npj Climate and Atmospheric Science最新文献

Eurasian teleconnections in boreal summer significantly influence regional climates and extremes, yet their dynamic origins remain largely unclear. Here, we revealed two critical modes of tropical convection that drive these Eurasian teleconnections in boreal summer. The first mode is characterized by suppressed convection in the equatorial eastern Pacific, coupled with enhanced convection extending from the equatorial Atlantic to northern Africa. In contrast, the second mode displays similar suppressed convection in the equatorial eastern Pacific, but features enhanced convection in the Gulf of Mexico and the equatorial Atlantic. These two modes result in markedly different atmospheric teleconnections, leading to distinct surface air temperature anomalies across the Eurasian continent. Both modes arise from the combined effects of sea surface temperature anomalies in the eastern Pacific and the North Atlantic/Indian Ocean. This study offers new insights into dynamics and seasonal predictions of boreal summer Eurasian climates.

Severe urban air pollution in China is driven by a synergistic conversion of SO₂, NOx, and NH₃ into fine particulate matter (PM_2.5). Field studies indicated NO₂ as an important oxidizer to SO₂ in polluted atmospheres with low photochemical reactivity, but this rapid reaction cannot be explained by the aqueous reactive nitrogen chemistry in acidic urban aerosols. Here, using an aerosol optical tweezer and Raman spectroscopy, we show that the multiphase SO₂ oxidation by NO₂ is accelerated for two-order-of-magnitude by a copper catalyst. This reaction occurs on aerosol surfaces, is independent of pH between 3 and 5, and produces sulfate by a rate of up to 10 µg m^-3_air hr^-1 when reactive copper reaches a millimolar concentration in aerosol water – typical of severe haze events in North China Plain. Since copper and NO₂ are companion emitters in air pollution, they can act synergistically in converting SO₂ into sulfate in China’s haze.

Global warming is accelerating climate disasters by triggering tipping points in various Earth systems. Although changes in precipitation patterns in High-Mountain Asia (HMA) have been extensively studied, the specific thresholds that trigger rapid snowfall loss remain unclear. A continuous piecewise linear regression model was employed to classify HMA into four distinct precipitation regimes: insensitive snowfall-dominated areas, sensitive snowfall-dominated areas, sensitive rainfall-dominated areas, and insensitive rainfall-dominated areas. Our results show that future warming will increase the sensitivity of winter and spring snowfall to climate change, whereas summer and autumn snowfall will become less sensitive. All four precipitation regimes exhibit an upward shift to higher elevations, with varying rates of elevation gain across regions and seasons. Temperature is the primary driver of snowfall loss, whereas relative humidity mitigates it. This study identifies high-risk areas vulnerable to snowfall loss, to help guide the development of effective mitigation strategies.

Previous studies focused on the spatial diversity of ENSO’s influence on tropical cyclones (TCs) in the western North Pacific (WNP), with less emphasis on temporal evolution. This study examines the variability of TC genesis in the WNP during boreal autumn (September-November) across three types of La Niña transitions: cyclic, multi-year, and episodic. The findings highlight significant differences, particularly in the South China Sea’s (SCS) role within the WNP region. During a cyclic La Niña, the SCS TC frequency is approximately 2.6 times greater than those of the other two types due to higher local humidity from increased water vapor transport from the Indian Ocean and convergence in the SCS, driven by an anomalous cyclone in the SCS and Maritime Continent. Observations and model simulations revealed that a warmer sea surface temperature in the Philippine Sea, a delayed effect of the preceding El Niño, triggered this cyclonic circulation and moisture influx.

Deciphering the driving forces behind spatial heterogeneity of regional hydroclimate changes is significant for developing strategies for water management. This study presents speleothem δ¹⁸O, δ¹³C and Mg/Ca records spanning the last deglaciation from Yingpan Cave, northeastern Yunnan in southwestern China. Speleothem δ¹³C and Mg/Ca indicate a gradual drying trend in northeastern Yunnan, aligning well with the variations in central China but contrasting with those of central-southern Yunnan. We propose that a decreased zonal sea surface temperature (SST) gradient in tropical Pacific (El Niño-like) shifted the West Pacific Subtropical High (WPSH) southwestward, leading to wetter conditions in northeastern Yunnan. Meanwhile, decreased precipitation in central-southern Yunnan was driven by weakened Indian summer monsoon rainfall associated with El Niño-like conditions, creating a dipolar hydrological pattern in Southwest China. Our results indicate that the spatial heterogeneity of hydroclimate can be modulated by the same triggers but have different processes and mechanisms and hence responses.

Inequalities in exposure to PM2.5 reflect disproportionate distribution of health risks across populations. This study assesses global PM2.5 exposure inequalities and associated trends since 2000. Results show that 118 countries reduced intra-country inequalities, but global disparities intensified due to widening gaps between developing and developed regions. By identifying pathways and country-specific contributions to global inequalities, we show that environmental policy shifts in major economies can rapidly reshape global inequality patterns.

Severe East Asian dust storms occur in spring due to dust-emitting winds in the Gobi Desert associated with Mongolian cyclones. The present study performs the first quantitative assessment of the contributions of Mongolian cyclones to springtime dust activity in East Asia, based on multiple reanalyses and observational datasets for 2001–2022. Atmospheric depressions dominate dust activities in Northern China, explaining ~90–92% of the total dust emissions in the Gobi Desert and ~88–93% of the dust aerosol optical depth (τ) downwind, depending on the dataset. Mongolian cyclones, defined as long-living and mobile atmospheric depressions, explain almost half (~34–47%) of the Gobi’s total dust emissions and τ downwind, and are the primary driver of high-impact dust storms. The number of Mongolian cyclones, along with the dust activity, has decreased since 2001, with a spatial pattern of the dust emission trend that is consistent with the northward shift of cyclone tracks.

Ultra-high-resolution mass spectrometry was used to investigate the characterization of aerosol organonitrates (ONs). ONs featured high-molecular-weight (HMW), high unsaturation, and high functionalization. Under high air pollution events, the number of N₁O_x class ONs composed of aliphatic and aromatic compounds increased with high levels of oxidation. In the daytime, highly unsaturated aliphatic-ONs were continuously produced. In the nighttime, the atmospheric oxidation of NO₃ radicals promoted ONs. N₂O_x class ONs were mainly comprised of multi-generation oxidated aliphatic compounds with high unsaturation. Most of the N₂O_x-ONs were from cooking. Biomass burning also played an indelible role in the formation of ONs. In the daytime, atmospheric photodegradation led to the removal of the HMW ONs, especially aliphatic ONs. During nighttime, the NO₃ oxidation radicals inhibited the generation of ONs, especially anthropogenic ONs. This study improves the understanding of the source, formation, and evolution of HMW ONs under the demand for continuous PM mitigation.

Atlantic Niño is the dominant mode of interannual climate variability of the tropical Atlantic, prominently influencing climate conditions over local and remote regions. A recent study has identified two types of Atlantic Niño–central and eastern Atlantic Niño (CAN and EAN), with warm sea surface temperature (SST) anomalies centered in the central and eastern basins, respectively. Here we investigate their formation mechanisms by performing a mixed layer heat budget analysis and conducting numerical experiments. Results show that the development of both types is contributed by upper-ocean vertical processes caused by westerly wind anomalies. Furthermore, anomalous horizontal advection also plays an important role but is associated with distinct physical processes in the CAN and EAN. The difference is related to the climatological distribution of tropical Atlantic SST, exhibiting two warm centers located in the southwest and northeast tropical basins during boreal spring. Consequently, eastward current anomalies during Atlantic Niño cause warming only in the western-central equatorial Atlantic south of the equator, contributing to the formation of CAN. In contrast, Ekman convergence anomalies cause SST warming in the southwest and northeast equatorial Atlantic during CAN and EAN, respectively, favoring both types. We further analyze initiation mechanisms for the two Atlantic Niño types and find that CAN and EAN are triggered by the subtropical South Atlantic warming and oceanic Kelvin waves, respectively. These results suggest that the two Atlantic Niño types are associated with distinct physical drivers.

The diurnal temperature range (DTR), the difference between daily maximum and minimum temperature, is important for the impact of extreme temperatures, but despite physical links to aerosol forcing previous studies have struggled to attribute observed DTR changes to aerosols. Using causal inference, we can clearly identify aerosols as a driver of European DTR change since 1940. Following a decrease from the 1940s, since the 1980s the European DTR has increased by about 0.5K due to a reduction in European aerosol emissions leading to cooler nights relative to days. Agreement between causal effects estimated from observations with those estimated for two CMIP6 models evaluates the models’ microphysical and radiative parameterizations. From causal effects, we also derive effective radiative forcing estimates of aerosols on surface shortwave during European summer, which amount to [−1.7; −1.5] Wm⁻² in observations and one model, while it is less negative in the other model ([−0.9; −0.8] Wm⁻²).