International Journal of Climatology最新文献

In the North China Plain (NCP), the assessment of water surplus or deficit (WSD), which is calculated as precipitation minus reference evapotranspiration (ET₀), holds significant implications for water resource management and agricultural irrigation decision-making, given the region's long-standing severe shortage of water resources. However, the magnitude, trend and climatic drivers of WSD remain poorly understood in the NCP. This study analysed the spatial and temporal characteristics of WSD, and quantified the contribution of climatic factors to WSD based on the sensitivity and contribution rate analysis methods with climatic data from 75 meteorological stations. The result showed that: (1) Annual WSD decreased mainly in northeastern NCP and increased significantly in southern NCP during 1961–2022. Annual WSD increased slightly from 1961 to 2022 at a rate of 1.63 mm a⁻² mainly due to the more significant decrease (−1.88 mm a⁻²) in ET₀ compared to precipitation (−0.25 mm a⁻²). (2) In terms of the sensitivity of WSD to climatic factors, relative humidity had the highest sensitivity, followed by net radiation, wind speed, precipitation and average air temperature. (3) Significant declines of wind speed were the most dominant factor affecting WSD variation in most part of NCP during most of a year, and net radiation of four stations in the western high-elevation regions played the most important role. This study enhances comprehension of the impact of climate change on WSD in the NCP and provides a reference for improving management of agricultural water resources under NCP's evolving climatic conditions.

The spatial and temporal variations of cumulonimbus clouds (Cbs) that produce lightning have mesoscale characteristics due to the nature of Cbs and the influence of topography; however, previous studies have lacked a mesoscale perspective because historical lightning observations relied on human observation. In this study, mesoscale variations in the number of thunder days (TDs) over the Japanese Archipelago over a 56-year period were investigated using manned observation data (Period 1: 1954–1963) and radio-wave observation data (Period 2: 2010–2019). A comparison of the two periods of Period 1 and Period 2 revealed that the locations of mesoscale areas with high TDs did not change significantly; however, the number of TDs increased in most mesoscale areas and it was not possible to identify any mesoscale areas with a significant decreasing trend. The characteristics of mesoscale variation varied with the season as follows: (1) Winter (November–January): the number of TDs along the coastal lands of the Sea of Japan increased significantly. The variations in the synoptic-scale winter pressure pattern with low stability were one of the factors contributing to the increasing trend of TDs. (2) In the first half of the Baiu season (June), the number of TDs increased in two regions: one region was the south of Japan associated with the Baiu front, while the second region was the northern area of Japan, where the influence of the Baiu front is limited. (3) Summer (August): the number of TDs in mountainous areas tended to increase significantly, and the variation in the water vapour content was significantly correlated with the variation in the number of TDs. The number of TDs in the foothills did not increase significantly. (4) Akisame season (September): the number of TDs along the Pacific Ocean coast significantly increased.

Meteorological droughts in Malaysia have significantly impacted critical sectors such as agriculture, water resources, health, the environment, tourism and various socio-economic sectors, affecting the population's livelihood and well-being. This study analyses drought characteristics over a 39-year period, from 1982 to 2021, using the Standardised Precipitation Index (SPI) derived from 5-km resolution Climate Hazards Group InfraRed Precipitation with Station data (CHIRPS). The droughts were assessed on 3-, 6-, 9- and 12-month timescales to investigate spatio-temporal variations in characteristics such as frequency, duration, peak, severity and intensity. The study also provides an in-depth analysis of large-scale drought modulation, particularly associated with the El Niño phenomenon and its teleconnection in the Maritime Continent. Depending on the location and timescale, the number of meteorological drought occurrences varied from 10 to 22 for the 3-month timescale and 4 to 14 for the 12-month timescale. Generally, as the timescale of a drought increases, the peak intensity decreases, while the duration and severity increase. Additionally, drought intensity decreases over longer timescales. These characteristics show significant spatial variations. Results indicate that meteorological droughts in Malaysia were almost entirely modulated by the El Niño phenomenon through its induced teleconnection over the Maritime Continent. Drought characteristics exhibit a strong seasonality linked to changes in the Walker circulation and the strengthening and weakening of anticyclonic circulations associated with Rossby waves induced by heating in the Pacific Ocean. Very strong El Niño events had the most significant influence on the droughts. The positive Indian Ocean Dipole (pIOD) strengthened the effects of El Niño but it itself had no significant influence on the droughts. In most regions, there were no significant trends in the characteristics of meteorological droughts. However, in northeast Peninsular Malaysia and some scattered areas along the west coast of the peninsula, significant trends are observed in peak, duration and severity.

This work studies the simultaneous and sequential occurrence of hot and dry months in the summer season in Argentina, north of 40°S, based on three different databases: meteorological stations, a gridded observational dataset and a reanalysis product. The influence of the El Niño-Southern Oscillation (ENSO) over the occurrence of these compound events is specially analysed using a logistic regression model. Monthly maximum temperature and precipitation data are used for the period 1979–2022 in four sub-regions of Argentina: Northwestern Argentina (NOA), Northeastern Argentina (NEA), Cuyo (central-western Argentina) and the Pampas (central-eastern Argentina). Simultaneous hot and dry months and hot months preceded by dry months are the most frequent compound events. The highest frequencies are found in the centre part of the study region and NEA for simultaneous compound events, and in NOA and the Pampas region for sequential ones. In general terms, all datasets show a good representation of the spatio-temporal variability of hot and dry months. The insights of the influence of ENSO on compound events revealed that La Niña enhances the occurrences of hot and dry months throughout the study region, with the exception of NOA, where El Niño conditions promote the occurrence of these events. Based on logistic regression models, we successfully quantify the relationship between ENSO and hot and dry months and demonstrate that ENSO plays a significant role as a driver of compound hot and dry events in the central region, Cuyo, NEA and a portion of the Pampas. This research contributes to the understanding of compound events in Argentina and how they are influenced by major drivers of climate variability providing useful information for the development of a predictive system for such events.

Impacts of El Niño−Southern Oscillation (ENSO) on the quasi-biweekly oscillation over the western North Pacific (WNP-QBWO) in boreal winter are investigated in the study. The WNP-QBWO in boreal winter primarily propagates westward from the tropical western Pacific to WNP. During the La Niña winter, the QBWO over the WNP has stronger intensity and propagates westward at a faster speed, while it is weaker and propagates more slowly during the El Niño winter. The possible mechanisms may involve the ENSO-related background moisture and zonal wind vertical shear changes that can significantly modulate the WNP-QBWO's behaviours in boreal winter. A 2.5-layer atmospheric model is applied in the study and confirms the results. It is further revealed that the moisture change is dominant in modulating the WNP-QBWO's intensity, while both the moisture and vertical shear changes may together contribute to the zonally propagating speed of the WNP-QBWO in boreal winter. These results can deepen our understanding of dynamic processes associated with the WNP-QBWO in boreal winter and are conducive to the predictability study.

The North American summer monsoon (NASM) and the North African summer monsoon (NAFSM) are two vital subsystems of the global monsoon. To date, the potential inter-monsoon relationship between the NASM and NAFSM has not been fully understood. To fill this gap, we investigate the NASM–NAFSM relationship on the interannual timescale during the period of 1979–2022. Based on statistical methods (including correlation, empirical orthogonal function and cross wavelet analyses), we identify a noteworthy interannual covariation of the NASM and NAFSM. This observed NASM–NAFSM covariation can be explained by atmospheric circulation anomalies associated with sea surface temperature (SST) anomalies in the tropical central-eastern Pacific and tropical Atlantic, suggesting the critical roles of tropical Pacific–Atlantic SST anomalies in shaping the NASM–NAFSM covariation. The results of Coupled Model Intercomparison Project Phase 6 (CMIP6) models indicate that a model's ability to simulate the NASM–NAFSM covariation tends to be related to its ability to reproduce the modulating effects of the tropical Pacific–Atlantic SST anomalies. These results have potential implications for seasonal forecasts of the NASM and NAFSM variations, suggesting that the NASM and NAFSM can be considered simultaneously in climate predictions.

Understanding the hydrological impacts of climate change is essential for robust and sustainable water management. This study assessed the hydrologic conditions under changing climate in the Jinshajiang River basin, the source region of the Yangtze River, using the hydrological model SWAT with the historical observations and the future climate simulations under two Shared Socioeconomic Pathways (SSP2-4.5 and SSP5-8.5). For the historical period, with an increasing trend of precipitation, evapotranspiration, and snowmelt, streamflow increases in upstream region but keeps decreasing in the downstream catchment. For future scenarios, a warmer and wetter climate is projected for the basin throughout the 21st century, leading to an overall increase in mean and extreme streamflow. The streamflow magnitude increases more significantly in the far future than in the near future, and more significant under SSP5-8.5 than SSP2-4.5. The projected remarkable increase in precipitation causes the transition in changing trend of streamflow compared with the historical period. The projected warming leads to a continuing decline in snowfall and snow water equivalent, followed by an earlier snowmelt and higher peak streamflow, especially at the upstream catchment. Ultimately, reservoirs in the basin are expected to gain more inflows, however, with greater variability including higher likelihoods of flood and drought events, which impose potential challenges on reservoir operations. These outcomes indicate the importance of adaptive water resources management in the melting water contributed basin to sustain and enhance its services under global warming.

In this study, the characteristics of tropical cyclones (TCs) over the Bay of Bengal (BoB) that affect snowfall on the Tibetan Plateau (TP) and spatiotemporal distribution of snowfall related to BoB TCs are statistically analysed by using multi-sources data from 1981 to 2020, with partitioning TC-influenced snowfall by tracking cloud clusters. The results show that 141 TCs formed during the 40-year period of 1981–2020, of which about 35% (50 TCs) impacted snowfall at 83% of meteorological stations on the TP during their northward or westward movement, and the average distance between the TC centre and the snowfall stations is 1277 km. The proportion of snowfall-related TC frequency shows a significantly decreasing trend with a predominant cycle of 10a. The TC-influenced snowfall frequency (SF), precipitation amount (PA) on a snowfall day and snow depth (SD) during 1981–2020 all show a non-significant weak decreasing trend, while TC-influenced snowfall is significantly increased in the eastern and southern edges of Xizang, western Sichuan and the southern margin of Qinghai. PA and SD in December account for more than 75% and 55% of the monthly total, respectively. The spatial pattern of PA could be objectively categorised into west-type (24%) and southeast-type (76%). The moisture transported by the BoB TC and a southerly jet stream formed between the trough and the western Pacific subtropical high (WPSH), the convergence of cold air and warm–moist airstream over the TP and the change in position of the south Asian high in the upper troposphere are significant factors causing the different spatial distribution. The results can provide reference for TC-related snowfall, SD prediction and disaster assessment on the TP.