Synergistic Effects of Midlatitude Atmospheric Upstream Disturbances and Oceanic Subtropical Front Intensity Variability on Western Pacific Jet Stream in Winter

Abstract

In winter, the western Pacific jet stream (WPJS) is located at the downstream of East Asian subtropical jet (EASJ) and East Asian polar front jet (EAPJ). It can be affected by sea surface temperature (SST) and has great impact on precipitation along the North American coast. Synergistic effects of midlatitude atmospheric upstream disturbances and oceanic subtropical front intensity variability on WPJS in winter are investigated in both observation and model experiments. It reveals that the strength and location of WPJS are determined by the configuration of atmospheric upstream disturbances and subtropical frontal zone (STFZ) intensity variability that exist concurrently. During the strong atmospheric upstream disturbances years, the WPJS is anchored at about 25–45°N, and its strength is enhanced (abated) by the intensified (weakened) STFZ. However, when the atmospheric upstream disturbances are weak, the intensity of STFZ changes the location of WPJS. An intensified (weakened) STFZ makes WPJS move southward (northward). Further studies show that strong atmospheric disturbances induce a wide and deep atmospheric baroclinicity anomaly zone, which makes the lower atmosphere obtain baroclinic energy from STFZ. Accordingly, the WPJS is anchored just the north of STFZ. At this time, the intensified (weakened) STFZ just increases (decreases) the upward baroclinic energy at the same position and thus the WPJS. However, with the weakened atmospheric upstream disturbances, the intensified (weakened) STFZ corresponds to an overhead narrow atmospheric baroclinicity anomaly zone, thus leading to the southward (northward) movements of upward baroclinic energy and the WPJS.

Local and remote forcing effects of oceanic eddies in the subtropical front zone on the mid-latitude atmosphere in Winter

“…14b). Some researches (Wang et al, 2016(Wang et al, , 2019Chen et al, 2019b;Chen et al, 2020) have discussed the atmospheric internal adjustment considering the STFZ intensity anomaly in atmospheric simulations. We further revealed the causes of the interannual variation of the STFZ intensity in this work.…”

“…Especially in the STFZ region, previous works discussed the forcing effects of STFZ intensity variations on above mid-latitude atmosphere (Wang et al, 2016(Wang et al, , 2019Chen et al, 2019b;Chen et al, 2020). However, the causes of interannual variation of STFZ intensity are not clear.…”

“…Their researches revealed that the stronger (weaker) year of the STFZ intensity was accompanied by the PDO warm (cold) phase sea temperature anomaly with the colder (warmer) north and the warmer (colder) south, which increased (weakens) the baroclinity of the lower atmosphere and might affect the upper atmosphere. Furthermore, Chen et al (2019b) and Chen et al (2020) pointed out that the STFZ significantly contributes to the variations of atmospheric storm track and westerly jet intensity in midlatitude via changing the vertical propagation of baroclinic Rossby wave and the incidence of barotropic Rossby wave breaking events. This process well reflects the forcing of the interannual variation of the STFZ intensity on the middle and upper atmosphere over the entire North Pacific, also known as remote forcing of the STFZ.…”

Synergistic effect of El Niño and the North Pacific Oscillation on wintertime precipitation over Southeastern China and the East China Sea Kuroshio area

“…ENSO and Tibetan Plateau snow cover also have a synergistic effect on the EASM (Wu et al 2012). Moreover, midlatitude atmospheric upstream disturbances and oceanic subtropical SST front intensity variability have synergistic effects on the wintertime western Pacific jet stream (Chen et al 2020). Thus, it may be more useful to give higher priority to investigating the joint effect of two or more factors than to single factor analysis.…”

Synergistic Effect of El Niño And The North Pacific Oscillation On Wintertime Precipitation Over Southeastern China And The East China Sea Kuroshio Area

“…ENSO and Tibetan Plateau snow cover also have a synergistic effect on the EASM (Wu et al 2012). Moreover, midlatitude atmospheric upstream disturbances and oceanic subtropical SST front intensity variability have synergistic effects on the wintertime western Paci c jet stream (Chen et al 2020). Thus it may be more useful to give higher priority to investigating the joint effect of two or more factors than to single factor analysis.…”