Correlation of DJF ALI with (a) July and (b) August rainfall in the following year. Heavy (light) shading in (a, b) indicates correlation coefficients significant at the 95% (90%) confidence level. Contour intervals are 0.1 in (a, b), and the green box is the region of SC (22–30°N, 105–118°E) in this study. Lag-lead correlation of ALI from preceding SON to JJA with (c) July and (d) August rainfall indices obtained from the UD rainfall dataset during 1901–2004. The dashed lines indicate significance at the 95% and 90% confidence level. (e) Sliding correlations between DJF AL index and July SC rainfall index displayed at the central year of a 21-yr window. (f) As in (e) but for the August rainfall index. Horizontal dashed lines in (e, f) indicate the correlation coefficient is significant at the 90% confidence level. Note that all variables have been subjected to a nine-year high-pass filter and the DJF ENSO signal has been linearly removed in constructing this figure. (Figure plotted by IAP)
The winter AL-related atmospheric circulation anomalies in the following summer were also examined. When the winter AL is stronger, there is a significant anticyclonic (cyclonic) circulation anomaly over the subtropical western North Pacific in the following July (August). Southerly (northerly) wind anomalies to the west of this anomalous anticyclonic (cyclonic) circulation increase (decrease) the northward moisture transportation and contribute to the positive (negative) rainfall anomalies over SC in July (August).
Anomalies of (a, d) 1000 hPa geopotential height (units: m), (b, e) 850 hPa horizontal winds (units: m s−1) and (c, f) 500 hPa geopotential height (units: m) in (a–c) July and (d–f) August regressed on the normalized DJF ALI during 1979–2004. Heavy (light) shading indicates geopotential anomalies that are significantly different from zero at the 95% (90%) confidence level. Note that all variables have been subjected to a nine-year high-pass filter and the DJF ENSO signal has been linearly removed in constructing this figure. (Figure plotted by IAP)
Hence, the research results indicate that the AL in the preceding winter can be used as a potential predictor of the rainfall anomalies in the following July and August over SC.
This research has been published in Atmospheric Oceanic Science Letters recently.
Citation: Song, L.-Y., and W.-S. Duan, 2015: Interannual relationship between the winter Aleutian Low and rainfall in the following summer in South China, Atmos. Oceanic Sci. Lett., 8, doi:10.3878/AOSL20150021.
Download: http://159.226.119.58/aosl/EN/abstract/abstract562.shtml
Contact: DUAN Wan-Suo, duanws@lasg.iap.ac.cn