明天天氣如何?
今晚鋒面會掠過臺灣，這時不只是北部，連中南部也有降雨發生，並且伴隨著大陸冷氣團的降溫和強風，變得又濕又冷，並延續到週一上班日。這波的強度比二月的寒流弱一些，但由於近期回暖，還是相當有感。家中有年長者幼童或慢性病患者務必留意保暖，今天也可以開始準備冬衣了。
這波冷氣團氣溫最低的時間預測落在週一的晚間到週二清晨，一方面是冷空氣最強，另一方面鋒面通過後乾空氣移入，雲量減少後輻射冷卻也快速增強，預測北部市區低溫大約在12-13度，中南部的沿海空曠地區也有機會出現類似的低溫。至於高山是否有機會降雪，目前看來只有在週一晚上到週二清晨氣溫比較低，也還有一些水氣殘留，想賞雪的朋友可以到合歡山之類的高山碰碰運氣，但時間相當短暫，到了週二白天冷氣團減弱，加上天氣轉晴，降雪的機會就越來越低了。而平地的天氣也好轉，除了迎風面山區還有短暫陣雨外，大多是晴朗日夜溫差大的天氣，雖然近山區清晨還是有局部較低溫，不過時間比較短暫，白天氣溫會一天比一天高。目前看來好天氣可望持續到下個週末。
而空氣品質方面，雖然今天南下的東北風有挾帶些許境外污染，但濃度比前一波低了不少，目前只有北部沿海臭氧較多，另外中南部內陸處於背風面，擴散條件不佳
，都有局部亮起代表對敏感族群不健康的橙燈。到了今晚隨著鋒面的降雨和強風，各地的大氣污染物可望被帶離，空氣品質就會逐漸改善。不過由於下週天氣都大致穩定，懸浮微粒又會開始累積，呼吸道敏感的朋友要多留意後續的空氣品質預報了。
以上氣象由天氣風險 / 李至晟 提供
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The log-periodic antenna as known as LPDA is a wideband directional antenna that provides gain and directivity combined over a wide band of frequencies.
Both Log-Periodic Antennas and Yagi antennas are high gain directional antennas. The main difference between these antennas is that Log-Periodic Antennas support wider frequency bandwidths and are physically much larger than Yagi antennas.
The log-periodic dipole array typical VSWR is 2:1 and operates over a much wider bandwidth and will have a lower gain for an equivalent number of elements.
In terms of its specification, a typical log periodic antenna might provide between 3 and 6 dB gain over dipole for a bandwidth of 2:1 while retaining a VSWR level of better than 1.3:1. With this level of performance, it is ideal for many applications, although a log-periodic antenna will be much larger than a Yagi of an equivalent gain.
EMC/EMI pre-compliance test antenna.
Very high gain over the full frequency range.
Meets latest EMC standards up to 7GHz.
Suitable even for immunity measurements
