雷達接收的訊號中，除了真實的天氣訊號外，其中亦包含了許多非天氣現象的幹擾訊號，除了影響觀測與預報人員對天氣系統的詮釋與判斷外，對於下游應用產品的影響更是深遠。利用五分山雷達資料進行為期一年的主觀分析統計發現，地形（地面）雜波長時間存在雷達資料中，其他雜波發生的頻率相對較低，其中大範圍的海面回波（大於10 dBZ）發生頻率約為60%，而非正常傳播與幹擾回波發生的頻率約為8.0%。為進行長期的雷達雜波統計作業，本研究利用中央氣象局2003年1月至2003年6月五分山、花蓮、七股、墾丁四個雷達資料，以雷達觀測最低層的4個仰角（0.5、1.5、2.4、3.3度）進行統計分析。分析結果顯示，網連雷達之海面回波氣象均相當明顯。另外，五分山及七股雷達均存在大範圍的地形雜波。五分山雷達的地形回波位於雪山山脈山頂區域、大屯山系以及宜蘭南方之山區，而七股雷達則位於東北至東側的中央山脈區域，影響仰角可達3.3度以上。墾丁雷達在蘭嶼島區域，也有地形雜波的出現，其影響可達仰角2.4度。在利用統計結果進行地形雜波的濾除時發現，回波閥值與頻率選取，決定了地面雜波在地理上的分佈位置，也關係著地形雜波濾除的成效。初步測試結果顯示，在大於0 dBZ的回波閥值與15%頻率的條件下，可以有效去除地形雜波，而真實的天氣現象亦得以保留。

　　　　　Weather radars can detect both weather and non-weather scatters. The latter ones can contaminate radar observations and cause forecasters to misinterpret weather phenomenon. Moreover, contaminated radar data will have negative impacts on downstream applications and weather products. By subjectively examining one year of reflectivity data from Wu-Fen-San radar at the lower elevation angles, five types of clutter echoes, i.e., ground clutter, sea clutter, interference, anomalous propagation, and unaccounted-for echo, are identified. The ground clutter appears almost all the time, while other types of clutter occur less frequently. The frequency of sea clutter appears almost all the time, while other types of clutter occur less frequently. The frequency of sea clutter occurrence (for reflectivities greater than 10dBZ) is about 60%, and the occurrence frequencies for interference and for anomalous propagation echoes are about 8.0% each. Four lowest elevation angles ( i.e., 0.5, 1.5, 2.4, 3.3 degrees) of reflectivity data collected between January and June of 2003 from the four S-band Doppler radars of Center Weather Bureau are used to analyze clear-air echo statistics and beam blockage patterns for each of the radars. In the umbrella of Wu-Fan-San radar, widespread clutter exists at mountaintops of the Snow Mountain, the Da-Tuan Mountains and the mountainous area near south of I-Lian. Similar ground clutter was also found in other three radars’echo statistics. The influence of ground clutter can reach to 3.3 degrees in the central Mountain area for Chi-Ku radar and to 2.4 degrees In Lan-Yu Island for Ken-Ting radar. Sea clutter echoes are apparent for all radars, especially for Ken-Ting radar because of the low altitude where the radar’s antenna is situated. Both the geographic distribution and the removal of ground clutter are dependent on the choice of a good reflectivity and an occurrence frequency threshold. A reflectivity threshold of 0 dBZ and an occurrence frequency threshold of 15% are found to be reasonable in removing clutter while retaining weather echoes.