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International Journal of Climatology
John Wiley & Sons Ltd.
International Journal of Climatology

John Wiley & Sons Ltd.

0899-8418

International Journal of Climatology/Journal International Journal of ClimatologySCIAHCIEIISTP
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    Possible impacts of spring subtropical Indian Ocean Dipole on the summer tropical cyclone genesis frequency over the western North Pacific

    Qun ZhouRunyu Zhang
    10页
    查看更多>>摘要：Abstract The linkage between the spring subtropical Indian Ocean Dipole (SIOD) events and tropical cyclone genesis frequency over the western North Pacific (WNP) in the following summer is investigated in this study. It is found that their correlation is positive and statistically significant with a greater number of TCs genesis over the WNP in summer of a positive SIOD year. After removing the ENSO effects, diagnostic analysis reveals that under positive SIOD conditions the summertime WNP monsoon trough becomes intensified. Correspondingly, there are enhanced lower‐level vorticity, reduced vertical zonal wind shear, increased middle‐level relative humidity and vertical velocity over the WNP, conductive to generation of more TCs. Further examination indicates that the Mascarene high and Australian high are strengthened successively from spring to subsequent summer in a positive SIOD year, contributing to the maintenance of SIOD‐related SST dipole anomalies in southern Indian Ocean due to SST–wind–evaporation feedback mechanism. The resulting cyclonic anomaly is formed at lower troposphere over the WNP induced by the prominently enhanced cross‐equator airflows and the related Ekman upwelling. At upper troposphere, there tend to be remarkably WNP divergence anomalies of the interhemispheric vertical circulation forced by the summertime SST patterns closely associated with positive SIOD cases. By contrast, the monsoon trough is weakened and the dynamic and thermodynamic conditions are unfavourable for the WNP TC genesis in summer of a negative SIOD year, in agreement with a lower‐level anticyclonic anomaly and suppressed deep convection over the WNP forced by the SIOD‐related SST anomalies.
      原文链接:
    • NSTL
    • Wiley

    Extension and application of an observation‐based local climate index aimed to anticipate the impact of El Ni?o–Southern Oscillation events on Colombia

    Juan‐Manuel SayolLaura M. VásquezJorge L. ValenciaJean R. Linero‐Cueto...
    27页
    查看更多>>摘要：Abstract The Tumaco multivariate index (TMI) is a multidecadal monthly index constructed with unique time series of sea surface temperature, surface air temperature and rain measured at Tumaco bay, in the southern Pacific coast of Colombia, and available since 1961. In this work, this index is re‐evaluated after the addition of in situ sea level data, and its properties for different standardization periods are compared against oceanic El Ni?o–Southern Oscillation (ENSO) and other derived indices. In particular, we propose a modified TMI, hereinafter referred as TMI4, whose potential to identify the expected sign and the amount of future variations of rain induced by ENSO events in Colombia is analysed for selected extreme episodes. Results indicate that after the inclusion of sea level data, TMI4 can anticipate the development of El Ni?o events before the ENSO 3 and some other sea surface temperature‐based regional indices, although its predictability depends on the ENSO type (canonical or Modoki). The explanation is that sea level includes new information into TMI4 on the onset of El Ni?o events. In particular, the signal of intraseasonal sea level anomalies carried by downwelling Kelvin waves is detected at Tumaco tide‐gauge. Moreover, the analysis of the differences, both in magnitude and spatial distribution, of rainfall anomalies induced by positive (El Ni?o) and negative (La Ni?a) ENSO events characterized by TMI4 are regionally presented. As a result, we find that TMI4 is especially suited for extensive northern and western areas of mainland Colombia. For completeness, in the appendix we briefly introduce the semi‐automated implementation of TMI4, including a visual interface, which is currently being tested by personnel within the operational oceanography area at Centro de Investigaciones Oceanográficas e Hidrográficas del Pacífico (Dimar‐CCCP).
      原文链接:
    • NSTL
    • Wiley

    Accelerated exacerbation of global extreme heatwaves under warming scenarios

    Qinmei HanShao SunZhao LiuWei Xu...
    12页
    查看更多>>摘要：Abstract It is generally believed that global warming drives an increase in heatwaves, but these changes vary regionally. Projected trends of heatwaves and comparisons between observed and projected heatwave trends are poorly understood. We selected multiple characteristics of global heatwave events, including indicators on heat‐related health impacts under historical and future scenarios from the NASA Earth Exchange/Global Daily Downscaled Projections (NEX‐GDDP) dataset. We quantified the trends in the frequency, intensity, duration and peak temperature of heatwave events and identified heatwave hotspots that respond dramatically to radiative forcing. Future simulations suggest a four‐fold increase in the duration of heatwaves by 2050s, spatially concentrated in central Africa, northern South America and Southeast Asia, and the maximum duration of single heatwave event will be up to 44?days under a high emission scenario. Accelerated increasing trends are also detected in intensity, total duration and temperature of heatwaves with up to 2‐fold, 8‐fold and 9‐fold larger than the trends of the baseline period under the high emission scenario. Considering socioeconomic exposure to extreme heatwaves, we identified some hotspot areas in western Europe, eastern North America and northern China that will face greater potential risks in the coming future and therefore need to urgently strengthen their adaptation capacity.
      原文链接:
    • NSTL
    • Wiley

    Historical droughts in Irish catchments 1767–2016

    Paul O'ConnorConor MurphyTom MatthewsRobert L. Wilby...
    25页
    查看更多>>摘要：Abstract Recent prolonged dry periods in summer 2018 and spring 2020 have reawakened interest in drought in Ireland, prompting questions regarding historical drought occurrence and potential long‐term risks. Employing 250?years of monthly precipitation and flow reconstructions, we investigate historical drought in Irish catchments evaluating the characteristics (number of events, duration, and deficits) of moderate, severe, and extreme droughts as well as the propagation of meteorological to hydrological drought. Using standardized indices, we identify three distinct catchment types. Cluster 1 catchments, located in the wetter northwest are characterized by small areas, low groundwater storage, and the highest frequency of hydrological drought relative to other catchments. Cluster 3 catchments, located in the drier east and southeast have larger areas, greater groundwater storage, the highest frequency of meteorological drought but the least hydrological droughts. However, once established, droughts in Cluster 3 tend to be more persistent with large accumulated deficits. Cluster 2 catchments, located in the southwest and west, are intermediate to Clusters 1 and 3, with hydrological droughts typically of shorter durations, reduced accumulated deficits but greater mean deficits. The most extreme droughts based on accumulated deficits across all catchments occurred in 1803–1806, 1854–1859, 1933–1935, 1944–1945, 1953–1954, and 1975–1977. Although not as severe, droughts in 1887–1888, 1891–1894, and 1971–1974 also appear as significant extremes. Changes in drought characteristics reveal a complex picture with the direction, magnitude, and significance of trends dependent on the accumulation period used to define drought, the period of record analysed, and the reference period used to standardize indices. Of particular note is a tendency towards shorter, more intense meteorological and hydrological droughts. Our findings offer important insight for drought and water management in Ireland given the paucity of extreme droughts in short observed river flow records.
      原文链接:
    • NSTL
    • Wiley

    Changes in extreme precipitation events in the Zambezi River basins based on CORDEX‐CORE models, Part II: Future projections under 1.5, 2.0, and 3.0°C global warming levels

    Sydney SamuelModise WistonKgakgamatso MphaleDieudonne Nsadisa Faka...
    20页
    查看更多>>摘要：Abstract This study examines the potential implications of 1.5, 2.0, and 3.0°C global warming levels (GWLs) on the austral summer (November–March) extreme precipitation indices over the Zambezi River basin (ZRB) relative to the control period (1971–2000). We computed extreme precipitation based on daily data from observations and the Coordinated Regional Downscaling Experiment (CORDEX)‐Coordinated Output for Regional Evaluations (CORE) multi‐model ensemble mean (ENSMean). First, we evaluated the performance of the CORDEX‐CORE ENSMean in simulating extreme precipitation based on six indices; the number of rainy days (RR1), simple daily intensity index (SDII), maximum consecutive wet days (CWD), maximum consecutive dry days (CDD), heavy precipitation days (R10), and very heavy precipitation days (R20). The results indicate that the CORDEX‐CORE ENSMean can simulate the spatial distributions of extreme precipitation over the ZRB. However, CORDEX‐CORE largely overestimates the magnitudes of RR1 and CWD. The projected changes show a decrease in RR1, CWD, and R10 under all GWLs, with a robust and pronounced decrease under 3.0°C GWL. In contrast, CDD and SDII are projected to increase under all GWLs, with a robust and pronounced increase in CDD under 3.0°C GWL. The regionally averaged changes show that the median values of CWD, RR1, and R10 (SDII and CDD) are projected to decrease (increase) under all GWLs over the ZRB and sub‐basins. The probability density function (PDF) shows negative (positive) shifts in the mean of CWD, RR1, and R10 (SDII and CDD) over the ZRB and sub‐basins under all GWLs. In contrast, R20 is projected to increase (decrease) over most of the western (eastern) ZRB under all GWLs. Assessing the implications of an additional 0.5 and 1.5°C (1.0°C) warming to 1.5°C (2.0°C) GWL shows that limiting GWL to 1.5°C would restrict the future exposure of the ZRB to extreme precipitation.
      原文链接:
    • NSTL
    • Wiley

    Summer hot extremes and antecedent drought conditions in Australia

    Patrícia PáscoaCélia M. GouveiaAna RussoAndreia F. S. Ribeiro...
    16页
    查看更多>>摘要：Abstract The compound occurrence of extreme weather and/or climate events can cause stronger negative impacts than the individual events, and its frequency is increasing in several regions of the world. In this work, the effect of antecedent drought conditions on hot extremes during the months of December–February in Australia was analysed for two periods (1979–2019 and 1950–2019). The standardized precipitation evapotranspiration index (SPEI) and the indices number of hot days (NHD) and number of hot nights (NHN) were used to assess drought and extreme temperature events. While the link between dry and heat events is more important in the north in February, in December and January it is strong in the east coast. When temporal lags of 1–3?months are considered, there is a strong correlation between SPEI and NHD/NHN for the concurrent month on most of the study area. For the previous 1–3?months, the area and the correlation values decreased, but consistent spatial patterns were obtained for each month, namely negative correlations on the southwest and southeast in December, and the east in February. Tropical areas showed large areas of correlation between SPEI and NHN, including for the previous 3?months, whereas temperate climates showed the smaller area of correlation with NHN, including at the concurrent month. Significant correlations obtained for lead times longer than 1?month, namely with night heat extremes, point to a predictive ability in several regions of Australia. Moreover, the correlation coefficients obtained using the more recent period (1979–2019) show similar spatial patterns, but with higher values than for the 1950–2019 period. The results highlight the prospect of an early prediction of hot summer extremes in regions affected by drought in spring.
      原文链接:
    • NSTL
    • Wiley

    Regional patterns of dry spell durations in Croatia

    Ksenija Cindri? KalinZoran Pasari?
    17页
    查看更多>>摘要：Abstract The spatiotemporal characteristics of mean and maximum dry spells (DSs) in Croatia were analysed through general climatology and the return values associated with different return periods. An analysis was performed across seven regions with different precipitation regimes comprising data from 131 meteorological stations for 1961–2015. Daily precipitation limits of 1, 5, and 10?mm were used to define dry days, and DSs were defined as consecutive series of dry days. Generalized extreme value (GEV) and generalized Pareto (GP) distributions were applied to the DS annual maxima (AM) and the peak over threshold (POT) series, respectively. The respective distribution parameter methodology and interpretation combined both frequentist and Bayesian approaches. The regional mean DS lengths clearly indicated a dominance of DS durations in easternmost Croatia during the cold season (mainly winter) and in the southern Adriatic during the warm season (mainly summer). Elsewhere, combined climatic influences were reflected, with the shortest DSs found in the highlands. This spatial pattern was more pronounced for DS5 and DS10, whereas differences in DS1 durations were not evident. Spatial DS distribution return values associated with various return periods obtained by the GEV and GP distributions followed the general DS climatology. The visual inspection of an appropriate threshold for GP‐POT modelling, using the GP parameter stability graphs and L‐moment ratio diagrams, indicated that the 75th percentile value was best for all three DS categories. Although the estimates obtained by the two methods could not be directly compared, the GP model generally found longer DS return values than those obtained by the GEV, particularly in the regions with long DS. This study provides a climatological basis for drought parameters and drought risk assessment in Croatia. Moreover, the results are relevant for adjacent regions, complementing and enriching the current DS characteristics knowledge in southeastern Europe.
      原文链接:
    • NSTL
    • Wiley

    Climatology and extreme cases of sea‐effect snowfall on the southern Baltic Sea coast

    Ewa BednorzBartosz CzerneckiArkadiusz M. Tomczyk
    15页
    查看更多>>摘要：Abstract Heavy snowfall events of possible sea‐effect origin, occurring on the southern Baltic Sea coast, are described in this study. The analysed region is not very snowy, with an average of 40?days with snow cover in the winter season and a mean maximum snow depth of 8–12?cm. Twenty‐five snowfall events were selected using the threshold of 20?cm/2?days (i.e., 20?cm of snow depth increase during 2?days), and the synoptic climatology, as well as triggering factors of their occurrence, were defined. The bipolar pattern of sea level pressure with a high‐pressure over Scandinavia and a low‐pressure system southward of it was identified as favourable for sea‐effect snowfall on the southern Baltic Sea coast. This pressure field, causing northeastern circulation in the lower troposphere, brings cold air masses over the relatively warm sea basin, and the negative anomalies of air temperature at 850?hPa geopotential level, amounting to ?9°C, encompass Scandinavia, as well as central and northeastern Europe. This makes the temperature difference between the air at the 850?hPa geopotential height and the sea surface exceeding 15°C. This large temperature difference establishes favourable conditions for convection in cold air masses, which become unstable while crossing over the warm sea. The formed clouds give snowfall in the coastal areas. In the further part of the study, three sea‐effect snowfall cases were chosen for detailed analysis, including atmospheric sounding, radar and satellite images, air parcel backward trajectories, and synoptic maps. They reveal high‐pressure wedges associated with low air temperature over Scandinavia and northern airflow over the Baltic Sea. The wind direction and the temperature of air masses are key components in the occurrence of sea‐effect snowfall, and global warming conditions seem to reduce the frequency of snow events over the Polish Baltic Sea coast.
      原文链接:
    • NSTL
    • Wiley

    Unravelling the backbone of climate networks from the analysis of collective dynamics and time reversal

    Leyla NaghipourMohammad Taghi AalamiVahid Nourani
    19页
    查看更多>>摘要：Abstract Many complex systems are characterized by interconnected units often difficult, or even impossible, to map through direct observations, while the dynamics of units is mostly easier to measure. The reconstruction of an unknown structure from the observed dynamics is a typical inverse problem in network‐based approaches to overcome such obstacles. However, this procedure is affected by the interplay between the structure and dynamics, as well as by the choice of the statistical method. In this study, collective behaviour of the Earth's climate system was investigated by focusing on three distinct climatological variables in monthly time step using a causality measure to separately construct climate networks through a robust statistical analysis. Multiplex network (MUX) was used to integrate the information obtained from collective dynamics and time reversal for better filtering spurious connectivity. In fact, the proposed approach mitigates undesired effects of pairwise statistical inference by adjusting for unphysical relationships in two layers of the constructed networks. The results indicate that the mere existence of statistical errors allowed by the hypothesis testing lead, inevitably, to reconstruct spurious connections in the null models even when the collective dynamics consists of white‐noise datasets from uncoupled units. The impact of spurious connections with the MUX dynamics is not remarkable to reconstruct the underlying plausible interactions; therefore, the concepts of MUX might be employed with the statistical analysis to unravel the backbone of climate networks. In this way that the inferred connections could distinguish highly connected regions for better understanding interconnected dynamical patterns, yielding deep insights into underlying physical interactions between the oceans and atmosphere. More specifically, edge directionality features provide a complementary tool for analysing topology of the networks with respect to the climatological variables, identifying relevant patterns in the climate system.
      原文链接:
    • NSTL
    • Wiley

    Comparing the performance of high‐resolution global precipitation products across topographic and climatic gradients of Central Asia

    Mayra Daniela Pe?a‐GuerreroAtabek UmirbekovLarisa TarasovaDaniel Müller...
    16页
    查看更多>>摘要：Abstract Accurate and reliable precipitation data with high spatial and temporal resolution are essential in studying climate variability, water resources management, and hydrological forecasting. A range of global precipitation data are available to this end, but how well these capture actual precipitation remains unknown, particularly for mountain regions where ground stations are sparse. We examined the performance of three global high‐resolution precipitation products for capturing precipitation over Central Asia, a hotspot of climate change, where reliable precipitation data are particularly scarce. Specifically, we evaluated MSWEP, CHIRPS, and GSMAP against independent gauging stations for the period 1985–2015. Our results show that MSWEP and CHIRPS outperformed GSMAP for wetter periods (i.e., winter and spring) and wetter locations (150–600?mm·year?1), lowlands, and mid‐altitudes (0–3,000?m), and regions dominated by winter and spring precipitation. MSWEP performed best in representing temporal precipitation dynamics and CHIRPS excelled in capturing the volume and distribution of precipitation. All precipitation products poorly estimated precipitation at higher elevations (>3,000?m), in drier areas (<150?mm), and in regions characterized by summer precipitation. All products accurately detected dry spells, but their performance decreased for wet spells with increasing precipitation intensity. In sum, we find that CHIRPS and MSWEP provide the most reliable high‐resolution precipitation estimates for Central Asia. However, the high spatial and temporal heterogeneity of the performance call for a careful selection of a suitable product for local applications considering the prevailing precipitation dynamics, climatic, and topographic conditions.
      原文链接:
    • NSTL
    • Wiley