Threshold value of Benthic Pollution Index (BPI) for a muddy healthy benthic faunal community and its application to Jinhae Bay in the southern coast of Korea

For the determination of benthic community health criteria of a biotic index, Benthic Pollution Index (BPI), the faunal data on macrobenthic community of Deukryang Bay collected in 2012 were used. Each macrobenthic fauna was classified into 4 functional groups according to their feeding and life history strategies and BPI was calculated using the abundance of fauna for these functional groups. Amphipods were the dominant faunal group belonging to Functional Group (FG) II in Deukryang Bay during all seasons. The BPI value fluctuated seasonally from 55 to 61, and the overall mean value of BPI in the reference area was 60, which was estimated as the threshold value for healthy communities. We tried to use BPI as an assessment tool for macrofaunal community health status by categorizing the BPI values into 5 grades. If the BPI value of the community is more than 60, the health status of a macrobenthic community will be assessed as ‘Excellent’ (Grade 1) and as ‘Good’ (Grade 2), if between 40 and 60, as ‘Fair’ (Grade 3), if between 30 and 40, as ‘Poor’ (Grade 4), if between 20 and 30, and finally the health status of a community will be assessed as ‘Very Poor’ (Grade 5), if the BPI value is less than 20. This assessment tool using BPI was applied to macrobenthic communities in Jinhae Bay including the Special Management Area of South Korea. In Jinhae Bay, the FG IV containing a spionid species, Paraprionospio patiens was the most dominant group. The values of BPI in Jinhae Bay were very low and ranged from 11 to 23. The ecological health status of macrobenthic communities in Jinhae Bay was ‘Very Poor’ at more than 50% of sites, especially in summer.     

Forecast skill of the tropical intraseasonal oscillation in the NCEP GFS dynamical extended range forecasts

This study examines the forecast performance of tropical intraseasonal oscillation (ISO) in recent dynamical extended range forecast (DERF) experiments conducted with the National Centers for Environmental Prediction (NCEP) Global Forecasting System (GFS) model. The present study extends earlier work by comparing prediction skill of the northern winter ISO (Madden-Julian Oscillation) between the current and earlier experiments. Prediction skill for the northern summer ISO is also investigated. Since the boreal summer ISO exhibits northward propagation as well as eastward propagation along the equator, forecast skill for both components is computed. For the 5-year period from 1 January, 1998 through 31 December, 2002, 30-day forecasts were made once a day. Compared to the previous DERF experiment, the current model has shown some improvements in forecasting the ISO during winter season so that the skillful forecasts (anomaly correlation>0.6) for upper-level zonal wind anomaly extend from the previous shorter-than 5 days out to 7 days lead-time. A similar level of skill is seen for both northward and eastward propagation components during the summer season as in the winter case. Results also show that forecasts from extreme initial states are more skillful than those from null phases for both seasons, extending the skillful range by 3–6 days. For strong ISO convection phases, the GFS model performs better during the summer season than during the winter season. In summer forecasts, large-scale circulation and convection anomalies exhibit northward propagation during the peak phase. In contrast, the GFS model still has difficulties in sustaining ISO variability during the northern winter as in the previous DERF run. That is, the forecast does not maintain the observed eastward propagating signals associated with large-scale circulation; rather the forecast anomalies appear to be stationary at their initial location and decay with time. The NCEP Coupled Forecast System produces daily operational forecasts and its predication skill of the MJO will be reported in the future.     

公元1840年以来东亚夏季风降水变化—— 以中国和韩国的树轮记录为例

根据中国和韩国3条树木年轮降水记录, 本文分析了过去160 a以来东亚夏季风降水的变迁历史. 统计分析表明, 年际间中国和韩国季风降水不存在线性相关, 而在10 a尺度上则表现出同步变化的趋势. 1860~1890, 1910~1925, 1940~1960年是3个降水量较多的时段; 1890~1910, 1925~1940, 1960~1998年, 则是3个降水量较少的时段. 3条降水重建序列均揭示1920年代中期东亚夏季风降水快速由多转少. 同时树木年轮季风降水重建序列也被基于中国历史文献记载所划分的旱涝指数和韩国雨量记录所证实.