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Title: Role of seasonal transitions and the westerlies in the interannual variability of the East Asian summer monsoon precipitation

ORCiD logo [1];  [1];  [1]
  1. Department of Geography and Berkeley Atmospheric Sciences Center, University of California, Berkeley California USA
Publication Date:
Sponsoring Org.:
OSTI Identifier:
Grant/Contract Number:
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Geophysical Research Letters
Additional Journal Information:
Journal Volume: 44; Journal Issue: 8; Related Information: CHORUS Timestamp: 2018-04-02 17:11:18; Journal ID: ISSN 0094-8276
American Geophysical Union
Country of Publication:
United States

Citation Formats

Chiang, J. C. H., Swenson, L. M., and Kong, W. Role of seasonal transitions and the westerlies in the interannual variability of the East Asian summer monsoon precipitation. United States: N. p., 2017. Web. doi:10.1002/2017GL072739.
Chiang, J. C. H., Swenson, L. M., & Kong, W. Role of seasonal transitions and the westerlies in the interannual variability of the East Asian summer monsoon precipitation. United States. doi:10.1002/2017GL072739.
Chiang, J. C. H., Swenson, L. M., and Kong, W. Wed . "Role of seasonal transitions and the westerlies in the interannual variability of the East Asian summer monsoon precipitation". United States. doi:10.1002/2017GL072739.
title = {Role of seasonal transitions and the westerlies in the interannual variability of the East Asian summer monsoon precipitation},
author = {Chiang, J. C. H. and Swenson, L. M. and Kong, W.},
abstractNote = {},
doi = {10.1002/2017GL072739},
journal = {Geophysical Research Letters},
number = 8,
volume = 44,
place = {United States},
year = {Wed Apr 19 00:00:00 EDT 2017},
month = {Wed Apr 19 00:00:00 EDT 2017}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1002/2017GL072739

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  • This paper presents a comprehensive analysis of interannual and interdecadal variations of summer precipitation and precipitation-related extreme events in China associated with variations of the East Asian summer monsoon (EASM) from 1979-2012. A high-quality daily precipitation dataset covering 2287 weather stations in China is analyzed. Based on the precipitation pattern analysis using empirical orthogonal functions, three sub-periods of 1979-1992 (period I), 1993-1999 (period II) and 2000-2012 (period III) are identified to be representative of the precipitation variability. Similar significant variability of the extreme precipitation indices is found across four sub-regions in eastern China. The spatial patterns of summer mean precipitation,more » the number of days with daily rainfall exceeding 95th percentile precipitation (R95p) and the maximum number of consecutive wet days (CWD) anomalies are consistent, but opposite to that of maximum consecutive dry days (CDD) anomalies during the three sub-periods. However, the spatial patterns of hydroclimatic intensity (HY-INT) are notably different from that of the other three extreme indices, but highly correlated to the dry events. The changes of precipitation anomaly patterns are accompanied by the change of the EASM regime and the abrupt shift of the position of the west Pacific subtropical high around 1992/1993 and 1999/2000, respectively, which influence the moisture transport that contributes most to the precipitation anomalies. Lastly, the EASM intensity is linked to sea surface temperature anomaly over the tropical Indian and Pacific Ocean that influences deep convection over the oceans.« less
  • Reasonably modeling the magnitude, south-north gradient and seasonal propagation of precipitation associated with the East Asian Summer Monsoon (EASM) is a challenging task in the climate community. In this study we calibrate five key parameters in the Kain-Fritsch convection scheme in the WRF model using an efficient importance-sampling algorithm to improve the EASM simulation. We also examine the impacts of the improved EASM precipitation on other physical process. Our results suggest similar model sensitivity and values of optimized parameters across years with different EASM intensities. By applying the optimal parameters, the simulated precipitation and surface energy features are generally improved.more » The parameters related to downdraft, entrainment coefficients and CAPE consumption time (CCT) can most sensitively affect the precipitation and atmospheric features. Larger downdraft coefficient or CCT decrease the heavy rainfall frequency, while larger entrainment coefficient delays the convection development but build up more potential for heavy rainfall events, causing a possible northward shift of rainfall distribution. The CCT is the most sensitive parameter over wet region and the downdraft parameter plays more important roles over drier northern region. Long-term simulations confirm that by using the optimized parameters the precipitation distributions are better simulated in both weak and strong EASM years. Due to more reasonable simulated precipitation condensational heating, the monsoon circulations are also improved. Lastly, by using the optimized parameters the biases in the retreating (beginning) of Mei-yu (northern China rainfall) simulated by the standard WRF model are evidently reduced and the seasonal and sub-seasonal variations of the monsoon precipitation are remarkably improved.« less
  • Cited by 9
  • Industrial emissions of anthropogenic aerosols over East Asia have greatly increased in recent decades, and so the interactions between atmospheric aerosols and the East Asian summer monsoon (EASM) have attracted enormous attention. In order to further understand the aerosol-EASM interaction, we investigate the impacts of anthropogenic aerosols on the EASM during the multidecadal strong (1950–1977) and weak (1978–2000) EASM stages using the Community Atmospheric Model 5.1. Numerical experiments are conducted for the whole period, including the two different EASM stages, with present day (PD, year 2000) and preindustrial (PI, year 1850) aerosol emissions, as well as the observed time-varying aerosolmore » emissions. A comparison of the results from PD and PI shows that, with the increase in anthropogenic aerosols, the large-scale EASM intensity is weakened to a greater degree (-9.8%) during the weak EASM stage compared with the strong EASM stage (-4.4%). The increased anthropogenic aerosols also result in a significant reduction in precipitation over North China during the weak EASM stage, as opposed to a statistically insignificant change during the strong EASM stage. Because of greater aerosol loading and the larger sensitivity of the climate system during weak EASM stages, the aerosol effects are more significant during these EASM stages. Moreover, these results suggest that anthropogenic aerosols from the same aerosol emissions have distinct effects on the EASM and the associated precipitation between the multidecadal weak and strong EASM stages.« less