The recent intensification of extreme precipitation events in the western Mediterranean basin raises questions about the physical mechanisms linking global warming to local hydrological response. This study analyzes the climate features and evolution of the western Mediterranean water-vapor recirculation cell and its role as a modulator of torrential rainfall on the Levante coast. Using ERA5 reanalysis data and daily station precipitation (1950–2024), we characterize a hydrological memory mechanism that links summer dynamics to autumn extremes. The results show that the closed circulation in summer acts as a moisture trap (r = 0.51 between Zonal Circulation and Recharge), creating a reservoir of potential energy that conditions the severity of rainfall months later. A robust predictive correlation (r = 0.52) was verified between cumulative summer recharge (Rec) and extreme autumn precipitation (Rp99), ruling out simultaneous local evaporation (r ≈ −0.05) as the main driver.Secular trend analysis reveals a highly nonlinear climate response. While summer water vapor content (TCWV) has increased by 6.4%, remaining in a Sub-Clausius-Clapeyron regime due to regional subsidence, extreme precipitation (Rp99) has experienced a disproportionate amplification of +68.0%. This discrepancy in magnitude indicates that the system has transitioned to a more efficient regime, in which the intensification of the blocking mechanism (+0.65 σ) and net accumulation (+1.57 σ) act as multipliers of the thermodynamic signal. We conclude that the increase in torrentiality does not respond linearly to a warmer atmosphere, but rather to the dynamic consolidation of an accumulation mode that concentrates available vapor more efficiently.

Abstract This study analyzes the evolution of autumn precipitation on the Mediterranean side of the Iberian Peninsula (Levante) and the spatiotemporal variations in its atmospheric forcings in 1950–2024. Using a dense network of observational data and the ERA5 reanalysis, a seasonal rainfall redistribution process is identified, marked by a statistically significant structural break in 1981. In the recent subperiod, extreme precipitation ( R p95 ) increases at the expense of ordinary precipitation ( R o ), while the total seasonal volume remains stationary. A decoupling of R p95 from key atmospheric indices, such as the Western Mediterranean Oscillation (WeMO) and blocking patterns, is detected. Although the seasonal synoptic‐trigger frequency remains strictly stationary, daily‐scale analysis demonstrates a 31% surge in the absolute rate of local extreme events, revealing a profound shift in thermodynamic efficiency. Composite differences show current torrential events occur in a dynamically more restrictive environment, characterized by an expanded subtropical ridge and subsidence anomalies in the middle troposphere. This attenuation of large‐scale dynamic forcing is offset by a highly localized thermodynamic increase in base specific humidity (up to +0.52 g·kg −1 ), confined to the planetary boundary layer, and amplified latent instability (Convective Available Potential Energy, CAPE), and mechanically capped by the background subsidence (Convective Inhibition, CIN). The Reynolds decomposition of moisture flux confirms a dynamic restructuring. The anomalous transport of the mean circulation loses statistical significance in the Levante and is replaced by low‐frequency flows conditioned by the orography, highlighting a bifurcation effect by the Pyrenees and intense channeling through the Ebro Valley. Transient high‐frequency eddies reveal a pattern of surface divergence over the Balearic Sea that accelerates intense maritime flows toward the coast. Upon impacting the Levantine coastline, these flows generate a deep anomalous convergence that overcomes the background inhibition. Thus, in an environment of synoptic subsidence and enriched moisture, torrential convective activity is driven by forced orographic lifting.

In this study, we report a thermodynamic paradox in southwestern Europe: a significant increase in rainfall extremes coexisting with a systematic decline in ordinary rainfall. Using non-negative matrix factorization (NNMF) applied to precipitation data from high-density stations (1950–2024) and the ERA5 reanalysis, we demonstrate that the region has entered a regime of asymmetric redistribution, wherein the intensification of extreme events is accompanied by a concurrent erosion of ordinary precipitation. Furthermore, non-stationary correlation analysis reveals a recent dynamic decoupling: while Atlantic-influenced regions remain dynamically driven by frontal systems, Mediterranean extremes have lost their historical association with large-scale synoptic patterns, confirming a fundamentally thermodynamically amplified regime. Ultimately, this transforms a region of Atlantic influence into a hot spot of hydroclimatic volatility. A profound temporal decoupling emerges between reanalysis precipitation variables and observations, revealing a critical saturation-efficiency gap: the atmosphere produces fewer ordinary rainfall events, yet produces extremes with unprecedented energetic magnitude, transforming a region of Atlantic influence into a hot spot of hydroclimatic volatility. This research characterizes the structural transformation of the hydrological regime in Southwest Europe from 1950 to 2024. The study uses a high-density observational data network of 8,207 weather stations across mainland Spain and the Balearic Islands, AEMET ROCIO grid precipitation data, and integrated ERA5 reanalysis atmospheric variables. The analyses employ Non-Negative Matrix Factorization (NNMF) to regionalize precipitation into four distinct modes (Cantabrian, Southwest, Mediterranean, and Interior) and apply change-point detection algorithms to identify regime shifts. The model focuses on the “thermodynamic efficiency gap,” analyzing how variables such as Total Column Water Vapor (TCWV) and Relative Humidity (RH) drive rainfall trends. Key results reveal a systemic asymmetric redistribution of precipitation: while ordinary precipitation (Ro) exhibits a widespread decline due to decreasing relative humidity, absolute extreme events (Rp95) are intensifying. Since 1950, total atmospheric water vapor (TCWV) has increased by 9

This study provides a comprehensive evaluation of the hydroclimatic transition of the Iberian Peninsula (1950-2024), characterizing its spatial structure and temporal evolution. By integrating ERA5 atmospheric water balances, high-density station observations, and stepwise regression models, we show evidence that the region is undergoing a structural redistribution of precipitation. The atmospheric water balance indicates a transition toward a moisture-limited sink, characterized by declining surface evaporation and rising atmospheric evaporative demand, while net moisture convergence and total precipitation remain statistically unchanged. Stationlevel analysis robustly validates this volumetric stability (present in 90.5% of the territory) but reveals an underlying zero-sum redistribution: the fractional contribution of extreme precipitation (Rp95) has systematically increased relative to ordinary rainfall (Ro) across 29.6% of the observational network, intensifying along the coasts while ordinary rainfall declines inland (redistribution precipitation-climate scenario). To determine the drivers of this shift, stepwise regressions were applied using the annually aggregated daily frequencies of large-scale circulation patterns (NAO, WeMO, subtropical ridges, and blocks). Results confirm that the stationary frequency of these dynamic drivers successfully explains the long-term stability of total precipitation volume but does not account for the intensification of extremes. The models reveal distinct seasonal mechanisms: while winter extremes exhibit an amplification of dynamic efficiency, autumn extremes (Rp95) remain entirely uncoupled from large-scale circulation. Furthermore, the intensification of these autumn extremes has accelerated significantly in the recent period (1988-2024). Since the dynamic triggers remain stable, these results provide diagnostic evidence highly consistent with thermodynamic amplification. Operating within a moisture-enriched environment, driven by long-term increases in total column water vapor (TCWV), classical synoptic configurations now act as more efficient triggers, thereby enhancing coastal extremes and shifting the Peninsula toward a more extreme, hydrologically volatile regime.

Based on a dense series of temperature data from 3685 observatories located in peninsular Spain and on the Balearic Islands, the patterns and trends of the annual and seasonal values of the maximum, minimum and daily temperature range for the 1952-2022 period are analysed. To this end, this study analyses anomalies for the 1961-1990 period, trends in different time windows, spatial variations, and the influence of altitude and longitude on the three aforementioned variables. The main results are: (1) since the 1980s, positive anomalies of maxima and minima have been observed, with increasing values in recent decades; (2) summer and spring are the seasons with the highest maxima and minima anomalies, while a decrease in the diurnal temperature range values in autumn has been noted in recent decades; (3) since the 1970s, there has been a positive trend in maximum and minimum temperatures that, after a pause in the 2000s, regains strength given the high values recorded in recent years; (4) the trend in maximum temperature increases with altitude, with stations above 1500 m being the most affected. However, for minimum temperatures, urban stations below 250 m show the most marked trends; (5) the stations in the east are warming more quickly than those in the west. The high temperatures recorded in recent decades have led to a new upturn in temperature trends in the study area, which underlines the importance of regularly updating such studies. The influence of the increasingly warmer Mediterranean Sea may explain some of these changes.

This study examines the mean annual cycles of monthly cumulated fog-water amounts (CFW) in the central Mediterranean Iberian Peninsula (MIP), highlighting the interplay between meteorological conditions, topography, and geographic location. Seasonal asymmetry in fog-water collection is evident, with summer exhibiting higher fog collection frequency but lower water volumes. In contrast, non-summer seasons feature lower frequency but higher intensity fog events. Tropospheric circulation anomalies at mid-and low-tropospheric levels reveal that fog-water collection is influenced by moisture transport from the Mediterranean, particularly during high fog-collection months. Positive specific humidity anomalies near coastal areas, driven by southeasterly wind anomalies, are crucial for frequent fog formation, while broader, less concentrated anomalies characterize higher-intensity fog events. These findings align with prior research emphasizing the role of cyclonic conditions and maritime moisture advection in enhancing fog-water collection yields. Additionally, seasonal variations in tropospheric circulation anomalies are linked to large-scale teleconnection patterns such as the North Atlantic Oscillation (NAO), Arctic Oscillation (AO), and Eastern Atlantic-Western Russia (EAWR) patterns. These modulate moisture advection, precipitation anomalies, and low-level winds that drive fog formation and collection. In summer, subtropical high-pressure weakening contributes to increased fog-water cumulates, while winter anomalies highlight the impact of quasi-stationary cyclonic circulations and autumn anomalies, positive NAO/AO phases. These results underscore the climatic importance of fog-water collection for water resource management in drought-prone regions and provide a foundation for future climate monitoring and prediction under anthropogenic radiative forcing. The study's insights have practical implications for enhancing water availability through fog collection in Mediterranean ecosystems.

Wildfire activity has decreased in the Valencia Region (Eastern Spain) in the last three decades in ignition and spread terms despite adverse climatological conditions caused by climate change, measured by the Fire Weather Index (FWI) in this study. We divided the study area into seven homogenous regions and split fires by cause to disaggregate the results, and to check for trends in these variables. The most relevant results were: 1) wildfire activity, especially in ignition terms, is decoupled from meteorological danger; 2) annual and interannual FWI variation fits changes in wildfire activity, although the decreasing fires trend masks any significant correlation; 3) summer is the most dangerous season, although large fires and adverse climatological conditions may occur in other seasons; 4) the majority of fires are manmade, with natural fires predominating in the northwest; 5) wildfires undergo significant regional differences that fit the type and intensity of the land use that predominates in each region; 6) the FWI is a good indicator of fire danger, and higher FWI values result in large and abundant fires; 7) responsible action and awareness have resulted in less wildfire activity in recent decades. While the increase in funds and equipment to prevent and combat fires has reduced their impact, ever more adverse conditions in the future caused by climate change will require making more effort to deal with wildfires by placing the focus beyond the warmest summer months.

Land surface temperature (LST) is an essential parameter for studying the effects of climate change. We examined the evolution of LST in the Iberian Peninsula and Balearic Islands (IP-BI) over the 2002-2021 period to identify significant trends associated with climate change. We used LST data retrieved from EOS-Aqua MODIS through the MYD11A1 product (v6.1), which is gridded at a 1-km resolution. Additionally, we utilized the corresponding LST_cci product from the Climate Change Initiative (CCI). The EOS-Aqua satellite passes over the study region twice a day: once in the afternoon (13-15 UTC) and once late at night (1-3 UTC). The Mann-Kendall (MK) test was employed for LST statistical analysis, together with the Sen's slope estimator to evaluate the strength of the statistically significant trends. We conducted the test for each pixel in our study area and for various LST statistics, such as the annual mean, maximum, and minimum LSTs recorded during both overpasses. The results show an average annual trend over the entire IP-BI of 0.1 K/year at daytime and 0.07 K/year at nighttime. We also present the MK test results for each season separately, allowing us to study different phenomena, such as the lengthening of summer and the increase in tropical nights. Finally, we examined the impact of different topological variables, such as vegetation indices, DEM, and continentality, on LST trends. In addition, the limitations of the study, including spatial correlation and type I error, have been addressed, and recommendations for mitigating them in future work have been provided.

El episodio torrencial de octubre de 2024 constituye un evento excepcional, no solo sobre el registro histórico y horario, sino también por mostrar características inusuales que parecen relacionarse con efectos del cambio climático. Este, además de asociarse a una DANA de configuración clásica, contó en superficie con un largo recorrido marítimo desde zonas del Mediterráneo central con temperaturas que sobrepasaban los 24 °C a finales de octubre. De modo que el estudio pone en relación el episodio con la tendencia a aumentar los valores de TSM sobre el Mediterráneo, y en especial con el fuerte in­cremento del contenido de agua disponible en la columna troposférica, que se constata en el estudio a partir de productos de reanálisis (NCEP y ERA5). Así, este episodio parece situarse en el contexto mayor de una tendencia de base al aumento de la potencialidad pluviométrica, y a la “subtropicalización” de condiciones climáticas, dentro del ámbito del este-sureste peninsular. Asimismo, este estudio también constata que ello está en línea con proyecciones climáticas a escenarios futuros de cambio climático que indican un aumento de los extremos pluviométricos en el área de estudio para los próximos años. Así, el estudio presenta proyecciones de extremos diarios de precipitación por downscaling estadístico, con modelos del CMIP6, para el ámbito de la zona cero del episodio. Proyecciones que ya para el escenario más cercano y actualmente en curso señalan la posibilidad de extremos diarios de precipitación un 50 % más elevados para la precipitación más extrema esperable en un periodo de 31 años con respecto a la serie de referencia (1985-2015). Es pues importante trasladar a la sociedad la conclusión de que eventos pluviométricos extremos y sus consecuencias pueden incrementar su frecuencia en los próximos años. Palabras clave: extremos pluviométricos, cambio climático, vapor de agua, Mediterráneo, esce­narios futuros.

This study evaluated the long-term changes in precipitation patterns and drought conditions in one of the key recharge areas of the hydrological system of southern and southeastern Spain, namely, the Sierra de Cazorla y Segura, which contains the headwater sectors of the catchment basins of two important rivers, namely, the Guadalquivir and the Segura. The research covered a period of 70 years (1952–2021) and undertook an exhaustive analysis of data from 348 pluviometric stations. The most relevant results are as follows: (1) most areas experienced a decrease in the precipitation volume and number of rainy days during the study period; (2) summer and winter showed the most significant decreases; (3) weak and moderate precipitation (<40 mm/d) showed significant decreases in both volume and frequency, while heavy precipitation (≥40 mm/d) showed the opposite behavior; (4) the durations of dry periods increased, while the durations of wet periods decreased in most areas; and (5) the SPEI showed an increase under drought conditions. This research underscores the need for water resource management and resilience strategies with interdisciplinary relevance in the face of changing hydrological patterns.

Climate change is altering the temperature and precipitation patterns in the Iberian Peninsula and on the Balearic Islands, with potential impacts on the distribution of plant communities. This study analyses the evolution of bioclimatic units in this region during the 1953–2022 period. Data from 3668 weather stations distributed throughout the study area were analysed. Two 35-year periods (1953–1987 and 1988–2022) were compared to assess changes in macrobioclimates and bioclimates. The results showed expansion of the Mediterranean macrobioclimate, whose total area increased by 6.93%, mainly at the expense of the Temperate macrobioclimate. For bioclimates, a trend towards more xeric and continental conditions was observed in the Mediterranean region, while temperate areas moved towards homogenisation of climate conditions. Likewise, two new bioclimates were detected, which indicate the emergence of new climate conditions. These results suggest a reorganisation of bioclimatic conditions, with particular implications for biodiversity in mountainous and transitional areas, where endemic species face higher risks of habitat loss. This study provides useful information for developing targeted conservation strategies, establishing a baseline for monitoring future changes and developing early warning systems for vulnerable ecosystems, thus supporting the design of climate-adapted conservation measures in the region studied.

The Fire Weather Index (FWI) is a widely used metric to estimate the wildfire risk based on climatological variables. As anthropogenic climate change is expected to increase wildfire risk by affecting the climate of the Mediterranean Iberian Peninsula, we assess the expected increase in wildfire risk during the past decades. For this purpose, we employ a dataset containing daily FWI values in a 0.25 degrees x 0.25 degrees grid for each day of a 52-year period, between 1971 and 2022, and perform a trend analysis at a statistically significant level. We evaluate the relation between FWI and spatial (altitude, latitude, and distance to the sea) variables to look for significant correlations. An analysis is performed at the geographic level by focusing on changes in concrete, relatively homogenous zones (subregions) to broadly study spatial patterns of change. The most relevant results are (1) the FWI shows an increasing trend across the study area (0.01 confidence level); (2) the FWI is determined by temperature variations on a multiyear scale, but annually by more volatile precipitation patterns; (3) the FWI does not uniformly behave across either space or time, and is subject to different variations in different zones; (4) summer and winter are the seasons with the most significant increase, and autumn is the only not significant season; (5) very high or extreme risks are increasingly prevalent across the territory, increasing wildfire risk and (6) the FWI more rapidly rises in areas further north, at a longer distance to the sea and at higher altitudes, with the Iberian System being the most affected region. The increase in wildfire risk requires putting in place more preventive measures. Our study results coincide with climatological trend studies on the region and bridge a knowledge gap as regards the historical climatology of the FWI.

This study examines the spatio-temporal evolution of bioclimatic belts in peninsular Spain and the Balearic Islands from 1953 to 2022 using the World Bioclimatic Classification System and data from 3668 meteorological stations. Findings indicate a shift toward warmer and more arid conditions, with thermotypes showing an increase in mesomediterranean and thermomediterranean types and a decrease in mesotemperate and supratemperate types. Ombrotype analysis revealed a rise in semiarid types and a decline in humid and hyperhumid types. Significant changes occurred in climate transition zones and mountainous regions, where a process of “Mediterraneanisation”—a process characterised by the expansion of warmer and drier conditions typical of Mediterranean climates into previously temperate areas and/or an altitudinal rise in thermotypes—has been observed. The spatial variability of changes in ombrotypes was greater than that in thermotypes, with regions showing opposite trends to the general one. These results highlight the need for adaptive conservation strategies, particularly in mountainous and climate transition areas, where endemic species may face increased vulnerability due to habitat loss and fragmentation. The results of this study provide insight into how climate change is affecting bioclimatological conditions in the Iberian Peninsula and the Balearic Islands.

The accumulation of greenhouse gases in the atmosphere is causing a generalized increase in temperatures. The Mediterranean basin is one of the most affected places on the planet, with effects such as an increase in maximum and minimum temperatures, among others, having been described in the scientific literature. However, in spite of this generalized thermal increase, the Mediterranean region still registers episodes of intense cold, some of them of great intensity and which give rise to episodes of cold waves. That is why the main objective of this work is to analyze the evolution of cold waves in the Mediterranean coast of the Iberian Peninsula, specifically in the province of Alicante, an area of great tourist activity and, therefore, of great economic importance in the country. The study covers a period of 70 years (1947-2016) and uses surface temperature data from a dense network of 92 meteorological observatories, which have been previously subjected to a filling and homogenization process. In turn, it uses the HYSPLIT model to analyze the origin of the identified cold waves. The most relevant results are: (1) A total of 93 cold waves have been registered during the 70 years of study; (2) The most recent decade (2007-2016) has been the one with the largest number of cold waves; (3) The annual number of days with cold wave has been decreasing over time, as well as the duration of cold waves, which are now shorter; (4) February and January are, in this order, the months with the largest number of cold waves, which also occur, to a lesser extent, in December, March and November; (5) In recent decades, cold waves have affected a greater surface area, although it has not been observed that they have been colder; (6) The most frequent cold waves have a maritime origin, while those of continental origin are the ones that cause the greatest impact in terms of surface area. It is important to accurately characterize the cold waves in our territory and to deepen our knowledge of them, so that we can adopt adaptation measures in the context of a climate change scenario. This work serves as a starting point for a study that characterizes cold waves in the entire Mediterranean region of the Iberian Peninsula. The study had the financial support of the projects Tool4Extreme PID2020-118797RBI00 funded by MCIN/AEI/10.13039/501100011033 and PROMETEO/2021/016 funded by Generalitat Valenciana.

A study on fog-water collection potential at the Mediterranean Iberian Peninsula was carried out for the period 2003-2012. The area is denoted by a high population density, with fairly common water restrictions in certain periods during the year. Moreover, climate change projections point out a sharp drop in precipitation for this sector of the western Mediterranean Basin that would aggravate water problems. This work aims to look closely at knowledge of fog-water collection and it presents results about: its behaviour during different seasons of the year; the fog-water collection potential on dry days (precipitation < 1 mm); the influence of site elevation on both collected volumes and the number of days with fog-water collection. To do so, daily fog-water collection data were analysed from 2003 to 2012 with a dense network of 23 fog-water collectors, which run along the Mediterranean coast of the Iberian Peninsula. The most relevant results were: (a) the seasonal periods with the largest recorded fog-water volumes were autumn and spring; the highest percentages of days with fog-water collection were obtained in summer and autumn; (b) on days when precipitation was null or negligible (< 1 mm), maximum daily fog-water captures were considerable and exceeded 25 L m(-2) at more than half the studied sites; (c) the greater the positive difference in elevation between nearby stations, the larger the positive difference in both fog collected volumes and fog days at equal exposition to prevailing winds, differences that increase in the summer period. Mount Muela (Murcia Region), combining a pair of stations only distanced by 600 m but at a 92-m elevation difference, reported a contrast of two times the collected volume at the upper station compared to the lower and an increment of 61% more days with fog occurrence. Mount Montseny (Catalonia), with a pair of stations distanced by 1,600 m horizontally and 398 m in elevation difference, obtained a sixfold variation between stations for fog-water collection and a 73% increment in foggy days.

The objective of the study is to quantify the effect of climate change on the climatic risks associated with droughts and diminished water resources in the eastern Iberian Peninsula. For this purpose, this work analyses the 70-year historical series (1952–2021) of daily rainfall data from 353 meteorological stations. They are located in a key recharge area of the hydrological system, the Sierra de Albarracín, where three important rivers originate, namely the Tagus, the Júcar and the Turia, as do several tributaries of the Guadiana and Ebro rivers. It analyses trends in: annual and seasonal rainfall volumes with specific studies about their intensity according to certain percentiles; the number of rainy days, dry spell duration (< 1 mm/day) and drought evolution with the Standardized Precipitation Evaporation Index. The most relevant results are: (1) the second 35 years of the study period (1987–2021) were notably drier than the first part (1952–1986), with smaller volumes and fewer days with recorded precipitation; (2) summer and winter were most affected by pluviometric decrease, with losses of >50% of rainfall volume at some stations; (3) moderate rainfall significantly reduced between the 50th and 95th percentiles, which were more important in the system's water recharge; (4) the stations with a negative precipitation trend predominated; (5) the medium- and long-term analyses (12 and 36 months) highlighted the drought situation in which the headwaters of the analyzed basins are immersed. The trend indicates that the situation will become critical.

An experimental site was selected for fog- and rain-water quality analyses. The selected location corresponds to Mount Monduver of 843 m elevation, being geographically centered in the Mediterranean Iberian Peninsula. Single fog- and rain-water samples were taken manually with a dedicated fog and rain collectors, to prevent any contamination with dry-deposition. Besides, a permanently exposed fog collector and a rain gauge were also used for the collection of water samples affected by dry deposition. Results indicated that all chemical analyses complied with Spanish drinking water regulations, except for the particular case of the dry-deposition contaminated water samples. A further statistical data analysis, together with five-day air mass backward trajectories, was performed. Two sample clusters could be differentiated which were also discriminated against by the two principal components obtained. Cluster-1 members comprised higher levels of conductivity and ion concentration, while cluster-2 members corresponded to lower levels of solutes. The second principal component related to pH levels showed the majority of samples centered at neutral values. The backward trajectory analysis indicated that the origin and route followed by the air masses leading to sample members in cluster-1 were over the Mediterranean Sea and mainly obtained in summer and autumn; while trajectories associated to sample members in cluster-2 had their origin primarily over the Atlantic Sea occurring only in winter and spring. The larger ion loads presented in fogs developed from Mediterranean air masses may be explained through the role of sea breezes on the confinement of pollutants into the atmosphere.

Fog-water collection has been widely analysed for its quantification and potential uses; however, there are few studies assessing the synoptic conditions and large-scale teleconnection patterns that affect its occurrence. Focusing on the Mediterranean Iberian Peninsula, this work aims to analyse the synoptic patterns, both at surface level and 850 hPa geopotential height, that most likely to favour fog-water collection, and to quantify the relationship between fog-water collection and the NAOi (North Atlantic Oscillation index), MOi (Mediterranean Oscillation index) as well as WeMOi (Western Mediterranean Oscillation index) teleconnection patterns. For this purpose, daily fog-water observations from a dense network of 23 fog-water collectors located along the Mediterranean Iberian Peninsula for 2003-2012 were analysed in relation to synoptic patterns and the three-teleconnection indices. The major findings are: (a) The most favourable synoptic patterns for fog-water collection are maritime advections carrying humidity from the Mediterranean basin, and cyclonic circulations, whereas anti-cyclonic situations generally led to large number of foggy days with low fog-collection rates. (b) In terms of winds at 850 hPa, the most favourable low-level flows for fog-water collection are associated with strong winds (>5.1 m s(-1)) from the Mediterranean. Atlantic winds generally cause a greater number of fog days than Mediterranean winds, with less fog-water collection rates. (c) WeMOi has the greatest influence on fog-water collection, mainly during winter and spring months, with statistically significant negative relationships for most of the stations. MOi also shows a great influence, with a large number of statistically significant negative correlations, mainly during the same months as WeMOi. Lastly, NAOi presented the lowest and no significant negative correlations with fog-water collection.

Among the different inputs involved in the hydrological system, fog water measured by man-made passive devices is one of the most unknown components, although it could be an additional water resource for specific environmental applications (forest restoration, forest firefighting, etc.). Focusing on the Mediterranean Iberian Peninsula, the aim of this work is to quantify fog-water collected by a 24-fog-stations network spread across three latitudinal sectors with different locations (coastal, pre-littoral and inland), and to determine the most productive sites. Measurements from the network show that distance-to-sea, latitude or elevation differences between stations are factors affecting fog-water collection potential. The network, based on passive cylindrical omnidirectional fog-water collectors, was active during the period 2003-2012. In addition to fog collection, other environmental variables such as rainfall, wind speed and wind direction, air temperature and relative humidity were measured. These ancillary data were used in a specific data reduction technique to eliminate the simultaneous rainwater component from the fog water measurements, and in the retrieval of the optimum mean wind directions to harvest fog-water efficiently. It was concluded that (i) positive differences in elevation allow greater collection rates, even under 100 m differences; (ii) optimum harvesting wind directions for inland locations are in line with the orientation of the existent valley coupled with the shortest path to the coastline, their collected fog-water volumes being generally smaller than those near the coast; (iii) fog-water collection at coastal locations present more dispersed optimal wind directions, ranging from north to the direction of the most immediate coastline; and (iv) there is a practically null dependence of the optimum mean wind direction on seasonality, but a strong dependence of fog-water captured volumes, however.