ISSN 1006-9895

CN 11-1768/O4

Three-Dimensional Circulation Structure of Summer Heavy Rainfall in the middle-lower reaches of the Yangtze River Valley
Author:
Affiliation:

1.University of Chinese Academy of Sciences;2.State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics,Institute of Atmospheric Physics,Chinese Academy of Sciences

Fund Project:

  • Article
  • |
  • Figures
  • |
  • Metrics
  • |
  • Reference
  • |
  • Related
  • |
  • Cited by
  • |
  • Materials
    Abstract:

    By using the daily station data and Japanese 55-year Reanalysis Project (JRA-55) data in the course of 1959-2013, a three-dimensional background circulation structure of summer heavy rainfall in the middle-lower reaches of the Yangtze River Valley (MLYRV) is analyzed. Composite analyses of circulation in advance of 373 heavy rainfall days reveal that a prominent warm anomaly with a center at 300hPa emerges in the upper troposphere over MLYRV. Because of hydrostatic and quasi-geostrophic equilibriums, an anticyclonic (cyclonic) anomaly forms above (below) the warm center. On one hand, the warm anomaly makes the westerly winds to the north of the warm center strengthened by high-level anticyclonic circulation anomaly, which results in the jet stream in the upper-level over East Asia shifting southward and eastward to the north side of MLYRV. So the upper-level divergent anomaly field over MLYRV is enhanced. On the other hand, the cyclonic anomaly below the warm anomaly reinforces the low-level southwesterly winds to MLYRV, which makes more water vapor transporting to MLYRV and convergence stronger. The favorable configuration of high and low altitude circulation anomalies caused by warm anomalies plays an important role in the formation of strong precipitation in MLYRV. The 300 hPa warm anomaly exists at 400-300 hPa in the eastern part of the Qinghai-Tibet Plateau 48 hours before the precipitation in MLYRV, and the 700-hPa cyclonic circulation appears in the middle and lower layers over the Sichuan Basin 24 hours ahead of schedule. The high and low circulation elements cooperate with each other and move eastward with time. The warm anomaly first reaches MLYRV, and cooperates with the low-level cyclonic circulation and water vapor convergence area, resulting in strong precipitation in MLYRV.

    Reference
    Related
    Cited by
Get Citation
Share
Article Metrics
  • Abstract:
  • PDF:
  • HTML:
  • Cited by:
History
  • Received:February 01,2019
  • Revised:April 23,2019
  • Adopted:May 16,2019
  • Online:
  • Published: