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Korean Meteorological Society (한국기상학회)
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Characteristics of Summer Season Precipitation Motion over Jeju Island Region Using Variational Echo Tracking

변분에코추적법을 이용한 제주도 지역 여름철 강수계의 이동 특성 분석

  • Kim, Kwonil (Dept. of Astronomy and Atmospheric Sciences, Research and Training Team for Future Creative Astrophysicists and Cosmologists, Kyungpook National University) ;
  • Lee, Ho-Woo (Korea Air Force Weather Group) ;
  • Jung, Sung-Hwa (Weather Radar Center, Korea Meteorological Administration) ;
  • Lyu, Geunsu (Center for Atmospheric REmote sensing, Kyungpook National University) ;
  • Lee, GyuWon (Dept. of Astronomy and Atmospheric Sciences, Research and Training Team for Future Creative Astrophysicists and Cosmologists, Kyungpook National University)
  • 김권일 (경북대학교 천문대기과학과, 천체물리 및 우주론 분야 미래 창의 인재 양성팀) ;
  • 이호우 (공군기상단) ;
  • 정성화 (기상청 기상레이더센터) ;
  • 류근수 (경북대학교 대기원격탐사연구소) ;
  • 이규원 (경북대학교 천문대기과학과, 천체물리 및 우주론 분야 미래 창의 인재 양성팀)
  • Received : 2018.11.01
  • Accepted : 2018.12.24
  • Published : 2018.12.31
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Abstract

Nowcasting algorithms using weather radar data are mostly based on extrapolating the radar echoes. We estimate the echo motion vectors that are used to extrapolate the echo properly. Therefore, understanding the general characteristics of these motion vectors is important to improve the performance of nowcasting. General characteristics of radar-based motions are analyzed for warm season precipitation over Jeju region. Three-year summer season data (June~August, 2011~2013) from two radars (GSN, SSP) in Jeju are used to obtain echo motion vectors that are retrieved by Variational Echo Tracking (VET) method which is widely used in nowcasting. The highest frequency occurs in precipitation motion toward east-northeast with the speed of $15{\sim}16m\;s^{-1}$ during the warm season. Precipitation system moves faster and eastward in June-July while it moves slower and northeastward in August. The maximum frequency of speed appears in $10{\sim}20m\;s^{-1}$ and $5{\sim}10m\;s^{-1}$ in June~July and August respectively while average speed is about $14{\sim}15m\;s^{-1}$ in June~July and $8m\;s^{-1}$ in August. In addition, the direction of precipitation motion is highly variable in time in August. The speed of motion in Lee side of the island is smaller than that of the windward side.

Keywords

KSHHDL_2018_v28n4_443_f0001.png 이미지

Fig. 1. Topography and analysis domains (D1, D2, D3). The altitude above mean sea level is shaded. Dashed circles represent 150 km ranges from GSN and SSP radar. Box symbols indicate the locations of radar.

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Fig. 2. Flow chart of the construction of valid motion vectors from GSN, SSP radar data.

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Fig. 3. Normalized frequency distribution of the direction and speed of motion vectors in D2 during the entire period. Upper (right) panel shows normalized frequency distribution of speed (direction) of motion vectors. ‘X’ mark indicates maximum frequency, whiskers represent the median, first and third quartile.

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Fig. 4. Diurnal variation of normalized frequency distribution of the (a) direction and (b) speed of motion vectors in D2 during the entire period. Upper panel shows time-averaged normalized frequency distribution. ‘X’ mark indicates maximum frequency for every hour and whiskers represent the median, first and third quartile.

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Fig. 5. Same as in Fig. 5 except for (a), (d) June, (b), (d) July, (e), (f) August. Upper and lower panels are the direction and the speed of motion vectors, respectively.

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Fig. 6. Diurnal variation of the (a) direction and (b) speed of motion vectors in D2 for each month. Solid line indicates the mean and dashed lines represent standard deviations from the mean.

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Fig. 7. Spatial distribution of the (a) mean direction and (b) mean speed of the motion vectors in D2. Standard deviations of (c) direction and (d) speed of motion vectors are also presented. Only 13 × 13 out of 25 × 25 vectors is displayed.

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Fig. 8. Same as in Fig. 7a and Fig. 7b except for (a), (d) June, (b), (e) July, (c), (f) August. Upper and lower panels are the direction and the speed of motion vectors, respectively.

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Fig. 9. Hovmöller Diagram of the (a) direction and (b) speed of motion vectors in D3. Upper panels show averaged direction and speed (in blue) of motion vectors and topography height (in black).

Table 1. Specification of GSN and SSP radars.

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Table 2. The number of 2 km MOSAIC used for generating motion vectors, the number of valid motion vectors, and the ratio of valid motion vectors to the generated motion vectors.

KSHHDL_2018_v28n4_443_t0002.png 이미지

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