npj Climate and Atmospheric Science最新文献

The El Niño/Southern Oscillation (ENSO) stands out as the most prominent interannual climate mode, profoundly affecting global climate. This phenomenon exhibits remarkable diversity and is commonly classified into two groups based on the location of maximum sea surface temperature anomalies. One of the two flavors with the maximum anomalous warming in the central equatorial Pacific is called El Niño Modoki. It has been suggested that anomalous zonal advection primarily contributes to the development of the positive sea surface temperature anomalies. Using outputs from a realistic ocean model simulation, here I show for the first time that anomalous vertical mixing makes a dominant or comparable contribution to the anomalous zonal advection during the development of El Niño Modoki in four out of six simulated events. The present finding provides a significant advancement in the understanding of El Niño Modoki, potentially contributing to more reliable future projections of ENSO.

Tropical cyclone (TC) precipitation is a major cause of severe floods and landslides. This study compares the characteristics of TC precipitation over land and ocean in the Northern Hemisphere using satellite data from 2001 – 2020. An analog selection method is used to pair each landfalling TC case with an oceanic case of the same intensity and similar atmospheric environmental conditions. Here we show robust discrepancies in rainfall rate and pattern for TCs over land and ocean. The average rain rates of landfalling TCs are 27.8% lower than those of oceanic TCs. Nonetheless, the rainfall is more intense on the right side of landfalling TCs compared with oceanic TCs. This left-right difference pattern tends to be more pronounced for TCs with faster translation speeds. Numerical simulations indicate that the increased surface friction and moisture convergence are largely responsible for the increased rainfall rate on the right side of landfalling TCs.

The occurrence of winter lightning concentrates in a few specific regions in the world, including the Mediterranean, where electromagnetic signatures of this interesting dangerous phenomenon have not yet been studied in detail. We investigate the initial stage of energetic negative cloud-to-ground winter lightning flashes in the West Mediterranean region using broadband magnetic field measurements (5 kHz–90 MHz) recorded in winter 2014/2015, which was unusually rich in global lightning activity. We found that the winter pre-stroke processes leading to the high peak current lightning (<−100 kA) lasted on average only 1.7 ms (in one case only 220 µs). Rapid evolution of energetic lightning indicates that leader initiation charge centers can be as low as 500 m above the ground. The measured distribution of pre-stroke pulse amplitudes and interpulse intervals can be used to model the charge structure in the lower thundercloud dipole and to derive the properties of in-cloud lightning channels.

The underexplored impact of climate change on influenza outbreak severity and duration hampers our understanding of how climate-driven changes affect transmission dynamics. Our study employs the SIRS (Susceptible-Infectious-Recovered-Susceptible) model to simulate incremental temperature rises (2.5 °C, 5 °C, 7.5 °C, and 10 °C) in winter and summer. Results show warming significantly influences infections across seasonal, interannual, and decadal scales. Higher temperatures significantly impact infection rates, especially in autumn and winter, with long-lasting effects extending 5-6 years. Sustained warming lowers the total infection numbers compared to pre-warming levels. When winter and summer experience simultaneous warming, infection fluctuations during the warming period are mainly driven by winter warming. Winter warming also lowers the peak-to-trough infection ratio, reducing epidemic intensity fluctuations. Additionally, parameter choices can significantly affect the impact of warming on infection rates. Warming of varying intensity and duration can significantly impact influenza outbreaks, potentially altering their seasonal patterns in a global warming context.

Wind-induced particulate matter (PM) resuspension is an increasingly recognized contributor to urban air pollution. A CFD model of 2D street canyon geometry was developed that can replicate the process of resuspension. Model created the wind speed vs concentration increase due to resuspension relationship and its key properties: threshold wind speed causing resuspension (TWSR) and concentration increase. At least 8.75 m/s in 10 m height inlet wind speed before street canyons was needed to start the resuspension, leading to PM₁₀ concentrations often exceeding 1 μg/m³, with peak values reaching as high as 3 μg/m³. The model can predict the behavior of resuspension well, but it cannot capture all the factors acting in the real environment to match precisely the air quality data. Silt load remains the greatest unknown factor in determining the overall magnitude of resuspension, with observed increases in PM₁₀ concentrations up to 6 μg/m³ in air quality data.

The Atlantic Meridional Overturning Circulation (AMOC), a tipping climatic component, has a quasi-global impact and it could induce a cascade of critical transitions. There is considerable uncertainty regarding the location of the overturning circulation’s current state relative to its stability thresholds. We identify similarities between observational and simulated spatial patterns, bifurcation diagrams and phase spaces linked with AMOC changes. The resemblances suggest that the overturning already underwent a Hopf bifurcation and entered a bistable regime before 1854, that it suffered a Rate-induced tipping around 1970, possibly linked with the Great Salinity Anomaly, and that it approached the attractor of its weak state. These changes in the overturning circulation dynamics are indicative of complex structural stability variations during the preindustrial revolution, which underline the need for a long-term temporal assessment of the overturning circulation stability on multi-centennial to millennial time-scales, to set its contemporary and future evolution in a long-term context.

We examine mesoscale convective organisation in the tropical western Pacific using a multivariate analysis of column humidity, precipitation and sea surface temperature (SST) observations. We demonstrate that in boreal summer and autumn, convection remains spatially random despite radiative-feedbacks acting to aggregate convection, which we attribute to the high density of convective moisture sources and the role of wind shear. Instead, in winter and spring, a weak meridional SST gradient exists and convection is usually clustered over the regions of warmer SSTs, with significant meridional humidity gradients. However, this is sporadically interrupted by episodes of convection migration to the coldest SSTs and limited spatial humidity variance. These episodes are the result of westward propagating equatorial waves, which remove meridional humidity gradients. It appears that the drivers of mesoscale convective clustering and humidity variability in the Pacific warm pool are the SST gradients, shear, and equatorial wave dynamics.

El Niño induced equatorial precipitation centers shift to different longitudinal positions during Eastern Pacific (EP) and Central Pacific (CP) El Niño events, resulting in distinct global climate responses. However, it remains unexplored how EP and CP El Niño forced precipitation changes may differ under global warming. Here, we find that the longitudinal separation of precipitation centers in EP and CP El Niño events is projected to increase under global warming. Specifically, the precipitation anomalies during EP El Niño events will shift further eastward, while those during CP El Niño will intensify in their original positions. This change is attributed to the amplified equatorial thermocline feedback as the mean thermocline shoals. A more meridionally confined El Niño structure under global warming generates extra boundary layer moisture convergence in situ. This intensifies the precipitation anomalies in CP El Niño but shifts the precipitation center eastward towards the maximum sea surface temperature anomaly center in EP El Niño. The projected increased longitudinal separation of precipitation centers suggests that the differences in global climate impacts between EP and CP El Niño events will intensify under global warming.

A zonally asymmetric surface temperature trend has been observed in the boreal winter over the Northern Hemisphere continents from the late 1980s to the late 2000s. While the cooling trend was pronounced over central Eurasia, the warming trend was evident over Northeastern North America and Greenland. However, such trends were suddenly reversed in the late 2000s. The surface energy budget reveals that the downward longwave radiation due to the Arctic Oscillation (AO)-related temperature and moisture advection was mostly responsible for such trends. While the sensible heat flux also contributed to the temperature trend over central Eurasia, other terms play a minor role. This result suggests that a zonally asymmetric temperature trend in boreal winter and its recent reversal in the Northern Hemisphere continents are largely driven by the internal climate variability, particularly the AO-related thermodynamic and dynamic processes.

How the shape characterization of the concentration-response relationships between particulate matter (PM) and all-cause mortality influences life expectancy (LE) gains remains unclear. Based on the Pearl River Cohort, the 2021 World Health Organization air quality guidelines, and an integrated comparative risk assessment framework, we identified sigmodal relationships between PM_2.5, all-cause mortality, and LE reduction. A 10-unit increase in PM_2.5 was associated with an excess mortality risk of 31.2% (95% uncertainty interval: 27.6–35.0%). Reducing PM_2.5 to the guideline threshold of 5 μg/m³ could prevent 0.193 (0.175–0.212) million deaths, contributing to a 4.07–year (3.60–4.52) average LE gain. In contrast, PM_2.5 reductions by 5.6% and 10% resulted in smaller LE gains of 0.33 (0.28–0.38) and 0.58 (0.49–0.67) years, respectively. These findings highlight the importance of accounting for the nonlinear relationship in air pollution control and provide essential incentives for tailoring sustainable plans to enhance population longevity.