npj Climate and Atmospheric Science最新文献

In this study solar elevation angle is shown to have a dominant impact on the net radiation due to tropical cyclone (TC) clouds. As solar elevation angle increases, net cooling effects from TC clouds dominate over net warming effects. From 2001 to 2020, the radiative effect of TC clouds remained stable. However, because of the strong dependency on solar elevation angle, future changes in seasonal occurrence could affect this contribution.

This study investigates typhoon-induced mesoscale cyclonic eddies (TIME) in the western North Pacific. A total of 69 potential TIME candidates (1995–2018) were identified using global mesoscale eddy trajectory atlas and JTWC typhoon data. Subsequently, systematic analysis procedures were applied to those candidates. Analysis revealed that three cyclonic ocean eddies (COEs) were likely triggered by typhoons Rosie (1997), Nida (2009), and Ma-on (2011). Numerical modeling with a regional ocean modeling system (ROMS) reconstructed the ocean environment during these events. Semi-idealized experiments confirmed that typical TIME events arise from the energy transfer between kinetic and potential energy, with vertical diffusion and horizontal advection contributing significantly to COE spin-up. Divergence and vertical advection terms suppress excessive COE growth. Given the increasing intensity and slower movement of typhoons due to global warming, more TIMEs are expected in the future. Stronger, longer-lasting TIMEs may have significant climate impacts and should be a focus of future research.

The demise of the Ming Dynasty (1368–1644) and the rise of the Qing Dynasty (1644–1912) marked an epochal moment in Chinese and world history. Attention has been given to the North China droughts during 1627–1643 that destabilized the Ming Dynasty. However, there is little attention paid to how climate influenced the rise of a minority Manchu state in Northeast China and its conquest of the Ming. Here, we find that contrasting climate conditions between North and Northeast China persisted over a six-decade period (1581–1644), which diversely affected economic, societal, and political changes at the regional level. Five successive megadroughts ravaged North China, while relatively wet and mild climate conditions prevailed in the Manchu homeland of Northeast China. Furthermore, in the early decades of Manchu rule in North China (1645–1680), increased precipitation facilitated the Qing Dynasty’s consolidation. Reconstructions and climate model simulations revealed that these unusual climatic patterns were influenced by the centennial variation of clustering El Niño-Southern Oscillation (ENSO) events and were amplified by the Little Ice Age cooling. These findings shed light on how long-term contrasting future climate changes could lead to divergent socioeconomic responses, potentially increasing the risk of conflict between neighboring states.

This paper systemically assesses the performances of two assimilation methods, i.e., the Offline Ensemble Kalman Filter (OEnKF) and the Hybrid Gain Analog Offline EnKF (HGAOEnKF) with three proxy databases, on reconstructing the temperature and precipitation during the last two millennia. The results show that, among three databases, increasing the number of proxy records significantly improves the reconstruction skill for both assimilation methods, with a larger improvement in HGAOEnKF. In the instrumental era, six reconstructions have comparable skill (similar correlation coefficients, CEs, and RMSEs) when validated against out-of-sample proxy records and instrumental reanalyses. During the pre-industrial era, HGAOEnKF shows better assimilation performance by improving the background field of assimilation when the number of proxy records is limited. Compared with the temperature reconstruction, the skill of precipitation reconstruction is relatively lower. The proxy records from the ocean contribute more to the temperature reconstruction skill with both assimilation methods. Finally, a new reanalysis product (NNU-2ka Reanalysis) is generated through the HGAOEnKF with the expanded proxy database.

Brazilian Cerrado has the largest annual burned area (BA) in South America, with strong interannual variability. However, there is limited understanding of which climatic drivers lead to the interannual variability of Cerrado fires. This study found sea surface temperature anomalies (SSTAs) in the North Tropical Atlantic (NTA) are positively correlated with the Cerrado BA. Positive SSTAs over the NTA modulate the intertropical convergence zone (ITCZ) position, which suppresses atmospheric convection over the Cerrado region. While NTA SSTA peaks March, the precipitation reduction in Cerrado is pronounced during June–August, since the ITCZ shifts northward and the local monsoon weakens. This leads to moisture deficits for the following months, significantly enhancing fire activity in August–October. This result implies NTA can exert an independent influence on Cerrado in addition to the traditionally considered factor, the El Niño–Southern Oscillation. This improves the predictability of fire activity because NTA precedes the fire season by 7 months.

Fires are a major source of air pollutants in Southeast Asia. Over the past few decades, there has been an increase in fire activities in this region, and the causes are not entirely clear. By analyzing multiple observational and reanalysis datasets, as well as conducting climate model simulations, we uncover a distinct positive impact of Arctic sea ice loss on Southeast Asian fire weather. There is a possibility that the fall in the autumn Sea Ice Concentration (SIC) over the Beaufort Sea the year prior contributes to the increase in boreal spring fire activity in Southeast Asia. This sea ice reduction generates a local low warm anomaly, triggering an upper atmosphere Rossby wave train that propagates from the tropical Pacific to Southeast Asia and arrives in Southeast Asia as a high-pressure anomaly with descending air. Moreover, two meridional cells originating from equatorial and polar regions intensify the sinking airflow. This Arctic-driven teleconnection causes high pressure with warmer and dryer surfaces in Southeast Asia, creating favorable conditions for fire ignition and expansion. Based on the fire weather classification criteria, a negative change in SIC of one standard deviation below the climatological mean will expose over 500 million people to very high levels of fire pollution across Southeast Asia, and the number of people exposed to extreme fires will be 1000 times greater than in the present scenario. The above-mentioned mechanism has great implications for projecting decadal air quality and developing relevant health policies to cope with climate change in Southeast Asia.

The Gulf and Atlantic Coastal Plains of the southern United States are characterized by a wide continental shelf that was subaerially exposed for ca. 80,000 years during glacial-interval marine regressions and transgressions. Given their present submergence, little is known about the vegetation dynamics, particularly at annual time scales, of these formerly terrestrial sites due to erosional processes associated with marine transgressions. Here, we present an annually resolved and well-replicated 489-year tree-ring chronology from macrobotanical specimens—anatomically identified as Taxodium distichum (L.) Rich.—collected in situ from a recently exposed submerged forest in 18 m water depth in the northern Gulf of Mexico. This chronology not only reveals historical vegetation dynamics at annual resolutions during Marine Isotope Stages 3–5a, but it also captures a catastrophic mortality event likely connected to intense storm activity, perhaps driven by freshwater fluxes from Heinrich events. Our findings are supported by coupled climate model simulations from the last glaciation, providing new insights into the environmental history of the southeastern US coastal regions.

This study aimed to quantify the age-specific risk and burden of fall-related mortality attributable to ambient temperature among older adults in China. Using data in 2759 counties/districts during 2005–2022, we found that both high and low temperatures significantly increased the risk of fall-related mortality, with a notably higher risk associated with high temperatures, particularly among the oldest old and people in Southern China. Projections indicate that the fall-related mortality burden associated with temperature will increase in the future, primarily affecting the oldest old, and the increase is mainly driven by climate change. These findings highlight the need for effective adaptation strategies to reduce the impact of temperature on fall-related mortality among older adults, particularly facing double challenges of climate change and population aging.

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.