International Journal of Climatology最新文献

Changes in patterns of accumulated rainfall, as well as the rainy season onset, cessation and duration, can impact the availability of water resources and sectors such as agriculture, affecting the livelihoods of the population. The knowledge of these changes is crucial for regions driven by strong precipitation variability such as the Andean countries. Therefore, the aim of this work is to determine the present and future spatio-temporal patterns of the onset, cessation and duration of the rainy season in Peru. For this purpose, we analysed in a first step the present variability and trends in 11 homogeneous regions using data from 377 ground stations for the period 1981–2019. The results showed significant trends (1981–2019) of earlier onset and increased duration only in the Southern Peruvian Amazon (Madre de Dios River basin). Furthermore, the accumulated rainfall has significant trends of increases in North East Andes, Northern and Southern Amazon. In a second step, we assessed future changes of the rainy season from an ensemble of statistically downscaled CMIP6 climate scenarios. A two-tailed Student t-test was used to evaluate the significance of changes. Two future time slices (2031–2060 and 2071–2100) relative to the reference period (1981–2010) were analysed. Future changes of the rainy season showed significant delays in the onset for the Central East Andes, South West Andes and Amazon regions in the period 2071–2100. Likewise, the rainy season duration presents future significant reductions in regions of the central and southern Andes under the SSP2-4.5 scenario. Moreover, the accumulated precipitation is projected to increase significantly in the Pacific slope and Andes regions, mainly under the SSP5-8.5 scenario. These findings are particularly important for sectors like agriculture, energy and water resources management.

Global warming by human activities have exacerbated the occurrence of extreme climatic events, which have taken a huge toll on human production and livelihoods. Predicting future changes in extreme wetness and dryness, along with the extent of cropland exposure to these conditions under various scenarios, is essential for effective climate adaptation and achieving sustainable development goals. This study employs the Standardised Antecedent Precipitation Evapotranspiration Index (SAPEI) method to identify extreme dryness and extreme wetness in China for future projections (2021–2100), and to analyse the characteristics of changes in the pixel-day, intensity, and affected area by extreme dryness and wetness, as well as the cropland exposures to them under different shared socioeconomic pathways (SSPs). We find that the intensity and spatial extent of extreme dryness and wetness significantly increase in future climate projections, especially under high-emission scenario compared to low-emission scenario. Under the scenarios with increased emissions, the cropland exposure increased in most parts of China. Therefore, it is particularly urgent to keep the low-emission scenario in order to minimise the cropland damage caused by extreme drought and wetness in China in the future.

Several classical and innovative trend methods exist in the literature to identify and evaluate the effects of climate change on hydro-meteorological variables. Among the classical methods, the most commonly used ones are modified Mann–Kendall (MMK) and Sen's slope (SS). As for the innovative methods to identify potential trends (probable risk levels) in hydro-meteorological variables depending on changing the initial conditions and temporal dynamic development behaviour of the trends, the risk Sen's slope (RSS) method was proposed based on different risk values. The actual trends are proposed in this research to comprehensively understand and analyse the climate change trend over the entire period. It uses RSS and the classical trends MMK and SS. Also, the spatiotemporal classical, actual and potential trends in meteorological variables are evaluated. Additionally, the advantages of the RSS method compared with classical SS are discussed in detail. The Western Black Sea basin in Türkiye, with monthly total precipitation and monthly average temperature data from 1961 to 2023, is selected as a representative application. The temperature trend results show that the 0.99 risk level gave approximately 25% higher slope than SS. The maximum temperature-increasing trend within the study area and the time period at 0.99 risk level is 2.10°C. However, the differences between precipitation trend slopes obtained by SS and RSS for different risk levels are relatively low. Furthermore, using different slopes corresponding to several risk levels allows for more proactive and effective measures for sustainable agricultural activities and water management. The actual temperature trend within the basin ranges between 1.33°C and 2.09°C, and the actual precipitation trend ranges between 2.78 and 12.74 mm over the study period.

Warm fronts often trigger significant weather changes, which also play a role in many extreme weather incidents. Therefore, it is crucial to understand the location and characteristics of warm fronts to accurately forecast weather changes. However, warm fronts are more difficult to identify than cold fronts on average, since the gradients can be weaker and shallower. This paper proposes a new objective method for identifying warm fronts in the Eurasia region using ERA-5 hourly reanalysis data. The method uses the appropriate thermal front parameter and warm advection threshold to identify the potential warm frontal zone, then determines the corresponding warm boundary according to the predominant wind direction within the frontal zone, and finally locates the warm front line along the warm boundary. In various weather processes, the location and shape of the objective warm front correspond well with the distribution of weather systems and meteorological elements, indicating the effectiveness of the method. Meanwhile, the high agreement between objective and manual warm fronts further supports the reliability of the method. Furthermore, this method is applied to the long-term datasets covering Eurasia, enabling an exploration of the climatological characteristics of warm fronts in the region. The study reveals distinct seasonal patterns in warm front frequency, with the highest frequency occurring during winter and the lowest during summer. Warm fronts are notably active in Europe, the Siberian Plain, the Northeast China Plain extending to the Western Pacific during winter, spring, and autumn. The dataset of warm fronts produced by this method proves valuable for climate change research.

Precipitation concentration represents the temporal unevenness of precipitation over a given period. A higher concentration increases the likelihood of concurrent flooding and drought. While previous studies have primarily focused on precipitation concentration at the daily scale, research on sub-daily scales remains limited. Furthermore, the impact of temperature on precipitation concentration across various temporal scales is not well understood. In this study, we utilise high-resolution precipitation products and the Gini index (GI) to examine the spatiotemporal characteristics of precipitation concentration across four different time scales (3, 6, 12-h and 1-day) over China. The climatological analysis reveals a gradual increase in precipitation concentration from southeast to northwest China. At shorter temporal scales (3 and 6-h), Southeastern China exhibits a notable increase in precipitation concentration, while longer scales (12-h and 1-day) show a significant decrease throughout most regions of Northwest China. These observed spatiotemporal patterns are closely linked to temperature variations. At the 3-h scale, precipitation concentration at the 3-h scale increases with temperature at a nation-averaged rate of 1.06% °C⁻¹ and decreases to 0.30% °C⁻¹ at the 1-day scale. Higher temperatures intensify precipitation concentration at the 3-h scale in Southeast China by increasing the frequency of heavy precipitation events. Meanwhile, in Northwest China, the decline in concentration at the daily scale under warmer conditions is attributed to increased annual precipitation amounts driven by higher temperatures. This study is of great significance, as it provides insight into how the temporal distribution of precipitation in China change under future global warming.

Rapid expansion (RE) of tropical cyclones (TCs) is a structural evolution that specifies the dramatic geometric synthesis increase in TC size. Its destructive potential is comparable or even more pronounced than that by the TC rapid intensification but receives limited attention. In this study, we utilise the ERA5-derived 41-year (1979–2019) global climatology of TC outer size data (i.e., effective azimuthal-area-average radius of 34-kt gale-force surface winds, R34_EFF) to define RE and reveal the global climatology of RE for the first time, where RE is defined as the 90th percentile of global expanding samples (i.e., ΔR34_EFF > 50 NM per 24 h; 1 NM = 1.852 km). Statistics show that 32% of all TCs underwent RE at least once during their lifetime. Climatologically, the proportion of RE decreased significantly in the globe (7%) and Northern Hemisphere (9%), particularly in the western North Pacific (8%). Seasonally, the RE proportion peaks in the early and late TC seasons. Spatiotemporally, distinct spatiotemporal variations and interdecadal changes of RE are found. In view of TC lifecycle, TCs likely reach their lifetime maximum intensity and lifetime maximum size after RE initiation. The duration of RE varies widely from basin to basin, while its seasonal variability is relatively smaller. Regarding the relationship between RE and TC intensity, the intensity of rapidly expanding TCs may increase or decrease with the former being more likely. The initial size and intensity of rapidly expanding TCs tend to be small (45 NM) and weak (60 kt), respectively. This study advances the understanding of RE from a global perspective, laying important groundwork for future study.

This study investigates the projected changes in the diurnal temperature range (DTR) over India and explains its considerable spatial heterogeneity from a 20-km resolution coupled regional climate model (RSM-ROMS) integration. The RSM-ROMS is driven at the lateral boundaries by the Community Climate System Model version 4 (CCSM4) model. Observations reveal spatial heterogeneity in DTR trends with significant declining trends at many grid points interspersed with areas of either increasing or insignificant trends of DTR during each of the four seasons. The present-day simulations from RSM-ROMS show reasonable skill in simulating the daily maximum temperature (Tmax) and minimum temperature (Tmin) over India. Our results show a significant decrease in DTR over the Gangetic Plains in boreal winter and fall seasons and over southeastern India during boreal summer in the projected mid-21st century climate under the RCP 8.5 emission scenario. The future reduction in DTR over Region-1 (over Bihar and the eastern regions of Uttar Pradesh) during December–February (−0.86°C) and over Region-3 (over the rain shadow regions of Peninsular India) during June–September (−0.49°C) is attributed to large changes in surface radiative fluxes, with some of the decrease in downward short wave flux attributed to an increase in high cloud cover at the time of Tmax while there is a considerable increase in downward longwave flux in the mid-21st century climate. The enthalpy fluxes at the time of Tmax also act to reduce the rate of its warming. As a result, the warming rate of Tmax is less compared with the corresponding warming rate of Tmin, which leads to a reduction of the DTR in some regions that display a significant reduction in future climate. In contrast, Region-2 (over Rajasthan) and Region-4 (over northeast India) exhibit insignificant DTR changes in the mid-21st century climate for lack of asymmetrical changes in Tmin and Tmax.

The Indo-Pacific warm pool (IPWP), enclosed by a 28°C isotherm, is vital in controlling atmospheric circulations affecting monsoonal flow. The warming trend of sea surface temperatures (SSTs) over the IPWP has expanded the IPWP region. This study examines the impact of the IPWP warming on the Indian summer monsoon rainfall (ISMR) patterns using ERA5 reanalysis and India Meteorological Department rainfall records based on station data from 1959 to 2021. Analyses based on correlation, regression and composite anomalies show the complex relationship between recent decades of IPWP expansion/warming and monsoon circulation. However, the effects of regional IPWP SST warming changes on the ISMR pattern remain unexplored. Here, we explore the changes in the monsoonal circulation owing to the warming and expansion of IPWP, by comparing two equal periods (1959–1989 and 1990–2021). The responses of monsoons to IPWP warming in these two periods revealed some interesting facts, but the complexity remained. Further, we examined the composite impacts of IPWP SST warming in three categories, that is, very cool, usual and extremely warm, on the dynamics of monsoon circulations. The very cool IPWP is associated with the dry monsoon, while the extremely warm IPWP produces copious rainfall over southern India and dryness over eastern north India. The study confirms the non-linear relationship between IPWP warming and ISMR, which has been investigated in detail.