warm ridge
1.The results show that a warm high ridge at the middle level and transformed surface cold high over the plain provide a good background condition; a cooling process produced by net surface radiation fluxes is the trigger and strengthening mechanism for the fog event; the subsidence flow at the middle and low tropospheric levels is favorable for the setting-up and maintenance of stable stratification at the boundary layer and weak wind condition at the ground layer over the fog region; the transportation of weak warm advection at lower levels and weak lift motion at the boundary layer play a very important role to the long maintenance of the fog event; the intrusion of north wind accompanied by cold advection is a main dynamic factor of the fog dissipation.
2.and in the middle troposphere,when the winter AO is in its low(high) phase,the East Asia trough is strengthened(weakened),the ridge west and north of Baikal Lake is also strengthened(weakened),the circulation develops meridionally(zonally),the northerly wind is strengthened(weakened),and northeast China undergoes successive cold(warm)winter.
