Warunki klimatyczne i bioklimatyczne terenów rekreacyjnych Kielc na tle klimatu centrum miasta w trakcie epizodów pogody gorącej
Climatic and bioclimatic conditions in the recreation areas of the city of Kielce during hot weather as compared to the climate of the city center

Summary/Abstract: Thermal and biothermal conditions vary among different land use areas in a city. Recreationalareas e.g. parks and the surroundings of reservoirs are cold islands within the urban heat island. Relativelylow air temperature in recreation areas is especially important during hot weather which maycause heat stress in humans.In this study, the variability of the thermal and biometeorological conditions was determined forthe city of Kielce and its outskirts during hot (Tmax > 25.0°C) and very hot (Tmax > 25.0°C) days.Special attention was paid to thermal and biothermal conditions in the recreation areas of Kielce, namelyS. Staszic Park, the surroundings of the Kielce Reservoir, the nature reserve in a former Wietrzniaquarry and a summit of the Dymińskie Range. Recreation areas where heat stress was the lowest inThe differences between hourly air temperature and WBGT index (wet bulb globe temperature) inthe downtown and recreation areas of Kielce as well as city’s outskirts were counted. The occurrencefrequency of the WBGT classes relating to acceptable physical activity was determined as well. Thedata comes from selected hot and very hot days in 2000, 2001 and 2003 as well as all the hot and veryhot days in the 2012–2015 period.The downtown of Kielce was 0.9°C warmer than the outskirts of the city. It is, however, the meandifference and it varied throughout the day. At night and at dawn, the downtown was 2.0–2.2°C warmerthan the countryside. In the morning the countryside was usually warmer than the downtown asthe air temperature rose faster there in comparison with the built-up area. It is an effect of the screeningof solar radiation by high buildings within the city.Most of the examined recreational areas of Kielce were colder than the built-up area of the downtown.The biggest air temperature difference was that one between the center of the city and the surroundingsof the Kielce Reservoir. The surroundings of the reservoir were 1.4°C colder than the downtown.Only the former quarries are not suitable for rest during hot weather. Their bottoms are generally warmer than the downtown and hazardous heat stress can occur there during hot and very hot days. The variability of WBGT turned out to be lower than that one of the air temperature. It resultedfrom higher humidity and more frequent sultry weather in recreation areas in comparison with thedowntown. Therefore, we should limit our physical activity also in the recreation areas of the city ofKielce during hot weather.

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