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We assess the spatial structure of moisture flux divergence, regional moisture sources and transport processes over Colombia, in northern South America. Using three independent methods the dynamic recycling model (DRM), FLEXPART and the Quasi-isentropic back-trajectory (QIBT) models we quantify the moisture sources that contribute to precipitation over the region. We find that moisture from the Atlantic Ocean and terrestrial recycling are the most important sources of moisture for Colombia, highlighting the importance of the Orinoco and Amazon basins as regional providers of atmospheric moisture. The results show the influence of long-range cross-equatorial flow from the Atlantic Ocean into the target region and the role of the study area as a passage of moisture into South America. We also describe the seasonal moisture transport mechanisms of the well-known low-level westerly and Caribbean jets that originate in the Pacific Ocean and Caribbean Sea, respectively. We find that these dynamical systems play an important role in the convergence of moisture over western Colombia.

The Colombian Andes (CA) are located over the northwestern corner of tropical South America (NW‐TropSA), where land and atmosphere interchange moisture and energy in a complex way owing to the orographic influence on the recycling of moisture over land. We aim to understand where and when water vapor evaporated from land turns into rainfall through moisture recycling, using the Water Accounting Model‐2layers (WAM‐2), an offline model to track atmospheric moisture forced with data from ERA‐5 at its native 0.25° resolution during 1980–2020. We define the spatiotemporal distribution of sources (high evaporation recycle ratios, ϵC) and receptors (high precipitation recycle ratios, ρC) of continental moisture at diverse timescales, including monthly, seasonal, annual and interannual (ENSO). Referring to the regional runs of WAM‐2 over NW‐TropSA (4°S–12°N/80°W–66°W), at elevations above 1,000 m.a.s.l., the CA has a mean annual ρC of 11% (ranging 6%–16%) and a mean annual ϵC of 35% (ranging 27%–40%). Moisture recycling in the CA exhibits a strong annual cycle over the region. The seasonal dynamic of moisture recycling shows two clear‐cut sources of moisture: the eastern foothills of the Eastern and Central ranges of the CA. Both foothills are also regions of high rainfall, although moisture recycling mechanisms differ. Sources of continental moisture grow spatially during September‐October‐November and March‐April‐May. The seasonal availability of moisture recycled coincides with regions where orography interacts with low level jets sourcing humidity. At interannual timescales, sources and receptors of continental moisture in the CA are modulated by the extreme phases of ENSO. Key Points The orography of the Colombian Andes emerged as a critical factor shaping the interaction between land and atmospheric moisture fluxes Foothills and valleys of the Colombian Andes play a pivotal role in continental moisture recycling, in terms of convergence and divergence ENSO modulates both sources and receptors of continental moisture at interannual timescales

Warming induced by increased greenhouse gas emissions is intensifying the global water cycle and increasing the water vapor content of the global atmosphere. However, there is a lack of scientific literature assessing how regional atmospheric moisture transport and recycling will change in a warming climate. This work analyzes the projections of atmospheric moisture transport and recycling over tropical South America by the end of the twenty-first century (2070–2100) under a climate change scenario (RCP8.5). We used the Dynamic Recycling Model to estimate atmospheric moisture contributions to the region considering input data from the European Centre for Medium-Range Weather Forecasts ERA5 reanalysis and 11 models included in the Fifth Phase of the Coupled Model Intercomparison Project. Projected increases of precipitable water in tropical South America are linked with increased evaporation from the oceans. However, those projections also indicate (1) reductions in the precipitation contributed by the main atmospheric moisture sources to the continental regions of tropical South America, (2) reductions of total precipitation, and (3) reductions of recycled precipitation over the region. The largest reductions of precipitation recycling are projected over the southern Amazon during the dry-to-wet transition season (about 31%) and the northern Amazon during its dry season (about 25%). This is particularly relevant since the southern Amazon has experienced the occurrence of longer dry seasons during the recent decades and has been highlighted as a hotspot of climate change.

Poleward atmospheric moisture transport （AMT） into the Arctic Ocean can change atmospheric moisture or water vaporcontent and cause cloud formation and redistribution, which may change downward longwave radiation and, in turn, surfaceenergy budgets, air temperatures, and sea-ice production and melt. In this study, we found a consistently enhanced polewardAMT across 60°N since 1959 based on the NCAR-NCEP reanalysis. Regional analysis demonstrates that the poleward AMTpredominantly occurs over the North Atlantic and North Pacific regions, contributing about 57% and 32%, respectively, to thetotal transport. To improve our understanding of the driving force for this enhanced poleward AMT, we explored the role thatextratropical cyclone activity may play. Climatologically, about 207 extratropical cyclones move across 60°N into the ArcticOcean each year, among which about 66 （32% of the total） and 47 （23%） originate from the North Atlantic and North PacificOcean, respectively. When analyzing the linear trends of the time series constructed by using a 20-year running window, wefound a positive correlation of 0.70 between poleward yearly AMT and the integrated cyclone activity index （measurementof cyclone intensity, number, and duration）. This shows the consistent multidecadal changes between these two parametersand may suggest cyclone activity plays a driving role in the enhanced poleward AMT. Furthermore, a composite analysisindicates that intensification and poleward extension of the Icelandic low and accompanying strengthened cyclone activityplay an important role in enhancing poleward AMT over the North Atlantic region.

The southeastern Amazon has recently been shown to be a net carbon source, which is partly caused by drying conditions. Drying depends on a number of factors, one of which is the land cover at the locations where the moisture has originated as evaporation. Here we assess for the first time the origins of the moisture that precipitates in the Amazon carbon source region, using output from a Lagrangian atmospheric moisture tracking model. We relate vegetation productivity in the Amazon carbon source region to precipitation patterns and derive land-cover data at the moisture origins of these areas, allowing us to estimate how the carbon cycle and hydrological cycle are linked in this critical part of the Amazon. We find that, annually, 13% of the precipitation in the Amazon carbon source region has evaporated from that same area, which is half of its land-derived moisture. We further find a moisture-recycling-mediated increase in gross primary productivity of roughly 41 Mg carbon km −2 yr −1 within the Amazon carbon source region if it is fully forested compared to any other land cover. Our results indicate that the parts of the Amazon forest that are already a net carbon source, still help sustain their own biomass production. Although the most degraded parts of the Amazon depend mostly on oceanic input of moisture, further degradation of this region would amplify carbon losses to the atmosphere.

The timing of melt onset in the Arctic plays a key role in the evolution of sea ice throughout Spring, Summer and Autumn. A major catalyst of early melt onset is increased downwelling longwave radiation, associated with increased levels of moisture in the atmosphere. Determining the atmospheric moisture pathways that are tied to increased downwelling longwave radiation and melt onset is therefore of keen interest. We employed Self Organizing Maps (SOM) on the daily sea level pressure for the period 1979–2018 over the Arctic during the melt season (April–July) and identified distinct circulation patterns. Melt onset dates were mapped on to these SOM patterns. The dominant moisture transport to much of the Arctic is enabled by a broad low pressure region stretching over Siberia and a high pressure over northern North America and Greenland. This configuration, which is reminiscent of the North American-Eurasian Arctic dipole pattern, funnels moisture from lower latitudes and through the Bering and Chukchi Seas. Other leading patterns are variations of this which transport moisture from North America and the Atlantic to the Central Arctic and Canadian Arctic Archipelago. Our analysis further indicates that most of the early and late melt onset timings in the Arctic are strongly related to the strong and weak emergence of these preferred circulation patterns, respectively.

Global warming mechanisms that cause changes in frequency and intensity of precipitation in the tropics are examined in climate model simulations. Under global warming, tropical precipitation tends to be more frequent and intense for heavy precipitation but becomes less frequent and weaker for light precipitation. Changes in precipitation frequency and intensity are both controlled by thermodynamic and dynamic components. The thermodynamic component is induced by changes in atmospheric water vapor, while the dynamic component is associated with changes in vertical motion. A set of equations is derived to estimate both thermodynamic and dynamic contributions to changes in frequency and intensity of precipitation, especially for heavy precipitation. In the thermodynamic contribution, increased water vapor reduces the magnitude of the required vertical motion to generate the same strength of precipitation, so precipitation frequency increases. Increased water vapor also intensifies precipitation due to the enhancement of water vapor availability in the atmosphere. In the dynamic contribution, the more stable atmosphere tends to reduce the frequency and intensity of precipitation, except for the heaviest precipitation. The dynamic component strengthens the heaviest precipitation in most climate model simulations, possibly due to a positive convective feedback.

Rainfed crops account for approximately 40% of India’s food production and support 60% of its livestock. Although linked to oceanic monsoon rainfall, their productivity also depends on terrestrially-sourced rainfall, particularly in the non-monsoon season. The degree to which rainfed crops rely on moisture sourced from evaporation in upwind irrigated areas remains largely unknown. Using a combination of models and observations, we show that evaporation from upwind irrigated crops contributes 7% (mean) ± 5% (spread) of the rainfall over rainfed areas annually, rising to 15 ± 10% during the pre-monsoon months (averaged over the years 2000–2020). In the absence of this input, water stress experienced by rainfed crops can increase by 5%–10% during the crucial mid to late crop growth phases, potentially affecting yields. Our results reveal an unrecognized atmospheric link between irrigated and rainfed agriculture that is overlooked in current agricultural policies. Planning and managing these systems holistically can help strengthen regional food and water security under future climates.

In recent decades, the Upper Paraguay River Basin (UPRB) has experienced increasingly frequent and intense wildfires, often linked to severe droughts. While these events reflect broader hydrological imbalances driven by changes in precipitation and atmospheric moisture support, the role of moisture sources in modulating drought–fire dynamics remains unclear. This study addresses this gap by identifying key moisture sources for the UPRB and analyzing their shifts during extreme drought years coinciding with high fire. We assessed the drought–fire relationship through correlations between the Standardized Precipitation‐Evapotranspiration Index (SPEI) and burned area (1986–2018), selecting the top‐3 extreme drought years using the SPEI‐based rarity index (|R|), and using the Lagrangian FLEXPART model outputs to track changes in moisture contributions. Results reveal a strong SPEI‐burned area correlation, 2007, 2010, and 1999 being the top‐3 extreme drought years aligning with peak wildfire activity. These years exhibited notable shifts in moisture contributions, particularly with persistent negative anomalies during the dry‐season, reinforcing the occurrence of extremes. The most severe droughts were preceded by contrasting wet‐season moisture conditions and consistently followed by strong dry‐season deficits, particularly from key continental and ocean sources, contributing to drought intensification. While drought severity modulates wildfire risk, fire occurrence and extent also reflect the influence of multiple interacting factors. The findings highlight the importance of moisture source dynamics in shaping drought–fire interactions. The Upper Paraguay River Basin faced intense droughts in 1999, 2007, and 2010, coinciding with extensive wildfires. In 2007, a severe drought episode affected 97.5% of its area. These extreme years were characterized by pronounced negative anomalies and shifts in atmospheric moisture contributions from key source regions, during dry season.

Atmospheric moisture transport governs oceanic evaporation with terrestrial water availability. However, its role in regulating vegetation activity in arid coastal ecosystems is still poorly understood. In particular, how transient circulation anomalies, such as coastal El Niño events, modify atmospheric moisture conditions and relate to vegetation dynamics at broader spatial scales has received limited attention. This study combines an event-based analysis of atmospheric moisture transport during the 2017 coastal El Niño in northern Peru with a global statistical analysis of vegetation-moisture relationships. Low-level moisture transport pathways and moisture properties were examined using backward trajectory analysis. Vegetation activity was represented by leaf area index. Spatial correlations between leaf area index and water vapor transport were evaluated within coastal buffer zones and across global land grid cells. The 2017 coastal El Niño was associated with a clear reorganization of low-level moisture transport pathways, with four dominant trajectory clusters identified compared to three in 2009. The largest equatorial Pacific pathway accounted for approximately 60% of trajectories in 2017, whereas two southeastern Pacific clusters represented nearly 90% of trajectories under normal conditions. Air parcels reaching the Peruvian coast contained substantial higher moisture content, with specific humidity frequently exceeding 15 g/kg compared to generally below 10 g/kg in 2009. This indicates significantly altered near-surface atmospheric conditions. At the global scale, relationships between leaf area index and water vapor transport varied strongly across regions. Positive associations were mainly observed in moisture-limited regions, particularly across large parts of the Southern Hemisphere and several arid coastal zones. In contrast, negative or weak associations dominated humid tropical regions and much of the Northern Hemisphere. These results indicate that atmospheric moisture transport influences vegetation activity in a region-dependent manner. Its role is more pronounced in arid and moisture-limited environments than in humid regions. By linking an event-scale moisture transport anomaly with global vegetation-moisture relationships, this study provides insight into vegetation sensitivity to circulation-driven moisture variability, particularly in arid coastal ecosystems.