Where does the link between atmospheric moisture transport and extreme precipitation matter?

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGAtmospheric moisture transport is the primary component of the atmospheric branch of the water cycle, and its anomalies strongly influence drought and precipitation extremes. We utilised the full geographical and temporal spectrum of the ERA-5 reanalysis data and extreme value theory to identify regions where the atmospheric moisture transport, quantified as local integrated moisture vertical transport (IVT), influences daily extreme precipitation, and where this influence has a relevant dynamic component, which may alter the dependency between IVT and extreme precipitation as temperatures increase with climate change. We showed that this dependency is weak or negligible in tropical regions and strong but nonuniform in extratropical regions. Its influence is much greater in areas where the main moisture transport mechanisms occur, namely, atmospheric rivers, low-level jets, and tropical cyclones. The dynamic component of IVT, linked to wind, is highly consequential in regions with landfalling atmospheric rivers, landfalling tropical cyclones, or moisture-transporting low-level jets.Agencia Estatal de Investigación | Ref. PID2021-122314OB-I00Xunta de Galicia | Ref. ED431C 2021/4

Combinations of drivers that most favor the occurrence of daily precipitation extremes

Previous studies indicate atmospheric instability, total column water vapor, and horizontal moisture transport as major drivers of precipitation extremes, however little is known about how the combination of these drivers affects precipitation extremes across the world. Here, using daily data from the ERA-5 reanalysis spanning the period 1981–2020, we identified the combinations of extreme values for these three major drivers that enhance the probability of daily precipitation extremes on a global scale. Our findings show that extreme daily precipitation is practically impossible without any of these drivers being extreme. Atmospheric instability is the primary driver of precipitation extremes, meaning that, among the three cases of the drivers being extreme in isolation, extreme atmospheric instability is associated with the highest average probability of extreme precipitation over landmasses (29% during December–February, 32% during June–August). When considering the combination of two drivers being simultaneously extreme, joint extremes of atmospheric instability and total column water vapor (and non-extreme horizontal moisture transport) lead to the highest probability of extreme precipitation (69% during December–February, 70% during June–August), which is similar to the probability under three drivers in extreme conditions (67% and 72%). Our results point to a latitudinal variation of the combination that leads to the highest probability of extreme precipitation. In subtropics, the case of the three extreme drivers dominates, whereas in extratropical regions, the dominant combination is that of the joint extremes of atmospheric instability and total column water vapor (and non-extreme horizontal moisture transport). By providing information on the most important drivers of precipitation extremes worldwide, these results can serve as a basis for evaluating precipitation extremes in climate models and understanding projected changes, which is vital for developing robust risk assessments.Agencia Estatal de Investigación | Ref. PID2021-122314OB-I00Xunta de Galicia | Ref. ED431C 2021/44Universidade de Vigo/CISU

The influence of maritime spatial planning on the development of marine renewable energies in Portugal and Spain: legal challenges and opportunities

The objective of this study is to analyse, from a legal point of view, the influence of the transposition of Marine Spatial Planning Directive into both Spanish and Portuguese domestic laws on the development of marine renewable energies in both countries. This article concludes that the Portuguese legal system is more favourable for the development of marine renewable energies than the Spanish legal regime, since the former establishes a more flexible planning system, sets criteria for the prioritisation of marine uses, incorporates trade-off mechanisms, introduces an electronic single-window system and regulates a pilot zone. These measures can help streamline licensing processes, avoid and resolve conflicts with other sea users, and adapt planning instruments to the rapid development of new marine renewable technologies. However, both legal regimes lack specific legal mechanisms aimed at offering effective protection of the marine environment against negative effects arising from the installation of such devices. Similarly, there is a lack of coordination between maritime spatial planning instruments and land planning instruments, and between the Central Government and the autonomous regions. This may hinder the installation of marine renewable energies. This study has implications in relation to the EU integrated marine policy aimed at achieving a balance between blue growth and the conservation of the marine environment, as well as an inter-administrative coordination improvement in decision-making.Xunta de Galicia | Ref. ED481A-2016/36Programa IACOBUS (Galicia-North Portugal Euroregion

A database of optimal integration times for Lagrangian studies of atmospheric moisture sources and sinks

Lagrangian methods for estimating sources and sinks of water vapour have increased in importance in recent years, with hundreds of publications over the past decade on this topic. Results derived from these approaches are, however, very sensitive to the integration time of the trajectories used in the analysis. The most widely used integration time is that derived from the average residence time of water vapour in the atmosphere, normally considered to be around 10 days. In this article, we propose an approach to estimate the optimal integration time for these Lagrangian methods for estimating sources and sinks, by comparing estimates of precipitation from the Lagrangian approach using different times of integration with results obtained from three state-of-the-art reanalyses, thereby providing a database of optimal integration times per month, for a spatial resolution of 0.25° × 0.25° in latitude and longitude.Ministerio de Ciencia e Innovación | Ref. CGL2015-65141-RXunta de Galicia | Ref. ED431C 2017/64-GR

The role of moisture transport for precipitation in the inter-annual and inter-daily fluctuations of the Arctic sea ice extension

By considering the moisture transport for precipitation (MTP) for a target region to be the moisture that arrives in this region from its major moisture sources and which then results in precipitation in that region, we explore (i) whether the MTP from the main moisture sources for the Arctic region is linked with inter-annual fluctuations in the extent of Arctic sea ice superimposed on its decline and (ii) the role of extreme MTP events in the inter-daily change in the Arctic sea ice extent (SIE) when extreme MTP simultaneously arrives from the four main moisture regions that supply it. The results suggest (1) that ice melting at the scale of inter-annual fluctuations against the trend is favoured by an increase in moisture transport in summer, autumn, and winter and a decrease in spring and, (2) on a daily basis, extreme humidity transport increases the formation of ice in winter and decreases it in spring, summer, and autumn; in these three seasons extreme humidity transport therefore contributes to Arctic sea ice melting. These patterns differ sharply from that linked to the decline on a long-range scale, especially in summer when the opposite trend applies, as ice melt is favoured by a decrease in moisture transport for this season at this scale.Ministerio de Ciencia e Innovación | Ref. CGL2015-65141-

A new pattern of the moisture transport for precipitation related to the drastic decline in Arctic sea ice extent

In this study we use the term moisture transport for precipitation for a target region as the moisture coming to this region from its major moisture sources resulting in precipitation over the target region (MTP). We have identified changes in the pattern of moisture transport for precipitation over the Arctic region, the Arctic Ocean, and its 13 main subdomains concurrent with the major sea ice decline that occurred in 2003. The pattern consists of a general decrease in moisture transport in summer and enhanced moisture transport in autumn and early winter, with different contributions depending on the moisture source and ocean subregion. The pattern is statistically significant and consistent with changes in the vertically integrated moisture fluxes and frequency of circulation types. The results of this paper also reveal that the assumed and partially documented enhanced poleward moisture transport from lower latitudes as a consequence of increased moisture from climate change seems to be less simple and constant than typically recognised in relation to enhanced Arctic precipitation throughout the year in the present climate.Secretaría de Estado de Investigación, Desarrollo e Innovación | Ref. CGL2015-65141-

Development of offshore wind power: contrasting optimal wind sites with legal restrictions in Galicia, Spain

The region of Galicia, in the northwest of the Iberian Peninsula, has a high wind potential for the installation of offshore wind farms (OWFs) in many areas of its surrounding marine waters. However, legal restrictions derived from the protection of other interests that converge in the marine environment (such as fishing, navigation, and biodiversity conservation) must be considered, along with technical limitations resulting from water depth. This study is aimed at analysing legal restrictions on the installation of OWFs in Galician waters and at identifying those zones of less conflict where the wind power density (WPD) is greater and the depths and distances from the coast are technically feasible given the current status of technology in Europe. To do this, a legal study was performed of both the strategic environmental assessment of the Spanish coast and the regulations of the different marine sectors at European, international, national, and regional levels. In addition, the WPD along the north-western area of the Iberian Peninsula and Europe was calculated, and an analysis of maximum and average depths and distances from the coast of planned and installed OWFs in Europe was made. Two main zones without legal and technical restrictions were identified in the north-eastern corner of Galicia and in the south of the Vigo estuary. The greatest WPD was identified in the north-western zone, from Cape Finisterre to Cape Ortegal, where there are small sites without legal or technical restrictions that are near several protected zones (such as a marine reserve, a special protected area, and a wetland and its buffer zone), making necessary a deeper analysis of the specific impacts of each OWF project in the Environmental Impact Assessment.Xunta de Galicia | Ref. ED481A-2016/36Fundação para a Ciência e a Tecnologia | Ref. SFRH/BPD/118142/201

The growing importance of oceanic moisture sources for continental precipitation

The precipitation that falls on the continents defines the extent and nature of terrestrial ecosystems and human activity in them, all of which are adapted to and maintained by present-day precipitation. In essence, precipitation is supplied by moisture that either comes directly from the ocean, or is subsequently recycled from the continents themselves. Both the processes that control evaporation and the main mechanisms of moisture transport clearly differ between the ocean and the continent, thus within the context of a changing climate, it may be expected that the relationship between precipitation of oceanic and terrestrial origin varies globally and regionally, as will the influence of these two basic components of total precipitation on global and regional precipitation trends, especially in tropical regions. We describe an approach based on a Lagrangian technique for estimating the precipitation in a target region given the proportions of moisture transported from the two sources (ocean and continent) to reveal that the percentage of precipitation of oceanic origin has increased globally in the current climate (1980–2016). The greatest observed rate of increase is in the tropical regions; furthermore, the trends of precipitation in these regions are controlled by trends in precipitation for which the source of moisture is the ocean.Agencia Estatal de Investigación | Ref. RTI2018-095772-B-I00Xunta de Galicia | Ref. ED481B 2019/070Xunta de Galicia | Ref. ED431C 2017/64-GR

Space-time causality analysis of regional impacts of ENSO on terrestrial and oceanic precipitation

Future changes are expected in precipitation under climate change, therefore, changes are projected in the oceanic and terrestrial components. However, it remains poorly elucidated how the El Niño–Southern Oscillation (ENSO) can influence these changes. Therefore, we aimed to perform a space-time causality analysis of regional ENSO impacts on terrestrial and oceanic precipitation by using the Granger causality method as a function of eight temporal lags (lags 1–8). The monthly values of total precipitation obtained using the Lagrangian approach and their respective terrestrial (PLT) and oceanic (PLO) components were used. The analysis was performed for the two regions of western North America (WNA) and eastern South America (ESA) with strong ENSO signals. For the WNA region in winter, the maximum Granger causality was observed in the component of oceanic origin for temporal lags 1 and 2 (3 and 6 months), with a predominance of both positive and negative ENSO conditions. For the ESA region, it was verified that the causality of the ENSO index was maximum for PLT. Temporal lags 2–5 (6–15 months) stood out in winter when there was a marked region of the Granger causality over the La Plata Basin. In autumn, for lags 1–4 (3–12 months), the Granger causality values were predominant in the southern and western areas of ESA and showed a tendency to move northward with an increased temporal lag. Finally, it was shown that high correlation values did not imply the causality of the relationship between the ENSO index and precipitation in the two regions.Xunta de Galicia | Ref. ED431C 2021/44Xunta de Galicia | Ref. ED481A-2020/193Ministerio de Ciencia, Innovación y Universidades | Ref. PID2021-122314OB-I0

Stable isotope signatures in Tehran’s precipitation: insights from artificial neural networks, stepwise regression, wavelet coherence, and ensemble machine learning approaches

This study investigates the impact of precipitation on Middle Eastern countries like Iran using precise methods such as stable isotope techniques. Stable isotope data for precipitation in Tehran were obtained from the Global Network of Isotopes in Precipitation (GNIP) station and sampled for two periods: 1961–1987 and 2000–2004. Precipitation samples were collected, stored, and shipped to a laboratory for stable isotope analyses using the GNIP procedure. Several models, including artificial neural networks (ANNs), stepwise regression, and ensemble machine learning approaches, were applied to simulate stable isotope signatures in precipitation. Among the studied machine learning models, XGboost showed the most accurate simulation with higher R2 (0.84 and 0.86) and lower RMSE (1.97 and 12.54), NSE (0.83 and 0.85), AIC (517.44 and 965.57), and BIC values (531.42 and 979.55) for 18O and 2H compared to other models, respectively. The uncertainty in the simulations of the XGboost model was assessed using the bootstrap technique, indicating that this model accurately predicted stable isotope values. Various wavelet coherence analyses were applied to study the associations between stable isotope signatures and their controlling parameters. The BWC analysis results show coherence relationships, mainly ranging from 16 to 32 months for both δ18O–temperature and δ2H–temperature pairs with the highest average wavelet coherence (AWC). Temperature is the dominant predictor influencing stable isotope signatures of precipitation, while precipitation has lower impacts. This study provides valuable insights into the relationship between stable isotopes and climatological parameters of precipitation in Tehran.Xunta de Galicia | Ref. ED431C 2021/4