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辐射参数化的变化对模式中期和月预报的影响
Impact of Changes in Radiation Parameterization on Model Medium-range and Monthly Forecasting
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摘要: 在T106中期数值预报模式和T63气候模式中进行了两种辐射过程参数化的对比试验。目前在这两个模式中用作对照积分的辐射方案(OPE)是ECMWF的早期业务方案，而新的辐射方案(NEW)是ECMWF 1989年5月2日成为业务的版本。试验结果表明，OPE高估了短波水的吸收，导致太大的短波大气吸收和地表太小的向下短波辐射；OPE还低估了长波辐射冷却和大气顶的向外长波辐射(OLR)；NEW增加了地表有效辐射能量和对流层总的冷却，产生了较大的湍流热通量，对流活动加强，降水量明显增加；NEW还使平流层温度偏暖得到矫正。业务平行试验的统计检验表明，NEW对4～7天中期预报有较显著的改进。Abstract: A comparison of two radiation parameterization schemes has been carried out in the T106 Medium-range NWP model and the National Climate Center’s climate model T63. The radiation scheme used for the control integration in the two models at present was the original ECMWF operational radiation scheme (OPE), and the new radiation scheme (NEW) was the version that became operational on May 2, 1989 in ECMWF. Results indicate that OPE overestimates the short-wave water absorptivity, which leads to too large short-wave atmospheric absorption and too small downward short-wave radiation at the surface; OPE also underestimates the long-wave radiative cooling and the outgoing long-wave radiation at the top of atmosphere (OLR). In NEW the radiative energy available at the surface and an overall cooling of the troposphere increase; large turbulent heat fluxes are generated; the convective activity is enhanced; and the precipitation clearly increases. The warm temperature bias in the stratosphere in OPE is corrected. The operational parallel statistical test indicates a more pronounced improvement to the medium-range forecast of 4—7 days.
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图 2 1997 年7 月T63 模式两种辐射方案预报和NCEP 再分析的月平均大气顶的向外长波辐射,(a)为NEW (b)为OPE (c)为NCEP 再分析(等值线的间隔为30 W°m -2)
图 3 1997 年7 月T63 模式两种辐射方案预报和NCEP 再分析的月平均感热通量(a)为NEW (b)为OPE (c)为NCEP 再分析(等值线的间隔为30 W°m -2)
图 4 1997 年7 月T63 模式两种辐射方案预报和NCEP 再分析的月平均潜热通量,(a)为NEW (b)为OPE (c)为NCEP 再分析(等值线的间隔为50 W°m -2)
图 5 1997 年7 月T63 模式两种辐射方案预报与NCEP 再分析降水的差以及NCEP 再分析的月降水量，(a)为NEW -NCEP (b)为OPE-NCEP (c)为NCEP 再分析
图 6 1997 年7 月T63 模式两种辐射方案预报与NCEP 再分析的100 hPa 月平均温度的差以及NCEP 再分析的月平均温度，(a)为NEW -NCEP (b)为OPE-NCEP (c)为NCEP 再分析
表 1 试验例子
表 2 新辐射方案(NEW)与业务方案(OPE)的比较
表 3 两种辐射方案的距平相关系数(上表)和均方根误差统计(下表)(分析为1998 年12 月2～21 日)
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