Academic literature 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.

AbstractFrom the 1851 Exhibition Scholarship Committee to Pawsey on 1 October 1931:Pawsey started out in research in the midst of excitement over the possibilities of radio communications and the iteratively developing physical understanding of the ionosphere and of the equipment that might be used to investigate it. During 1926–28 he completed his BSc at the University of Melbourne, Victoria. In 1929 he began a Master’s Degree, which was at that time a research-only degree, under the direction of Professor T.H. Laby. He was supported by receiving the M.J. Bartlett Research Scholarship. Presumably this, along with his work as a tutor in Physics at Queens College, provided him with a small, but independent, income. He embarked on a study of “atmospherics”—electrical disturbances in the atmosphere that Appleton, at King’s College, London, and others had linked in part with thunderstorm activity—and their impact on radio broadcasting. From January 1930 to August 1931, he carried out observations using a cathode ray direction finder, working with George H. Munro and Lenard Huxley as part of the Australian Radio Research Board (RRB). Pawsey wrote in 1933: “We were able to give strong evidence that all atmospherics originate in lightning flashes, and made measurements of intensity enabling the distance of the thunderstorms to be roughly determined.” (Ratcliffe & Pawsey, 1933)