关键词: 相似预报方法, 云量预报, 逐步过滤, 相似离度

Abstract:

Cloud is a common and important weather phenomenon. The prediction of cloud cover is one of difficulties in weather forecast. In this paper, according to the analog forecast principle and analogue deviation criterion, based on ERA-Interim reanalysis data, T639 numerical forecast products and cloud cover data at 109 meteorological stations in Shanxi Province from 1980 to 2013, the most closely related forecast factors with cloud cover were selected and combined, firstly. Then, the stepwise analog filtering scheme with three-layer nested grids and five-level filtering were designed, On this basis the back substitution forecast of cloud cover in 1-10 days were done in Shanxi Province from 2010 to 2013. The results show that the forecast effect of low cloud cover by the stepwise analog filtering scheme was better than that of total cloud cover. The average accuracy of forecast error within 10 percent for 1-10 days low cloud cover was from 71.6% to 74.4%, and the forecast error of low cloud cover was less than 20 percent in spring, autumn and winter, while that was relatively larger in summer from June to August. The average accuracy of forecast error within 30 percent for total cloud cover in 1-10 days was from 54.9% to 62.8%, the forecast error in most months was less than 30 percent, but it was relatively larger from July to September. The forecast accuracy of total cloud cover and low cloud cover decreased slightly with the increase of forecast days, which had important reference significance for short-term and medium-term forecast of cloud cover in Shanxi Province.

Key words: analog forecast method, cloud cover forecast, stepwise filtering, analogue deviation