The relationship between the destructive potential of tropical cyclones (TCs) over the western North Pacific (WNP) (as quantified by the Power Dissipation Index) and El Niño events is investigated in this work. Results show that the destructive potential of TCs is significantly affected by how rapidly El Niño decays from a positive phase to a negative phase. For TCs occurring during ‘slow-transforming’ El Niño, more of them initiate over the southeastern part (0°–15 °N, 150 °E–180°) of the WNP and the destructive potential of TCs is usually strong. In contrast, weaker destructiveness is indicated during ‘rapid-transforming’ periods, with fewer TC formations in the southeastern area. This weaker destructiveness during rapid-transforming El Niño years is mainly caused by anomalously cooler upper-ocean conditions in the central Pacific, negative relative vorticity anomalies, and increased vertical wind shear in the WNP. These findings may have important implications for the seasonal prediction of TC changes in the WNP.
Gravity waves (GWs) are important for vertical coupling between the lower and upper atmosphere on Mars. Saturated GWs will promote the acceleration of mean flow and turbulence generation, causing diffuse transport of energy and momentum. We analyze the spectral characteristics of GWs in the thermosphere on Mars during the low solar activity of Martian Year (MY) 35, based on CO2 density measured by the Neutral Gas and Ion Mass Spectrometer (NGIMS) on board Mars Atmosphere and Volatile EvolutioN (MAVEN). The results are compared with those of MY33 at the higher solar activity. The vertical wavenumber spectral density obtained in the Martian thermosphere is similar to the semi-empirically predicted saturation spectrum in the Earth’s atmosphere, with a logarithmic spectral slope around −3. The average spectral density of GWs shows saturation between 160 and 200 km and decreases with increasing altitude. Compared to MY33, GW activity is larger and less attenuated in MY35 as it propagates upward, implying that waves experience more favorable propagation conditions during low solar activity. Also, the dependence of GW activity on local time during this period is found to be different from previous studies, with the strongest GWs in the spring of MY35 occurring within 6–12 hr on the dayside, suggesting that the amplitude of the GWs in the Martian thermosphere during low solar activity is less controlled by the background temperature and is subject to dissipative effects of other factors, such as molecular viscosity and thermal conduction.
The Martian atmospheric waves perturbation Datasets (MAWPD) version 2.0 is the first observation-based climatology dataset of Martian atmospheric waves. It contains climatology-gridded temperature, gravity waves, and tides spanning the whole Martian year. MAWPD uses the Data INterpolating Empirical Orthogonal Functions method (DINEOF) reconstruction method for data assimilation with the observational data from the Mars Global Surveyor (MGS), Mars Reconnaissance Orbiter (MRO), Mars Atmosphere and Volatile EvolutioN (MAVEN), Mars Pathfinder (MP), Mars Phoenix Lander (MPL), Mars Exploration Rover (MER) and Mars Express (MEX) temperature retrievals. The dataset includes gridded fields of temperature (Level 1 data) as well as the physical quantities of GWs (Level 2 data, amplitude, and potential energies), SPWs and tides (Level 2 data, amplitude, and phase). The MAWPD, based entirely on multiple reliable observations, provides climatological background atmospheric information of temperature and wave disturbances on Mars. The dataset is not only useful for observation-based scientific studies concerning Martian atmospheric waves, e.g., circulation, dust storms, and wave excitation mechanism, but also for cross-validating with model-based datasets or model results.
Gravity waves (GWs) are important for the vertical coupling of the Martian atmosphere. The middle atmosphere is the key region where GWs propagate to the upper thermosphere and generate momentum and energy exchange, but the knowledge of middle-atmosphere GWs is incomplete, due to the lack of observations with the kilometer-scale resolution. We have analyzed the climatology of GW activity in the middle and upper atmosphere of Mars using 20–180 km temperature profiles measured by the Atmospheric Chemistry Suite instrument on board the Trace Gas Orbiter. The results show that the amplitudes of GWs extracted in this study are generally less than 15% and that the centers of the strongest GW activity vary significantly with the seasons. Second, the strongest GW activity in the mesosphere indicates the strong dissipation effects of the mesopause, and the mid-atmospheric GWs show a seasonal pattern that is stronger in the winter hemisphere. During the global dust event of MY34, the enhancement of GWs in the middle atmosphere is most pronounced at low and middle latitudes where the dust storms are active. It is possible that changes in the temperature structure of the middle atmosphere adjust the atmospheric circulation and thus improve the propagation of GWs. Furthermore, GW activity is stronger on the dayside than on the nightside, and there is no significant correlation between amplitudes and background temperature. This suggests a limited role of convective instability in limiting the growth of GWs in the middle atmosphere, with nonlinear damping competing with that of molecular diffusion at different harmonics.
Gravity waves (GWs) are important for understanding the coupling between dust activity and atmospheric dynamics on Mars. Using temperature and water-vapor profiles from the Near-Infrared channel of the Atmospheric Chemistry Suite (ACS-NIR) onboard the ExoMars Trace Gas Orbiter (TGO), we investigate wave-related temperature perturbations during global and regional dust-storm periods. Comparisons between Mars Years (MY) 34 and 35 reveal a localized enhancement of wave-related perturbations at southern high latitudes, particularly between 60°S and 90°S and 40–90 km. This enhancement persists after controlling for differences in observational sampling. The gravity-wave-related potential-energy proxy is approximately 2–3 times larger during the MY34 global dust storm, with a weaker enhancement during the regional event. These variations coincide with substantial differences in background temperature, static stability, and zonal winds, suggesting that dust-related changes in the atmospheric environment may modify wave propagation and filtering. Water-vapor abundance is also higher in the same region, but is more likely associated with dust-driven large-scale circulation, while wave-related processes may provide additional local modulation. These results provide observational constraints on dust–wave–water coupling in the Martian middle atmosphere.