| 摘要: | 近年來，全球暖化議題成為世人關注的焦點後，北極海冰的融冰便成為科學家研究探討的對象。由於北極海冰的變化對氣候的改變具有高度的敏感性，它可以調節地表吸收太陽的能量，進一步影響海洋大氣間的動量、潛熱及化學組成，故針對北極海冰變化的監測，有助於瞭解氣候潛在因子變動之因果關係。據研究顯示，反照率正回饋現象、大氣可降水含量等均是影響北極地區氣候變化的重要因素；因此，本研究之主要目的係探討北極冰反照率正回饋作用，對北極地環流區可降水分佈的影響，以及瞭解此狀況與氣候變化的關係。 本研究分析所使用的研究材料概分為兩類，分別是搭載於美國國防氣象衛星計畫(Defense Meteorological Satellite Program, DMSP)上的SSM/I(Special Sensor Microwave/Imager)微波輻射計資料，以及美國環境預報中心(National Centers for Environmental Prediction, NCEP)和國家大氣研究中心(National Center for Atmospheric Research, NCAR)的再分析資料。由觀測資料發現，海冰面積在1989-1996年間，處於一個振盪平衡狀態，而在1997-2007年間，則處於冰反照率正回饋狀態。分析時係將分佈區域與氣候因子間的關係，作交叉性及綜合性的比較探討；在區域的分布上，本研究將研究區之北緯60到90度分為6個區域，並比較前述個時期之氣候因子在不同地域和季節的分佈狀況及因果關係。 依研究分析之結果顯示，在不同季節中，當反照率處於正回饋作用時，無論海洋或陸地區域之可降水含量在夏季時明顯增加；而冬季地域性的分析顯示，在海洋上的可降水受到正回饋作用，有增加的趨勢；惟在斯堪地納維亞半島和洛磯山脈地表上之可降水，則低於正回饋作用前，推斷可能原因係北極振盪(Arctic Oscillation, AO)在此階段處於負相位，造成寒冷氣流南下，帶走大氣中的可降水含量所致。 綜上顯示，北極地環流區之反照率正回饋作用對該區域之海冰面積、溫度及可降水含量的關係變化，產生明顯的影響性；並隨著近年來氣候暖化之影響，呈現劇烈變化，殊值持續觀測。 In recent years, after most of the focus of the world attention on global warming, the Arctic sea ice melting condition has become main research issue for scientists. Sea ice in the Arctic is very sensitivity to climate changes. It can help regulate the amount of incoming and insolation absorbed by the earth and exchanges momentum, heat, and chemical constituents between the atmosphere and the ocean. Therefore, monitoring for the changes of the Arctic sea ice will help us to comprehend the causation of climate change of potential factors. According to researches, the phenomenon of positive ice-albedo feedback and atmospheric precipitable water are important factors to affect climate changes in the Arctic region. Therefore, the main purpose of this study is to analyze how the positive ice-albedo feedback to affect the distribution of precipitable water on the Arctic Polar Cell. The research data used in this study has been divided into two categories, namely, the Special Sensor Microwave/Imager (SSM/I) microwave radiometer data that is onboard the Defense Meteorological Satellite Program (DMSP) satellite and the NCEP/NCAR reanalysis data. By the observation, sea ice area in the years of 1989 to 1996 was in an oscillatory equilibrium state, while the years of 1997 to 2007 was in a positive ice-albedo feedback state. On analysis that will discuss the relationship between the distribution of precipitation on the Arctic Polar Cell and climatic factors by comprehensive and comparative studying. In this study, we divided the distribution of precipitation on the Arctic Polar Cell into 6 areas in latitude from 60 -90 degrees, and compares the results with previous periods of climatic factors in different geographical and season distribution. According to the results of the analysis, in the different seasons, when positive ice-albedo feedback is active, both marine and terrestrial area of precipitable water increased significantly in the summer, and regional analysis shows that precipitable water has increased trend at marine in winter by positive ice-albedo feedback effect. However, precipitable water in the Scandinavia and the Rocky Mountains are less than before the period of positive ice-albedo feedback. The possible cause is that the Arctic oscillation system (AO) was in the negative phase at this stage, resulting in cold air southward and taking away atmospheric water vapor. To sum up the previous results, it shows that positive ice-albedo feedback in the Arctic Polar Cell has significant effected upon sea ice area, temperature, precipitable water, and with the impact of climate warming in recent years that is showing dramatic changes, thus, it’s a special issue that worth to observe consistently in the future. |
