Interdecadal Variation of Precipitation over the Hengduan Mountains during Rainy Seasons

Abstract

The present study investigates the interdecadal variation of precipitation over the Hengduan Mountains (HM) during rainy seasons from various reanalysis and observational datasets. Based on a moving t test and Lepage test, an obvious rainfall decrease is identified around 2004/05. The spatial distribution of the rainfall changes exhibits large and significant precipitation deficits over the southern HM, with notable anomalous lower-level easterly divergent winds along the southern foothills of the Himalayas (SFH). The anomalous easterlies are located at the northern edge of two cyclones, with two centers of positive rainfall anomalies over the west coast of India (WCI) and the Bay of Bengal (BOB). Observational evidence and numerical experiments demonstrate that the decadal changes of SST over the WP and WIO suppress rainfall over the eastern Indian Ocean (EIO) through large-scale circulation adjustment. The EIO dry anomalies trigger the cross-equatorial anticyclonic wind anomalies as a Rossby wave response, and further cause anomalous meridional circulation and moisture transport over the WCI and BOB, favoring the rainfall increase there. The anomalous easterlies at the northern edge of two cyclones induced by the wet anomalies–related heating cause the divergence anomalies along the SFH, resulting in the reduction of precipitation in the HM. In turn, the two anomalous cyclones and dry anomalies have positive feedback on the wet and easterly wind anomalies, respectively, emphasizing the importance of the circulation–heating interaction.

Synoptic‐Scale Circulation Precursors of Extreme Precipitation Events Over Southwest China During the Rainy Season

“…It means that these two typical circulation patterns are responsible for extreme precipitation over southern China, but the affected regions vary with their different locations/phases. In addition, it was reported that SRP can influence rainy-season mean rainfall over SWC in interannual and interdecadal time scale (D. H. Dong et al, 2018Dong et al, , 2019. We calculate the SRP index before and after the REPEs, following Hong and Lu (2016) to investigate whether the two Rossby wave trains in the paper are related to SRP.…”

“…Under the background of global warming, the daily precipitation extremes in SWC are sensitive to anthropogenic influences (H. P. Chen & Sun, 2017). From an interdecadal perspective, the precipitation variability over SWC is influenced by the Indian summer monsoon (ISM), East Asian summer monsoon (EASM), the Silk Road pattern (SRP), and sea surface temperature (SST) over Indian Ocean, tropical‐North Pacific Ocean, and so on (D. H. Dong et al., 2019; L. Liu, Cao et al., 2011; L. Wang, Huang et al., 2018; T. Wei et al., 2018). The interannual variability of precipitation over SWC is also attributed to the variability of the ISM and EASM (X.…”

Dominant modes of interannual variability in precipitation over the Hengduan Mountains during rainy seasons

“…As a result, 151 stations in HM are selected for analysis. The rainy seasons of HM are from May to September, and the total precipitation during rainy seasons accounts for more than 80% of annual total precipitation (Gao et al ., 2013; Dong et al ., 2018; Dong et al ., 2019; Tao et al ., 2020). Besides, monthly global land‐surface precipitation dataset based on rain gauges from the Global Precipitation Climatology Centre Full Data Reanalysis Version 6.0 (GPCC V6; Schneider et al ., 2014) with a spatial resolution of 0.5° × 0.5° is used to verify its consistency with station observations.…”

“…The variables include precipitation, evaporation, horizontal winds, vertical pressure velocity, specific humidity, surface pressure, air temperature, and geopotential height. According to the results of our previous studies, JRA55 well capture the climatology (Tao et al ., 2020), interannual (Dong et al ., 2018), and interdecadal (Dong et al ., 2019) characteristics of HM precipitation. The monthly SST data is from NOAA Extended Reconstructed Sea Surface Temperature (ERSST) V5 on a 2° × 2° grid (Smith and Reynolds, 2003).…”

“…It has been generally recognized that monsoon climate is influenced not only by the variations from tropics, that is, El Niño‐Southern Oscillation (ENSO; e.g., Wang et al ., 2000; Lau and Weng, 2001; Lau and Wu, 2001; Xie et al ., 2009; Chowdary et al ., 2019), Indian Ocean Dipole (IOD; e.g., Guan and Yamagata, 2003; Saji and Yamagata, 2003; Yuan et al ., 2008; Qiu et al ., 2014), but also by the atmospheric processes at middle and high latitudes, that is, Silk Road pattern (SRP; e.g., Lau and Wu, 2001; Lu et al ., 2002; Wu, 2002; Enomoto et al ., 2003; Ding and Wang, 2005; Kosaka et al ., 2009; Gong et al ., 2018), North Atlantic Oscillation (NAO; e.g., Wu et al ., 2009; Gong et al ., 2011; Sun and Wang, 2012; Song et al ., 2014; Chen et al ., 2020). Recent studies have confirmed that the HM precipitation is largely controlled by the tropical sea surface temperature (SST) and mid‐ and high‐latitude atmospheric modes at different time scales (Dong et al ., 2018; Dong et al ., 2019). In particular, Dong et al .…”