Airborne bacterial populations above desert soils of the McMurdo Dry Valleys, Antarctica

Bacteria are assumed to disperse widely via aerosolized transport due to their small size and resilience. The question of microbial endemicity in isolated populations is directly related to the level of airborne exogenous inputs, yet this has proven hard to identify. The ice-free terrestrial ecosystem of Antarctica, a geographically and climatically isolated continent, was used to interrogate microbial bio-aerosols in relation to the surrounding ecology and climate. High-throughput sequencing of bacterial ribosomal RNA (rRNA) genes was combined with analyses of climate patterns during an austral summer. In general terms, the aerosols were dominated by Firmicutes, whereas surrounding soils supported Actinobacteria-dominated communities. The most abundant taxa were also common to aerosols from other continents, suggesting that a distinct bio-aerosol community is widely dispersed. No evidence for significant marine input to bio-aerosols was found at this maritime valley site, instead local influence was largely from nearby volcanic sources. Back trajectory analysis revealed transport of incoming regional air masses across the Antarctic Plateau, and this is envisaged as a strong selective force. It is postulated that local soil microbial dispersal occurs largely via stochastic mobilization of mineral soil particulates

Discovery of Sclerotinia sclerotiorum Hypovirulence-Associated Virus-1 in Urban River Sediments of Heathcote and Styx Rivers in Christchurch City, New Zealand

In samples of benthic and bank river sediments of two urban rivers in Christchurch city (New Zealand), we identified and recovered isolates of Sclerotinia sclerotiorum hypovirulence-associated virus-1 (SsHADV-1), a fungus-infecting circular single-stranded DNA virus. This is the first report of SsHADV-1 outside of China and in environmental samples

Identifying hydro-meteorological events from precipitation extremes indices and other sources over northern Namibia, Cuvelai Basin

Worldwide, more than 40% of all natural hazards and about half of all deaths are the result of flood disasters. In northern Namibia flood disasters have increased dramatically over the past half-century, along with associated economic losses and fatalities. There is a growing concern to identify these extreme precipitation events that result in many hydro-meteorological disasters. This study presents an up to date and broad analysis of the trends of hydrometeorological events using extreme daily precipitation indices, daily precipitation data from the Grootfontein rainfall station (1917–present), regionally averaged climatologies from the gauged gridded Climate Research Unit (CRU) product, archived disasters by global disaster databases, published disaster events in literature as well as events listed by Mendelsohn, Jarvis and Robertson (2013) for the data-sparse Cuvelai river basin (CRB). The listed events that have many missing data gaps were used to reference and validate results obtained from other sources in this study. A suite of ten climate change extreme precipitation indices derived from daily precipitation data (Grootfontein rainfall station), were calculated and analysed. The results in this study highlighted years that had major hydro-meteorological events during periods where no data are available. Furthermore, the results underlined decrease in both the annual precipitation as well as the annual total wet days of precipitation, whilst it found increases in the longest annual dry spell indicating more extreme dry seasons. These findings can help to improve flood risk management policies by providing timely information on historic hydro-meteorological hazard events that are essential for early warning and forecasting

Fire weather of a Canterbury Northwester on 6 February 2011 in South Island, New Zealand

Foehn winds, known locally as the "Canterbury Northwester", occurred on 6 February 2011 and were associated with extreme fire weather in the lee of the Southern Alps and across the eastern South Island of New Zealand. A peak air temperature of 40.7˚C was recorded at Timaru, which compares with the national record of 42.4˚C set at Rangiora in 1973 during another Northwester. The primary objective of this study was to investigate the fire weather and the synoptic and mesoscale atmospheric processes associated with the Northwester. This was achieved through analysis of weather station data and a high-resolution Weather Research and Forecasting (WRF) model simulation. The fire weather was assessed through consideration of observable weather variables and New Zealand's version of the Fire Weather Index (FWI) in the Canadian Forest Fire Danger Rating System. The WRF model results suggest that internal gravity waves were present in the lee of the Southern Alps and considerably affected fire weather across the eastern South Island. The FWI was recorded at extreme values, due to a combination of high air temperatures and wind speeds, and low relative humidity. This study provides a better understanding of the mesoscale atmospheric dynamics and fire weather associated with the Canterbury Northwester

The influence of atmospheric circulation patterns during large snowfall events in New Zealand's Southern Alps

Large snowfall events contribute significantly to total annual snow accumulation across the maritime Southern Alps. However, the knowledge about atmospheric circulation patterns associated with large snowfall events over the New Zealand Southern Alps is very limited. Daily snow observation data from three automatic weather stations and ERA-Interim reanalysis data were used to investigate the relationship between atmospheric forcing and large snowfall events across the Southern Alps. To do so, analysis of composite anomaly maps during large snowfall events were carried out to identify the common features of the days with heavy snow accumulation. Large snowfall across the Southern Alps are mainly associated with strong negative anomalies of sea level pressure (SLP) located over the southwest of New Zealand’s South Island. These conditions are concurrent with negative anomalies of geopotential heights at 500 (Z500) located in the centre of low pressure systems. However, over New Zealand, days leading to large snowfall events experience positive anomalies of Z500 showing a relatively warm environment during such events in the maritime Southern Alps. Positive anomalies of low-tropospheric temperatures (850 hPa and 1000 hPa) over the Tasman Sea and across the Southern Alps, strong values of integrated vapour transport (IVT) as well as high frequency of local synoptic patterns associated with troughing regimes (~78%) during large snowfall events provide more evidence of the important contribution of warm air flows

Moisture Transport during Large Snowfall Events in the New Zealand Southern Alps: The Role of Atmospheric Rivers

Synoptic-scale moisture transport during large snowfall events in the New Zealand Southern Alps is largely unknown due to a lack of long-term snow observations. In this study, records from three recently developed automatic weather stations (Mahanga, Mueller Hut, and Mt Larkins) near the Main Divide of the Southern Alps were used to identify large snowfall events between 2010 and 2018. The large snowfall events are defined as those events with daily snow depth increase by greater than the 90th percentile at each site. ERA-Interim reanalysis data were used to characterize the hydrometeorological features of the selected events. Our findings show that large snowfall events in the Southern Alps generally coincide with strong fields of integrated vapor transport (IVT) within a northwesterly airflow and concomitant deepening low pressure systems. Considering the frequency of large snowfall events, approximately 61% of such events at Mahanga were associated with narrow corridors of strong water vapor flux, known as atmospheric rivers (ARs). The contributions of ARs to the large snowfall events at Mueller Hut and Mt Larkins were 70% and 71%, respectively. Analysis of the vertical profiles of moisture transport dynamics during the passage of a landfalling AR during 11–12 October 2016 revealed the key characteristics of a snow-generating AR in the Southern Alps. An enhanced presence of low- and midlevel moisture between 700 and 850 hPa and pronounced increases of wind velocities (more than 30 m s−1with high values of the meridional component between 750 and 850 hPa were identified over the Southern Alps during the event