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Journal of Climate
The dependency of extreme UK hourly rainfall on 62 temperature has been demonstrated to be consistent with CC scaling in observations 63 (Blenkinsop et al., 2015) and a high resolution, convection-permitting ... We note that it is in summer 722 when the highest hourly precipitation extremes occur in the UK (Blenkinsop et al., 2017; Chan et al., 2014a). ... The provenance and extensive quality control of the 258 observational dataset, which is comprised of ~1900 rain gauges are described in Blenkinsop et 259 al. (2017). ...doi:10.1175/jcli-d-17-0435.1 fatcat:y3q6pcp5gbbwllfvarmgdp76ka
Journal of Hydrology
Highlights: 11 • The frequency of extreme daily precipitation occurrence displays a distinctive non-12 uniform seasonal pattern 13 • The seasonal distribution is simulated with Generalized Additive Models 14 • A strong dependence on atmospheric driving conditions is replicated. 15 • Statistical simulations indicate a future shift toward more frequent autumnal extreme 16 precipitation. 17 Abstract 18 Floods pose multi-dimensional hazards to critical infrastructure and society and 19 thesedoi:10.1016/j.jhydrol.2016.03.038 fatcat:pvsyvzewmrgp5ncs257yrxtoji
more »... may increase under climate change. While flood conditions are dependent 20 on catchment type and soil conditions, seasonal precipitation extremes also play an 21 important role. The extreme precipitation events driving flood occurrence may arrive 22 non-uniformly in time. In addition, their seasonal and inter-annual patterns may also 23 cause sequences of several events and enhance likely flood responses. 24 Spatial and temporal patterns of extreme daily precipitation occurrence are 25 characterized across the UK. Extreme and very heavy daily precipitation is not uniformly 26 distributed throughout the year, but exhibits spatial differences, arising from the relative 27 proximity to the North Atlantic Ocean or North Sea. Periods of weeks or months are 28 identified during which extreme daily precipitation occurrences are most likely to occur, 29 with some regions of the UK displaying multimodal seasonality. 30 A Generalized Additive Model is employed to simulate extreme daily 31 precipitation occurrences over the UK from 1901-2010 and to allow robust statistical 32 testing of temporal changes in the seasonal distribution. Simulations show that 33 seasonality has the strongest correlation with intra-annual variations in extreme event 34 occurrence, while Sea Surface Temperature (SST) and Mean Sea Level Pressure (MSLP) 35 have the strongest correlation with inter-annual variations. The north and west of the UK 36 are dominated by MSLP in the mid-North Atlantic and the south and east are dominated 37 by local SST. 38 All regions now have a higher likelihood of autumnal extreme daily precipitation 39 than earlier in the twentieth century. This equates to extreme daily precipitation occurring 40 3 earlier in the autumn in the north and west, and later in the autumn in the south and east. 41 The change in timing is accompanied by increases in the probability of extreme daily 42 precipitation occurrences during the autumn, and in the number of days with a very high 43 probability of an extreme event. These results indicate a higher probability of several 44 extreme occurrences in succession and a potential increase in flooding. 45
The "Karakoram Vortex" (KV), hereafter also referred to as the "Western Tibetan Vortex" (WTV), has recently been recognized as a large-scale atmospheric circulation system related to warmer (cooler) near-surface and mid-lower troposphere temperatures above the Karakoram in the western Tibetan Plateau (TP). It is characterized by a deep, anti-cyclonic (cyclonic) wind anomaly associated with higher (lower) geopotential height in the troposphere, during winter and summer seasons. In this study, wedoi:10.1007/s00382-018-4118-2 fatcat:uym3srdpfbdq7fie44uyprdpxe
more »... further investigate the seasonality and basic features of the WTV in all four seasons, and explore its year-toyear variability and influence on regional climate. We find the WTV accounts for the majority of year-to-year circulation variability over the WTP as it can explain over 50% ( R 2 ⩾ 0.5 ) variance of the WTP circulation on multiple levels throughout the troposphere, which declines towards the eastern side of the TP in most seasons. The WTV is not only more (less) active but also has a bigger (smaller) domain area, with a deeper (shallower) structure, in winter and spring (summer and autumn). We find that the WTV is sensitive to both the location and intensity of the Subtropical Westerly Jet (SWJ), but the relationship is highly dependent on the climatological mean location of SWJ axes relative to the TP in different seasons. We also show that the WTV significantly modulates surface and stratospheric air temperatures, north-south precipitation patterns and total column ozone surrounding the western TP. As such, the WTV has important implications for the understanding of atmospheric, hydrological and glaciological variability over the TP.
Journal of Climate
Extreme short-duration rainfall can cause devastating flooding that puts lives, infrastructure, and natural ecosystems at risk. It is therefore essential to understand how this type of extreme rainfall will change in a warmer world. A significant barrier to answering this question is the lack of sub-daily rainfall data available at the global scale. To this end, a global sub-daily rainfall dataset based on gauged observations has been collated. The dataset is highly variable in its spatialdoi:10.1175/jcli-d-18-0143.1 fatcat:ztyd642rcjeexbron37lc7bhai
more »... age, record length, completeness and, in its raw form, quality. This presents significant difficulties for many types of analyses. The dataset currently comprises 23 687 gauges with an average record length of 13 years. Apart from a few exceptions, the earliest records begin in the 1950s. The Global Sub-Daily Rainfall Dataset (GSDR) has wide applications, including improving our understanding of the nature and drivers of sub-daily rainfall extremes, improving and validating of highresolution climate models, and developing a high-resolution gridded sub-daily rainfall dataset of indices.
1 Increasing precipitation extremes are one of the possible consequences of a warmer climate. 2 These may exceed the capacity of urban drainage systems and thus impact the urban environment. 3 Since short-duration precipitation events are primarily responsible for flooding in urban systems it is 4 important to assess the response of extreme precipitation at hourly (or sub-hourly) scales to a warming 5 climate. 6 This study aims to evaluate the projected changes in extreme rainfall events acrossdoi:10.1002/hyp.11421 fatcat:clxnn3kn7baiholpffsqass5pa
more »... the region of 7 Sicily (Italy) and, for two urban areas, to assess possible changes in Depth-Duration-Frequency 8 (DDF) curves. We used Regional Climate Model (RCM) outputs from EURO-CORDEX ensemble 9 simulations at a ~12 km spatial resolution, for the current period and two future horizons under the 10 Representative Concentration Pathways (RCPs) 8.5 scenario. Extreme events at the daily scale were 11 first investigated by comparing the quantiles estimated from raingauge observations and RCM 12 outputs. Secondly, we implemented a temporal downscaling approach to estimate rainfall for sub-13 daily durations from the modelled daily precipitation and, lastly, we analyzed future projections at 14 daily and sub-daily scales. A frequency distribution was fitted to annual maxima time series for the 15 sub-daily durations to derive the DDF curves for two future time horizons and the two urban areas. 16 The overall results showed a raising of the growth curves for the future horizons, indicating an 17 increase in the intensity of extreme precipitation, especially for the shortest durations. The DDF 18 curves highlight a general increase of extreme quantiles for the two urban areas, thus underlining the 19 risk of failure of the existing urban drainage systems under more severe events. 20 21
Droughts and heatwaves can have profound impacts on society and the environment, which can be exacerbated by their co-occurrence. However, in China, co-occurrence of droughts and heatwaves has not been explored. Here we assess concurrent drought and heatwave events (CONDH) in summer across eastern China (EC) for 1962-2015. We found that these events are more frequent in the North and South of EC (>20 events during 1962-2015) and less frequent in the central region. In the North and Southdoi:10.1016/j.wace.2019.100242 fatcat:2k3og54gavftnosggve3bzcjha
more »... , intensity of heatwaves is ~2-4 times higher during drought conditions than in average conditions. Also, in these two regions the number of CONDH events is more than double what would be expected if droughts and heatwaves were independent. When analyzing changes between 1962-1988 and 1989-2015, the dependence between drought and heatwave was shown to be stable, but the number of CONDH more than doubled in parts of the North and small areas in the South, and decreased by over 50% in the southern central region. We have shown that the North and South of EC are hotspots of compound droughts and heatwaves and therefore it is crucial to considering both events together when assessing how to adapt to present and future weather extremes.
By using gauge records obtained from the Blenkinsop et al. (2017) observational data set, an analysis based on a larger number of events may now be undertaken. ... of this scaling to the prevailing synoptic circulation (Blenkinsop et al., 2015) , to date there has been no detailed examination of the synoptic-scale drivers of intense U.K. subdaily rainfall. ...doi:10.1029/2018jd029664 pmid:31245232 pmcid:PMC6582617 fatcat:7khne65hdrandprdxferzy4xou
The "Western Tibetan Vortex" (WTV)-also termed the Karakoram Vortex-dominates the middle-to-lower troposphere and the near-surface air temperature variability above the western Tibetan Plateau (TP). Here, we explore the thermodynamic mechanisms through which the WTV modulates air temperature over the western TP by diagnosing the three major terms of the thermodynamic energy equation-adiabatic heating, horizontal temperature advection, and diabatic heating-that maintain the atmospheric thermaldoi:10.1007/s00382-019-04785-2 pmid:31929690 pmcid:PMC6936652 fatcat:tktcm43aobgxppwgabtcvsvifa
more »... lance. We composite these major terms to examine the differences between anti-cyclonic and cyclonic WTV events. Our theoretical approach demonstrates that adiabatic sinking-compression (rising-expansion) provides the overwhelming control on both the middle-to-lower tropospheric and lower stratospheric temperature increases (decreases) under anti-cyclonic (cyclonic) WTV conditions over the western TP high mountain area in all four seasons. This also explains the mechanisms behind the anomalous temperature "dipole" found between the mid-lower troposphere and lower stratosphere when the WTV was initially identified. Spatially, adiabatic heating effects are centred on the central western TP in summer and the south slope centring at 70°-80°E of the TP in other seasons. The other two terms, horizontal temperature advection and diabatic heating, have localized importance over the edges of the western TP. In a case study over the Karakoram area, we further demonstrate that adiabatic heating (rising-expanding-cooling/sinking-compressing-warming) is the dominant thermodynamic process controlling Karakoram air temperatures under WTV variability, except for at the very near surface in autumn and winter. Our analysis methods can be applied to investigate the thermodynamic processes of other atmospheric circulation systems or climate variability modes.
temperature and glacial melt driven by regional atmospheric circulation variability. Nature Climate Change 2017, http://dx. Summary Identifying mechanisms driving spatially heterogeneous glacial mass-balance patterns in the Himalaya, including the "Karakoram anomaly", is crucial for understanding regional water resource trajectories. Streamflows dependent on glacial meltwater are strongly positively correlated with Karakoram summer air temperatures, which show recent anomalous cooling. Wedoi:10.1038/nclimate3361 fatcat:rslseolwojdrlgdnswjsqwyhju
more »... n these temperature and streamflow anomalies through a circulation system -the Karakoram Vortexidentified using a regional circulation metric that quantifies the relative position and intensity of the westerly jet. Winter temperature responses to this metric are homogeneous across South Asia, but the Karakoram summer response diverges from the rest of the Himalaya. We show that this is due to seasonal contraction of the Karakoram Vortex through its interaction with the South-Asian monsoon. We conclude that interannual variability in the Karakoram Vortex, quantified by our circulation metric, explains the variability in energy-constrained ablation manifested in river flows across the Himalaya, with important implications for Himalayan glaciers' futures. [ Figure 1 ] Geographic definition, resulting zonal wind climatologies and conceptual structures for the Karakoram Zonal Shear (KZS). A) Locations and data origin for T2m station observations used. B) 200-hPa reanalysis-ensemble climatology (lines = mean, shaded area = 10 th to 90 th percentiles range) of zonal wind speeds in the northern (Unorth, in purple) and southern (Usouth, in orange) areas, and the KZS (in green), i.e. north minus south. C) a cross-section conceptual diagram of the KZS in relation to atmospheric processes and structures. In A) T2m station transects are shown as "I.V." (Indus Valley, latitudinal) and "H.A." (Himalayan Arc, longitudinal).
Temperature scaling studies suggest that hourly rainfall magnitudes might increase beyond thermodynamic expectations with global warming 1, 2, 3 ; that is, above the Clausius-Clapeyron (CC) rate of ~6.5% °C -1 . However, there is limited evidence of such increases in long-term observations. Here, we calculate continental-average changes in the magnitude and frequency of extreme hourly and daily rainfall observations from Australia over 1990-2013 and 1966-1989. Observed changes are compared todoi:10.1038/s41558-018-0245-3 fatcat:g74ujagwz5hu7eavm2psk6b5ye
more »... e uncertainty from natural variability and to expected changes from CC-scaling as a result of global mean surface temperature change. We show that increases in daily rainfall extremes are consistent with CC scaling, but are within the range of natural variability. By contrast, changes in the magnitude of hourly rainfall extremes are close to or exceed double the expected CC-scaling, and are above the range of natural variability, exceeding 3xCC in the tropical region (north of 23°S). These continental-scale changes in extreme rainfall are not explained by changes in the El Niño-Southern Oscillation or changes in the seasonality of extremes. Our results indicate that CC-scaling on temperature provides a severe underestimate of observed changes in hourly rainfall extremes in Australia, with implications for assessing the impacts of extreme rainfall. Main A warming climate is expected to cause an intensification of heavy rainfall 4 . Basic physical arguments suggest that, in the absence of changes in large-scale circulation (and associated moisture advection), the intensification will follow the water holding capacity of air, dictated
Blenkinsop, A. Burton, H. J. Fowler, P. Orban, and A. Dassargues (2011), Modeling climate change impacts on groundwater resources using transient stochastic climatic scenarios, Water Resour. ... This approach is demonstrated by Blenkinsop et al. ... Blenkinsop, H. J. Fowler, C. Harpham, A. Burton, and P. Goderniaux, Modelling transient climate change with a stochastic weather generator. ...doi:10.1029/2010wr010082 fatcat:3atxufrdojcyfeviefq5iv3zai
ORCID Stephen Blenkinsop https://orcid.org/0000-0003-0790-6545 Joseph Willis https://orcid.org/0000-0002-6766-363X Sanjay M. Sisodiya https://orcid.org/0000-0002-1511-5893 ...doi:10.1111/epi.17046 pmid:34462915 fatcat:67ho2vgkdvczjakovpdmkorbpi
We use 1903 quality controlled UK rain gauges (see Fig. 1a for coverage) from Blenkinsop et al. (2017) and Lewis et al. (2018) . ... As the measurements of precipitation gauge at instrument sites contain inevitable observational errors (McMillan et al. 2012 ), various quality control procedures were applied by Blenkinsop et al. (2017 ...doi:10.1007/s00382-020-05144-2 pmid:32226231 pmcid:PMC7089634 fatcat:kd6bpfcymzfe7jexopuycqbtwm
Newcastle University ePrints -eprint.ncl.ac.uk Chan SC, Kendon EJ, Roberts NM, Fowler HJ, Blenkinsop S. Downturn in scaling of UK extreme rainfall with temperature for future hottest days. ... ., Blenkinsop, S. & Roberts, N. M. Projected increases in summer and winter UK sub-daily precipitation extremes from high resolution regional climate models. Environ. Res. Blenkinsop, S., Chan, S. ...doi:10.1038/ngeo2596 fatcat:knfw4uyiibdhtby3vea55x3a7m
Newcastle University ePrints -eprint.ncl.ac.uk Blenkinsop S, Lewis E, Chan SC, Fowler HJ. Quality control of an hourly rainfall dataset and climatology of extremes for the UK. ... Blenkinsop et al., 2015) and lead to a better understanding of the potential drivers of flash flooding from intense rainfall. ... Blenkinsop, Water Resource Systems Research Laboratory, School of Civil Engineering and Geosciences, Cassie Building Newcastle University, Newcastle upon Tyne NE1 7RU, UK. ...doi:10.1002/joc.4735 pmid:28239235 pmcid:PMC5300158 fatcat:djkis3xo6nelraukmuq5dvg4b4
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