This paper demonstrates that an annular mode can be constructed from the combination of the North Atlantic Oscillation(NAO) and the Pacific/North American(PNA) patterns.The quasi-annularity,meridional dipole and verti...This paper demonstrates that an annular mode can be constructed from the combination of the North Atlantic Oscillation(NAO) and the Pacific/North American(PNA) patterns.The quasi-annularity,meridional dipole and vertical barotropy of the constructed annular mode resemble those of the Atlantic Oscillation(AO) pattern.It is also a dominant mode in terms of the variance contribution.Moreover,its temporal correlation with the AO is quite strong.This new annular mode has the advantage over the AO in that it incorporates a large portion of the PNA and makes the center of action in the Pacific stronger and more physically relevant than that of the AO.Or,more generally,it may be regarded as a physical mode unlike the AO.The results of this study also indicate the NAO-PNA perspective contains most of the information of the AO,whereas the AO perspective only contains about half of the information of the NAO-PNA.Consequently,the NAO-PNA perspective is regarded by the authors to be more comprehensive than that of the AO.展开更多
In this study, using the ECMWF reanalysis data, the possible linkage between the Pacific-North American teleconnection pattern （PNA） and the North Atlantic Oscillation （NAO） during boreal winter （December- Febru...In this study, using the ECMWF reanalysis data, the possible linkage between the Pacific-North American teleconnection pattern （PNA） and the North Atlantic Oscillation （NAO） during boreal winter （December- February） is investigated. The PNA and the NAO pattern are obtained by performing Rotated Empirical Orthogonal Function （REOF） analysis on an anomalous daily mean 300-hPa geopotential height field. The composite daily NAO indices show that the NAO indices are prone to be negative （positive） when the contemporary PNA indices are extremely positive （negative）. The correlation coefficients between the daily PNA and NAO indices also confirm that, indeed, there is a significant anti-correlation between the PNA and NAO indices. The correlation peaks at a lag of 0 days （meaning contemporary correlation）, and its value is 0.202. Analyses of a newly defined Rossby wave breaking index and diagnostics of the stream function tendency equation indicate that the anti-correlation between PNA and NAO may be caused by the anomalous Rossby wave breaking events associated with the PNA pattern.展开更多
To study the impact of climate change on Godthab(Greenland), temperature and precipitation gathered from the Global Historical Climatology Network (GHCN) were analyzed for patterns within 1866-2011. Both temperature a...To study the impact of climate change on Godthab(Greenland), temperature and precipitation gathered from the Global Historical Climatology Network (GHCN) were analyzed for patterns within 1866-2011. Both temperature and precipitation have experienced an overall increase throughout the past 146 years. Precipitation, however, has experienced a declining trend since 1985. North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) indices showed strong correlations with average annual temperature (R = ?0.6) and smaller correlations with annual total precipitation (R = ?0.2). There are moderate correlations between temperature, precipitation, and Southern-Oscillation Index (SOI). The positive phases of Pacific-North American (PNA) led to increased winter and spring precipitation. The climate mode’s influential strength on Godthab’s temperature and precipitation, vary seasonally. In contrast with global average temperatures, Greenland has not experienced a continual warming trend since the 1950s;30- and 10-year trends show a cooling period between 1965 and 1995. From 1866 to 2011, Godthab’s average annual temperature has increased by 1.9?C, and is anticipated to continue to warm in accordance with the global warming trend and the Arctic’s associated feedback mechanisms.展开更多
基金Foundation of Key Laboratory of Meteorological Disaster of Ministry of Education (KLME0702)LaSW Foundation of the Chinese Academy of Meteorological Sciences, National Key Basic Research and Development Project of China (2009CB421503)+2 种基金National Natural Science Foundation of China (40775033, 40940022)Chinese Special Scientific Research Project for Public Interest (GYHY200806009)Qinglan Project of Jiangsu Province of China (2009)
文摘This paper demonstrates that an annular mode can be constructed from the combination of the North Atlantic Oscillation(NAO) and the Pacific/North American(PNA) patterns.The quasi-annularity,meridional dipole and vertical barotropy of the constructed annular mode resemble those of the Atlantic Oscillation(AO) pattern.It is also a dominant mode in terms of the variance contribution.Moreover,its temporal correlation with the AO is quite strong.This new annular mode has the advantage over the AO in that it incorporates a large portion of the PNA and makes the center of action in the Pacific stronger and more physically relevant than that of the AO.Or,more generally,it may be regarded as a physical mode unlike the AO.The results of this study also indicate the NAO-PNA perspective contains most of the information of the AO,whereas the AO perspective only contains about half of the information of the NAO-PNA.Consequently,the NAO-PNA perspective is regarded by the authors to be more comprehensive than that of the AO.
文摘In this study, using the ECMWF reanalysis data, the possible linkage between the Pacific-North American teleconnection pattern （PNA） and the North Atlantic Oscillation （NAO） during boreal winter （December- February） is investigated. The PNA and the NAO pattern are obtained by performing Rotated Empirical Orthogonal Function （REOF） analysis on an anomalous daily mean 300-hPa geopotential height field. The composite daily NAO indices show that the NAO indices are prone to be negative （positive） when the contemporary PNA indices are extremely positive （negative）. The correlation coefficients between the daily PNA and NAO indices also confirm that, indeed, there is a significant anti-correlation between the PNA and NAO indices. The correlation peaks at a lag of 0 days （meaning contemporary correlation）, and its value is 0.202. Analyses of a newly defined Rossby wave breaking index and diagnostics of the stream function tendency equation indicate that the anti-correlation between PNA and NAO may be caused by the anomalous Rossby wave breaking events associated with the PNA pattern.
文摘To study the impact of climate change on Godthab(Greenland), temperature and precipitation gathered from the Global Historical Climatology Network (GHCN) were analyzed for patterns within 1866-2011. Both temperature and precipitation have experienced an overall increase throughout the past 146 years. Precipitation, however, has experienced a declining trend since 1985. North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) indices showed strong correlations with average annual temperature (R = ?0.6) and smaller correlations with annual total precipitation (R = ?0.2). There are moderate correlations between temperature, precipitation, and Southern-Oscillation Index (SOI). The positive phases of Pacific-North American (PNA) led to increased winter and spring precipitation. The climate mode’s influential strength on Godthab’s temperature and precipitation, vary seasonally. In contrast with global average temperatures, Greenland has not experienced a continual warming trend since the 1950s;30- and 10-year trends show a cooling period between 1965 and 1995. From 1866 to 2011, Godthab’s average annual temperature has increased by 1.9?C, and is anticipated to continue to warm in accordance with the global warming trend and the Arctic’s associated feedback mechanisms.
