This study assessed the projected near-surface wind speed (SWS) changes and variability over the Iberian Peninsula for the 21st century. Here, we compared Coupled Model Intercomparison Project Phase ...6 global climate models (GCMs) with a higher spatial resolution regional climate model (RCM; ∼20 km), known as WRF-CESM2, which was created by a dynamic downscaling of the Community Earth System Model version 2 (CESM2) using the Weather Research and Forecasting (WRF) model. Our analysis found that the GCMs tended to overestimate observed SWS for 1985-2014, while the higher spatial resolution of the WRF-CESM2 did not improve the accuracy and underestimated the SWS magnitude. GCMs project a decline of SWS under high shared socioeconomic pathways (SSPs) greenhouse concentrations, such as SSP370 and SSP585, while an interdecadal oscillation appears in SSP126 and SSP245 for the end of the century. The WRF-CESM2 under SSP585 predicts the opposite increasing SWS. Our results suggest that 21st-century projections of SWS are uncertain even for regionalized products and should be taken with caution.
In this study, we investigated the changes in the origin of moisture for the precipitation associated with tropical cyclones (TCs) after extratropical transition (ET) over the North Atlantic Ocean ...basin from 1980 to 2018. We analyzed the 24 hr before and after the occurrence of ET events. By applying a TC‐centric methodology we found that the moisture uptake (MU) occurred predominantly in the south and southwest sectors within ∼2,000 km of TC center before ET and from the southwest and west sectors after ET. In addition, the development of the cold front and the warm conveyor belt after ET induces changes in the moisture transport pattern. Overall, the secondary circulation of TCs favored the moisture flux inward for TCs precipitation, while the large‐scale baroclinic environment controlled the MU after ET.
Plain Language Summary
Tropical cyclones (TCs) are one of the weather systems that often cause fatalities and strong damage to socioeconomic infrastructures in tropical and subtropical latitudes. During the poleward movement, they can undergo an extratropical transition (ET), experiencing notable changes in their structure, such as the replacement of the warm core with a cold core and an increase in the area of the precipitation pattern. In this study, we investigate the changes in the moisture sources' contribution to the precipitation within the TCs' outer radius before and after ET over the North Atlantic Ocean basin. Our results show that the moisture sources were mainly located in the south and southwest sectors within ∼2,000 km of the TC center before ET and in the southwest and west sector after ET. Additionally, the large‐scale baroclinic environment modulated the moisture transport pattern after ET. These findings contribute to improving our knowledge about the changes in a TC during the ET event.
Key Points
The west North Atlantic Ocean was identified as the main moisture source, accounting for ∼44%–69% of total moisture uptake
The moisture was predominately originated from the south and southwest sectors during PRE‐extratropical transition (ET) and from the southwest‐west during POST‐ET
The large‐scale baroclinic environment controlled the moisture transport for tropical cyclones precipitation after ET
Abstract
Global warming and associated changes in atmospheric circulation patterns are expected to alter the hydrological cycle, including the intensity and position of moisture sources. This study ...presents predicted changes for the middle and end of the 21st century under the SSP5-8.5 scenario for two important extratropical moisture sources: the North Atlantic Ocean (NATL) and Mediterranean Sea (MED). Changes over the Iberian Peninsula—considered as a strategic moisture sink for its location—are also studied in detail. By the end of the century, moisture from the NATL will increase precipitation over eastern North America in winter and autumn and on the British Isles in winter. Moisture from the MED will increase precipitation over the southern and western portions of the Mediterranean continental area. Precipitation associated with the MED moisture source will decrease mainly over eastern Europe, while that associated with the NATL will decrease over western Europe and Africa. Precipitation recycling on the Iberian Peninsula will increase in all seasons except summer for mid-century. Climate change, as simulated by CESM2 thus modifies atmospheric moisture transport, affecting regional hydrological cycles.
In this study, we investigated the moisture sources for precipitation through a Lagrangian approach during the genesis, intensification, and dissipation phases of all tropical cyclones (TCs) that ...occurred over the two hemispheric sub-basins of the Indian Ocean (IO) from 1980 to 2018. In the North IO (NIO), TCs formed and reached their maximum intensity on both sides of the Indian Peninsula, to the east in the Bay of Bengal (BoB), and to the west in the Arabian Sea (AS). The oceanic areas where TCs occurred were their main moisture sources for precipitation associated with TCs. Additionally, for TCs over the BoB, continental sources from the Ganges River basin and the South China Sea also played a notable role; for TCs over the AS, the Somali Low-Level jet (along the African coast in a northerly direction) also acted as an essential moisture transport. In the South IO (SIO), the western, central, and eastern basins were identified as the preferred areas for the genesis and development of TCs. During TC activity, the central IO and the Wharton and Perth basins mostly supplied atmospheric moisture. The Mascarene High circulation was the main moisture transport mechanism for the precipitation of TCs formed in the SIO basin. In both basins, during their intensification process, TCs gained more moisture (even more intensely when reaching the hurricane category) than during the genesis or dissipation stages. Additionally, the modulation during monsoonal seasons of the moisture contribution to the TCs was more noticeable over the NIO basin than for the SIO. Overall, the moisture uptake for precipitation from the sources for TCs occurred slightly faster in the NIO basin than in the SIO basin.
Abstract
Tropical cyclones (TCs) are an important component of the hydrological cycle at tropical latitudes. In this study, we investigated the origin of precipitation associated with TCs formed from ...1980 to 2018 over the Pacific Ocean in three subbasins: the western North Pacific Ocean (WNP), central and east Pacific Ocean (NEPAC), and South Pacific Ocean (SPO) basins. The analysis was performed throughout the TC lifetime during genesis, when they reached the lifetime maximum intensity (LMI), and the dissipation stage. The backward trajectories of all precipitant atmospheric parcels residing over the TC locations from the global outputs of the Lagrangian Flexible Particle (FLEXPART) dispersion model fed by the ERA-Interim dataset were used to identify moisture sources. The South and East China Seas and the western tropical North Pacific Ocean were identified as the principal moisture sources in the WNP basin, while the atmospheric moisture that precipitated mainly came from the eastern tropical North and South Pacific Ocean in the NEPAC basin, followed by the Caribbean Sea. Meanwhile, the Coral Sea, western tropical South Pacific Ocean, and northern Australia are the origins of the moisture in the SPO. The mean moisture uptake per TC was higher during the hurricane category than during any other stage in each basin.
Extreme summer precipitation events commonly affect the Iberian Peninsula (IP), and studying the moisture sources that generate intense precipitation is extremely important. Therefore, this study ...analyzed the moisture sources of two major extreme precipitation events in summer in the IP. The events occurred on 18 September 1999 and 7 September 1989, and the anomalies of the associated meteorological variables are shown with respect to a 30-year reference period (1985–2014). A Lagrangian approach is used for determining the moisture source pattern using only the precipitating particles that reach the target region. In this research a dynamic downscaling methodology is applied using the WRF-ARW model forced using the ERA5 reanalysis and then the WRF-ARW outputs used to force the Lagrangian dispersion model FLEXPART-WRF. Specifically, the first event was associated with an atmospheric river favoring strong moisture transport from remote sources and the second event was caused by local convergence of moisture under the influence of a cut-off low system. For the 18 September 1999 case study, the major contribution to moisture reaching the target region was associated with the central and eastern North Atlantic, with values of up to approximately 32%. In addition, the moisture source pattern exhibited a strong anomaly in the climatological pattern. However, the origin of the moisture sources associated with the case of 7 September 1989 was mainly the western Mediterranean Sea, with a contribution of up to 40% or higher. Finally, Northwest Africa and precipitation recycling processes over the IP contributed approximately 16% to the moisture supply for this event.
This study applies a Lagrangian approach to identify the origin of moisture for subtropical cyclones (SCs) along their tracks in the South Atlantic Ocean (SAO) basin from 1980 to 2015. The analysis ...shows that the local evaporation cannot fully explain the moisture gained by SCs, highlighting the role of external sources in moisture support, mainly through the northeasterly winds associated with the South Atlantic Subtropical Anticyclone. Overall, the northwestern SAO was the principal moisture source for SCs. It was noticeable that its contribution (~40%–45%) remained quasi‐constant during the year. Conversely, the moisture supplied from the northeastern SAO, southwestern SAO and the terrestrial source southeastern Brazil exhibited a marked seasonal variability. While contributions from the southwestern SAO intensify (weaken) in austral winter (summer), the southeastern Brazil source is more intense (weak) in summer (winter). In addition, SCs predominantly gain atmospheric humidity from sources close to their position, which reduces the mean water vapor residence time to ~3.2 days. Interestingly, we also found that ~42%–47% of the moisture that reached the SCs precipitates. These findings constitute a further step toward improving our knowledge of mechanisms underlying SC activity in the SAO basin.
The moisture transport by northeasterly winds is crucial for the activity of subtropical cyclones in the South Atlantic Ocean.The northwestern South Atlantic Ocean is the main moisture source for subtropical cyclogenesis maintaining a quasi‐constant contribution (~40%–45%) throughout the year.Approximately 42%–47% of the moisture gained by subtropical cyclones becomes precipitation.
Tropical cyclones (TCs) are extremely rare over the South Atlantic Ocean (SATL) due to predominantly unfavourable conditions, that is, cool sea‐surface temperature and strong vertical wind shear. ...Nevertheless, unusual conditions over SATL associated with a blocking system promoted the formation of Hurricane Catarina from an extratropical precursor in late March 2004, which produced heavy rainfall over the states of Santa Catarina and the Rio Grande do Sul in south Brazil. This work identifies the moisture sources for the precipitation produced by Catarina along its 6‐hourly trajectory, through a Lagrangian moisture‐tracking method. We extracted the pathways of precipitating air parcels within the cyclone's outer radius from the global outputs of the FLEXPART model forced with the ERA‐Interim reanalysis. Our findings revealed the terrestrial source in south‐southeastern Brazil (SEB) and the oceanic source limited by the box between 20‐40°S and 30–50°W over SATL (WSATL) as the principal moisture sources, with the overall support of ∼27% and ∼66%, respectively. However, their contribution varied according to the development phase of Catarina. While the moisture uptake from SEB decreased from ∼75% during the extratropical phase to ∼8% during the hybrid stage, the moisture contribution from WSATL notable increased from ∼20% to 87%, respectively. Likewise, the contributions from SEB and WSATL during the tropical phase of the cyclone accounted for ∼13% and ∼85%, respectively. The tracked air parcels achieved the high water content in a short period before the precipitation, leading to a reduction of the mean water vapour residence time to ∼3.1 days. Additionally, the precipitating moisture uptake along the Catarina trajectory was noticeably higher than the climatological value.
South‐southeastern Brazil and the western South Atlantic Ocean were the principal moisture sources for the precipitation of Catarina. The moisture contribution from each source varied accordingly to the different phase of Catarina development. The anomalous precipitating moisture uptake along the Catarina track exceeded noticeably the climatological value.
Abstract
Moisture transport and changes in the source–sink relationship play a vital role in the atmospheric branch of the hydrological cycle. Lagrangian approaches have emerged as the dominant tool ...to account for estimations of moisture sources and sinks; those that use the FLEXPART model fed by ERA-Interim reanalysis are most commonly used. With the release of the higher spatial resolution ERA5, it is crucial to compare the representation of moisture sources and sinks using the FLEXPART Lagrangian model with different resolutions in the input data, as well as its version for WRF-ARW input data, the FLEXPART-WRF. In this study, we compare this model for 2014 and moisture sources for the Iberian Peninsula and moisture sinks of North Atlantic and Mediterranean. For comparison criteria, we considered FLEXPARTv9.0 outputs forced by ERA-Interim reanalysis as “control” values. It is concluded that FLEXPARTv10.3 forced with ERA5 data at various horizontal resolutions (0.5° and 1°) represents moisture source and sink zones as represented forced by ERA-Interim (1°). In addition, the version fed with the dynamic downscaling WRF-ARW outputs (∼20 km), previously forced with ERA5, also represents these patterns accurately, allowing this tool to be used in future investigations at higher resolutions and for regional domains.
Significance Statement
The FLEXPART dispersion model forced with ERA5 reanalysis data at various resolutions represents moisture source and sink zones compared to when it is forced by ERA-Interim. When the Weather Research and Forecasting Model is used to dynamically downscale ERA5, FLEXPART-WRF can also represent moisture sources and sinks, allowing this tool to be used in future investigations requiring higher resolution and regional domains and on regions with a predominance of complex orography due to its ability to represent local moisture transport.
The main aim of the rain forecast is to determine rain occurrence conditions in a specific location. This is considered of vital importance to assess the availability of water resources in a basin. ...In this study, several methods are analyzed to forecast monthly rainfall totals in hydrological basins. The study region was the Almendares-Vento basin, Cuba. Based on Multi–Layer Perceptron (MLP), Convolutional Neural Network (CNN) and Long Short–Term Memory (LSTM) neural networks, and Autoregressive Integrated Moving Average (ARIMA) models, we developed a hybrid model (ANN + ARIMA) for rainfall prediction. The input data were the one year lagged rainfall records in gauge stations within the basin, sunspots, the sea surface temperature and time series of nine climate indices up to 2014. The predictions were also compared with the rainfall records of a gauge station network from 2015 to 2019 provided by the Cuban National Institute of Hydraulic Resources. Based on several statistical metrics such as mean absolute error, Pearson correlation, BIAS, Nash–Sutcliffe efficiency and Kling–Gupta efficiency, the CNN model showed higher ability to forecast monthly rainfall. Nevertheless, the hybrid model was notably better than individual models. Overall, our findings have proved the reliability of using the hybrid model to predict rainfall time series for water management and can be extensively applied to this sort of application. In addition, this work proposes a new approach to enhance the planning and management of water availability in watershed for agriculture, industry and population through improving rainfall forecasting.
Article Highlights
Convolutional Neural Network model is able to forecast monthly rainfall amounts.
Our methodology allows the models to learn the seasonal variations of the rainfall.
The hybrid model is skillful to forecast rainfall time series for water management.
The findings are promising to enhance water management systems.
The method can be easily applied to predict rainfall in other watersheds.
