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 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

Completeness of radiosonde humidity observations based on the Integrated Global Radiosonde Archive

Radiosonde measurements from the 1930s to present give unique information on the distribution and variability of water vapor in the troposphere. The sounding data from the Integrated Global Radiosonde Archive (IGRA) Version 2 are examined here until the end of 2016, aiming to describe the completeness of humidity observations (simultaneous measurements of pressure, temperature, and humidity) in different times and locations. Upon finding the stations with a non-negligible number of radiosonde observations in their period of record, thus removing pilot-balloon stations from IGRA, the selected set (designated IGRA-RS) comprises 1723 stations, including 1300 WMO stations, of which 178 belong to the current GCOS Upper-Air Network (GUAN) and 16 to the GCOS Reference Upper-Air Network (GRUAN). Completeness of humidity observations for a radiosonde station and a full year is herein defined by five basic parameters: number of humidity soundings, fraction of days with humidity data, average vertical resolution, average atmospheric pressure and altitude at the highest measuring level, and maximum number of consecutive days without data. The observations eligible for calculating precipitable water vapor – i.e., having adequate vertical sampling between the surface and 500 hPa – are particularly studied. The present study presents the global coverage of humidity data and an overall picture of the temporal and vertical completeness parameters over time. This overview indicates that the number of radiosonde stations potentially useful for climate studies involving humidity depends not only on their record length, but also on the continuity, regularity, and vertical sampling of the humidity time series. Additionally, a dataset based on IGRA is described with the purpose of helping climate and environmental scientists to select radiosonde data according to various completeness criteria – even if differences in instrumentation and observing practices require extra attention. This dataset consists of two main subsets: (1) statistical metadata for each IGRA-RS station and year within the period of record; and (2) metadata for individual observations from each station. These are complemented by (3) a list of the stations represented in the whole dataset, along with the observing periods for humidity (relative humidity or dew-point depression) and the corresponding counts of observations. The dataset is to be updated on a 2-year basis, starting in 2019, and is available at https://doi.org/10.5281/zenodo.1332686.Ministerio de ciencia e Innovación | Ref. CGL2015-65141-RXunta de Galicia | Ref. ED431C 2017/64-GR

Synoptic and dynamical characteristics of high-impact storms affecting the Iberian Peninsula during the 2018–2021 extended winters

In the extended winters from December 2017 to April 2021, numerous high-impact storms affected the Iberian Peninsula (IP) with heavy precipitation and/or strong winds. Here, we provide a comprehensive assessment of these events, synoptic conditions, large-scale dynamics associated with storms, and a climatological analysis to improve public awareness and natural disaster prevention. Variability analysis presents that their maximum intensity ranges from 955 hPa to 985 hPa, a two-to-four-day lifetime, and the highest frequency (eight events) occurred in January. At the instant of maximum intensity, anomalies presented low MSLP values (−21.6 hPa), high values of water vapor (327.6 kg m−1s−1) and wind speed at 250 hPa (29.6 m s−1), high values of θe at 850 hPa (19.1 °C), SST (−1 °C), and QE (−150 W m−2), near Iberia. The values obtained during the storm impact days exceeded the 98th percentile values in a high percentage of days for daily accumulated precipitation (34%), instantaneous wind gusts (46%), wind speed at 10 m (47%), and concurrent events of wind/instantaneous wind gusts and precipitation (26% and 29%, respectively). These results allow us to characterize their meteorological impacts on the IP, namely those caused by heavy precipitation and wind.Fundação para a Ciência e a Tecnologia | Ref. UID/GEO/50019/2019Fundação para a Ciência e a Tecnologia | Ref. PTDC/CTAMET/29233/2017Fundação para a Ciência e a Tecnologia | Ref. LISBOA-01-0145-FEDER-029233Fundação para a Ciência e a Tecnologia | Ref. NORTE-01-0145-FEDER-029233Fundação para a Ciência e a Tecnologia | Ref. 2021.04927.BDXunta de Galicia | Ref. ED431C 2021/4

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-

Atmospheric moisture sources associated with extreme precipitation during the peak precipitation month

Understanding moisture transport is crucial for understanding continental precipitation and extreme precipitation events, which are expected to become substantially more frequent under global warming conditions. In this work, the influence of major global moisture sources on extreme continental precipitation during the peak precipitation month is estimated and compared with climatological patterns. The results show a general change in the pattern of contribution of the primary source of precipitation (the source with the highest contribution) during extreme precipitation events. Most primary sources show a general reduction in their area of influence and a notable reduction in their contribution to the total precipitation.Agencia Estatal de Investigación | Ref. RTI2018‐095772‐B‐I0OXunta de Galicia | Ref. ED481B 2018/062Xunta de Galicia | Ref. ED431C 2017/64Fundação para a Ciência e a Tecnologi

Influence of teleconnection patterns on global moisture transport during peak precipitation month

Teleconnection patterns are an important feature influencing the variability of moisture transport. This study explores the influence of the Arctic, Antarctic, Pacific-North American, and El Niño–Southern Oscillations on moisture transport from major oceanic and continental moisture sources during the peak precipitation month. The positive phase of the Pacific-North American teleconnection pattern increases the influence of Pacific Ocean moisture on western North America, while the negative phase increases the influence of Atlantic Ocean moisture over eastern North America, with differences between phases higher than 1.5 mm·day−1 over most of the area when the sources are the preferred. The positive phase of the Arctic Oscillation increases the importance of the Mediterranean as a source of moisture for western Europe while the negative phase increases the importance of the North Atlantic as a source with contribution increased in more than 2 mm·day−1 over Europe. The positive phase of the Antarctic Oscillation favours the contribution from the western Indian basin over eastern Africa, while in the negative phase the contribution from the southern Pacific is increased over northwestern Africa. For El Niño–Southern Oscillation, the main influence occurs over South America during El Niño events, increasing the moisture contributions from the South Pacific Ocean over southern South America and from South Atlantic over southeastern Brazil. El Niño events also increase the moisture transport from the North Atlantic over western Europe and from the North Pacific over North America. In contrast, La Niña events increase moisture contributions from the Pacific over Central America and northern South America, being the latter the area when higher differences between phases are observed.Xunta de Galicia | Ref. ED431C 2021/44Xunta de Galicia | Ref. ED481B 2018/062Xunta de Galicia | Ref. ED481D‐2022‐020Agencia Estatal de Investigación | Ref. RTI2018-095772-B-I00Fundação para a Ciência e a TecnologiaFinanciado para publicación en acceso aberto: Universidade de Vigo/CISU

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-

TROVA: TRansport Of water VApor

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGThe TRansport Of water VApor (TROVA) software, developed in Python and Fortran for the study of moisture sources and sinks, is presented here. TROVA includes the main Lagrangian methodologies established in the literature, using outputs from the global FLEXible PARTicle dispersion model and the regional FLEXPART-WRF model at different spatial resolutions. TROVA will benefit users investigating the physics of the atmosphere and fields associated with this branch in the study of current and future changes in source–sink moisture relationships and their link with mean and extreme precipitation.Xunta de Galicia | Ref. ED481A-2020/193Xunta de Galicia | Ref. ED431C 2021/44Agencia Estatal de Investigación | Ref. PID2021-122314OB-I0

LATTIN: A Python-based tool for Lagrangian atmospheric moisture and heat tracking

LATTIN is a Python-based tool for Lagrangian atmospheric moisture and heat tracking. It can read input data from the Lagrangian FLEXPART and FLEXPART-WRF models. Features include parallel reading of atmospheric parcel trajectories and user custom threshold criteria. It complements and improves existing tools by including several tracking approaches and also by its non-dependence on the horizontal resolution of the input or output grid. LATTIN provides a compact tool for Lagrangian atmospheric moisture and heat tracking, which will support a wide range of research to understand future changes in the hydrological cycle and extreme temperature eventsAgencia Estatal de Investigación | Ref. PID2021- 122314OB-I00Xunta de Galicia | Ref. ED481B-2023/016Xunta de Galicia | Ref. ED431C2021/44Universidade de Vigo/CISU