Miejska wyspa ciepła na tle naturalnego zróżnicowania termicznego obszaru położonego we wklęsłej formie terenu (na przykładzie Krakowa)

Urban heat island versus the natural air temperature diversity in an area located in a concave landform (using an example of Kraków)

Summary: The aim of the paper is to present the concept of urban heat island determination in the case of a city located in a concave landform, with Kraków as an example. The data used were daily values of minimum air temperature and the temperature at 00:00 UTC from the period 1991-1995 from the following stations: Kraków-Botanical Gardens, Kraków-Balice, Garlica Murowana, Miechów, Igołomia, Libertów and Gaik-Brzezowa (Fig. 1). Mean annual values of the chosen thermal characteristics (Table 1) show that the highest temperatures are observed at the stations in the Wieliczka Foothills (Libertów and Gaik-Brzezowa). Mean monthly values of the differences in minimum air temperature and the differences in the air temperature at 00:00 UTC between the non-urban stations located in the river valley (Kraków-Balice and Igołomia) and at the hilltops (Gaik-Brzezowa, Libertów in the south and Garlica Murowana and Miechów in the north) prove that in the southern part of the city, on the Wieliczka Foothills slope, the temperature inversion prevails all year long, with higher intensity in the warm half-year than in the cold one, while on the Kraków Upland slope, in the northern part of the city, the differences are rather small and show mainly normal stratification (Fig. 2). On the Foothills' slope the inversions are noted at about 60% of nights in a year, while on the Upland slopes normal stratification occurs during 49,6-74,6% of the nights (values differ depending on the pair of stations compared) (Tables 2 and 3). The minimum air temperature differences on Foothills' slope most often have the value from the interval (-1.1)-(-4.0)°C, while on the Upland slope it is (-1.0)-1.0°C. In autumn and winter, the big differences (<-4°C) occur more often on the foothills' slope than in other seasons, while on the Upland slopes such differences are hardly noted (Fig. 3, 4, 5). Most probably, during 25% of the nights in a year, an inversion of about 100 m depth occurs in the vicinity of Kraków, during 28% of the nights the inversion of the depth up to 70 m takes place, during 14% of the nights a warm belt on a slope is observed but only in the northern part of the city, and during 33% of the nights there is a normal thermal stratification. The highest mean intensity of urban heat island (1.4°C) was connected with the inversion of the depth up to 70 m (Table 4 and 5). For the towns located in concave landforms, the intensity of the urban heat island should be determined separately for the city parts located at different relative height.

Słowa kluczowe: miejska wyspa ciepła, inwersja temperatury, rzeźba terenu, Kraków, dolina Wisły

Słowa kluczowe (w języku angielskim): urban heat island, air temperature inversion, terrain relief, Kraków, Vistula river valley

Prace Geograficzne, 2009, z. 122, s. 111-132.

Instytut Geografii i Gospodarki Przestrzennej UJ

ISSN 1644-3586

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