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Hydroxyl (OH) is the atmosphere’s main oxidant removing most pollutants including methane. Its short lifetime prevents large-scale direct observational quantification. Abundances inferred using anthropogenic trace gas measurements and models yield conflicting trend estimates. By contrast, radiocarbon monoxide ( 14 CO), produced naturally by cosmic rays and almost exclusively removed by OH, is a tracer with a well-understood source. Here we show that Southern-Hemisphere 14 CO measurements indicate increasing OH. New Zealand 14 CO data exhibit an annual-mean decrease of 12 ± 2% since 1997, whereas Antarctic measurements show a December-January decrease of 43 ± 24%. Both imply similar OH increases, corroborating our own and other model results suggesting that OH has been globally increasing during recent decades. Model sensitivity simulations illustrate the roles of methane, nitrogen oxides, stratospheric ozone depletion, and global warming driving these trends. They have substantial implications for the budgets of pollutants removed by OH, and especially imply larger than documented methane emission increases. Many atmospheric pollutants including methane are removed by the hydroxyl radical. Southern-Hemisphere long-term measurements of radiocarbon monoxide and global model results indicate that this atmospheric self-cleansing capacity is strengthening.

We use ground-based spectroscopic remote sensing measurements of the stratospheric trace gases O 3 , HCl, ClO, BrO, HNO 3 , NO 2 , OClO, ClONO 2 , N 2 O and HF, along with radiosonde profiles of temperature to track the springtime development of the 2019 ozone hole over Arrival Heights (77.8°S, 166.7°E, AHTS), Antarctica, during, and after, the 2019 stratospheric sudden warming (SSW) event. Both measurements and model simulations show that the 2019 SSW caused an extraordinarily warm stratosphere within the polar vortex, resulting in record low ozone depletion over AHTS. We also contrast the evolution of the 2019 ozone hole to that in 2002, which also had a major springtime SSW event. The SSW event started around 28 th August. By ∼17 th September, stratospheric temperatures inside the polar vortex over AHTS were ∼45 K higher than the climatological average. The SSW did not cause an en masse displacement of mid-latitude air over AHTS as in the 2002 SSW event. However, the increased temperatures did cause an unusually early reduction in polar stratospheric clouds, halting the denitrification early and leading to increased gas-phase HNO 3 and record high levels of NO 2 ('renoxification'). This caused the earliest observed deactivation of chlorine, returning all active chlorine into the chlorine reservoir species, HCl and ClONO 2 . The deactivation rate into HCl remained relatively unaffected by the SSW, whilst there was a dramatic increase in ClONO 2 formation. This chlorine deactivation pathway via ClONO 2 is typical of the Arctic and atypical for the Antarctic. At AHTS, record high levels of springtime ozone were observed. The measured ozone total column did not drop below 220 DU. Record high stratospheric temperatures persisted until 7 th October over AHTS. By 22 nd October, AHTS was not beneath the polar vortex. The polar vortex break-up date on 9 th November was one of the earliest observed.

The impact of cyclone track features (e.g., cyclone translation speed, cyclone path and cyclone landfall crossing angle) in combination with tidal phase shift upon surge characteristics have been investigated at the Bay of Bengal along the Bangladesh coast. A two-dimensional hydrodynamic model in a horizontal direction (2DH) coupled with a storm-surge model has been employed for the study. Numerical experiments with three different cyclone translation speeds show that when the surge height is directly forced by the cyclonic wind speed especially within the RWM (Radius of Maximum Wind), faster translation speed produces reduced surge height as the cyclone gets less time to force the water. On the other hand, at locations outside the RMW, surge waves travel as a propagating long wave where higher surges are produced by faster moving cyclones. It is found that surge arrival times are more and more affected by tidal phase when cyclone translation speed is reduced. Analysis of seven hypothetical parallel cyclone paths show that local bathymetry and complex coastline configurations strongly influence the surge height and surge arrival time along the Bangladesh coast. From the analyses of cyclone landfall crossing angles at the Khulna and Chittagong coasts, it is observed that surge durations are the smallest at both the coasts when the coastline crossing angles are the smallest.

Two hundred sixty-eight years (about three centuries) since the 1755 Lisbon tsunami, which provoked large-scale damage in Portugal, Spain and Morocco. Scientists in several countries have mobilized to develop investigative methods to study this extraordinary tsunami, with the aim of reducing the impact of waves in future events and protecting and warning populations at risk. However, the most important question remains whether the entire damaged community has sufficient information about the impact to prepare for tsunami risks. The aim of this paper is to determine the maximum wave heights in selected cities located within high-risk tsunami zones in Morocco, as well as the tsunami arrival time for each site. We used the Non-linear Shallow Water model With Nested Grids (NSWING) code to model tsunami propagation. Six cities were determined as observation points as being the subject of tsunami studies in previous work, namely Tangier, Asilah, Rabat, Casablanca, El-Jadida and Safi. The maximum wave height calculated within the Atlantic coast of Morocco exceeds 5 m in some locations and the first waves reach the Moroccan coast in 60 minutes. The authorities might utilize these results to develop evacuation plans.

Operational TEWS play a key role in reducing tsunami impact on populated coastal areas around the world in the event of an earthquake-generated tsunami. Traditionally, these systems in the NEAM region have relied on the implementation of decision matrices. The very short arrival times of the tsunami waves from generation to impact in this region have made it not possible to use real-time on-the-fly simulations to produce more accurate alert levels. In these cases, when time restriction is so demanding, an alternative to the use of decision matrices is the use of datasets of precomputed tsunami scenarios. In this paper we propose the use of neural networks to predict the tsunami maximum height and arrival time in the context of TEWS. Different neural networks were trained to solve these problems. Additionally, ensemble techniques were used to obtain better results.

Three-dimensional (3D) multi-input-multi-output (MIMO) is one of the enabling technologies for next-generation mobile communication. As the elevation angle in the 3D MIMO channel model might vary against the height of the base station (BS) antenna, it should be considered within channel modeling. In this paper, the impact of antenna height on the channel characteristics of the 3D MIMO channel is investigated by using the intelligent ray launching algorithm (IRLA). Three typical street scenarios, i.e., the straight street, the forked road, and the crossroad, are selected as benchmarks. The joint and marginal probability density functions (PDFs) of both the elevation angle of departure (EAoD) and the elevation angle of arrival (EAoA) are obtained through simulations. Moreover, the elevation angle spread (AS) and the elevation delay spread (DS) under various antenna heights are jointly discussed. Simulation results show that the characteristics of the PDFs of EAoD will vary under different street scenarios. It is observed that in order to obtain the maximum or minimum value of the AS and the DS, the BS antenna should be deployed at half of the building height.

The combination of a high-frequency ocean surface radar and a tsunami detection method should be assessed as the onshore-offshore distribution of tsunami detection probability, because the probability will vary in accordance with the signal-to-noise ratio (SNR) and the tsunami magnitude in addition to the radar system specifications. Here, we statistically examine the tsunami detection distance based on virtual tsunami observation experiments by using signals received by a high-frequency radar in February 2014 installed on the southern coast of Japan and numerically simulated velocities induced by a Nankai Trough earthquake. In the experiments, the Doppler frequencies associated with the simulated velocities were superimposed on the receiving signals of the radar, and the radial velocities were calculated from the synthesized signals by the fast Fourier transform. Tsunami arrival was then detected based on the temporal change in the cross-correlation of the velocities, before and after tsunami arrival, between two points 3 km apart along a radar beam. We found that the possibility of tsunami detection primarily depends on the kinetic energy ratio between tsunami current and background current velocities. The monthly average detection probability is over 90% when the energy ratio exceeds 5 (offshore distance: 9 km ≤  L  ≤ 36 km) and reduces to 50% when the energy ratio is approximately 1 ( L  = 42 km) over the shelf slope. The ratio varied with the background current physics and SNR, which was mainly affected by ocean surface wave heights and ionospheric electron density.

The Makran subduction zone (MSZ), located along the southern coasts of Iran and Pakistan, has experienced some deadly earthquakes and tsunamis, including the destructive 1945 Makran tsunami that led to more than 4000 fatalities. In spite of past studies on 1945 Makran tsunami, there are still unresolved problems, particularly on mismatches between the tsunami wave heights and arrival times with reported observations at different locations. The significant disagreement between the results of numerical models and existing data supports the existence of another mechanism involved during the generation of the tsunami. In the present study, a submarine landslide, triggered by the 1945 Earthquake, is studied as the major source of 1945 Makran tsunami. The simulation of seismic 1945 Tsunami, using high-resolution bathymetry data with a fine nested grid to increase the accuracy of modeled tsunami wave heights, confirms the large discrepancies between the reported tsunami waves and simulated values. Assuming the location and dimensions of a probable landslide, the GEOWAVE model, a combination of TOPICS and FUNWAVE models, is applied to model the non-seismic 1945 Tsunami. The simulated landslide tsunami demonstrates a fair agreement with the reported tsunami wave heights at different locations in Pakistan, Iran and India. The arrival times of tsunami waves at Pasni and Karachi in Pakistan can also be interpreted if the occurrence time of the probable submarine landslide is assumed with 3.5 h delay after the quake. The study highlights the potential danger of a non-seismic landslide tsunami in unconsolidated sediments at the MSZ and the necessity of the development of suitable countermeasures against other potential Makran tsunamis in future.

Seaquake is a phenomenon where there are water disturbance at the sea, caused by earthquake or submarine eruption. The scope of this study focuses on tsunami simulation due to Manila Trench and Sulu Trench seaquake which is prone to harm Malaysia offshore areas. Manila Trench is a highly potential earthquake source that can generate tsunami in South China Sea. Meanwhile, Sulu Trench could be a threat to east of Sabah offshore areas. In this study, TUNA-M2 model was utilized to perform tsunami simulation at South China Sea and Sulu Sea. TUNA-M2 model applied Okada source model to create tsunami generation due to earthquake. It utilized linear shallow water equation during tsunami propagation with its radiant boundary condition. Five simulations performed at each study region. Forecast points at South China Sea areas were divided into three separate locations which are at the Peninsular Malaysia, west of Sabah and Sarawak offshore areas. Forecast points at Sulu Sea were focused at the east of Sabah offshore areas. This paper will present the simulation results of tsunami wave height and arrival time at various forecast points. The findings of this study show that the range of tsunami wave height at Sulu Sea is higher than that of South China Sea. The tsunami arrival time at Sulu Sea is less than South China Sea. It can be concluded that Sulu Sea poses worse tsunami threat than South China Sea to the Malaysian offshore areas.

The beach is a boundary between the ocean and land changes with time due to erosion and sedimentation events. The study of beach changes aims to understand the condition of the coast towards the factors that influence it, such as wave height, wave angle of arrival, beach area, depth, and groin. The study used synthetic beach conditions data. Furthermore, changes in shoreline caused were modelled with one-line models using numerical method solutions. Modeling results show that shoreline changes increase with time, and are strongly influenced by wave height, wave angle and the distance of waves breaking to the beach. Changes in the coastline are also influenced by the location of the beach structures, the structures of the beach that are parallel to the coast will provide better results to prevent the coast than the structure located off the coast.