Winter Maximum Research Articles

Analysis of the Effect of Climate Change on the Characteristics of Rainfall in Igeldo-Gipuzkoa (Spain)

In recent years, numerous studies have been carried out on changes in the temperature and precipitation regimes and in the frequency of the extreme events that are a result of climate change. While there is evidence of an increase in temperature at a global level, this globality does not seem to occur with precipitation. The Igeldo weather station (San Sebastian) has one of the longest recorded rainfall intensity series in Spain and can be considered as representative of the Cantabrian coast. This circumstance makes it the ideal place to analyse the trend of the pluviometric regime of this area, and this was precisely the objective of this study. A total of 165 series of pluviometric parameters were obtained to characterise the pluviometric regime. The Mann–Kendall and Spearman tests were applied to evaluate the trends of the different parameters, and the Pettitt test was applied to detect the existence of change points. In all the series, it was proven that there were no significant trends or change points. Significant increasing trends were only detected in the series of maximum winter precipitation. In general terms, it can be concluded that the precipitation regime in Igeldo is quite stationary in the context of climate change.

Variability of Atmospheric CO2 Over the Arctic Ocean: Insights From the O‐Buoy Chemical Observing Network

AbstractAs the Arctic climate rapidly warms, there is a critical need for understanding variability and change in the Arctic carbon cycle, but sparse spatial coverage of observations has hindered progress. This work analyzes measurements of atmospheric CO2 in the Arctic from long‐term on‐ice measurements (the O‐Buoy Network), as well as coastal observatories from 2009 to 2016. The on‐ice measurements showed smaller seasonal amplitudes than coastal observatories, in contrast to the general observation of poleward increases of seasonal cycle amplitude. Average on‐ice measurements were also lower than their coastal counterparts during winter and spring, contradicting the expectation that CO2 increases poleward in boreal winter. We compared the observations to CO2 simulated in an updated version of GEOS‐Chem 3‐D chemical transport model, which includes new tracers of airmass history and CO2 sources and sinks. The model reproduced the observed features of the seasonal cycle and showed that terrestrial biosphere fluxes and synoptic transport explain most CO2 variability (both synoptic and interannual) over the Arctic Ocean surface. The polar airmass partially isolates the Arctic Ocean surface air from terrestrial CO2 exchange, which explains the reduced seasonal cycle amplitude and winter maxima. All Arctic coastal sites had similar CO2 interannual variability, particularly in summer, which was largely reproduced by the model. The interannual variability observed over sea ice, however, was distinct from the coastal sites and not reproduced by the model. Air‐sea CO2 exchange in and around sea ice, which was once thought to be negligible, may be an important driver of interannual variability over the Arctic Ocean.

Seasons dynamics of biochemical parameters of blood of cows during the dry period

The study of the metabolism in the body of cows, depending on the physiological state, factors of feeding and the conditions of content in different seasons of the year, is a necessary condition for the direct effect on their reproductive capacity and productivity. In particular, the scientific and practical interest is the disclosure of physiological and biochemical mechanisms, which are associated with the characteristics of metabolism in the body of cows during pregnancy. The purpose of the research was to study the features of protein metabolism in highly productive deep-calving cows in different seasons of the year. The object for the study is served cows with milk production of 5–6 thousand kg for lactation at 8–9 months of pregnancy and blood samples taken from them. Biochemical study of cows blood plasma was carried out according to generally accepted methods. The recorded seasonal changes in protein exchange of deep-calving cows (Table) were cyclic. In contrast to the total protein content, seasonal differences in its fractional composition were also detected. The dynamics of the change in protein ratio is similar to that of albumin. During the summer, the content of a-globulins increased by 20.1 %, b-globulins by 17.3 %, g-globulins per 20.5 % compared with the spring period. In dry-bodied cows, the activity of ALT and AST in winter increases, reaching its maximum value but in the summer activity of ALT significantly decreased, and its activity was even less than the physiological limits. ACT activity was the lowest in the autumn. Determined that seasonal changes in the protein metabolism of dry cows were cyclic character. A decrease in the content of globulins (due to a-, b- and g-globulins) was observed during the winter period compared to the summer period. This characterizes the high activity of protein metabolism in the summer with the decline in winter. In dry cows, the albumin content and protein ratio reached a maximum in winter with a significant decrease in spring and summer, and in the autumn they again started to rise. The degree and direction of changes in ALT and AST activity were similar to seasonal changes in albumin content. This indicates a low intensity of protein-synthesizing processes in the liver in summer.

Distribution and Long-Term Trends of Tropospheric Ozone Concentrations in Ireland

Tropospheric ozone (O3) is highly variable over space and time reflecting local production and destruction as well as addition and loss through regional and long-range transport. In this study, O3 concentrations at 11 stations in Ireland and their long-term trends (7–9 sites) were evaluated; O3 concentrations (2015–2019) varied spatially, with the highest annual mean concentrations along the Atlantic west coast (69–75 µg/m3), and the lowest in urban centres (39–43 µg/m3). Ozone followed a seasonal pattern of spring and winter maximum and summer–autumn minimum. Significant long-term (2005–2019) increases were observed in annual O3 concentration at two rural stations, while increases were larger and more frequent during winter with increases at four out of seven stations. During the decade 2010–2019, significant annual increases were observed at four out of nine stations. Observed site- and season-specific increasing trends in O3 concentrations likely reflected changes in regional precursor gas emissions sources. Despite reported decreases in background concentrations in the marine boundary layer in northern mid-latitudes in recent decades, O3 concentrations at some sites in Ireland have increased significantly primarily driven by changes in winter concentrations. There were no significant decreasing trends at any site or in any season.

Characteristics of Gravity Wave Horizontal Phase Velocity Spectra in the Mesosphere Over the Antarctic Stations, Syowa and Davis

AbstractMesospheric gravity‐wave (GW) phase velocity spectra and total powers at two Antarctic stations, Davis and Syowa, were derived using OH airglow data from March to October in 2016. The total powers have similar seasonal variation, that is, maxima in winter at both stations. The average powers at both stations in winter were not significantly different. However, the power at Davis in September was three times smaller than that at Syowa. This lower power at Davis was attributed to GWs with omnidirectional phase velocity. These lower GW activities at Davis could be attributed to a longitudinal variation in wave filtering; a stronger wind at Davis filtered out more GWs than at Syowa. Also, to explore possible sources in the middle atmosphere, we investigated one event, in which GWs with ∼100 ms−1 southeastward phase velocity appeared at Davis on 29 August. The raytracing method was applied, and its result indicated that those GWs with high southeastward phase velocity propagated from ∼45 km altitude or higher over the Southern Ocean. A large residual of the non‐linear balanced equation was found at 50 km on its ray path. GWs, very likely emitted from a tropospheric jet, were also found near the ray path at the termination altitude over the Southern Ocean and possibly appeared saturated between 45 and 50 km. Therefore, the OH imager at Davis probably captured GWs generated by a spontaneous adjustment in the upper stratosphere and/or secondary GWs produced by the breaking of the GWs that have originated from the tropospheric jet.

Ground-Based FTIR-Measurements of the Atmospheric Nitric Acid at the NDACC Site of St. Petersburg

Atmospheric nitric acid (HNO3) has a significant impact on the formation of the ozone layer; therefore, its content is regularly monitored using various local and remote-sensing methods. We used ground-based measurements of solar IR spectra with a Bruker 125HR Fourier spectrometer to derive information on the HNO3 content at the St.Petersburg observational NDACC site in Peterhof. The HNO3 time series obtained showed a pronounced seasonal cycle with a maximum in winter and early spring and a minimum in summer and early autumn. The averaged seasonal variations in nitric acid varied from –30 to +60% for the 0–15 km layer, from –25 to +25% for the 15–50 km layer, and from –25 to +30% for total columns. For 2009–2022 measurement period, no statistically significant trend was found in the time series considered. Comparison of HNO3 stratospheric columns with independent satellite measurements by the MLS and ACE-FTS instruments showed their qualitative and quantitative agreement; the correlation coefficient between ground-based and satellite measurements totals 0.88–0.93. Time series on the vertical structure of the atmospheric nitric acid measured at the St.Petersburg site can be used both to analyze the state of the ozonosphere and to validate satellite measurements and refine the parameters of atmospheric models.

Secondary formation and source analysis of carbonaceous components in PM1 in a typical city, Southwest of China

Carbonaceous components are major components of PM1, which have a significant impact on climate change, air quality and human health. However, the secondary formation and source analysis of carbonaceous components in PM1 are still unclear. Therefore, in order to study the secondary formation and sources of carbonaceous components in PM1, PM1 samples were collected in Chengdu, a typical city located in southwest of China, from 2018 to 2019. The concentrations of organic carbon (OC), elemental carbon (EC) and isotopic compositions of carbon (δ13C) in PM1 were determined using a thermal/optical carbon analyzer and elemental analyzer-isotope ratio mass spectrometer. In addition, the δ13C values from relevant potential sources (C3 plants, C4 plants, vehicle exhaust and coal) were also determined. The results showed that the annual average concentrations of OC and EC in PM1 in Chengdu were 6.43 ± 3.30 μg·m−3 and 1.99 ± 0.98 μg·m−3, accounting for 13.83% and 4.28% of the PM1 mass concentration, respectively. The concentrations of OC in PM1 ranked in the order of winter > summer > spring > autumn, while the concentrations of EC varied in the order of winter > spring > autumn > summer. The concentrations of OC and EC in PM1 reached the maximum in winter, mainly due to the special meteorological conditions and significantly higher pollutant emissions. The correlations of OC and EC were higher in spring, autumn and winter, and lower in summer. It showed that OC and EC might have the same sources in spring, autumn and winter, while the sources of OC and EC were relatively complex in summer. The annual average concentration of secondary organic carbon (SOC) in PM1 was 2.23 ± 1.22 μg·m−3. The concentrations of SOC were higher in autumn and winter and lower in spring and summer. The special meteorological conditions and significantly higher pollutant emissions are important reasons for the higher SOC concentrations in winter. On the other hand, the low temperature in winter can also promote the formation of SOC. The results of carbon isotopic compositions indicated that the carbonaceous components in PM1 were mainly derived from vehicle exhaust (52.4%), C3 plants combustion (26.2%), coal burning (16.2%) and C4 plants combustion (5.2%). The findings help to deepen the understanding of the secondary formation and sources of carbonaceous components in PM1 and provide theoretical guidance for environmental management.

Comparison of Spatio-Temporal Variability of Daily Maximum Flows in Cold-Season (Winter and Spring) in Southern Quebec (Canada)

Quebec has experienced a significant decrease in the amount of snow and an increase in temperature during the cold season. The objective of this study is to analyze the impacts of these climate changes on the spatio-temporal variability of the daily maximum flows generated by snowmelt in winter and spring using several statistical tests of correlation (spatial variability) and long-term trend (temporal variability). The study is based on the analysis of flows measured in 17 watersheds (1930–2019) grouped into three hydroclimatic regions. Regarding the spatial variability, the correlation analysis revealed that in winter, the flows are positively correlated with the agricultural area and the daily maximum winter temperature. In the spring, the flows are positively correlated with the drainage density and the snowfall but negatively correlated with the area of wetlands and the daily maximum spring temperature. As for temporal variability (long-term trend), the application of eight statistical tests revealed a generalized increase in flows in winter due to early snowmelt. In the spring, despite the decreased snow cover, no negative trend was observed due to the increase in the spring rainfall, which compensates for the decrease in the snowfall. This temporal evolution of flows in the spring does not correspond to the predictions of climate models. These predict a decrease in the magnitude of spring floods due to the decrease in the snowfall in southern Quebec.

Influence of Climatic Variables on Incidence of Whitefly-Transmitted Begomovirus in Soybean and Bean Crops in North-Western Argentina.

Over the last 20 years, begomoviruses have emerged as devastating pathogens, limiting the production of different crops worldwide. Weather conditions increase vector populations, with negative effects on crop production. In this work we evaluate the relationship between the incidence of begomovirus and weather before and during the crop cycle. Soybean and bean fields from north-western (NW) Argentina were monitored between 2001 and 2018 and classified as moderate (≤50%) or severe (>50%) according to the begomovirus incidence. Bean golden mosaic virus (BGMV) and soybean blistering mosaic virus (SbBMV) were the predominant begomovirus in bean and soybean crops, respectively. Nearly 200 bio-meteorological variables were constructed by summarizing climatic variables in 10-day periods from July to November of each crop year. The studied variables included temperature, precipitation, relative humidity, wind (speed and direction), pressure, cloudiness, and visibility. For bean, high maximum winter temperatures, low spring humidity, and precipitation 10 days before planting correlated with severe incidence. In soybeans, high temperatures in late winter and in the pre-sowing period, and low spring precipitations were found to be good predictors of high incidence of begomovirus. The results suggest that temperature and pre-sowing precipitations can be used to predict the incidence status [predictive accuracy: 80% (bean) and 75% (soybean)]. Thus, these variables can be incorporated in early warning systems for crop management decision-making to reduce the virus impact on bean and soybean crops.

Opposing Shifts of the Hadley Cell Edge and Eddy-Driven Jet Latitude in the Last Glacial Maximum: A Parameter Sweep Study Using a Dynamical Core GCM

Abstract A coherent poleward displacement of the Hadley cell (HC) edge and eddy-driven jet latitude has been well documented in the Southern Hemisphere (SH) under the present and future climate changes. However, a recent study showed that during the Last Glacial Maximum (LGM) winter, an equatorward shift of the HC edge but a poleward shift of the jet latitude are found in the SH. These opposing circulation changes are investigated in this study by conducting the parameter sweep experiments using a dynamical core general circulation model (GCM). By systematically varying the amplitude of tropical upper-tropospheric and polar surface cooling, mimicking the LGM-like climate state, an opposing shift of circulation is reproduced when polar cooling is much stronger than tropical cooling. This is due to the higher sensitivity of the jet-latitude change compared to the HC-edge change in response to polar cooling. Eddy cospectra analysis reveals that the poleward jet shift is dominated by fast waves as the baroclinic zone expands poleward with increasing polar surface cooling. Instead, the HC-edge change is largely attributed to the activity of slow waves and the axisymmetric circulation change. They lead to the HC edge being weakly influenced by extratropical baroclinicity, resulting in an equatorward shift of the HC edge under a global cooling–like condition. Similar circulation changes but with an opposite sign are also found in global warming–like experiments. This result suggests that a poleward HC shift together with an equatorward jet shift can occur even in a future climate if Arctic amplification is accelerated relative to tropical warming.

Modulation of the seasonal cycle of the Antarctic sea ice extent by sea ice processes and feedbacks with the ocean and the atmosphere

Abstract. The seasonal cycle of the Antarctic sea ice extent is strongly asymmetric, with a relatively slow increase after the summer minimum followed by a more rapid decrease after the winter maximum. This cycle is intimately linked to the seasonal cycle of the insolation received at the top of the atmosphere, but sea ice processes as well as the exchanges with the atmosphere and ocean may also play a role. To quantify these contributions, a series of idealized sensitivity experiments have been performed with an eddy-permitting (1/4∘) NEMO-LIM3 (Nucleus for European Modelling of the Ocean–Louvain-la-Neuve sea ice model version 3) Southern Ocean configuration, including a representation of ice shelf cavities, in which the model was either driven by an atmospheric reanalysis or coupled to the COSMO-CLM2 regional atmospheric model. In those experiments, sea ice thermodynamics and dynamics as well as the exchanges with the ocean and atmosphere are strongly perturbed. This perturbation is achieved by modifying snow and ice thermal conductivities, the vertical mixing in the ocean top layers, the effect of freshwater uptake and release upon sea ice growth and melt, ice dynamics, and surface albedo. We find that the evolution of sea ice extent during the ice advance season is largely independent of the direct effect of the perturbation and appears thus mainly controlled by initial state in summer and subsequent insolation changes. In contrast, the melting rate varies strongly between the experiments during the retreat, in particular if the surface albedo or sea ice transport are modified, demonstrating a strong contribution of those elements to the evolution of ice coverage through spring and summer. As with the advance phase, the retreat is also influenced by conditions at the beginning of the melt season in September. Atmospheric feedbacks enhance the model winter ice extent response to any of the perturbed processes, and the enhancement is strongest when the albedo is modified. The response of sea ice volume and extent to changes in entrainment of subsurface warm waters to the ocean surface is also greatly amplified by the coupling with the atmosphere.

Predicting Iran’s future agro-climate variability and coherence using zonation‑based PCA

The effects of climate changes on agroecosystems can cause relevant issues. Using principal component analysis (PCA) we determined the 67 agricultural climate indicators (ACI) at 44 of Iran’s synoptic stations under current (1990-2019) and future (2025, 2050, 2075, and 2100) conditions. Based on UNESCO aridity index, the agroecological zonation (AEZ) was used to classify Iran’s regions (very dry, dry, semidry and humid climates). Using the PCA method, the first 5 principal components were determined by including data sets for temperature (winter, spring, summer and autumn maximum and winter minimum temperature), precipitation (winter and summer precipitation), reference evapotranspiration (ETref), and the degree of growth days in spring and winter, which explained about 96 percent of the total variance. For each climate empirical equation for ETref was selected. In order to accurate evaluation of ETref were used The Penman-Monteith based on FAO56 (PM-FAO56) for the very dry climate, the Hargreaves equation for the semidry climate, and the Penman 1 and 2 equations for the dry and humid climates, respectively. According to the results, the first component alone, with an eigenvalue of 41.15, explained more than 74 percent of the total variance. Based on the results of zoning by the PCA outcomes, the stations for 1990-2019 were classified into 7 zones. While 2025, 2050, 2075, and 2100 were classified in 6, 7, 6, and 5 zones, respectively. Under the future climatic conditions of the country, in terms of climatic indicators, the similarity between the stations will increase and the climatic diversity of the country will decline compared to current conditions. The results demonstrated that the PCA method would be valuable for monitoring AEZ in semidry climates at reasonably long periods.

Understanding the variations and sources of CO, C2H2, C2H6, H2CO, and HCN columns based on 3 years of new ground-based Fourier transform infrared measurements at Xianghe, China

Abstract. Carbon monoxide (CO), acetylene (C2H2), ethane (C2H6), formaldehyde (H2CO), and hydrogen cyanide (HCN) are important trace gases in the atmosphere. They are highly related to biomass burning, fossil fuel combustion, and biogenic emissions globally, affecting air quality and climate change. However, the variations and correlations among these species are not well known in northern China due to limited measurements. In June 2018, we installed a new ground-based Fourier transform infrared (FTIR) spectrometer (Bruker IFS 125HR) recording mid-infrared high spectral resolution solar-absorption spectra at Xianghe (39.75∘ N, 116.96∘ E), China. In this study, we use the latest SFIT4 code, together with advanced a priori profiling and spectroscopy, to retrieve these five species from the FTIR spectra measured between June 2018 and November 2021. The retrieval strategies, retrieval information and retrieval uncertainties are presented and discussed. For the first time, the time series, variations, and correlations of these five species are analyzed at a typical polluted site in northern China. The seasonal variations in C2H2 and C2H6 total columns show a maximum in winter–spring and a minimum in autumn, whereas the seasonal variations in H2CO and HCN show a maximum in summer and a minimum in winter. Unlike the other four species, the FTIR measurements show that there is almost no seasonal variation in the CO column. The correlation coefficients (R) between the synoptic variations in CO and the other four species (C2H2, C2H6, H2CO, and HCN) are between 0.68 and 0.80, indicating that they are affected by common sources. Using the FLEXPART model backward simulations and satellite fire measurements, we find that the variations in CO, C2H2, C2H6, and H2CO columns are mainly dominated by the local anthropogenic emissions, while HCN column observed at Xianghe is a good tracer to identify fire emissions.

Herpetological remains from the Lower Magdalenian site of El Juyo (Cantabria, Spain): the challenge of reconstructing climate and landscape from poorly diverse assemblages

ABSTRACT El Juyo is a Cantabrian Lower Magdalenian cave site located approximately 8 km west of the city of Santander. The excavations covered an area over 40 m2, and the stratified deposits reach 3.5 m thick, with an estimated duration of Magdalenian occupation of around 1,000 years. Here, we present the first study of the herpetofaunal assemblages from El Juyo and explore their significance in terms of quantitative palaeoclimatic and palaeoenvironmental reconstructions using different quantitative methods. The palaeoherpetofaunal assemblages documented at El Juyo have a much lower diversity than present day. All methods applied to these assemblages characterised the climate as colder (between −8.5 and −3.7°C) and dryer (between −415 and −344 mm) than today, whereas landscape reconstructions suggest humid open area together with a potentially good representation of woodland areas in the vicinity of the site. This indicates that the climate during the Dryas I was much colder and dryer than today, even if the proximity of the sea may have mitigated in some way the harshness of the climate in this area. Rainfall seasonality pattern changed between the coldest periods of the Dryas I and today from more abundant precipitation during summer to late fall and winter maximum.

Winter mortality of a passerine bird increases following hotter summers and during winters with higher maximum temperatures.

Climate change may influence animal population dynamics through reproduction and mortality. However, attributing changes in mortality to specific climate variables is challenging because the exact time of death is usually unknown in the wild. Here, we investigated climate effects on adult mortality in Australian superb fairy-wrens (Malurus cyaneus). Over a 27-year period, mortality outside the breeding season nearly doubled. This nonbreeding season mortality increased with lower minimum (night-time) and higher maximum (day-time) winter temperatures and with higher summer heat wave intensity. Fine-scale analysis showed that higher mortality in a given week was associated with higher maxima 2 weeks prior and lower minima in the current fortnight, indicating costs of temperature drops. Increases in summer heat waves and in winter maximum temperatures collectively explained 62.6% of the increase in mortality over the study period. Our results suggest that warming climate in both summer and winter can adversely affect survival, with potentially substantial population consequences.

Потери почвы от дефляции в Ростовской области

Purpose: collection, analysis and generalization of data on wind speed and the intensity of deflation processes in Rostov region, that helps assessing the quantitative side of soil loss depending on wind speed, weather conditions, terrain, tillage method and other factors, and development of wind corridors for the conditions of the region under consideration. Materials and methods. The research was carried out on chestnut soils, southern and ordinary chernozems of the agricultural enterprise “Rassvet” of Aksai district and the agricultural enterprise “Krasnoarmeyskoe” of Oryol district of Rostov region, and the results of other scientists, who have been conducting research in Rostov region since 1969, were analyzed and summarized. Wind speed was measured with anemometers at a height of 2 m above the soil level, and the soil mass moved by winds was determined by the Erosion bridge (pin method) and dust collectors of our own design. Methods of analysis and synthesis as a systematic approach to achieving the goal were used. Results. The wind direction and speed in Rostov region depend on the seasonal position of pressure centers: the Siberian maximum in winter and the Azores in summer. Over the 54 years of research from 1969 to 2023, dust storms and drifting snow were observed 11 times, i.e. once every five years. Mathematical processing of long-term research data made it possible to obtain dependencies for assessing the effect of wind speed on soil removal on average in 1 hour, to determine soil removal coefficients, to propose zoning of the region into five deflationary regions, to develop a map diagram of deflationary zones and wind corridors of Rostov region. Conclusions. The greatest soil losses in wind-impact directions were in 1969 up to 800–900 t/ha for a duration of 300 h, in 1972 – 170–200 t/ha for a duration of 96 h; in 1984, with a daytime wind speed of 10–14 m/s with gusts of up to 25–30 m/s for a duration of 142 h, soil losses amounted to 218 t/ha.

Assessment of carbonaceous aerosols at Mukteshwar: A high-altitude (~2200 m amsl) background site in the foothills of the Central Himalayas

The present study examined the equivalent black carbon (eBC) mass concentrations measured over 10.5 years (September 2005–March 2016) using a 7-wavelength Aethalometer (AE-31) at Mukteshwar, a high-altitude and regional background site in the foothills of Indian central Himalayas. The total spectral absorption coefficient (babs) was divided into three categories: black carbon (BC) and brown carbon (BrC); fossil fuels (FF) and wood/biomass burning (WB/BB); and primary and secondary sources. At the wavelength of 370 nm, a significant BrC contribution (25 %) to the total babs is identified, characterized by a pronounced seasonal variation with winter (December–January-February) maxima (31 %) and post-monsoon (October and November) minima (20 %); whereas, at 660 nm, the contribution of BrC is dramatically less (9 %). Climatologically, the estimated BCFF at 880 nm ranges from 0.25 ± 0.19 μg m−3 in July to 1.17 ± 0.80 μg m−3 in May with the annual average of 0.67 ± 0.63 μg m−3, accounting for 79 % of the BC mass. The maximum BCFF/BC fraction reaches its peak value during the monsoon (July and August, 85 %), indicating the dominance of local traffic emissions due to tourism activities. Further, the highest BCWB concentration observed during pre-monsoon (March–May) suggests the influence of local forest fires along with long-range transported aerosols from the low-altitude plains. The increased contribution of BrC (26 % at 370 nm) and WB absorption (61 % at 370 nm) to the total absorption at the shorter wavelengths suggests that wood burning is one of the major sources of BrC emissions. Secondary BrC absorption accounts for 24 % [91 %] of the total absorption [BrC absorption] at 370 nm, implying the dominance of secondary sources in BrC formation. A trend analysis for the measured BC concentration shows a statistically significant increasing trend with a slope of 0.02 μgm−3/year with a total increase of about 22 % over the study period. A back trajectory-based receptor model, potential source contribution function (PSCF), was used to identify the potential regional source region of BC. The main source regions of BC are the northwest states of India in the IGP region and the northeast Pakistan region.

Implications of modeling seasonal differences in the extremal dependence of rainfall maxima

For modeling extreme rainfall, the widely used Brown–Resnick max-stable model extends the concept of the variogram to suit block maxima, allowing the explicit modeling of the extremal dependence shown by the spatial data. This extremal dependence stems from the geometrical characteristics of the observed rainfall, which is associated with different meteorological processes and is usually considered to be constant when designing the model for a study. However, depending on the region, this dependence can change throughout the year, as the prevailing meteorological conditions that drive the rainfall generation process change with the season. Therefore, this study analyzes the impact of the seasonal change in extremal dependence for the modeling of annual block maxima in the Berlin-Brandenburg region. For this study, two seasons were considered as proxies for different dominant meteorological conditions: summer for convective rainfall and winter for frontal/stratiform rainfall. Using maxima from both seasons, we compared the skill of a linear model with spatial covariates (that assumed spatial independence) with the skill of a Brown–Resnick max-stable model. This comparison showed a considerable difference between seasons, with the isotropic Brown–Resnick model showing considerable loss of skill for the winter maxima. We conclude that the assumptions commonly made when using the Brown–Resnick model are appropriate for modeling summer (i.e., convective) events, but further work should be done for modeling other types of precipitation regimes.

Three decades of environmental change studies at alpine Finse, Norway: climate trends and responses across ecological scales

The International Tundra Experiment (ITEX) was established to understand how environmental change impacts Arctic and alpine ecosystems. The success of the ITEX network has allowed for several important across-site syntheses, and for some ITEX sites enough data have now been collected to perform within-site syntheses on the effects of environmental change across ecological scales. In this study, we analyze climate data and synthesize three decades of research on the ecological effects of environmental change at the ITEX site at Finse, southern Norway. We found a modest warming rate of +0.36 °C per decade and minor effects on growing season length. Maximum winter snow depth was highest in winters with a positive North Atlantic Oscillation. Our synthesis included 80 ecological studies from Finse, biased towards primary producers with few studies on ecological processes. Species distributions depended on microtopography and microclimate. Experimental warming had contrasting effects on abundance and traits of individual species and only modest effects at the community level above and below ground. In contrast, nutrient addition experiments caused strong responses in primary producer and arthropod communities. This within-site synthesis enabled us to conclude how different environmental changes (experimental and ambient warming, nutrient addition, and environmental gradients) impact across ecological scales, which is challenging to achieve with across-site approaches.

Observations of Inertia Gravity Waves in the Western Pacific and Their Characteristic in the 2015/2016 Quasi‐Biennial Oscillation Disruption

AbstractThe statistical characteristics of inertia‐gravity waves (IGWs) in the troposphere (2–14 km) and lower stratosphere (18–28 km) are analyzed using daily radiosonde observations over six stations in the Western Pacific from 2013 to 2018. Stokes parameter method is used to extract the characteristic parameters of gravity waves (GWs), which are divided into upward and downward propagating waves, and compared with the results of hodograph analysis. In the stratosphere, due to the filtering effect of the background wind field, the IGWs generated in the troposphere mainly propagate eastward with lower frequency range. The tropospheric IGWs have obvious seasonal variation in spectral amplitude and energy, with the maximum in winter and the minimum in monsoon from 2013 to 2018. The stratospheric IGWs are enhanced during phase transition of the quasi‐biennial oscillation, when the enhanced easterly wind appears in the lowest stratosphere, accompanied by enhanced wave energy in the troposphere. During the quasi‐biennial oscillation disruption in late 2015 and early 2016, the tropospheric wave source excites more intense IGWs propagating upward. After reaching the stratosphere, IGWs with slower phase speed are absorbed by the mean flow, dissipating momentum to the lower stratosphere and generating additional enhanced westward forcing, which may have contributed to the development of the easterly wind within the westerly quasi‐biannual oscillation phase.