Trends in cloud amount and radiative fluxes at Syowa Station, Antarctica

Variations of cloud amount and radiative fluxes are a matter of discussion related to the recent climate change in the Arctic and Antarctic. It is also of great concern related to “from dimming to brightening” recently found. Discussions based on satellite data had been conducted; however, no solid results are obtained from the surface station data for a long term in the recent.At Syowa Station, Antarctica, meteorological observation has been continued for nearly 50 years. During this term, an annual mean cloud amount showed a gradual increase at a rate of 0.014/yr. Radiation budget was observed since 1991 as one of the BSRN stations. Trends of monthly mean radiative fluxes were compared with those of cloud amount and conformable relations were seen during the period from 1991 to 2004. A cloud radiative forcing was estimated. In December, a downward trend in net longwave and net total appeared, while an upward trend in net shortwave was seen, and all corresponded to the decrease of cloud amount in this month. On the other hand in June, an upward trend in net longwave forcing was seen, corresponding to the increase of cloud amount. On an average, cloud radiative forcings at Syowa Station represented those of Antarctic costal stations near sea ice area.