ISSN 1006-9895

CN 11-1768/O4

Analysis of Frontogenesis and Circulation Characteristics of the Meiyu Front with Heavy Precipitation in Zhejiang Province
Author:
Affiliation:

1.Jinhua Meteorology Bureau, Jinhua, Zhejiang 321000;2.Pujiang Meteorology Bureau, Pujiang, Zhejiang 322200

Fund Project:

Innovation Team Project of Severe Weather Forecast in Jinhua Meteorological Bureau;Specific Funds for Weather Forecast in Zhejiang Meteorological Bureau Grant 2016YBY13Innovation Team Project of Severe Weather Forecast in Jinhua Meteorological Bureau, Specific Funds for Weather Forecast in Zhejiang Meteorological Bureau (Grant 2016YBY13)

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    Abstract:

    This paper analyzes the frontogenetic and circulation characteristics in central and western Zhejiang Province as represented by a typical Meiyu process on 15 June 2016. Based on ERA-INTERIM (0.25°×0.25°) reanalysis data, FY-2E TBB (Black Body Temperature) data, and radar data, the relationship between frontogenesis and heavy precipitation, and the characteristics of circulation, were analyzed by means of wind decomposition and composite analysis. Results indicated that the typical Mei-yu was under a favorable synoptic-scale background, and the heavy precipitation area was closely related to the low-to-mid-level frontogenesis. When the frontal zone persisted, it was accompanied by mid-level deformation and tilting frontogenesis. When the frontal zone shifted southward, it was accompanied by mid-level tilting frontogenesis and low-level horizontal frontogenesis. The super-geostrophic westerly airflow on the north side of the low-level Mei-yu front and the strong southeast ageostrophic airflow on the south side affected the unbalanced northerly airflow on the north side and the balanced southwesterly airflow on the south side, thus affecting frontal development. In the frontal zone, upward motion, which formed the ascending branch of the secondary circulation, was caused by low-level geostrophic deviation convergence and upper-level divergence. The contrary was found in the post-frontal area. Additionally, in the pre-frontal area, the low-level zonal wind was sub-geostrophic, while in the post-frontal area, the low-level zonal wind was super-geostrophic, and the upper-level zonal wind was sub-geostrophic. Thus further enhanced the secondary circulation. After composite, there was an area of significant enhancement of the northwesterly and southwesterly airflow behind and in the frontal trough at 200 hPa. In addition, there was a significant northeasterly wind variation area over northern Zhejiang Province at 700 hPa. Horizontal and vertical distribution of the decomposition items were similar between the composite and typical cases. Low-level frontogenesis was mainly contributed to by the divergence term, followed by the deformation term, while the tilting term had a negative contribution. Mid-level frontogenesis was mainly contributed to by the tilting term, followed by the deformation term. Upper-level frontolysis was mainly contributed to by the tilting term.

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History
  • Received:July 04,2018
  • Revised:
  • Adopted:
  • Online: November 14,2019
  • Published: