Influence Of Volcanic Eruptions Research Articles

Changes in Northern Hemisphere extra-tropical cyclone frequency following volcanic eruptions

Explosive volcanic eruptions are well known to influence Earth’s temperature. Changes in Earth’s temperature can affect temperature gradients which in turn could affect the isentropic slope and hence Northern Hemisphere high and mid-latitude weather. Yet, the possible influence of volcanic eruptions on these atmospheric circulation patterns and the potential spatial extent are not well understood. To address this issue, we pursue two independent lines of evidence. Firstly, we simulate volcanic eruptions with the MPI-ESM1.2 Earth System Model and use the TRACK algorithm to explore how extra-tropical cyclone (ETC) frequency is affected in the model experiments. Secondly, we query the Greenland ice core NEEM-2011-S1 for indications of increased Northern Hemisphere ETC frequency correlating with evidence for explosive volcanism by comparing the storm proxies sodium and calcium; with the eruption proxy sulphur. Both the model and proxy evidence suggest that large explosive volcanic eruptions increase storminess around the location of the ice core. Furthermore, the simulations indicate that the number of ETCs increases in the subtropics and at high latitudes, while they decrease in the mid-latitudes. A detailed interrogation of the simulated eruptions reveals that increases in cyclone frequency are linked to steepening of the isentropic slope due to a larger meridional temperature gradient and to a lower tropopause. The steepening is driven by a combination of warming of the tropical stratosphere from absorption of longwave radiation by volcanic aerosols and surface cooling due to the scattering of sunlight by the same aerosols, whereas the lower tropopause may be attributed to a warmer stratosphere.

Lidar Observations of Stratospheric Aerosols in Obninsk in 2012–2021: Influence of Volcanic Eruptions and Biomass Burning

Lidar Observations of Stratospheric Aerosols in Obninsk in 2012–2021: Influence of Volcanic Eruptions and Biomass Burning

Differential pedogenesis of some pseudo-andic and non-andic soils in a toposequence of Andaman and Nicobar Islands

A large scale soil survey with high resolution image data and classification has been conducted to understand soil genesis of North and Middle Andaman district soils with emphasis of some pseudo-Andic and non-Andic nature in a topographical sequence for the first time. The study of soils showed sandy loam to silty clay loam texture, low in bulk density (0.96–1.22 Mg m−3) very strongly acidic (pH 4.6) to strongly alkaline (pH 9.0) with medium to high (7.4–9.8 g kg−1) organic carbon. Bulk density has a significant negative correlation with Feo (r = -0.74**), Feo/Fed (r = -0.77**) and Alo+0.5Feo (r = -0.73**), indicating the direct influence of amorphous Fe and Al on lowering bulk density of soils. Cation exchange capacity (CEC)/clay has also significant negative correlation with Feo (r = -0.53**), Feo/Fed (r = -0.60) and Alo+0.5Feo (r = -0.52**). Bulk density, acid oxalate extractable Fe (Feo) and Al (Alo), citrate-bicabonate-dithionate extractable Fe (Fed), percentage of Alo plus half the Feo and Feo/Fed ratio were proven to be the appropriate indicators of Pseudo-Andic properties in soils. Pseudo-Andic soils were classified as Aquandic Fluvaquents in interspersed valleys, Aquandic Endoaquepts in coastal plains and Aquandic Endoaqualfs in volcanic mudflats. Non-Andic soils were formed in uplands (Typic Hapluudalfs) and alluvial plains (Typic Endoaqualfs). The study inferred that effect of volcanic ejections was very much prominent in coastal plains, mangroves and swamps and has been spread up to the interspersed valleys. Soils on uplands and alluvial plains did not experience little or no influence of volcanic eruptions and found matured profiles. Soils on coastal region were environmentally most vulnerable and needs appropriate conservation measures. Vulnerability of coastal plain soils and typical pseudo-Andic soils observed require a special soil and land management to protect and maintain soil health and productivity. Criteria used to characterize the nature and vulnerability risk helps to manage similar kind of soils elsewhere for land use plan.

Responses of testate amoebae assemblages (Amoebozoa: Arcellinida) to recent volcanic eruptions, inferred from the sediment record in Laguna Verde, southern Patagonia, Argentina

There is little knowledge about testate amoebae in lakes and their responses to volcanic eruptions. To address this knowledge gap, we studied the paleoecology of these protists in a sediment record from Laguna Verde, a lake located east of the southern Patagonian Ice Field, in Santa Cruz Province, Argentina. The lake is under the influence of volcanic eruptions from Lautaro Volcano, Chile, ~ 42 km WNW of Laguna Verde. We evaluated the response of 11 testate amoeba morphospecies in the lake to the last four Lautaro eruptions, using a 61-cm sediment core. Calcium (Ca), a major element of volcanic ash, was the most important variable explaining testate amoeba variability in the three zones determined by detretended correspondence analysis. We identified four declines in testate amoeba abundance and diversity associated with tephra deposition. Poisson regression analysis revealed that Difflugia immanata, D. bidens, and D. glans strain “glans” decrease after deposition of tephra layers. In contrast, Centropyxis constricta strain “constricta,” C. aculeata strain “aculeata” and Zivkovicia compressa respond positively to ash deposition. Our findings suggest a high resilience of testate amoebae to stochastic events such as volcanism because the same assemblage (D. immanata, D. bidens, and D. glans strain “glans”) inhabited the lake before and after the ashfalls. Nevertheless, several volcanic eruptions during the last ~ 300 years may have weakened this resilience and had a long-term effect on community diversity. Multivariate analysis showed that potassium (K) plays a significant role in shaping assemblage composition. Because of the low K content of the Lautaro tephra, we infer that higher potassium concentrations in sediments are not related with volcanic events, but rather, are associated with terrestrial input. Future studies, however, will be needed to identify the source of K in the sediment record and its relationship with testate amoebae assemblages. Our study demonstrates the potential for using lacustrine testate amoebae as environmental proxies, and illustrates the direct effects of volcanic ash deposition on their assemblage composition, diversity and distribution in southern Patagonia.

Suspended sediment yield characteristics variability in rivers of Kamchatka krai

The regularities of spatiotemporal variability of suspended sediment yield characteristics were studied. Based on the analysis of difference-integral yield curves, it was found that most of the rivers in Kamchatka krai are characterized by the presence of two relatively long trends in the suspended sediment yield variability: an increase until the end of the 1970s–early 1980s, and its subsequent decrease. This regularity disturbs in rivers under the influence of volcanic eruptions, where the most significant increasing of sediment yield is observed after major eruptions. Existent maps of mean annual suspended sediment concentration and mean annual specific suspended sediment yield were significantly specified (18 instead 4 and 13 instead two zones were marked respectively). The map of grain-size distribution of suspended sediment was compiled (three zones was marked in region under study). Maximum values of mean annual specific suspended sediment yield (more than 500 t km-2 yr-1), suspended sediment concentration (more than 1000 g m-3) and grain-size of sediments are observed in water runoff of volcanic areas. Minimum values of suspended sediment concentration, specific suspended sediment yield, as well as grain-size of sediments characterized the mainland part of the krai.

The influence of volcanic eruptions on weather regimes over the North Atlantic simulated by ECHAM5/MPI-OM ensemble runs from 800 to 2000 CE

The volcanic fingerprint on the winter North Atlantic atmospheric circulation and climate is analyzed in six ensemble runs of ECHAM5/MPI-OM covering 800–2000 CE, both for equatorial and Northern Hemisphere (NH) eruptions. Large volcanic eruptions influence climate on both annual and decadal time scales due to dynamic interactions of different climate components in the Earth's system. It is well known that the North Atlantic Oscillation (NAO) tends to shift towards its positive phase during winter in the first 1–2 years after large tropical volcanic eruptions, causing warming over Europe, but other North Atlantic weather regimes have received less attention. Here we investigate the four dominant weather regimes in the North Atlantic: The negative and positive phase of NAO as well as the Atlantic Ridge, Scandinavian blocking. The volcanic fingerprint is detected as a change in the frequency of occurrence and anomalies in the wind and temperature fields as well as in the sea ice cover. We observe a strong significant increase in the frequency of Atlantic Ridge in the second year after equatorial eruptions that precede the NAO+ detected in year 3–5 as a result of a strong zonal wind anomalies in year 1–2. Evidence for a stronger polar vortex is detected in years 12–14 where NAO+ is detected both as a frequency increase and in the wind and temperature fields. A short-term response is also detected 2–4 years after NH eruptions. The longterm signal after NH eruptions indicate a weak polar vortex around a decade after an eruption. Although the signal after NH eruptions is weaker our results stress the need for further studies. The simulated atmospheric response recorded in ECHAM5 after volcanic eruptions suggest a more dynamic response than previously thought. The methodology used can also be applied to other forcing scenario, for example for future climate projections where the aim is to search for a long-term climate signal.

The transformation of the runoff of the suspended load in Kamchatkan rivers due to volcanism

This paper considers the influence of volcanic eruptions on the variation in the characteristics of the runoff of the suspended river load (suspended sediment concentration, discharge, rate of runoff, and grain-size distribution) on a variety of space–time scales (daily, seasonal, and long-term). The main factors that affect the yield of suspended load in rivers that flow in volcanic areas include the water runoff, drainage area, and the abundance of unconsolidated volcanic deposits. The areas of recent volcanism in Kamchatka are characterized by the maximum values of potential scour of particles, the mean long-term suspended sediment concentration, and specific suspended sediment yield. The largest increment in the transport of suspended river load in areas of volcanic activity is observed after major eruptions. The daily variations in the transport of suspended load are controlled by the water regime of rivers on the slopes of active volcanoes, namely, periodic cessations of surface runoff because of filtering into volcanic deposits.

Evaluation for Influence of New Volcanic Eruption on Geological Disposal Site

ABSTRACTThere are some regions where it is difficult to exclude the possibility of appearance of new volcanic activity on the site even if the geological disposal site is located far from existing volcanos in Japan. In order to identify the influence of volcanic eruption at the site to the public if it occurs, public exposure doses were evaluated based on the two scenarios considering types of eruption at new volcanic activity in Japan. One is the exposure by volcanic ash widespread by Strombolian eruption and deposited on the ground surface, including radionuclides from vitrified waste forms after a volcanic conduit penetrated the repository. The other is that by waste forms appeared at the ground surface by Merapi type pyroclastic flow. Exposure doses of the residents living on the volcanic ash do not exceed 1mSv/y even when the eruption occurs at 1,000 years after closure of disposal site. Exposure dose rate for the volcanic researchers temporarily approaching naked waste forms without realizing radioactive wastes is 0.8mSv/h when the eruption occurs 100,000 years after. It indicated that attention should be paid to the influence by Merapi type pyroclastic flow on researchers approaching waste forms appeared rather than that by Strombolian eruption on residents living on the volcanic ash widespread.

Arctic catchment as a sensitive indicator of the environmental changes: distribution and migration of metals (Svalbard)

Arctic regions experience metal pollution, despite their remote location, and the distribution and migration of those metals determine their potential impact on the local environment. Here, a High-Arctic catchment (Revelva, Svalbard) located remotely from human-induced pollution sources is studied with respect to the distribution and migration of chosen trace elements (Ag, Al, As, B, Ba, Bi, Ca, Cd, Co, Cr, Cu, Cs, Mo, Ni, Pb, Sb, Se, Sr, Tl, U, V and Zn) in surface waters. The metal concentrations fluctuated in 2010–2012 between 0.01 and 354 μg L−1, the highest mean-weighted concentration noted for Sr (42.5 μg L−1). The concentrations in the river water were likely influenced by both natural and human-activity-related processes. These factors can produce substances of the same chemical composition (e.g. carbon dioxide, sulphur dioxide and metals may be emitted both by a volcanic eruption and by industrial sources). Therefore, chemometric techniques were used in the current paper to distinguish the multiple sources of pollution in the Revelva catchment. The authors were seeking to determine whether there is indeed evidence for contamination, sufficient to cause environmental damage in polar region. As a result, it was shown that the long-range transport could play an important role in shaping the metal concentration profile of this Arctic tundra environment, capturing both the influence of volcanic eruptions within the region and the human activity in a range of distances from the study site.

The influence of volcanic eruptions on the climate of tropical South America during the last millennium in an isotope-enabled general circulation model

Abstract. Currently, little is known on how volcanic eruptions impact large-scale climate phenomena such as South American paleo-Intertropical Convergence Zone (ITCZ) position and summer monsoon behavior. In this paper, an analysis of observations and model simulations is employed to assess the influence of large volcanic eruptions on the climate of tropical South America. This problem is first considered for historically recent volcanic episodes for which more observations are available but where fewer events exist and the confounding effects of El Niño–Southern Oscillation (ENSO) lead to inconclusive interpretation of the impact of volcanic eruptions at the continental scale. Therefore, we also examine a greater number of reconstructed volcanic events for the period 850 CE to present that are incorporated into the NASA GISS ModelE2-R simulation of the last millennium. An advantage of this model is its ability to explicitly track water isotopologues throughout the hydrologic cycle and simulating the isotopic imprint following a large eruption. This effectively removes a degree of uncertainty associated with error-prone conversion of isotopic signals into climate variables, and allows for a direct comparison between GISS simulations and paleoclimate proxy records. Our analysis reveals that both precipitation and oxygen isotope variability respond with a distinct seasonal and spatial structure across tropical South America following an eruption. During austral winter, the heavy oxygen isotope in precipitation is enriched, likely due to reduced moisture convergence in the ITCZ domain and reduced rainfall over northern South America. During austral summer, however, more negative values of the precipitation isotopic composition are simulated over Amazonia, despite reductions in rainfall, suggesting that the isotopic response is not a simple function of the "amount effect". During the South American monsoon season, the amplitude of the temperature response to volcanic forcing is larger than the rather weak and spatially less coherent precipitation signal, complicating the isotopic response to changes in the hydrologic cycle.

Natural origin arsenic in aquatic organisms from a deep oligotrophic lake under the influence of volcanic eruptions.

Volcanic eruptions are recognized sources of toxic elements to freshwater, including arsenic (As). In order to study the short term changes in the bioaccumulation of naturally occurring As by aquatic organisms in Lake Nahuel Huapi (Argentina), located close to the Puyehue-Cordón Caulle volcanic complex (PCCVC), we described As concentrations at different trophic levels and food web transfer patterns in three sites of the lake prior to the last PCCVC eruption (June 2011), and compared As concentrations in biota before and after the eruption. The highest As concentrations and greater variations both between sites and position in the water column, were observed in phytoplankton (3.9-64.8 µg g(-1) dry weight, DW) and small zooplankton (4.3-22.3 µg g(-1) DW). The pattern of As accumulation in aquatic organisms (whole body or muscle) was: primary producers (phytoplankton) > scrapper mollusks (9.3-15.3 µg g(-1) DW) > filter feeding mollusks (5.4-15.6 µg g(-1) DW) > omnivorous invertebrates (0.4-9.2 µg g(-1) DW) > zooplankton (1.2-3.5 µg g(-1) DW) > fish (0.2-1.9 µg g(-1) DW). We observed As biodilution in the whole food web, and in salmonids food chains, feeding on fish prey; but biomagnification in the food chain of creole perch, feeding on benthic crayfish. The impact of the 2011 PCCVC eruption on the As levels of biota was more evident in pelagic-associated organisms (zooplankton and planktivorous fish), but only in the short term, suggesting a brief high bioavailability of As in water after ash deposition. In benthic organisms As variations likely responded to shift in diet due to coverage of the littoral zone with ashes.

Influence of volcanic eruptions on midlatitude upper tropospheric aerosol and consequences for cirrus clouds

AbstractThe influence of downwelling stratospheric sulfurous aerosol on the UT (upper troposphere) aerosol concentrations and on cirrus clouds is investigated using CARIBIC (Civil Aircraft for Regular Investigation of the Atmosphere Based on an Instrument Container observations) (between 1999–2002 and 2005–2013) and the cirrus reflectance product from Moderate Resolution Imaging Spectroradiometer (MODIS). The initial period, 1999–2002, was volcanically quiescent after which the sulfurous aerosol in the LMS (lowermost stratosphere) (SLMS) became enhanced by several volcanic eruptions starting 2005. From 2005 to 2008 and in 2013, volcanic aerosol from several tropical eruptions increased SLMS. Due to consequent subsidence, the sulfur loading of the upper troposphere (SUT) was increased by a factor of 2.5 compared to background levels. Comparison of SLMS and SUT during the seasons March–July and August–November shows a close coupling of the UT and LMS. Finally, the relationship between SLMS and the cirrus cloud reflectance (CR) retrieved from MODIS spectrometer (on board the satellites Terra and Aqua) is studied. SLMS and CR show a strong anticorrelation, with a factor of 3.5 increase in SLMS and decrease of CR by 8 ± 2% over the period 2001–2011. We propose that the increase of SLMS due to volcanism has caused the coinciding cirrus CR decrease, which would be associated with a negative radiative forcing in the Northern Hemisphere midlatitudes.

The influence of volcanic eruptions on growth of central European lowland trees in NE-Germany during the last millennium

Palaeoclimate proxies have shown links between climate changes and volcanic activity. However, not much is known about the impact of volcanic outbursts on growth of lowland trees. We investigate the effect of large volcanic eruptions on the growth rate of trees. The study is based on an unexplored comprehensive database with 1128 samples of long tree-ring width (TRW) chronologies of Quercus robur L. and Pinus sylvestris L., correlating with forest net primary production (NPP), originating from three different sites in eastern Germany (Greifswald, Eberswalde and Saxony). This study focuses on trees in rarely examined temperate zones where tree growth is less temperature limited. Growth relationships were compared against 52 large volcanic eruptions known for the last 1000years. Dendrochronological methods revealed a predominantly negative (60.2%) effect of large volcanic eruptions on the tree-ring chronologies. Nevertheless, also positive (31.7%) and neutral (8.7%) tree growth reactions were detected. In the tree-ring width chronologies of Q. robur and P. sylvestris, we detected a negative influence on tree growth for up to four years after large eruptions. The chronologies of Q. robur revealed a stronger negative response (68.1%) than those of P. sylvestris (53%). However, at the Greifswald site both tree species (79% Q. robur and 73% P. sylvestris) show a negative response in tree growth after every volcanic eruption. Furthermore, the results suggest that volcanic aerosols originating from the Northern Hemisphere cause a greater reduction in tree growth than aerosols being emitted from Southern Hemisphere volcanoes, which might be related to the long distances between trees and volcanoes, as well as the global atmospheric circulation patterns. This study demonstrates that the effects of major volcanic eruptions are less clear in trees from central European lowlands than in trees growing at the altitudinal or latitudinal timberlines.

Identifying volcanic signals in Irish temperature observations since AD 1800

Large volcanic eruptions have been shown to affect temperature patterns to varying degrees on continental, hemispheric or global scales. However, few studies have systematically explored the influence of volcanic eruptions on temperatures at a local, Irish level. The focus of this paper is to determine the impacts of five high-magnitude low-latitude volcanic eruptions and one such Icelandic event on Irish climate over the past ∼200 years. Daily temperature data from the Armagh Observatory, Co. Armagh, Northern Ireland was used to assess the influence of volcanic eruptions on seasonal and yearly values through time. The paper explores volcanically-induced temperature trends by filtering out the influence of the North Atlantic Oscillation (NAO) and solar variability, and goes on to employ a variation of Superposed Epoch Analysis to identify which seasons and years are most significantly affected by large volcanic eruptions. Armagh temperatures proved particularly responsive in the spring, with a significant...

Influence of volcanic eruptions on the climate of the Asian monsoon region

Several state‐of‐the‐art general circulation models (GCMs) predict that large volcanic eruptions should result in anomalous dry conditions throughout much of monsoon Asia. Here, we use long and well‐validated proxy reconstructions of Asian droughts and pluvials to detect the influence of volcanic radiative forcing on the hydroclimate of the region since the late Medieval period. Superposed epoch analysis reveals significantly wetter conditions over mainland southeast Asia in the year of an eruption, with drier conditions in central Asia. Our proxy and model comparison suggests that GCMs may not yet capture all of the important ocean‐atmosphere dynamics responsible for the influence of explosive volcanism on the climate of Asia.

Statistical modeling of total ozone: Selection of appropriate explanatory variables

A set of 44 potential explanatory variables is used for statistical modeling of monthly mean total ozone values of 158 ground‐based stations. A stepwise elimination process leads to zonally optimized multiple regression models, which account for approximately 78% of the variance in total ozone in the tropics, 85% south of 60°S and more than 90% in the three remaining zones while only retaining six explanatory variables in the model. In all regions the dynamics appear to dominate ozone variability, which is primarily described by a proxy specifically designed to describe the effects of short‐term isentropic excursions at different altitude levels and the compression/expansion of air connected to convergence/divergence. The influence of equivalent effective stratospheric chlorine (EESC) is also important in all regions, indicating the significant effects of anthropogenic emissions of ozone depleting substances (ODS). In addition to the dynamics and EESC, the influence of volcanic eruptions, represented by the integrated surface area density of stratospheric aerosols (SAD), has the largest impact on total ozone in northern regions. The results of the analysis are less clear in the Southern Hemisphere where only a few long‐enough ozone time series are available.

Exciting natural modes of variability by solar and volcanic forcing: idealized and realistic experiments

Using multi-millenium simulations performed with the three-dimensional climate model ECBILT-CLIO, we analyze how variations in the external forcing can excite low-frequency modes of climate variability. We find that prescribing an idealized, abrupt decrease in solar irradiance can trigger a large perturbation of the oceanic thermohaline circulation (THC) associated with a cooling of more than 5 degreesC in the North Atlantic over decades to centuries. Using more realistic scenarios that include the variations of solar irradiance and the influence of volcanic eruptions, such large perturbations of the THC are not triggered. Nevertheless, modifications of the forcing can strongly modify the probability of very cold years in the North Atlantic. During those cold years, sea-ice covers a large part of the Nordic Seas and the inflow of warm Atlantic waters at high latitudes is strongly reduced. Those processes induce a temporarily, strong local amplification of the forcing and generate modifications of the atmospheric conditions. Simulations of the last millenium climate using realistic forcing reveal that the probability to have such very cold years in the model is higher during the period AD 1300-1850 than during the first centuries of the second millenium or during the twentieth century. This might explain the higher variability observed during this period in some climate records in the Nordic Seas.

Influence of volcanic eruptions on Northern Hemisphere summer temperature over the past 600 years

A network of temperature-sensitive tree-ring-density chronologies provides circum-hemisphere information on year-by-year changes in summer warmth in different regions of the northern boreal forest1. Combining these data into a single time-series provides a good summer-temperature proxy for northern high latitudes and the Northern Hemisphere as a whole2. Here we use this well dated, high-resolution composite time-series to suggest that large explosive volcanic eruptions produced different extents of Northern Hemisphere cooling during the past 600 years. The large effect of some recent eruptions is apparent, such as in 1816, 1884 and 1912, but the relative effects of other known, and perhaps some previously unknown, pre-nineteenth-century eruptions are also evaluated. The most severe short-term Northern Hemisphere cooling event of the past 600 years occurred in 1601, suggesting that either the effect on climate of the eruption of Huaynaputina, Peru, in 1600 has previously been greatly underestimated, or another, as yet unidentified, eruption occurred at the same time. Other strong cooling events occurred in 1453, seemingly confirming a 1452 date for the eruption of Kuwae, southwest Pacific, and in 1641/42, 1666, 1695 and 1698.

Changes in stratospheric aerosols and solar insolation due to Mt. Pinatubo eruption as observed over the western Pacific

Effects of the Mt. Pinatubo eruption on the stratospheric aerosols and the solar insolation over the Western Pacific were estimated by sunphotometer and pyranometer on board ships. The sunphotometer measurements showed that the columnar aerosol optical thickness increased by 0.3 at 500 nm over the latitude from 30°N to 30°S, while that without the influence of volcanic eruptions is less than 0.1. The aerosol optical thickness became minimum in the summer of 1992, and increased again after the summer. The shipboard pyranometer measurements showed that solar insolation decreased after the eruption by 1.4∼4.1% compared with that before the eruption. This value is larger than that calculated with radiative transfer code, based on the aerosol model estimated from the sunphotometry.

Influence of volcanic eruptions on the troposphere through stratospheric dynamical processes in the northern hemisphere winter

It has been suggested that the zonal‐mean stratospheric zonal‐wind anomalies can propagate downward into the troposphere, producing considerable changes. On the other hand, volcanic aerosols are thought to produce a stronger polar vortex in the winter stratosphere. If these suggestions are correct, the influence of volcanic eruptions can be expected to produce changes in the northern hemisphere winter troposphere through stratospheric process. In the present study, this idea is examined by analyzing changes in the January circulation after three recent volcanic eruptions. Regional features of observed changes in tropospheric temperatures due to volcanic eruptions can be explained by the changes in the propagation of stationary waves associated with dipole‐type anomalies in the zonal‐mean zonal winds, which are similar to those observed in a previous work on the influence of polar night jet.