1.5.2. Barrow Station Climatology

The 21-year station climatologies are an important record for the interpretation of measured values of aerosols, trace gases, atmospheric turbidity, solar radiation, and in the long-term changes in the records themselves. The records also serve to outline periods of local contamination.

In Figure 1.1 wind roses of hourly average resultant wind direction and speed at BRW are presented in 16 direction classes and 4 speed classes. Winds from the “clean air” sector, north-northeast to southeast occurred 48.5% of the time in 1996 and 63.5% in 1997 as compared to 61.9% for the 19-year period from 1977 through 1995 (Figure 1.2). Wind speeds that were greater than 10 ms^-1 in 1996 (6.9%) and 1997 (7.9%) were less frequent than the 19-year climatology (11.7%). The average speed of 5.1 ms^-1 in 1996 (Table 1.8) was the second lowest average while the 5.0 ms^-1 in 1997 was the lowest average in the 21 years at the station.

Fig. 1.1. Wind roses of surface winds for BRW for 1996 (top) and 1997 (bottom). The distribution of resultant wind direction and speed are given in units of percent occurrence. Wind speed is displayed as a function of direction in three speed classes.

Fig. 1.2. Wind rose of surface winds for BRW for 1977 through 1995. The distribution of resultant wind direction and speed are given in units of percent occurrence for the 19-year period. Wind speed is displayed as a function of direction in three wind classes.

TABLE 1.8. BRW 1996 and 1997 Monthly Climate Summary

Instrument heights: wind, 10.5 m; pressure, 9.5 m (MSL); air temperature, 2.2 m; dewpoint temperature, 2.0 m. Wind and tempera-ture instruments are on a tower 25 m northeast of the main building.

*Maximum and minimum values are hourly averages.

The average air temperatures of –10.7°C in 1996 and –11.2°C (Table 1.8) in 1997 were both warmer than the 19-year average of -12.5°C. New record high temperatures were recorded in 1996 during the months of June (23°C) and November (1°C) while March tied its record high (-1°C). June 1996 was the warmest ever recorded in the 21-year history of the observatory, and June 1997 set a new record low temperature (-12°C). The barometric pressure for 1996 was 1.8 hPa above the 19-year average while the average for 1997 was close to normal. February 1996 (-40°C), April 1997 (-36°C), and November 1997 (-24°C) set new record lows. The summertime precipitation was measured at 41 mm in 1996; this was below the long-term average of 63 mm, while the 65 mm measured in 1997 was slightly above normal.

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