International Journal of Climatology最新文献

Arctic warming has been substantially greater than that in the rest of the world and has had an important influence on the global climate. This study first explores the temporal and spatial evolutionary characteristics of marine heatwaves (MHWs) over the Arctic Ocean in multiyear ice (MYI), first-year ice (FYI), and open-water (OPW) regions from 1982 to 2020. MHWs in the Arctic Ocean show obvious spatial and seasonal variations, mainly occurring over the FYI region in the JAS (July–August–September, JAS), and their occurrences have a significant increasing trend in recent decades, accompanied by an abrupt increase since 2010. Furthermore, a multivariable network-based method is adopted to delineate the relationship between different climatic factors and MHWs in the Arctic Ocean and the climatic impacts of MHWs. The results show that the correlations between different climatic factors and MHWs in JAS in 2010–2020 are generally stronger than those in 1982–2009, and the main influencing factors of MHWs in different ice covers are different. MHWs in the MYI region are mainly affected by freshwater dilution processes, such as sea-ice concentrations (SIC), precipitation, and mixed-layer salinity. For the FYI region, the 2-m air temperature and total heat flux mainly affect MHWs by thermodynamic processes, and the 500-hPa geopotential height affects MHWs mainly by large-scale atmospheric circulation. The MHWs in the OPW region are mainly related to the SIC, 850-hPa geopotential height, and 10-m v-wind, indicating that they are correlated with atmospheric processes and wind fields. MHWs in JAS are also revealed to reduce or delay the formation of sea ice in OND (October–November–December, OND) by storing more abnormal heat, indicating that unfrozen ocean surfaces may lead to enhanced Arctic amplification in the following seasons.

Upper-level (200 hPa) velocity potential (VP200) is useful in identifying areas of rising or sinking atmospheric motions on varying temporal scales (e.g., weekly, seasonal, interannual) especially in the global tropics. These areas are associated with enhancement (rising motion) or suppression (sinking motion) of tropical convection and subsequent weather phenomena dependent on these processes (e.g., tropical cyclones). This study employed commonly used global weather reanalysis datasets to calculate and compare VP200 on interannual through multidecadal temporal scales and quantify any differences that existed between them from 1959 to 2020 over four key regions of tropical variability (Equatorial Africa, Amazon Basin, Equatorial Central Pacific, and Equatorial Indonesia). To supplement this analysis, the highly correlated variables to VP200 of outgoing longwave radiation (OLR) and daily precipitation rate were used and directly compared with independent OLR and precipitation datasets to determine the reanalysis' level of agreement with the independent data. The ECMWF ERA5 held the highest agreement to these data over all regions examined and was reasoned to have the highest confidence in accurately capturing the variability of VP200 fields for the study period. Confidence was decreased in the usefulness of the NCEP/NCAR Reanalysis 1 as it consistently performed poorly over much of the study domain. The results of this study also emphasised the usefulness in ensemble-based approaches to assess climate variability and understanding of potential biases and uncertainties that are inherent in these data sources.

Precipitation is the fundamental source for various research areas, including hydrology, climatology, geomorphology, and ecology, serving essential roles in modelling, distribution, and process analysis. However, the accuracy and precision of spatially distributed precipitation estimates is a critical issue, particularly for daily scale and topographically complex areas. Although many datasets have been developed based on different algorithms and sources are developed for this purpose, determining which of these datasets best reflects actual conditions is quite challenging. This study, hence, aims to compare the 25 global distributed precipitation estimates (gridded, satellite, model, and fused) concerning 221 ground-based observations based on the ranking of 18 continuous (evaluation statistics), eight categorical (precipitation indices), and two seasonality metric (high and low precipitation). Upon examining the results, gridded and model precipitation data including APHRODITE (Asian Precipitation—Highly-Resolved Observational Data Integration Towards Evaluation), CPC (Global Unified Gauge-Based Analysis of Daily Precipitation), ERA5-Land (ECMWF Reanalysis 5th Generation for Lands), and CFSR (Climate Forecast System Reanalysis) occupy the top four positions in continuous metrics. In contrast, satellite data such as PERSIANN-PDIR (Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks), CMORPH (Climate Prediction Center morphing method), IMERG (The Integrated Multi-Satellite Retrievals for GPM), and TRMM-TMPA (Tropical Rainfall Measuring Mission/Multi-satellite Precipitation Analysis) dominate in the top four positions in categorical metrics. For seasonality of high and low precipitation, fused, gridded, and reanalyses products such as CPC, MSWEP (Multi-Source Weighted-Ensemble Precipitation, version 2), HydroGFD (Hydrological Global Forcing Data), CFSR rank among top four. Based on the first five rankings of all metrics, fused (multiple sourced) and gridded datasets accurately reflect the actual situations compared to other precipitation products. Reanalysis (model) and satellite-based follow this rank, respectively. The results clearly indicate that fused precipitation derived products from multiple sources offer better accuracy and precision in representing the spatial distribution of precipitation on a daily scale.

In mountainous areas, accurately estimating the long-term climatology of seasonal precipitations is challenging due to the lack of high-altitude rain gauges and the complexity of the topography. This study addresses these challenges by interpolating seasonal precipitation data from 3189 rain gauges across France over the 1982–2018 period, using geographical coordinates, and altitude. In this study, an additional predictor is provided from simulations of a Convection-Permitting Regional Climate Model (CP-RCM). The simulations are averaged to obtain seasonal precipitation climatology, which helps capture the relationship between topography and long-term seasonal precipitation. Geostatistical and machine learning models are evaluated within a cross-validation framework to determine the most appropriate approach to generate seasonal precipitation reference fields. Results indicate that the best model uses a machine learning approach to interpolate the ratio between long-term seasonal precipitation from observations and CP-RCM simulations. This method successfully reproduces both the mean and variance of observed data, and slightly outperforms the best geostatistical model. Moreover, incorporating the CP-RCM outputs as an explanatory variable significantly improves interpolation accuracy and altitude extrapolation, especially when the rain gauge density is low. These results imply that the commonly used altitude-precipitation relationship may be insufficient to derive seasonal precipitation fields. The CP-RCM simulations, increasingly available worldwide, present an opportunity for improving precipitation interpolation, especially in sparse and complex topographical regions.

Accurate runoff projections are vital for developing climate adaptation strategies, yet significant uncertainties persist. The commonly employed approaches to constrain these uncertainties rely on the stationarity of climate biases and runoff sensitivity, which may not hold for climate-sensitive regions (e.g., semi-arid regions). This study investigates the validity of the stationarity assumption across 29 CMIP6 models, encompassing diverse climate biases (Dry Warm, Wet Warm, Dry Cold, and Wet Cold), utilising a semi-arid region in central India as a testbed. The implications of this assumption on runoff projection uncertainties were comprehensively assessed across the runoff modelling chain for three time periods (the 2030s, 2060s and 2090s) based on the Soil and Water Assessment Tool (SWAT) simulations. The results highlight the non-stationary nature of climate biases and runoff sensitivity under future scenarios, challenging the widespread applicability of common uncertainty-constraining approaches. Moreover, the impact of non-stationarity on runoff projection uncertainty was found to be strongly influenced by the choice of GCMs, preprocessing methods and climate change scenarios. In the 2030s, GCMs dominate runoff uncertainty, with dry models exhibiting ~10%–15% higher uncertainty compared to warm models, which is further amplified when interacting with warm biases. However, from the mid-century onwards, the bias-adjustment approaches and climate change scenarios significantly shape runoff projection uncertainties under non-stationary conditions. These findings emphasise the potential of climate bias and runoff sensitivity-based GCM selection for reducing runoff uncertainty in near-future assessment (2030s). For mid-term and long-term runoff projections, addressing diverse climate biases through bias-adjustment approaches is more viable. This study offers critical insights to prioritise the development of a non-stationarity-based approach for reliable runoff projections in climate-sensitive regions.

Vapour pressure deficit (VPD) is a critical measure of the atmospheric demand for water and can be used to assess short-term and seasonal drought. To provide for probabilistic comparisons of VPD across space and time, we develop a Standardized Vapor Pressure Deficit Index (SVPDI). Similar to the way that other standardised drought indices are used, SVPDI allows for the analysis and comparison of changes in VPD across regions with different base level VPD values. It also should be useful for analysing impacts on vegetation that has varying levels of adaptation to high VPD. We use 1-, 3-, 6- and 12-month timescales for the development of SVPDI and show that the gamma distribution is superior to other zero-limited probability distributions for analysing VPD and, therefore, for calculating SVPDI. Then, focusing on the short-term variations at the 1- and 3-month timescales, we show how SVPDI has changed globally from 1958 to 2023 and how those changes differ from those of the commonly used Standardized Precipitation Evaporation Index (SPEI). We find that SVPDI shows more widespread drying conditions that also are larger in magnitude compared to those of SPEI. Although the two indices are moderately well correlated across the terrestrial surface, we discover that they are more decoupled in humid and arid regions compared to dry sub-humid and semi-arid regions. Using four locations that have recently experienced severe drought, we find that SVPDI generally showed longer drought duration and more severe drought events in the last decade when compared to SPEI.