Frequency Of Air Masses Research Articles

Статистический анализ конвективных процессов над Апшеронским полуостровом

This paper is focuses on to determine the air masses observed during convective processes in Baku and the Absheron Peninsula in 2011-2020. As well as to identify the frequency of air masses and atmospheric phenomena by seasons and years. The purpose of this study is to determine weather phenomena that is significantly influence the safety and the operational activity of air traffic, particularly, in the areas of the aerodrome and route. The formation of thunderstorms is a particularly important meteorological event that has major relevance to aviation safety. Despite all the safety improvements, the weather is still today a major cause of aviation accidents and incidents. According to the International Civil Aviation Organization (ICAO) statistics, 15-20 % of plane crashes are caused by severe weather conditions. Hazards associated with convective weather include thunderstorms with severe turbulence, intense up- and downdrafts, lightning, hail, heavy precipitation, icing, wind shear, microbursts and strong low-level winds. As a source of the information regular observations of Heydar Aliyev International Airport, also soundings, satellite images, surface and upper air maps were used.

Changes in the frequency and temperature of air masses over east‐central Europe

AbstractThe study specifies the circulation conditions, the frequency of occurrence, long‐term changes, and thermal characteristics of air masses over east‐central Europe in the years 1951–2020. The division of air masses utilized by The Polish Institute of Meteorology and Water Management was used, where, based on the geographical location of the source areas, Arctic (A), Polar maritime fresh (mPf), Polar maritime old (transformed) (mPo), Polar maritime warm (mPw), Polar continental (cP), and Tropical (T) air masses are distinguished. It has been shown that western circulation dominates in this area (60% of days on average), during which the advection of maritime air masses occurs. The share of Arctic air mass flowing from the north (about 12% of days a year) and Tropical air mass from the southern sector (4% of days) is clearly smaller. The results of the research have shown that the frequency of the majority of the analysed air masses was subject to short‐term changes in the studied period. On the other hand, long‐term changes in this frequency concerned two air masses flowing from lower latitudes (mPw and T). In the case of mPw, in the period 1951–2020 there was a significant increase in frequency, not only on a yearly basis, but also in all seasons. In the last two decades, the frequency of Tropical air mass has also increased significantly, while the increase took place only in the summer period. Therefore, the increase in air temperature recorded in east‐central Europe since the 1990s, mainly in the warm half of the year, should to a large extent be attributed to both the greater frequency of the inflow of air masses from lower latitudes (mPw and T) and the increase in temperature in virtually all separated air masses, which in turn is a result of progressing global warming.

Analysis of convective processes for the Absheron Peninsula

This paper is focuses on to determine the air masses observed during convective processes in Baku and the Absheron Peninsula in 2011-2020. As well as to identify the frequency of air masses and atmospheric phenomena by seasons and years. The purpose of this study is to determine weather phenomena, which is significantly, influence the safety and the operational activity of air traffic, particularly, in the areas of the aerodrome and route. The formation of thunderstorms is a particularly important meteorological event that has major relevance to aviation safety. Despite all the safety improvements, the weather is still today a major cause of aviation accidents and incidents. According to the International Civil Aviation Organization (ICAO) statistics, 15 -20% of plane crashes are caused by severe weather conditions. Hazards associated with convective weather include thunderstorms with severe turbulence, intense up- and downdrafts, lightning, hail, heavy precipitation, icing, wind shear, microbursts and strong low-level winds. As a source of the information regular observations of Heydar Aliyev International Airport, also soundings, satellite images, surface and upper air maps were used.

Trends in air mass frequencies across Europe

Trends in air mass frequencies across Europe

A high-resolution pollen and diatom record of mid-to late-Eemian at Kozłów (Central Poland) reveals no drastic climate changes in the hornbeam phase of this interglacial

In the region of 20 newly-found fossil lakes in the Garwolin Plain (Central Poland), formed during the Eemian interglacial (MIS 5e), the Kozłów site is considered one of the longest examples of sequences of palaeolake deposits. Pollen investigations have revealed an entire Eemian interglacial (MIS 5e) with a very long hornbeam phase. Repeated coring allowed for high-resolution pollen and diatom analysis to be used in tracing climate-driven palaeoenvironmental changes during the mid- and late-Eemian. The resulting thick series of organogenic deposits from Kozłów joins the collection of existing high-resolution long records of this interglacial in central-eastern Europe. It should be emphasized that a very good correlation was found between palynological and diatom data, which allows for drawing consistent conclusions. The warm and humid climate of the Corylus phase at the onset of the mid-Eemian was marked by a great abundance of planktonic Cyclotella sensu lato species, which indicate a rising water level, increased water temperatures, thermal stratification and a warm-wet climate. In the diatom zones correlated with the Carpinus phase, a distinct change was observed, from an assemblage dominated by planktonic species to one composed of benthic ones, including Fragilaria sensu lato taxa. The greater frequency of oceanic air masses must have affected the humidity and thermal conditions in lake and its surroundings in the first part of the interglacial optimum. Climate changes are very clearly visible at the transition between Carpinus and Picea-Abies zones, which were caused by increased influence of continental air masses. However, in the Middle Eemian no drastic changes were observed in both the pollen and diatom records.In the upper part of the core, represented by Pinus pollen, the presence of cold-loving diatom species, and an increase of green algae Pediastrum spp. point to a drop in temperatures at the close of the interglacial. The pollen results were compared to the well-recognized mid-to late-Eemian successions from Poland and West Europe.

Mediterranean contemporary winter and summer air mass climatology with respect to temperature and moisture flux

Large-scale moisture fluxes and backward air mass trajectories and frequencies were investigated to explain the mechanisms of synoptic-scale seasonal variability of air masses in the Mediterranean basin. For this aim, reanalysis data were used to calculate variations in moisture flux with respect to temperature and stability according to the 8 standard pressure levels between 1000 and 300 hPa. Investigating air mass characteristics changing with pressure levels provided new information in terms of air mass climatology for the Mediterranean basin. Results show that due to the influence of westerly flows, the Atlantic is the main source of moisture higher than 700 hPa. Turbulent transport of moisture from the Mediterranean Sea is the source of moisture close to the surface, which corresponds to levels lower than 700 hPa. According to the trajectory analysis, the continental Arctic (cA) air mass can reach the Mediterranean basin and provide very wet conditions over the Mediterranean basin during winter. In addition, during very dry conditions in summer, all air mass currents originate from surface pressure levels between 1000 and 850 hPa. These relatively warm and dominant air masses cause cloud-free conditions with very low precipitation over the Mediterranean basin. This study showed that air masses should be analyzed not only according to their source and path but also according to pressure levels. Therefore, more studies are needed investigating the contemporary air mass climatology of a specific region.

Trends and Variability in Airmass Frequencies: Indicators of a Changing Climate

AbstractRecent international efforts at communicating climate change have begun using the notion of a climate indicator—a climate-related metric that can be used to track changes in the Earth system over time. Based upon a recently developed global-scale classification of daily air masses, this research examines the trends and variability in the frequencies of these air masses and then utilizes them to develop two nontraditional climate indicators: a warm/cool index (WCI) and a global extremes index (GEI). Results show that both indices trend significantly upward over the 40-yr period of record, indicating an increase in warm-based air masses (WCI) and extreme air masses (GEI). The two indices also exhibit a moderate (GEI) to strong (WCI) association with the global mean temperature record, multiple near-surface climate variables, and other existing climate indicators over that same time, showing promise as global indicators. Shorter-term variability in these indices also show a linear relationship between the WCI and changes in the Atlantic multidecadal oscillation and a nonlinear relationship between GEI and El Niño–Southern Oscillation. While many published climate indicators are based upon a single variable, and/or are regional in scope, the two indices presented herein are unique in that they are representative of the trends in the multivariate (and extreme, in the case of the GEI) weather conditions that are experienced near Earth’s surface, while also being global in scope.

Atmospheric Deposition of Organochlorine Pesticides and Industrial Compounds to Seasonal Surface Snow at Four Glacier Sites on Svalbard, 2013-2014.

Winter snow from four glacial sites on Svalbard was analyzed for atmospheric deposition of 36 organochlorine pesticides (OCPs) and 7 industrial compounds (OCICs) by GC-high-resolution MS. Thirteen of the OCPs and all OCICs were detected at all sites. Sampling sites are 230 km apart from west to east, but are at varying elevations, ranging from 700 to 1202 m a.s.l. Total OCP flux was greater than total OCIC at all sites and was 5 times greater at Lomonosovfonna, and 3 times greater at Austfonna, the most easterly site. Chlorpyrifos dominated OCP flux at Lomonosovfonna (81.7 pg cm-2 yr-1) and Kongsvegen (60.6 pg cm-2 yr-1), and at Austfonna, but not at Holtedahlfonna where dieldrin dominated. trans-chlordane was a major contributor to OCPs. These three pesticides comprised at least 50% of total OCP at each site. OCIC flux was dominated by pentachloroanisole (PCA) at Lomonosovfonna (23.5 pg cm-2 yr-1) and Kongsvegen (14.1 pg cm-2 yr-1). PCA and hexachlorobenzene comprised at least 63% of all OCICs at each site. Air mass frequency from likely source areas showed that Austfonna had the most frequent long-distance air flow, but showed lower amounts of chlorpyrifos and PCA, suggesting local sources of these compounds to other sites.

Comparing daily temperature averaging methods: the role of synoptic climatology in determining spatial and seasonal variability

ABSTRACTThe two primary methods for averaging daily near-surface air temperature are twice-daily averaging (i.e., the sum of the maximum and minimum divided by two) and hourly averaging (i.e., using the 24 hourly values of a day). To quantify the influence of synoptic (air mass) climatology on the numerical difference between the two types of daily temperature averaging, a synoptic climatology for 215 weather stations across the Contiguous United States (CONUS) was developed for the period 1981–2010 and then correlated with those difference values. A significant correlation is found between air mass frequency and the temperature difference, especially during the non-transition seasons (i.e., summer and winter). This pattern is due to the influence of air mass type on the shape of the daily temperature curve. The correlation results also show spatial variability, as air masses that are more frequent in the northern CONUS (e.g., Dry Polar) influence the diurnal temperature curve differently than air masses more common in the southern CONUS (e.g., Moist Tropical). Future work can capitalize on these results by investigating different geographic regions and utilizing this correlation-based approach to analyze how anticipated future changes in the synoptic climatology of air masses influence the diurnal temperature curve.

Synoptyczne uwarunkowania napływu mas powietrza polarnego nad Lubelszczyznę

<p>Celem opracowania jest charakterystyka częstości i uwarunkowań synoptycznych napływu mas powietrza polarnego nad obszar Lubelszczyzny. Ich występowanie w ujęciu regionalnym określono dla godziny 12 UTC na podstawie dolnych map synoptycznych PIHM/IMGW-PIB z okresu 1951–2010. Częstość napływu mas powietrza polarnego (morskiego „świeżego” – PPm, morskiego starego – PPms, morskiego ciepłego – PPmc i kontynentalnego – PPk) w ciągu roku wynosiła 82,5%. Spośród wyróżnionych typów mas powietrza najczęściej notowano powietrze polarne morskie stare (PPms), z częstością przekraczającą 37% (maksimum w lecie, minimum wiosną). W latach 1951–2010 zaznaczyły się istotne zmiany w częstości napływu nad Lubelszczyznę mas PPk (spadek średnio o 11 dni na 10 lat), PPm (spadek 7 dni na 10 lat) i PPmc (wzrost o blisko 11 dni na 10 lat). We wszystkich porach roku masy PPms najczęściej napływały nad Lubelszczyznę z zachodu, PPmc z południowego zachodu i zachodu, PPm z zachodu i północo-zachodu, a PPk ze wschodu i południowego wschodu.</p>

Synoptyczne uwarunkowania napływu mas powietrza arktycznego i zwrotnikowego nad Lubelszczyznę

<p>Celem opracowania jest charakterystyka częstości i uwarunkowań synoptycznych napływu mas powietrza arktycznego i zwrotnikowego nad obszar Lubelszczyzny. Ich występowanie w ujęciu regionalnym określono dla godziny 12 UTC na podstawie dolnych map synoptycznych PIHM/IMGW z okresu 1951-2010. Do oceny uwarunkowań synoptycznych napływu analizowanych mas powietrza wykorzystano kalendarz typów cyrkulacji dla Lubelszczyzny. Częstość napływu mas powietrza arktycznego w ciągu roku wynosiła 13,4%. Największy udział tych mas występuje wiosną, z maksimum w kwietniu (20,4%), najmniejszy zaś latem (w lipcu i sierpniu poniżej 5%). Rzadziej notuje się napływ powietrza zwrotnikowego (4,1% wszystkich dni w roku). Najczęściej nad Lubelszczyzną występuje ono w lecie (z maksimum w lipcu – 9,2%), natomiast najrzadziej w zimie (< 1%). W latach 1951-2010 zaznaczyły się istotne zmiany w częstości napływu nad Lubelszczyznę mas arktycznych (wzrost średnio o 8 dni na 10 lat) i zwrotnikowych (wzrost o blisko 3 dni na 10 lat). Udział mas arktycznych zwiększył się w zimie, jesieni i na wiosnę, mas zwrotnikowych zaś w lecie. We wszystkich porach roku największe prawdopodobieństwo występowania powietrza arktycznego notowano podczas typów cyrkulacji ze składową północną i północno-wschodnią, najmniejsze zaś w typach warunkujących adwekcję powietrza z południa i południo-zachodu. W przypadku powietrza zwrotnikowego największe prawdopodobieństwo jego wystąpienia notuje się podczas napływu powietrza z kierunków E-SE-S-SW. Niezależnie od pory roku, podczas występowania powietrza arktycznego i zwrotnikowego wykazano występowanie wyraźnych anomalii, zarówno temperatury powietrza na powierzchni izobarycznej 850 hPa, jak i średniej grubości warstwy powietrza między powierzchnią izobaryczną 850 i 1000 hPa.</p>

Long-term trends of surface ozone and its influencing factors at the Mt Waliguan GAW station, China – Part 2: The roles of anthropogenic emissions and climate variability

Abstract. Inter-annual variability and long-term trends in tropospheric ozone are both environmental and climate concerns. Ozone measured at Mt Waliguan Observatory (WLG, 3816 m a.s.l.) on the Tibetan Plateau over the period of 1994–2013 has increased significantly by 0.2–0.3 ppbv yr−1 during spring and autumn but shows a much smaller trend in winter and no significant trend in summer. Here we explore the factors driving the observed ozone changes at WLG using backward trajectory analysis, chemistry–climate model hindcast simulations (GFDL AM3), a trajectory-mapped ozonesonde data set, and several climate indices. A stratospheric ozone tracer implemented in GFDL AM3 indicates that stratosphere-to-troposphere transport (STT) can explain ∼ 60 % of the simulated springtime ozone increase at WLG, consistent with an increase in the NW air-mass frequency inferred from the trajectory analysis. Enhanced STT associated with the strengthening of the mid-latitude jet stream contributes to the observed high ozone anomalies at WLG during the springs of 1999 and 2012. During autumn, observations at WLG are more heavily influenced by polluted air masses originating from South East Asia than in the other seasons. Rising Asian anthropogenic emissions of ozone precursors are the key driver of increasing autumnal ozone observed at WLG, as supported by the GFDL AM3 model with time-varying emissions, which captures the observed ozone increase (0.26 ± 0.11 ppbv yr−1). AM3 simulates a greater ozone increase of 0.38 ± 0.11 ppbv yr−1 at WLG in autumn under conditions with strong transport from South East Asia and shows no significant ozone trend in autumn when anthropogenic emissions are held constant in time. During summer, WLG is mostly influenced by easterly air masses, but these trajectories do not extend to the polluted regions of eastern China and have decreased significantly over the last 2 decades, which likely explains why summertime ozone measured at WLG shows no significant trend despite ozone increases in eastern China. Analysis of the Trajectory-mapped Ozonesonde data set for the Stratosphere and Troposphere (TOST) and trajectory residence time reveals increases in direct ozone transport from the eastern sector during autumn, which adds to the autumnal ozone increase. We further examine the links of ozone variability at WLG to the quasi-biennial oscillation (QBO), the East Asian summer monsoon (EASM), and the sunspot cycle. Our results suggest that the 2–3-, 3–7-, and 11-year periodicities are linked to the QBO, EASM index, and sunspot cycle, respectively. A multivariate regression analysis is performed to quantify the relative contributions of various factors to surface ozone concentrations at WLG. Through an observational and modelling analysis, this study demonstrates the complex relationships between surface ozone at remote locations and its dynamical and chemical influencing factors.

Characterising fifteen years of continuous atmospheric radon activity observations at Cape Point (South Africa)

This paper describes and discusses fifteen years (1999–2013) of continuous hourly atmospheric radon (222Rn) monitoring at the coastal low-altitude Southern Hemisphere Cape Point Station in South Africa. A strong seasonal cycle is evident in the observed radon concentrations, with maxima during the winter months, when air masses arriving at the Cape Point station from over the African continental surface are more frequently observed, and minima during the summer months, when an oceanic fetch is predominant. An atmospheric mean radon activity concentration of 676 ± 2 mBq/m3 is found over the 15-year record, having a strongly skewed distribution that exhibits a large number of events falling into a compact range of low values (corresponding to oceanic air masses), and a smaller number of events with high radon values spread over a wide range (corresponding to continental air masses). The mean radon concentration from continental air masses (1 004 ± 6 mBq/m3) is about two times higher compared to oceanic air masses (479 ± 3 mBq/m3). The number of atmospheric radon events observed is strongly dependent on the wind direction. A power spectral Fast Fourier Transform analysis of the 15-year radon time series reveals prominent peaks at semi-diurnal, diurnal and annual timescales. Two inter-annual radon periodicities have been established, the diurnal 0.98 ± 0.04 day−1 and half-diurnal 2.07 ± 0.15 day−1. The annual peak reflects major seasonal changes in the patterns of offshore versus onshore flow associated with regional/hemispheric circulation patterns, whereas the diurnal and semi-diurnal peaks together reflect the influence of local nocturnal radon build-up over land, and the interplay between mesoscale sea/land breezes. The winter-time diurnal radon concentration had a significant decrease of about 200 mBq/m3 (17%) while the summer-time diurnal radon concentration revealed nearly no changes. A slow decline in the higher radon percentiles (75th and 95th) for the winter and spring seasons is found over the 15-year data set, with most of the change occurring in the first 9 years (1999–2007). This observed inter-annual decline appears to be associated with changes in the frequency of air masses having originated from over the African continental surfaces, and no significant trend is found in the lower radon percentiles associated with oceanic air masses. The general decrease of atmospheric radon-associated with continental air-masses at Cape Point could be attributed to changing meteorological conditions, possibly driven by climate change.

Black carbon radiative forcing derived from AERONET measurements and models over an urban location in the southeastern Iberian Peninsula

This paper provides an account of observed variations in Black carbon (BC) aerosol concentrations and their induced radiative forcing for the first time over Granada a measurement site in Southeastern Iberian Peninsula. Column-integrated BC concentrations were retrieved for the period 2005–2012. Monthly averages of BC concentrations (± one standard deviation) ranged from higher values in January and December with 4.0±2.5 and 4±3mg/m2, respectively, to lower values in July and August with 1.6±1.2 and 2.0±0.5mg/m2, respectively. This reduction is not only observed in the average values, but also in the median, third and first quartiles. The average BC concentration in winter (3.8±0.6mg/m2) was substantially higher than in summer (1.9±0.3mg/m2), being the eight-year average of 2.9±0.9mg/m2. The reduction in the use of fossil fuels during the economic crisis contributed significantly to reduced atmospheric loadings of BC. According to our analysis this situation persisted until 2010. BC concentration values were analyzed in terms of air mass influence using cluster analysis. BC concentrations for cluster 1 (local and regional areas) showed high correlations with air masses frequency in winter and autumn. In these seasons BC sources were related to the intense road traffic and increased BC emissions from domestic heating. High BC concentrations were found in autumn just when air mass frequencies for cluster 3 (Mediterranean region) were more elevated, suggesting that air masses coming from that area transport biomass burning particles towards Granada. BC aerosol optical properties were retrieved from BC fraction using aerosol AERONET size volume distribution and Mie theory. A radiative transfer model (SBDART) was used to estimate the aerosol radiative forcing separately for composite aerosol (total aerosols) and exclusively for BC aerosols. The mean radiative forcing for composite aerosol was +23±6W/m2 (heating rate of +0.21±0.06K/day) and +15±6W/m2 for BC aerosol (heating rate of +0.15±0.06K/day). These values of radiative forcing and heating rate for BC aerosol represent about 70% of their values for composite aerosol, which highlights the crucial role that BC aerosols play in modifying the radiation budget and climate.

Thermal Stratification in Simulations of Warm Climates: A Climatology Using Saturation Potential Vorticity

Abstract The spatial and temporal distribution of stable and convectively neutral air masses is examined in climate simulations with carbon dioxide levels spanning from modern-day values to very high levels that produce surface temperatures relevant to the hottest climate of the past 65 million years. To investigate how stability with respect to slantwise and upright moist convection changes across a wide range of climate states, the condition of moist convective neutrality in climate experiments is assessed using metrics based upon the saturation of potential vorticity, which is zero when temperature profiles are moist adiabatic profiles along vortex lines. The modern climate experiment reproduces previously reported properties from reanalysis data, in which convectively neutral air masses are common in the tropics and locally at higher latitudes, especially over midlatitude continents in summer and ocean storm tracks in winter. The frequency and coverage of air masses with higher stabilities declines in all seasons at higher latitudes with warming; the hottest case features convectively neutral air masses in the Arctic a majority of the time in January and nearly universally in July. The contribution from slantwise convective motions (as distinct from upright convection) is generally small outside of midlatitude storm tracks, and it declines in the warmer climate experiments, especially during summer. These findings support the conjecture that moist adiabatic lapse rates become more widespread in warmer climates, providing a physical basis for using this assumption in estimating paleoaltimetry during warm intervals such as the early Eocene.

Application of spatial synoptic classification in evaluating links between heat stress and cardiovascular mortality and morbidity in Prague, Czech Republic

Spatial synoptic classification (SSC) is here first employed in assessing heat-related mortality and morbidity in Central Europe. It is applied for examining links between weather patterns and cardiovascular (CVD) mortality and morbidity in an extended summer season (16 May-15 September) during 1994-2009. As in previous studies, two SSC air masses (AMs)-dry tropical (DT) and moist tropical (MT)-are associated with significant excess CVD mortality in Prague, while effects on CVD hospital admissions are small and insignificant. Excess mortality for ischaemic heart diseases is more strongly associated with DT, while MT has adverse effect especially on cerebrovascular mortality. Links between the oppressive AMs and excess mortality relate also to conditions on previous days, as DT and MT occur in typical sequences. The highest CVD mortality deviations are found 1day after a hot spell's onset, when temperature as well as frequency of the oppressive AMs are highest. Following this peak is typically DT- to MT-like weather transition, characterized by decrease in temperature and increase in humidity. The transition between upward (DT) and downward (MT) phases is associated with the largest excess CVD mortality, and the change contributes to the increased and more lagged effects on cerebrovascular mortality. The study highlights the importance of critically evaluating SSC's applicability and benefits within warning systems relative to other synoptic and epidemiological approaches. Only a subset of days with the oppressive AMs is associated with excess mortality, and regression models accounting for possible meteorological and other factors explain little of the mortality variance.

Aerosol extinction properties over coastal West Bengal Gangetic plain under inter-seasonal and sea breeze influenced transport processes

We analysed the atmospheric aerosol extinction properties under an influence of inter-seasonal and sea breeze (SB) transport processes over coastal West Bengal (WB) Gangetic plain (WBGP). The predominant frequency of airmass back trajectory path was through the Arabian Sea (AS) during southwest monsoon (SWmon) and that through the Indo-Gangetic plain (IGP) during transition to winter (Twin) season and the Bay of Bengal during transition to summer (Tsumm) season. Aerosol surface concentration (Sconc) and aerosol extinction exhibited heterogeneity in the seasonal variability over coastal WBGP with their highest seasonal mean being during winter and summer seasons respectively. Seasonal mean extinction was respectively 17% and 30% higher during winter and summer seasons than that during SWmon. While angstrom exponent (AE) was less than one during SWmon, Tsumm, and summer seasons, it was near to one during Twin and winter monsoon (Wmon), and was more than one during winter season. Relative contribution (%) of upper (at altitude above 1km) aerosol layer (UAL) to aerosol extinction during summer was four times of that during winter. Seasonally distinct vertical distribution of aerosol extinction associated with meteorological and SB influenced transport and that due to influence of high rise open burning emissions was inferred. Possible aerosol subtypes extracted during days in Tsumm were inferred to be mostly constituted of dust and polluted dust during daytime, in addition to polluted continental and smoke in UAL during nighttime. In contrast to that at nearby urban location (Kolkata, KOL), intensity of updraft of airmass evaluated during evening/SB activity hour (1730 local time, (LT)) at study site (Kharagpur, KGP) was as high as 3.5 times the intensity during near to noon hour (1130 LT); this intensity was the highest along coast of westBengal-Orissa. Enhanced Sconc and relative contribution of UAL to aerosol extinction (58% compared to 36% only at nearby urban location) was inferred associated with SB activity.

Climate context of the cold summer of 2014 in Toronto, ON, Canada

Toronto, Ontario, Canada, experienced a cooler summer in 2014, in spite of worldwide record temperatures. In this work, we assess the relative coldness of summer 2014 from a climatological perspective. Using historical temperature data and several thermal metrics, summer 2014 was ranked using three time periods, 1840–2014 (175 years), the full extent of the local instrumental data; 1965–2014, the most recent 50 years; and 1985–2014, the most recent 30 years. For each of the periods, rank within the time period, recurrence interval and average temperature were calculated. Summer of 2014 in Toronto was ranked 118th since 1840 (175 years of data) using the mean daily temperature. The summer of 2014 with an average mean temperature of 20.8 °C was not extreme in nature and is in fact warmer than the average temperature of the time period (19.9 °C). For the more recent time periods, however, the summer was cooler than average but not an extremely cold summer. A monthly analysis showed in particular a cooler July compared to June and August, ranking July 2014 as the 4th coldest July since 1985 whereas June and August were 21st and 10th coldest during the 30-year period, respectively. Recurrence rates did not exceeded 5 years for the seasonal data and 8.3 years for the monthly data. Although the summer of 2014 was cooler than some recent summers, it was not an extreme event such as the Mount Pinatubo-induced cool summer of 1992 which it was explicitly compared to. Finally, an air mass analysis showed that the cooler July of 2014 was the result of a reduced frequency of warm air masses compared to 1992 when there was both a reduction of warm air masses and an increase in colder ones.

Air mass distribution and the heterogeneity of the climate change signal in the Hudson Bay/Foxe Basin region, Canada

The linkage between changes in air mass distribution and temperature trends from 1971 to 2010 is explored in the Hudson Bay/Foxe Basin region. Statistically significant temperature increases were found of varying spatial and temporal magnitude. Concurrent statistically significant changes in air mass frequency at the same locations were also detected, particularly in the declining frequency of dry polar (DP) air. These two sets of changes were found to be linked, and we thus conclude that the heterogeneity of the climatic warming signal in the region is at least partially the result of a fundamental shift in the concurrent air mass frequency in addition to global and regional changes in radiative forcing due to increases in long-lived greenhouse gases.

Airborne mineral components and trace metals in Paris region: spatial and temporal variability.

A variety of mineral components (Al, Fe) and trace metals (V, Cr, Mn, Ni, Cu, Zn, Cd, Pb) were simultaneously measured in PM2.5 and PM10 fractions at three different locations (traffic, urban, and suburban) in the Greater Paris Area (GPA) on a daily basis throughout a year. Mineral species and trace metal levels measured in both fractions are in agreement with those reported in the literature and below the thresholds defined by the European guidelines for toxic metals (Cd, Ni, Pb). Size distribution between PM2.5 and PM10 fractions revealed that mineral components prevail in the coarse mode, while trace metals are mainly confined in the fine one. Enrichment factor analysis, statistical analysis, and seasonal variability suggest that elements such as Mn, Cr, Zn, Fe, and Cu are attributed to traffic, V and Ni to oil combustion while Cd and Pb to industrial activities with regional origin. Meteorological parameters such as rain, boundary layer height (BLH), and air mass origin were found to significantly influence element concentrations. Periods with high frequency of northern and eastern air masses (from high populated and industrialized areas) are characterized by high metal concentrations. Finally, inner city and traffic emissions were also evaluated in PM2.5 fraction. Significant contributions (>50 %) were measured in the traffic site for Mn, Fe, Cr, Zn, and Cu, confirming that vehicle emissions contribute significantly to their levels, while in the urban site, the lower contributions (18 to 33 %) for all measured metals highlight the influence of regional sources on their levels.