Synoptic Climatological Approach Research Articles

Thermodynamic and Dynamic Components of Winter Temperature Changes in Western Canada, 1950–2020

Abstract Most of the globe has experienced significant warming trends that have been attributed to anthropogenic climate change. However, these rates of warming are also influenced by short-term climate fluctuations driven by atmospheric circulation dynamics, resulting in inconsistent trend magnitudes in both time and space. This research evaluated winter (December–February) temperature trends over 1950–2020 at 91 climate stations across British Columbia (BC), Alberta (AB), and Saskatchewan (SK), Canada, and determined the components attributed to thermodynamic and dynamic (atmospheric circulation) factors. A synoptic climatological approach was used to classify atmospheric circulation patterns in the midtroposphere, relate those patterns to surface temperature, and evaluate changes in frequency. Moderate to high temperature increases over 71 years were found for most of the region, averaging 3.1°C in southern SK to 4.1°C in central-northern AB, and a maximum of 5.8°C in northern BC. Low to moderate increases were found for southern BC, averaging 1.2°C. Changes in atmospheric circulation accounted for 29% and 31% of observed temperature changes in central-northern BC and AB, respectively. Dynamic factors were a moderate driver in southern AB (18%) and central-northern SK (13%), and low in southern SK (5%). Negative dynamic contributions in southern BC (−6%), suggest that atmospheric circulation changes counteracted thermodynamically driven temperature changes. Results were consistent with trend analyses, indicating this method is well suited for trend detection and identification of thermodynamic and dynamic drivers. Results of this research improve our understanding of the magnitude of winter temperature changes critical for informing adaptation and climate-related policy decisions. Significance Statement Winter temperatures are strongly influenced by atmospheric circulation patterns, which move warm or cold air masses over large distances. We wanted to understand how changes in atmospheric circulation affect observed changes in winter temperatures in three provinces in western Canada. This also helps us to understand how much temperature change is due to anthropogenic (e.g., caused by greenhouse gases and land cover changes) and naturally occurring changes to Earth’s energy balance. Our results highlight the importance of understanding variability when selecting a time series for trend analyses or climate baselines for modeling studies. This study also helps to inform climate-related policies, decision-making, and adaptation strategies.

Climatological conditions of the Black Sea‐effect snowfall events in Istanbul, Turkey

AbstractA climatological analysis and overlying synoptic conditions of Black Sea‐effect snowfall events were investigated for Istanbul, Turkey, during the 1971–2006 winter (DJF) periods. Using the synoptic climatological approach, the Lamb Weather Type (LWT) method was applied to NCEP/NCAR daily mean sea level pressure data. Basically, northwesterly (NW), northerly (N), and northeasterly (NE) circulation types (CTs), which blow from the Black Sea (BS), were thought to be important for sea‐effect snowfall events to occur. Wind speeds and flows at 850‐hPa, directional shear, and temperature difference between sea surface and 850‐hPa level (SST‐T850) thresholds were applied to these three CTs in order to find suitable snowfall cases originating from the Black‐Sea. The results showed that 4, 14, and 111 snowfall episodes occurred during NW, N, and NE circulation types over Istanbul with the 2.8, 4.1, and 3.5 cm daily mean snow cover depths (DMSCD), respectively. In particular, it was found that interaction between a surface high located over continental Europe and a low pressure located over the central Black Sea, and a relatively warm sea surface temperature (SST), and cold temperature anomaly at the low level of the atmosphere (SST‐T850 > 17°C) are a favourable environment for the development of intense Black Sea‐effect snowstorms (DMSCD > 10 cm) sourced by NE cases. A statistically significant positive relation between snow cover depths and SST‐Tmax (daily maximum temperature) under NE cases (r = 0.28, p < .05) indicated that we observe intense daily snow accumulation when land‐sea temperature contrast increases (>7°C) in the region.

Synoptic climatological approach associated with three recent summer heatwaves in the Canadian Arctic

Abstract The observed unusually high temperatures in the Arctic during recent decades can be related to the Arctic sea ice declines in summer 2007, 2012 and 2016. Arctic dipole formation has been associated with all three heatwaves of 2007, 2012 and 2016 in the Canadian Arctic. Here, the differences in weather patterns are investigated and compared with normal climatological mean (1981–2010) structures. This study examines the high-resolution datasets from the North American Regional Reanalysis model. During the study periods, the north of Alaska has been affected by the low-pressure tongue. The maximum difference between Greenland high-pressure centre and Alaska low-pressure tongue for the summers of 2012, 2016 and 2007 are 8 hPa, 7 hPa and 6 hPa, respectively, corresponding and matching to the maximum summer surface Canadian Arctic temperature records. During anomalous summer heatwaves, low-level wind, temperatures, total clouds (%) and downward radiation flux at the surface are dramatically changed. This study shows the surface albedo has been reduced over most parts of the Canadian Arctic Ocean during the mentioned heatwaves (∼5–40%), with a higher change (specifically in the eastern Canadian Arctic region) during summer 2012 in comparison with summer 2016 and summer 2007, agreeing with the maximum surface temperature and sea ice decline records.

Identifying patterns of airborne pollen distribution using a synoptic climatology approach

Understanding the mechanisms of pollen release and dispersion in the atmosphere is of high importance, not only for getting an insight on the patterns of movement of these biological particles that are necessary for plants' reproduction, but also because exposure to airborne pollen is a major concern for respiratory allergies worldwide. In this work, a synoptic circulation-to-environment classification method was adopted to elucidate the relationship between distinct atmospheric patterns and pollen levels for the 11 most abundant but also allergenic taxa in Thessaloniki, Greece, for the 15-year period 1987–2001. It was found that the NW1 depressional weather type is associated with the “low winter pollen season” and high levels of pollen from Carpinus spp., Corylus spp., Cupressaceae, Platanus spp., Pinaceae, Quercus spp. and Urticaceae. In contrast, the SW1 cyclonic type is linked to the “high spring-summer pollen season” and high levels of pollen from Oleaceae and Urticaceae. On the other hand, anticyclonic weather is associated with the “summer-autumn pollen season” and high levels of Poaceae and Chenopodiaceae pollen in the atmosphere. Regional transport of Alnus pollen is linked to a strong high-pressure system centered over Italy, giving light NE winds over northern Greece. These findings shed light to the synoptic climatology of airborne pollen in Thessaloniki and could feed early-warning systems for alerting vulnerable groups of the allergic population.

Weather patterns and all-cause mortality in England, UK.

Cold- and heat-related mortality poses significant public health concerns worldwide. Although there are numerous studies dealing with the association between extreme ambient temperature and mortality, only a small number adopt a synoptic climatological approach in order to understand the nature of weather systems that precipitate increases in cold- or heat-related mortality. In this paper, the Lamb Weather Type synoptic classification is used to examine the relationship between daily mortality and weather patterns across nine regions of England. Analysis results revealed that the population in England is more susceptible to cold weather. Furthermore, it was found that the Easterly weather types are the most hazardous for public health all-year-long; however, during the cold period, the results are more evident and spatially homogenous. Nevertheless, it is noteworthy that the most dangerous weather conditions are not always associated with extreme (high or low) temperatures, a finding which points to the complexity of weather-related health effects and highlights the importance of a synoptic climatological approach in elucidating the relationship between temperature and mortality.

Using self-organizing maps to identify the South Asian seasonal cycle

A synoptic climatological approach using the self-organizing maps (SOMs) technique has been used to identify South Asian seasonality, by categorizing atmospheric patterns for each of five near-surface variables. This research mainly focused on showing the general climatology of the monsoonal seasonal cycle through four traditional seasons (winter, pre-monsoon, monsoon, and post-monsoon) and the transitions between each of these seasons, highlighting spatiotemporal variability. For each variable, a 9 × 9 SOM was created using surface-level reanalysis data. Each node in each SOM is assigned to a season or a seasonal transition, based on defined standard criteria. The SOM-based synoptic approach helps to increase our understanding and visualization of the different atmospheric conditions and their seasonal cycle of the South Asian climate, such as a complete reversal of mean sea-level pressure over the course of the year, with high pressure over the land in winter and low pressure in the summer, and a clear seasonal cycle in wind direction with cyclonic and anticyclonic circulations in different seasons creating a greater wind speed over the ocean than the land.

Atmospheric circulation variability and vintage Port wine

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 75:117-130 (2018) - DOI: https://doi.org/10.3354/cr01513 Atmospheric circulation variability and vintage Port wine Anthony J. Vega1,*, Sara A. Ates2, Robert V. Rohli2 1Department of Biology and Geoscience, Clarion University of Pennsylvania, Clarion, PA 16214, USA 2Department of Geography and Anthropology, Louisiana State University, Baton Rouge, LA 70803-4105, USA *Corresponding author: avega@clarion.edu ABSTRACT: The success of viticulture is inexorably tied to atmospheric conditions during the growing season. Previous work has tied observed and general circulation model (GCM)-projected changes in atmospheric variables to wine production in Europe. This research uses a synoptic climatological approach to examine the role of atmospheric circulation variability on wine production in the Douro Valley region of Portugal. Of particular interest is the atmospheric contribution to ‘vintage Port’ production. Vintage Port years are declared periodically and coincide with particularly high quality grape harvests. Results suggest that temperatures and potential evapotranspiration (PET) have increased significantly overall for the region, with the signal being present in both non-vintage and vintage years, while precipitation has remained statistically constant over the study period. Circulation analysis indicates that early winter ridging and drying offset by late winter pressure decreases and frontal cyclone tracking over the region is important during vintage years. Additionally, the analysis suggests that March synoptic drying followed by a significantly reduced PET during summer is important in vintage years. When followed by autumn maximum air temperatures and evapotranspiration rates that are significantly higher than normal, vintage Port results. Such conditions favor summer water retention in grapes, which increases the concentration of sugars through drying immediately prior to harvest. These results may be useful in alerting producers about quality of the upcoming harvest, especially as long-lead climate outlooks continue to improve. KEY WORDS: Port wine · Viticulture · Atmospheric circulation variability · Portugal Full text in pdf format PreviousNextCite this article as: Vega AJ, Ates SA, Rohli RV (2018) Atmospheric circulation variability and vintage Port wine. Clim Res 75:117-130. https://doi.org/10.3354/cr01513 Export citation Mail this link - Contents Mailing Lists - RSS Facebook - Tweet - linkedIn Cited by Published in CR Vol. 75, No. 2. Online publication date: May 30, 2018 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 2018 Inter-Research.

Synoptically classified lake-effect snowfall trends to the lee of Lakes Erie and Ontario

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 74:1-13 (2017) - DOI: https://doi.org/10.3354/cr01480 Synoptically classified lake-effect snowfall trends to the lee of Lakes Erie and Ontario Zachary J. Suriano*, Daniel J. Leathers Department of Geography, University of Delaware, Newark, DE 19716, USA *Corresponding author: zsuriano@udel.edu ABSTRACT: Recent research has indicated that snowfall in portions of the North American Great Lakes region subject to lake-effect snow has undergone a trend reversal, with snowfall declining in recent decades. This study examines the seasonal variability and trends specifically in synoptically classified lake-effect snow across the eastern Great Lakes region, and investigates the mechanisms responsible for observed changes. Using a synoptic climatological approach, days are identified where the synoptic-scale conditions are conducive to lake-effect snowfall and the associated snowfall is analyzed. Seven synoptic types over the November to March snowfall season are identified with characteristics of lake-effect conditions. Snowfall from these 7 lake-effect synoptic types represents between 45 and 53% of the seasonal snowfall total along the eastern shores of Lakes Erie and Ontario, with snowfall totals being highest during January. Lake-effect snowfall exhibits a 60 yr increasing trend downwind of Lakes Erie and Ontario; however, through examination over shorter 30 yr periods, a change in the trend of snowfall is observed around 1980. While a true trend reversal is not detected, lake-effect snowfall significantly increases from 1950-1979 before exhibiting no significant trend from 1980-2009. The inter-annual variability of seasonal lake-effect snowfall is highly related to the frequency of lake-effect synoptic types where an increase (decrease) in synoptic type occurrence leads to enhanced (diminished) lake-effect snowfall totals. Depending on the period examined, long-term changes in the frequency of lake-effect synoptic types and snowfall rates represent between 89 and 95% of the observed changes in lake-effect snow. KEY WORDS: Great Lakes · Synoptic classification · Snowfall variability · Climate change · Lake effect Full text in pdf format NextCite this article as: Suriano ZJ, Leathers DJ (2017) Synoptically classified lake-effect snowfall trends to the lee of Lakes Erie and Ontario. Clim Res 74:1-13. https://doi.org/10.3354/cr01480 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 74, No. 1. Online publication date: October 16, 2017 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 2017 Inter-Research.

Synoptic climatology of lake‐effect snowfall conditions in the eastern Great Lakes region

ABSTRACTThe characteristics of overlying synoptic conditions play an important role in the production of lake‐effect snowfall within the Great Lakes region of North America. With a synoptic climatological approach, the synoptic‐scale patterns conducive to lake‐effect snowfall are identified for the eastern Great Lakes region during the November–March seasons of 1950–2009. Seven synoptic types identified as lake effect are combined with daily snowfall observations to examine the role of individual synoptic types on seasonal snowfall. The types exhibit a wide range of surface and 850 hPa temperatures and winds, sea‐level pressures, snowfall intensities, and inter‐annual frequencies. These factors result in substantial differences in the location and magnitude of seasonal lake‐effect snowfall.Recent research has revealed that snowfall within portions of the Great Lakes region subject to lake‐effect snow has undergone a trend reversal, declining in recent decades. Examining the inter‐annual frequency of the seven lake‐effect synoptic types, a majority of types increased in frequency prior to 1980, before becoming less frequent thereafter. The variability in frequency of lake‐effect synoptic types can partially be explained by relationships to large‐scale atmospheric and oceanic modes of variability. The majority of lake‐effect synoptic types occur in association with an upper‐level trough over the eastern United States. This trough is consistent with the upper‐level pattern associated with a negative phase Arctic Oscillation (AO) and North Atlantic Oscillation (NAO), or positive Pacific/North American pattern (PNA), such that when the AO, NAO, and/or PNA pattern are in those respective phases, there is a significant increase in the frequency of lake‐effect synoptic types.

Atmospheric drivers of sea-level fluctuations and nuisance floods along the mid-Atlantic coast of the USA

As sea levels have risen and continue to rise, the risk of coastal flooding has increased in turn. While many studies have examined specific extreme flooding events, far fewer have explored the systematic associations between weather events and smaller, nuisance flood events. In this research, we take a synoptic climatological approach to assess this connection. We utilize self-organizing maps (SOMs) to separately cluster two atmospheric fields, sea-level pressure and 700-hPa geopotential height. We then utilize the output from these classifications to assess the impact of atmospheric conditions on the short-term fluctuations of sea level for the period 1979–2012, as well as the likelihood of nuisance flood occurrence, at five tidal gauges from Cape May, NJ, to Charleston, SC, along the mid-Atlantic coast of the USA. Results show the impacts of both the inverted barometer effect as well as surface wind forcing. Beyond this, the SOM nodes show a clear spatial continuum of associations between circulation and anomalous sea level, including some significant sea-level anomalies associated with relatively ambiguous pressure patterns. Moreover, the transitions from 1 day to the next are also analyzed, with results showing that rapidly deepening cyclones, or persistent onshore flow, can be associated with the greatest likelihood of nuisance floods. Results are generally weaker with 700-hPa height than sea-level pressure; however, in some cases, it is clear that the mid-tropospheric circulation can modulate the connection between sea-level anomalies and surface circulation.

Zooplankton community responses to regional-scale weather variability: a synoptic climatology approach

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 62:189-198 (2015) - DOI: https://doi.org/10.3354/cr01275 Zooplankton community responses to regional-scale weather variability: a synoptic climatology approach Ana Lígia Primo1,*, David G. Kimmel2,3, Sónia C. Marques1, Filipe Martinho1, Ulisses M. Azeiteiro1,4, Miguel A. Pardal1 1CFE - Centre for Functional Ecology, Department of Life Sciences, University of Coimbra, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal 2Department of Biology, East Carolina University, Greenville, NC 27858, USA 3Institute for Coastal Science and Policy, East Carolina University, Flanagan Building, Suite 250, Mail Stop 169, Greenville, NC 27858, USA 4Departamento de Ciências e Tecnologia, Universidade Aberta, 752 Rua do Ameal, 4200-055 Porto, Portugal *Corresponding author: ana.primo@uc.pt ABSTRACT: Estuarine and coastal ecosystems are strongly affected by variations in climate through alterations in freshwater input, which result in changes in water temperature and salinity. Predicting the response of estuarine systems to future scenarios of climate change requires knowledge of the present relationships between estuarine and coastal communities and variations in local weather patterns. Synoptic climatology is a method that identifies recurrent weather patterns at a regional scale (1000s of km) and is valuable for predicting estuarine ecosystem responses to environmental variability. This method was applied for a region of southwest Europe, and the effects of weather patterns on the zooplankton community of the Mondego Estuary (Portugal) were investigated. We identified 9 weather patterns for the region during the last 61 yr. A regression analysis related these weather patterns with freshwater flow in the estuary during the winter, and subsequently years between 2003 and 2011 were classified as average, dry or wet by a percentile approach. The abundance and spatial distribution of the zooplankton community responded to weather pattern variability during the winter. For example, years that featured lower precipitation, freshwater flow and higher salinity were characterized by marine planktonic groups. Salinity appeared to be the main factor related to zooplankton community changes. This study shows that the synoptic climatology approach is effective at capturing regional-scale dynamics of estuaries and at providing baseline climate relationships with estuarine zooplankton communities, which can be used to predict future response to climate change. KEY WORDS: Plankton communities · Synoptic climatology · Mondego Estuary · Climate variability Full text in pdf format PreviousNextCite this article as: Primo AL, Kimmel DG, Marques SC, Martinho F, Azeiteiro UM, Pardal MA (2015) Zooplankton community responses to regional-scale weather variability: a synoptic climatology approach. Clim Res 62:189-198. https://doi.org/10.3354/cr01275 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 62, No. 3. Online publication date: February 05, 2015 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 2015 Inter-Research.

The Relationship between Interannual Climate Variability and Juvenile Eastern Oyster Abundance at a Regional Scale in Chesapeake Bay

AbstractThe eastern oyster, Crassostrea virginica, is an important ecological and commercial species along the Eastern Seaboard of North America, although its abundance in Chesapeake Bay (Maryland and Virginia) has declined precipitously since the mid‐1800s. Management activities, including efforts to enhance larval settlement, to rebuild the Chesapeake Bay eastern oyster population have met with limited success. Since 1939, juvenile oyster abundance has been measured at oyster bars in the northern portion of Chesapeake Bay. Prior analyses of those data indicate that juvenile oyster abundance is influenced by environmental conditions, which are related to regional climate. We quantified a regional scale (1,000 km2) climate signal using a synoptic climatology approach by identifying predominant weather patterns. We related these weather patterns to Susquehanna River freshwater discharge, a major influencing factor on Chesapeake Bay salinity, and the Palmer Hydrological Drought Index (PHDI), an indicator of the overall wetness or dryness of a given region. We developed path analysis models that linked weather patterns to Susquehanna River discharge and thence to either the PHDI or ambient salinity and water temperature and finally to juvenile oyster abundance in one of four preidentified spatial groupings. The path models indicated that weather patterns that produce wet conditions, leading to a higher PHDI and lower salinity, resulted in reduced juvenile oyster abundance; weather patterns that produce dry conditions that decreased the PHDI and increased salinity resulted in higher juvenile oyster abundance. Our results indicate that regions of higher juvenile oyster abundance may be predicted several months in advance using the path model. These predictions can be used to increase the effectiveness of oyster restoration efforts by indicating where hard substrate added to oyster bars in the four regions is likely to result in greater than average numbers of juvenile oysters.Received January 16, 2013; accepted July 24, 2013Published online December 3, 2013

Associations between circulation pattern frequencies and sea ice minima in the western Arctic

ABSTRACTIn this study, a synoptic climatological approach is employed to assess the relationship between the frequency of circulation patterns (CPs) and the latitude of mid‐September sea ice minima in the western Arctic. Fifteen CPs are created via principal component analysis and cluster analysis from daily NCEP/NCAR reanalysis sea‐level pressure (SLP) fields across a grid from 50 to 90°N and 150°E–100°W from 1979 to 2011. The frequency of these CPs are statistically compared with the latitude of the sea ice minimum from passive microwave data for each of 11 equally‐spaced longitudes (176°W to 126°W) extending into the Chukchi and Beaufort Seas. Monthly frequencies for each of the 15 CPs from March to September, signifying the melt season, for each year are correlated with the ice minimum for that September. These monthly frequencies are then entered into a stepwise multiple linear regression (SMLR) and collectively, CP frequencies explain 40–79% of the total ice retreat variance across the longitudes. The frequency of one cluster, CP 11, representing a broad high pressure area over the Beaufort Sea, is highly correlated with the latitude of the sea ice minima; June and August frequencies of this pattern are the initial predictors at 8 of the 11 longitudes and explain 22–32% of the variance. This pattern has occurred more frequently from 2007 onwards; compared with a June mean occurrence of 9 days during 1979–2006, CP 11 occurred 16 times in June 2007, and on average more than 17 days per month during June 2008–2011. The Arctic Dipole (AD), Arctic Oscillation (AO), and Pacific‐North American (PNA) pattern indices are significantly correlated with CPs 11–13 frequencies throughout certain summer months, further indicating strong relationships between summer circulation and sea ice minima in the region.

Evaluating Linkages of Weather Patterns and Water Quality Responses in South Florida Using a Synoptic Climatological Approach

AbstractCoastal ocean ecosystems are impacted by atmospheric conditions and events, including episodic severe systems such as hurricanes as well as more regular seasonal events. The complexity of the atmosphere–ocean relationship makes establishing concrete connections difficult. In this paper, this relationship is assessed through synoptic climatological methods, a technique well established in applied climatological research but heretofore rarely used in assessing coastal ocean water quality and ecological status. Historical sea level pressure data are used to define 10 circulation patterns across the southeastern United States and adjacent Gulf of Mexico, based on the spatial pattern of sea level pressure, which can then be associated with the presence of cyclones, precipitation, and wind stress. The frequency of these patterns, and their deviation from climatological means, is then compared with Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) chlorophyll observations over the Florida Bay and south Florida shelf for the period 1997–2010. Several circulation patterns indicative of cyclonic activity over the broader region are associated with increased chlorophyll levels in the study area, while several other patterns, indicative of anticyclonic conditions, are associated with decreased chlorophyll levels. These relationships are spatially and temporally variable, generally with stronger correlations observed in winter and spring, and farther north in the study region when compared with more southern locations near the Florida Keys. The results here demonstrate the potential of using synoptic analysis and derived statistics for tracking and modeling changes in chlorophyll and other indicators related to water quality and biological health.

Influence of Meteorological Parameters and Air Pollutants onto the Morbidity due to Respiratory Diseases in Castilla-La Mancha, Spain

This study considers the relationship between the risk of hospital admission due to respiratory diseases, the daily weather, and the air pollution conditions between 2000 and 2006. A synoptic climatological approach is used to investigate the links between weather types and all hospital admissions due to respiratory diseases in Castilla-La Mancha (CLM), Spain. The main circulation weather types (CWTs) were determined for winter and spring, the seasons with the highest percentage of hospital admissions, and the frequency distribution of these types was also analyzed. The study includes a summary of the main characteristics of the hospital admission series and their distribution over the study period of seven years, as well as the frequency distributions of the admissions classified by gender and age, for each season, month and day of the week. In addition, an admission index was used to compare CWTs and hospital admissions due to respiratory diseases. The results show distinctly different responses of daily respiratory disease admission rates (RD) to the eight CWTs identified in winter and in spring. In winter, three CWTs (southwesterly (SW), anticyclonic (A) and hybrid anticyclonic southwesterly (HASW)) present values 1.5 times above the average admission rates. In contrast, there are no significant differences in spring. Finally, the results of Principal Component Analysis applied to the daily series of meteorological parameters, atmospheric pollutants and morbidity data revealed that in winter the decrease in RD is related to increases in temperature and pressure. These results represent an important step in identifying reliable connections between weather-air pollutants and human health.

Effects of weather types on hospital admissions for respiratory diseases in Castilla-La Mancha, Spain

The aim of this study is to evaluate the relationship between the risk of hospital admission for respiratory diseases (RD) and the daily weather types during the period 2000-2006. A synoptic climatological approach is used to investigate links between air-mass types (weather situations) and all respiratory hospital admissions in the Castilla-La Mancha (CLM) area in Spain. This afforded the main circulation weather types (CWTs) for the winter and spring periods (since respiratory hospital admissions reached their maximum during these seasons) and the frequency distributions of these types were analyzed. A summary of the main characteristics of the hospital admission series and their distribution over the seven years studied, together with the frequency distributions of the admissions classified by sex and ages, for season, month and for each day of the week, is reported. In addition, a comparison between air-mass classification and hospital admissions is made using an admission index (AI). The results reveal different responses of respiratory admission rates to the eight air-mass types identified in winter and in spring. In winter, three air massess southwesterly (SW), anti-cyclonic (A) and hybrid anti-cyclonic southwesterly (HASW), are associated with values 1.5 times higher than the respective average admission rates, while in spring no significant differences are seen.

Use of circulation types classifications to evaluate AR4 climate models over the Euro-Atlantic region

This paper presents an evaluation of the multi-model simulations for the 4th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) in terms of their ability to simulate the ERA40 circulation types over the Euro-Atlantic region in winter season. Two classification schemes, k-means and SANDRA, have been considered to test the sensitivity of the evaluation results to the classification procedure. The assessment allows establishing different rankings attending spatial and temporal features of the circulation types. Regarding temporal characteristics, in general, all AR4 models tend to underestimate the frequency of occurrence. The best model simulating spatial characteristics is the UKMO-HadGEM1 whereas CCSM3, UKMO-HadGEM1 and CGCM3.1(T63) are the best simulating the temporal features, for both classification schemes. This result agrees with the AR4 models ranking obtained when having analysed the ability of the same AR4 models to simulate Euro-Atlantic variability modes. This study has proved the utility of applying such a synoptic climatology approach as a diagnostic tool for models’ assessment. The ability of the models to properly reproduce the position of ridges and troughs and the frequency of synoptic patterns, will therefore improve our confidence in the response of models to future climate changes.

A Synoptic Climatological Approach to Assess Climatic Impact on Air Quality in South-central Canada. Part I: Historical Analysis

Automated synoptic weather typing and robust orthogonal stepwise regression analysis (via principal components analysis) were applied together to develop within-weather-type air pollution prediction models for a variety of pollutants (specifically, carbon monoxide – CO, nitrogen dioxide – NO2, ozone – O3, sulphur dioxide – SO2, and suspended particles – SP) for the period 1974–2000 in south-central Canada. The SAS robust regression procedure was used to limit the influence of outliers on air pollution prediction algorithms. Six-hourly Environment Canada surface observed meteorological data and 6-hourly US National Centers for Environmental Prediction (NCEP) reanalysis data of various weather elements were used in the analysis. The models were developed using two-thirds of the total years for meteorological and air pollution data; the remaining one-third (randomly selected) was used for model validation. Robust stepwise regression analysis was performed to analytically determine the meteorological variables that might be used to predict air pollution concentrations. There was a significant correlation between observed daily mean air pollution concentrations and model predictions. About 20, 50, and 80% of the 80 prediction models across the study area possessed R 2 values ≥ 0.7, 0.6, and 0.5, respectively. The results of model validation were similar to those of model development, with slightly smaller model R 2 values.

A Synoptic Climatological Approach to Assess Climatic Impact on Air Quality in South-central Canada. Part II: Future Estimates

Using within-weather-group air pollution prediction models developed in Part I of this research, this study estimates future air pollution levels for a variety of pollutants (specifically, carbon monoxide – CO, nitrogen dioxide – NO2, ozone – O3, sulphur dioxide – SO2, and suspended particles – SP) under future climate scenarios for four cities in south-central Canada. A statistical downscaling method was used to downscale five general circulation model (GCM) scenarios to selected weather stations. Downscaled GCM scenarios were used to compare respective characteristics of the weather groups developed in Part I; discriminant function analysis was used to allocate future days from two windows of time (2040–2059 and 2070–2089) into one of four weather groups. In Part I, the four weather groups were characterised as hot, cold, air pollution-related, and other (defined as relatively good air quality and comfortable weather conditions). In estimating future daily air pollution concentrations, three future pollutant emission scenarios were considered: Scenario I – emissions decreasing 20% by 2050, Scenario II – future emissions remaining at the same level as at the end of the twentieth century, and Scenario III – emissions increasing 20% by 2050. The results showed that, due to increased temperatures, the average annual number of days with high O3 levels in the four selected cities could increase by more than 40–100% by the 2050s and 70–200% by the 2080s (from the current areal average of 8 days) under the three pollutant emission scenarios. The corresponding number of low O3 days could decrease by 4–10% and 5–15% (from the current areal average of 312 days). For the rest of the pollutants, future air pollution levels will depend on future pollutant emission levels. Under emission Scenarios II and III, the average annual number of high pollution days could increase 20–40% and 80–180%, respectively, by the middle and late part of this century. In contrast, under Scenario I, the average annual number of high pollution days could decrease by 10–65%.

Winter air -mass-based synoptic climatological approach and hospital admissions for myocardial infarction in Florence, Italy

The aim of this study was to evaluate the relationship between the risk of hospital admission for myocardial infarction (MI) and the daily weather conditions during the winters of 1998–2003, according to an air-mass-based synoptic climatological approach. The effects of time lag and 2-day sequences with specific air mass types were also investigated. Studies concerning the relationship between atmospheric conditions and human health need to take into consideration simultaneous effects of many weather variables. At the moment few studies have surveyed these effects on hospitalizations for MI. Analyses were concentrated on winter, when the maximum peak of hospitalization occurred. An objective daily air mass classification by means of statistical analyses based on ground meteorological data was carried out. A comparison between air mass classification and hospital admissions was made by the calculation of a MI admission index, and to detect significant relationships the Mann–Whitney U test, the analysis of variance, and the Bonferroni test were used. Significant increases in hospital admissions for MI were evident 24 h after a day characterized by an anticyclonic continental air mass and 6 days after a day characterized by a cyclonic air mass. Increased risk of hospitalization was found even when specific 2-day air mass sequences occurred. These results represent an important step in identifying reliable linkages between weather and health.