Dominant Modes of Tropospheric Ozone Variation over East Asia from GOME Observations

Figure 4

Two dominant patterns retrieved from EOF analysis ((a) EOF1, (b) EOF2) of monthly mean TOVMR (color shaded) and their corresponding time series ((c) PC1, (d) PC2; red: positives, blue: negatives) between March 1996 and June 2003. The yellow contours in (a) are total westerly jet occurrence counts based on 6-hourly ERA-interim data, and the thick green lines show the position of maximum occurrence. Summer (June–August) winds at 200 hPa for the same period are shown by vectors in (b). The red star is the location of Beijing and the red dots are locations of Lhasa, Xining, and Pyramid (Nepal); they are four ozonesonde stations. The square in (a) is the area of northern China; the square in (b) is southern Tibetan Plateau and the area to the south of Tibetan Plateau.

(a) EOF1 (61.5%)

(b) EOF2 (29.2%)

(c) PC1

(d) PC2