Sport events on the international scale, e.g., the 2020 Olympics in Tokyo, are mostly hosted during the summer season. This might be due to the fact that they are often originating from Europe, where the summer season is the one with the largest fraction of thermally comfortable hours [1
]. There are several perspectives to be considered when analyzing the effect of meteorological conditions: (a) the athlete’s [2
] and (b) the visitors’ and workforces’ attending the events [1
]. This study does focus on athletes participating in the competitions of, as well as on visitors, originating from various places all over the world (e.g., Europe). Just like athletes, visitors have different thermal perception and they express different behaviors.
However, there are several factors which must be considered. First of all, it has to be stated that visitors and tourists are the groups mostly affected by extreme meteorological conditions. This is due to the usually short acclimatization time and lack of information on how to counteract the effects of heat while travelling. Proper hydration schedules, shading behaviors, and clothing should be adopted when exposed to outdoor conditions. On the other hand, athletes participating in events usually tend to arrive on the site of the event few days prior to competition. This strategy allows them to progressively acclimatize to the local climatic conditions and increase the exercising load up to the day of competition. To allow for a safe participation in sport events, it is recommended that athletes arrive at the competition location at least two weeks prior to the event [3
]. When arriving on the site of the event in advance is not possible, acclimatization should take place in an environment with similar climatic conditions to the final destination. Proper hydration behaviors and clothing should also be adopted, and athletes should be familiar with strategies to limit dehydration, sun exposure, and lowering their body temperature.
The existing methodologies for the quantification and assessment of the effect of the thermal environment on human beings, mostly estimating thermal indices, are well known and applied regularly for other purposes than sport events [1
]. Typical applications in this field are: analyzing different designs of open spaces and the effect on local thermal comfort, the benefit of green areas in terms of human thermal biometeorology [4
], as well as heat waves in urban areas [5
]. The impact of the environment on human thermal comfort includes different meteorological and non-meteorological parameters [6
]. Especially, some of the meteorological measures are severely modified by the environment (e.g., wind speed and the individual radiation fluxes) [8
]. Urban environments, which are most probably the prevailing environment type in Tokyo (alike all types of areas in general), generate modifications of the local meteorological conditions by morphology and surface properties of the various specific elements and their configurations [1
]. This, however, can be turned into an advantage as the resulting local micro climate may be modified by planning measures to achieve a reduction of heat load on humans attending the event in question [1
The aim of this study is to propose a methodology that can be used as a basis for future decisions about location, time of year and time of the day for specific sport events. Furthermore, to create a method to quantify general and specific conditions for different kind of sports e.g., road races or wind influenced sports [9
]. Another objective is to define short term conditions assessment and procedures to generate recommendations and tools for delaying, or, in extreme conditions, canceling, sport events. The methodology that is presented here does allow for the identification of time periods of the year, which are appropriate or inappropriate in the context of human thermal comfort, for the timely design of the appropriate countermeasures that are necessary to avoid casualties. At the same time, it is intended to provide the methodology to enable planners and responsible persons to run a similar analysis themselves. In contrast to earlier studies on similar topics, the research that is presented here not only is relying on a quantification of individual parameters influencing human-biometeorology, e.g., air temperature (Ta) on a coarse temporal resolution, but on the analysis of temporal variability and sensitivity of two complex thermal indexes (Physiologically Equivalent Temperature (PET) and modified Physiological Equivalent Temperature (mPET)) for a long period of meteorological data in 3 h temporal resolution. The methodology was designed to obtain results that may assist in the early stage of planning different sporting events all over the world. The method is described in detail to allow for the planning committees to reproduce the analysis for their local conditions to obtain quantitative results for their specific location. The results are presented in graphs, which are designed in a way that can be understood easily by non-specialists in the field of thermal human-biometeorology.
4. Discussion and Conclusions
Based on the results, it can be concluded that quantifications and an integral analysis of meteorological conditions for the selection of periods, when sport events may take place over the year do require meteorological input data covering a long period of time of at least 30 years (as recommended by the WMO) in high temporal resolution (<=3 h). Analysis that is based on monthly resolution and average values cannot provide appropriate information. While a long time period is required to provide statistical stability, the temporal resolution should allow for an identification of the beneficial and less beneficial times of the day.
In times of global climate change [24
] and urban areas being affected the most, it should be stated that most recent data should be used in order to account for changing frequency and intensity of heat waves and the recent development of the urban canopy influencing the urban heat island effect [14
When comparing Figure 7
and Figure 8
to Figure 9
, one can find that the conditions causing thermally uncomfortable or even stressful conditions, namely heat stress, cannot be quantified based on air temperature only. This is in quite good agreement to other studies [5
]. Ta is only one of the constituent environmental parameters affecting a human body’s energy balance and therefore it cannot represent the human thermal perception with enough precision [17
]. The human thermal perception is based on the human energy balance influenced by integral effect of air temperature, air humidity, wind speed, and radiation fluxes [15
]. The applied thermal indices PET and mPET allow for this quantification [7
]. The presentation of the results in terms of frequency diagrams that are based on thermal comfort classes facilitates the visualization of the conditions throughout day and year as well as their interpretation [20
]. From the Figure 7
and Figure 8
, it can be concluded that thermal stress in terms of heat stress could be significantly reduced by either moving the date of the event or by carefully setting the time of day. Even in the hottest time of the year, which is found to be the last decade of July, as well as the first two decades of August (compare to Figure 3
and Figure 4
), comfortable conditions can be met in the early morning or late afternoon hours.
While this study is mainly focused on visitors originating from Central Europe, it can be considered to be representative for people originating from other regions but with similar thermal climatic conditions. It can further easily be adopted for visitors from other continents or climatic regions by using a different assessment scale that is more representative for the corresponding climatic region, e.g., the classification for Israel [26
] or Taiwan [27
The current study presents some limitations that need to be considered. Readings from an individual meteorological station can be hardly representative for a whole city or urban area, like Tokyo. All of the input parameters to the thermal indices as well as the indices themselves are modified significantly by the urban environment and show strong variation in short distances of few meters [28
]. However, the general background conditions and the temporal variation in day and year can be seen from the readings and for keeping the study simple only one station was used. This is intended to facilitate reproduction of the results prior to other events. If both, know-how, as well as input data is available, the results can be improved by considering the actual local conditions using a building-resolving urban climate model, e.g., the SkyHelios model [29
This study describes an approach to determine and assess the conditions that foreign athletes and visitors attending sport events are facing. The approach does provide quantitative results that are based on human biometeorological methods. The intention of the authors is not to prove a specific location unsuitable to host a sport event but rather to provide decision makers with a useful methodology to assess the prevailing conditions and timely take action in order to allow for a safe participation for athletes as well as spectators. Being able to accurately predict climatic conditions does enable the responsible persons to take the most effective countermeasures on time and safeguard all attendees’ health.