The Increasing Surface Ozone and Tropospheric Ozone in Antarctica and Their Possible Drivers.

A comprehensive analysis of the temporal evolution of tropospheric ozone in Antarctica using more than 25 years of surface ozone and ozonesonde measurements reveals significant changes in tropospheric ozone there. It shows a positive trend in ozone at the surface and lower and mid-troposphere, but a negative trend in the upper troposphere. We also find significant links between different climate modes and tropospheric ozone in Antarctica and observe that changes in residual overturning circulation, the strength of the polar vortex, and stratosphere-troposphere exchange make noticeable variability in tropospheric ozone. Therefore, this study alerts of increasing ozone concentration in Antarctica, which would have a profound impact on the future climate of the region as tropospheric ozone has warming feedback to the Earth's climate.

New "Smart" Systems for Atmospheric Aerosol and Reactive Gas Sampling in Ambient Air.

Nowadays a recognized need for accurate observations of atmospheric aerosols (AEs) and reactive gases (RGs) exists in the framework of regional, national and global near-surface networks based on permanent or mobile measurement stations. In this context, a paramount and not-trivial issue is related to the correct execution of continuous sampling of ambient air and its subsequent distribution to measurement analyzers hosted inside the stations. Sampling artifacts must be minimized for obtaining reliable pictures of ambient air composition. To respond to this need, a suite of novel "smart" and relatively low-cost systems for the continuous sampling of ambient air was developed in the framework of the 2012⁻2015 I-AMICA Project. These systems were designed to execute AE and RG measurements according with WMO/GAW and ACTRIS recommendations and standard operation procedures. A particular attention was dedicated to the stabilization and control of the sampling flow rates and temperatures. The analysis of one full year of operations at the WMO/GAW regional station of Capo Granitola (GAW ID: CGR, Italy), allowed to conclude that these systems are effective in meeting the technical requirements for correct execution of AE and RG measurements.

Saharan dust and daily mortality in Emilia-Romagna (Italy).

OBJECTIVE: To investigate the association between Saharan dust outbreaks and natural, cardiovascular and respiratory mortality. METHODS: A case-crossover design was adopted to assess the effects of Saharan dust days (SDD) on mortality in the Emilia-Romagna region of Italy. The population under study consisted of residents in the six main towns of the central-western part of the region who died between August 2002 and December 2006. The association of Saharan dust outbreaks and PM(10) concentration with mortality was estimated using conditional logistic regression, adjusted for apparent temperature, holidays, summer population decrease, flu epidemic weeks and heat wave days. The role of the interaction term between PM(10) and SDD was analysed to test for effect modification induced by SDD on the PM(10)-mortality concentration-response function. Separate estimates were undertaken for hot and cold seasons. RESULTS: We found some evidence of increased respiratory mortality for people aged 75 or older on SDD. Respiratory mortality increased by 22.0% (95% CI 4.0% to 43.1%) on the SDD in the whole year model and by 33.9% (8.4% to 65.4%) in the hot season model. Effects substantially attenuated for natural and cardiovascular mortality with ORs of 1.042 (95% CI 0.992 to 1.095) and 1.043 (95% CI 0.969 to 1.122), respectively. CONCLUSIONS: Our findings suggest an association between respiratory mortality in the elderly and Saharan dust outbreaks. We found no evidence of an effect modification of dust events on the concentration-response relationship between PM(10) and daily deaths. Further work should be carried out to clarify the mechanism of action.

High frequency new particle formation in the Himalayas.

Rising air pollution levels in South Asia will have worldwide environmental consequences. Transport of pollutants from the densely populated regions of India, Pakistan, China, and Nepal to the Himalayas may lead to substantial radiative forcing in South Asia with potential effects on the monsoon circulation and, hence, on regional climate and hydrological cycles, as well as to dramatic impacts on glacier retreat. An improved description of particulate sources is needed to constrain the simulation of future regional climate changes. Here, the first evidence of very frequent new particle formation events occurring up to high altitudes is presented. A 16-month record of aerosol size distribution from the Nepal Climate Observatory at Pyramid (Nepal, 5,079 m above sea level), the highest atmospheric research station, is shown. Aerosol concentrations are driven by intense ultrafine particle events occurring on >35% of the days at the interface between clean tropospheric air and the more polluted air rising from the valleys. During a pilot study, we observed a significant increase of ion cluster concentrations with the onset of new particle formation events. The ion clusters rapidly grew to a 10-nm size within a few hours, confirming, thus, that in situ nucleation takes place up to high altitudes. The initiation of the new particle events coincides with the shift from free tropospheric downslope winds to thermal upslope winds from the valley in the morning hours. The new particle formation events represent a very significant additional source of particles possibly injected into the free troposphere by thermal winds.

Was an Avalanche Swarm Responsible for the Devastation at Mount Everest Base Camp During the April 2015 Nepal Earthquake?

Moore, G.W.K., Paolo Cristofanelli, Paolo Bonasoni, Gian Pietro Verza, and J.L. Semple. Was an avalanche swarm responsible for the devastation at Mount Everest Base Camp during the April 2015 Nepal earthquake? High Alt Med Biol. 21:352-359, 2020. Introduction: An avalanche triggered by an earthquake on April 25, 2015, struck the Mount Everest Base Camp (EBC) resulting in 15 deaths and over 70 injuries. Despite the common occurrence of avalanches in this region, little is known about their intensity and the stability of the glaciers that ring the Mount Everest massif. Here we present unique observations from a nearby automatic weather station (AWS) in the minutes just after the earthquake. Methods: Several (AWS) were deployed along the Khumbu Valley in Nepal. The site at Kala Patthar (elevation 5,613 m asl) 3.5 km from EBC and 4 km from the col along the ridge between Pumori and Lingtren was active from 2010 to 2015 and recorded temperature, relative humidity, pressure, solar radiation, and wind speed and direction. Results: The sequence of wind direction anomalies indicated that multiple air blasts passed the AWS, each associated with a distinct avalanche source, suggesting that earthquake likely caused a number of distinct avalanches from different source regions along this ridge. Discussion: Results suggest that a swarm of avalanches collectively lead to the death and destruction at EBC, suggesting the need for improvement in our understanding of avalanches in the region as well as in our ability to model and forecast such events.

High Concentrations of Ozone Air Pollution on Mount Everest: Health Implications for Sherpa Communities and Mountaineers.

Semple, John L., G.W. Kent Moore, Petros Koutrakis, Jack M. Wolfson, Paolo Cristofanelli, and Paolo Bonasoni. High concentrations of ozone air pollution on Mount Everest: health implications for Sherpa communities and mountaineers. High Alt Med Biol. 17:365-369, 2016.-Introduction: Populations in remote mountain regions are increasingly vulnerable to multiple climate mechanisms that influence levels of air pollution. Few studies have reported on climate-sensitive health outcomes unique to high altitude ecosystems. In this study, we report on the discovery of high-surface ozone concentrations and the potential impact on health outcomes on Mount Everest and the high Himalaya. MATERIALS AND METHODS: Surface ozone measurements were collected during ascending transects in the Mount Everest region of Nepal with passive nitrite-coated Ogawa filter samplers to obtain 8-hour personal exposures (2860-5364 m asl). In addition, the Nepal Climate Observatory-Pyramid, a GAW-WMO Global Station sited in the Khumbu Valley (5079 m asl), collected ozone mixing ratios with photometric gas analyzer. RESULTS: Surface ozone measurements increased with altitude with concentrations that exceed 100 ppb (8-hour exposure). Highest values were during the spring season and the result of diverse contributions: hemispheric background values, the descent of ozone-rich stratospheric air, and the transport of tropospheric pollutants occurring at different spatial scales. DISCUSSION: Multiple climate factors, including descending stratospheric ozone and imported anthropogenic air masses from the Indo-Gangetic Plain, contribute to ambient ozone exposure levels in the vicinity of Mount Everest that are similar to if not higher than those reported in industrialized cities.

Environmental conditions at the South Col of Mount Everest and their impact on hypoxia and hypothermia experienced by mountaineers.

BACKGROUND: Hypoxia and hypothermia are acknowledged risk factors for those who venture into high-altitude regions. There is, however, little in situ data that can be used to quantify these risks. Here, we use 7 months of continuous meteorological data collected at the South Col of Mount Everest (elevation 7,896 m above sea level) to provide the first in situ characterization of these risks near the summit of Mount Everest. METHODS: This is accomplished through the analysis of barometric pressure, temperature and wind speed data collected by an automatic weather station installed at the South Col. These data were also used as inputs to parameterizations of wind chill equivalent temperature (WCT) and facial frostbite time (FFT). RESULTS: The meteorological data show clear evidence of seasonality, with evidence of pre-monsoon, monsoon and post-monsoon conditions. Low pressures, cold temperatures and high wind speeds characterize the pre- and post-monsoon periods with significant variability associated with the passage of large-scale weather systems. In contrast, the monsoon period is characterized by higher pressures, warmer temperatures and lower wind speeds with a pronounced reduction in variability. These environmental conditions are reflected in WCTs as low as -50°C and FFTs as short as 2 min during the pre- and post-monsoon periods. During the monsoon, the risk of cold injury is reduced with WCTs of order -20°C and FFTs longer than 60 min. The daily cycle in the various parameters is also investigated in order to assess the changes in conditions that would be experienced during a typical summit day. The post-monsoon period in particular shows a muted daily cycle in most parameters that is proposed to be the result of the random timing of large-scale weather systems. CONCLUSIONS: Our results provide the first in situ characterization of the risk of hypoxia and hypothermia on Mount Everest on daily, weekly and seasonal timescales, and provide additional confirmation as to the extreme environment experienced by those attempting to summit Mount Everest and other high Himalayan mountains.

Background ozone in the southern Europe and Mediterranean area: influence of the transport processes.

The troposphere is subject to continuous inputs, production and removal processes of ozone and its precursors from natural processes and human activities acting together within a very complex system. In order to assess the behaviour of background ozone in the Mediterranean area, a description of trends, seasonal and diurnal behaviours of free tropospheric ozone is provided. In the Mediterranean area and southern Europe the background tropospheric ozone concentration appears significantly affected by three main air mass transport processes: (i) transport of polluted air masses on regional and long-range scales, (ii) downward transport of stratospheric air masses, and (iii) transport of mineral dust from the Sahara desert. In this review of the literature of the last two decades, we present an overview of these phenomena, mainly monitored at high baseline mountain stations representative of background atmospheric conditions.