Meteorological observations at Syowa Station in 1999 by the 40th Japanese Antarctic Research Expedition

Abstract

This report presents the results of meteorological observations at Syowa Station from February 1, 1999 through January 31, 2000, carried out by the 40th Japanese Antarctic Research Expedition (JARE-40). The meteorological observation method, measuring instruments, means to compile statistics, and other aspects of the work were almost the same as those used by the 39th Japanese Antarctic Research Expedition. Remarkable weather phenomena during the wintering period are as follows: 1) In the surface weather observations, in July, December and January, the atmospheric temperature was significantly lower recorded compared to normal average years, and also the atmospheric pressure was significantly lower in May, October, December and January. The lowest sea level pressure, 932.1hPa was recorded during a severe blizzard on October 5 for the JARE-40 period (the 2nd lowest in history). There were 25-blizzards of which 4 were class A, 10 class B, and 11 class C, the same level as in a normal year.2) As a result of total ozone observation, the large-scale ozone hole was observed, as in the previous year, and the monthly average amount of total ozone in November recorded the lowest ever. Then, the ozone hole disappeared in mid-December, however, the recovery of the total amount of ozone was the slowest in years.3) Because, the temperature rise for the stratosphere was delayed, record-low monthly average temperature was observed in the lower stratosphere in springtime.4) By observing with an aerosol sonde, we observed cloud particles of polar stratospheric cloud (PSCs), which are thought to be the most important cause of ozone holes formed in the Antarctic lower stratosphere in springtime.5) In observation of surface ozone concentration, the rapid decrease of surface ozone concentration has been observed continuously, since JARE-38 started this observation.