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The North Hemisphere winter stratosphere is frequently affected by large and rapid temperature increases, known as Sudden Stratospheric Warmings (SSWs). The strongest and most spectacular events, known as the Major Mid-Winter Warmings, cause a temporary reversal of climatological westerly zonal mean winds and, in some cases, even the breakup of the stratospheric polar vortex into several smaller vortices. The following downward propagation of stratospheric anomalies to the upper and middle troposphere has been associated with significant weather anomalies resembling a negative Northern Annular Mode (NAM) regime over Eurasia and North America. These events are often involved in winter weather extremes in Northern Hemisphere, therefore a better understanding of their occurrence and development could be helpful for the improvement of medium term forecast of extreme meteorological conditions.
In order to assess the impact of Sudden Stratospheric Warmings on surface weather conditions in central and eastern Europe, all major SSW events identified in the period 1979 – 2020 were classified in 5 major types using a k-means cluster analysis method. Then, in order to determine the changes in tropospheric circulation as an effect of each SSW, we identified the main weather circulation types in Europe by performing a cluster analysis of 500 hPa geopotential height and sea level pressure. After that, the changes in frequencies of these types, as well as the mean composite anomalies of the two aforementioned parameters were assessed. This has been done for three intervals: one month before and two months after a SSW event. The surface and lower troposphere impact was studied using the mean composite anomalies of several parameters: 2 m temperature, total precipitation amount, snowfall and snow depth, for the same intervals.
The results show a great deal of variability in the surface effects of SSW events. The general impact of SSW events consisted in a tendency towards a diminishing of the frequency of westerlies, and a subsequent increase in the frequency of both Mediterranean cyclones and high latitude blocking conditions, with their associated temperature and precipitation anomalies. Also, a second major output of the study indicates that in central and eastern Europe these SSW events lead to harsh winter conditions in 30% of cases, but also to abnormal warm winters intervals in other 25% of cases, depending on the type of the SSW. However, some events show a less marked impact on tropospheric weather, while other SSW do not propagate from the stratosphere to the upper and middle troposphere. Taking into account the type and characteristics of each SSW might significantly increase the predictability of their tropospheric effects.
Robert Hrițac; Lucian Sfîcă; Pavel Ichim. Tropospheric impact of Sudden Stratospheric Warmings in Central and Eastern Europe. 2021, 1 .
AMA StyleRobert Hrițac, Lucian Sfîcă, Pavel Ichim. Tropospheric impact of Sudden Stratospheric Warmings in Central and Eastern Europe. . 2021; ():1.
Chicago/Turabian StyleRobert Hrițac; Lucian Sfîcă; Pavel Ichim. 2021. "Tropospheric impact of Sudden Stratospheric Warmings in Central and Eastern Europe." , no. : 1.
This study was carried out in order to outline the human bioclimatic stress/comfort conditions within the area of Iași city, Romania. The meteorological data were obtained over a 7-year period (December 2012–November 2019) from an observation network relying on 8 fixed observation points located in selected spots, relevant for the urban climate conditions in the region. The results demonstrate firstly that throughout the entire analyzed period, using the thermo-hygrometric index (THI), “very cold” conditions characterize 4% of the entire year in the inner parts of the city and 6% in the rural area, while the “hot” THI conditions vary from 18% in the middle of the urban heat island to 15% in the rural area. Overall, the rural areas are generally more comfortable than the inner city, especially during summer, when the urban heat island (UHI) core is starting to develop from the evening and persists during the night. On the contrary, the UHI renders the inner city more comfortable than the rural surroundings from October to April. Similar bioclimatic conditions are also presented in detail for the summer by the relative strain index (RSI), which exceeds the stress threshold value mostly during heat waves, when a significant contrast between urban and rural areas is felt. In brief, it has been determined that the most suitable area for human comfort in Iași city is inside the urban area during the winter and in the rural areas during the summer.
Pavel Ichim; Lucian Sfîcă. The Influence of Urban Climate on Bioclimatic Conditions in the City of Iași, Romania. Sustainability 2020, 12, 9652 .
AMA StylePavel Ichim, Lucian Sfîcă. The Influence of Urban Climate on Bioclimatic Conditions in the City of Iași, Romania. Sustainability. 2020; 12 (22):9652.
Chicago/Turabian StylePavel Ichim; Lucian Sfîcă. 2020. "The Influence of Urban Climate on Bioclimatic Conditions in the City of Iași, Romania." Sustainability 12, no. 22: 9652.
The paper presents the main features of the urban heat island of Galați city during the summer season for a period of 16 years (2003-2018) using MODIS products. The main objectives were to analyse the extension and geometry of the urban heat island (UHI), its intensity, as well as its connection with land cover. The study is based on LST (Land Surface Temperature), a product obtained from Moderate Resolution Imaging Spectroradiometer (MODIS) sensors located on board of the Terra (EOS AM-1) satellite since 2001 and Aqua (EOS PM-1) satellite since 2003. The boundaries, geometry and spatial extent of the UHI were delimited primarily through the Rodionov test. Through this method, the changing points along four transects over Galați city were identified (North-South, East-West, Northeast-Southwest and Northwest-Southeast) and have been used to delimitate the UHI. Overall, the Galați UHI assessed by satellite information is stronger during the day when the UHI is split in two centres, developed over the industrial area in the west and over the residential part of the town in the east, while during the night the UHI is weaker being developed more clearly over the oldest part of the city. One of the major characteristics of the Galați UHI is that it is highly influenced by the water bodies encircling the city. During the day the intensity of UHI reaches 2-2.5°C while during the night decreases below 2.0°C. The relation of the UHI with land cover and the attenuation of UHI in the surrounding area are also investigated.
Ștefănel–Claudiu Crețu; Pavel Ichim; Lucian Sfîcă. SUMMER URBAN HEAT ISLAND OF GALAȚI CITY (ROMANIA) DETECTED USING SATELLITE PRODUCTS. Present Environment and Sustainable Development 2020, 14, 5 -27.
AMA StyleȘtefănel–Claudiu Crețu, Pavel Ichim, Lucian Sfîcă. SUMMER URBAN HEAT ISLAND OF GALAȚI CITY (ROMANIA) DETECTED USING SATELLITE PRODUCTS. Present Environment and Sustainable Development. 2020; 14 (2):5-27.
Chicago/Turabian StyleȘtefănel–Claudiu Crețu; Pavel Ichim; Lucian Sfîcă. 2020. "SUMMER URBAN HEAT ISLAND OF GALAȚI CITY (ROMANIA) DETECTED USING SATELLITE PRODUCTS." Present Environment and Sustainable Development 14, no. 2: 5-27.
The aim of this study is to evaluate the role of the weather conditions and local climate on the temporal and spatial variability of particulate matters (PM 10) in Iași city which is facing major pollution problems in the recent years. Daily data from 4 monitoring stations of Environmental Protection Agency-Iași–for main weather parameters and particulate matters – and the temperature from an inner temperature and relative humidity observation network inside the city were used for a three year study (2013-2015). Linear correlation, composite analysis and multiple regression are the main statistical methods applied in the analysis. In brief, the most important meteorological parameters enhancing air pollution in Iași seem to be represented by thermal inversions developing in the region strongly related to local climate conditions. The Pearson correlation coefficient (stronger than -0.40) between PM10 and thermal gradient, the difference in the PM10 concentration exceeding 20 μg/m3 between strong thermal inversions and unstable conditions and the leading role of thermal gradients in multiple regression are the main indicators of the great role of thermal inversion in generating and sustaining pollution conditions in this area. The maximum concentrations of PM10 occur in May and March, gathering more than 30% of the days for the entire year. Complementary studies were taken into account in order to analyse the aerosol optical properties retrieved from Aerosol Robotic Network (AERONET-NASA).
Lucian Sfîcă; Iulian Iordache; Pavel Ichim; Alina Leahu; Marius-Mihai Cazacu; Silviu Gurlui; Cătălin-Răzvan Trif. The Influence of Weather Conditions and Local Climate on Particulate Matter (PM10) Concentration in Metropolitan Area of Iasi, Romania. Present Environment and Sustainable Development 2018, 12, 47 -69.
AMA StyleLucian Sfîcă, Iulian Iordache, Pavel Ichim, Alina Leahu, Marius-Mihai Cazacu, Silviu Gurlui, Cătălin-Răzvan Trif. The Influence of Weather Conditions and Local Climate on Particulate Matter (PM10) Concentration in Metropolitan Area of Iasi, Romania. Present Environment and Sustainable Development. 2018; 12 (2):47-69.
Chicago/Turabian StyleLucian Sfîcă; Iulian Iordache; Pavel Ichim; Alina Leahu; Marius-Mihai Cazacu; Silviu Gurlui; Cătălin-Răzvan Trif. 2018. "The Influence of Weather Conditions and Local Climate on Particulate Matter (PM10) Concentration in Metropolitan Area of Iasi, Romania." Present Environment and Sustainable Development 12, no. 2: 47-69.
The study underlines the characteristics of the urban heat island of Iași (Iași’s UHI) on the basis of 3 years of air temperature measurements obtained by fixed-point observations. We focus on the identification of UHI development and intensity as it is expressed by the temperature differences between the city centre and the rural surroundings. Annual, seasonal and daily characteristics of Iaşi’s UHI are investigated at the level of the classical weather observation. In brief, an intensity of 0.8 °C of UHI and a spatial extension which corresponds to the densely built area of the city were delineated. The Iaşi UHI is stronger during summer calm nights—when the inner city is warmer with 2.5–3 °C than the surroundings—and is weaker during windy spring days. The specific features of Iași’s UHI bear a profound connection to the specificity of the urban structure, the high atmospheric stability in the region and the local topography. Also, the effects of Iași’s UHI upon some environmental aspects are presented as study cases. For instance, under the direct influence of UHI, we have observed that in the city centre, the apricot tree blossoms earlier (with up to 4 days) and the depth of the snow cover is significantly lower (with up to 10 cm for a rural snow depth of 30 cm) than in the surrounding areas.
Lucian Sfîcă; Pavel Ichim; Liviu Apostol; Adrian Ursu. The extent and intensity of the urban heat island in Iași city, Romania. Theoretical and Applied Climatology 2017, 134, 777 -791.
AMA StyleLucian Sfîcă, Pavel Ichim, Liviu Apostol, Adrian Ursu. The extent and intensity of the urban heat island in Iași city, Romania. Theoretical and Applied Climatology. 2017; 134 (3-4):777-791.
Chicago/Turabian StyleLucian Sfîcă; Pavel Ichim; Liviu Apostol; Adrian Ursu. 2017. "The extent and intensity of the urban heat island in Iași city, Romania." Theoretical and Applied Climatology 134, no. 3-4: 777-791.
Radu-Vlad Dobri; Lucian Sfîcă; Pavel Ichim; Gabriela-Victoria Harpa. The Distribution of the Monthly 24-Hour Maximum Amount of Precipitation in Romania According to their Synoptic Causes. Geographia Technica 2017, 12, 62 -72.
AMA StyleRadu-Vlad Dobri, Lucian Sfîcă, Pavel Ichim, Gabriela-Victoria Harpa. The Distribution of the Monthly 24-Hour Maximum Amount of Precipitation in Romania According to their Synoptic Causes. Geographia Technica. 2017; 12 (2):62-72.
Chicago/Turabian StyleRadu-Vlad Dobri; Lucian Sfîcă; Pavel Ichim; Gabriela-Victoria Harpa. 2017. "The Distribution of the Monthly 24-Hour Maximum Amount of Precipitation in Romania According to their Synoptic Causes." Geographia Technica 12, no. 2: 62-72.
This study is based on 3 years of hourly observations of global solar radiation (2014-2016), at a new weather station installed in the region of Central Moldavian Plateau, at Mădârjac (47.05°N, 27.25°E, 270 m). The main characteristics of annual, monthly and daily regime of global radiation were emphasized using for comparison similar data from Iașioficial weather station. Smaller annual amount of global solar radiation than those observed in previous studies were observed, reaching 4734 MJ/m2 in Iași and 4454 MJ/m2 in Mădârjac. An altidudinal gradient of global solar radiation close to 140 MJ/m2 was identified for the hilly region of Moldova. Despite the overall higher values in Iași, 30% of days indicates higher values of this parameter at Mădârjac weather station. These results can be used for the evaluation of the photo-voltaic potential in the region, but also to understand the altitudinal differences of solar radiation in the hilly region in Moldavia, since the only long-range actinometric stations from this part of Romania, Iași and Galați, are located at low altitudes.
Lucian Sfîcă; Pavel Ichim; Liviu Apostol; Ovidiu Machidon. Three Years of Observations on Global Solar Radiation at Mădârjac Weather Station (270 m) - Central Moldavian Plateau. Present Environment and Sustainable Development 2017, 11, 109 -117.
AMA StyleLucian Sfîcă, Pavel Ichim, Liviu Apostol, Ovidiu Machidon. Three Years of Observations on Global Solar Radiation at Mădârjac Weather Station (270 m) - Central Moldavian Plateau. Present Environment and Sustainable Development. 2017; 11 (2):109-117.
Chicago/Turabian StyleLucian Sfîcă; Pavel Ichim; Liviu Apostol; Ovidiu Machidon. 2017. "Three Years of Observations on Global Solar Radiation at Mădârjac Weather Station (270 m) - Central Moldavian Plateau." Present Environment and Sustainable Development 11, no. 2: 109-117.
Temperature inversions represent complex phenomena, specific for depression forms of relief which introduce changes in vertical zoning (Apăvăloae, Apostle, Pîrvulescu, 1986 by stable air stratification (Erhan, 1981), because of their morphological features, this is due to the interdependence of general movement and characteristics of the active surface, being the cause of their production (Apăvăloae, et. al., 1984, 1986, 1987). The generation of thermal inversions, their intensity and frequency is a consequence of altitude topography, morphology, fragmentation, orientation and degree of closure to external drives. (Apăvăloae, Apostle, Pîrvulescu, 1988). Thermal inversions represent complex phenomena, specific to depression landforms that introduce changes within the vertical zoning (Apăvăloae, Apostol, Pîrvulescu, 1986) by stable air stratification (Matveev, 1958, Erhan, 1981, Yinghui Liu, 2002) where vertical thermal gradient is negative (Matveev, 1958), due to their morphological features, also as a consequence of the interdependance of general circulation and characteristics of the active surface, the cause of their generation (Apăvăloae, et. al., 1984, 1986, 1987).
Pavel Ichim; Liviu Apostol; Lucian Sfîcă; Adriana-Lucia Kadhim-Abid; Vasilică Istrate. Frequency of Thermal Inversions Between Siret and Prut Rivers in 2013. Present Environment and Sustainable Development 2014, 8, 267 -284.
AMA StylePavel Ichim, Liviu Apostol, Lucian Sfîcă, Adriana-Lucia Kadhim-Abid, Vasilică Istrate. Frequency of Thermal Inversions Between Siret and Prut Rivers in 2013. Present Environment and Sustainable Development. 2014; 8 (2):267-284.
Chicago/Turabian StylePavel Ichim; Liviu Apostol; Lucian Sfîcă; Adriana-Lucia Kadhim-Abid; Vasilică Istrate. 2014. "Frequency of Thermal Inversions Between Siret and Prut Rivers in 2013." Present Environment and Sustainable Development 8, no. 2: 267-284.