Atmospheric Regimes Research Articles

Geodynamics of Super‐Earth GJ 486b

AbstractMany super‐Earths are on very short orbits around their host star and, therefore, more likely to be tidally locked. Because this locking can lead to a strong contrast between the dayside and nightside surface temperatures, these super‐Earths could exhibit mantle convection patterns and tectonics that could differ significantly from those observed in the present‐day solar system. The presence of an atmosphere, however, would allow transport of heat from the dayside toward the nightside and thereby reduce the surface temperature contrast between the two hemispheres. On rocky planets, atmospheric and geodynamic regimes are closely linked, which directly connects the question of atmospheric thickness to the potential interior dynamics of the planet. Here, we study the interior dynamics of super‐Earth GJ 486b ( , , K), which is one of the most suitable M‐dwarf super‐Earth candidates for retaining an atmosphere produced by degassing from the mantle and magma ocean. We investigate how the geodynamic regime of GJ 486b is influenced by different surface temperature contrasts by varying possible atmospheric circulation regimes. We also investigate how the strength of the lithosphere affects the convection pattern. We find that hemispheric tectonics, the surface expression of degree‐1 convection with downwellings forming on one hemisphere and upwelling material rising on the opposite hemisphere, is a consequence of the strong lithosphere rather than surface temperature contrast. Anchored hemispheric tectonics, where downwellings und upwellings have a preferred (day/night) hemisphere, is favored for strong temperature contrasts between the dayside and nightside and higher surface temperatures.

Storms and convection on Uranus and Neptune: Impact of methane abundance revealed by a 3D cloud-resolving model

Context. Uranus and Neptune have atmospheres dominated by molecular hydrogen and helium. In the upper troposphere (between 0.1 and 10 bar), methane is the third main molecule, and it condenses, yielding a vertical gradient in CH4 . As this condensable species is heavier than H2 and He, the resulting change in mean molecular weight due to condensation serves as a factor countering convection, which is traditionally considered as governed by temperature only. This change in mean molecular weight makes both dry and moist convection more difficult to start. As observations also show latitudinal variations in methane abundance, one can expect different vertical gradients from one latitude to another. Aims. In this paper, we investigate the impact of this vertical gradient of methane and the different shapes it can take, including on the atmospheric regimes and especially on the formation and inhibition of moist convective storms in the troposphere of ice giants. Methods. We developed a 3D cloud-resolving model to simulate convective processes at the required scale. This model is nonhydrostatic and includes the effect of the mean molecular weight variations associated with condensation. Results. Using our simulations, we conclude that typical velocities of dry convection in the deep atmosphere are rather low (on the order of 1 m/s) but sufficient to sustain upward methane transport and that moist convection at the methane condensation level is strongly inhibited. Previous studies derived an analytical criterion on the methane vapor amount above which moist convection should be inhibited in saturated environments. In ice giants, this criterion yields a critical methane abundance of 1.2% at 80 K (this corresponds approximately to the 1 bar level). We first validated this analytical criterion numerically. We then showed that this critical methane abundance governs the inhibition and formation of moist convective storms, and we conclude that the intensity and intermittency of these storms should depend on the methane abundance and saturation. In the regions where CH4 exceeds this critical abundance in the deep atmosphere (at the equator and the middle latitudes on Uranus and at all latitudes on Neptune), a stable layer almost entirely saturated with methane develops at the condensation level. In this layer, moist convection is inhibited, ensuring stability. Only weak moist convective events can occur above this layer, where methane abundance becomes lower than the critical value. The inhibition of moist convection prevents strong drying and maintains high relative humidity, which favors the frequency of these events. In the regions where CH4 remains below this critical abundance in the deep atmosphere (possibly at the poles on Uranus), there is no such layer. More powerful storms can form, but they are also a bit rarer. Conclusions. In ice giants, dry convection is weak, and moist convection is strongly inhibited. However, when enough methane is transported upward, through dry convection and turbulent diffusion, sporadic moist convective storms can form. These storms should be more frequent on Neptune than on Uranus because of Neptune’s internal heat flow and larger methane abundance. Our results can explain the observed sporadicity of clouds in ice giants and help guide future observations that can test the conclusions of this work.

Studies of dynamic spatio-temporal processes of electrons in a 50 kHz/5 MHz dual-frequency dielectric barrier discharge plasma at atmospheric pressure

Dual-frequency excitation of dielectric barrier discharge (DBD) plasma reactors, where the plasma is generated by a low-frequency (LF) source and modulated by a radio-frequency (RF) source, have been widely adopted in the low-pressure regime. However, the impacts of the RF voltage and LF voltage amplitudes on the plasma parameters, including the spatiotemporal distributions of ion and electron densities, electron dynamics, and gas temperatures, remain poorly understood in the atmospheric pressure regime. The present work addresses this issue by conducting joint experimental and simulation studies for an atmospheric-pressure 50 kHz/5 MHz dual-frequency driven DBD plasma reactor based on phase-resolved optical emission spectra and a drift–diffusion model. The results demonstrate that the dynamic spatiotemporal behaviors of electrons change dramatically as the voltage of the RF component increases from 50 V to 300 V with the voltage of the LF component fixed at 1 kV. Moreover, the RF component is further demonstrated to modulate other plasma characteristics, such as particle densities, gas temperature, and argon emissions. These results contribute toward the tailoring of the non-equilibrium and nonlinear plasma parameters obtained under atmospheric pressure conditions.

Novel Atmospheric Dynamics Shape the Inner Edge of the Habitable Zone around White Dwarfs

White dwarfs offer a unique opportunity to search nearby stellar systems for signs of life, but the habitable zone around these stars is still poorly understood. Since white dwarfs are compact stars with low luminosity, any planets in their habitable zone should be tidally locked, like planets around M dwarfs. Unlike planets around M dwarfs, however, habitable white dwarf planets have to rotate very rapidly, with orbital periods ranging from hours to several days. Here we use the ExoCAM global climate model to investigate the inner edge of the habitable zone around white dwarfs. Our simulations show habitable planets with ultrashort orbital periods (P ≲ 1 day) enter a “bat rotation” regime, which differs from typical atmospheric circulation regimes around M dwarfs. Bat rotators feature mean equatorial subrotation and a displacement of the surface’s hottest regions from the equator toward the midlatitudes. We qualitatively explain the onset of bat rotation using shallow water theory. The resulting circulation shifts increase the dayside cloud cover and decrease the stratospheric water vapor, expanding the white dwarf habitable zone by ∼50% compared to estimates based on 1D models. The James Webb Space Telescope should be able to quickly characterize bat rotators around nearby white dwarfs thanks to their distinct thermal phase curves. Our work underlines that tidally locked planets on ultrashort orbits may exhibit unique atmospheric dynamics, and guides future habitability studies of white dwarf systems.

1-Hexene Ozonolysis across Atmospheric and Combustion Temperatures via Synchrotron-Based Photoelectron Spectroscopy and Chemical Ionization Mass Spectrometry.

This study investigates the complex interaction between ozone and the autoxidation of 1-hexene over a wide temperature range (300-800 K), overlapping atmospheric and combustion regimes. It is found that atmospheric molecular mechanisms initiate the oxidation of 1-hexene from room temperature up to combustion temperatures, leading to the formation of highly oxygenated organic molecules. As temperature rises, the highly oxygenated organic molecules contribute to radical-branching decomposition pathways inducing a high reactivity in the low-temperature combustion region, i.e., from 550 K. Above 650 K, the thermal decomposition of ozone into oxygen atoms becomes the dominant process, and a remarkable enhancement of the conversion is observed due to their diradical nature, counteracting the significant negative temperature coefficient behavior usually observed for 1-hexene. In order to better characterize the formation of heavy oxygenated organic molecules at the lowest temperatures, two analytical performance methods have been combined for the first time: synchrotron-based mass-selected photoelectron spectroscopy and orbitrap chemical ionization mass spectrometry. At the lowest studied temperatures (below 400 K), this analytical work has demonstrated the formation of the ketohydroperoxides usually found during the LTC oxidation of 1-hexene, as well as of molecules containing up to nine O atoms.

Late Glacial-Holocene cirque glacier chronology on sub-Antarctic Kerguelen Archipelago (49°S) based on cosmogenic 36Cl exposure dating

Sub-Antarctic glacier chronologies can provide valuable information about the past variability of climate dynamics in the Southern Ocean region. The Kerguelen Archipelago (49°S) is advantageously located under the influence of the Southern Hemisphere's westerly wind belt, thus fluctuations of climate-sensitive glaciers on Kerguelen can provide a baseline for understanding the behavior of this atmospheric regime in response to climatic forcings. We present 17 36Cl exposure ages of moraine and erratic boulders to provide chronological constraints to paleoglacier extents of the Guynemer cirque glacier, located just north of the Cook Ice Cap. Erratic boulders show ice thinning in the Guynemer region started to occur in the Late Glacial by 13.5 ka and continued past 12.4 ka. Ice retreat was punctuated by the formation of two moraine stages, the outermost at 11.5 ± 0.4 ka followed by another at 10.4 ± 1.2 ka, which are indicative of Early Holocene glacier advances/standstills. A glacial advance occurred at 1.4 ± 0.3 ka, which corroborates other Late Holocene re-advances elsewhere on the archipelago. Finally, three undated moraine stages are found between 1.4 ka and the 1960s. The lack of moraines after 10.4 ka and through the Mid-Holocene suggests that the Guynemer glacier was significantly smaller during this extended period of the Holocene compared to its Early Holocene as well as its Late Holocene limits. The Guynemer glacier history provides unique evidence of Early Holocene moraines on Kerguelen, which have not been discovered thus far on the archipelago. Similar to glaciers in Patagonia, New Zealand and South Georgia, the Guynemer glacier was at its largest Holocene extent in the Early Holocene. However, while other southern mid-latitude glacier chronologies show progressively smaller glacial extents throughout the Mid- to Late Holocene, the Late Holocene re-advance of the Guynemer glacier, like other Kerguelen glaciers, likely exceeded its Mid-Holocene extent.

Climate extremes in Svalbard over the last two millennia are linked to atmospheric blocking

Arctic precipitation in the form of rain is forecast to become more prevalent in a warmer world but with seasonal and interannual changes modulated by natural modes of variability. Experiencing rapid hydroclimatic changes in the Arctic, Svalbard serves as an ideal study location due to its exposure to oceanic and atmospheric variability in the North Atlantic region. Here we use climate data from paleoproxies, observations, and a climate model to demonstrate that wet and warm extremes in Svalbard over the last two millennia are linked to the presence of atmospheric blocking regimes over Scandinavia and the Ural mountain region. Rainfall episodes lead to the deposition of coarse sediment particles and high levels of calcium in Linnévatnet, a lake in southwest Svalbard, with the coarsest sediments consistently deposited during atmospheric blocking events. A unique annually resolved sediment record from Linnévatnet confirms that this linkage has been persistent over the past 2000 years. Our record also shows that a millennial-scale decline in Svalbard precipitation ended around the middle of the 19th century, followed by several unprecedented extreme events in recent years. As warming continues and sea ice recedes, future Svalbard floods will become more intense during episodes of Scandinavian and Ural blocking.

Characterizing turbulence structures in convective and neutral atmospheric boundary layers via Koopman mode decomposition and unsupervised clustering

The atmospheric boundary layer (ABL) is a highly turbulent geophysical flow, which has chaotic and often too complex dynamics to unravel from limited data. Characterizing coherent turbulence structures in complex ABL flows under various atmospheric regimes is not systematically well established yet. This study aims to bridge this gap using large eddy simulations (LESs), Koopman theory, and unsupervised classification techniques. To this end, eight LESs of different convective, neutral, and unsteady ABLs are conducted. As the ratio of buoyancy to shear production increases, the turbulence structures change from roll vortices to convective cells. The quadrant analysis indicated that as this ratio increases, the sweep and ejection events decrease, and inward/outward interactions increase. The Koopman mode decomposition (KMD) is then used to characterize their turbulence structures. Our results showed that KMD can reveal non-trivial modes of highly turbulent ABL flows (e.g., transverse to the mean flow direction) and can reconstruct the primary dynamics of ABLs even under unsteady conditions with only ∼5% of the modes. We attributed the detected modes to the imposed pressure gradient (shear), Coriolis (inertial oscillations), and buoyancy (convection) forces by conducting novel timescale and quadrant analyses. We then applied the convolutional neural network combined with the K-means clustering to group the Koopman modes. This approach is displacement and rotation invariant, which allows efficiently reducing the number of modes that describe the overall ABL dynamics. Our results provide new insights into the dynamics of ABLs and present a systematic data-driven method to characterize their complex spatiotemporal patterns.

Nonstationary thermodynamic and dynamic contributions to the interannual variability of winter sea ice growth in the Kara–Laptev Seas

The Kara–Laptev Seas (KLS), known as the ‘Ice Factory of the Arctic’, witnesses rising instead of falling winter sea ice growth (WSIG) under the shrinkage of Arctic ice. However, knowledge of the large year-to-year variation is still unclear. Combining a seasonal ice concentration budget, a composite analysis, and a typical case study, we study both the interannual variability of WSIG in the KLS and the associated air-sea forcings during 1985–2021. Results quantitatively reveal that, during 1985–2021, thermodynamic melt in the melting season (April–August) contributed 80.3% to the interannual ice loss difference and promoted the subsequent WSIG by the recovery mechanism in the KLS. This consistent thermodynamic melt is caused by the strengthened summer Beaufort High, transporting heat and introducing a locally positive ice-albedo feedback. However, since 2010, the dynamic growth during the freezing season (October–February) has increasingly stimulated the WSIG. Typical cases in 2013 and 2017 indicate that the overlying anticyclonic atmospheric regime restricts the ice drift from the KLS and contributes to the dynamic growth of 41.6% of the WSIG difference, while the turbulent-heat-induced thermodynamic growth in winter is down to 58.4%. In short, we reveal an unstable relationship between the summer ice loss and the subsequent WSIG under the background of Arctic warming. Our study points out that the distinct dynamic ice growth driven by surface winds or ocean currents during the freezing season is likely to increase in the near future, with thinner and more mobile seasonal ice predominating in the Arctic.

Wind farm power curve characterization under different atmospheric stability regimes

Wind farm power curves are particularly relevant in different applications. A better understanding of wind farm power curves under different atmospheric regimes is sought. In the present work, the atmospheric stability regime was identified by the vertical gradient of the potential temperature. Vertical profile of the wind velocity presented a clearly different pattern during the stable and unstable regimes. Analysis was performed considering 5 years of data from three wind farms, each corresponding to different mesoscale wind. Power curves are presented as a function of atmospheric stability. For each wind farm, we utilized wind velocity and temperature data measurements of a correspondent near the tower location. Clearly different patterns of wind farm power curves were observed as a function of the stability regime, with clear differences in the dependence of mesoscale wind regimes. For the same mean velocity, wind power production is greater for higher values of turbulence intensity TI.

Boost to early spring compound heatwaves over South Asia from anomalous Tibetan Plateau atmospheric heat source

In the early spring of 2022, South Asia (SA) experienced an unprecedented and prolonged episode of compound extreme heatwaves (EHWs), which pose significant risks to both human society and ecosystems. This exceptional event broke historical records for both frequency and intensity anomalies since 1981 and could be attributed to a barotropic atmospheric regime characterized by an anomalous anticyclone. This study ascribed this record-breaking event to an exceptionally warm Tibetan Plateau (TP) atmospheric apparent heat source (TPAHS). Both the observations and the numerical experiments conducted with a linear baroclinic model revealed that the unusual TPAHS acted as an “air pump”, driving the vigorous lower-level convergence and ascending motion around the TP. Abnormal TPAHS led to an increase in air temperature, subsequently elevating the height of the tropopause. This, in turn, induced a cooler upper-level and warmer lower-level thermal structure over the TP, resulting in a negative potential vorticity (PV) source near 200 hPa. As the TPAHS continued to intensify, the anomalous anticyclone strengthened and extended westward, facilitating the advection of negative PV anomalies from the TP to upstream regions. This resulted in negative PV anomalies and increased geopotential height over the SA. Furthermore, the triggered zonal circulation significantly enhanced descending motion and reduced relative vorticity, thereby strengthening the barotropic atmospheric regime over the SA. Consequently, clear skies prevailed, amplifying the solar shortwave radiation reaching the ground. This increase in surface thermal radiation warmed the near-surface air temperatures, ultimately resulting in compound EHWs on an interannual timescale.

Synergistic Effect of Surface Thermal Heterogeneity in Phase With Topography on Deep Moist Convection

AbstractUsing large eddy simulation, we investigate the combined effect of terrain and surface sensible heat flux (SHF) heterogeneity on the development of afternoon deep moist convection (DMC). We implement an analytically derived, two‐dimensional terrain and SHF variations transformed from a κ−3 (where κ is the wavenumber) spectrum spanning wavelengths from 32 to 0.2 km. By separately coupling multiscale terrain with a homogeneous SHF field and the multiscale SHF field with flat terrain, we discern the individual impacts of these κ−3‐spectrum forcings on DMC. Our specific forcing configuration demonstrates that the multiscale terrain had a greater influence on DMC development compared to the multiscale SHF field. While the solely surface SHF heterogeneity forcing results in a wider pool of high relative humidity above the boundary layer, its significance is relatively lower in the mountainous terrain cases due to the shorter interaction time between highly buoyant thermals and the surrounding environment. However, when the multiscale terrain and SHF field are synchronized, DMC develops rapidly within a time frame of 4.5 hr, which is facilitated by enhanced surface buoyancy fluxes, the presence of highly buoyant thermals, and the persistence of mesoscale structures such as near‐surface convergence and mesoscale updrafts. Our study highlights the importance of the synergistic effects between multiscale terrain and surface SHF heterogeneity in DMC development. Additionally, our multiscale analyses of atmospheric variables reveal distinct atmospheric regimes between the pre‐storm and DMC periods. These findings contribute to a better understanding of the complex dynamics involved in the formation of afternoon DMC.

Atmospheric chemistry regimes in intercontinental air traffic corridors: Ozone versus NOx sensitivity

This study focusses on the environmental consequences of aircraft NOx emissions and their role and impact on ozone formation in the upper troposphere and lower stratosphere (UTLS). We use a global chemistry transport/box model approach to quantify the impacts of NOx on UTLS ozone over time scales of hours and over distance scales appropriate to air traffic corridors and aircraft flight paths. An important feature of our study has been to provide a marked contrast to the coarse spatial resolution of the global model studies typically employed to assess the impacts of aviation NOx on UTLS ozone. Real operational aviation routing data are used to quantify the NOx impacts on ozone at 235 locations on 21 flight paths. The NOx impact on ozone in the intercontinental air traffic corridors is strongest in the great circle routes from North America and Europe into Asia and weakest in the trans-polar routes. The NOx impacts identified with the CTM/box model combination are significantly smaller compared with those identified in the current global models typically used to assess aviation NOx impacts. Further research is required to confirm our assessment of those flight paths that appear to show greatest NOx – O3 impacts and those the least and extend our analyses into the tropics and southern hemisphere.

Weather whiplash events in Europe and North Atlantic assessed as continental-scale atmospheric regime shifts

The term “weather whiplash” describes abrupt transitions from one persistent weather regime to another substantially different one, such as from a frigid cold spell to anomalous warmth. Weather whiplash events (WWEs) are often highly disruptive to agriculture, ecosystems, infrastructure, and human activities. While no consistent definition exists, we identify WWEs based on substantial shifts in the continental-scale, upper-atmosphere circulation. As first demonstrated in our earlier study focused on the NE Pacific/North American region, a WWE is detected when one persistent, large-scale pattern in 500 hPa height anomalies shifts to another distinctly different one. Patterns are identified using self-organizing maps (SOMs), which create a matrix of representative patterns in the data. In the present study, we apply this approach to identify WWEs in the North Atlantic/European sector. We analyze the occurrence of WWEs originating with long-duration events (four or more days) in each pattern. A WWE is detected when the pattern two days following a long-duration event is substantially different, measured with distance thresholds internal to the matrix. Changes in WWE frequency, past and future, are assessed objectively based on reanalysis output and climate model simulations. We find that future changes under RCP 8.5 forcing exhibit distinct trends, especially in summer months, while those based on reanalysis are less clear. Patterns featuring positive height anomalies in high latitudes are projected to produce more WWEs in the future, while patterns exhibiting negative anomalies produce fewer. Shifts in temperature and precipitation extremes associated with these WWEs are diagnosed.

Atmospheres as a window to rocky exoplanet surfaces

ABSTRACT As the characterization of exoplanet atmospheres proceeds, providing insights into atmospheric chemistry and composition, a key question is how much deeper into the planet we might be able to see from its atmospheric properties alone. For small planets with modest atmospheres and equilibrium temperatures, the first layer below the atmosphere will be their rocky surface. For such warm rocky planets, broadly Venus-like planets, the high temperatures and moderate pressures at the base of their atmospheres may enable thermochemical equilibrium between rock and gas. This links the composition of the surface to that of the observable atmosphere. Using an equilibrium chemistry code, we find a boundary in surface pressure–temperature space which simultaneously separates distinct mineralogical regimes and atmospheric regimes, potentially enabling inference of surface mineralogy from spectroscopic observations of the atmosphere. Weak constraints on the surface pressure and temperature also emerge. This regime boundary corresponds to conditions under which SO2 is oxidized and absorbed by calcium-bearing minerals in the crust, thus the two regimes reflect the sulphidation of the crust. The existence of these atmospheric regimes for Venus-like planets is robust to plausible changes in the elemental composition. Our results pave the way to the prospect of characterizing exoplanetary surfaces as new data for short period rocky planet atmospheres emerge.

A Bayesian Approach to Atmospheric Circulation Regime Assignment

Abstract The standard approach when studying atmospheric circulation regimes and their dynamics is to use a hard regime assignment, where each atmospheric state is assigned to the regime it is closest to in distance. However, this may not always be the most appropriate approach as the regime assignment may be affected by small deviations in the distance to the regimes due to noise. To mitigate this we develop a sequential probabilistic regime assignment using Bayes’s theorem, which can be applied to previously defined regimes and implemented in real time as new data become available. Bayes’s theorem tells us that the probability of being in a regime given the data can be determined by combining climatological likelihood with prior information. The regime probabilities at time t can be used to inform the prior probabilities at time t + 1, which are then used to sequentially update the regime probabilities. We apply this approach to both reanalysis data and a seasonal hindcast ensemble incorporating knowledge of the transition probabilities between regimes. Furthermore, making use of the signal present within the ensemble to better inform the prior probabilities allows for identifying more pronounced interannual variability. The signal within the interannual variability of wintertime North Atlantic circulation regimes is assessed using both a categorical and regression approach, with the strongest signals found during very strong El Niño years. Significance Statement Atmospheric circulation regimes are recurrent and persistent patterns that characterize the atmospheric circulation on time scales of 1–3 weeks. They are relevant for predictability on these time scales as mediators of weather. In this study we propose a novel approach to assigning atmospheric states to six predefined wintertime circulation regimes over the North Atlantic and Europe, which can be applied in real time. This approach introduces a probabilistic, instead of deterministic, regime assignment and uses prior knowledge on the regime dynamics. It allows us to better identify the regime persistence and indicates when a state does not clearly belong to one regime. Making use of an ensemble of model simulations, we can identify more pronounced interannual variability by using the full ensemble to inform prior knowledge on the regimes.

Aerosol Effects on Water Cloud Properties in Different Atmospheric Regimes

AbstractAerosol‐cloud interaction remains one of the least understood processes in climate science arena, despite its profound impacts in radiation and water budget perturbations. The aerosol effects on clouds largely depend on aerosol characteristics. Here, we implemented 17‐year (2003–2020) data set of aerosol, cloud, and meteorological factors collected over East Asia—a highly polluted region with recent decreasing trend of air pollution due to control measures—to elucidate atmospheric regime‐dependent aerosol effects on water cloud properties by simultaneously accessing the response of air pollution control measures in cloud field. The study found a very close relationship between aerosol loading and cloud properties modifications in the continental region of East Asia with a significant response of air pollution control measures in the cloud field. The study further revealed that aerosols of the polluted continental atmosphere affected cloud micro‐ and macro‐physics differently than aerosols of the clean maritime atmosphere: in the former, increased aerosol loading increased the stability under cloud base and then enhanced cloud droplet collision‐coalescence process, resulting to increase cloud droplet size by decreasing cloud top height; whereas in the latter, increased aerosol loading decreased cloud droplet size without notable influence in the atmosphere thermodynamics and cloud top height. This study further showed a complex aerosol‐cloud interaction process in the polluted maritime atmosphere due to the mixed effect of polluted continental and clean maritime atmospheres. In all atmospheric regimes, cloud fraction was found to increase with the increase of aerosol loading.

Water rather than nitrogen availability predominantly modulates soil microbial beta-diversity and co-occurrence networks in a secondary forest

Atmospheric nitrogen (N) deposition and changing precipitation regimes greatly affect the structure and functions of terrestrial ecosystems. However, their impacts on the diversity and assembly of soil microbial communities including bacteria, fungi and protists, remain largely unclear. As part of a six-year field experiment in a secondary forest in a warm temperate and subtropical climate transitional zone in China, we aimed to investigate the responses of soil microbial communities to N addition, increased and decreased precipitation. The results showed that N addition had no effect on soil microbial α- or β-diversity, but reduced the complexity of microbial network. Neither increased nor decreased precipitation influenced soil microbial α-diversity, but decreased precipitation rather than increased precipitation elevated bacterial and protistan community dissimilarities (β-diversity), which could have been largely attributed to species replacement processes through reducing soil water availability. In addition, decreased precipitation weakened microbial complexity and stability, but enhanced the node proportion of protists in the co-occurrence network. Our observations suggest the asymmetric responses of soil microbial β-diversity to increased and decreased precipitation, and underscore that water rather than N availability, especially drought condition, plays a predominant role in modulating soil microbial β-diversity. Moreover, the findings imply that global change can strengthen the importance of soil protists and then reshape microbial assembly in forests.

ANALYSIS OF THE SERIES OF ANNUAL TOTALS OF ATMOSPHERIC PRECIPITATION AT WEATHER STATIONS OF THE KALININGRAD REGION WITH REGARD TO THE ADJUSTMENT OF RAIN GAUGE READINGS

For solving hydrological problems, quantitative indicators of the atmospheric precipitation regime are of great importance. The article presents the results of the analysis of annual precipitation totals in the territory of the Kaliningrad region according to the observational data of meteorological stations. There are gaps in the results of atmospheric precipitation measurements, therefore, within the framework of this study, the observation series for the meteorological stations Baltiysk, Zheleznodorozhny, Sovetsk were reconstructed. The values of the sums of annual precipitation were corrected, taking into account the errors that arise during their measurement. Based on the data obtained (for the period from 1991 to 2020), a scheme of isolines of average annual amounts of atmospheric precipitation in the Kaliningrad region was constructed. The data obtained can be used in performing hydrological calculations and climate studies.

Changes in the Atmospheric Circulation Regime in the Context of Global Climate Trends in the Atlantic-Eurasian Sector of the Northern Hemisphere

Changes in the Atmospheric Circulation Regime in the Context of Global Climate Trends in the Atlantic-Eurasian Sector of the Northern Hemisphere