Wave Duration Index Research Articles

Extreme precipitation and temperature indices under future climate change in central Asia based on CORDEX-CORE

The present study analyzes the projected changes of extreme climate indices over Central Asia using regional climate model (RCM) simulations from the Coordinated Regional Climate Downscaling Experiment (CORDEX) - Coordinated Output for Regional Evaluations (CORE). The extreme indices are based on precipitation and temperature and are inspected for present (1981–2005) and future periods - near- (2031–2055) and far-future (2071–2095) - to assess the long-term climate change under the representative concentration pathway RCP8.5. Projected changes are analyzed for three different model ensembles. These ensembles are based on CORDEX-Central Asia (ENS_CAS, four ensemble members) and CORDEX-East Asia (ENS_EAS, six ensemble members), and a combination of both (ENS, ten ensemble members) for our study area centered over high mountain Asia, called Central East Asia (CEAS). For precipitation indices, an increase of consecutive dry days (CDD) in ENS_EAS and a slight to moderate decrease in northern parts in ENS_CAS during near-future is observed. Consecutive wet days (CWD), very heavy precipitation events (R20mm), maximum one-day precipitation (RX1day), and very wet days (R95p) are projected to increase in most areas. All indices show a further intensification towards the end of the century over large parts of the domain, e.g., + 7.8% / +5.6 days for CDD, + 96.6% / +0.26 days for R20mm, and + 19.7% for RX1day as median of ENS over CEAS. For temperature indices, the ensembles project a strong increase over the high mountain regions and southern parts for consecutive summer days (CSU, + 108.5% / +38.3 days), heat wave duration index (HWDI, + 1379.1% / +91.37 days), and the percentage of very hot days (TX90p, + 391.1% / +34.54 days). Accordingly, the number of consecutive frost days (CFD, -43.7% / -25.2 days) and the percentage of very cold days (TX10p, -83.4% / -8.13 days) are projected to decrease. The first-time usage of CORDEX-CORE and the larger ensemble size by considering simulations from overlapping domains increase the robustness of the findings from earlier studies. However, some discrepancies in the projected changes prevail among the different RCMs being part of the two CORDEX-domains and in specific landscapes like complex mountainous or lake areas. These uncertainties may be tackled by further model development with improved land-surface processes and potentially higher spatial resolution.

Simulation of Temperature Extremes Over West Africa With MPAS

AbstractA large ensemble of 51 simulations with the Model for Prediction Across Scales (MPAS) has been applied to assess its ability to reproduce extreme temperatures and heat waves in the area of West Africa. With its global approach the model avoids transition errors influencing the performance of limited area climate models. The MPAS simulations were driven with sea surface temperature (SST) and sea ice extent as the only boundary condition. The results reveal moderate cold biases in the range from −0.6° to −0.9°C for the daily mean temperature and −1.2° to −2.0°C for the area mean of the daily maximum temperature. The bias in the number of tropical nights ranges from +3 to −10 days. An underestimation by up to 50% is also present regarding the number of summer days. The heat wave duration index is underestimated regionally by 10%–60%. MPAS simulations are generally closer to the reanalysis results than they are to the observational reference. The results from long term runs and from short term runs with selected SST years are similar. Shortcomings in the reproduction of the temperature and precipitation indices found in the present investigation indicate that the global MPAS approach does provide a fidelity similar to that of the regional climate models.

P-wave indices as predictors of atrial fibrillation.

BackgroundP‐wave duration (PDURATION) and P‐wave area (PAREA) have been linked to risk of atrial fibrillation (AF), but they do not improve the efficacy of Framingham AF risk score. We suggest the incorporation of both variables in one index, the P‐wave area/P‐wave duration (PAREA / DURATION) index, which may be considered an expression of the average amplitude of the P wave that reflects aspects of P‐wave morphology.ObjectiveTo assess the prognostic value of P‐wave area/P‐wave duration index (PAREA/DURATION index) in lead II together with other P‐wave indices (PWIs) in incidence of AF in the Copenhagen Holter Study.MethodsThe study included 632 men and women, between 55 and 75 years with no apparent heart disease or AF. Baseline standard 12‐lead Electrocardiography (ECGs) were analyzed manually.ResultsThe median follow‐up time was 14.7 (14.5;14.9) years. A total of 68 cases of AF and 233 cases of death were recorded. The restricted cubic spline method showed a U‐shaped association between PAREA/DURATION and rate of AF. The lowest quintile of PAREA/DURATION index in lead II was associated with increased rate of AF, HR 2.80 (1.64–4.79). The addition of the new index to the Framingham model for AF improved the model in this population. The PAREA in lead II in its lowest quintile was also associated with increased rate of AF, HR 2.16 (1.25–3.75), but did not improve the Framingham model. PDURATION and P‐wave terminal force (PTF) were not significantly associated with AF.ConclusionA flat P wave as expressed by a small PAREA/DURATION index in lead II is associated with increased rate of incident AF beyond known AF risk factors.

Electrocardiographic characteristics for successful radiofrequency ablation of right coronary cusp premature ventricular contractions.

Electrocardiographic (ECG) criteria identifying right- and left-sided outflow tract origins have been established. The purpose of this study was to define the criteria for premature ventricular contractions (PVCs) originating from the right coronary cusp (RCC) adequately.We analyzed ECG and electrophysiologic study data from patients who underwent successful ablation of PVCs originating from the RCC and right ventricular outflow tract (RVOT). Eighteen RCC and 28 septal RVOT PVCs were studied. Among these 18 successful RCC PVCs, a predominantly positive QRS in lead I in 18/18 (100%), longer V1–2 R-wave duration (81.4 ± 31.1 vs 44.8 ± 7.0 ms, P = .02), V1–2 R wave duration index (RWDI) (51.3 ± 22.0 vs 31.2 ± 7.5%, P = .06) were observed compared to those with posteroseptal RVOT. Local ventricular activation time preceding QRS onset was significantly earlier (−38 ± 12 ms) at the successful RCC ablation site compared to the failed ablation site of the septal RVOT (−22 ± 8 ms), even without good pace mapping at the RVOT (P < .001). The receiver operating characteristic curve showed that a pre-QRS time of ≥−31 ms predicted successful RCC ablation with 67% sensitivity and 94% specificity. A predominantly positive QRS in lead I, longer R-wave duration and RWDI in lead V1 or V2 with a local ventricular activation preceding QRS onset by an average of −31 ms suggests an effective RCC ablation site.

Predictive Values of Different ECG Algorithms in Differentiating Left Ventricular Outflow Tract from Right Ventricular Outflow Tract Premature Ventricular Beats Origin

Background:Premature ventricular beats (PVBs) are early myocardial electrical oscillations, which are not life threatening in patients with normal cardiac architecture, however causing annoying morbidity; radiofrequency catheter ablation became a curative tool for elimination of this arrhythmia. Methods: This study was held on 80 symptomatic patients with PVBs of same morphology provided being of significant burden, these patients were eligible for PVB electrophysiological study and catheter ablation in EP unit, Ain Shams University. Detailed history, comprehensive general and local examination was fulfilled. Trans-thoracic echocardiographic study and Holter ECG monitoring was offered for the studied population. Different algorithms for PVB origin identification were utilized in all patients before electrophysiological localization and radiofrequency ablation was done. Results: mean age of studied population was 39.9±12.97 years, encompassing 44 (59.4%) males, admitted to our centre for EP study and ablation. PVB origin was unleashed initially via various algorhythms, which matched precise intra-cardiac origin in 78 cases; patients with PVBs originating from LVOT showed earlier transition, narrowed QRS complex, higher V2 transition ratio and R wave duration index as compared to those with PVBs originating from RT side. With multivariate logistic regression, the only significant independent predictor for RVOT origin was R wave duration index utilizing a cut off value of ˂ 0.3 (P=0.0057). Conclusion:Accurate localization of PVB origin is feasible using surface ECG with positive impact on acute procedural success as well as reducing procedural time.

Performance of BCC-CSM Models with Different Horizontal Resolutions in Simulating Extreme Climate Events in China

In this study, the performance of the Beijing Climate Center (BCC) Climate System Model version 1.1 (BCC-CSM1.1) (280-km resolution) and the BCC-CSM1.1m (110-km resolution) in simulating extreme climate events over China in the last 40 years is compared. Both models capture the main spatial distribution features of heavy precipitation (R95T), the number of consecutive wet days (CWD), the annual count of days with precipitation mm (R1), the maximum consecutive 5-day precipitation (Rx5), and the numbers of frost days (FD) and summer days (SU). The BCC-CSM1.1m has a better ability to simulate the detailed distribution of extreme climate events than the BCC-CSM1.1, including R95T, CWD, R1, and the simple precipitation intensity index (SDII). However, the BCC-CSM1.1m does not show an improvement in simulating the number of days with extreme precipitation (R90N), the number of consecutive dry days (CDD), the heat wave duration index (HWDI), the warm day frequency (TX90P), and cold night frequency (TN10P). This indicates that the simulation of the R95T, CWD, R1, and SDII climate events is more sensitive to the resolution of the model. The improved BCC-CSM1.1m is used to explore the projection of extreme climate change in China during the 21st century under the RCP4.5 (Representative Concentration Pathways) and RCP8.5 scenarios. The results show that extreme precipitation will increase dramatically over North and Southwest China in the late 21st century. The CWD index will decrease on the Tibetan Plateau and in northeastern and central China and will increase in other parts of China; R1 will increase in northern China and decrease in southern China; Rx5 will increase dramatically in southern China; FD will decrease and SU will increase over China in the late 21st century under both emission scenarios, with larger amplitudes in RCP8.5.

Heatwave Trends and the Population Exposure Over China in the 21st Century as Well as Under 1.5 °C and 2.0 °C Global Warmer Future Scenarios

Heatwaves exert negative socio-economic impacts and particularly have serious effects on public health. Based on the multi-model ensemble (MME) results of 10 downscaled high-resolution Fifth Phase of the Coupled Model Intercomparison Project (CMIP5) model output from NASA Earth Exchange Global Daily Downscaled Projections (NASA-GDDP), the intensity (largest lasting time), frequency and total duration of heatwaves over China as well as population exposure in the 21st century and at 1.5 °C and 2.0 °C above pre-industrial levels are investigated by using the three indices, the Heat Wave Duration Index (HWDI), annual total frequency of heatwaves (N_HW) and annual total days of heatwaves (T_HW) under RCP4.5 and RCP8.5. The MME results illustrate that heatwaves are projected to become more frequent (0.40/decade and 1.26/decade for N_HW), longer-lasting (3.78 days/decade and 14.59 days/decade for T_HW) as well as more extreme (1.07 days/decade and 2.90 days/decade for HWDI under RCP4.5 and RCP8.5 respectively) over China. High latitude and high altitude regions, e.g., the Tibetan Plateau and northern China, are projected to experience a larger increase of intensity, frequency and the total time of heatwaves compared with southern China (except Central China). The total population affected by heatwaves is projected to increase significantly and will reach 1.18 billion in later part of the 21st century, and there will be more and more people expected to suffer long heatwave time (T_HW) in the 21st century. Compared with a 2.0 °C global warming climate, holding the global warming below 1.5 °C can avoid 26.9% and 29.1% of the increase of HWDI, 34.7% and 39.64% for N_TW and 35.3%–40.10% of T_HW under RCP4.5 and RCP8.5 respectively. The half-degree less of warming will not only decrease the population exposure by 53–83 million but also avoid the threat caused by longer heatwave exposure under the two scenarios. Based on the comprehensive assessment of heatwave under the two RCP scenarios, this work would help to enhance the understanding of climate change and consequent risk in China and thus could provide useful information for making climate adaptation policies.

Association of P wave duration index with atrial fibrillation recurrence after cryoballoon catheter ablation

AimWe aimed to investigate the relationship between the recurrence of AF and P wave duration index (PWDI) in patients with nonvalvular PAF. MethodsWe included 114 patients who underwent cryoballoon catheter ablation with the diagnosis of paroxysmal atrial fibrillation (PAF) (55 male, 59 female; mean age 55.5±10,9years). PWDI was calculated by dividing the Pwd by the PR interval in DII lead of 12‑lead ECG. Patients had regular follow-up visits with 12-lead ECG, medical history and clinical evaluation. 24h Holter ECG monitoring had been recorded at least 12months after ablation. ResultsAF recurrence was detected in 24 patients after 1year. Patients were divided into two groups according to the AF recurrence. All parameters were compared between the two groups. Age, DM, HT frequency, ACEI-ARB use, CHA2DS2VASc and HAS-BLED score, HsCRP, LA diameter, LA volume, LA volume index, Pwd and PWDI were related to AF recurrence. In binary logistic regression analysis, PWDI (OR=1.143, p=0.001) and HT (OR=0.194, p=0.020) were found to be independent parameters for predicting AF recurrence. Every 0,01 unit increase in PWDI was found to be associated with 14.3% increase in the risk of AF recurrence. The cut-off value of PWDI obtained by ROC curve analysis was 59,9 for prediction of AF recurrence (sensitivity: 75.0%, specificity: 69.0%). The area under the curve (AUC) was 0.760 (p<0.001). ConclusionIncreased PWDI may help to identify those patients in whom electrical remodeling has already occurred and who will get less benefit from cryoablation.

Outflow tract ventricular premature beats ablation in the presence or absence of structural heart disease: Technical considerations and clinical outcomes.

BackgroundPremature ventricular beats (PVBs) are early depolarization of the myocardium originating in the ventricle. In case of very frequent PVBs, patients are severely symptomatic with impaired quality of life and are at risk of pre-syncope, syncope, heart failure, and sudden cardiac death particularly in the presence of structural heart disease. Ventricular outflow tracts are the most common sites of origin of idiopathic PVBs especially in patients without structural heart disease. We examined the role of radiofrequency catheter ablation in suppression of monomorphic PVBs of outflow tract origin in the presence or absence of structural heart disease, and its impact on improvement of left ventricular (LV) systolic function.MethodsThirty-seven highly symptomatic patients with PVBs burden exceeding 10% were enrolled, provided that PVBs are monomorphic, originating in ventricular outflow tracts and regardless the presence or absence of structural heart disease. Patients were divided into 2 groups according to PVB site origin (RVOT vs. LVOT). 3D electro-anatomical mapping modalities were used in all patients employing activation mapping technique in the majority of cases. Acute success was considered when PVBs completely disappeared or when residual sporadic PVBs ≤ 1 beats/min or ≤10 beats/30 min after RF ablation. Patients were followed up for a mean period of 5.4 ± 1.2 months with long-term success defined as complete disappearance or marked reduction by more than 75% in the PVBs absolute number on 24 h holter monitoring.ResultsMean age of the study group was 39.9 ± 12.97 years, including 22 (59.4%) males. PVBs originated in RVOT in 17 cases and in LVOT in the remaining 20 cases. Prevalence of structural heart disease and consequently shortness of breath was higher in LVOT group. Initial ECG localization matched EP localization in the majority (94%) of cases. R wave duration index was the only significant independent predictor for RVOT origin with cut off value of <0.3 (P = 0.0057) upon multivariate analysis. Acute success was encountered in 32 (86%) patients with all cases of failure in the LVOT group. Recurrence occurred in 5 (15%) cases without significant difference between both groups. All cases of recurrence had residual PVBs at the end of the procedure. 18 cases out of the study group showed significant improvement of their EF (>5%) at the end of the follow-up period with no significant differences between both groups (p = 0.09). A linear correlation was observed between PVBs burden at follow up and magnitude of improvement of LV EF, particularly in patients with resting LV dysfunction and increased LV internal dimensions.ConclusionsRF ablation is an effective and safe method for elimination of outflow tract PVBs irrespective of their origin and the presence or absence of structural heart disease. PVBs burden after ablation appears to be the main determinant for reversal of PVB induced myopathy particularly in those with increased LV internal dimensions.

Future Extreme Climates Projection over Huang-Huai-Hai Region of China

This study projects the future extreme climate changes over Huang-Huai-Hai (3H) region in China using a regional climate model (RegCM4). The RegCM4 performs well in “current” climate (1970-1999) simulations by compared with the available surface station data, focusing on near-surface air temperature and precipitation. Future climate changes are evaluated based on experiments driven by European-Hamburg general climate model (ECHAM5) in A1B future scenario (2070-2099). The results show that the annual temperature increase about 3.4 °C-4.2 °C and the annual precipitation increase about 5-15% in most of 3H region at the end of 21st century. The model predicts a generally less frost days, longer growing season, more hot days, no obvious change in heat wave duration index, larger maximum five-day rainfall, more heavy rain days, and larger daily rainfall intensity. The results indicate a higher risk of floods in the future warmer climate. In addition, the consecutive dry days in Huai River Basin will increase, indicating more serve drought and floods conditions in this region.

Evaluation of extreme climate events using a regional climate model for China

ABSTRACTExtreme climate events over China at the end of the 21st century (2080–2099) are investigated using the regional climate model RegCM4. Model performance is validated through comparison between observations and simulations over the period 1985–2005. The results show that RegCM4 can satisfactorily reproduce the spatial distribution of extreme climate events over China. The model simulates temperature extremes more accurately than precipitation. Under the RCP8.5 (high emission) scenario, the number of frost days decreases, and both the heat wave duration index and the growing season length increase dramatically towards the end of the 21st century. Changes in extreme temperature become increasingly pronounced from South to North China, with the most significant changes occurring on the Tibetan Plateau (TP). The proportion of heavy precipitation generally increases, except on the southern TP. The number of very heavy precipitation days increases by 25–50% in Northwest and East China. In winter, the number of consecutive dry days (CDD) decreases in North China and increases in South China. The greatest increases in CDD are found in June, July and August (JJA) in Southwest China. In a future that follows this scenario, drought events may be aggravated in Southwest China, and decrease in North China. In contrast, when repeating these projections under the assumption of the RCP4.5 scenario for emissions, the frequency of extreme climate events is reduced. These results suggest that reductions in greenhouse gas emissions may mitigate the effects of climate change over the coming decades.

Evaluation and Projection of Temperature Extremes over China Based on CMIP5 Model

Evaluation and projection of temperature extremes over China are carried out with 8 model datasets from CMIP5. Compared with the NCEP reanalysis data, multi-model weighted ensemble is capable of reproducing the 8 temperature extreme indices and 20-year return values of annual maximum/minimum temperatures. The time correlation coefficients of all the 8 indices between multi-model ensemble and the reanalysis can reach a significance level of 0.10. The spatial correlation coefficient of 20-year return level of annual maximum/minimum temperatures is greater than 0.98. Under the RCP4.5 scenario, more extreme warm events and less cold events are expected over China in multi-model ensemble. By the middle of the 21st century, the heat wave duration index will be multiplied 2.6 times. At the end of the 21st century, the cold wave duration index will decrease 71%, and the 20-year return value will increase 4°C in parts of China for the maximum/minimum temperatures. CitationYao, Y., Y. Luo, J.-B. Huang, 2012: Evaluation and projection of temperature extremes over China based on CMIP5 model.Adv. Clim. Change Res.,3(4), doi: 10.3724/SP.J.1248.2012.00179.

High-resolution climate change simulations for the Jordan River area

[1] For the estimation of future climate conditions in the Jordan River region, the National Center for Atmospheric Research–Penn State University meteorology model in the versions 3.5 and 3.7 driven with boundary data from the Max-Planck-Institute for Meteorology and Hadley Centre global circulation models and the Special Report on Emission Scenarios A1B emission scenario has been used. The spatial resolution of the nested dynamic downscaling approach was 18.6 km, and the transient runs were performed for the period 1960–2099. The investigated statistics include mean precipitation, frequency and intensity of wet days and strong precipitation events, as well as mean temperature and heat wave duration index. The results show that the models satisfactorily reproduce the mean temperature and precipitation patterns. The comparison with the observational reference for the period 1961–1990 reveals a bias in the annual mean precipitation ranging from −20% to +17%, with an ensemble mean of −3%. The models show limitations in reproducing the precipitation seasonality. All models underestimate the wet day frequency and show differences in the strong precipitation events. The simulations of the future climate signal indicate an ensemble mean increase of the annual mean temperature of approximately 2.1 K in the period 2031–2060 and 3.7 K for the period 2070–2099 related to the 1961–1991 mean. In the same periods, the annual mean precipitation is simulated to decrease by approximately −11.5% and −20%, respectively, which means a reduction of expected water availability in the Jordan River region. All models show an increase of the heat wave duration index. A significant elevation dependence is present in the simulated future climate signal on both temperature and precipitation. The simulations show an increased coefficient of variation in annual precipitation, indicating that larger interannual precipitation variability can be expected in the future.

Extreme climate events in China: IPCC-AR4 model evaluation and projection

Observations from 550 surface stations in China during 1961–2000 are used to evaluate the skill of seven global coupled climate models in simulating extreme temperature and precipitation indices. It is found that the models have certain abilities to simulate both the spatial distributions of extreme climate indices and their trends in the observed period. The models’ abilities are higher overall for extreme temperature indices than for extreme precipitation indices. The well-simulated temperature indices are frost days (Fd), heat wave duration index (HWDI) and annual extreme temperature range (ETR). The well-simulated precipitation indices are the fraction of annual precipitation total due to events exceeding the 95th percentile (R95T) and simple daily intensity index (SDII). In a general manner, the multi-model ensemble has the best skill. For the projections of the extreme temperature indices, trends over the twenty-first century and changes at the end of the twenty-first century go into the same direction. Both frost days and annual extreme temperature range show decreasing trends, while growing season length, heat wave duration and warm nights show increasing trends. The increases are especially manifested in the Tibetan Plateau and in Southwest China. For extreme precipitation indices, the end of the twenty-first century is expected to have more frequent and more intense extreme precipitation. This is particularly visible in the middle and lower reaches of the Yangtze River, in the Southeast coastal region, in the west part of Northwest China, and in the Tibetan Plateau. In the meanwhile, accompanying the decrease in the maximum number of consecutive dry days in Northeast and Northwest, drought situation will reduce in these regions.

An analysis of heat waves in Belgrade and Niš using the climate index

An analysis of heat waves is done using the Heat Wave Duration Index (HWDI) for Belgrade and Niš. The length and severity of heat waves at two meteorological stations in Serbia were analyzed based on the daily maximum temperatures during the summer (June, July and August) and winter (December, January and February).

Regional analysis of extreme temperature and precipitation indices for the Carpathian Basin from 1946 to 2001

Since human and natural systems may be especially affected by changes of extreme climate events, the main objective of our research is to detect the possible changes of intensity and frequency of these extreme events. Several climate extreme indices are analyzed and compared for Central/Eastern Europe (focusing on Hungary) for the 20th century based on the guidelines suggested by the joint WMO-CCl/CLIVAR Working Group on climate change detection. These climate extreme indices include the numbers of severe cold days, winter days, frost days, cold days, warm days, summer days, hot days, extremely hot days, cold nights, warm nights, hot nights, the intra-annual extreme temperature range, the heat wave duration, the number of wet days (using several threshold values defining extremes, i.e., 10 mm and 20 mm), the maximum number of consecutive dry days, the highest 1-day precipitation amount, the greatest 5-day rainfall total, the simple daily precipitation intensity, the numbers of moderate wet days and very wet days, the annual fraction due to extreme precipitation events, etc. Therefore, daily maximum, minimum and mean temperature observations (from 13 stations) and daily precipitation amounts (from 31 stations) are used in the present statistical analysis. Our results suggest that similarly to the global and continental trends, regional temperature of Central/Eastern Europe has become warmer during the second half of the 20th century. Specifically, the strongest increasing tendency is detected in case of the annual numbers of hot days, summer days, warm days, warm nights, and the heat wave duration index. Before this warming period in the last quarter of the 20th century, most of the indices exhibit a cooling period until the middle of the 1970's. Furthermore, regional intensity and frequency of extreme precipitation has increased (as shown by the annual fraction due to extreme precipitation events, and the numbers of moderate wet days, very wet days, and very heavy precipitation days) between 1976 and 2001, while the total precipitation has decreased (as shown by numbers of precipitation days exceeding 0.1 mm, 1 mm, and 5 mm) in the region.

Climate change scenarios for surface temperature in Emilia-Romagna (Italy) obtained using statistical downscaling models

Summary Possible changes of mean climate and the frequency of extreme temperature events in Emilia-Romagna, over the period 2070–2100 compared to 1960–1990, are assessed. A statistical downscaling technique, applied to HadAM3P experiments (control, A2 and B2 scenarios) performed at the Hadley Centre, is used to achieve this objective. The method applied consists of a multivariate regression based on Canonical Correlation Analysis (CCA), using as possible predictors mean sea level pressure (MSLP), geopotential height at 500 hPa (Z500) and temperature at 850 hPa (T850), and as predictands the seasonal mean values of minimum and maximum surface temperature (Tmin and Tmax), 90 th percentile of maximum temperature (Tmax90), 10 th percentile of minimum temperature (Tmin10), number of frost days (Tnfd) and heat wave duration (HWD) at the station level. First, the statistical model is optimised and calibrated using NCEP=NCAR reanalysis to evaluate the large-scale predictors. The observational data at 32 stations uniformly distributed over Emilia-Romagna are used to compute the local predictands. The results of the optimisation procedure reveal that T850 is the best predictor in most cases, and in combination with MSLP, is an optimum predictor for winter Tmax90 and autumn Tmin10. Finally, MSLP is the best predictor for spring Tmin while Z500 is the best predictor for spring Tmax90 and heat wave duration index, except during autumn. The ability of HadAM3P to simulate the present day spatial and temporal variability of the chosen predictors is tested using the control experiments. Finally, the downscaling model is applied to all model output experiments to obtain simulated present day and A2 and B2 scenario results at the local scale. Results show that significant increases can be expected to occur under scenario conditions in both maximum and minimum temperature, associated with a decrease in the number of frost days and with an increase in the heat wave duration index. The magnitude of the change is more significant for the A2 scenario than for the B2 scenario.

Observed temperature changes in Emilia-Romagna: mean values and extremes

Temporal and spatial variability of temperature in Emilia-Romagna is described using daily maximum and minimum temperature at 40 stations covering the period 1958 to 2000. Before use, data were quality controlled and tested for inhomogeneity using standard techniques. First, a description of climatological values of maximum and minimum temperature and of their temporal variability is given. Then, frequency of extreme events in temperature is described using 4 indices: 10th percentile of minimum temperature, 90th percentile of maximum temperature, number of frost days and heat wave duration. These indices are based on daily temperature and were computed for all seasons. For each season and each index, the magnitude of trends was estimated by linear regres- sion, while statistical significance was evaluated by Kendall's τ. The analysis reveals the presence of an increase in mean maximum and minimum temperature, especially during winter and summer. Trends were significant in the plain and hill area. Similar tendencies were also observed in the 10th percentile of daily minimum temperature in both seasons, accompanied by a reduction in the num- ber of frost days during winter. Positive trends were detected in the 90th percentile of daily maximum temperature during winter, spring and summer, leading to an increase in the heat wave duration index. These results were significant over almost the whole region, summer being the season charac- terised by the greatest number of stations with significant trends. The spatial variability of frequency of extreme events was analysed using cluster techniques. Finally, the relationship between winter frequency of extreme temperature events in Emilia-Romagna and large-scale Euro-Atlantic circula- tion patterns is briefly described. The results show the presence of significant values of correlation with some of the patterns considered, namely the Eastern Atlantic and European Blocking pattern.

Changes in Temperature-based Extremes Indices Due to Global Warming Projected by a Global 20-km-mesh Atmospheric Model

Changes in temperature-based extremes over land due to global warming estimated by a global 20-km-mesh atmospheric model are analyzed using Frich’s five extremes indices. At the end of the 21st Century, under the Intergovernmental Panel on Climate Change (IPCC) SRES A1B scenario, the model projects that the total number of frost days (Fd) decreases by more than 20 days per year and the length of the growing season (GSL) increases by about 14-34 days in northern mid- and high latitudes. The heat wave duration index (HWDI) and the percentage of time with a daily minimum temperature above the present-day 90th percentile (Tn90) increase worldwide. The intra-annual extreme temperature range (ETR) decreases in northern high latitudes, east Asia, and eastern North America by 1.3-3.9°C, but it increases by 1.0°C in the Amazon. The high-resolution simulation reveals that changes in these indices are influenced by regional properties, such as the altitude and distance from the coast.