The seventh International Conference on Urban Climate, 29 June - 3 July 2009, Yokohama, Japan
BIOMETEOROLOGICAL SITUATIONS IN DIFFERENT SUBWAY SYSTEMS *
Benjamin Steiling & Andreas Pflitsch Department of Geography, Ruhr-University of Bochum, Germany Wilfried Endlicher & Meike Schwabe Department of Geography, Humboldt University zu Berlin, Germany
1.
INTRODUCTION
Within the framework of a project dealing with various climatologic questions concerning different subway systems all over the world, the assessment of bioclimatologic aspects is of special interest. Regarding the fact that the ventilation of lots of underground systems is mainly passive and thus forced by the movement of arriving and departing trains, and natural processes of air exchange, the occurrence of situations of thermal discomfort to the subway users seems to be very likely. Earlier temperature measurements made in the subway of NYC showed us that besides air temperature, other factors have to be considered in order to prove the occurrence of such situations of discomfort or stress to the human organism According to HUPFER (1996), atmospheric radiation, air pollutants, and other meteorological parameters like relative humidity and wind speed have a big impact regarding the human well-being. Thinking of an underground system like a subway station, radiation is reduced to thermal radiation emitted from walls, the floor, the ceiling and the trains and the heat emitted from air condition of lots of workrooms. Regarding air pollutants, it is necessary to distinguish between different natural and unnatural substances in the air. This field can be of high importance as the underground environment provides only restricted ventilation. Other factors of interest would be the internal human heat production that differs between different individuals and insulation effects of clothing. The human body always aims at maintaining an equilibrium core temperature of 37°C and an average skin temperature of about 33°C (HUPFER, 1996). If these equilibriums cannot be established because the environment is either too hot or too cold, the person experiences thermal discomfort. 2.
METHODOLOGY
Within different scientific projects during the last years, the thermal situation inside different subway systems in the USA (NYC, Washington DC) and Europe (Dortmund, Munich, Newcastle, Berlin) has been investigated intensively. In the following we will have a more intense look at the subway systems of NYC and Berlin. In order to obtain similar conditions for a comparison these systems, which date from the beginning of the 20th century and have been considerably extended since then, were chosen. Both are comparatively large subway-systems, in which at least the topmost platform of the observed station lies directly below the street surface and is effectively ventilated through the entrances and gratings. The NY subway has a higher density of traffic and longer trains as the Berlin subway. Whereas in New York the subway is operating during the whole night, this is the case only during the weekends in Berlin. Both systems have very little active ventilation. It is important though that New York lies 12 degrees of latitude south of Berlin. The temperature measurements were made at irregular intervals throughout the year simultaneously – that means on the same days - in both subway-systems.. For selected sections on different subway lines the maximum air temperature for every station, respectively every platform was determined and related to the outside air temperature. 3.
FIRST RESULTS
The temperature measurements taken in both systems between April 2008 and May 2009 showed significant differences between outside air temperature and air temperatures in the stations. These differences reached up to 25 K in New York City, up to 15 K in Berlin. Moreover, air temperature varies to an amazing extent inside the station itself (up to 20K in NYC). Within the subway station, maximum air temperatures of up to 38°C were recorded in NYC in summer; in Berlin we have measured a maximum of 31°C. But even in winter we could * ∗
Corresponding author address: Andreas Pflitsch, Ruhr-University Bochum, Dept. of Geography, Workgroup: Cave & Subway Climatology, 44780 Bochum, Germany, email:
[email protected]
The seventh International Conference on Urban Climate, 29 June - 3 July 2009, Yokohama, Japan
investigate temperatures inside the stations of up to 25°C in NYC and up to 20°C in Berlin. The highest temperatures were found on the lowermost platforms of three-storey stations in New York City. As here are no direct connections to the outside, air exchange is limited and cooling is clearly constricted. The overheating of both systems was evident for all seasons except of spring, here especially the air in the European one, was sometimes cooler than the outer atmosphere. The measurements prove that enormous thermal loads exist for passengers inside the subway stations, especially in the system of New York City. These are not only due to the prevailing uncomfortably high air and radiation temperatures but furthermore to partly extreme differences over short distances. Differences mainly occur with the change from the atmosphere outside to the one inside the station, between different levels inside the station, and when entering or leaving equally air conditioned trains. In Berlin the results show, however, that thermal load is less and comparatively occurs less frequently than in the NYC. 4.
CONCLUSION
It can be stated that passengers have to endure high to extreme thermal loads inside subway stations. It is not possible to protect oneself by choosing the respective clothes due to high differences of temperature between the air inside and outside the station as well as the thermal “jumps“ within the station. These loads are present in summer and in winter. Loads observed appear to be much higher in cities of southern latitudes – here in NYC than in northern cities like Berlin. The deeper the station below the surface and the less the air exchange between the outside atmosphere and the subway station the higher is the thermal load to the passengers as well. References Hupfer, P., 1996: Unsere Umwelt. Das Klima. (Our Environment. Climate), Stuttgart, Leipzig
