Thermoisopleth diagram

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The thermoisopleth diagram is a climate diagram that shows the daily curves of air temperature in one place over the course of a year. It makes both the daily and the annual course of the air temperatures in this place visible and is suitable, among other things, to determine whether there is a seasonal climate or a time-of-day climate. The temperature amplitude of the year also indicates the geographical location - just like a normal climate diagram - and contains information about the type of climate, such as maritime or continental climate . In contrast to the normal climate diagram, a thermoisopleth diagram can be used to read off the nocturnal lowest and daily highest values ​​of the temperature as well as all the temperature values ​​measured in between during the day.

Isopleth and isothermal diagrams go back to Alexander von Humboldt . Carl Troll took up the form of representation of the thermoisopleth diagram in 1941 and 1943.

construction

Belém thermoisopleths : tropical daytime climate . Rapid temperature rise after sunrise, cooling by the midday rain , then very slow dropping after sunset by the moisture-related natural greenhouse effect .
Thermoisopleths of Irkutsk : highly continental seasonal climate

In the heading of the thermoisopleth diagram is the place name or name of the meteorological station with the details of the coordinates and the height above sea level . The diagram is divided as follows: On the right-hand axis are the first letters of the twelve months of the year. In the northern hemisphere, the year starts with January. For the southern hemisphere, July can alternatively be selected as the first month, so that December and January are the summer months in the middle. Since there is no winter in the tropics , the year can either start with January or with July. The 24 hours of a day are on the vertical axis from top to bottom.

The air temperature measured at many times during the day is recorded, with the mean values ​​of the hourly temperatures of the day serving as the basis. In the diagram, neighboring points of the same temperature are connected with lines, the so-called isopleths , similar to the contour lines on a topographic map. For the sake of clarity, the different temperature ranges are subdivided by means of color highlighting and some isopleths, usually printed in bold, are labeled.

In addition, other information can also be accommodated in a thermoisopleth diagram. For example, dash-dotted lines indicate the time of sunrise and sunset at extra-tropical stations ; in the polar zones, however, the duration of polar day and polar night . If the station is between the tropics , vertical dashed lines indicate the zenith of the sun. However, the horizontal dashed lines at 6, 12 and 6 o'clock only serve to facilitate reading.

interpretation

The course of the isopleths is decisive when interpreting the diagram. If this is almost parallel to the time axis (vertical), it can be concluded that the temperature changes only slightly during the day, while greater fluctuations take place over the course of the year. That is why one speaks here of a thermal seasonal climate . If, on the other hand, they run largely parallel to the monthly axis (horizontal), it is exactly the opposite: The greatest temperature fluctuations take place during the day and night, while the temperatures remain almost constant throughout the year. If so, one speaks of a time of day climate . Double elliptical isopleths ("lying eight") suggest that the zenith stage has passed twice, as only occurs in the inner tropics . Circle-like isopleths mean both diurnal and seasonal temperature differences ( moderate latitudes ).

The isopleth density is an indication of the strength of the fluctuation, whereby the following applies: the more isopleths there are, the greater the fluctuation in temperature, of course.

literature

  • Joachim Blüthgen and Wolfgang Weischet : General climate geography . 3. Edition. de Gruyter, Berlin, New York 1980, ISBN 3-11-006561-4 , sections 3. Daily and annual cycle as well as horizontal distribution of air temperature and 4. Temperature fluctuations, variability, extreme values , p. 140-147 .

Individual evidence

  1. ^ Weather dictionary - amplitude. In: wetter.net: Everything about the weather - Franzy Polak's weather dictionary. Retrieved October 14, 2016 .
  2. ↑ Wolfgang Latz: Diercke Geographie, Westermann 2007, ISBN 978-3-14-151065-2 . Pages 110 and 522
  3. ^ Isopleth diagrams. In: Spektrum.de Lexicon of Geography. Retrieved January 12, 2017 .
  4. ↑ Alexander von Humboldt. Humboldt-Gesellschaft, accessed January 12, 2017 : "He [Alexander von Humboldt] introduced the isotherm method and was the creator of the first isotherm map."
  5. ^ Hermann Lautensach: Carl Troll - A researcher's life . In: Geography . tape 8 , no. 4 , December 1959, p. 247 (Lautensach gives as a work in which Troll took up the thermoisopleths: Studies on the comparative geography of the high mountains of the earth. In: Bonner Mitteilungen. Issue 21, 1941).
  6. ^ Joachim Blüthgen: General climate geography . tape 2 . Walter de Gruyter, 1980, ISBN 978-3-11-006561-9 , p. 142 ( google.de [accessed October 7, 2018]).
  7. ↑ Wolfgang Latz: Diercke Geographie, Westermann 2007, ISBN 978-3-14-151065-2 . Page 522
  8. ↑ [1]