Meteorological observations at Syowa Station in 2015 by the 56 th Japanese Antarctic Research Expedition

This report describes the results of meteorological observations at Syowa Station from February 1 st, 2015 to January 31 st, 2016, carried out by the Meteorological Observation Team of the 56 th Japanese Antarctic Research Expedition (JARE-56). The observation methods, instruments, and statistical methods used by JARE-56 were almost the same as those used by the JARE-55 observation team. The operation to replace the surface observation system in Syowa station was carried by JARE-55, JARE-56, and JARE-57. In this operation, JARE-56 installed an anemometer, thermometer, hygrometer, and snow cover meter and operated the new surface observation system as test operation. Remarkable weather phenomena observed during the period of JARE-56 are as follows. 1) The snow depth was considerably large in 2015. The number of blizzards that attacked Syowa station was 29. This number was higher than the average for the period from 1981 to 2010 (24.6) and contributed to increase snow depth and to keep it large. Especially, the snow depth increased 50 cm during the blizzard from July 17 th to 19 th. Thus the snow depth reached 179 cm on July 31 th and August 30 th and 185 cm on September 25 th. These records updated the maximum snow depth of the month in July, August, and September. 2) Monthly mean temperatures in the lower stratosphere during the periods from May 2015 to August 2015 and from October 2015 to January 2016 over Syowa Station were almost lower than normal. The monthly mean air temperature on mandatory pressure level from 100 hPa to 40 hPa in May 2015 updated the lowest record in May. The monthly mean air temperature at the standard pressure level from 175 hPa to 125 hPa in January 2016 updated the lowest record in January. 3) The total ozone over Syowa Station was often less 220 m atm-cm, which was a measure of the ozone hole from middle-August to middle-December. The monthly mean of the total ozone amount in December 2015 updated the second lowest value in December. The total ozone in December 2015 kept lower value compared to the recent ten years in December, and the UV-index 12.7 recorded on December 1 st was the highest value since the start of observation.