In 2002, a new system for measuring dissolved chlorofluorocarbons (CFC-11, CFC-12, and CFC-113: CFCs) in seawater was developed by the Climate and Marine Department, Japan Meteorological Agency (JMA). During the Ryofu Maru RF03-04 cruise in the western North Pacific in April and May 2003, CFCs concentrations measured by this system were compared with those measured by the Meteorological Research Institute's (MRI's) system that had been used for CFCs measurements in this region since 2000, using a common calibration scale and the same sampling protocol. The precisions of analysis by the MRI system, as determined from analysis of replicate samples, were 0.037 pmol/kg seawater (1.4%) for CFC-12, 0.049 pmol/kg (1.0%) for CFC-11 and 0.012 pmol/kg (2.3%) for CFC-113. The precisions of analysis by the JMA system were 0.008 pmol/kg seawater (0.4%) for CFC-12, 0.011 pmol/kg (0.2%) for CFC-11 and 0.012 pmol/kg (3.0%) for CFC-113. The no discrepancy in the concentrations of CFCs measured by the MRI and JMA systems was found at the 95% of significance level for these CFCs. These results suggest that if only the calibration scale were inter-compared, we could obtain comparable CFCs data in seawater.
Long-term changes in diurnal variation patterns of precipitation frequency were analyzed using visual data (ww) for 42 years (1961 to 2002) in Japan. The precipitation frequency relative to the daily mean was found to have increased in the nighttime and decreased in the daytime at a rate of the order of 0.01 per decade. This change was observed for all seasons and regions. A supplementary analysis based on hourly automated data on the AMeDAS network (1979 to 2002) confirmed the relative decreasing trend of daytime precipitation frequency, apart from some differences by regions and precipitation intensity. Changes in diurnal variation patterns were also found for vapor pressure and temperature, with a relative increase in nighttime values, although little change was detected for the diurnal variation patterns of relative humidity and cloud amount.
Previous studies suggested that solar activity may influence the El Niño/ Southern Oscillation (ENSO) cycle, such as in the modulation of the amplitude of the Tropospheric Biennial Oscillation (TBO). This study shows that the difference of the TBO due to the solar cycle is, in fact, derived from a difference in the association of the Indian Ocean sea-surface temperatures (SSTs) with the Pacific Ocean SSTs. High SSTs appear in the Indian Ocean following a warming in the Pacific Ocean during low solar activity (LS) from summer to winter. However, such a relationship is absent during high solar activity (HS). This difference in SSTs is related to the distribution of convective activity over the equator. Convective activity is more localized over the Pacific sector during HS, but more zonal and extending over the Indian Ocean during LS. Differences are also found in the vertical velocity in the troposphere. Up-welling over a warm SST region is connected to the stratosphere during LS, but limited within the troposphere during HS.
A possible mechanism suggested from this study is that the solar influence in the equatorial troposphere does not arise from a change in the ocean temperature, but originates from the equatorial stratosphere through changes in the meridional circulation. This circulation modulates the vertical extent of convective activity as well as the horizontal distribution along the equator.