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Ozone (O3) pollution threatens global public health and damages ecosystem productivity. Droughts modulate surface O3 through meteorological processes and vegetation feedbacks. Unraveling these influences is difficult with traditional chemical transport models. Here, using an atmospheric chemistry-vegetation coupled model in combination with a suite of existing measurements, we investigate the drought impacts on global surface O3 and explore the main driving processes. Relative to the mean state, accelerated photochemical rates dominate the surface O3 enhancement during droughts except for eastern U.S. and western Europe, where reduced stomatal uptakes make comparable contributions. During 1990-2012, the simulated frequency of O3 pollution episodes in western Europe decreases greatly with a negative trend of -5.5 ± 6.6 days per decade following the reductions in anthropogenic emissions if meteorology is fixed. However, such decreased trend is weakened to -2.1 ± 3.8 days per decade, which is closer to the observed trend of -2.9 ± 1.1 days per decade when year-to-year meteorology is applied because increased droughts alone offset 43% of the effects from air pollution control. Our results highlight that more stringent controls of O3 precursors are necessary to mitigate the higher risks of O3 pollution episodes by more droughts in a warming world., This work was jointly supported by the National Natural Science Foundation of China (grant no. 41975155) and Jiangsu Science Fund for Distinguished Young Scholars (grant no. BK20200040). R.S. acknowledges grants RYC2020-029216-I and CEX2018-000794-S funded by MCIN/AEI/10.13039/501100011033 and by “ESF Investing in your future”. We would like to thank the editor and four anonymous reviewers for their constructive comments which helped improve the quality of the paper.

Исследованы непериодические повышения интенсивности микросейсмического шума. На протяжении четырех месяцев осуществлялись синхронные геофизические наблюдения гравиметрами ScintrexCG5 Autograv в Обнинске, Мурманске, Екатеринбурге и Красноярске. При проведении измерений были зарегистрированы множественные случаи синхронного повышения интенсивности микросейсмических шумов, как в пунктах гравиметрических наблюдений, так ив ряде сейсмометрических пунктов северовосточной части Евразии. Продолжительность зарегистрированного аномального повышения микровибраций составляет от нескольких часов до нескольких суток. Высокочувствительные гравиметры регистрируют не только гравитационное поле и его вариации, связанные с приливными изменения силы тяжести и другими неприливными и метеорологическими явлениями, но и высокочастотные вариации, связанные в первую очередь с воздействием процессов инерциального характера. Гравиметры и сейсмографы обладают различными характеристиками, однако, высокочастотное воздействие, от общего источника регистрируется обоими приборами, с той лишь разницей, что в гравиметре оно считается помехой и характеризуется среднеквадратичным отклонением (СКО). СКО гравиметрических данных, и СКО, посчитанное по рядам измерений сейсмометров, обнаруживают высокое сходство. Сопоставление с микросейсмическими шумами позволяет говорить об инерциальной, а не о гравиметрической природе зарегистрированных гравиметрами аномалий. Результаты исследования корреляционных связей сигналов объясняются крупными локальными вариациями микросейсм и метеорологических характеристик, их влиянием на тонкую структуру геофизических сигналов, регистрируемых гравиметрами. Кратковременные полугодовые наблюдения обнаружили особенности геофизических процессов на обширной территории Евразии. Дальнейшие исследования позволят выявить тонкую структуру взаимных влияний геофизических процессов по данным наблюдений чувствительными гравиметрами и сейсмометрами. Учет этого явления необходим при планировании и выполнении высокоточных гравиметрических съемок и долговременных гравиметрических наблюдений., Nonperiodic intensity increase of microseismic noise was researched. During four months, synchronous geophysical observations were carried out using Scintrex CG5 Autograv gravimeters in Obninsk, Murmansk, Yekaterinburg and Krasnoyarsk. During the measurements, multiple cases of synchronous intensity increase of microseismic noise were recorded, both at the gravimetric observation points and at a number of seismometric points in northeastern Eurasia. The duration of the registered anomalous increase in microvibrations ranges from several hours to several days. Highly sensitive gravimeters register not only the gravitational field and its variations associated with tidal changes of gravity and other nontidal and meteorological phenomena, but also highfrequency variations associated primarily with the effects of inertial processes. Gravimeters and seismographs have different characteristics, however, both instruments record highfrequency effects from a common source, with the only difference that in the gravimeter it is considered interference and is characterized by standard deviation (RMS). RMS of gravimetric data, and RMS, calculated by series of seismometers measurements, show high similarity. Comparison with microseismic noise suggests an inertial rather than a gravimetric nature of anomalies recorded by gravimeters. The results of the signals correlation study are explained by large local variations of microseisms and meteorological characteristics, their influence on the fine structure of geophysical signals recorded by gravimeters. Shortterm semiannual observations revealed features of geophysical processes in the vast territory of Eurasia. Further studies will reveal the fine structure of the mutual influences of geophysical processes according to observation data by sensitive gravimeters and seismometers. Consideration of this phenomenon is necessary when planning, performing highprecision gravimetric surveys, and longterm gravimetric observations, Геология и геофизика Юга России, Выпуск 2 2019

A fully nonlinear, primitive equation hydrostatic numerical model is utilized to study coastal how along central California. combining a realistic atmospheric model, with a higher-order turbulence closure, with highly simplified background flow. Local terrain and surface forcing of the model are treated realistically, while the synoptic-scale forcing is constant in time and space. Several different simulations with different background wind directions were performed. The motivation is to isolate the main properties of the local flow dependent on the coastal mesoscale influence only and to facilitate a study of the structure of the coastal atmospheric boundary layer, the mean momentum budget, and the atmospheric forcing on the coastal ocean for simplified quasi-stationary but still typical conditions. The model results feature the expected summertime flow phenomena, even with this simplified forcing. A coastal jet occurs in all simulations, and its diurnal variability is realistically simulated. The coastal topography serves as a barrier, and the low-level coastal flow is essentially coast parallel. Among the conclusions are the following. (i) The boundary layer for a northerly jet is more shallow and more variable than that for a southerly jet. One reason is an interaction between waves generated by the coastal mountains and the boundary layer. A realistic inclusion of the Sierra Nevada is important, even For the nearsurface coastal atmosphere. (ii) The transition from southerly to northerly flow, when changing the background flow direction, is abrupt for a change in the latter from west to northwest and more gradual for a change cast to south. (iii) The low-level flow is in general semigeostrophic. The across-coast momentum balance is geostrophic, while the along-coast momentum balance is dominated by vertical stress divergence and the pressure gradient. Local acceleration and spatial variability close to the coast arise as a consequence of the balance among the remaining terms. For southeasterly background flow, the across-coast momentum balance is dominated by the background synoptic-scale and the mesoscale pressure gradients, sometimes canceling the forcing, thus making this case transitional. (iv) Smaller-scale flow transitions arise for some background flow directions, including an early morning jet reversal north of Monterey, California, and a morning-to-noon low-level eddy formation in the Southern Californian Eight. (v) The model turbulence parameterization provides realistic patterns of the atmospheric forcing on the coastal ocean. (vi) Characteristic signals measured in propagating wind reversals related to boundary layer depth and inversion structure here are seen to correspond to different quasi-stationary conditions.

The influence of the main large-scale wind directions on thermally driven mesoscale circulations at the Baltic southwest coast, southeast of Sweden, is examined. The aim of the study is to highlight small-scale alterations in the coastal atmospheric boundary layer. A numerical three-dimensional mesoscale model is used in this study, which is focused on an overall behaviour of the coastal jets, drainage flows, sea breezes, and a low-level eddy-type flow in particular. It is shown that synoptic conditions, together with the moderate terrain of the southeast of Sweden (max. height h(0) less than or equal to 206 m), governs the coastal mesoscale dynamics triggered by the land-sea temperature difference Delta T. The subtle nature of coastal low-level jets and sea breezes is revealed ; their patterns are dictated by the interplay between synoptic airflow, coastline orientation, and Delta T. The simulations show that coastal jets typically occur during nighttime and vary in height, intensity and position with respect to the coast ; they interact with downslope flows and the background wind. For the assigned land surface temperature (varying +/-8 K from the sea temperature) and the opposing constant geostrophic wind 8 m s(-1), the drainage flow is more robust to the opposing ambient flow than the sea breeze later on. Depending on the part of the coast under consideration, and the prevailing ambient wind, the sea breeze can be suppressed or enhanced, stationary at the coast or rapidly penetrating inland, locked up in phase with another dynamic system or almost independently self-evolving. A low-level eddy structure is analyzed. It is governed by 'tilting', 'divergence' and horizontal advection terms. The horizontal extent of the coastal effects agrees roughly with the Rossby radius of deformation.

International audience; This study aims at better understanding the space-time statistical properties of rain over a Mediterranean region. To this end we analyzed temporal, spatial, and spatio-temporal spectra of rain field maps provided by an X-band radar situated in the southeast part of France. The database extends from 2009 to 2012 and has a spatial and temporal resolution of 1 km2 and 5 min. The analysis highlights several scaling regimes, which are interpreted in terms of meteorological structures (convective cells, mesoscale structures, and midlatitude cyclones). The analysis of spectra per month confirms the dependency of the spectral signature to the underlying meteorological process. Nevertheless, our results also reveal that for a given range of scales (20-45 min in time and 7-20 km in space), spectral slope is monthly invariant. It means that rain behaves identically, in terms of scaling, whatever the mechanism that generated it (convection, front). Moreover, spectral analysis shows that the temporal decorrelation scale is 10 days, which can possibly be related to the longest lifetime of a meteorological phenomenon in the region (i.e., about 10 days). An approach to compute the scaling anisotropy between space and time is proposed. It reveals that, over two distinct ranges of scales (7-20 km/20-45 min and 20-70 km/45 min-3 h), the scaling anisotropic coefficient is equal to 2. It also reveals that the ratio of spectral slope of 2-D angle averaged spatial spectrum versus 1-D temporal spectrum is equal to 1 over these ranges of scales. It suggests a similarity in the second-order properties (e.g., correlation) of temporal and spatial rain field. All these results are important to better understand rainfall statistical behavior and could also be used for the development of downscaling schemes and the validation of numerical weather models.

Comunicación presentada en: Symposium on Atmospheric Chemistry and Physics at Mountain Sites celebrado del 8 al 10 de junio de 2010 en Interlaken, Suiza.

Comunicación presentada en: Symposium on Atmospheric Chemistry and Physics at Mountain Sites celebrado del 8 al 10 de junio de 2010 en Interlaken, Suiza.