East Atlantic-West Russia Research Articles

Subseasonal variability of sea level pressure and its influence on snowpack over mid-high-latitude Eurasia during boreal winter

The atmospheric circulation significantly influences the snowpack over mid-high-latitude Eurasia. This study examines the characteristics of the leading subseasonal variability mode of boreal winter sea level pressure (SLP) with 20-80-day period and its relationship with snowpack over mid-high-latitude Eurasia, using the fifth generation of European Center for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA5) data and different snowpack datasets. The SLP leading mode, characterized by a monopole pattern with a strong surface anomalous high centered near the Ural Mountains, exhibits a barotropic structure and extends from the surface to the tropopause. Above SLP and geopotential height anomalies propagate southeastward from the Barents-Kara Sea to East Asia. This leading SLP mode contributes to surface air temperature (SAT) and snowfall circulation anomalies over mid-high-latitude Eurasia. The latter two both directly influence on snowpack anomalies in situ. Over high latitude region, snowfall circulation anomaly is the dominant factor to control the snow depth anomaly. Over middle latitude region, both SAT and snowfall circulation anomalies lead to the snowpack anomaly. Furthermore, the response of snow depth to the leading subseaonal SLP mode occurs 2–5 days earlier than the response of snow cover to the same mode over middle latitude region. In addition, it is suggested that the Arctic Oscillation (AO), East Atlantic/West Russia (EAWR) and Polar/Eurasia (PEU) pattern may contribute to the development of the leading SLP mode and subsequently influence snowpack anomalies.

Spatiotemporal variability and underlying large‐scale atmospheric mechanisms causing the change in the Black Sea surface temperature and associated extreme precipitation events in the northeastern of Turkiye

AbstractSea surface temperature (SST) has an important local and remote influence on global climate through the distribution and transport of heat and moisture. As a result of climate forcing, significant changes occur in the SSTs, which result in many natural disasters such as supercharged storms, higher wind speeds, heavier precipitation and flooding. This study investigates the spatiotemporal changes and underlying atmospheric mechanisms of the Black Sea (BLS) surface temperature. For this purpose, National Oceanicand Atmospheric Administration (NOAA) high‐resolution SST data (0.25°), which were verified with buoy observations, were used for the period 1982–2021. To investigate the circulation impacts, the relationship between North Atlantic Oscillation and East Atlantic/West Russia (EA/WR) phases and SSTs of the western BLS (WBLS) and eastern BLS (EBLS) was analysed. According to the results, SST values increased from 1.64°C (in winter) to 2.52°C (in summer) during the 40‐year period. Significant SST increases are shown in the EBLS during the summer and fall months. Statistically significant negative correlations (p < 0.05) were found between EA/WR and winter (r = −0.57) and summer (r = −0.56) SSTs in the EBLS. During winter, surface high located in the eastern Anatolia causes southerly winds, which blows from the terrestrial areas to the EBLS and result in above‐normal SST values. During summer (under negative EA/WR phases), the Azores high‐pressure centre extends to the Balkan Peninsula and WBLS and as a consequence, a significant amount of moisture associated with high sea surface temperature (>27°C, above‐normal 2.0°C) develops low‐level moisture convergence. Proper synoptic conditions, strong instability conditions between the surface and upper levels, and orographic forcing enable the occurrence of convective cloud cells. The movement of these cells to the northeastern part of Turkiye by strong northwesterly winds causes extreme precipitation and associated flash‐flood events in a limited area where land–sea interaction occurs (i.e., Artvin, Rize and Hopa provinces of Turkiye).

Exploring the spatial-temporal evolution characteristics of extreme heat events and driving factors in seven geographic regions of China (1980–2021)

Extreme heat events in China are occurring more frequently due to global warming. However, there is a lack of comprehensive studies analyzing the movement direction and factor interaction of extreme heat events in different regions of China. Based on daily temperature data from 2252 meteorological stations in China from 1980 to 2021, three extreme heat indicators were calculated: Hot days (SU35), Tropical nights (TR20), and Extreme maximum temperature (TXx). The study updated and compared the characteristics of spatiotemporal evolution and driving factors of extreme heat events in China and its seven geographical regions.The results show that: (1) SU35 and TR20 increase faster in summer, while TXx increases faster in winter. Nighttime high-temperature events have increased at a faster rate. (2) Extreme heat events in North, Northeast, and Northwest China have gradually moved southward and eastward, while in Central, East, and South China, such events have moved northward. (3) In northeast and northwest China, the Atlantic Multi-decadal Oscillation (AMO) is a strong driving force for extreme heat events, while urbanization is the most potent driving force in the remaining regions. The interaction between urbanization and atmospheric circulation, including AMO, Pacific Decadal Oscillation (PDO), and East Atlantic/West Russia (EA/WR), is non-linear or double factor enhancement and exhibits significant spatial heterogeneity. These results will be significant for urban adaptation to climate change and sustainable development.

Karadeniz'de 2000-2022 Yılları Arasında Yüzey Sıcaklığının Mekansal ve Zamansal Değişimi

This study presents a comprehensive assessment of the spatio-temporal variability of Sea Surface Temperature (SST) in the Black Sea at monthly to interannual scales, with a focus on understanding its connection to major large-scale atmospheric forcing during the period 2000-2022. Monthly variations of SST in the Black Sea reveal distinct seasonal patterns. The study evaluates the potential impacts of large-scale atmospheric patterns on interannual SST variations using climate indices such as the North Atlantic Oscillation (NAO), East Atlantic/West Russia (EA-WR) and El Niño-Southern Oscillation (ENSO) during the winter months. The results indicated that these large-scale atmospheric oscillations played a substantial role in influencing SST anomalies, with the NAO and EA-WR indices particularly affecting the Black Sea's SST anomalies. The NAO index exhibited negative values during warm winters and positive values during cold winters, with extreme cold and warm winters corresponding to specific years, as observed in 2003, 2006, 2012, 2017 (cold) and 2018, 2020, 2021 (warm). Notably, the relationship between NAO and SST anomalies was not as dominant during 2000-2022. This difference might be explained by the combined influence of NAO and ENSO, which is beyond the scope of this study. The EA-WR pattern was identified as another significant large-scale atmospheric dynamic affecting the Black Sea's SST. Although it explains the cold SST anomalies in certain years, it cannot account for extreme warm SST years. While the influence of ENSO remains somewhat inconclusive for the extreme warm period, the SST pattern between 2016-2022 aligns closely with El Niño events, particularly in 2018 and 2021 when positive SOI index values coincide with warm SST years in the Black Sea.

The increase in extreme precipitation and its proportion over global land

Changes in extreme precipitation (EP) have a significant impact on the ecology and sustainable development of most regions, especially when considered against a backdrop of global warming. Using trend analysis and other methods, we analyze the changes in nine extreme precipitation indices (EPIs), looking at the proportion of EP in total precipitation from the perspectives of intensity, frequency, and duration. We also utilize a geo-detector method to investigate the impacts of 15 climate factors on EPIs. Our results indicate that although EP and their proportions show an overall increasing trend on a global scale, they had undergone a process of initial decrease followed by increase over the past approximately 70 years. And this overall global increases are charged by the significant increases happened in Northern Hemisphere and western of South America, especially EP intensity and frequency indices, and their proportion. Whereas CDD shows an opposite trend in spatial distribution, the CWD is decreasing globally. The EPIs and their proportions are all highest in the low elevation belt (≤2000 m), followed by the high elevation belt (≥4000 m), and lowest in the mid-elevation belts (2000-4000 m). Most of them have returned to or exceeded the levels of the mid-20th century in all three elevation belts. Only CWD shows a decreasing trend, which indicates that more EP amounts are occurring with less precipitation duration. In some arid areas, this makes it possible that a short period of precipitation may complete the total amount of precipitation for that year. Global temperature is proven to be the most important factor influencing the EPI globally, and followed by the temperature of each region. And the regions of high latitudes of the Northern Hemisphere and Antarctica which are greatly influenced by global temperature demonstrate the Polar amplification effect. The East Atlantic-West Russia Pattern, Atlantic Multi-Decadal Oscillation, and El Nino-Southern Oscillation indices are the secondly important factors leading to changes in the proportion of global EP. At the same time, we also find that the influence of non-monsoon factors on EP is gradually strengthening. This study clarifies changes in EP globally and in various regions, which will help provide a scientific reference for preventing disasters caused by extreme climate change.

Winter particulate pollution severity in North China driven by atmospheric teleconnections

Elevated levels of particulate matter in the atmosphere are hazardous to human health and the environment. Severe particulate pollution days, with daily mean PM2.5 concentrations exceeding 150 μg m−3, occurred frequently in North China, especially during the boreal winters of 2013–2019. Severe particulate pollution generally occurs under conducive weather patterns characterized by a stable atmosphere with weak winds, under which air pollutants emitted at the surface by human activities would accumulate. The occurrence of conducive weather patterns has been attributed to variations in numerous climate factors such as Arctic sea-ice cover, sea surface temperature and atmospheric teleconnections, but the dominant climate drivers remain unclear. Here, we show that the East Atlantic–West Russia teleconnection pattern and the Victoria mode of sea surface temperature anomalies are the top two dominant climate drivers that lead to conducive weather patterns in North China through the zonal and meridional propagations of Rossby waves. Our results suggest that, with the help of seasonal forecast from climate models, indices of these two drivers can be used to predict severe particulate pollution over North China for the coming winter, enabling us to protect human health by air-quality planning.

Zonal shift in the cold airmass stream of the East Asian winter monsoon

The East Asian winter monsoon (EAWM) exhibits long-term variations in intensity and spatial pattern, though the latter one is less understood. To investigate the long-term spatial variations of the EAWM and their possible causes, we propose a new position index of the EAWM by quantifying the low-level East Asian stream (EAS) of cold airmass in the Lagrangian sense. Based on the new-defined index, we find that the EAS undergoes an evident zonal shift between two channels over the land and coast. At interdecadal timescale, the peak location of the EAS is displaced eastward, with an increasing southward cold airmass flux at the coast since the mid-1960s. The interannual shift of the EAS presents not only the zonal oscillation of peak location between two channels but also the width changes of coastal channel over the northwestern Pacific. These shifts in the EAS are related to the strength changes of two source cold airmass streams from Siberia or Bering Sea, which are associated with the phase changes in the upper-tropospheric atmospheric teleconnections. At interdecadal timescale, the phase change in the North Atlantic Oscillation modulates the zonal shift in the EAS via the East Atlantic-West Russia teleconnection. At interannual timescale, the Pacific/North American teleconnection becomes the dominant factor altering the zonal shift and width change of the EAS.

Mediterranean-Scale Drought: Regional Datasets for Exceptional Meteorological Drought Events during 1975–2019

Drought is one of the most complex climate-related phenomena and is expected to progressively affect our lives by causing very serious environmental and socioeconomic damage by the end of the 21st century. In this study, we have extracted a dataset of exceptional meteorological drought events between 1975 and 2019 at the country and subregional scales. Each drought event was described by its start and end date, intensity, severity, duration, areal extent, peak month and peak area. To define such drought events and their characteristics, separate analyses based on three drought indices were performed at 12-month timescale: the Standardized Precipitation Index (SPI), the Standardized Precipitation Evapotranspiration Index (SPEI), and the Reconnaissance Drought Index (RDI). A multivariate combined drought index (DXI) was developed by merging the previous three indices for more understanding of droughts’ features at the country and subregional levels. Principal component analysis (PCA) was used to identify five different drought subregions based on DXI-12 values for 312 Mediterranean stations and a new special score was defined to classify the multi-subregional exceptional drought events across the Mediterranean Basin (MED). The results indicated that extensive drought events occurred more frequently since the late 1990s, showing several drought hotspots in the last decades in the southeastern Mediterranean and northwest Africa. In addition, the results showed that the most severe events were more detected when more than single drought index was used. The highest percentage area under drought was also observed through combining the variations of three drought indices. Furthermore, the drought area in both dry and humid areas in the MED has also experienced a remarkable increase since the late 1990s. Based on a comparison of the drought events during the two periods—1975–1996 and 1997–2019—we find that the current dry conditions in the MED are more severe, intense, and frequent than the earlier period; moreover, the strongest dry conditions occurred in last two decades. The SPEI-12 and RDI-12 have a higher capacity in providing a more comprehensive description of the dry conditions because of the inclusion of temperature or atmospheric evaporative demand in their scheme. A complex range of atmospheric circulation patterns, particularly the Western Mediterranean Oscillation (WeMO) and East Atlantic/West Russia (EATL/WRUS), appear to play an important role in severe, intense and region-wide droughts, including the two most severe droughts, 1999–2001 and 2007–2012, with lesser influence of the NAO, ULMO and SCAND.

Variability of the precipitation over the Tianshan Mountains, Central Asia. Part II: Multi‐decadal precipitation trends and their association with atmospheric circulation in both the winter and summer seasons

AbstractThe annual precipitation over the Tianshan Mountains experienced an inter‐decadal transition shift towards an increasing trend in the late 1980s. This study conducts attribution analysis from atmospheric circulation factors based on the Global Precipitation Climatology Centre (GPCC) dataset and NCEP/NACR reanalysis data. The results show that (a) Winter precipitation in the Tianshan Mountains is affected by multi‐decadal oscillations with periods of 26.8 and 44.7 years, and has entered a period of positive anomalies after 1988. Although the non‐linear trend of winter precipitation in the Tianshan Mountains firstly increased and then decreased after 1979, the multi‐decadal fluctuation of precipitation caused the Tianshan Mountains in winter to be in a wet period from the 1980s until 2011. (b) We find that the East Atlantic‐West Russia (EATL/WRUS) teleconnection pattern has a similar multi‐decadal variability as Tianshan precipitation in winter. The wet period of Tianshan in winter after 1988 is mainly due to the enhanced meridional feature of the EATL/WRUS triggering more water vapour flux from low‐latitude oceanic areas. (c) Summer precipitation in the Tianshan Mountains has an obvious multi‐decadal scale of 33.5 years and shows a non‐linear growth trend. Tianshan Mountains in summer entered a humid period after 1986. (d) The Scandinavia (SCAND) teleconnection pattern represents important circulation variability affecting Tianshan summer precipitation. The vigorous high pressure over the Ural Mountains and the low pressure over Central Asia during the SCAND negative phase in summer jointly lead to enhanced moisture transport from the Arctic Ocean to the Tianshan Mountains. (e) Apart from SCAND, the Silk Road pattern (SRP) and East Asia‐Pacific teleconnection (EAP) also impacted Tianshan summer precipitation during the periods 1964–1984 and 1985–2004.

Relationships between Large-Scale Climate Signals and Winter Precipitation Amounts and Patterns over Iran

Precipitation is one of the most complex weather phenomena; its successful spatiotemporal modeling provides substantial information for designing water management systems. This research aimed to determine the relationship of sixteen large-scale climate signals with weather types (WTs) as well as precipitation amounts over Iran during the winter season (January–March). Daily precipitation data covering the period 1991–2010 were collected from 130 weather stations across the country. In addition, four atmospheric variables affecting the precipitation process over Iran were derived from National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis datasets as predictors. Several nonhomogeneous hidden Markov models (NHMMs) were employed to identify the prevailing WTs governing the spatial distributions of daily precipitation in winter over Iran. A hidden state (i.e., WTs) in NHMMs was dependent on an immediately previous state of WT in the hidden layer and the reanalyzed atmospheric variables at the current time in the predictor layer. Daily WTs over the recording period were decoded using Viterbi’s algorithm. Results showed that the NHMM including the atmospheric variable of mean sea level pressure (Mslp) in the predictor layer had the minimum value (= 0) of Bayesian information criterion difference (BICD) among the other variables and was treated as the best model. The chosen model distinguished the eight spatially coherent WTs for winter that were in accordance with the eight synoptic patterns influencing the study area. Based on the Spearman’s rank method, amounts of winter precipitation at many stations in Iran were significantly correlated with four climate signals, including the atlantic multidecadal oscillation (AMO), East Atlantic/West Russia (EA/WR) pattern, Southern Oscillation Index (SOI), and Trans Polar Index (TPI). However, these station-based relationships could not exhibit well the spatial dependencies of the teleconnections and regional precipitation. It was also found that the unconditional and conditional frequencies of WTs were under the influence of a greater number of large-scale climate signals than the precipitation amounts, were under the influence of a greater number of large-scale climate signals. Moreover, the inherent nature of WTs in keeping spatial dependencies allowed for a better understanding of regional teleconnective relationships. These findings confirmed the advantage of regional rather than local assessments of teleconnective relationships.

Statistical associations of teleconnection indices and space weather with spring weather pattern in the Eastern Baltic region

AbstractThe studies of associations between solar inputs and climate are mostly designed for winter or cold period; whereas the knowledge about these associations during spring on a day‐to‐day time scale are very scarce. Therefore, the aim of this study is to detect the response of spring air temperature (T), relative humidity (RH), and atmospheric pressure (ATP) to variation in teleconnection indices and space weather variables on the day‐to‐day timescale during the period of 1998–2017 in six cities of Eastern part of the Baltic region. We created a multivariate linear regression model for weather variables including month, the linear and seasonal trend, different teleconnection patterns, El Niño–Southern Oscillation, the Quasi‐biennial Oscillation phase, the presence of Sudden Stratospheric Warming (SSW) and space weather variables. The multivariate models for the mean daily weather variables showed a positive association between T and the daily Arctic oscillation, monthly Scandinavian pattern (SCA) indices, solar proton events (SPEs) with a lag of 1–9 days, and solar wind dynamic pressure (P) with a lag of 1–2 days and negative association between T and East Atlantic/West Russia (EA/WR) index. The mean RH positively correlated with a long‐term and short‐term variation in galactic cosmic rays (GCR) and solar wind speed (SWS) with a lag of 0–6 days and negatively correlated with EAWR and NINO3.4 indices. The mean ATP was negatively associated with both long‐term and short‐term changes in GCR and positively associated with the North Atlantic oscillation, EA/WR and SCA indices, By component of interplanetary magnetic field with a lag of 2 days, P, days of Stream Interaction Regions (SIRs) and SWS with a lag of 4–6 days. These results show the significant short‐term effects of SSW, SPEs, SIRs and solar wind variables on spring weather pattern in the Eastern part of the Baltic region.

Climatic Indices over the Mediterranean Sea: A Review

The Mediterranean Sea, strategically situated across a dynamic frontier line that separates two regions with different climates (Europe and North Africa), has been the focus of attention of many studies dealing with its thermohaline circulation, deep water formation processes or heat and freshwater budgets. Large-scale atmospheric forcing has been found to play an important role in these topics and attention has been renewed in climatic indices that can be used as a proxy for atmospheric variability. Among them, the North Atlantic oscillation, the East Atlantic or the East Atlantic–West Russia patterns have been widely addressed but much less attention has been devoted to a Mediterranean mode, the Mediterranean oscillation. This overview summarizes the recent advances that have been achieved in the understanding of these climatic indices and their influence on the functioning of the Mediterranean from a physical point of view. The important role of the Mediterranean oscillation is emphasized and the most relevant aspects of the other indices are revisited and discussed.

Spatiotemporal variability of summer precipitation and precipitation extremes and associated large-scale mechanisms in Central Asia during 1979–2018

The spatiotemporal variability of precipitation extremes dramatically affects various socio-economic activities in dryland. Based on the long-term and high-resolution daily precipitation obtained from the National Oceanic and Atmosphere Administration (NOAA) Climate Prediction Center (CPC), the total summer precipitation (TSP), precipitation extreme and persistent precipitation extreme (PPE) characteristics are revealed in Central Asia (CA) (34.3°N–55.4°N and 46.5°E–96.4°E) during 1979–2018. Results show that TSP, precipitation extreme and PPE in CA are significantly increased and the abrupt increasing occurred mainly in 1998. Additionally, proportion of precipitation extreme in TSP also increases. More significant positive trends of TSP, precipitation extreme and PPE occur in zones of northern Kazakhstan (NKZ) and Tienshan mountain range (TSM). Notably, although PEP in other regions exhibit indistinctive changes, PPE in some particular years abnormally frequent which may leads disasters. Further analyses indicate TSP and precipitation extreme in CA have significant positive correlation with the increasing water vapor transport from the southern boundary. Meanwhile, increasing horizontal moisture advection and enhanced vertical moisture advection, contributes to increasing in TSP and precipitation extreme in NKZ and TSM. In addition, negative phase of East Atlantic/West Russia (EA/WR) may result in the cyclone anomalous and deepened trough over CA, which cooperates with enhanced vertical advection and abnormal south moisture, finally provides favorable conditions for precipitation and precipitation extreme.

Spatiotemporal variability of daily precipitation concentration and its relationship to teleconnection patterns over the Mediterranean during 1975–2015

AbstractThis study has addressed the spatiotemporal distribution of the daily rainfall concentration and its relation to the teleconnection patterns across the Mediterranean (MR). Daily concentration index (CI) and the ordered n index ( nor) are used at annual time scale to reveal the statistical structure of precipitation across the MR based on 233 daily rainfall series for the period 1975–2015. Eight teleconnection patterns, North Atlantic Oscillation (NAO), Mediterranean Oscillation (MO), Western Mediterranean Oscillation (WeMO), Upper‐Level Mediterranean Oscillation index (ULMO), East Atlantic (EA) pattern, East Atlantic/West Russia (EATL/WRUS) pattern, Scandinavia (SCAND) pattern and Southern Oscillation (SO) at annual time scale are selected. The spatiotemporal patterns in precipitation concentration indices, annual precipitation and their teleconnections with previous large‐scale circulations are investigated. Results show a strong connection between the CI and the nor (r = 0.70, p < .05) which present the same relative areas of high and low concentration. The annual values range from 0.57 to 0.70 for CI and 0.49 to 0.71 for nor index which show a high daily precipitation concentration across the MR. Trend analysis demonstrated mostly significant increasing trends for both indices. This increase is mainly found in south France, northern coastlands of the Iberian Peninsula (IP), Greece and Tunisia. An inverse relationship between the number of rainy days and concentration indices is evident. Both of WeMO and MO can play an important role in modulating rainfall in the northwest Mediterranean. The positive EATL/WRUS phase is mainly connected with positive precipitation mean anomalies in the eastern Mediterranean and vice versa in the west. The high daily precipitation concentration values over south France, northeast Spain, Croatia and Tunisia are linked to the low values of WeMO and high values of EA. These results could pave the way for new possibilities regarding the projection of precipitation concentration and precipitation irregularity in downscaling techniques.

TRMM-based rainfall variability over the Central Mediterranean and its relationships with atmospheric and oceanic climatic modes

The seasonal rainfall variability over the Central Mediterranean area was studied in this research using the Tropical Rainfall Measurement Mission (TRMM) monthly product for the 20-years period 1998–2017, with emphasis given on the fresh water flux over the marine areas. The relationships with the principal atmospheric and oceanic climatic modes were also explored.Significant positive trends were detected over the Ionian Sea during the autumn and mild negative trends over the Northern Italy - Dinaric Alps, enhancing over the Northern Ligurian Sea. These tendencies were found to be regulated by the North Atlantic Oscillation (NAO), the Scandinavian (SCAND) pattern, and particularly by the Mediterranean evaporation under the influence of the increasing Mediterranean Sea Surface Temperature (SST) and the East Atlantic – West Russia (EAWR) pattern. On the contrary, significant negative trends were detected in the winter and spring rainfall over the Ionian and the Tyrrhenian Seas, and positive trends over the Southern Alps and the Adriatic Sea – Balkans area. These stresses were modulated by the combined effects of the SCAND, EAWR, and NAO during the winter, and also associated with the Mediterranean evaporation and SST during the spring under the influence of NAO and the East Atlantic pattern. During the summer mild negative trends were detected over the Tyrrhenian Sea and coherent rainfall variations with the increasing Mediterranean SST over the Ionian Sea. These tendencies seem to be associated with the prevalence of negative anomalies in the summer NAO.

Adriatic-Ionian air temperature and precipitation patterns derived from self-organizing maps: relation to hemispheric indices

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 78:149-163 (2019) - DOI: https://doi.org/10.3354/cr01565 Adriatic-Ionian air temperature and precipitation patterns derived from self-organizing maps: relation to hemispheric indices Frano Matić1,*, Hrvoje Kalinić2, Ivica Vilibić1, Branka Grbec1, Karla Morožin3 1Institute of Oceanography and Fisheries, 21000 Split, Croatia 2Faculty of Science, University of Split, 21000 Split, Croatia 3Department of Marine Studies, University of Split, 21000 Split, Croatia *Corresponding author: fmatic@izor.hr ABSTRACT: Normalized anomalies in air temperature and precipitation patterns derived from monthly data series collected at 28 in situ meteorological stations in the Adriatic-Ionian region between 1961 and 2015 were mapped by using the self-organizing map (SOM) method—an unsupervised neural network method—and connected with hemispheric indices in the atmosphere. Four indices were used: North Atlantic Oscillation (NAO), East Atlantic (EA), East Atlantic/West Russia (EAWR) and Scandinavian (SCA). Two experiments were conducted: the first combined normalized temperature anomalies with the indices, and the second combined normalized precipitation anomalies with the indices. Precipitation data better fit the SOM model than temperature data, while the SOM model has the best performance at a 3 × 3 matrix size. Region-wide negative precipitation anomalies are related to a combination of positive NAO and EAWR, and negative SCA indices, and vice versa. Positive air temperature anomalies are related to the positive EA index and vice versa. The mapped relations between the NAO index and precipitation anomalies indicate a nonlinear connection, because positive index values resemble 2 different precipitation patterns. The SOM-based nonlinear clustering might be useful in determining and forecasting precipitation and air temperature patterns from hemispheric indices. KEY WORDS: Self-organizing maps · Air temperature · Precipitation · Hemispheric indices · Central Mediterranean Full text in pdf format PreviousNextCite this article as: Matić F, Kalinić H, Vilibić I, Grbec B, Morožin K (2019) Adriatic-Ionian air temperature and precipitation patterns derived from self-organizing maps: relation to hemispheric indices. Clim Res 78:149-163. https://doi.org/10.3354/cr01565 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 78, No. 2. Online publication date: August 08, 2019 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 2019 Inter-Research.

Temporal disparity of the atmospheric systems contributing to interannual variation of wintertime haze pollution in the North China Plain

AbstractPrevious studies indicated that the meridional (northerly or southerly) wind anomalies over East China play an important role in modulating interannual variation of the winter haze pollution in the North China Plain (NCP) mainly via changing surface wind speed and humidity. Here, we report that the factors for the formation of the meridional wind anomalies over East China related to interannual variation of winter haze pollution experienced a significant interdecadal change around the mid‐1990s. Before the mid‐1990s, two upstream atmospheric wave trains contribute to generation of the meridional wind anomalies over East China via inducing significant geopotential height anomalies over northeast Asia. The first occurred over mid‐latitude Eurasia and propagated eastward into East Asia, resembling the East Atlantic‐west Russia (EAWR) pattern. The second propagated eastward along the subtropical Asian jet. Furthermore, during this period, the change in the intensity of East Asian trough (EAT) was closely linked with interannual variation of the winter haze variation in the NCP. By contrast, after the mid‐1990s, the atmospheric wave train along the Asian subtropical jet was not observed. Furthermore, the connection between the EAT intensity and the winter time NCP haze variation was weak. The mid‐latitude EAWR‐like pattern and the El Niño‐Southern Oscillation‐related sea surface temperature anomalies in the tropical Pacific were possible factors that explain the meridional wind anomalies over East China. Understanding the change in the atmospheric anomalies contributing to interannual variation of the haze is essential for the prediction of haze in the NCP.

Interannual variability of surface air temperature over mid-high latitudes of Eurasia during boreal autumn

This study analyzes the dominant modes of interannual variability of surface air temperature (SAT) during boreal autumn over the mid-high latitudes of Eurasia and investigates their associations with snow cover, atmospheric circulation and sea surface temperature (SST). The first, second and third empirical orthogonal function (EOF) mode of autumn SAT anomalies displays same-sign distribution, an east–west dipole pattern and a south–north dipole pattern, respectively. Analysis of surface heat fluxes indicates that snow changes explain only small patches of SAT anomalies related to the first two EOFs via altering surface shortwave radiation. Atmospheric circulation anomalies have important contributions to the formation of SAT anomalies. Southerly (northerly) wind anomalies generally favor positive (negative) SAT anomalies via bringing warmer (colder) air from lower (higher) latitudes. The atmospheric circulation anomalies related to the first EOF mode are attributed to a combination of the Arctic Oscillation (AO) and the Scandinavia pattern and those related to the second EOF mode have a close relation with the East Atlantic/West Russian (EAWR) and circumglobal teleconnection (CGT) patterns. Formation of the atmospheric circulation anomalies related to the third EOF mode is partly related to the Arctic sea ice change around the Barents–Kara Seas. SST anomalies have little contribution to the atmospheric circulation anomalies associated with the first three EOF modes of Eurasian autumn SAT interannual variations. Hindcast skill of the SAT anomalies related to the first (second) EOF mode is improved when taking both the AO and Scandinavia (EAWR and CGT) patterns into account.

Leading modes of interannual soil moisture variability in European Russia and their relation to regional climate during the summer season

Soil moisture (SM) data from the Global Land Evaporation Amsterdam Model dataset for 1980–2014 are used to investigate interannual variability of SM in European Russia during the summer season. An Empirical Orthogonal Function (EOF) analysis performed on monthly-mean data (i.e., separately for June, July and August) revealed three leading modes of SM variability, characterized by monopole (EOF-1), zonal dipole (EOF-2) and meridional dipole (EOF-3) patterns. Together these modes explain more than half of the total SM variability in each summer month. Analysis of correlations between the leading PCs (principal components) of SM in European Russia and indices of regional teleconnections suggests that the monopole pattern is associated with the Polar—Eurasia teleconnection, whereas the zonal and meridional dipole patterns are linked respectively to the East Atlantic—West Russia and Scandinavian teleconnections. These links are subject to change over the summer season. The leading PCs broadly capture the large SM anomalies associated with regional climate extremes (such as the Russian summer heat wave in 2010). Correlation analysis revealed generally consistent patterns in which positive (negative) SM anomalies are linked to cyclonic (anti-cyclonic) anomalies of sea level pressure, above (below) normal precipitation and negative (positive) anomalies of air temperature. Locally we find differing roles of air temperature and precipitation in land-atmosphere interaction. Specifically, while precipitation is the dominant driver of interannual SM variability in early summer, air temperature plays a larger role in late-summer land-atmosphere interaction (at some time scales) over the southern part of European Russia, where moisture availability is limited.

Analysis of the Variability of Wave Energy Due to Climate Changes on the Example of the Black Sea

An analysis of the variability of wave climate and energy within the Black Sea for the period 1960–2011 was made using field data from the Voluntary Observing Ship Program. Methods using wavelet analysis were applied. It was determined that the power flux of wave energy in the Black Sea fluctuates: the highest value is 4.2 kW/m, the lowest is 1.4 kW/m. Results indicate significant correlations among the fluctuations of the average annual wave heights, periods, the power flux of wave energy, and teleconnection patterns of the North Atlantic Oscillation (NAO), the Atlantic Multi-decadal Oscillation (AMO), the Pacific Decadal Oscillation (PDO) and the East Atlantic/West Russia (EA/WR). It was revealed that, in positive phases of long-term periods of AMO (50–60 years) as well as PDO, NAO, and AO (40 years), a decrease of wave energy was observed; however, an increase in wave energy was observed in the positive phase of a 15-year period of NAO and AO. The positive phase of changes of EA/WR for periods 50–60, 20–25, and 13 years led to an increase of wave energy. The approximation functions of the oscillations of the average annual wave heights, periods, and the power flux of wave energy for the Black Sea are proposed.