雾与能见度数值预报诊断SW方案和FSL方案改进的研究及评估

为了提高雾与能见度的预报水平，对业务上常用的两种能见度诊断方案，即Stoelinga and Warner（SW）方案与Forecast Systems Laboratory（FSL）方案的改进进行预报试验，SW方案基于Gultepe方案考虑了液态水粒子数浓度对能见度的影响，FSL改进方案中利用了递减平均法对公式中用到的温度与露点温度进行订正，并用其重新计算公式中的相对湿度。基于山东省气象科学研究所逐时更新循环（hourly update cycle，HUC）业务模式输出结果，从2015—2016年选取10次雾天气过程，并详细分析了2015年11月13—14日这次雾天气过程的预报结果，比较了改进前后各方案对雾与能见度的预报效果，结果显示：在模式预报的雨水含量占总液态含水量比例较大的预报时效，改进后的SW方案对雾与能见度预报效果优于原始方案，在模式预报液态含水量接近0的预报时效，改进前后的SW方案对雾与能见度的预报效果相当；利用订正的温度与露点温度重新计算相对湿度，其平均绝对误差（mean absolute error，MAE）降低明显的预报时段，改进后的FSL方案对雾与能见度的预报效果大大提升。将两种改进后的方案相融合并进行预报试验，结果显示，综合对能见度与雾的预报效果，Combined Visibility（CVIS）方案要优于其他两种改进方案。

Research and evaluation of improved SW and FSL schemes for diagnosis and numerical simulation of fog and visibility

To improve the forecast of fog and visibility, prediction experiments are conducted to optimize the two operational diagnostic schemes for forecast of visibility, namely Stoelinga and Warner (SW) scheme and Forecast Systems Laboratory (FSL) scheme. SW scheme takes into account the impact of number concentration of liquid water particles on visibility based on Gultepe scheme. In the improvement of FSL scheme, the decaying averaging method is employed to correct the temperature and dew point and then the relative humidity is recomputed. Base on the simulating results from HUC (hourly update cycle) model of Shandong Institute of Meteorological Sciences, 10 fog processes are selected from 2015 to 2016, among which the forecast of the fog process from 13 to 14 November 2015 is analyzed in detail, and the forecast skills of fog and visibility between the original and improved schemes are compared. The results are as follows. 1) When the rain water content takes up a large proportion in the total liquid water content in the model forecast, the forecast skill of fog and visibility by the improved SW scheme is better than that by the original SW scheme, while when little liquid water content can be forecast by the model, the forecast skill of fog and visibility between the original and improved SW schemes are equivalent. 2) When the mean absolute error (MAE) of the relative humidity, which is recomputed with the corrected temperature and dew point, decreases notably during the forecast period, the forecast skill of fog and visibility by the improved FSL scheme is greatly enhanced. The improved SW and FSL schemes are integrated into one scheme named Combined Visibility (CVIS) scheme, and the results of experiments show the general forecast skill of CVIS scheme is better than that by the two improved schemes.