Qz. Geng et al., Role of transients in the dynamics of east Asian summer seasonal mean circulation anomalies - A study of 1993 and 1994, J CLIMATE, 13(19), 2000, pp. 3511-3531
By using the National Centers for Environmental prediction reanalysis data
and a nonlinear barotropic model, the transient activities and the possible
role of transient Vorticity fluxes in the maintenance of east Asian summer
seasonal mean circulation anomalies associated with Japan's extremely cool
and wet. summer of 1993 and hot and dry summer of 1994 are examined. Data
analysis shows that the summertime atmospheric circulation and the transien
t activity anomalies exhibit nearly opposite patterns over east Asia during
these two years. Vorticity budget calculations indicate that the anomalies
of transient activities in these two years produced strong transient vorti
city flux forcing anomalies that are comparable in magnitude to the diverge
nt forcing anomalies over east Asia.
The nonlinear barotropic model, when forced by the anomalous divergence and
transient vorticity Aux forcing together, produces simulations that bear r
esemblance to the observed summertime seasonal mean circulation anomalies o
f 1993 and 1994. The response to the anomalous transient vorticity flux for
cing is found to be similar in magnitude with the response to the anomalous
divergence. The solution deteriorates if the transient vorticity flux forc
ing anomaly is not included.
Both the vorticity budget analysis and model simulations in the present pap
er show that the transient vorticity flux forcing anomaly plays an importan
t role in maintaining the observed circulation anomalies over east Asia dur
ing the 1993 and 1994 summers.