Longyearbyen UHI experiment, April 18, 2008

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Longyearbyen April 18, 2008 12:01 hr (not corrected for summer time), looking WNW from the northern end of the lake Isdammen (see map below). The sky was almost clear. The wind was weak from Northwest, 2-3 m/s. The large building in the distance to the right is the main hangar at Svalbard Ariport. Compare with map below.


The general weather situation, measurement equipment and measurement route

The air temperature was about -20oC, and the wind weak from northwest, 2-3 m/s, but with local deviations (see map below). The sky was almost clear. The ground surface was covered by snow. The nearby fjord was ice free, with the exception of the innermost 1000 m, which was filled with ice. A shielded thermistor was attached to the roof of a car (c. 1.5 m above terrain), and temperatures were logged at 2 sec. intervals. The time given in the diagrams below are not corrected for summer time. The measurements were carried starting at Svalbard Airport in the upper left of the map below, driving southeast along the coast to the town, making a roundtour here, before proceding southeast into the lower part of the large valley Adventdalen. 

Longyearbyen is the worlds northernmost town and is located at 78o17'N 11o20'E, in central Spitsbergen . The present number of inhabitants is 2,001 (January 1, 2007). There is no official meteorological station located in Longyearbyen at the moment. The official meteorological station is located at the airport, about 4 km northwest of Longyearbyen, close to the coast (see map below).  


Topographic map showing Longyearbyen and Svalbard Airport (Svalbard Lufthavn). The red line shows the measurement route April 18, 2008, starting at the Airport and ending in the lower part of the valley Adventdalen to the southeast. In between, a detour was made in the central part of the town as shown. The wind was weak, 2-3 m/s, from northwest, but with local deviations (blue arrows). The fjord was ice free, except for the innermost 1000 m, which was filled with ice. The map section measures c. 11 km west to east.



Result of temperature measurements along the route Svalbard Airport - Longyearbyen -Adventdalen, April 18, 2008. The official Svalbard meteorological station is located at the airport. Se map above for reference. Time (not corrected for summer time) is given in hh:min:ss format along the x-axis.


Interpretation of results

The whole area was snowcovered. The Parts of the route were sunlit, while others were in topographic shade. The investigation was carried out shortly before solar noon. 

The registered air temperatures show an overall falling trend towards SE along the main measurement route. Near the airport, where the official Svalbard meteorological station is located, air temperatures are relatively high (about -6.7oC), which is interpreted as the result of the onshore airflow from SE across the ice free fjord. Further towards SE, this local warming effect diminishes inland, and colder air (about -8.5oC) in the valley Adventdalen dominates. The temperature difference between the Airport and Adventdalen is about 2oC, representing the open water effect (OWE) at this particular time. The OWE is reduced compared to situations with southeasterly air flow (see e.g. the experiment 20080331). In between the Airport and Adventdalen, a local heat island effect of the town Longyearbyen is weekly seen. The maximum UHI effect appears to be about 1oC at the time of the experiment, which may be partly explained with the relatively small wind velocity in the Longyear valley.

The existence of an urban heat island effect in a relatively small settlement as Longyearbyen may come as a surprise. This is, however, not the first time this has been observed in the Arctic; see, e.g., Hinkel et al. 2003.