# Defining Heatwaves with Respect to Human Biometeorology. The Case of Attica Region, Greece

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## Abstract

**:**

## 1. Introduction

## 2. Materials and Methods

- A binary variable to capture if a percentile exceedance exists for each index (i.e., temperature, PET, and UTCI), with “0” signifying non-exceedance and “1” signifying exceedance of the percentile value, and
- Two binary heatwave variables, with “0” representing non-heatwave day and “1” representing heatwave day for durations that are greater than or equal to 2 and 3 days, respectively.

^{2}) interprets to what extent the variance of the heatwave variable explains the variance of the mortality. Lastly, in order to quantify the harvesting effect, we run a robust statistical analysis using the superposed Epoch analysis (SEA) as a means to observe when mortality peaks using different temperature percentiles. In the present section, the null H

_{0}and the alternative H

_{1}hypotheses are as follows:

**Hypothesis**

**1.**

**Hypothesis**

**2.**

**Hypothesis**

**3.**

## 3. Results

^{2}, 5 days after the event for the 97.5th percentile are equal to 0.044 for mean temperature, 0.039, for mean PET, and 0.033 for mean UTCI. In conclusion, the optimal and more robust definition of a heatwave for the case of Attica, concerning this analysis is “a period of at least 3 days when mean temperature is higher than the 97.5th percentile”. After defining a heatwave, we use the Superposed Epoch Analysis, a non-parametric statistical technique, using different percentiles of mean temperature, since as we show it is the optimal index to define a heatwave event and according to [17], it may best reflect heat stress For our estimation, the confidence interval is constructed using the preferred percentiles of the empirical distribution for a large number of resampled values. In particular, we use 10,000 resamples to construct the 95% confidence interval. Since our interest concentrates on the 15 days before and after an event, the superposed Epoch analysis constructs 10.000 randomly selected samples of size equal to 31 observations, which in turn are used to calculate the mean, the standard deviation, and finally, the confidence interval. The resampling method used in our analysis to construct the reported confidence intervals offer robustness for the results and thus minimizes the effects of data measurement errors.

## 4. Discussion

## 5. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 1.**Graphs of mortality for Attica: (

**a**) Graph of cardiological mortality during summer months; (

**b**) graph of respiratory mortality during summer months; (

**c**) graph of cardiorespiratory mortality during summer months.

**Figure 2.**Temperature graphs of mortality for Attica: (

**a**) Graph of mean temperature; (

**b**) graph of maximum temperature.

**Figure 5.**Map of mean values of cardiological, respiratory, and cardiorespiratory mortality (CR) for summer and winter for Attica. Note: The latitude and longitude coordinates are 37.983810 and 23.727539, respectively.

**Figure 6.**Superposed Epoch analysis for mortality due to cardiological diseases for duration of the heatwave event of at least 2 and 3 days: (

**a**) 95th percentile; (

**b**) 97.5th percentile; (

**c**) 99th percentile. Notes: (i) The shaded area shows the 95% Confidence Interval (CI), (ii) the vertical axis measures the mean number of deaths due to cardiological diseases, (iii) the horizontal axis depicts the time 15 days before and 15 days after the heatwave event. Day 0 is the first day of the event.

**Figure 7.**Superposed Epoch analysis for mortality due to respiratory diseases for duration of the heatwave event of at least 2 and 3 days: (

**a**) 95th percentile; (

**b**) 97.5th percentile; (

**c**) 99th percentile. Notes: (i) The shaded area shows the 95% Confidence Interval (CI), (ii) the vertical axis measures the mean number of deaths due to respiratory diseases, (iii) the horizontal axis depicts the time 15 days before and 15 days after the heatwave event. Day 0 is the first day of the event.

**Figure 8.**Superposed Epoch analysis for mortality due to cardiorespiratory diseases for duration of the heatwave event of at least 2 and 3 days: (

**a**) 95th percentile; (

**b**) 97.5th percentile; (

**c**) 99th percentile. Notes: (i) The shaded area shows the 95% Confidence Interval (CI), (ii) the vertical axis measures the mean number of deaths due to cardiorespiratory mortality, (iii) the horizontal axis depicts the time 15 days before and 15 days after the heatwave event. Day 0 is the first day of the event.

Mortality | Winter | Summer | ||||||
---|---|---|---|---|---|---|---|---|

Mean | Min. | Max. | Std. Deviation | Mean | Min. | Max. | Std. Deviation | |

Cardiological | 32.63 | 15.00 | 70.00 | 6.72 | 26.25 | 8.00 | 89.00 | 6.87 |

Respiratory | 10.10 | 1.00 | 36.00 | 5.00 | 7.94 | 0.00 | 31.00 | 4.19 |

Cardiorespiratory | 42.74 | 20.00 | 96.00 | 9.26 | 34.18 | 10.00 | 103.00 | 8.94 |

Percentiles | 90th | 92.5th | 95th | 97.5th | 99th |
---|---|---|---|---|---|

Mean Temperature | 28.67 | 29.23 | 30.00 | 31.00 | 32.15 |

Max. Temperature | 33.89 | 34.60 | 35.41 | 36.60 | 38.01 |

Mean PET | 28.61 | 29.50 | 30.58 | 31.39 | 33.46 |

Max. PET | 43.00 | 43.97 | 45.50 | 47.79 | 50.00 |

Mean UTCI | 28.35 | 29.17 | 30.02 | 31.25 | 32.55 |

Max. UTCI | 38.70 | 39.50 | 40.58 | 42.20 | 43.90 |

Temperature Percentile | 2 Days | |||||||||
---|---|---|---|---|---|---|---|---|---|---|

90th | 92.5th | 95th | 97.5th | 99th | ||||||

Days | Events | Days | Events | Days | Events | Days | Events | Days | Events | |

Mean Temp. | 858 | 142 | 635 | 114 | 404 | 81 | 196 | 51 | 82 | 24 |

Max Temp. | 11 | 5 | 7 | 3 | 2 | 1 | 0 | 0 | 0 | 0 |

Mean PET | 845 | 148 | 622 | 122 | 405 | 97 | 191 | 51 | 71 | 22 |

Max PET | 725 | 166 | 515 | 135 | 298 | 95 | 127 | 45 | 34 | 12 |

Mean UTCI | 841 | 147 | 617 | 121 | 402 | 93 | 186 | 51 | 74 | 23 |

Max UTCI | 766 | 169 | 536 | 129 | 340 | 99 | 142 | 44 | 46 | 16 |

Temperature Percentile | 3 Days | |||||||||
---|---|---|---|---|---|---|---|---|---|---|

90th | 92.5th | 95th | 97.5th | 99th | ||||||

Days | Events | Days | Events | Days | Events | Days | Events | Days | Events | |

Mean Temp. | 810 | 118 | 581 | 92 | 362 | 60 | 158 | 33 | 68 | 15 |

Max Temp. | 3 | 1 | 3 | 1 | 0 | 0 | 0 | 0 | 0 | 0 |

Mean PET | 779 | 116 | 570 | 94 | 339 | 63 | 149 | 30 | 57 | 15 |

Max PET | 615 | 112 | 401 | 85 | 194 | 45 | 83 | 22 | 20 | 6 |

Mean UTCI | 767 | 108 | 561 | 91 | 348 | 64 | 150 | 33 | 56 | 14 |

Max UTCI | 658 | 112 | 438 | 83 | 250 | 54 | 106 | 26 | 36 | 11 |

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**MDPI and ACS Style**

Dimitriadou, L.; Nastos, P.; Zerefos, C. Defining Heatwaves with Respect to Human Biometeorology. The Case of Attica Region, Greece. *Atmosphere* **2021**, *12*, 1100.
https://doi.org/10.3390/atmos12091100

**AMA Style**

Dimitriadou L, Nastos P, Zerefos C. Defining Heatwaves with Respect to Human Biometeorology. The Case of Attica Region, Greece. *Atmosphere*. 2021; 12(9):1100.
https://doi.org/10.3390/atmos12091100

**Chicago/Turabian Style**

Dimitriadou, Lida, Panagiotis Nastos, and Christos Zerefos. 2021. "Defining Heatwaves with Respect to Human Biometeorology. The Case of Attica Region, Greece" *Atmosphere* 12, no. 9: 1100.
https://doi.org/10.3390/atmos12091100