Search Results (19)

On 3 February 2006, a powerful Mediterranean cyclone instigated a widespread dust storm across Saudi Arabia. Meteorological observations from one station recorded strong westerly to southwesterly winds, with gusts reaching 40 m/s, accompanied by thunderstorms and dust storms. This study delves into the formation and development of this significant Mediterranean cyclone, which impacted the Mediterranean basin and the Arabian Peninsula from 26 January to 4 February 2006. Utilizing ECMWF ERA5 reanalysis data, this research analyzes the synoptic and dynamic conditions that contributed to the cyclone’s evolution and intensification. The cyclone originated over the North Atlantic as cold air from higher latitudes and was advected southward, driven by a strong upper-level trough. The initial phase of cyclogenesis was triggered by baroclinic instability, facilitated by an intense upper-level jet stream interacting with a pre-existing low-level baroclinic zone over coastal regions. Upper-level dynamics enhanced surface frontal structures, promoting the formation of the intense cyclone. As the system progressed, low-level diabatic processes became the primary drivers of its evolution, reducing the influence of upper-level baroclinic mechanisms. The weakening of the upper-level dynamics led to the gradual distortion of the low-level baroclinicity and frontal structures, transitioning the system to a more barotropic state during its mature phase. Vorticity analysis revealed that positive vorticity advection and warm air transport toward the developing cyclone played key roles in its intensification, leading to the development of strong low-level winds. Atmospheric kinetic energy analysis showed that the majority of the atmospheric kinetic energy was concentrated at 400 hPa and above, coinciding with intense jet stream activity. The generation of the atmospheric kinetic energy was primarily driven by cross-contour flow, acting as a major energy source, while atmospheric kinetic energy dissipation from grid to subgrid scales served as a major energy sink. The dissipation pattern closely mirrored the generation pattern but with the opposite sign. Additionally, the horizontal flux of the atmospheric kinetic energy was identified as a continuous energy source throughout the cyclone’s lifecycle. Full article

In recent years, the energy policies of both Spain and the European Union have pursued the development of renewable energies, including solar power. One way these installations will appear in the Region of Murcia is on bodies of water, which do not alter existing land uses, but ground-mounted solar energy installations do bring about such changes. The Region of Murcia is located in the south-eastern quadrant of the Iberian Peninsula. Positioned on the leeward side of the westerly zonal circulation, characteristic of mid-latitudes, and influenced by the layout of the Betic mountain ranges that cross it from north-west to south-east, it experiences significant scarcity and irregularity of rainfall. In contrast, it benefits from an abundance of sunlight, with more than 3400 h of sunshine per year. This makes it one of the most productive locations for capturing solar energy and converting it into electricity. As a result, the land occupied by photovoltaic parks has increased at the expense of dry farming areas, irrigated land, and woodland. High energy prices have also led to self-consumption measures, with solar panels being installed on the roofs of industrial buildings, floating panels in irrigation reservoirs, photovoltaic solar farms associated with desalination and lift irrigation pumps, and pressure required by localized irrigation, etc. Full article

Meteorological and agricultural droughts are inherently correlated, whereas the propagation mechanism between them remains unclear in Northwestern China. Investigating the linkages between these drought types and identifying the potential influencing factors is crucial for effective water resource management and drought mitigation. This study adopted the Standardized Precipitation Evapotranspiration Index (SPEI) and Standardized Soil Moisture Index (SSMI) to characterize the meteorological and agricultural droughts from 1960 to 2018. The propagation time between these droughts was detected using the Pearson correlation analysis, and the cross-wavelet transform and wavelet cross-correlation were utilized to describe their linkages across the time–frequency scales. The grey relational analysis was applied to explore the potential factors influencing the propagation time. The results revealed that the agricultural drought typically lagged behind the meteorological drought by an average of 6 months in Northwestern China, with distinct seasonal and regional characteristics. The shortest propagation time occurred in the summer (3 months), followed by the autumn (4 months), and the propagation time was longer in the winter (8 months) and spring (9 months). Additionally, the average propagation time was longer in the plateau climate zone (8 months) than in the southeastern climate zone (6 months) and the westerly climate zone (4 months). There was a multi-timescale response between the meteorological and agricultural droughts, with a relatively stable and significant positive correlation over long timescales, whereas the correlation was less clear over short timescales. The key factors influencing the propagation time were soil moisture, elevation, precipitation, and potential evapotranspiration. Furthermore, the wavelet cross-correlation between agricultural and meteorological droughts was relatively high, with a lag of 0 to 3 months; as the timescale increased, the fluctuation period of their cross-correlation also increased. Full article

Anegada, the easternmost island of the Virgin Islands group (Caribbean Sea), is a low Pleistocene carbonate platform surrounded by Horseshoe Reef, the world’s third-largest fringing reef. The western part of the island consists of an extensive beachridge plain (>40 ridges). The sandy carbonate shoreline exists in three morphodynamic domains that exhibit distinctive behaviour over the 59-year study period (1953 to 2012). The northern shore is dominated by westerly longshore drift under fair-weather conditions and cross-shore sediment transport during high-energy events. Storm wave run-up and high nearshore sediment availability contribute to the construction of shore-parallel beachridges. The western end of the island is affected by refracted waves that drive strong erosion and sediment transport. This is reflected in a succession of alternating rapid shoreline recession and progradation phases over the study period. The south–central shoreline is exposed to low wave energy and is stable and colonised by mangroves. The fringing reef plays a dominant role in mesoscale shoreline morphodynamics, both as a sediment source and in wave energy dissipation. Quasi-stable points and embayments suggest a strong influence of the reef framework in controlling the shoreline’s morphology and position. Sediment transfer from the reef to the shoreline appears to take place via shore-oblique, linear sediment transport pathways that develop across the lagoon in response to the modification of incoming waves. Cannibalisation of the shoreline sediment over the past 50 years is leading to straightening of the shoreline planform. This is counter to the long-term (Holocene) development of beachridges and suggests a change from a strongly positive to negative sediment budget. Full article

As the primary mountain range in Central Asia, the Altay Mountains receive water vapor carried by westerly circulation, resulting in relatively abundant local precipitation and lush pastures in all seasons. Consequently, it has become one of the important transportation routes between Asia and Europe. The exploration of long-term variations in precipitation is meaningful for understanding the ebb and flow of the Asia–Europe steppe trade routes. However, previous dendroclimatological studies of the Altay Mountains focused more on temperature changes than precipitations variations. We carried out a 404-year precipitation reconstruction based on the tree rings of Siberian larch growing on the south slopes of the Altay Mountains, which could explain 45.9% of the variance observed in the February–October precipitation. Our reconstruction demonstrated some severe drought events which could be found in the historical documents, such as the drought in the late Ming Dynasty (1640s) and the Ding-Wu Disaster (1870s). The spatial correlation analysis, cross-wavelet spectrum and wavelet coherency analysis indicated that the precipitation variations in the study area may be related to the ENSO and NAO. This study presents a robust precipitation reconstruction of the southern Altay Mountains, serving as a reference for future research on large-scale climatic forces acting on Altay precipitation. Full article

The Antonine Wall Distance Sculptures are iconic and unique sculptural reliefs that marked Rome’s most north-westerly frontier across central Scotland. Their inscribed texts and iconography depict graphic tales of frontier life, and recent non-invasive analysis has confirmed they were originally brought to life through vibrant polychromy. This paper tracks the trajectory of one Distance Sculpture that was embedded into the dramatic setting of Dunnottar Castle off the north-east coast of Scotland during the 16th century, where it was recorded as having been repainted during that episode of use. A suite of complementary analytical techniques, including pXRF, FTIR, and SEM/EDS, was recently reported on which identified pigments and surface treatments as well as their chronology of application, confirmed through stratigraphic sequencing visible in cross-section. That approach facilitated the investigation of all episodes in the itinerary of this iconic sculpted relief from the second century to the Scottish Renaissance. That vanguard research has provided an unprecedented opportunity to unravel the rich hidden history behind this unique monumental inscription and re-tell a fascinating transformational tale of a pivotal period in its past. The combination of historical, archaeological, and scientific approaches to an understudied, and overlooked, phenomenon of post-antique colouration is revolutionary in polychromy studies. It provides innovative and well-contextualised information that lifts an aesthetically modest Roman monument into a vibrant, colourful, and sumptuous decorative feature fit to grace the walls of a Renaissance castle emulating Roman imperial practices. We can now trace its journey through time by delving into the detail of its Renaissance repainting to present, for the first time, an accurate digital reconstruction as it performed for 16th century audiences. Full article

Background. Since the mid-20th century, massive dieback of coniferous forests has been observed in the temperate and boreal zones across North America and Northern Eurasia. The first hypotheses explaining forest dieback were associated with industrial air pollution (acid rain). At the end of the century, new hypotheses emerged that supported critical climate-induced aridization to explain forest dieback. Many studies were based on the SPEI (Standardized Precipitation Evapotranspiration Index) drought index. Our goals were to investigate if the SPEI drought index was a suitable metric to reflect drought conditions in wet and moist dark-needled forests in the South Siberian Mountains (Mts) and if droughts trigger the dieback of those forests. Methods. We calculated the SPEI drought index, the annual moisture index AMI, potential evapotranspiration PET, and water balance dynamics for the period 1961–2019 for four transects in the South Siberian Mts. where decline/dieback of dark-needled Siberian pine and fir forests were identified in situ. Climate data from nine weather stations located at lower and upper elevations of each transect were used to calculate climatic index dynamics for the 1961–2019 period to identify dry and wet phases of the period. Results. Our findings showed that climatic moisture/dryness indices have rarely gone down to high risk levels during the last 60 years (1961–2019). AMI did not reach the critical limit, 2.25, characteristic of the lower border for the dark-needled taiga. SPEI values < −1.5 represent drought stress conditions for dark-needled conifers at the lower border, and these conditions occurred 3–4 times during the 60-year period. However, the annual water balance stayed positive in those years in wet and moist forests at mid-to-high elevations. Trees are known to survive occasional (1–2) dry years. We found that dark-needled conifer dieback often occurs in wet years with plentiful rain rather than in drought years. We found forest dieback was associated with the westerlies that bring atmospheric pollution from the west at 50–56 N latitudes, where the air masses cross populated regions that have widespread industrial complexes. Conclusions. We concluded that the observed decline of dark-needled conifers at middle-to-high elevations across the South Siberia’s Mts was conditioned by several plausible causes, among which air pollution seems to be more credible, rather than dry climatic conditions, as cited in recent literature. Results are essential for understanding these ecosystems and others as our planet changes. Other causes and mechanisms should be further investigated, which would necessitate creating infrastructure that supports multi-disciplinary, inter-agency teamwork of plant physiologists, foresters, chemists, etc. Full article

It is important to consider extreme climate events, reduce disaster losses, and formulate effective disaster prevention and mitigation countermeasures. Based on the daily data from 36 meteorological stations of Xinjiang from 1960 to 2020, in order to analyze the temporal–spatial variations and influencing factors of extreme dry and wet events in Xinjiang, a number of methods were used including climate trend, the Mann–Kendall test, the Fourier power spectrum, the contribution rate, partial least squares and cross-wavelet analysis. Results indicate that the annual average frequency of extreme dry/wet events has a decreasing/increasing trend, at the rate of 0.26 times/decade and 0.19 times/decade, respectively; the variation trend in extreme dry and wet events of four seasons are consistent with the annual counterpart, at the rate of −0.04 times/decade and 0.02 times/decade (spring), −0.08 times/decade and 0.05 times/decade (summer), −0.05 times/decade and 0.06 times/decade (autumn), and −0.1 times/decade and 0.08 times/decade (winter). Fe fluctuation is greatest in winter and the smallest in spring, so the transition to warm and wet is obvious in winter and spring drought is easy to occur; the variation extent of extreme dry and wet events in northern Xinjiang exceeds the counterpart in southern Xinjiang; 1986 and 1987 witnessed abrupt variation in extreme dry and wet events in Xinjiang, with indication of distinct periodic oscillations of 2.44, 2.94, and 5.69 years and 2.94 and 5.69 years, respectively; the extreme dry (wet) events are determined by meteorological factors, comprising precipitation, relative humidity and temperature, and the circulation factors constituted by Western Pacific Subtropical High-Intensity Area (East Asian Trough Intensity, Westerly Circulation and Western Pacific Subtropical High Area) and El Niño events. Full article

This study presents data on the directional flying behaviour of the five most abundant seabird species migrating across the Strait of Gibraltar in relation to the wind, as observed from the north coast, based on radar tracking, and identified to species level by visual observations. A total of 318 seabird trajectories were analysed, illustrating the expected east–west or west–east movements in spring and autumn. We hypothesised that the seabirds that cross the Strait channel during their migrations would behave differently with respect to compensation for wind direction, depending on their flight styles, the migratory period, and the prevailing winds. In this regard, our results showed that flapping birds (Razorbill, Puffin, Northern Gannet, and Balearic shearwater) compensated for wind drift independently of the season and the predominant wind direction. This agrees with the theory that suggests that under moderate winds and whenever visual contact with the coastline is present (as in the case of our study), migrants should compensate for wind drift to avoid being drifted towards the coast, off their main direction of flight. However, Cory’s shearwater, an active gliding seabird with long, slender wings, showed an adaptive directional response to wind, allowing it to be drifted in spring when westerly tailwinds were prevalent, but compensated for wind in autumn, when both easterly and westerly winds were similarly frequent. This adaptive flight behaviour allows it to take advantage of the prevailing tailwinds in spring, gaining ground speed and saving energy during its passage through the Strait, while in autumn, more frequent headwind conditions and a more directional migration to the south may favour compensating for wind drift. Our results support the usefulness of bird radar as a remote tool for describing the pattern of animal movements in the marine environment, as well as their behavioural response to atmospheric conditions. These studies are particularly relevant in the current framework of climate change. Full article

In this study, the European Centre for Medium-Range Weather Forecasts reanalysis v5 (ERA5) wave height reanalysis data and sea-level pressure data from two seasonal prediction systems were used to study the wave characteristics of the Southern Ocean and the seasonal prediction of difficulty for the vessels crossing the westerlies. The results show that significant wave height, extreme wave height, and extreme wave processes were all much stronger in austral winter than in austral summer, making it more difficult for vessels to cross the westerlies in winter. Furthermore, the difficulty of crossing the westerlies has increased over the last 40 years, except in areas east of South America. We found that the monthly frequency of crossing the westerlies between 100° E and 75° W could be accurately estimated point by point using the monthly mean sea-level pressure difference between 30° S and 65° S. With a 1-month lead, the multi-model forecasts gave a fairly accurate forecast of such sea-level pressure difference signal between 150° E to 60° W for target months from May to December. Based on these assessments, we could estimate the difficulty of crossing the westerlies in some specific months in advance using a seasonal prediction system. We also found that the seasonal prediction system produced inaccurate predictions of sea-level pressure at high latitudes, which is the main barrier to further accurately estimating the difficulty of crossing the westerlies. These findings may provide support for predicting difficulty for the vessels crossing the westerlies with a 1-month lead and can provide planning for the route and the allocation of material reserves. Full article

It is urgent to improve the prediction accuracy of precipitation in the preflood season (PFS) over South China (SC) under the background of global warming, and thus the research of water vapor conditions is the key. For the period of 1960–2012, using the daily precipitation data from 60 meteorology stations in SC and National Centers for Environmental Prediction (NCEP) reanalysis data, the synergistic effect of PDO (the Pacific Decadal Oscillation) &IOD (the Indian Ocean Dipole Mode) on water vapor transport process to frontal/monsoon precipitation is revealed, based on the Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT_4.9). For the frontal precipitation, the positive PDO phase (PDO+) compared with the negative PDO phase (PDO−), there is more water vapor over the West Pacific (WP), the northern South China Sea (SCS), and the Bay of Bengal (BOB). Water vapor for frontal precipitation mainly comes from WP and SCS. When PDO and IOD are in phase resonance, the water vapor transport tracks from the SCS, WP are shorter and westward, so more water vapor is transported to SC, the precipitation efficiency of water vapor to PFS precipitation is higher too. For the summer monsoon precipitation, the tropical Indian Ocean (IO)-BOB is rich in water vapor, especially for PDO−& IOD+. The main water vapor transport tracks are the cross-equatorial flows in the IO, BOB and SCS. The precipitation efficiency of water vapor from the IO-BOB is higher for the positive IOD phase (IOD+) than that for the negative IOD phase (IOD−); however, the precipitation efficiency of water vapor from SCS is higher for the IOD− than that for IOD+. Compared with frontal precipitation, the strong westerly anomaly in the northern IO increases the water vapor transport from the north IO, BOB to SC during monsoon precipitation. For the PDO+&IOD+, the stronger Indian Low and cyclonic anomaly in the WP increases the water vapor transported from the IO-BOB to SC, improving the precipitation efficiency of water vapor. Understanding the synergistic effect of the PDO and IOD on water vapor transport will help to improve the accuracy of precipitation prediction, and reduce the negative impact of drought and flood disasters. Full article

Based on the China Meteorological Administration (CMA) best-track data, the ERA5 reanalysis, and the Global Precipitation Measurement (GPM) precipitation data, this paper analyzes the reasons for the heavy rainfall event of Super Typhoon Rammasun in 2014, and the results are as follows: (1) Rammasun was blocked by the western Pacific subtropical high (WPSH), the continental high, and the mid-latitude westerly trough. Such a stable circulation pattern maintained the vortex circulation of Rammasun. (2) During the period of landfall, the southwest summer monsoon surge was reinforced due to the dramatic increase of the zonal wind and the cross-equatorial flow near 108° E. The results of the dynamic monsoon surge index (DMSI) and boundary water vapor budget (BWVB) show that the monsoon surge kept providing abundant water vapor for Rammasun, which led to the enhanced rainfall. (3) The East Asian monsoon manifested an obvious low-frequency oscillation with a main period of 20–40 days in the summer of 2014, which propagated northward significantly. When the low-frequency oscillation reached the extremely active phase, the monsoon surge hit the maximum and influenced the circulation of Rammasun. Meanwhile, the convergence and water vapor flux associated with the low-frequency oscillation significantly contributed to the heavy rainfall. Full article

Sea temperature structures are important for water stratification and marine ecosystems. In the coastal water of Muping, China, stationary measurements of sea temperature captured temporal temperature changes during two summer storm events. The north component of the wind during the two storms was opposite. The temperature responded differently to wind directions in the two storm events. A well-validated numerical ocean model was used to investigate the mechanism of sea temperature variation of the coast of Muping. The model revealed that the southerly and easterly wind was upwelling-favorable in the study area. They generated the shoreward transport of bottom cold water, which induced bottom water cooling, enhanced stratification, and weakened vertical mixing. On the other hand, the northerly and westerly wind was downwelling-favorable and enhanced turbulent mixing. The alongshore upwelling-favorable wind caused more cross-shore transport than cross-shore upwelling-favorable wind, which resulted in stronger bottom cooling. Similarly, alongshore downwelling-favorable wind generated lower temperature than cross-shore wind. A surface cold-water band was formed in the second storm. Although it was formed during upwelling-favorable wind, the temperature balance analysis indicated that vertical mixing and westward horizontal advection were the two dominant processes compared to upwelling. Full article

The Heihe River Basin (HRB), located on the northeastern edge of the Tibetan Plateau, is the second-largest inland river basin in China, with an area of 140,000 km². The HRB is a coupling area of the westerlies, the Qinghai–Tibet Plateau monsoon and the Southeast monsoon circulation system, and is a relatively independent land-surface water-circulating system. The refined characteristics of moisture recycling over the HRB was described by using the Weather Research and Forecasting (WRF) model for a long-term simulation, and the “finer box model” for calculating the net water-vapor flux. The following conclusions were drawn from the results of this study: (1) The water vapor of the HRB was dominantly transported by the wind from the west and from the north, and the west one was much larger than the north one. The net vapor transported by the west wind was positive, and by the north wind was negative. (2) The precipitation over the HRB was triggered mainly by the vapor from the west, which arose from the lower vertical layer to higher one during transporting from west to east. The vapor from the north sank from a higher layer to a lower one, and crossed the south edge of the HRB. (3) The moisture-recycling ratio of evapotranspiration to precipitation over the HRB was much higher than the other regions, which may be due to the strong land–atmosphere interaction in the arid inland river basin. Full article

The spatial distribution of stable water isotopes (also known as an isoscape) in precipitation has drawn increasing attention during the recent years. In this study, based on the observations at 32 stations, we assessed two widely applied global isoscape products (Regionalized Cluster-based Water Isotope Prediction (RCWIP) and Online Isotopes in Precipitation Calculator (OIPC)) at the Qinghai-Tibet Plateau (QTP) and then established an improved isoscape of oxygen isotopes in precipitation on a monthly basis using a regionalized fuzzy cluster method. Two fuzzy clusters can be determined, which is consistent using three meteorological data. The monthly isoscapes show the seasonal movement of high and low isotopic value regions across the QTP and reveal the influences of monsoon and westerly moisture. According to the cross validation, the δ¹⁸O in precipitation in the new monthly isoscapes for the QTP we propose performs better compared to the existing global products. To create a regional isoscape in many other regions, the regionalized fuzzy cluster method can be considered especially for regions with complex controlling regimes of precipitation isotopes. Full article