agreement with Houze’s aforementioned conceptual model. Finally, it was found that the most important triggering mechanisms for this Hector event are topography, the sea breeze, and a gust front produced by previous convection.

The Waroona bushfire burnt 69,000 ha south of Perth in January 2016. During the first two days of the fire, there were two pyrocumulonimbus (pyroCb) events and two destructive evening fire runs. Over 160 homes were destroyed and there were two fatalities. This case study examines in detail the links between the meteorological observations and the fire behaviour reconstruction.The first pyroCb developed on Wednesday 6 January 2016, when the fire made an unexpectedly fast run in light prevailing winds. The pyroCb produced lightning strikes that ignited a new fire downwind of the main head fire. A second pyroCb developed on Thursday morning, against normal diurnal thunderstorm trends. Similar to the previous evening, the fire spread faster than expected, given the near-surface meteorological conditions.On both evenings there were destructive ember storms over the towns of Waroona (Wednesday) and Yarloop (Thursday). Examination of the meteorological observations has linked these ember showers to the onset of downslope winds, locally known as `scarp winds'. As downslope winds are associated with strong localised turbulence, they provide a mechanism for transport of large numbers of firebrands.The periods of extreme fire behaviour at Waroona were against normal diurnal expectations and did not coincide with the highest observed Fire Danger Index (FDI) values, which occurred at around 1600 LT. This study links both pyroCb events to accelerated fire spread, which presents a hazard to firefighters that is not accounted for in traditional, surface based methods of fire prediction. Downslope winds similar to those that impacted the Waroona fire occur at many locations. They provide a highly localised mechanism for destructive evening ember showers.This investigation into the Waroona fire describes the potential impacts of fireatmosphere feedback processes. Consequently, it highlights the need for predictive methods and tools that anticipate fire behaviour which is not steady-state. Planned simulations using a coupled fire-atmosphere model will allow further insights into features of this case study.

Abstract The development of a severe Hector thunderstorm that formed over the Tiwi Islands, north of Australia, during the Aerosol and Chemical Transport in Tropical Convection/Stratospheric-Climate Links with Emphasis on the Upper Troposphere and Lower Stratosphere (ACTIVE/SCOUT-O3) field campaign in late 2005, is simulated by the Advanced Research Weather Research and Forecasting (ARW) model and the Met Office Unified Model (UM). The general aim of this paper is to investigate the role of isolated deep convection over the tropics in regulating the water content in the upper troposphere/lower stratosphere (UT/LS). Using a horizontal resolution as fine as 1 km, the numerical simulations reproduce the timing, structure, and strength of Hector fairly well when compared with field campaign observations. The sensitivity of results from ARW to horizontal resolution is investigated by running the model in a large-eddy simulation mode with a horizontal resolution of 250 m. While refining the horizontal resolution to 250 m leads to a better representation of convection with respect to rainfall, the characteristics of the Hector thunderstorm are basically similar in space and time to those obtained in the 1-km-horizontal-resolution simulations. Several overshooting updrafts penetrating the tropopause are produced in the simulations during the mature stage of Hector. The penetration of rising towering cumulus clouds into the LS maintains the entrainment of air at the interface between the UT and the LS. Vertical exchanges resulting from this entrainment process have a significant impact on the redistribution of atmospheric constituents within the UT/LS region at the scale of the islands. In particular, a large amount of water is injected in the LS. The fate of the ice particles as Hector develops drives the water vapor mixing ratio to saturation by sublimation of the injected ice particles, moistening the air in the LS. The moistening was found to be fairly significant above 380 K and averaged about 0.06 ppmv in the range 380–420 K for ARW. As for UM, the moistening was found to be much larger (about 2.24 ppmv in the range of 380–420 K) than for ARW. This result confirms that convective transport can play an important role in regulating the water vapor mixing ratio in the LS.

Abstract. Extreme wildfires are global phenomena that consistently result in loss of life and property and further impact the cultural, economic and political stability of communities. In their most severe form they cause widespread devastation of environmental assets and are capable of impacting the upper troposphere/lower stratosphere through the formation of a thunderstorm within the plume. Such fires are now often observed by a range of remote-sensing technologies, which together allow a greater understanding of a fire's complex dynamics. This paper considers one such fire that burnt in the Blue Mountains region of Australia in late November 2006, which is known to have generated significant pyrocumulonimbus clouds in a series of blow-up events. Observations of this fire are analysed in detail to investigate the localised processes contributing to extreme fire development. In particular, it has been possible to demonstrate for the first time that the most violent instances of pyroconvection were driven by, and not just associated with, atypical local fire dynamics, especially the fire channelling phenomenon, which arises due to an interaction between an active fire, local terrain attributes and critical fire weather and causes the fire to rapidly transition from a frontal to an areal burning pattern. The impacts of local variations in fire weather and of the atmospheric profile are also discussed, and the ability to predict extreme fire development with state-of-the-art tools is explored.

Abstract. Extreme wildfires are global phenomena that consistently result in loss of life and property, and further impact the cultural, economic and political stability of communities. In their most extreme form they cause widespread devastation of environmental assets and are capable of impacting the upper troposphere–lower stratosphere through the formation of a thunderstorm within the plume. Such fires are now often observed by a range of remote sensing technologies, which together allow a greater understanding of a fire's complex dynamics. This paper considers one such fire that burnt in the Blue Mountains region of Australia in late-November 2006, that is known to have generated significant pyrocumulonimbus clouds in a series of blow-up events. Observations of this fire are analysed in detail to investigate the localised processes contributing to extreme fire development. In particular, it has been possible to demonstrate for the first time that the most severe instances of pyroconvection were driven by, and not just associated with, extreme local fire dynamics, especially the fire channelling phenomenon, which arises due to an interaction between an active fire, local terrain attributes and critical fire weather, and causes the fire to rapidly transition from a frontal to an areal burning pattern. The impacts of local variations in fire weather and of the atmospheric profile are also discussed, and the ability to predict extreme fire development with state-of-the-art tools is explored.

AbstractThe aim of this study is to examine the statistics of convective storms and their concomitant changes with thermodynamic variability. The thermodynamic variability is analyzed by performing a cluster analysis on variables derived from radiosonde releases at Brisbane Airport in Australia. Three objectively defined regimes are found: a dry, stable regime with mainly westerly surface winds, a moist northerly regime, and a moist trade wind regime. S-band radar data are analyzed and storms are identified using objective tracking software [Thunderstorm Identification, Tracking, Analysis, and Nowcasting (TITAN)]. Storm statistics are then investigated, stratified by the regime subperiods. Convective storms are found to form and maintain along elevated topography. Probability distributions of convective storm size and rain rate are found to follow lognormal distributions with differing mean and variance among the regimes. There was some evidence of trimodal storm-top heights, located at the trade inversion (1.5–2 km), freezing level (3.6–4 km), and near 6 km, but it was dependent on the presence of the trade inversion. On average, storm volume and height are smallest in the trade regime and rain rate is largest in the westerly regime. However, westerly regime storms occur less frequently and have shorter lifetimes, which were attributed to the enhanced stability and decreased humidity profiles. Furthermore, time series of diurnal rain rate exhibited early morning and midafternoon maxima for the northerly and trade regimes but were absent for the westerly regime. The observations indicate that westerly regime storms are primarily driven by large-scale forcing, whereas northerly and trade wind regime storms are more responsive to surface characteristics.

Abstract. Although lightning-generated oxides of nitrogen (LNOx) account for only approximately 10 % of the global NOx source, they have a disproportionately large impact on tropospheric photochemistry due to the conducive conditions in the tropical upper troposphere where lightning is mostly discharged. In most global composition models, lightning flash rates used to calculate LNOx are expressed in terms of convective cloud-top height via the Price and Rind (1992) (PR92) parameterisations for land and ocean, where the oceanic parameterisation is known to greatly underestimate flash rates. We conduct a critical assessment of flash-rate parameterisations that are based on cloud-top height and validate them within the Australian Community Climate and Earth System Simulator – United Kingdom Chemistry and Aerosol (ACCESS-UKCA) global chemistry–climate model using the Lightning Imaging Sensor and Optical Transient Detector (LIS/OTD) satellite data. While the PR92 parameterisation for land yields satisfactory predictions, the oceanic parameterisation, as expected, underestimates the observed flash-rate density severely, yielding a global average over the ocean of 0.33 flashes s−1 compared to the observed 9.16 flashes s−1 and leading to LNOx being underestimated proportionally. We formulate new flash-rate parameterisations following Boccippio's (2002) scaling relationships between thunderstorm electrical generator power and storm geometry coupled with available data. The new parameterisation for land performs very similarly to the corresponding PR92 one, as would be expected, whereas the new oceanic parameterisation simulates the flash-rate observations much more accurately, giving a global average over the ocean of 8.84 flashes s−1. The use of the improved flash-rate parameterisations in ACCESS-UKCA changes the modelled tropospheric composition – global LNOx increases from 4.8 to 6.6 Tg N yr−1; the ozone (O3) burden increases by 8.5 %; there is an increase in the mid- to upper-tropospheric NOx by as much as 40 pptv, a 13 % increase in the global hydroxyl radical (OH), a decrease in the methane lifetime by 6.7 %, and a decrease in the lower-tropospheric carbon monoxide (CO) by 3 %–7 %. Compared to observations, the modelled tropospheric NOx and ozone in the Southern Hemisphere and over the ocean are improved by this new flash-rate parameterisation.

Abstract Severe winds associated with thunderstorms and convection are a hazard affecting key aspects of society, including emergency management and infrastructure design. Several studies around the world have shown that severe convective winds (SCWs) can occur due to several different processes, in a range of atmospheric environments, with significant regional and temporal variations. However, in eastern Australia, the types of SCWs and their variability have not been assessed outside of individual case studies. Here, a combination of reanalysis, lightning, radar and station data are used to characterise a set of 36 SCW events in four locations in eastern Australia. These events are objectively chosen based on the strongest measured wind gusts from station data (greater than 25 m/s) over a 14-year period, with 6-hourly lightning data and a 30 dBZ radar reflectivity threshold used to infer moist convective processes. Radar data analysis suggests that these SCW events are produced by several different types of parent thunderstorms, with station observations suggesting a range of temporal characteristics for these different event types. A clustering algorithm applied to environmental data is used to suggest three dominant types of events, based on low-level moisture, low-level temperature lapse rate, and deep-layer mean wind speed and vertical shear. Based on the distribution of synoptic conditions and thunderstorm properties for each environmental cluster, it is suggested that these three event types correspond to: 1) shallow vertical transport of strong synoptic-scale winds to the surface, 2) downbursts driven by sub-cloud evaporation, and 3) intense thunderstorms including supercells.

AbstractFire activity in Australia is strongly affected by high inter-annual climate variability and extremes. Through changes in the climate, anthropogenic climate change has the potential to alter fire dynamics. Here we compile satellite (19 and 32 years) and ground-based (90 years) burned area datasets, climate and weather observations, and simulated fuel loads for Australian forests. Burned area in Australia’s forests shows a linear positive annual trend but an exponential increase during autumn and winter. The mean number of years since the last fire has decreased consecutively in each of the past four decades, while the frequency of forest megafire years (>1 Mha burned) has markedly increased since 2000. The increase in forest burned area is consistent with increasingly more dangerous fire weather conditions, increased risk factors associated with pyroconvection, including fire-generated thunderstorms, and increased ignitions from dry lightning, all associated to varying degrees with anthropogenic climate change.

Internal pressurisation of buildings during a severe wind event, such as a tropical cyclone or thunderstorm, can often cause severe structural failures, as observed during damage investigations. Wind loading standards worldwide provide design data for internal pressure design. However, the implementation of these data often depends on the location of the building in relation to the levels of wind hazard in the relevant country. Recent observations during Tropical Cyclone (TC) Seroja in an intermediate wind region (wind region B) in Western Australia indicated the need for the design for full internal pressures of buildings in this wind region. This paper presents an overview of the damage investigation conducted after TC Seroja that highlights significant damage to buildings due to the lack of design for internal pressures. Additionally, a case study of a house modelled using the vulnerability analysis software VAWS is presented showing the improvements in the performance of buildings designed for internal pressures. TheVAWS models showed that both the design for full internal pressure and the use of debris rated shutters were both effective at reducing the level of serious structural damage and making houses more resilient. The robustness and resilience of buildings increase significantly if they are designed for high internal pressure because the failure of a window or door (a local failure) will not lead to a major structural failure.

Introduction This article is a study in anxiety with regard to social online spaces (SOS) conceived of as dark. There are two possible ways to define ‘dark’ in this context. The first is that communication is dark because it either has limited distribution, is not open to all users (closed groups are a case example) or hidden. The second definition, linked as a result of the first, is the way that communication via these means is interpreted and understood. Dark social spaces disrupt the accepted top-down flow by the ‘gazing elite’ (data aggregators including social media), but anxious users might need to strain to notice what is out there, and this in turn destabilises one’s reception of the scene. In an environment where surveillance technologies are proliferating, this article examines contemporary, dark, interconnected, and interactive communications for the entangled affordances that might be brought to bear. A provocation is that resistance through counterveillance or “sousveillance” is one possibility. An alternative (or addition) is retreating to or building ‘dark’ spaces that are less surveilled and (perhaps counterintuitively) less fearful. This article considers critically the notion of dark social online spaces via four broad socio-technical concerns connected to the big social media services that have helped increase a tendency for fearful anxiety produced by surveillance and the perceived implications for personal privacy. It also shines light on the aspect of darkness where some users are spurred to actively seek alternative, dark social online spaces. Since the 1970s, public-key cryptosystems typically preserved security for websites, emails, and sensitive health, government, and military data, but this is now reduced (Williams). We have seen such systems exploited via cyberattacks and misappropriated data acquired by affiliations such as Facebook-Cambridge Analytica for targeted political advertising during the 2016 US elections. Via the notion of “parasitic strategies”, such events can be described as news/information hacks “whose attack vectors target a system’s weak points with the help of specific strategies” (von Nordheim and Kleinen-von Königslöw, 88). In accord with Wilson and Serisier’s arguments (178), emerging technologies facilitate rapid data sharing, collection, storage, and processing wherein subsequent “outcomes are unpredictable”. This would also include the effect of acquiescence. In regard to our digital devices, for some, being watched overtly—through cameras encased in toys, computers, and closed-circuit television (CCTV) to digital street ads that determine the resonance of human emotions in public places including bus stops, malls, and train stations—is becoming normalised (McStay, Emotional AI). It might appear that consumers immersed within this Internet of Things (IoT) are themselves comfortable interacting with devices that record sound and capture images for easy analysis and distribution across the communications networks. A counter-claim is that mainstream social media corporations have cultivated a sense of digital resignation “produced when people desire to control the information digital entities have about them but feel unable to do so” (Draper and Turow, 1824). Careful consumers’ trust in mainstream media is waning, with readers observing a strong presence of big media players in the industry and are carefully picking their publications and public intellectuals to follow (Mahmood, 6). A number now also avoid the mainstream internet in favour of alternate dark sites. This is done by users with “varying backgrounds, motivations and participation behaviours that may be idiosyncratic (as they are rooted in the respective person’s biography and circumstance)” (Quandt, 42). By way of connection with dark internet studies via Biddle et al. (1; see also Lasica), the “darknet” is a collection of networks and technologies used to share digital content … not a separate physical network but an application and protocol layer riding on existing networks. Examples of darknets are peer-to-peer file sharing, CD and DVD copying, and key or password sharing on email and newsgroups. As we note from the quote above, the “dark web” uses existing public and private networks that facilitate communication via the Internet. Gehl (1220; see also Gehl and McKelvey) has detailed that this includes “hidden sites that end in ‘.onion’ or ‘.i2p’ or other Top-Level Domain names only available through modified browsers or special software. Accessing I2P sites requires a special routing program ... . Accessing .onion sites requires Tor [The Onion Router]”. For some, this gives rise to social anxiety, read here as stemming from that which is not known, and an exaggerated sense of danger, which makes fight or flight seem the only options. This is often justified or exacerbated by the changing media and communication landscape and depicted in popular documentaries such as The Social Dilemma or The Great Hack, which affect public opinion on the unknown aspects of internet spaces and the uses of personal data. The question for this article remains whether the fear of the dark is justified. Consider that most often one will choose to make one’s intimate bedroom space dark in order to have a good night’s rest. We might pleasurably escape into a cinema’s darkness for the stories told therein, or walk along a beach at night enjoying unseen breezes. Most do not avoid these experiences, choosing to actively seek them out. Drawing this thread, then, is the case made here that agency can also be found in the dark by resisting socio-political structural harms. 1. Digital Futures and Anxiety of the Dark Fear of the darkI have a constant fear that something's always nearFear of the darkFear of the darkI have a phobia that someone's always there In the lyrics to the song “Fear of the Dark” (1992) by British heavy metal group Iron Maiden is a sense that that which is unknown and unseen causes fear and anxiety. Holding a fear of the dark is not unusual and varies in degree for adults as it does for children (Fellous and Arbib). Such anxiety connected to the dark does not always concern darkness itself. It can also be a concern for the possible or imagined dangers that are concealed by the darkness itself as a result of cognitive-emotional interactions (McDonald, 16). Extending this claim is this article’s non-binary assertion that while for some technology and what it can do is frequently misunderstood and shunned as a result, for others who embrace the possibilities and actively take it on it is learning by attentively partaking. Mistakes, solecism, and frustrations are part of the process. Such conceptual theorising falls along a continuum of thinking. Global interconnectivity of communications networks has certainly led to consequent concerns (Turkle Alone Together). Much focus for anxiety has been on the impact upon social and individual inner lives, levels of media concentration, and power over and commercialisation of the internet. Of specific note is that increasing commercial media influence—such as Facebook and its acquisition of WhatsApp, Oculus VR, Instagram, CRTL-labs (translating movements and neural impulses into digital signals), LiveRail (video advertising technology), Chainspace (Blockchain)—regularly changes the overall dynamics of the online environment (Turow and Kavanaugh). This provocation was born out recently when Facebook disrupted the delivery of news to Australian audiences via its service. Mainstream social online spaces (SOS) are platforms which provide more than the delivery of media alone and have been conceptualised predominantly in a binary light. On the one hand, they can be depicted as tools for the common good of society through notional widespread access and as places for civic participation and discussion, identity expression, education, and community formation (Turkle; Bruns; Cinque and Brown; Jenkins). This end of the continuum of thinking about SOS seems set hard against the view that SOS are operating as businesses with strategies that manipulate consumers to generate revenue through advertising, data, venture capital for advanced research and development, and company profit, on the other hand. In between the two polar ends of this continuum are the range of other possibilities, the shades of grey, that add contemporary nuance to understanding SOS in regard to what they facilitate, what the various implications might be, and for whom. By way of a brief summary, anxiety of the dark is steeped in the practices of privacy-invasive social media giants such as Facebook and its ancillary companies. Second are the advertising technology companies, surveillance contractors, and intelligence agencies that collect and monitor our actions and related data; as well as the increased ease of use and interoperability brought about by Web 2.0 that has seen a disconnection between technological infrastructure and social connection that acts to limit user permissions and online affordances. Third are concerns for the negative effects associated with depressed mental health and wellbeing caused by “psychologically damaging social networks”, through sleep loss, anxiety, poor body image, real world relationships, and the fear of missing out (FOMO; Royal Society for Public Health (UK) and the Young Health Movement). Here the harms are both individual and societal. Fourth is the intended acceleration toward post-quantum IoT (Fernández-Caramés), as quantum computing’s digital components are continually being miniaturised. This is coupled with advances in electrical battery capacity and interconnected telecommunications infrastructures. The result of such is that the ontogenetic capacity of the powerfully advanced network/s affords supralevel surveillance. What this means is that through devices and the services that they provide, individuals’ data is commodified (Neff and Nafus; Nissenbaum and Patterson). Personal data is enmeshed in ‘things’ requiring that the decisions that are both overt, subtle, and/or hidden (dark) are scrutinised for the various ways they shape social norms and create consequences for public discourse, cultural production, and the fabric of society (Gillespie). Data and personal information are retrievable from devices, sharable in SOS, and potentially exposed across networks. For these reasons, some have chosen to go dark by being “off the grid”, judiciously selecting their means of communications and their ‘friends’ carefully. 2. Is There Room for Privacy Any More When Everyone in SOS Is Watching? An interesting turn comes through counterarguments against overarching institutional surveillance that underscore the uses of technologies to watch the watchers. This involves a practice of counter-surveillance whereby technologies are tools of resistance to go ‘dark’ and are used by political activists in protest situations for both communication and avoiding surveillance. This is not new and has long existed in an increasingly dispersed media landscape (Cinque, Changing Media Landscapes). For example, counter-surveillance video footage has been accessed and made available via live-streaming channels, with commentary in SOS augmenting networking possibilities for niche interest groups or micropublics (Wilson and Serisier, 178). A further example is the Wordpress site Fitwatch, appealing for an end to what the site claims are issues associated with police surveillance (fitwatch.org.uk and endpolicesurveillance.wordpress.com). Users of these sites are called to post police officers’ identity numbers and photographs in an attempt to identify “cops” that might act to “misuse” UK Anti-terrorism legislation against activists during legitimate protests. Others that might be interested in doing their own “monitoring” are invited to reach out to identified personal email addresses or other private (dark) messaging software and application services such as Telegram (freeware and cross-platform). In their work on surveillance, Mann and Ferenbok (18) propose that there is an increase in “complex constructs between power and the practices of seeing, looking, and watching/sensing in a networked culture mediated by mobile/portable/wearable computing devices and technologies”. By way of critical definition, Mann and Ferenbok (25) clarify that “where the viewer is in a position of power over the subject, this is considered surveillance, but where the viewer is in a lower position of power, this is considered sousveillance”. It is the aspect of sousveillance that is empowering to those using dark SOS. One might consider that not all surveillance is “bad” nor institutionalised. It is neither overtly nor formally regulated—as yet. Like most technologies, many of the surveillant technologies are value-neutral until applied towards specific uses, according to Mann and Ferenbok (18). But this is part of the ‘grey area’ for understanding the impact of dark SOS in regard to which actors or what nations are developing tools for surveillance, where access and control lies, and with what effects into the future. 3. Big Brother Watches, So What Are the Alternatives: Whither the Gazing Elite in Dark SOS? By way of conceptual genealogy, consideration of contemporary perceptions of surveillance in a visually networked society (Cinque, Changing Media Landscapes) might be usefully explored through a revisitation of Jeremy Bentham’s panopticon, applied here as a metaphor for contemporary surveillance. Arguably, this is a foundational theoretical model for integrated methods of social control (Foucault, Surveiller et Punir, 192-211), realised in the “panopticon” (prison) in 1787 by Jeremy Bentham (Bentham and Božovič, 29-95) during a period of social reformation aimed at the improvement of the individual. Like the power for social control over the incarcerated in a panopticon, police power, in order that it be effectively exercised, “had to be given the instrument of permanent, exhaustive, omnipresent surveillance, capable of making all visible … like a faceless gaze that transformed the whole social body into a field of perception” (Foucault, Surveiller et Punir, 213–4). In grappling with the impact of SOS for the individual and the collective in post-digital times, we can trace out these early ruminations on the complex documentary organisation through state-controlled apparatuses (such as inspectors and paid observers including “secret agents”) via Foucault (Surveiller et Punir, 214; Subject and Power, 326-7) for comparison to commercial operators like Facebook. Today, artificial intelligence (AI), facial recognition technology (FRT), and closed-circuit television (CCTV) for video surveillance are used for social control of appropriate behaviours. Exemplified by governments and the private sector is the use of combined technologies to maintain social order, from ensuring citizens cross the street only on green lights, to putting rubbish in the correct recycling bin or be publicly shamed, to making cashless payments in stores. The actions see advantages for individual and collective safety, sustainability, and convenience, but also register forms of behaviour and attitudes with predictive capacities. This gives rise to suspicions about a permanent account of individuals’ behaviour over time. Returning to Foucault (Surveiller et Punir, 135), the impact of this finds a dissociation of power from the individual, whereby they become unwittingly impelled into pre-existing social structures, leading to a ‘normalisation’ and acceptance of such systems. If we are talking about the dark, anxiety is key for a Ministry of SOS. Following Foucault again (Subject and Power, 326-7), there is the potential for a crawling, creeping governance that was once distinct but is itself increasingly hidden and growing. A blanket call for some form of ongoing scrutiny of such proliferating powers might be warranted, but with it comes regulation that, while offering certain rights and protections, is not without consequences. For their part, a number of SOS platforms had little to no moderation for explicit content prior to December 2018, and in terms of power, notwithstanding important anxiety connected to arguments that children and the vulnerable need protections from those that would seek to take advantage, this was a crucial aspect of community building and self-expression that resulted in this freedom of expression. In unearthing the extent that individuals are empowered arising from the capacity to post sexual self-images, Tiidenberg ("Bringing Sexy Back") considered that through dark SOS (read here as unregulated) some users could work in opposition to the mainstream consumer culture that provides select and limited representations of bodies and their sexualities. This links directly to Mondin’s exploration of the abundance of queer and feminist pornography on dark SOS as a “counterpolitics of visibility” (288). This work resulted in a reasoned claim that the technological structure of dark SOS created a highly political and affective social space that users valued. What also needs to be underscored is that many users also believed that such a space could not be replicated on other mainstream SOS because of the differences in architecture and social norms. Cho (47) worked with this theory to claim that dark SOS are modern-day examples in a history of queer individuals having to rely on “underground economies of expression and relation”. Discussions such as these complicate what dark SOS might now become in the face of ‘adult’ content moderation and emerging tracking technologies to close sites or locate individuals that transgress social norms. Further, broader questions are raised about how content moderation fits in with the public space conceptualisations of SOS more generally. Increasingly, “there is an app for that” where being able to identify the poster of an image or an author of an unknown text is seen as crucial. While there is presently no standard approach, models for combining instance-based and profile-based features such as SVM for determining authorship attribution are in development, with the result that potentially far less content will remain hidden in the future (Bacciu et al.). 4. There’s Nothing New under the Sun (Ecclesiastes 1:9) For some, “[the] high hopes regarding the positive impact of the Internet and digital participation in civic society have faded” (Schwarzenegger, 99). My participant observation over some years in various SOS, however, finds that critical concern has always existed. Views move along the spectrum of thinking from deep scepticisms (Stoll, Silicon Snake Oil) to wondrous techo-utopian promises (Negroponte, Being Digital). Indeed, concerns about the (then) new technologies of wireless broadcasting can be compared with today’s anxiety over the possible effects of the internet and SOS. Inglis (7) recalls, here, too, were fears that humanity was tampering with some dangerous force; might wireless wave be causing thunderstorms, droughts, floods? Sterility or strokes? Such anxieties soon evaporated; but a sense of mystery might stay longer with evangelists for broadcasting than with a laity who soon took wireless for granted and settled down to enjoy the products of a process they need not understand. As the analogy above makes clear, just as audiences came to use ‘the wireless’ and later the internet regularly, it is reasonable to argue that dark SOS will also gain widespread understanding and find greater acceptance. Dark social spaces are simply the recent development of internet connectivity and communication more broadly. The dark SOS afford choice to be connected beyond mainstream offerings, which some users avoid for their perceived manipulation of content and user both. As part of the wider array of dark web services, the resilience of dark social spaces is reinforced by the proliferation of users as opposed to decentralised replication. Virtual Private Networks (VPNs) can be used for anonymity in parallel to TOR access, but they guarantee only anonymity to the client. A VPN cannot guarantee anonymity to the server or the internet service provider (ISP). While users may use pseudonyms rather than actual names as seen on Facebook and other SOS, users continue to take to the virtual spaces they inhabit their off-line, ‘real’ foibles, problems, and idiosyncrasies (Chenault). To varying degrees, however, people also take their best intentions to their interactions in the dark. The hyper-efficient tools now deployed can intensify this, which is the great advantage attracting some users. In balance, however, in regard to online information access and dissemination, critical examination of what is in the public’s interest, and whether content should be regulated or controlled versus allowing a free flow of information where users self-regulate their online behaviour, is fraught. O’Loughlin (604) was one of the first to claim that there will be voluntary loss through negative liberty or freedom from (freedom from unwanted information or influence) and an increase in positive liberty or freedom to (freedom to read or say anything); hence, freedom from surveillance and interference is a kind of negative liberty, consistent with both libertarianism and liberalism. Conclusion The early adopters of initial iterations of SOS were hopeful and liberal (utopian) in their beliefs about universality and ‘free’ spaces of open communication between like-minded others. 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