两种不同初始场对太阳辐射模拟效果的影响

Impact of Differences Between the NCEP and ECMWF Reanalysis Data on Solar Radiation Simulation

利用2010年1,4,7和10月ECMWF和NCEP再分析资料作为初始场和边界条件,应用辐射模式系统WRF-SES2模拟了北京观象台的总辐射、散射辐射和直接辐射,并与观测值进行对比,重点分析了模式初始场云量差异对辐射模拟的影响。结果表明:(1)1,4,7和10月多数时段总辐射模拟值较观测值偏大,散射辐射模拟值较观测值偏小,总云量模拟值小于观测值,直接辐射误差分布范围较总辐射、散射辐射大。(2)多数时段采用ECMWF再分析资料作为初边值条件模拟(简称EC方案)的总辐射、直接辐射、散射辐射误差小于NCEP资料作为初边值条件模拟(简称NCEP方案)的误差,即EC方案模拟太阳短波辐射效果优于NCEP方案,这可能与ECMWF再分析资料中的云微物理量误差相对较小有关。(3)1月和4月总辐射模拟效果较好,平均绝对误差最小,其中1月两种方案误差分布范围最小,且介于-50~200 W·m-2之间,10月次之,7月稍差;1,4月和10月两种方案模拟误差较接近,而7月EC方案模拟的总辐射误差小于NCEP方案。(4)1月直接辐射模拟效果较好,4月和10月次之,7月稍差;除4月外,其他3个月EC方案模拟的直接辐射误差小于NCEP方案。(5)1月和10月散射辐射模拟效果较好,4月和7月稍差;4个月EC方案模拟的散射辐射误差小于NCEP方案。(6)EC和NCEP方案对总辐射、直接辐射和散射辐射的模拟准确率受初始场中云量模拟效果的影响较大,当总云量模拟误差较小时,总辐射的模拟误差亦相对较小。(7)在多云和有降水天气过程时,EC和NCEP方案模拟的太阳辐射误差较大,需要通过资料同化方法改进模式初始场,并对模拟结果做进一步订正。

Global,diffuse and direct radiation were simulated by WRF- SES2 radiation model system in Beijing urban area based on ECMWF and NCEP reanalysis data in January,April,July,and October 2010. The differences of solar radiation was put emphasis on simulation using the two kinds of reanalysis data and impacts of differences of total cloud amount on radiation simulation. The results showed that:( 1) Simulated values of global radiation in most of times are larger than the observed values and those of scattered radiation are smaller; simulation values of total cloud amount are less than the observed values; errors distribution scopes of direct radiation are larger than global and scattered radiation.( 2) In general,simulated errors of global,direct,diffuse radiation based on EC data in most of periods are less than those based on NCEP data because simulation errors of microphysical quantities of cloud using EC data are less than those with NCEP data.( 3) Simulation effects of global radiation in January and April are better,those in October take second place,those in July are worse. Namely average absolute errors in January and April are smaller and distribution scopes of simulation error are narrower,falling in between- 50 W·m- 2and 200 W·m- 2. Simulation effects of direct radiation are better in January,followed by those in April and October and results in July are worse. Those of scattered radiation are better in January and October,followed by those in April and July.( 4) Simulation accuracy of global,direct and diffuse radiation were obviously affected by simulation effects of cloud amounts in initial fields. When sky is cloudy and rain falls,simulated errors of solar shortwave radiation based on EC data and NCEP data are large and data assimilation in the initial field and corrections are required. We will improve simulation of solar shortwave radiation in the future research using data assimilation method,more accurate the atmospheric radiative transfer model,advanced cloud parameterization schemes and effective correction methods.