Meridional and vertical propagation characteristics of the submonthly Northern Hemisphere Annular Mode

From a “troposphere view”, the related horizontal and vertical circulation anomalies propagation characteristics of the Northern Hemisphere Annular Mode (NAM) in submonthly timescales (5-30 d) are studied by using the NCEP/NCAR reanalysis daily data and Li and Wang’s new NAM index, which can express better variation structure of the NAM. The results show that in the horizontal direction, the temperature anomaly shows intense southward propagation in the troposphere from the polar region and high latitudes to the equator, especially in the surface layer, while it shows weak northward propagation in the stratosphere from the mid-low latitudes to the high latitudes. And the zonal wind anomaly exhibits obviously southward propagation characteristics from the high latitudes to the equator nearly in all levels. In the vertical direction, the temperature anomaly shows upward propagation from the troposphere to the stratosphere in the middle latitudes and downward propagation from the stratosphere to the troposphere in the high and low latitudes. And the zonal wind anomaly propagates upward nearly in all the latitudes in the Northern Hemisphere. The horizontal propagation characteristics are similar on the main submonthly character time scales (quasi-week, quasi two-week and quasi three-week), but the vertical propagation characteristics are similar on quasi-week and quasi two-week, but the vertical circulation anomalies propagation on quasi three-week is different from the other two submonthly character time scales.  The atmosphere general circulation anomalies related to the NAM propagate strongly from the polar region to the equator in the troposphere of the Northern Hemisphere on submonthly timescales, which implies that the atmosphere anomalies in the midhigh latitudes may have predictive skills to atmospheric anomalies in the midlow latitudes on the relative short timescales; and the characteristics of upward propagation of the temperature and zonal wind anomalies on submonthly timescales implies that the circulation signals related to the NAM are not absolutely originated in the upper stratosphere, while the signals in the troposphere can propagate upward into the stratosphere on relative short timescales. 