Search

The mean weight-at-age of fish species is an indicator of fish growth and physiological condition, as well as a basic parameter for assessing and managing fish stocks. Here, we investigate the temporal trends of the mean weight-at-age of four different commercial species with different life strategies: (i) the short-lived pelagic European sardine (Sardina pilchardus), (ii) the horse mackerel (Trachurus trachurus) and two medium-lived benthic, (iii) the megrim (Lepidorhombus whiffiagonis) and iv) the four-spotted megrim (Lepidorhombus boscii), in North Atlantic Iberian waters from 2000 to 2018. Generalised additive models were implemented to identify the main (density-dependent and density-independent) drivers of fish weight-at-age variability: abundance, sex, maturity, sea surface temperature, sea bottom temperature, North Atlantic Oscillation (NAO) and Atlantic Multidecadal Oscillation indices. In all four species, abundance had a negative effect on mean weight-at-age. Temperature affected mean weight-at-age in sardine and megrim, while NAO influenced it in horse mackerel and four-spotted megrim. In the case of the sardine, we observed a progressive decrease in the mean weight-at-age of adults in the series in contrast to the four-spotted megrim; however, there was no effect of year on either horse mackerel or megrim. We discuss the influence of life strategy on fish response to drivers. [ABSTRACT FROM AUTHOR]

The Central-Pacific (CP) and Eastern-Pacific (EP) types of El Niño-Southern Oscillation (ENSO) and their ocean–atmosphere effect cause diverse responses in the hydroclimatological patterns of specific regions. Given the impact of ENSO diversity on the North Atlantic Oscillation (NAO), this study aimed to determine the relationship between the ENSO-NAO teleconnection and the ENSO-influenced precipitation patterns in Colombia during the December–February period. Precipitation data from 1981 to 2023, obtained from the Climate Hazards Group (CHIRPS), were analyzed using nine ENSO and NAO indices spanning from 1951 to 2023. Using Pearson's correlation and mutual information (MI) techniques, nine scenarios were devised, encompassing the CP and EP ENSO events, neutral years, and volcanic eruptions. The results suggest a shift in the direction of the ENSO-NAO relationship when distinguishing between the CP and EP events. Higher linear correlations were observed in the CP ENSO scenarios (r > 0.65) using the MEI and BEST indices, while lower correlations were observed when considering EP events along with the Niño 3 and Niño 1.2 indices. MI show difference in relationships based on the event type and the ENSO index used. Notably, an increase in the non-linear relationship was observed for the EP scenarios with respect to correlation. Both teleconnections followed a similar pattern, exhibiting a more substantial impact during CP ENSO events. This highlights the significance of investigating the impacts of ENSO on hydrometeorological variables in the context of adapting to climate change, while acknowledging the intricate diversity inherent to the ENSO phenomenon. [ABSTRACT FROM AUTHOR]

During early boreal winter, the extratropical atmospheric circulation is influenced by Rossby waves propagating from the Indian Ocean toward the North Atlantic–European (NAE) regions, resulting in a North Atlantic Oscillation (NAO)-like pattern. The mechanisms driving these teleconnections are not well understood and are crucial for improving model skills. This study investigates these mechanisms using the ERA5 dataset and tests the predictive capabilities of the ECMWF SEAS5, exploring potential reasons for a weak model response. Linear regression methods are employed to examine the extratropical links with the Indian Ocean dipole (IOD), both in isolation and in combination with El Niño–Southern Oscillation (ENSO). Our findings demonstrate a connection between October IOD sea surface temperature anomalies and December Indian Ocean precipitation patterns. Furthermore, a correlation between the October IOD and December NAO time series suggests a link between the IOD and NAE circulation. The early winter European response to a positive IOD is characterized by a north–south precipitation dipole and a large positive surface air temperature anomaly. Positive feedback from transient eddy forcing reinforces the wavenumber-3-like propagation across extratropical regions, with ENSO playing a minor role compared to the IOD. This phenomenon is particularly evident in regions such as the North Pacific and North Atlantic, where wave energy propagation is intensified. Although SEAS5 replicates the NAO response, its magnitude is significantly weaker. The model struggles to simulate the delayed rainfall dipole response to the IOD accurately and shows structural discrepancies compared to reanalysis data. [ABSTRACT FROM AUTHOR]

Since 1993, Satellite Altimetry greatly enhanced the ability to study and understand ocean dynamics, particularly in the context of climate change. Though relatively low-energy and understudied, the Northeast Tropical Atlantic Ocean (NTAO) plays a crucial role in the Earth's climate system. This study aims to deepen understanding of the NTAO region using the satellite altimetry-derived daily sea level gridded data set provided by the Copernicus Climate Change Service (C3S). The analysis of long-term regional Sea Level Anomaly (SLA) signals in the NTAO reveals a higher rate of sea level rise compared to the global average. The same analysis for regional Eddy Kinetic Energy (EKE) per unit mass and surface geostrophic currents shows declining rates, in contrast to global counterparts. Correlation analysis between SLA and climate indices (CI) uncovered significant links with the North Atlantic Oscillation, Tropical North/South Atlantic, Western Hemisphere Warm Pool, and Southern Oscillation Index. Composite maps of sea surface temperature (SST), sea level pressure (SLP), and wind anomalies, as well as complementary maps with anomalies of SLA, EKE, and ocean circulation, were examined to understand the primary mechanisms behind these correlations. SST emerged as the main forcing factor, with SLP and wind anomalies also contributing to specific regional and index correlations. EKE anomalies further elucidate differences in the anomalies of the surface geostrophic currents in the areas influenced by the key currents in the study region. The findings of this study show an intricate interplay between oceanic dynamics and climate phenomena, shedding light on the complex mechanisms driving changes in the Northeast Tropical Atlantic Ocean. [ABSTRACT FROM AUTHOR]

Ecosystem services provided by terrestrial biomes, such as moisture recycling and carbon assimilation, are crucial components of the water, energy, and biogeochemical cycles. These biophysical processes are influenced by climate variability driven by distant ocean-atmosphere interactions, commonly referred to as teleconnections. This study aims to identify which teleconnections most significantly affect key biophysical processes in South America's two largest biomes: The Amazon and Cerrado. Using 20 years of monthly data on Precipitation (P), Evapotranspiration (ET), Gross Primary Productivity (GPP), and Ecosystem Water Use Efficiency (EWUE), alongside data from six teleconnections (Antarctic Oscillation - AAO, Atlantic Multidecadal Oscillation - AMO, Oceanic Niño Index - ONI, Atlantic Meridional Mode - AMM, North Atlantic Oscillation - NAO, and Pacific Decadal Oscillation - PDO), we developed a multivariate linear model to assess the relative importance of each teleconnection. Additionally, time-lagged Spearman correlations were used to explore relationships between biophysical variables and teleconnections. Our findings indicate that the AMO exerts the strongest influence across all studied variables. Furthermore, ONI and AMM significantly impact precipitation in the northern Amazon, with a 3-month lag in ONI showing positive correlations with ET and GPP. In contrast, a 3-month lag in AMO negatively influences GPP in the southern Amazon and Cerrado, though positive correlations with EWUE were observed in the same region. These insights highlight the complex and regionally varied impacts of teleconnections on South America's largest biomes. [ABSTRACT FROM AUTHOR]

The timing of migration is fundamental for species exploiting seasonally variable environments. For ungulates, earlier spring migration is expected with earlier vegetation green-up. However, other drivers, such as access to agricultural farmland and variation in local conditions, are also known to affect migration. We investigated the timing of spring migration for 96 male and 201 female red deer (Cervus elaphus) using a long-term dataset (2005–2020). Overall, the timing of migration was mainly characterized by large individual variability between and within years (95% range 6 April to 18 June). The spring migration timing was, as expected, later with colder winter and spring conditions (North Atlantic Oscillation (NAO) winter and April indices) and later peak vegetation green-up (NDVI), with a five-day delay in green-up causing a migration delay of 1.2 days. Timing was also influenced by local conditions in summer and winter home ranges. Red deer with greater access to farmland and a more variable topography (hence variable plant phenology) in winter delayed migration. Similarly, individuals with higher-elevation summer ranges (with delayed onset of plant growth) also delayed migration. Our analyses highlight that the timing of red deer migration is determined by multiple drivers affecting foraging conditions in the landscape, indicative of considerable phenotypic plasticity. [ABSTRACT FROM AUTHOR]

Over the subtropical Northeast Pacific (NEP), highly reflective low clouds interact with underlying sea surface temperature (SST) to constitute a local positive feedback. Recent modeling studies showed that, together with wind–evaporation–SST (WES) feedback, the summertime low cloud–SST feedback promotes nonlocal trade wind variations, modulating subsequent evolution of El Niño–Southern Oscillation (ENSO). This study aims to identify drivers of summertime low-cloud variations, using satellite observations and global atmosphere model simulations forced with observed SST. A transbasin teleconnection is identified, where the north tropical Atlantic (NTA) warming induced by the North Atlantic Oscillation (NAO) increases precipitation, exciting warm Rossby waves that extend into the NEP. The resultant enhancement of static stability promotes summertime low cloud–SST variability. By regressing out the effects of the preceding ENSO and NTA SST, atmospheric internal variability over the extratropical North Pacific, including the North Pacific Oscillation (NPO), is found to drive the NEP cooling by latent heat loss and subsequent summer low cloud–SST variability. With the help of the background trade winds and WES feedback, the SST anomalies extend southwestward from the low-cloud region, accompanied by ENSO in the following winter. This suggests the nonlocal effects of low clouds identified by recent studies. Analysis of a 500-yr climate model simulation corroborates the NTA and NPO forcing of NEP low cloud–SST variability and subsequent ENSO. [ABSTRACT FROM AUTHOR]

The Mongolian Plateau grassland (MPG) is critical for ecological conservation and sustainability of regional pastoral economies. Aboveground net primary productivity (ANPP) is a key indicator of grassland health and function, which is highly sensitive to variabilities in large-scale atmospheric circulations, commonly referred to as teleconnections (TCs). In this study, we analyzed the spatial and temporal variations of ANPP and their response to local meteorological and large-scale climatic variabilities across the MPG from 1982 to 2015. Our analysis indicated the following: (1) Throughout the entire study period, ANPP displayed an overall upward trend across nine ecoregions. In the Sayan montane steppe and Sayan alpine meadow ecoregions, ANPP displayed a distinct inflection point in the mid-1990s. In the Ordos Plateau arid steppe ecoregion, ANPP continuously increased without any inflection points. In the six other ecoregions, trends in ANPP exhibited two inflection points, one in the mid-1990s and one in the late-2000s. (2) Precipitation was the principal determinant of ANPP across the entire MPG. Temperature was a secondary yet important factor influencing ANPP variations in the Ordos Plateau arid steppe. Cloud cover affected ANPP in Sukhbaatar and central Dornod, Mongolia. (3) The Atlantic Multidecadal Oscillation affected ANPP by regulating temperature in the Ordos Plateau arid steppe ecoregion, whereas precipitation occurred in the other ecoregions. The Pacific/North America, North Atlantic Oscillation, East Atlantic/Western Russia, and Pacific Decadal Oscillation predominantly affected precipitation patterns in various ecoregions, indicating regional heterogeneities of the effects of TCs on ANPP fluctuations. When considering seasonal variances, winter TCs dominated ANPP variations in the Selenge–Orkhon forest steppe, Daurian forest steppe, and Khangai Mountains alpine meadow ecoregions. Autumn TCs, particularly the Pacific/North America and North Atlantic Oscillation, had a greater impact in arid regions like the Gobi Desert steppe and the Great Lakes Basin desert steppe ecoregions. This study's findings will enhance the theoretical framework for examining the effects of TCs on grassland ecosystems. [ABSTRACT FROM AUTHOR]

Atmosphere-ocean interactions are understood to significantly modulate climate variability and ocean circulation patterns. In this study, the influence of climate oscillations, particularly the North Atlantic Oscillation (NAO) and the El Niño-Southern Oscillation (ENSO), on the circulation dynamics of the Gulf of Mexico (GoM) is investigated. Empirical Orthogonal Function (EOF) analysis was used to identify the principal modes of variability in the GoM circulation, and cross-spectral analysis was conducted to examine the coherence between the GoM circulation, NAO, and ENSO indices. The results reveal that Gulf of Mexico circulation patterns share significant frequencies with both NAO and ENSO. These shared frequencies suggest synchronization phenomena between NAO, ENSO, and the Atlantic Meridional Overturning Circulation (AMOC), indicating a strong influence of these climate oscillations on the GoM's circulation. Key frequencies observed include a near 7-year period aligning with ENSO's natural variability and semiannual periods linked to NAO and the Madden-Julian Oscillation (MJO). These climate oscillations are found to modulate heat transfer intensity in the GoM, influencing large-scale ocean-atmosphere interactions. The findings highlight the critical role of NAO-ENSO teleconnections in shaping GoM circulation variability and their broader implications for global oceanic heat transport mechanisms. [ABSTRACT FROM AUTHOR]

The reconstruction of flood frequency beyond the Instrumental Era is challenging and mostly based on historical sources, but it rarely covers more than the last 1000 years when abundant documentation is preserved. To investigate the long‐term trends in flooding and obtain insight into current climatic changes it is necessary to extend these data to a larger number of rivers beyond the Instrumental Era and available period of historical documentation. In this paper we reconstruct the paleoflood record for the Roman Period of the Serchio River (Auser in antiquity, located in Northern Tuscany, Central Italy) using geoarcheological data. The complex hydrological evolution of the river and the development of the important cities of Lucca and Pisa on the river bank allowed an important collection of data, showing a prominent peak in flood activity during the 1st century ce, which seems to correspond to an increase in regional rainfall interpreted from speleothem proxies. A secondary peak is present in the 6th century ce, which corresponds locally with an increase in precipitation recorded by speleothems. The phases of increased flooding, when compared with present‐day synoptical meteorological conditions, probably developed during a period of negative North Atlantic Oscillation (NAO) Index, and it is partially supported by comparison with paleoproxies for NAO. These findings confirm that an extensive collection of geoarcheological data, supported by geological and geomorphological investigation, represents a powerful tool to be integrated with historical data for the reconstruction of floods. The concomitance of local paleohydrological proxies can help in disentangling the origin of the signal from other causes. [ABSTRACT FROM AUTHOR]

In a routine search for meteorological events with a great impact on society in the Extremadura region (southwest interior of the Iberian Peninsula) using newspapers, the month of June 1925 was detected as exceptional due to the large number of thunderstorms associated with significant losses of human lives and material resources. This extraordinary month underwent a detailed examination from various complementary perspectives. Firstly, we reconstructed the history of the events, considering the most impacted locations and the resulting damage. Periodical publications, especially the widely circulated Extremadura newspaper in 1925, were pivotal in this regard. Secondly, we scrutinized monthly meteorological variables (precipitation, temperature, and cloudiness) using the lengthiest-available data series from the Iberian Peninsula. This aimed to underscore the exceptional characteristics of June 1925. Lastly, we analyzed the synoptic situation of the thunderstorm events by employing National Oceanic and Atmospheric Administration/Cooperative Institute for Research in Environmental Sciences/Department of Energy (NOAA/CIRES/DOE) 20th Century Reanalysis V3 (20CR) data. This approach allowed us to comprehend, from a synoptic perspective, the exceptional nature of this month. Thereby, a combination of a negative North Atlantic Oscillation (NAO) situation, elevated convective available potential energy (CAPE) values, large-scale lifting, and abundant precipitable water availability in the region was revealed. [ABSTRACT FROM AUTHOR]

Based on the daily minimum temperature station data provided by the National Meteorological Information Centre from 1980 to 2022， the month-by-month reanalysis data of the NCEP/NCAR， and the monthly Sea Surface Temperature （SST） data from the NOAA， by using EOF， simple linear regression and T-N wave flux methods， the main anomalous spatial and temporal characteristics of winter cold wave frequency in the southern China are studied， and the influence mechanisms of atmospheric circulation and winter Atlantic Sea Surface Temperature Anomaly （SSTA） on it are also analyzed.The results show that： （1） The large value areas of winter cold wave frequency are mainly located in the eastern and central of the southern China， with an approximately "inverse C" distribution.There are three main frequency anomalous modes， namely， regionally consistent anomaly， north-south antiphase anomaly and tripole anomaly patterns according to the EOF analysis， among which the regionally consistent anomaly reflects the overall anomalous spatial and temporal characteristics of the winter cold wave frequency in the southern China.（2） The negative phase of the North Atlantic Oscillation （NAO）， the strong Caspian Sea - Tibetan Plateau ridge and the East Asian Trough located to the north and to the east， the weak in the north and strong in the south of the Siberian High， the strong temperate jet and the weak subtropical jet are the key circulation systems affect the winter cold wave frequency in the southern China.The cold air pool is located in the Western Siberia.The high and low level circulation systems cooperate together to make the cold air from Western Siberia move southward to the vicinity of the Caspian Sea， and then transport eastward along the northern side of the Tibetan Plateau， then move southward into the southern China along the eastern side of the Tibetan Plateau， resulting in the increase of the winter cold wave frequency in the whole southern China.（3）In winter， the “+”“-”“+” tripolar SSTA in the North Atlantic can stimulate the -NAO atmospheric circulation anomalies through the exchange of heat fluxes between air and sea and the Rossby wave energy anomalies.The Rossby wave energy propagates from the North Atlantic to East Asia along the south and north two paths， and stimulates the corresponding anomalous waves， which enhance the key circulation systems in the north and south affecting the cold wave frequency in the southern China.When the North Atlantic SSTA exhibits an inverse "C" anomaly in spring， and there is a trend of developing into a “+”“-”“+” tripolar pattern in summer and autumn， the winter cold wave frequency in the southern China can be predicted to more.

The interannual‐to‐decadal variability of sea surface temperature and height in the North Atlantic exhibits a tripolar pattern. Here, we explore the spatiotemporal structure, including the vertical, of the North Atlantic tripole using observations and reanalysis data in 1993–2021. For the first time, we demonstrate that the tripole's vertical structure across the Mid‐Atlantic Bight continental shelf and slope differs from that in the ocean interior. The tripole strongly projects in the Slope Water north of the Gulf Stream mean path, marked with temperature changes across the water column not maintained by air‐sea heat flux. Over the shelf, the tripole‐associated sea level, temperature, and ocean current are weak. In the ocean interior, the tripole temperature variability is apparent in the upper 100 m in the tropics and three times as deep in the subtropics. The tripole imprints resemble those of the North Atlantic Oscillation, peaking after the dominant atmospheric mode's winter maximum. Plain Language Summary: A significant fraction of large‐scale and year‐to‐year sea surface temperature and height changes in the North Atlantic exhibit a tripolar pattern, with anomalies of the equal sign in the tropical and subpolar regions and the opposite in the subtropics. The tripolar pattern has been linked to increased nuisance flooding along the United States Southeast coast in the recent decade. Despite its extensive impacts on the low‐lying coastal lands, many of the pattern's properties remain unknown, particularly the vertical structure. This study uses long‐term observations and reanalysis data to describe tripole characteristics from the continental shelf to the ocean interior. The results indicate that the tripole‐associated temperature, sea level, and ocean current are most pronounced between the Gulf Stream and the Mid‐Atlantic Bight shelf break, concomitant with changes in the strength and position of the flow, but they rapidly decay toward the shore. In the interior, the temperature difference between the tropics and the subtropics attributable to the tripole is largest in the upper 100 m. The tripole generally attains maximum following the North Atlantic Oscillation's winter peak. Key Points: The tripole variability is strongest in the Slope WaterThe vertical extent of tripole‐related temperature variability in the subtropics is three times deeper than in the tropicsTripole‐associated temperature, ocean current, and sea level changes in the Mid‐Atlantic Bight shelf are small [ABSTRACT FROM AUTHOR]

Improvement of subseasonal to seasonal North Atlantic winter forecasting requires better prediction of the North Atlantic Oscillation (NAO), the dominant mode of variability in the Northern Hemisphere. Despite recent research demonstrating the importance of stratosphere‐troposphere coupling for NAO predictability, the driving mechanisms and implications are not fully understood. This study reveals that the October upper stratosphere is highly relevant to polar vortex development and predictability of winter NAO. We derive a simple index based on the strength of meridional wind in the upper stratospheric surf zone and find that anomalously poleward motion is associated with a significantly stronger polar vortex, which predicts the subsequent winter surface NAO with a correlation coefficient of r = 0.40. Plain Language Summary: The North Atlantic Oscillation (NAO) is a large‐scale atmospheric system that significantly affects the weather and climate in the North Atlantic basin, especially in winter. Accurately forecasting the NAO 1–3 months ahead is challenging. However, on these timescales, more predictable factors like the stratosphere play a crucial role in modulating the NAO. The upper stratosphere plays a significant role in stratospheric dynamics, however it remains poorly understood and its potential to improve winter NAO predictions is largely untapped. Here, we create a simple index to measure the north‐south winds in the upper stratosphere during October and find that a positive index predicts a stronger winter polar vortex, leading to a more positive NAO. This results in warmer, wetter, and stormier conditions in northern Europe and the eastern US, and colder, drier conditions in southern Europe and Canada. Conversely, a negative index indicates a weaker winter polar vortex and an increased likelihood of sudden stratospheric warming events, which can often lead to extreme and prolonged cold conditions at the surface. Our findings highlight the importance of monitoring the upper stratosphere in October to improve winter NAO predictions and better understand stratosphere‐troposphere coupling. Key Points: The meridional wind in the midlatitude upper stratosphere in October contains significant seasonal predictability for the winter NAOThe strength of the meridional wind in this region also predicts changes in the occurrence of midwinter SSWsThe winter surface impact of the October upper stratospheric wind occurs partly, but not entirely, via changes to the polar vortex [ABSTRACT FROM AUTHOR]

The North Atlantic Tripole sea surface temperature anomaly (NAT SSTA) is critical for predicting climate in Eurasia. Predictions for summer climate anomalies currently assume the NAT SSTA phase persists from boreal winter through summer. When NAT phase switches, predictions become unreliable. However, the NAT phase sustained/reversal mechanism from boreal winter to spring remains unclear. This study demonstrates that the evolution of the NAT phase could be driven by the North Atlantic Oscillation (NAO). When NAO phase persists (switches) during preceding boreal winter, the NAO-driven wind anomalies favor maintenance (transition) of NAT phase by causing sea surface heat flux anomalies. Meanwhile, NAT SSTA causes eddy-mean flow interaction by increasing atmospheric baroclinity, thereby generating positive feedback on the former NAO phase. The NAO phase change is leading 1–3 months for the NAT phase. These findings deepen our understanding of the interaction between NAO and NAT and provide implications for seasonal prediction in Eurasia. [ABSTRACT FROM AUTHOR]

Based on the leaf area index (LAI) and normalized difference vegetation index (NDVI) from 1982 to 2020, this study reveals a significant increase in the intensity of interannual variability (IIV) in spring (April–May) vegetation over Northeast Asia since the early 2000s. This change is closely linked to the notable increase in the IIV of April surface air temperatures over Northeast Asia from the former period (1986–2001) to the latter period (2002–2016). Further analysis also highlights a salient impact of the North Atlantic Oscillation (NAO) on the strengthened IIV in vegetation. During the latter period, there is a substantial increase in the IIV of the March NAO compared with the former period. This greater variability allows the positive NAO to significantly influence the net heat fluxes, thereby leading to a positive phase of the North Atlantic tripole (NAT) sea surface temperature (SST) pattern in March. Given the persistence of SSTs, the positive NAT SST pattern lasts to April, subsequently causing positive height anomalies over Northeast Asia through a wave train that originates from the North Atlantic and propagates downstream. This process consequently results in an increase in surface air temperature over Northeast Asia and hence the local vegetation. Thus, the increased IIV of the March NAO is conducive to enhancing the IIV in spring vegetation over Northeast Asia. Plain Language Summary: Vegetation in Northeast Asia is of particular interest because of its great potential to dampen or amplify climate change. The intensity of interannual variability (IIV) in vegetation can reflect vegetation vulnerability to external disturbances. However, the change in the IIV of vegetation over Northeast Asia is poorly understood. Our results reveal that the IIV of spring (April–May) vegetation in Northeast Asia has experienced a noticeable increase since the start of the 21st century. This increase is closely related to the enhanced IIV in April surface air temperature. The North Atlantic Oscillation (NAO) in March may also play an important role in the increased IIV of spring vegetation in Northeast Asia through its influence on the surface air temperature. These findings are encouraging for improving our understanding of changes in spring vegetation over Northeast Asia. Key Points: Interannual variability of spring vegetation in Northeast Asia has increased after the early 2000sThis increase is linked to the enhanced interannual variability in April surface air temperaturesThe March NAO also plays a role in the increased interannual variability of spring vegetation [ABSTRACT FROM AUTHOR]

ABSTRACT In this study, the effects of the Mount Pinatubo eruption on surface air temperature (SAT) over mid‐ to high‐latitude Northern Hemisphere (NH) continents in December–January–February (DJF) 1991/92 were investigated using MPI‐ESM Grand Ensemble simulations, observations and reanalysis data. The results indicated that the 1991 Mount Pinatubo eruption was not the primary cause of the SAT warming anomaly over the mid‐ to high‐latitude NH continents in DJF 1991/92. In the observations, a positive Arctic Oscillation (AO) or North Atlantic Oscillation (NAO)‐like pattern dominated the warming of Eurasia, while a Pacific North American (PNA)‐like pattern dominated the warming of North America. However, the model ensemble mean (MEM) simulated SAT and sea level pressure anomalies were much weaker over high‐latitude continents. Furthermore, by categorising the 100 MPI‐ESM Grand Ensemble simulations into four categories, we found that the probability of warm and cold temperature anomalies occurring over Eurasia and North America was nearly equal. Only about 22% of the MPI‐ESM Grand Ensemble members simulated winter warming over the mid‐ to high‐latitude NH continents that matched observations. Our study suggested that this winter warming was mostly caused by the internal variability of the climate system, which was consistent with previous studies. A more detailed analysis indicated that, following the Mount Pinatubo eruption, the intrinsic phase shifts in the AO and PNA remained key factors driving the SAT variations in Eurasia and North America, respectively. [ABSTRACT FROM AUTHOR]

The cloud cover and meteorological parameters serve as fundamental criteria for an astronomical observatory working in optical and infrared wavelengths. In this paper, we present a systematic assessment of key meteorological parameters at the Lenghu astronomical observing site on the Tibetan Plateau. The data sets adopted includes the meteorological parameters collected at the local weather stations at the site and in the Lenghu Town, the sky brightness acquired by the Sky Quality Meters and all-sky images from a digital camera, the ERA5 reanalysis data base, and global climate monitoring data. From 2019 to 2023, the fractional observable time of photometric condition is 69.70 per cent, 74.97 per cent, 70.26 per cent, 74.27 per cent, and 65.12 per cent, respectively, which is influenced by a variety of meteorological parameters. Large-scale air–sea interactions affect the climate at Lenghu site, which in fact delivers a clue to understand the irregularity of 2023. Specifically, precipitable water vapour at Lenghu site is correlated to both the westerly wind index and the summer North Atlantic Oscillation index, the yearly average temperature of Lenghu site is observed to increase significantly during the occurrence of a strong El Niño event, and the relative humidity anomaly at Lenghu site is correlated to the Pacific Decadal Oscillation index. The decrease of fractional observing time in 2023 was due to the ongoing strong El Niño event and relevant global climate change. We underscore the substantial role of global climate change in regulating astronomical observing conditions and the necessity for long-term continuous monitoring of the astronomical meteorological parameters at Lenghu site. [ABSTRACT FROM AUTHOR]

Climate change‐driven impacts on vegetation productivity have been shown to drive mammalian herbivore population dynamics in Arctic and alpine environments. However, there is less evidence for temperate systems. To address this, we examined the contribution of increasing plant biomass in different vegetation communities (measured by NDVI, normalised difference vegetation index) and winter weather on the observed long‐term upward trend in the population of the Soay sheep of Hirta, St Kilda, UK. We found that biomass had increased in all vegetation communities present and increased the fastest in vegetation types preferred by the sheep. Specifically, those communities with high specific leaf area and Ellenberg's N, low leaf dry matter content. Peak summer NDVI and either winter average wind speed or winter North Atlantic Oscillation data added to the variance explained by a simple density dependence model of yearly sheep population growth rates. The highest explanatory power was found for preferred vegetation types including maritime cliff communities dominated by Plantago species, but also for both inaccessible (Rumex acetosa‐dominated) or unpreferred (Eriophorum vaginatum‐ or Sphagnum‐dominated) communities where seasonal variation more closely reflects productivity due to minimal grazing. Although the climate is getting windier and wetter, it is also getting warmer allowing increased plant productivity and this appears to be behind the long‐term increases in the Soay sheep population. Our study indicates that analysing key vegetation communities may reveal these links better than using landscape‐level averages, and that oceanic‐temperate systems may show similar climate‐driven herbivore population trends to those reported in Arctic and alpine systems. [ABSTRACT FROM AUTHOR]

The boreal winter of 2022/23 was notable as a third consecutive winter in which La Niña had an influence on the European weather. The GloSea6 seasonal forecast system predicted a blocked circulation pattern in the North Atlantic in early winter (December), and then a transition through mid‐winter (January) into a more zonal pattern in late winter (February), consistent with the canonical La Niña teleconnection pattern seen previously. The seasonal forecast for the UK was an increased likelihood of near average temperatures, and drier‐ and calmer‐than‐average conditions. Both the predicted broad‐scale circulation patterns and UK winter mean weather conditions verified well against observations, and we show that seasonal forecasts of the North Atlantic Oscillation (NAO) over the last 10 winters show similar skill to previously reported hindcasts. Throughout the winter, the Madden–Julian Oscillation (MJO) was particularly active. On three occasions, it exhibited strong phases 6 and 7. There was also a sudden stratospheric warming (SSW) that occurred on 16th February. This was followed by colder conditions and associated impacts similar to the canonical negative NAO response over the UK, although the main impact fell in March and so did not affect the winter (December–January–February) mean conditions. [ABSTRACT FROM AUTHOR]

Global change has profound effects on marine species, communities, and ecosystems. Among these impacts, small pelagics have emerged as valuable indicators for detecting regime shifts in fish stocks. They exhibit swift responses to changes in ocean variables, including decreased abundances, accelerated juvenile growth rates, early maturation, and reduced adult sizes in warm waters. However, each pelagic species occupies a unique local ecological niche, that reflects the sum of all environmental conditions. Consequently, their responses to environmental changes manifest in distinct ways. We explore here how global change affects small pelagics in the Madeira Archipelago (NE Atlantic Ocean) at (i) community level, by studying the effects of climate change over a 40-year (1980–2019) period on small pelagic landings, and (ii) population level, by studying the effects on the life-history traits of the two most abundant species, Scomber colias and Trachurus picturatus. Our study demonstrated that anomalies in the Sea Surface Temperature and the North Atlantic Oscillation caused a regime shift within the small pelagic community. Both environmental predictors explained 88.9% of the community landings oscillations. S. colias appears to exhibit a relatively more favorable adaptive response to climate change compared to T. picturatus. Understanding the species-specific ecological responses of small pelagic fish to global change is crucial for effective management and conservation efforts in the face of ongoing environmental scenarios. [ABSTRACT FROM AUTHOR]

Large-scale modes of climate variability, such as the El Niño-Southern Oscillation, North Atlantic Oscillation, and Indian Ocean Dipole, show significant regional correlations with seasonal weather conditions, and are routinely forecast by meteorological agencies attempting to anticipate seasonal precipitation patterns. Here, we use machine learning together with more traditional approaches to quantify how much precipitation variability can be explained by large-scale modes of variability, and to understand the degree to which these modes interact non-linearly. We find that the relationship between climate modes and precipitation is predominantly non-linear. In some regions and seasons climate modes can explain up to 80% of precipitation variability. However, variability explained is below 10% for more than half of the land surface, and only 1% of the land shows values above 50%. This outcome provides a clear rationale to limit expectations of predictability from modes of variability in all but a few select regions and seasons. [ABSTRACT FROM AUTHOR]

We present the reconstruction of palaeoenvironmental conditions in the Gdansk, Bornholm, and Arkona Basins of the Baltic Sea over the last millennium. A multiproxy study (including geochemical, XRF, grain size, AMS, and micropalaeontological analyses) of five short sediment cores was performed. The relative age of the sediments was determined based on the Pb distribution along the sediment sequences, as radiocarbon dating has resulted in an excessively old age. The retrieved cores cover two comparable warm periods, the Medieval Climate Anomaly and the Modern Warm Period, for which the increase in surface water productivity was reconstructed. Notably, the production of diatoms was higher during the colder periods (the Dark Ages and Little Ice Age), but this was also the case within the Modern Warm Period. In the Gdansk Basin, the initial salinity increase during the Littorina transgression started after 7.7 cal. a BP. The increased inflow activity was reconstructed during the Medieval Climate Anomaly, even in the Gdansk Basin, despite, in general, very low foraminiferal amounts and diversity. The strongly positive North Atlantic Oscillation Index during this period led to the prevalence of westerly winds over the Baltic region and stronger saltwater intrusions. In the recent sediments, the reconstructed inflow frequency demonstrates a variability against the reduction trend, and a general decline compared to the Medieval Climate Anomaly is seen. [ABSTRACT FROM AUTHOR]

Copyright of Plateau Meteorology is the property of Plateau Meteorology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study examined the carbon cycling dynamics in the tropical Atlantic Ocean from 1985 to 2023, focusing on factors influencing the surface partial pressure of CO2 (pCO2), freshwater input, total alkalinity (ALK), total dissolved carbon (TCO2), and pH levels. The time series data revealed significant trends, with average pCO2 concentrations rising from approximately 350 μatm in the early 1990s to over 400 μatm by 2023. The TCO2 levels increased from about 2000 μmol/kg to 2200 μmol/kg, while ALK rose from approximately 2300 μmol/kg to 2500 μmol/kg. This increase highlights the ocean's role as a carbon sink, particularly in areas with high biological productivity and upwelling where TCO2 also rose. This study employed Empirical Orthogonal Functions (EOFs) to identify variability modes and understand spatial patterns of pCO2. Freshwater dynamics significantly affect TCO2 concentrations, particularly in coastal regions, where pH can shift from 8.2 to 7.9, exacerbating acidification. Rising sea surface temperatures have been linked to elevated pCO2 values. These findings support the need for ongoing monitoring and effective management strategies to mitigate the impacts of climate change and ensure the sustainability of marine resources. This study documented the long-term trends in tropical Atlantic CO2 parameters linked to the North Atlantic Oscillation (NAO) and Atlantic Multidecadal Oscillation (AMO). [ABSTRACT FROM AUTHOR]

Daily 7Be activity concentrations data across 21 global locations between 2010 and 2017 from the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) were analyzed using multifractal formalism. The multifractal detrended fluctuation analysis revealed that 7Be distribution across the 21 locations are multifractal (0.17<α<0.66) with a wide range of fractal exponents. The observed multifractality was found to be statistically significant except at two locations (RN45 and RN47). The multifractal strength (α) and Holder’s exponent (α0) were used to group the locations into 3 clusters with K-means algorithm. The relationship between 7Be and five drivers (Southern Oscillation Index — SOI, North Atlantic Oscillation — NAO, Total Sunspot number — Tot_SN, Northern hemisphere Sunspot number — NH_SN and Southern hemisphere sunspot number — SH_SN) was investigated using multifractal detrended cross-correlation analysis. The multifractal cross-correlation between 7Be and drivers was found to be 0.06–0.21(SOI), 0.08–0.23 (NAO), 0.04–0.27 (Tot_SN), 0.05–0.25 (NH_SN) and 0.04–0.27 (SH_SN). NAO was found to be the strongest driver of 7Be. The location, RN16 in Yellowknife Canada, showed strong cross-correlation with the five drivers. [ABSTRACT FROM AUTHOR]

Air‐sea heat and moisture fluxes modulate the surface energy balance and oceanic and atmospheric heat transport across all timescales. Spatial gradients of these fluxes, on a multitude of spatial scales, also have significant impacts on the ocean and atmosphere. Nevertheless, analysis of these gradients, and discussion regarding our ability to represent them, is relatively absent within the community. This letter discusses their importance and presents a wintertime climatology. Their sensitivity to spatiotemporal scale and choice of data set is also examined in the mid‐latitudes. A lead‐lag analysis illustrates that wintertime air‐sea heat flux gradients in the Gulf Stream can precede the North Atlantic Oscillation by ∼1 month. A lack of observations and thus validation of air‐sea heat flux gradients represents a significant gap in our understanding of how air‐sea processes affect weather and climate, and warrants increased attention from the observational and modeling communities. Plain Language Summary: The oceans impact both weather and climate by heating and cooling the lower atmosphere. Surface latent (sensible) heat flux is a quantity that measures the exchange of heat associated with evaporation of seawater (an air‐sea temperature difference). In addition to the absolute exchange, the manner in which the exchange varies spatially (the heat flux gradients) is also known to be important for the development of weather systems and longer‐term climate. Despite this, relatively little attention is paid in the literature to variability in these gradients. This study provides a brief overview of their importance and provides a wintertime climatology in these gradients. It is also illustrated that when considering gradients, the importance of specifying the spatial scale over which the gradient is calculated is critical. Although many differences exist between air‐sea heat flux data products in these gradients, there are currently almost no observations to validate them in key areas of interest, which represents a significant deficiency in our understanding of ocean‐atmosphere interactions. This is emphasized by demonstrating that these gradients in the mid‐latitudes can statistically precede variability in the North Atlantic Oscillation, the most important mode of monthly atmospheric variability in the North Atlantic. Key Points: Air‐sea heat and moisture flux gradients modulate important oceanic and atmospheric processes across a multitude of spatiotemporal scalesAir‐sea heat flux gradient variability can statistically precede mid‐latitude atmospheric variabilityNotable air‐sea heat and moisture flux gradient inconsistencies exist in data products, yet the ability to validate them remains elusive [ABSTRACT FROM AUTHOR]

The winter North Atlantic Oscillation (NAO), one of the leading modes of atmospheric variability in the Northern Hemisphere and key driver of surface climate anomalies, was long considered to be spatially stable. Yet, its northern center-of-action – the Icelandic Low (IL) – shifted eastward in the late 1970s compared to the preceding decades of the mid-20th century. The responsible processes are still uncertain, particularly after the decline of the positive NAO trend in the 21st century. Here, we present observational and model evidence that the NAO-IL moves naturally alternating between two preferential locations, west/east of Iceland, with no need for changes in anthropogenic forcing or low-frequency oceanic variability. These recurrent longitudinal displacements of the NAO pattern appear linked to zonal changes in the fluctuations (not mean-state) of transient-eddy activity, emphasizing the relevance of internal atmospheric variability, and could represent a major source of uncertainty in regional climate prediction and projection. [ABSTRACT FROM AUTHOR]

The withdrawal of the United Kingdom from the European Union will likely result in reduced fishing grounds for the Belgian fishing fleet. This fleet now targets demersal fish, but there used to be a tradition of catching Atlantic herring (Clupea harengus). After the stock collapse of Atlantic herring in the 1970s, fishing on herring by the Belgian fleet did not recover and herring quotas are now exchanged with the Netherlands and Germany. To assess the feasibility of reintroducing herring fisheries for the Belgian fishing fleet, our study created spatiotemporal species distribution models for Atlantic herring in the Northeast Atlantic Ocean, focusing results on the Belgian Part of the North Sea. In total 30078 occurrence records were derived and processed to fit species-environmental relationships with temperature, salinity, seabed characteristics and plankton concentration using Maximum entropy (Maxent) models. The Area Under the Curve of the Receiver Operating Characteristic plot (AUC) and the True Skill Statistic (TSS) were used to assess model fit. Models performed well (AUC > 0.7 and TSS > 0.6). While a broad spatiotemporal distribution of Atlantic herring in the Northeast Atlantic Ocean was inferred, regional differences show that herring habitat is most suitable during winter months in the Belgian Part of the North Sea for both adult and larval herring (habitat suitability index > 75%). This regional trend in the Belgian Part of the North Sea was negatively correlated (R = -0.8) with the North Atlantic Oscillation (NAO). We anticipate that these findings will provide valuable insights for policymakers to implement sustainable fisheries management practices. [ABSTRACT FROM AUTHOR]

Understanding storm impacts on marine vertebrate demography requires detailed meteorological data in tandem with long‐term population monitoring. Yet most studies use storm proxies such as the North Atlantic Oscillation Index (NAOI), potentially obfuscating a mechanistic understanding of current and future risk. Here, we investigate the impact of extratropical cyclones by extracting north Atlantic winter storm characteristics (storm number, intensity, clustering and wave conditions) and relating these with long‐term overwinter adult survival of three long‐lived sympatric seabirds which winter at sea—common guillemot Uria aalge, Atlantic puffin Fratercula arctica and razorbill Alca torda. We used multidecadal mark‐recapture analysis (1970s–2020s) to estimate survival while correcting for resighting probability, combined with spatially explicit environmental data from geolocation‐derived wintering areas, to determine the impact of different storm characteristics (i.e., number, intensity, duration, gap between storms, wave height and wind speed), as well as broad‐scale climatic conditions (NAOI and sea surface temperature [SST]). All three species experienced rapid population growth over the study period. Guillemot and razorbill survival was lower during stormier winters, with an additive effect of summer SST for guillemots, and a negative interaction with population size for razorbills. Puffin survival was negatively correlated with winter SST, and the lowest puffin survival coincided with intense winter storms and a large seabird wreck in 2013/14. The number of days with wind speed >30 and 35 ms−1 negatively impacted razorbill and guillemot survival, respectively, and puffin survival was higher when gaps between storms were longer. Our results suggest negative but divergent storm impacts on these closely related sympatric breeders, which may be compounded by warmer seas and density‐dependence as these populations return to their previously much larger sizes. We tentatively suggest that frequent, long‐lasting storms with strong winds are likely to have the greatest negative impact on auk survival. Moreover, we highlight the possibility of tipping points, where only the most extreme storms, that may become more frequent in the future, have measurable impacts on seabird survival, and no effect of NAOI. [ABSTRACT FROM AUTHOR]

We use Coupled Model Intercomparison Project Phase 6 (CMIP6) coupled and Atmospheric Model Intercomparison Project (AMIP) climate models, dynamical analyses, and observations to investigate interactions between summer Arctic sea ice concentration (SIC) variations and the Summer North Atlantic Oscillation (SNAO). Observations suggest that SIC-SNAO relationships mainly come from the East Siberian to Arctic Canada (ESAC) region where a weak atmospheric jet stream exists in summer. Twelve CMIP6 models with the most realistic atmospheric climatologies over the North Atlantic and Europe agree well with reanalyses on relationships between SIC and Northern Hemisphere atmospheric circulation. CMIP6 model data indicate that ESAC SIC influences the SNAO with a lead time of several weeks. However, AMIP simulations do not reproduce the observed atmospheric circulation when observed sea ice is prescribed. Rossby wave analyses do though support observed ESAC SIC influences on the SNAO. We conclude that ESAC Arctic SIC modestly influences the SNAO, and such investigations require the use of coupled models. [ABSTRACT FROM AUTHOR]

Snow is particularly impacted by climate change and therefore there is an urgent need to understand the temporal and spatial variability of depth of snowfall (HN) trends. However, the analysis of historical HN observations on large‐scale areas is often impeded by lack of continuous long‐term time series availability. This study investigates HN trends using observed time series spanning the period 1920–2020 from 46 sites in the Alps at different elevations. To discern patterns and variations in HN over the years, our analysis focuses also on key parameters such as precipitation (P), mean air temperature (TMEAN), and large‐scale synoptic descriptors, that is, the North Atlantic Oscillation (NAO), Arctic Oscillation (AO) and Atlantic Multidecadal Oscillation (AMO) indices. Our findings reveal that in the last 100 years and below 2000 m a.s.l., despite a slight increase in winter precipitation, there was a decrease in HN over the Alps, especially for southern and low‐elevation sites. The South‐West and South‐East regions experienced an average loss of 4.9 and 3.8%/decade, respectively. A smaller relative loss was found in the Northern region (2.3%/decade). The negative HN trends can be mainly explained by an increase of TMEAN by 0.15°C/decade. Most of the decrease in HN occurred mainly between 1980 and 2020, as a result of a more pronounced increase in TMEAN. This is also confirmed by the change of the running correlation between HN and TMEAN, NAO, AO over time, which until 1980 were not correlated at all, while the correlation increased in later years. This suggests that in more recent years favourable combinations of temperature, precipitation, and atmospheric pattern have become more crucial for snowfall to occur. On the other hand, no correlation was found with the AMO index. [ABSTRACT FROM AUTHOR]

Internal variability arising from the inherently chaotic nature of the climate system has amplified or obscured human-caused changes, especially at regional scales in the extratropics, where its contribution to climate variability is the largest. It is virtually certain that this will continue in the near-term. We here focus on the Northern Europe region, whose variability is largely controlled by the North Atlantic Oscillation (NAO) and the Atlantic Meridional Overturning Circulation (AMOC) through remote dynamical and thermodynamic processes, and introduce the concept of internal variability storylines (IVS) to explore, understand, and quantify the role of the two combined drivers of internal variability in the modulation of the anthropogenic warming by 2040 in winter. Based on a large ensemble of historical-scenario simulations, we show that the high-impact IVS, characterised by weak AMOC decline and a decadal shift of the NAO toward dominant positive phase, leads faster to warmer-wetter conditions independently of actual and future greenhouse gases emissions. By contrast, amplified AMOC reduction and more recurrent negative NAO can considerably damp both warming and wettening at near-term. In the latter IVS, we provide evidence that winter-severe conditions similar to those in 2010, that had been responsible for widespread socio-economic disruptions, remain almost as likely to occur by 2040. Reframing the uncertain climate outcomes into the physical science space in a conditional form through the prism of IVS makes climate information relevant for accurate risk assessments and adaptation planning. [ABSTRACT FROM AUTHOR]

This study presents a framework to assess climate variability and change through atmospheric circulation patterns (CPs) and their link with regional processes across time scales. We evaluate the CP impacts on daily rainfall and maximum and minimum temperatures in the Iberian Peninsula using sea level pressure (SLP) during 1950–2022. Different sensitivity analyses are performed, employing multiple spatial domains and number of patterns. An optimal classification is found in midlatitudes, centered over the Mediterranean basin and covering part of the North Atlantic Ocean, which can identify atmospheric configurations significantly related to discriminated rainfall and temperature anomalies, with clear seasonal behavior. The temporal variability of CPs is studied across time scales showing, e.g., that transitions between patterns are faster in autumn and spring, and that CPs exhibit distinct temporal variability at intraseasonal, seasonal, interannual, and decadal scales, including significant long-term trends on their frequency. CPs influence temperature and precipitation variations throughout the year. The winter season exhibits the largest atmospheric circulation variability, while the summer is dominated by persistent high-pressure structures—the subtropical Azores high—leading to warm and dry conditions. Based on an interannual correlation analysis, some CPs are significantly associated with the North Atlantic Oscillation (NAO), stronger during winter, indicating the NAO modulation on the regional-to-local climatic features. Overall, this approach arises as a dynamic cross-time-scale framework that can be adapted to specific user needs and levels of regional detail, being useful to study climate drivers for climate change and to perform a process-based evaluation of climate models. [ABSTRACT FROM AUTHOR]

Against the backdrop of intensified global climate change, the frequency and intensity of extreme weather events in mainland China continue to rise due to its unique topography and complex climate types. In-depth research on the trends and impacts of climate extremes can help develop effective adaptation and mitigation strategies to protect the environment and enhance social resilience. In this research, temperature data from 2029 meteorological stations for the period 1961–2021 were used to study 15 extreme temperature indices and 3 extreme composite temperature indices. Linear propensity estimation and the Mann–Kendall test were applied to analyze the spatial and temporal variations in extreme temperatures in China, and Pearson's correlation analysis was used to reveal the relationship between these indices and atmospheric circulation. The results show that in the past 60 years, the extreme temperature index in China has shown a trend of decreasing low-temperature events and increasing high-temperature events; in particular, the increase in warm nights is significantly higher than that of warm days. In terms of spatial distribution, daily maximum temperature less than the 10th percentile (TX10P) and daily minimum temperature greater than the 90th percentile (TN90P) increased significantly in the warm temperate sub-humid (WTSH) region, north subtropical humid (NSH) region, and marginal tropical humid (MTH) region, whereas frost days (FD0) and diurnal temperature range (DTR) decreased significantly. In the extreme composite temperature index, extreme temperature range (ETR) showed a downward trend, while compound heatwave (CHW) and compound heatwave and relative humidity (CHW-RH20) increased, with the latter mainly concentrated in the WTSH and NSH regions. Correlation analysis with climate oscillation shows that Arctic Oscillation (AO), Atlantic Multiannual Oscillation (AMO), and El Niño–Southern Oscillation (ENSO) are positively correlated with extremely high temperatures, whereas North Atlantic Oscillation (NAO) and Pacific Decadal Oscillation (PDO) are negatively correlated. [ABSTRACT FROM AUTHOR]

Surface air temperature (SAT) variability is investigated for advancing our understanding of the climate patterns over the Kingdom of Saudi Arabia (KSA). SAT variability reveals significant warming trends, particularly from 1994 onward, as demonstrated by nonlinear and linear trend analysis. This warming is linked to global climate patterns, which serve as significant indicators for studying the effects of climate change on surface air temperature patterns across the KSA. The empirical orthogonal function (EOF) method is employed for analyzing SAT due to its effectiveness in extracting dominant patterns of variability during the winter (DJF) and summer (JJA) seasons. The first mode (EOF1) for both seasons shows positive variability across the KSA, explaining more than 45% of the variance. The second mode (EOF2) indicates negative variability in central and northern regions. The third mode (EOF3) describes positive variability but with lower variance over time. PC1 is used to describe the physical mechanism of SAT variability and correlations with global sea surface temperature (SST). The physical mechanism shows that the variability in Mediterranean troughs during the winter season and high pressure over the Indian Ocean and central Asia controls SAT variability over the KSA. The correlation coefficients (CCs) were calculated during the winter and summer season between the SAT of the KSA and six teleconnection indices, El Niño Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), Atlantic Meridional Mode (AMM), Pacific Warm Pool (PWP), North Atlantic Oscillation (NAO), and Tropical North Atlantic (TNA) SST for the period from 1994 to 2022. ENSO shifts from positive to negative correlations with SAT from winter to summer. IOD shows a diminished correlation with SAT due to the absence of upper air dynamics. PWP consistently enhances surface warming in both seasons through upper air convergence during both seasons. AMM and NAO have a non-significant impact on SAT; however, TNA contributes warming over central and northern parts during winter and summer seasons. The seasonal SAT variations emphasize the significant role of ENSO, PWP, and TNA across the seasons. The findings of this study can be helpful for seasonal predictability in the KSA. [ABSTRACT FROM AUTHOR]

The western Guangdong Province (WGDP) in China, influenced by both the East Asian and the Indian summer monsoon, is a pivotal region for exploring the Asian summer monsoon (ASM) evolution. So far, there still lacks detail studies on late Holocene climatic/environmental changes here. In this study, multiple magnetic parameters were measured on the lake sediments of Hedong section in this area. Results indicated a dominance of pseudo-single-domain detrital (titano-)magnetite or maghemite mixed with paramagnetic and anti-ferromagnetic minerals in sediments, and the impacts of authigenic greigite, bacterial activity, post-depositional dissolution, and dilution effects were trivial. Changes in rainfall-induced surface erosion intensity were determined as a role in sediment magnetic properties. Intensified surface erosion deduced by increased rainfall favored enhanced concentrations and more coarse-grained magnetic minerals in sediments, and vice versa. Thus, the magnetic parameters can be used to reflect varying ASM strength in the past ~4300 years. They revealed four relatively humid (strengthened ASM) (i.e., 4300–4000 cal. yr BP, 3500–3130 cal. yr BP, 2640–1950 cal. yr BP, and 1250–850 cal. yr BP), and three dry periods (weakened ASM) (i.e., 4000–3500 cal. yr BP, 3130–2640 cal. yr BP, and 1950–1250 cal. yr BP) which coincided with the Bond events 3, 2, and 1 respectively. In combination with the three significant cycles (i.e., 1250-, 75-, and 65-year) revealed by spectral analysis on SIRM record, we inferred both the external forcing (e.g., solar activity) and internal hemispheric-scale atmospheric processes (e.g., ENSO, North Atlantic Oscillation) have played an integral role in late Holocene climate changes in the study region. [ABSTRACT FROM AUTHOR]

Spring drought forecasting is essential in South Korea for managing water resources reliably and cultivating agricultural products efficiently, as seasonal rainfall difference often drives water shortage during spring. In the current study, a novel scheme for spring drought forecasting was suggested by extensively searching appropriate predictors from the global climate variable: here mean sea level pressure (MSLP) of the winter season due to its time lag for forecasting. The target series was estimated with the median of the spring precipitation series of the weather stations over South Korea, called the accumulated spring precipitation (ASP). A number of points of the MSLP data were detected as significant cross‐correlation with the ASP and also the points were regionally grouped. Therefore, the regionalization for the high correlation points was performed, resulting in three regions, such as Arctic Ocean (R1), South Pacific (R2), and South Africa (R3). The R1 and R2 regions are located at the places where climate indices have been developed such as Arctic Oscillation and North Atlantic Oscillation for R1 and the indicator of El‐Nino and Southern Oscillation for R2. The generalized linear model (GLM) was adopted in ASP drought forecasting with the driven three regionalized indices as the predictors of the ASP. The result indicates that the regionalized indices can produce a good performance in forecasting the ASP. The forecasting result can be employed as a good tool for managing water resources and planning better cultivation in agriculture industries. [ABSTRACT FROM AUTHOR]

The Observatorio del Roque de los Muchachos will host the northern site of the Cherenkov Telescope Array Observatory (CTAO), in an area about 200 m below the mountain rim, where the optical telescopes are located. The site currently hosts the MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov) telescopes, which have gathered a unique series of 20 yr of weather data. We use advanced profile-likelihood methods to determine seasonal cycles, the occurrence of weather extremes, weather downtime, and long-term trends correctly taking into account data gaps. The fractality of the weather data is investigated by means of multifractal detrended fluctuation analysis. The data are published according to the Findable, Accessible, Interoperable, and Reusable (FAIR) principles. We find that the behaviour of wind and relative humidity show significant differences compared to the mountain rim. We observe an increase in temperature of |$0.55\pm 0.07\mathrm{(stat.)}\pm 0.07\mathrm{(syst.)}$| |$^{\circ }$| C decade−1, the diurnal temperature range of |$0.13\pm 0.04\mathrm{(stat.)}\pm 0.02\mathrm{(syst.)}$| |$^{\circ }$| C decade−1 (accompanied by an increase of seasonal oscillation amplitude of |$\Delta C_m=0.29\pm 0.10\mathrm{(stat.)}\pm 0.04\mathrm{(syst.)}$| |$^{\circ }$| C decade−1), and relative humidity of |$4.0\pm 0.4\mathrm{(stat.)}\pm 1.1\mathrm{(syst.)}$|  per cent decade−1, and a decrease in trade wind speeds of |$0.85\pm 0.12\mathrm{(stat.)}\pm 0.07\mathrm{(syst.)}$|  (km h−1) decade−1. The occurrence of extreme weather, such as tropical storms and long rains, remains constant over time. We find a significant correlation of temperature with the North Atlantic Oscillation Index and multifractal behaviour of the data. The site shows a weather-related downtime of 18.5 per cent–20.5 per cent, depending on the wind gust limits employed. No hints are found of a degradation of weather downtime under the assumption of a linear evolution of environmental parameters over time. [ABSTRACT FROM AUTHOR]

Lake ice phenology serves as a sensitive indicator of climate change in the lake-rich Northeast China. In this study, the freeze-up date (FUD), break-up date (BUD), and ice cover duration (ICD) of 31 lakes were extracted from a time series of the land water surface temperature (LWST) derived from the combined MOD11A1 and MYD11A1 products for the hydrological years 2001 to 2021. Our analysis showed a high correlation between the ice phenology measures derived by our study and those provided by hydrological records (R2 of 0.89) and public datasets (R2 > 0.7). There was a notable coherence in lake ice phenology in Northeast China, with a trend in later freeze-up (0.21 days/year) and earlier break-up (0.19 days/year) dates, resulting in shorter ice cover duration (0.50 days/year). The lake ice phenology of freshwater lakes exhibited a faster rate of change compared to saltwater lakes during the period from HY2001 to HY2020. We used redundancy analysis and correlation analysis to study the relationships between the LWST and lake ice phenology with various influencing factors, including lake properties, local climate factors, and atmospheric circulation. Solar radiation, latitude, and air temperature were found to be the primary factors. The FUD was more closely related to lake characteristics, while the BUD was linked to local climate factors. The large-scale oscillations were found to influence the changes in lake ice phenology via the coupled influence of air temperature and precipitation. The Antarctic Oscillation and North Atlantic Oscillation correlate more with LWST in winter, and the Arctic Oscillation correlates more with the ICD. [ABSTRACT FROM AUTHOR]

This letter raises the possibility that ergodicity concerns might have some bearing on the signal‐to‐noise paradox. This is explored by applying the ergodic theorem to the theory behind ensemble weather forecasting and the ensemble mean. Using the ensemble mean as our best forecast of observations amounts to interpreting it as the most likely phase‐space trajectory, which relies on the ergodic theorem. This can fail for ensemble forecasting systems if members are not perfectly exchangeable with each other, the averaging window is too short and/or there are too few members. We argue these failures can occur in cases such as the winter North Atlantic Oscillation (NAO) forecasts due to intransitivity or regime behaviour for regions such as the North Atlantic and Arctic. This behaviour, where different ensemble members may become stuck in different relatively persistent flow states (intransitivity) or multi‐modality (regime behaviour), can in certain situations break the ergodic theorem. The problem of non‐ergodic systems and models in the case of weather forecasting is discussed, as are potential mitigation methods and metrics for ergodicity in ensemble systems. [ABSTRACT FROM AUTHOR]

Given the link between climatic factors on one hand, such as climate change and low frequency climate oscillation indices, and the occurrence and magnitude of heat waves on the other hand, and given the impact of heat waves on mortality, these climatic factors could provide some predictive skill for mortality. We propose a new model, the Mortality-Duration-Frequency (MDF) relationship, to relate the intensity of an extreme summer mortality event to its duration and frequency. The MDF model takes into account the non-stationarities observed in the mortality data through covariates by integrating information concerning climate change through the time trend and climate variability through climate oscillation indices. The proposed approach was applied to all-cause mortality data from 1983 to 2018 in the metropolitan regions of Quebec and Montreal in eastern Canada. In all cases, models introducing covariates lead to a substantial improvement in the goodness-of-fit in comparison to stationary models without covariates. Climate change signal is more important than climate variability signal in explaining maximum summer mortality. However, climate indices successfully explain a part of the interannual variability in the maximum summer mortality. Overall, the best models are obtained with the time trend and the North Atlantic Oscillation (NAO) used as covariates. No country has yet integrated teleconnection information in their heat-health watch and warning systems or adaptation plans. MDF modeling has the potential to be useful to public health managers for the planning and management of health services. It allows predicting future MDF curves for adaptive management using the values of the covariates. [ABSTRACT FROM AUTHOR]