Hydroclimatic Bulletin for Planning Unit UP15

Radley Horton,1,a Daniel Bader,1,a Yochanan Kushnir,2 Christopher Little,3 Reginald Blake,4 and Cynthia Rosenzweig5 1Columbia University Center for Climate Systems Research, New York, NY. 2Ocean and Climate Physics Department, Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY. 3Atmospheric and Environmental Research, Lexington, MA. 4Physics Department, New York City College of Technology, CUNY, Brooklyn, NY. 5Climate Impacts Group, NASA Goddard Institute for Space Studies; Center for Climate Systems Research, Columbia University Earth Institute, New York, NY

BackgroundSeveral studies have investigated the association between asthma exacerbations and exposures to ambient temperature and precipitation. However, limited data exists regarding how extreme events, projected to grow in frequency, intensity, and duration in the future in response to our changing climate, will impact the risk of hospitalization for asthma. The objective of our study was to quantify the association between frequency of extreme heat and precipitation events and increased risk of hospitalization for asthma in Maryland between 2000 and 2012.MethodsWe used a time-stratified case-crossover design to examine the association between exposure to extreme heat and precipitation events and risk of hospitalization for asthma (ICD-9 code 493, n = 115,923).ResultsOccurrence of extreme heat events in Maryland increased the risk of same day hospitalization for asthma (lag 0) by 3 % (Odds Ratio (OR): 1.03, 95 % Confidence Interval (CI): 1.00, 1.07), with a considerably higher risk observed for extreme heat events that occur during summer months (OR: 1.23, 95 % CI: 1.15, 1.33). Likewise, summertime extreme precipitation events increased the risk of hospitalization for asthma by 11 % in Maryland (OR: 1.11, 95 % CI: 1.06, 1.17). Across age groups, increase in risk for asthma hospitalization from exposure to extreme heat event during the summer months was most pronounced among youth and adults, while those related to extreme precipitation event was highest among ≤4 year olds.ConclusionExposure to extreme heat and extreme precipitation events, particularly during summertime, is associated with increased risk of hospitalization for asthma in Maryland. Our results suggest that projected increases in frequency of extreme heat and precipitation event will have significant impact on public health.Electronic supplementary materialThe online version of this article (doi:10.1186/s12940-016-0142-z) contains supplementary material, which is available to authorized users.

Contribution of extreme daily precipitation to total rainfall over the Arabian Peninsula

Introduction: Several studies have shown associations between an increase in precipitation and a higher frequency of traffic accidents; a few have examined the relationship between high temperatures and motor vehicle crashes. However, to our knowledge, no studies exist assessing how extreme events, projected to grow in frequency, intensity, and duration in response to our changing climate, will impact the risk of injury from motor vehicle accidents. Our study quantified the association between frequency of extreme heat and precipitation events and change in injury risk from motor vehicle accident in Maryland between 2000 and 2012. Methods: Motor vehicle accident data was obtained from the Maryland Automated Accident Reporting System. Each observation in the data set corresponded to a unique collision event. A time-stratified case-crossover design was utilized to assess the association between exposure to extreme heat and precipitation events and risk of injury or death from motor vehicle accident. Additional stratified analyses examined risk by road type and season. Results: Over the study period, there were 461,009 motor vehicle accidents that resulted in injury or death. We observed an 18% increase (OR: 1.18; 95% CI: 1.17, 1.19) in risk of motor vehicle injury for every 1-day increase in extreme precipitation event, with the highest risk (29%) observed during autumn (OR: 1.29; 95% CI: 1.27, 1.32). Extreme precipitation related increase in motor vehicle injury was considerably higher when a road defect or obstruction was present (OR: 1.42, 95% CI: 1.32, 1.52). Changes in risk associated with extreme heat events were generally marginal. Conclusion: Extreme precipitation events, particularly in conjunction with a road defect or obstruction, are associated with an increased risk of injury from motor vehicle accidents in Maryland. Our results suggest that projected increases in frequency of extreme precipitation event will have a significant impact on public health.

Synchronisation, the tendency of climatic events to occur simultaneously, can arise from small‐scale and large‐scale atmospheric dynamics. Climate variables can be synchronised across broad spatial and temporal scales, manifesting as regional, continental and global teleconnection patterns. In the study, we analysed spatiotemporal patterns of inland extreme precipitation events (EPEs) and extreme sea surface temperature events (ESSTEs) in the Northern Hemisphere (0°N–60°N) to better understand their connection. Using gridded monthly gauge‐ and interpolation‐based datasets for precipitation and sea surface temperature from 1930 through 2020, we detected extreme events based on the 95th percentile threshold. We then quantified the synchronisation between extreme events using the event synchronisation (ES) method and compared our findings to a null model distribution to ensure that the identified links were non‐random. Subsequently, we constructed EPE and ESSTE complex networks and calculated key network metrics including degree centrality , mean geographic distance (MGD) and clustering coefficient . Our results showed that the EPEs and ESSTEs exhibited non‐monotonic trends over the past nine decades, with significant increasing trends after 1980. Key EPE network hubs were detected in Mexico, the African Sahel and parts of Asia, while ESSTE hubs appeared in the Atlantic Ocean near the UK and US borders, the Pacific Ocean close to East Asia and the Mediterranean and Red Seas. Analyses of MGD and revealed that the EPE network had larger MGDs and more intense local clustering in continental areas (Sahel and East Asia), indicating that EPEs experience teleconnections within these locations even though they also experience strong local associations. The findings of our EPE network contrast with those of our ESSTE network, which had lower MGD values and close clustering within specific ocean basins, as expected due to localised ocean–atmosphere coupling. Our findings suggest that the drivers for extreme climate events are complex and can lead to strong local and global connections.

Detection and attribution of extreme precipitation changes from 1961 to 2012 in the Yangtze River Delta in China

The observed trends in extreme precipitation events, and those in annual and seasonal mean precipitation in China during 1961–2001 are analyzed. The results show that the annual mean precipitation increases significantly in southwest, northwest, and east China, and decreases significantly in central, north and northeast China. The increasing trends in east China occurred mainly in summer, while the decreasing trends in central, north, and northeast China occurred in both spring and autumn. The increasing trends in most of northwest China occurred in all seasons. Patterns of the trends in extreme daily precipitation events are similar to those in the annual and seasonal mean precipitation except in the northwest China where most areas show increasing trends in extreme events only in summer. The extreme precipitation events in the Yangtze River basin increased dramatically by 10%–20% every 10 years in summer, consistent with the increasing trends in summer mean precipitation in the region. The circulation over East Asia shows a weakening trend in the summer monsoon over central‐east China.

Extreme precipitation events and increased risk of campylobacteriosis in Maryland, U.S.A

Facing climate change-related extreme events in megacities of China in the context of 1.5 °C global warming

BackgroundInfections with nontyphoidal Salmonella cause an estimated 19,336 hospitalizations each year in the United States. Sources of infection can vary by state and include animal and plant-based foods, as well as environmental reservoirs. Several studies have recognized the importance of increased ambient temperature and precipitation in the spread and persistence of Salmonella in soil and food. However, the impact of extreme weather events on Salmonella infection rates among the most prevalent serovars, has not been fully evaluated across distinct U.S. regions.MethodsTo address this knowledge gap, we obtained Salmonella case data for S. Enteriditis, S. Typhimurium, S. Newport, and S. Javiana (2004-2014; n = 32,951) from the Foodborne Diseases Active Surveillance Network (FoodNet), and weather data from the National Climatic Data Center (1960-2014). Extreme heat and precipitation events for the study period (2004-2014) were identified using location and calendar day specific 95th percentile thresholds derived using a 30-year baseline (1960-1989). Negative binomial generalized estimating equations were used to evaluate the association between exposure to extreme events and salmonellosis rates.ResultsWe observed that extreme heat exposure was associated with increased rates of infection with S. Newport in Maryland (Incidence Rate Ratio (IRR): 1.07, 95% Confidence Interval (CI): 1.01, 1.14), and Tennessee (IRR: 1.06, 95% CI: 1.04, 1.09), both FoodNet sites with high densities of animal feeding operations (e.g., broiler chickens and cattle). Extreme precipitation events were also associated with increased rates of S. Javiana infections, by 22% in Connecticut (IRR: 1.22, 95% CI: 1.10, 1.35) and by 5% in Georgia (IRR: 1.05, 95% CI: 1.01, 1.08), respectively. In addition, there was an 11% (IRR: 1.11, 95% CI: 1.04-1.18) increased rate of S. Newport infections in Maryland associated with extreme precipitation events.ConclusionsOverall, our study suggests a stronger association between extreme precipitation events, compared to extreme heat, and salmonellosis across multiple U.S. regions. In addition, the rates of infection with Salmonella serovars that persist in environmental or plant-based reservoirs, such as S. Javiana and S. Newport, appear to be of particular significance regarding increased heat and rainfall events.

ABSTRACTSeveral droughts and floods in Amazonia and Northeast Brazil have occurred in recent years and projections from Intergovernmental Panel on Climate Change indicate an increase of these extreme events. El Niño Southern Oscillation (ENSO) is one of the phenomena associated with extreme rainfall events in the Amazon. However, recent studies have indicated that the basic response of ENSO is dependent on the Madden–Julian Oscillation (MJO) phase. Hence, this study analyses the MJO influence on precipitation extreme events over northern South America in El Niño and La Niña years. Extreme precipitation events over northern South America for the rainy season (December–May) were obtained through a composite analysis of the combinations of ENSO and MJO phases. Most of the dry extreme events occurred during El Niño periods, while wet extreme events were more recurrent during La Niña or neutral years. However, the results showed that the MJO convection could enhance or weaken the basic response of ENSO on extreme precipitation events. Moreover, dry/wet extreme events over both Amazon and Northeast Brazil are favoured when MJO convection over Indonesia is enhanced (MJO phases 4 and 5)/suppressed (MJO phase 2). Additionally, the interannual variability of the extreme events showed an increasing linear trend for dry extreme events and a decreasing linear trend for wet extreme events. The results presented here contribute to a better understanding of the climate variability and will be helpful for the forecast of ENSO effects on extreme events over northern South America.

Comparison and evaluation of the performance of reanalysis datasets for compound extreme temperature and precipitation events in the Qilian Mountains

ABSTRACTDaily station records and output from the MERRA atmospheric reanalysis for the period 1979 onwards are used to examine extreme daily precipitation events at Ny Ålesund and three other sites located on Spitsbergen. Spitsbergen, lying between 77°N and 80°N, is the largest island of the Svalbard Archipelago. The region is frequently influenced by extratropical cyclones associated with the North Atlantic cyclone track and (in winter) regional baroclinicity due to proximity to the sea ice margin. Despite the stronger cyclone activity in winter, extreme precipitation events at Ny Ålesund, defined as those in the top 1% of the statistical distribution, can occur year round. On the basis of a composite analysis, extreme events tend to occur when the region is influenced by a trough of low sea level pressure extending from the southwest, southerly winds in the troposphere, positive anomalies in precipitable water, and pronounced upward motion (negative omega) at 500 hPa. This is linked to positive anomalies in 500 hPa heights over the Barents Sea and negative anomalies over Greenland. While individual extreme events do not share all of these characteristics, strong southerly flow and positive anomalies in precipitable water provide a near common thread. Reflecting local topography, extremes at Ny Ålesund are typically not well represented at other stations on the island, but there are notable exceptions. Some of the largest precipitation events can be associated with features resembling ‘atmospheric rivers’, seen as narrow corridors of pronounced positive anomalies in precipitable water extending thousands of kilometres south into the subtropical Atlantic. There is no systematic pattern of temporal trends in the frequency or magnitude of extremes.

Adapting to climate change through anticipatory action: The potential use of weather-based early warnings

Climate models predict that amplification of the hydrological cycle results in more extreme (more intensive but less frequent) precipitation events (EPEs) that have larger effects on ecosystem functioning than mean precipitation conditions. Semiarid grassland ecosystems are considered important CH4 sinks whose functioning is greatly affected by variations in precipitation patterns. An experiment was performed to assess the effects of extreme precipitation events on the functioning of a fenced semiarid steppe grassland on the Inner Mongolian Plateau of China. Extreme precipitation events (282 mm over 20 consecutive days) during the middle (Pm) and late (Ps) growing periods of 2014 were simulated to assess the effects of extreme precipitation events on the CH4 uptake of the ecosystem. The extreme precipitation events had no significant effect on the CH4 uptake rate during the growing season but did result in 62 and 45% reductions in the CH4 uptake rate during the Pm and Ps events, respectively. There were legacy effects on suppression of the CH4 uptake rate for approximately 40 and 35 days after the events in the Pm and Ps plots, respectively, but the suppression disappeared rapidly during the late season as a result of faster water loss. No significant differences in cumulative CH4 uptake were detected between the treatment and the control plots over the growing season as a whole, which demonstrates that the ecosystem functions as a CH4 sink. The average CH4 uptake rates were found to be strongly regulated by changes in the soil water content. The results suggest that the CH4 uptake budget of this fenced steppe grassland can be maintained even in the face of consecutive extreme precipitation events, regardless of the timing of the events. Nevertheless, long-term experiments are needed to detect the thresholds for CH4 uptake budget changes, in case of an increasing occurrence of EPEs in the future.