Explore the vast range of titles available.

Atmospheric Rivers (ARs) are elongated, narrow corridors of concentrated moisture in the atmosphere, transporting significant amounts of water vapor outside the tropics and causing heavy precipitation. ARs are often accompanied with explosive extratropical cyclones (EECs) over oceans. This paper investigates the characteristics of 118 super ARs associated with EECs over the Northern Pacific Ocean. Nearly 78.0% of ARs are associated with strong or super EECs, indicating that stronger ARs may lead to more explosive development of EECs. The composite analyses of ARs suggest that the AR is typically located in southwest of the cyclone center, in front of the cold front, with mean value of AR top pressure of approximately 693.51 hPa. In addition, water vapor from low latitudes and that evaporating from the sea surface are two important water vapor sources for ARs. Through investigating the evolution of EECs, a mechanism strengthens ARs and EECs.

The climatological characteristics of water vapor transport over the Tibetan Plateau (TP) were investigated in this study by using the ERA-interim and JRA55 monthly reanalysis dataset. The trends of water vapor budget and water vapor sources during the past 40 years were also revealed. The analyses show that the TP is a water vapor convergence area, where the convergence was enhanced from 1979 to 2018. In addition, the convergence is much stronger in JJA, with a linear trend that is twice the annual average trend. The climatological water vapor sources over the TP were identified mainly at the southern and western boundaries, with the vapor sources at the southern boundaries originating from the Arabian Sea and Bay of Bengal and the vapor sources at the western boundary being transported by mid-latitude westerlies. The TP is a moisture sink at a climatological mean, with an annual average net water vapor flux of 11.86 × 106kg ∙ s−1. Water vapor transport is much stronger in JJA than in other times of the year, and the net water vapor flux is 29.60 × 106kg ∙ s−1. The net water vapor flux in the TP increased with a linear trend of 0.12×106kg ∙ s−1 ∙ year−1 (α = 0.01), while the increase in the flux was more significant in JJA than in other times of the year with a linear trend of 0.30 ×106kg ∙ s−1 ∙ year−1 (α = 0.01). Detailed features in the water vapor flux and transport changes across the TP’s four boundaries were explored by simulating backward trajectories with a Lagrangian trajectory model (hybrid single-particle Lagrangian integrated trajectory model, HYSPLIT). In the study period, the water vapor contribution rate of western channel is increased. However, the Southern channel’s water vapor contribution decreased.

Qiang, A.; Wang, N.; Xie, J., and Wei, J., 2020. Analysis of water vapor change and precipitation conversion efficiency based on HYSPLIT backward trajectory model over the three-river headwaters region. In: Hu, C. and Cai, M. (eds.), Geo-informatics and Oceanography. Journal of Coastal Research, Special Issue No. 105, pp. 6–11. Coconut Creek (Florida), ISSN 0749-0208. The paper traced the moisture transport path for –240 h of the Three-River Headwaters Region (TRHR) and calculated atmospheric water vapor content and Precipitation Conversion Efficiency (PCE) by introducing Hybrid Single Particle Lagrangian Integrated Trajectory backward trajectory model based on Lagrangian integral propagation diffusion model using the Global Data Assimilation System assimilation data provided by National Centers for Environmental Prediction and the ERA-Interim data of the European Centre for Medium-Range Weather Forecasts, they were compared and analyzed PCE with precipitation contribution rate. The results were as follows: first, the PWV and P had been increasing trend from 1979 to 2017 in the TRHR, but the seasonal difference was obvious. They gradually decreased in space from southeast to northwest. Second, a height of 1000 m becomes the water vapor source boundary layer in TRHR, the southern flow (45.5%), and the northern flow (54.5%) appear below 1000 m; however, the western water vapor (75%) and eastern water vapor (25%) above 1000 m. Third, the water vapor mainly come from the west-oriented airflow brought by the westerly belt in the TRHR, but the backward trajectory variation is different at different altitudes and moments. Fourth, The precipitation contribution rate isn't consistent with the results reflected by PCE in the TRHR.

From a global perspective, the stable isotope altitude effect is crucial for understanding climate information. However, the intensity of this effect can be influenced by the source of moisture, particularly in inland mountainous regions where the moisture sources are complex. Different combinations of moisture sources might affect the altitude effect. Focusing on the upper Shiyang River in the northern part of the Qilian Mountains in China, this study calculated the proportion of recycled moisture in precipitation and utilized the HYSPLIT model to determine the source of advective moisture. It explored the characteristics and mechanisms by which moisture sources affect the spatiotemporal variations in precipitation isotope effects within the study area. The findings indicated that: (a) The altitude effect follows a seasonal pattern: winter < autumn < spring < summer, with a reverse effect in winter. (b) As the contribution of recycled moisture to precipitation increases, the altitude effect of stable isotopes weakens, primarily due to the disruptive influence of recycled moisture on this effect. (c) The altitude effect of stable isotopes in precipitation is determined by the direction of the moisture source and its attributes. When the primary source of advective moisture runs perpendicular to the mountain range and the moisture migration speed is slow, the altitude effect is pronounced. Thus, although temperature directly causes the altitude effect, water vapor sources significantly influence it in inland mountainous regions. Key Points The altitude effect has significant seasonal variation, being strong in summer and weakest in winter The contribution of recirculating water vapor to precipitation is large, weakening the altitude effect The source of water vapor and the nature of the air masses contribute to the differences in elevation effects

Using the four-times daily and monthly-mean reanalysis datasets of NCEP/NCAR for the 1958 to 2018 period, we investigate the interannual variability of the June-July-August (JJA)–mean water vapor source and sink over the tropical eastern Indian Ocean-Western Pacific (TEIOWP) and the underlying mechanism. It is found that the two major modes (EOF1 and EOF2) of the water vapor source and sink anomalies over the TEIOWP present a southwest-northeast oriented dipole and a southwest-northeast oriented tripole. Specifically, when the western maritime continent shows an anomalous water vapor source, the northwestern Pacific is characterized by anomalous water vapor sink and source in EOF1 and EOF2 modes, respectively. The EOF1 and EOF2 modes are primarily driven by a single and a double meridional cell anomaly, which corresponds to the in-phase and out-of-phase linkage between evaporation anomalies over the western maritime continent and precipitation anomalies over the northwestern Pacific, respectively. Furthermore, the EOF1 mode is regulated by the quick transition of the El Niño-Southern Oscillation (ENSO) phase, whereas the EOF2 mode probably originates from internal atmospheric variability. Considering that the standard deviation of PC1 is much higher during ENSO years than that during non-ENSO years, it is probable that the water source and sink anomalies over the TEIOWP tend to be dominant by EOF1 mode during ENSO years. In contrast, the EOF2 mode may play an important role in the water source and sink anomalies over the TEIOWP during non-ENSO years. Accordingly, the water vapor source and sink anomalies over the TEIOWP may be well predicted based on the ENSO state in the previous December-January-February. These results are useful for understanding the predictability of water vapor source and sink anomalies over the TEIOWP.

We characterized new particle formation (NPF) events in the urban background of Amman during August 2016–July 2017. The monthly mean of submicron particle number concentration was 1.2 × 104–3.7 × 104 cm−3 (exhibited seasonal, weekly, and diurnal variation). Nucleation mode (10–15 nm) concentration was 0.7 × 103–1.1 × 103 cm−3 during daytime with a sharp peak (1.1 × 103–1.8 × 103 cm−3) around noon. We identified 110 NPF events (≈34% of all days) of which 55 showed a decreasing mode diameter after growth. The NPF event occurrence was higher in summer than in winter, and events were accompanied with air mass back trajectories crossing over the Eastern Mediterranean. The mean nucleation rate (J10) was 1.9 ± 1.1 cm−3 s−1 (monthly mean 1.6–2.7 cm−3 s−1) and the mean growth rate was 6.8 ± 3.1 nm/h (4.1–8.8 nm/h). The formation rate did not have a seasonal pattern, but the growth rate had a seasonal variation (maximum around August and minimum in winter). The mean condensable vapor source rate was 4.1 ± 2.2 × 105 molecules/cm3 s (2.6–6.9 × 105 molecules/cm3 s) with a seasonal pattern (maximum around August). The mean condensation sink was 8.9 ± 3.3 × 10−3 s−1 (6.4–14.8 × 10−3 s−1) with a seasonal pattern (minimum around June and maximum in winter).

To better understand the process of precipitation and water cycle, the composition of stable isotope in precipitation and its influences by different vapor sources in the eastern of Qilian Mountains were conducted from June 2013 to May 2014. The total of 100 precipitation samples were collected in Wushaoling national meteorological station located in the eastern of Qilian Mountains. The analysis indicates that the slope of Local Meteoric Water Line is lower than that of Global Meteoric Water Line. The average values of δ 18 O and δD in precipitation are higher in summer but lower in winter. Except for negative correlation with relative humidity, the stable isotope values in precipitation are positive correlations with temperature, precipitation and water vapor pressure. Influenced by water vapor source, the values of d -excess are lower for the Westerly wind and the South Asia Monsoon on July and the Westerly wind and the East Asia Monsoon on August, but they are higher for the Westerly wind on other months, that they are also influenced by the weather conditions in rainfall process. The variation of stable isotope in precipitation exhibited significant temperature effect, and there is also some precipitation amount effect in spring and summer.

AWAKE is a plasma wakefield acceleration R&D experiment at CERN, where wakefields are driven by relativistic and self-modulated proton bunches. The goal of AWAKE Run 2b is to demonstrate that a correctly placed plasma density step stabilises the wakefield amplitude (after saturation of self-modulation) at a higher value than without the step. This can be demonstrated by accelerating witness particles. It is therefore planned to externally side-inject 19MeV test electrons into the wakefields. In this manuscript, the injection setup for the AWAKE Run 2b experiments is summarised. Challenges on beam transport due to the Earth’s magnetic field upstream of the vapour source entrance are highlighted and uncertainties on the injection location are estimated. Additionally, a new plasma-light-based diagnostic to verify that electrons cross the plasma column is introduced.

The AWAKE experiment investigates the acceleration of externally injected electrons into the wakefields driven by a self-modulated proton bunch. In Run 1, AWAKE successfully demonstrated proton bunch self-modulation and accelerated electrons from 19 MeV to 2 GeV. For Run 2b, upgrades to the rubidium vapour source enabled the introduction of a plasma density step and adjustments to the plasma length. This facilitated studies on how the density step sustains the longitudinal wakefield amplitude by measuring the electron energy gain as a function of the plasma length. This paper presents the analysis techniques for such energy measurements and the technical considerations for interpreting results under the varying plasma conditions.

The Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) platform is used to simulate Lagrangian trajectories of air parcels in East China during the summer monsoon. The investigation includes four distinct stages of the East Asian summer monsoon (EASM) during its seasonal migration from south to north. Correspondingly, the main water vapor channel migrates from the west Pacific Ocean (PO) for the premonsoon in South China (SC) to the Indian Ocean (IO) for the monsoon in SC and in the Yangtze–Huaihe River basin, and finally back to the PO for the terminal stage of monsoon in North China. Further calculations permit us to determine water vapor source regions and water vapor contribution to precipitation in East China. To a large extent, moisture leading to precipitation does not come from the strongest water vapor pathways. For example, the proportions of trajectories from the IO are larger than 25% all of the time, but moisture contributions to actual precipitation are smaller than 10%. This can be explained by the large amount of water vapor lost in the pathways across moisture-losing areas such as the Indian and Indochina Peninsulas. Local water vapor recycling inside East China (EC) contributes significantly to regional precipitation, with contributions mostly over 30%, although the trajectory proportions from subregions in EC are all under 10%. This contribution rate can even exceed 55% for the terminal stage of the monsoon in North China. Such a result provides important guidance to understand the role of land surface conditions in modulating rainfall in North China.