South America experiences recurrent precipitation variability and hydroclimatic anomalies, yet two questions remain unresolved: whether joint climate-mode states add information beyond individual-mode effects and how predictably their associated regional anomalies can be recovered out of sample. This study assesses precipitation anomalies across the Amazon Region (AR), Northeast Brazil (NB), and southern Brazil and the La Plata basin (SL) using Global Precipitation Climatology Centre (GPCC) Full Data Daily precipitation for 1982–2020. Individual phases of the El Niño–Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), Southern Annular Mode/Antarctic Oscillation (SAM/AAO), and Tropical North Atlantic/Tropical South Atlantic (TNA/TSA) are compared with pairwise combined regimes using block-bootstrap confidence intervals and false-discovery-rate (FDR) correction; continuous seasonal-year regressions separate main effects from interaction terms. Random Forest and XGBoost are evaluated through climate-year-grouped out-of-fold (OOF) validation, mode ablation, and OOF SHapley Additive exPlanations (SHAP). Five of 18 ENSO regional phase–season composites are FDR-significant, compared with two of 54 secondary-mode composites. Selected combined regimes reach approximately − 35
Mesoscale convective systems (MCSs) frequently propagate from China’s second-step terrain to North China Plain (NCP), yet the regime dependence of their spatiotemporal characteristics and the controlling environments remains insufficiently understood. Using Himawari-8/9 brightness temperature data and an iterative tracking approach, this study identified warm-season mountain-to-plain MCSs (MP-MCSs) over North China during 2016–2023. K-means clustering separates these MP-MCSs into four major categories: short-distance northeastward/southeastward moving (Short-NE/Short-SE) and long-distance northeastward/southeastward moving (Long-NE/Long-SE) MP-MCSs. Short-distance MP-MCSs initiate mainly over the Taihang–Yanshan region and occur most frequently during the monsoon season, producing rainfall maxima along the slopes and adjacent plains. Long-distance MP-MCSs originate farther upstream and are more common during seasonal transition periods, with rainfall concentrated over western mountainous regions. All four categories exhibit enhanced frequencies of intense hourly precipitation over the plains. Short-SE systems are the most convectively intense but spatially compact and slow moving, whereas Long-NE systems are the least intense, have the broadest cloud shields, and move the fastest. The diurnal rainfall evolution also differs systematically by propagation direction and significantly terrain-dependent. NE-moving systems peak from late-afternoon to evening over the eastern Taihang slopes and adjacent foothills, whereas SE-moving systems, especially Short-SE, display a pronounced mountain-to-plain phase delay, with afternoon rainfall over high terrain and nocturnal rainfall over foothills and plains. Composite environments indicate that the four regimes are favored by baroclinic waves, local thermodynamic and topographic forcing, midlatitude troughs, and cold-vortex-related northwesterly flow, respectively. These results refine the regime-based understanding of MP-MCS propagation and heavy-rainfall risk over North China.
Using cutting-edge coupled climate models from the CMIP6 archives, this study seeks to comprehend the mean atmospheric structure of tropical and extratropical circulations over High Mountain Asia (HMA) under future socioeconomic scenarios and to look into how the seasonal precipitation over the HMA gets affected by global teleconnection changes. Our results indicate reasonably good performance of historical simulations of CMIP6 models over the HMA region with respect to the ERA5 datasets. MMM (multi-model mean) is used to evaluate the changes in meteorological parameters under two shared socio-economic pathways (SSP2-4.5 and SSP5-8.5) compared with the historical simulations over the HMA region. Both the future climate projections show a significant decline in winter precipitation over the southern part of HMA whereas the Hindu Kush and Pamir regions show an increase. The non-parametric K-S test demonstrates that models show unequivocal changes in meteorological parameters over several parts of HMA. To comprehend global teleconnections instigating noticeable changes under various SSP scenarios, the NAO and ENSO indices are estimated. This study devises ENSO and NAO indices for future climate projections and deals with the usefulness of CMIP6 models to investigate global teleconnections under future climate projections. The results point to the noteworthy changes in the atmospheric circulation patterns across the HMA region in association with NAO and ENSO. The results show a weakening of sub-tropical jet stream for negative NAO phases under SSP5-8.5 and all-over decreasing influence of ENSO on the precipitation patterns is also perceptible.
Understanding and forecasting drought dynamics play a vital role in mitigating and controlling drought-related disasters. Unlike previous studies focusing primarily on drought propagation time, this study establishes a nationwide multitype framework to quantify future propagation thresholds among meteorological, soil, and hydrological droughts and their associated drought resistance capacity under CMIP6 climate scenarios. In this study, the characteristics and propagation changes of different drought types (meteorological drought (MD), hydrological drought (HD), and soil drought (SD)) in China were systematically evaluated under two shared socioeconomic pathway (SSP2-4.5 and SSP5-8.5) scenarios on the basis of multimodel ensemble (MME)-simulated precipitation, runoff, evapotranspiration, and soil moisture data from Phase 6 of the Coupled Model Intercomparison Project (CMIP6). The propagation thresholds among the different drought types in the future were determined. The investigation shows that (1) MD and HD will increase in most areas of China, and SD will decrease in some areas. (2) Compared with those during the historical period, the duration and severity of MD, SD and HD under the different future scenarios will noticeably increase, remain unchanged, and noticeably decrease, respectively. (3) In the future, the propagation thresholds from MD to HD will increase in most areas of China, with the regional mean duration- and severity-based thresholds increasing by approximately 51.9–70.2
Despite rapid global warming, the persistent and occasionally intensifying winter extreme cold events (ECEs) in the Northern Hemisphere (NH) pose a profound scientific paradox and severe socioeconomic challenges. However, the extent to which the long-term trends of these ECEs diverge across varying intensities, and the specific physical mechanisms driving such disparities, remain poorly understood. Using ERA5 reanalysis data from 1940 to 2023, this study employs Quantile Regression (QR) to systematically quantify the intensity-dependent trends of NH ECEs. Furthermore, we apply circulation composite analysis and a dynamical adjustment framework to uncover the key physical processes governing these trends. Our results reveal that while the total frequency of ECEs has significantly decreased, the annual frequency of strong ECEs exhibits a robust increasing trend. Consequently, the overall average intensity of ECEs has amplified, driven concurrently by the pronounced decline in weak ECEs and the increased occurrence of strong ECEs. By quantitatively separating the dynamical and thermodynamic components, we demonstrate that their contributions to ECE evolution differ fundamentally by intensity. For strong ECEs, the dynamical and thermodynamic components both contribute to the strengthening of cumulative cooling, but the dynamic component dominates, accounting for approximately 88
