Weather Types Research Articles

A Ceilometer-Derived Climatology of the Convective Boundary Layer Over a Southern Hemisphere Subtropical City

Accurate measurements of the depth of the convective boundary layer (CBL) are fundamental for understanding and forecasting weather, air quality, and climate. However, the CBL depth (BLD) shows significant spatial and temporal variability, which is challenging to measure and model. Ceilometer instruments, which estimate the CBL depth from aerosol layers, are relatively cheap, have high temporal resolution, and have the potential for increased spatial coverage. Nevertheless, their performance in subtropical environments with low aerosol concentrations is unknown. Furthermore, climatological studies of the variability in the urban CBL depth are scarce, especially in the Southern Hemisphere, and very few studies have examined the relationship between BLD variability and synoptic conditions. Using three years of continuous ceilometer data, we present a novel climatology of the temporal variability in CBL depth over the Southern Hemisphere subtropical, coastal city of Auckland, New Zealand. The results indicate that the median daytime maximum CBL depth (BLDMAX) over the Auckland CBD is 1100 m a.g.l. (above ground level) during summer and 700 m a.g.l. during winter. Strong relationships are found between the maximum CBL depth and both solar radiation and soil moisture; however, no relationship is found between the maximum CBL depth and the synoptic conditions as determined by the New Zealand Kidson weather types synoptic classification. The absence of a relationship between the maximum CBL depth and Kidson weather types may explain the poor correlation previously observed between synoptic class and air pollution events in Auckland.

Influence of Meteorological Conditions on Ozone Pollution at Shangdianzi Station Based on Weather Classification

As a typical secondary pollutant, tropospheric ozone has become the primary pollutant in Beijing in spring and summer, and meteorological factors are one of the main factors affecting the change in concentration. Using atmospheric composition and meteorological observation data from 2008 to 2017, the weather types in Beijing were divided into six categories by Lamb classification and Mann-Whitney U test. Among these, the mean and extreme values of ozone concentration of SWW and C types at Shangdianzi station were the highest, and the highest frequency was from April to September, with a total of 47.4%. The main contribution weights of the two types were determined by a multiple stepwise regression equation. The southwest wind prevailed in 54.0% of SWW and C types, and the newly discharged pollutants and secondary aging air masses were continuously transported by the southwest air flow. The vertical velocity zero layer appeared near 850 hPa. The horizontal and vertical meteorological conditions were conducive to the transport, accumulation, and secondary generation of ozone. The northeast wind prevailed in 64.7% of AN and ESN types, and the air masses source was clean. The same subsidence movement and air divergence prevailed above 1000 hPa. The discharged pollutants can also be diluted and diffused quickly, and the ozone concentration was at a low value. Taking the NW type on May 3, 2015 as an example, although the northwest air flow prevailed on the ground, with clean source, the residual high concentration of ozone above the boundary layer was transported to the near ground through the vertical subsidence of the atmosphere, resulting in the high concentration of ozone on some days.

Transport Characteristics of Air Pollution in Tianjin Based on Weather Background

Regional transport is an important factor when considering the prevention and control of air pollution. The aim of this study was to provide support for the joint prevention and control of air pollution in the Beijing-Tianjin-Hebei region. With a focus on an analysis of the relationship between regional transport and meteorological conditions based on the weather background, an atmospheric chemical model was developed to quantitatively estimate the impact of regional transport on Tianjin from October 2016 to September 2017. The results showed that the contribution percentage of regional transport in cities in plains in the Beijing-Tianjin-Hebei region was significantly higher than in cities in mountains. The local contribution of PM2.5 in the Tianjin area was 62.9% and the contribution of regional transport was 37.1%. This was mainly affected by transmissions of Chanzhou, Langfang, central and southern Hebei, Beijing, Tanshan, and Shandong. Regional transport was the most significant from April to June, the weakest from July to August, and the highest contributor to local emissions. Regional transport was closely related to weather situation, wind field, precipitation, and other meteorological conditions. Post-high pressure and pre-frontal low pressure were the two types of pollution weather with the highest proportion in regional transport, and the impact of air pollution transport under the southwest wind, westerly wind and south wind was the most apparent. Wind speed of 2-3 m·s-1 was beneficial to the regional transport of PM2.5, and precipitation above 5 mm will effectively reduce the regional transport of air pollutants. For different pollution types and heavy pollution stages, the contribution of regional transport was the most apparent in light pollution weather, being 20.5% higher than the average. The heavy pollution weather was controlled by static stable air mass, and because of the migration of high PM2.5 concentrations, pollution air mass in the surrounding area had a significant impact on the accumulation of pollution and transport in the region. The contribution ratio of PM2.5 transport in the heavy pollution period was more than the average and was approximately 10% and 15% higher. In the process of heavy pollution, the proportion of transport contribution in the initial accumulation stage and peak stage were higher than in other periods, and 14.5% and 19.5% higher than in the outbreak stage. The contribution of local emissions in the outbreak stage was more significant, being 9.9% higher than average.

Comparative Analysis of Site-Specific Soiling Losses on PV Power Production

The rapid global expansion of utility-scale solar power parks has led to an increased effort to overcome the challenges related to accumulated soiling on PV panels. So far, little attention has been paid to the differing impacts of various dust types. This article focuses on the decreased transmission of sunlight through the PV cover glass with an increased level of dust layer density. The loss in the PV power production due to soiling is heavily dependent on site-specific climatological and anthropological parameters, such as topography, weather, human activity, and PV module type. Three natural dust samples from solar power plants in Egypt and Jordan were analyzed for structural, chemical, and optical attributes, including transmission measurements. Cement was added to the analysis and compared with the natural dust samples. We show that different reductions in transmission between the different dust types are mostly ascribed to a dissimilar particle size distribution and albedo, where the former is the most crucial determinant. Under equal weather conditions and similar dust layer density on the PV cover glass plates, a lower particle size distribution would result in a more dramatic drop of transmission. Additionally, the darker appearance of the grains increases the absorption of sunlight causing a further loss of light due to soiling. The results show that between the “best” and the “worst” natural panel dust studied in this article, a difference in transmission of 5 % was identified. At equal weather conditions, this directly translates into a similar loss in electricity production.

Key Points in Air Pollution Meteorology.

Although emissions have a direct impact on air pollution, meteorological processes may influence inmission concentration, with the only way to control air pollution being through the rates emitted. This paper presents the close relationship between air pollution and meteorology following the scales of atmospheric motion. In macroscale, this review focuses on the synoptic pattern, since certain weather types are related to pollution episodes, with the determination of these weather types being the key point of these studies. The contrasting contribution of cold fronts is also presented, whilst mathematical models are seen to increase the analysis possibilities of pollution transport. In mesoscale, land–sea and mountain–valley breezes may reinforce certain pollution episodes, and recirculation processes are sometimes favoured by orographic features. The urban heat island is also considered, since the formation of mesovortices determines the entry of pollutants into the city. At the microscale, the influence of the boundary layer height and its evolution are evaluated; in particular, the contribution of the low-level jet to pollutant transport and dispersion. Local meteorological variables have a major influence on calculations with the Gaussian plume model, whilst some eddies are features exclusive to urban environments. Finally, the impact of air pollution on meteorology is briefly commented on.

Weather Types Affect Rain Microstructure: Implications for Estimating Rain Rate

Quantitative precipitation estimation (QPE) through remote sensing has to take rain microstructure into consideration, because it influences the relationship between radar reflectivity Z and rain intensity R. For this reason, separate equations are used to estimate rain intensity of convective and stratiform rain types. Here, we investigate whether incorporating synoptic scale meteorology could yield further QPE improvements. Depending on large-scale weather types, variability in cloud condensation nuclei and the humidity content may lead to variation in rain microstructure. In a case study for Bavaria, we measured rain microstructure at ten locations with laser-based disdrometers, covering a combined 18,600 h of rain in a period of 36 months. Rain was classified on a temporal scale of one minute into convective and stratiform based on a machine learning model. Large-scale wind direction classes were on a daily scale to represent the synoptic weather types. Significant variations in rain microstructure parameters were evident not only for rain types, but also for wind direction classes. The main contrast was observed between westerly and easterly circulations, with the latter characterized by smaller average size of drops and a higher average concentration. This led to substantial variation in the parameters of the radar rain intensity retrieval equation Z–R. The effect of wind direction on Z–R parameters was more pronounced for stratiform than convective rain types. We conclude that building separate Z–R retrieval equations for regional wind direction classes should improve radar-based QPE, especially for stratiform rain events.

Dictons romans avec les douze mois : la caractérisation parémique et mensuelle de l’année

Romance Proverbs with the Twelve Months: the Paremical and Monthly Characterization of the Year. There are various types of weather and calendar proverbs in the Romance languages. Not only concerning their motivation, but also concerning their length. Among the proverbs referring to the months, some are very short, just two or three words, the so-called “minimal proverbs”, while others are quite long, and curiously defy any kind of mnemonics. Our corpus will be made up of the latter type: thirteen proverbs mentioning all the twelve months of the year, which represent five different Romance varieties; from west to east: Portuguese (1 proverb), Spanish (2), Catalan (5), Italian (4) and the Laziale Italian variant (1). We classify these formulae, which lie on the thresholds of what strictly might be considered proverbs, in two groups: proverbs without meteorological implication and meteorological proverbs. On the other hand, we classify the examples of the second group in four sections according to the characteristics that are attributed to one or several months: proverbs with a characteristic for several months, proverbs with a characteristic for each pair of months, proverbs with a characteristic for some of the months, and sayings attributing a different feature for each month. This corpus offers a glimpse to the way Romance peoples view the months and it reveals affinities in the form of paremic types (or “paremiotypes”), which tell us about the popular culture shared by the peoples that are heirs of Rome.

Lithostratigraphy, sedimentary petrography and geochemistry of the Upper Karoo Supergroup in the Central Kalahari Karoo Sub-Basin, Botswana

The Kalahari Karoo Basin of Botswana is an intracratonic basin developed in south-central Gondwana and is filled with Upper Carboniferous–Lower Jurassic Karoo Supergroup volcano-sedimentary units. The Karoo Supergroup units are unconformably covered by the Cretaceous to recent Kalahari Group. The Upper Karoo Supergroup in the Central Kalahari Karoo Sub-Basin of Botswana consists of the lacustrine sediments of the Beaufort Group (Tlhabala Formation), overlaid unconformably by the continental sediments of the Lebung Group, and by the continental basalts of the Stormberg Group. The Late Triassic to Early Jurassic Lebung Group is subdivided into the Mosolotsane Formation and the Ntane Formation. This sedimentary sequence is poorly exposed, and formation boundaries are tentatively identified by lithological changes in boreholes. Here, new sedimentological and geochemical data are used for the refinement of the stratigraphy of the Upper Karoo Supergroup in the Central Kalahari Karoo Sub-Basin of Botswana, new criteria for the identification of unit boundaries are set and provenance of the Lebung Group sediments has been defined. The geochemical investigation of the Upper Karoo Supergroup in the Central Kalahari Karoo Sub-Basin of Botswana revealed clear geochemical markers that have allowed the pinpointing of unit boundaries between the Tlhabala Formation (Beaufort Group), Mosolotsane Formation (lowermost Lebung Group). The sediments from the Tlhabala Formation have a geochemical signature typical of wackes, while the sandstones from the overlying Mosolotsane Formation and the Ntane Formation are dominated by arkose to subarkose. The transition from wacke to subarkose pinpoints the boundary between the Beaufort Group and the base of the Lebung Group. The Tlhabala Formation is characterized by increasing SiO2/Al2O3 ratio, with a maximum at the base of the Lebung Group, and by an upward decrease in the abundance of Na, K and transition metals such as Cr, Mn and Fe. The SiO2/Al2O3 ratio decreases upward in the Lebung Group. Similarly, the abundances of Na, K, Cr, Mn and Fe slightly increase upward only to show a negative peak at the Lebung Group and the Kalahari Group boundary. This contact is marked by a clear increase in the total REE content.The chemical composition of the Lebung Group sandstones also indicates a quartzose sedimentary provenance. The CIA (chemical index of alteration) values for these sandstones ranged from 63 to 73, indicating a high degree of chemical weathering. This type of intense weathering should produce high volumes of clay minerals, which are rather scarce in the studied samples. This indicates that the large amount of quartz in the Lebung Group has been recycled from the Paleoproterozoic sedimentary sequences of the Palapye Group, located southeast from the study area.

Impacts of Regional Transport and Meteorology on Ground-Level Ozone in Windsor, Canada

This study investigated impacts of regional transport and meteorology on ground-level ozone (O3) in the smog season (April–September) during 1996–2015 in Windsor, Ontario, Canada. Data from five upwind stations in the US, which are within 310 km (i.e., Allen Park and Lansing in Michigan, Erie, National Trail School, and Delaware in Ohio), were included to assess the regional characteristics of O3. The five US stations showed high degrees of similarity with O3 concentrations in Windsor, with overall strong correlations (r = 0.567–0.876 for hourly O3 and r = 0.587–0.92 for 8 h max O3 concentrations) and a low degree of divergence, indicating that O3 pollution in the study area shares regional characteristics. Meteorological conditions played important roles in O3 levels in Windsor. High O3 concentrations were associated with southerly and southwesterly air mass from which polluted and hot air mass was transported and that enhanced local photochemical O3 production. In contrast, northerly flows brought in clean, cool, and dry air mass, and led to low O3 concentrations. Strong correlations were found between numbers of days with 8 h max O3 concentrations greater than 70 ppb and numbers of days with daily max temperature greater than 30 °C, as well as between daily max temperatures and 8 h max O3 concentrations. Nearly half (45%) of the high O3 days (≥90th percentile) occurred in dry tropical weather during 1996–2015, and the 90th percentile 8 h max O3 was associated with dry tropical weather. Occurrences of both southerly flow hours and dry tropical weather type in the smog season increased during the study period. If there were more hot and dry days in the next few decades due to climate change, the effect of emission control on reducing peak O3 values would be diminished. Therefore, continued regional and international efforts are essential to control precursors’ emissions and to mitigate O3 pollution in Windsor.

Influence of weather types on the hydrosedimentary response in three small catchments on the Island of Mallorca, Spain

The influence of the sea and topography are vital factors in the atmospheric processes affecting any island, as they introduce peculiarities in the hydrosedimentary response of fluvial systems. In view of that, the relationship between the surface atmospheric conditions (weather types, WTs), rainfall, runoff and erosion dynamics in three small catchments located in Mallorca were analysed. The catchments are representative in terms of geomorphology and land use but also due to their location within the major rainfall areas previously identified in the island by (Sumner et al., 1993). Data of rainfall, runoff and sediment variables, coupled with calculated WTs were used for the 2013–2017 period. WTs frequency and distribution during this period were compared to the last climatic period reference (1981–2010) to test the climate validity of the study period. The results illustrated how hydrosedimentary response was mostly caused by eco-geographical patterns but also by differences in the response of each catchment to WTs, related to the intrinsic geographical position in the island and different exposures to humid winds. Anticyclonic WT was the most frequent, despite it being only involved in one flood event at the eastern catchment. Conversely, eastern and northeastern WTs generated more than 85% of the total runoff and sediment, representing only 39% of flood events. The understanding of the specific role of WTs on the island's hydrology was improved, considering that freshwater resources are scarce and eco-sociologically crucial.

Behavioral Responses of Tabanidae and Stomoxys calcitrans to Unbaited and Baited Nzi and Horse Pal Traps in Southern Sweden

The distribution and species diversity of tabanids and stable flies, Stomoxys calcitrans Linnaeus, 1758, in the research area, Hästhult (wood pasture) in Sweden, as well as the behavioral responses of biting flies to visual and olfactory cues were highlighted by this study. Beyond the control of tabanids and stable flies through the Nzi and Horse Pal traps that act as a surrogate host, this study sought to demonstrate the attractiveness of biting flies to these traps by comparing the results of the two periods in which the traps were unbaited and baited. The odor attractants, such as urine (a mixture of more than phenol) and acetone used to increase trap yields, made the difference to the Horse Pal and Nzi traps for S. calcitrans (L) because the number of flies caught was significantly higher. Through this study, Nzi trap with bait and Horse Pal trap with and without bait were tested for the first time as regards the tabanids and S. calcitrans (L) in Scandinavia. Surprisingly, the number of tabanids caught in the Nzi trap was equal in both situations with or without bait. The result underlined the idea that the Nzi trap manages to catch a large number of tabanids even in the absence of attractants. It turns out that the Horse Pal trap was just as effective with and without bait in capturing tabanids. Furthermore, the number of tabanids caught in both traps depended on the type of weather, and the number of stable flies depended on the weather and also the type of trap. The results of this study showed that both the visual and olfactory aspects of the Nzi and Horse Pal traps are always essential, being used successfully in the control of biting flies and optimized for various research purposes.

A Robust Method to Update Local River Inundation Maps Using Global Climate Model Output and Weather Typing Based Statistical Downscaling

Global warming is changing the magnitude and frequency of extreme precipitation events. This requires updating local rainfall intensity-duration-frequency (IDF) curves and flood hazard maps according to the future climate scenarios. This is, however, far from straightforward, given our limited ability to model the effects of climate change on the temporal and spatial variability of rainfall at small scales. In this study, we develop a robust method to update local IDF relations for sub-daily rainfall extremes using Global Climate Model (GCM) data, and we apply it to a coastal town in NW Spain. First, the relationship between large-scale atmospheric circulation, described by means of Lamb Circulation Type classification (LCT), and rainfall events with potential for flood generation is analyzed. A broad ensemble set of GCM runs is used to identify frequency changes in LCTs, and to assess the occurrence of flood generating events in the future. In a parallel way, we use this Weather Type (WT) classification and climate-flood linkages to downscale rainfall from GCMs, and to determine the IDF curves for the future climate scenarios. A hydrological-hydraulic modeling chain is then used to quantify the changes in flood maps induced by the IDF changes. The results point to a future increase in rainfall intensity for all rainfall durations, which consequently results in an increased flood hazard in the urban area. While acknowledging the uncertainty in the GCM projections, the results show the need to update IDF standards and flood hazard maps to reflect potential changes in future extreme rainfall intensities.

Traditional conservation on Chinese Metal Coins (Kepeng) from sangkulu-kulu underwater archaeological sites, Selayar Regency

This study aims to carry out conservation using a traditional approach to the artifacts of Chinese metal coins (kepeng) that are raised from the Sangkulu-kulu Selayar underwater site. The natural ingredients used are a solution of wuluh starfruit (Averrhoa Bilimbi), maja fruit solution (Aegle Marmelos (L) Correa), lime juice (Citrus Aurantifolia), tamarind juice (Tamarindus Indica) and coconut water (Cocoa nutifera). The methods used include identification of weathering. The second stage is of XRF analysis. The third stage is immersion with a conservative ingredients solution. The results showed that of the five solutions used in the cleaning of 3 types of weathering in the coin sample, the lime solution was faster in removing three types of weathering (chemistry, physical and biotic), especially for the types of chemical and biotic weathering. Acidic solutions are used to remove active patina; a tamarind solution is the most effective solution in eliminating physical weathering by a process that lasts slowly or little by little.

There's a storm a-coming: Ecological resilience and resistance to extreme weather events.

Extreme weather events (EWEs) are expected to increase in stochasticity, frequency, and intensity due to climate change. Documented effects of EWEs, such as droughts, hurricanes, and temperature extremes, range from shifting community stable states to species extirpations. To date, little attention has been paid to how populations resist and/or recover from EWEs through compensatory (behavioral, demographic, or physiological) mechanisms; limiting the capacity to predict species responses to future changes in EWEs. Here, we systematically reviewed the global variation in species’ demographic responses, resistance to, and recovery from EWEs across weather types, species, and biogeographic regions. Through a literature review and meta‐analysis, we tested the prediction that population abundance and probability of persistence will decrease in populations after an EWE and how compensation affects that probability. Across 524 species population responses to EWEs reviewed (27 articles), we noted large variation in responses, such that, on average, the effect of EWEs on population demographics was not negative as predicted. The majority of species populations (80.4%) demonstrated compensatory mechanisms during events to reduce their deleterious effects. However, for populations that were negatively impacted, the demographic consequences were severe. Nearly 20% of the populations monitored experienced declines of over 50% after an EWE, and 6.8% of populations were extirpated. Population declines were reflected in a reduction in survival. Further, resilience was not common, as 80.0% of populations that declined did not recover to before EWE levels while monitored. However, average monitoring time was only two years with over a quarter of studies tracking recovery for less than the study species generation time. We conclude that EWEs have positive and negative impacts on species demography, and this varies by taxa. Species population recovery over short‐time intervals is rare, but long‐term studies are required to accurately assess species resilience to current and future events.

Cloud cover changes driven by atmospheric circulation in Europe during the last decades

AbstractDue to its complex role within the radiation budget of the Earth, cloud cover plays an important role in climate variability at local, regional or continental scale. Consequently, there is a need for better understanding the causes and feedbacks of changes in cloud cover. We aim at investigating the response of cloud cover to changes in atmospheric circulation for 1981–2014. This is done based on the application of automated weather type classification from COST733 synoptic classifications software, which helps in identifying a variety of atmospheric circulation types for selected domains. Two major spatial changes in cloud cover over Europe are identified, in connection with atmospheric circulation, associated with the latitudinal shift towards the north of the westerly circulation. The first one is related to a decrease of the cloud cover over the inner continent and especially in the East of Europe in connection with an increase of circulation types associated with high pressures centers development over the central and northern part of the continent. The second one, which is weaker in intensity, indicates an increase of cloud cover in the south‐western part of Europe as a result of a decrease in circulation types induced by the development of the Azores High and its northeastward ridges. The changes in cloud cover distribution and also in radiation fluxes, imposed by these shifts in atmospheric circulation over the continent, are higher in the Eastern and Central Europe.

A GIS plugin to model the near surface air temperature from urban meteorological networks

This article proposes a QGIS plug-in called TempMap, to obtain near surface air temperature maps from an urban meteorological network, the topography description and three parameters describing the urbanized surface fraction. The objective being to facilitate the communication and consideration of local climate in French urban planning practices, some methodological choices were done related to the meteorological situation robustness, the choice of the mapped indicator and the availability of the surface data description. The plug-in allows to apply spatial analytical modelling based on a hybrid interpolation and is here applied to the CAPITOUL atmospheric database of Toulouse (France), the MApUCE urban database and the topographical information from the French National Geographical Institute to obtain air temperature maps for four Local Weather Types. The plug-in can be download from GitHub, is compatible with all QGIS versions since 2.14.12. The evaluation of the model results shows an accuracy comparable to the state-of-the-art with a maximum delta between predicted and observed values of ~1 °C. Here French datasets are used but alternative datasets can be used being also possible to modify the output resolution in order to fit the input data resolution and the needs of the study.

Design of an expert distance metric for climate clustering: The case of rainfall in the Lesser Antilles

To expand our knowledge of the climate in the Lesser Antilles, we attempted to identify the spatio-temporal configurations of daily weather. We noticed certain pitfalls that can lead to poor results when using clustering algorithms and have proposed some steps towards the solution. These advancements might prove interesting for climate informatics, as well as for many applications that cluster physical fields. We illustrated the pitfalls with a dataset of cumulative rainfall from NASA’s Tropical Rainfall Measuring Mission for the period 2000 to 2014. First, the pitfall is the lack of numerical evaluation of the clusters found by the algorithms, which prevents the comparison of algorithms. We used silhouette index for this evaluation and to demonstrate other problems. Second, algorithms like K-means cluster the points around their barycentre. For many physical fields, this barycentre is trivial, which may lead to poor performances. Third, the L2 norm used in conventional clustering methods, such as K-means and hierarchical agglomerative clustering, focus on the exact location of fields, which leads to poor evaluations of similarity between fields. We replaced it by a similarity measure called the expert distance (ED) that compares the histograms of four zones, based on the symmetrised Kullback–Leibler divergence. It integrates the properties of the observed physical parameter and climate knowledge. With these improvements, the results revealed five clusters with high indexes. The algorithms now discriminate the daily scenarios favourably, thereby providing more physical meaning to the resulting clusters. The interpretation of these clusters as weather types is discussed.

Analysis of Temperature Change in Uzbekistan and the Regional Atmospheric Circulation of Middle Asia during 1961–2016

Climate change and shrinking of the Aral Sea have significantly affected the region’s temperature variations. Observed interannual changes in Uzbekistan’s air temperature compared to the duration of synoptic weather types (SWT) in Middle Asia were analyzed. Nonparametric Mann–Kendall statistical test and climate trends coefficients were used to identify trend characteristics of observed temperature from 1961–2016 to the baseline period of 1961–1990. The results showed increasing temperature trends average to 1 °C in warm and cold half years over Uzbekistan. The 1991–2016 decadal temperature trend ranged from 0.25 °C/decade in the northwest to 0.52 °C/decade in the center, especially pronounced in the oasis and Aral Sea zones. There were also significant changes in the structure of regional SWT. The main difference in the structure of SWT in Middle Asia relative to the baseline period was expressed in a decrease of cold mass invasion duration from 113.4 to 76.1 days and an increase in low-gradient baric field duration from 65.8 to 134.6 days. The process of anthropogenic warming, which began in Uzbekistan in the 1960s of the twentieth century, has accelerated from the mid-1970s with a higher mean annual air temperature than the baseline period’s climate normals (1961–1990) and is associated with changes in the regional SWT over Middle Asia.

Продуцирование и энергетические показатели биогеоценозов полупустынь Ганых-Айричайской долины Азербайджана

The results of phytoproductivity in dynamics and some energy indicators of Artemisetum–Ephemerosum and Alhagietum–Artemisosum on the territory of the Ganykh–Airichai valley of Azerbaijan are presented. These are typical semi-desert cenoses. Analysis of quantitative indicators of energy consumption in plant communities over the period of research showed that 2 types of weather and climatic conditions determined 2 contrasting periods of development. Data on the aboveground and underground biomass in the studied communities are given. A comparative analysis has been carried out.

The use of weather types in the definition of seasons: the case of southern Balkans

The use of weather types for the definition of seasons is examined. Specifically, an objective definition of seasons is attempted for the southern Balkans based on the intra-annual variations of the frequencies of the objectively defined weather types. The methodology includes a combined application of Principal Component Analysis and k-means Cluster Analysis on daily grid point meteorological data obtained from the ERA5 database, for the 40-year period 1979–2018. The methodology is used at first for the classification of weather types and then for the definition of seasons based on the intra-annual variations of the weather types’ frequency. The application of the methodology results in nine weather types and four seasons. The characteristics of the defined weather types are connected to the prevalence of specific atmospheric circulation patterns, the windward or leeward character of the various sub-regions, and the thermal characteristics of the earth’s surface. The four seasons generally correspond to the conventional ones, but they present differences regarding their onset and cessation dates and their duration.