npj Climate and Atmospheric Science最新文献

Ozone is the primary air pollutant in eastern China during the warm season. Clarifying the differences in the spatio–temporal evolution of the ozone formation sensitivity between ozone polluted days and clean air days is key for the precise formulation of ozone prevention policies. By combining ground–and satellite–based remote sensing with ground station observations, we identified large spatio–temporal differences in the ozone formation sensitivity in eastern Chinese cities under different ozone pollution levels. Diurnally, the NO₂ concentration was higher in the morning and lower at noon on the ozone exceedance days. The HCHO concentration was higher throughout the day, and the transition limited regime or NO_x–limited regime contributed more to the ozone formation sensitivity on the ozone exceedance days. Vertically, the ratio of HCHO to NO₂ (FNR) was higher on ozone exceedance days, and the contributions of NO_x–limited regime at 0–2 km and the transition limited regime at 0–1 km on ozone exceedance days increased considerably. Spatially, HCHO in the North China Plain and middle–lower Yangtze River Plain was significantly increased on ozone exceedance days, while the NO₂ concentration in the southeast hills was increased on ozone exceedance days. The difference in FNR values between northern and southern cities in eastern China on O₃ exceedance days narrowed, and the ozone formation sensitivity in eastern China tended to be under a transition limited regime. The shifts in the ozone formation sensitivity under different ozone pollution levels implies that controlling only one of the precursors cannot achieve the best O₃ prevention effect, and the most appropriate ratio of O₃ precursor emission reductions should be designed according to ozone formation sensitivity in the different regions.

The amplified warming on the Tibetan Plateau (TA) is a distinctive characteristic of global climate change, leading to various climate responses with far-reaching implications. This study investigates the influence of interannual variation of TA on summer precipitation over East Asia (Pre_EA) using observational data and a Linear Baroclinic Model (LBM). When TA exceeds the Northern Hemisphere average, summer precipitation in the Yangtze River Valley significantly decreases, while it increases in North China and South China, resulting in a tripole Pre_EA pattern. Notably, the relationship between TA and Pre_EA is independent of the El Niño-Southern Oscillation (ENSO) and explains more variance in Pre_EA than ENSO. Our analysis reveals that TA enhances the tripole Pre_EA pattern by modulating moisture transport and vertical motion in the East Asia-North Pacific regions. Specifically, positive TA is linked to significant local tropospheric warming, which intensifies and eastward expands the South Asian High, creating a double-gyre meridional circulation over East Asia. Additionally, positive TA induces an eastward-propagating wave, reinforcing a midlatitude anomalous high-pressure belt over East Asia and the western North Pacific regions. These circulation changes weaken the East Asian subtropical jet, form a notable double jet configuration, and promote subsidence over mid-latitude East Asia. Moreover, anomalously warm sea surface temperatures in the Northwestern Pacific reinforce the TA-Pre_EA relationship by contributing to the mid-latitude East Asia-North Pacific high-pressure belt. Our LBM model experiments support these findings. Our study provides an in-depth understanding of the physical processes influencing summer precipitation variability in East Asia.

Winter Arctic sea ice is a crucial climate indicator, declining at an accelerated rate compared to the past and playing a significant role in Arctic amplification over recent decades. The sea-ice concentration (SIC) in the Greenland–Barents Sea (GBS) shows considerable interannual variability, yet the link between this variability and the El Niño–Southern Oscillation (ENSO) remains uncertain. Here, we identify a reversed relationship between the autumn Central Pacific (CP)-type ENSO and the winter GBS SIC around the mid-1980s. Observational and model experiments demonstrate that, before the mid-1980s, CP ENSO triggered a double wave pattern propagating toward the Arctic, generating a positive geopotential height anomaly in the Arctic. Such an anomaly, along with a northerly anomaly, favored cold-air advection and intrusion into the GBS, resulting in an increased SIC. After the mid-1980s, however, CP ENSO only induced a single wave train towards the Arctic, favoring a positive geopotential height anomaly over Iceland. As a result, the southerly anomaly transported abundant moisture into the GBS and consequently reduced the SIC. The variation in wave patterns can largely be attributed to the sea surface temperature anomaly in the tropical Atlantic induced by CP ENSO. Our findings highlight the unstable connection between tropical and polar regions, which provides a basis for better understanding the mechanisms of Arctic sea-ice changes.

Aerosols, derived from natural processes and human activities, present various risks to the environment and human health. In this regard, the role of recent pollutant environmentally persistent free radicals (EPFRs) should not be overlooked. However, the oxidative toxicity and mass transfer processes of EPFRs in liquid-phase environments remain completely understood. In this study, the dispersion characteristics of EPFRs and their contributions to the oxidation potential (OP) and reactive oxygen species (ROS) in sea spray and size-resolved PM were investigated and compared. The results showed that the sea spray contained fast-decaying C-centred EPFRs with a half-life of 0.32 years. The concentration ranged from 0.3 × 10¹³ spins/m³ to 7.5 × 10¹³ spins/m³. It increased as the samples approached the coast. Moreover, the size-resolved PM contained slow-decaying O-centred EPFRs with a half-life of 0.51 years. The concentration ranged from 4.57 × 10¹³ spins/m³ to 11.46 × 10¹³ spins/m³, which was higher than that of most sea spray samples. The interaction between sea spray and water mainly generated hydroxyl free radicals (54 ± 3%), whereas the size-resolved PM mainly generated organic free radicals (64 ± 5%). Correlation analysis revealed that EPFRs may be involved in ROS generation. In addition, the mass transfer of EPFRs between the PM and sea spray may have been controlled by both gas and liquid films. The concentration of EPFRs at the phase interface was calculated to be 4.92 × 10¹³ spins/m³. In summary, EPFRs positively contribute to OP and ROS production.

Global warming is jeopardizing the artificial snow making conditions, shortening outdoor ski resorts opening days and increasing operation cost, severely threatening the sustainability of outdoor ski industry. The sustainability of 772 outdoor ski resorts in China under RCP 4.5 climate scenarios in 2030 s and 2050 s had been analyzed. (1) The skiing sports developed prominently during 1996 to 2023 and will boom in China in the coming decades. (2) Accelerated global warming is the main threat to the sustainability of outdoor ski resorts of China. However, snowfall isn’t a critical influencing factor in the coming decades. (3) The outdoor ski resorts in south China are facing the most threats and are the most unsustainable resorts. We proposed a nexus of Government-Operator-Skier adaptation framework for adapting climate change threats and advocating the temporal small-scale ski resorts are more adaptive as their high water and energy efficiencies for saving water and electricity resources.

The global flood risk urges an improved understanding of flood magnitude and its mechanism, which needs insights from pre-instrumental flood investigations. Due to data scarcity, reconstructing pre-instrumental flood magnitudes relies on statistical downscaling, failing to capture nonlinear and dynamic characteristics. We developed a dynamical approach, NorESM-WRF-SWAT, integrating a global climate, a regional, and a hydrologic model to investigate the 1931 Yangtze River flood (the deadliest in the world) and compared it with the 1998’s. Through validation, our method outperforms the statistical method in simulating precipitations and river discharges. For the first time, we presented detailed insights into the intensity and duration of the 1931 flood, revealing a smaller magnitude but associated with an amplified loss, likely due to social vulnerability and reduced societal resilience compared to the 1998’s. While successful simulation can be interfered with by model variability, our dynamical method shows promise for simulating pre-instrumental flood and building a long-term pre-instrumental-hydrology database.

Simulating accurately the South Asian summer monsoon is crucial for food security of several South Asian countries yet challenging for global climate models (GCMs). The GCMs suffer from some systematic biases including dry bias in mean monsoon rainfall over the India subcontinent and excessive equatorial light rain between which the relationship was rarely discussed. Numerical experiments are conducted for one month during active monsoon with global quasi-uniform resolution of 60 km (U60 km) and 3 km (U3 km) separately. Evaluation with observations shows that U3 km reduces the dry bias over northern India and excessive light rain over the equatorial Indian Ocean (EIO) that are both prominent in U60 km. Excessive light rain in U60 km contributes critically to stronger rainfall and latent heating over the EIO. A Hadley-type anomalous circulation is thus induced, whose subsidence branch suppresses updrafts and reduces moisture transport into northern India, contributing to the dry bias. The findings highlight the importance of constraining excessive light rain for regional climate projection in GCMs.

In this study, we examine the predictability of tropical cyclone (TC) track density in the subseasonal-to-seasonal (S2S) reforecast ensembles of the European Centre for Medium-range Weather Forecasts (ECMWF) using the method of average predictability time (APT). Eleven of the retrieved APT modes (APTMs) of TC track density possess an APT longer than 1 week. The most predictable of them, APTM-1, has an APT of almost three weeks and is found to be closely linked to the Boreal Summer Intraseasonal Oscillation (BSISO) and monsoon variability. Another discovery is the strong relationship between APTM-7 and the activity of mixed Rossby-gravity (MRG) waves and tropical depression (TD) type disturbances despite its short APT of ~12 days. We further carry out a simple case analysis to see how the relatively high predictability of APTM-1 manifests in the S2S model. Our work provides a new possibility for improving medium-range TC forecast skill, and has revealed how underlying tropical variability can play a role in determining TC predictability.

Inaccurate characterization of complex topography leads to the wet bias in climate models, particularly affecting terrain effects in regions like the Tibetan Plateau (TP). This study utilizes the Weather Research and Forecasting (WRF) model with multiple terrain datasets and introduces the terrain complexity index (TCI) to quantify the degree of terrain changes, aiming to evaluate how terrain complexity affects the cloud and precipitation processes over the TP. The results indicate that fine terrain complexity primarily causes earlier cloud formation and precipitation, resulting in more heavy precipitation on the southern slope of the TP (SSTP) and more light precipitation on the TP platform. The structure of moisture transport and microphysical processes further reveals that this promotes the formation of more medium and high clouds, increasing the proportion of solid precipitation over the SSTP. Over the TP platform, the restriction of medium and high cloud development with enhancing the proportion of low clouds for more liquid precipitation. These findings deepen the understanding of the TP’s complex terrain effect on cloud and precipitation changes in the Asian water cycle.

Accurately estimating particulate organic nitrate under high NO_x and oxidizing conditions is critical. This study compared the NO_x⁺ ratio, unconstrained Positive Matrix Factorization (PMF), and Multilinear Engine-2 (ME2) methods to estimate particulate organic nitrate in Shanghai across different seasons. The factors associated with organic nitrate, as identified through two receptor methods, exhibited consistent daily patterns in spring, summer, and autumn, although source contributions varied. The NO_x⁺ ratio method reported higher organic nitrate levels than the PMF and ME2 methods, likely due to the fixed R_ON/R_AN parameter. Seasonal R_ON/R_AN parameters were optimized based on precursor emissions in Shanghai, achieving values of 3.13 in spring, 2.25 in summer, and 1.88 in autumn. This optimization reduced discrepancies in organic nitrate using the NO_x⁺ ratio to 3.2–7.4%. The optimized parameters in this study support the rapid and accurate estimation of organic nitrate during different seasons in urban areas.