Kim, Kyung-Eak

Kinematic Characteristics of mesoscale precipitation systems nearby

the Baiu front by Doppler radar observations

Kim, Kyung-Eak

Department of Astronomy and Atmospheric Science, Kyungpook National University

Kyungpook National University 2

Contents Ⅰ. Introduction

Ⅱ. Data acquisition

Ⅲ. Analysis Method 1. VVP method 2. Calculation of vertical air velocity

Ⅳ. Analysis Results

Ⅴ. Summary and Conclusion


Ⅰ. Introduction


1. Previous Studies

Takeda and Seko (1986) Study of 3-dimensional structures and propagation prosess of mesoscale rain band using data based on radar observation.

Ninomia et al (1988) notified that fluctuation of Chang-ma(Baiu or Maiu) front has organization according Orlanski classification.


Iwasaki and Takeda (1993) Study of structures and states of mesoscale cloud clusters moving over the Chang-ma front zones

Ishihara et al (1995) Analysis properties of heavy mesoscale rain band over the Chang-ma front using the Doppler radar.

Takahashi et al.(1996) Analysis of both mesoscale and convectice scale features of Baiu frontal heavy rainfall.


Bessho et al.(1999) Multi-scale structure of Baiu front

Kanada et al.(2000) study of rainfall enhancement of band-shaped convective cloud system in the downwind side of Yaku-shima


2. Purpose of study

To Study kinematic characteristics and structure of mesoscale precipitation developed on the Baiu front using a Doppler radar observations


Ⅱ. Data acquisition


1. Observation area

The location of Doppler radar and radiosonde observation site

Radar data : Yakushim, Japan

Sounding data : Minamita, Japan


Case 1: 1600 LST, 21- 0700 LST, 22, June, 1996 Case 2: 1900 LST, 05- 1600 LST, 06, July, 1996

2. observation period

3. elevation angles

0.5o, 1.6o, 2.8o, 4.2o, 6.1o, 8.9o, 12.9o, 17.9o, 24.0o, 31.0o


4. The characteristics of MRI-X band radar installed at Minamita

Pulse repetition frequency (Hz)

2000

Number of range gates

256

Parameter Characteristic values

Frequency (MHz)Wavelength (cm)Maximum range (km)Nyquist velocity (m/s)Pulse repetition frequency(Hz)Number of range gatesRange resolution (m)Azimuth resolution (degree)Data resolutions Velocity (m/s) Reflectivity (dBZ)

9810375

15.2920002562501. 0

0. 10.1


Ⅲ. Analysis Method


1. VVP(Volume Velocity Processing)

The data processing geometry of VVP and TVP method. The △h and D are the vertical depth and diameter of slice, respectively. Here the 250 m and 45 km, respectively.


Kinematical parameters estimated by VVP method

,,,,, 000 y

v

x

uwvu

z

w

z

v

z

u

x

v

y

u

,,,


2. Calculation of vertical air velocity

used anelastic mass continuity equation (Ogura and Phillips, 1962)

'

'

)0

(

0

)0

()( dzH

z

ey

vzz x

uH

z

eH

zz

ezawz

aw


Ⅳ. Analysis Results


1600 LST, 21, June, 1996 ~ 0700 LST, 22, June, 199

6

Case Ⅰ


The surface weather map at (a) 0000 UTC(9 LST) 21 June, and (b) 1200 UTC(21 LST) 21 June, 1996.

(a) (b)


Infrared satellite image at (a) 1800 LST 21 June, (b) 2100 LST 21 June. (c) 0000 LST 22 June, and (d) 0300 LST 22 June, 1996

(a) (b)

(c) (d)


Three hourly rainfall amounts around Yakushima from 1500 LST 21 June, 1996 to 0900 LST 22 June, 1996 (Case 1).


The vertical profiles of potential temperature, equivalent potential temperature and saturated equivalent potential temperature at (a) 1500 LST, 21, June, (b) 2100 LST, 21, June and (c) 0900 LST, 22, June, respectively. And the vertical profiles of (d) temperature, (e) wind speed and (f) wind direction at periods of (a), (b) and (c).


Time-height cross sections of (a) reflectivity (dBZ) and (b) divergence (1.0×10-4 s-1) from 1600 LST 21 to 0700 LST 22 June, 1996.


The vertical profiles of (a) radar reflectivity, (b) divergence, (c) vertical air velocity, and (d) fall velocity at 1800 LST-1900 LST 21 June, 1996.


The vertical profiles of (a) radar reflectivity, (b) divergence, (c) vertical air velocity, and (d) fall velocity at 2100 LST, 21-0115 LST, 22, June, 1996


The vertical profiles of (a) radar reflectivity, (b) divergence, (c) vertical air velocity, and (d) fall velocity at 0200 LST - 0230 LST, 22, June, 1996.


The vertical profiles of (a) radar reflectivity, (b) divergence, (c) vertical air velocity, and (d) fall velocity at 0400 LST-0430 LST, 22, June,1996.


The vertical profiles of (a) radar reflectivity, (b) divergence, (c) vertical air velocity, and (d) fall velocity at 0500 LST - 0645 LST, 22, June, 1996.


Time-height cross sections of divergence components (×10-4s-1) parallel (a) and perpendicular (b) to the front of Case 1, respectively.


Time-height cross sections of vertical wind shear components (×10-3s-

1) parallel (a) and perpendicular (b) to the front of Case 1, respectively.


Case Ⅱ

1900 LST, 05 , July, 1996 ~1600 LST, 06, July, 1996


The surface weather maps at (a) 1200 UTC (2100 LST) 5 July, 1996 and (b) 1200 UTC (2100 LST) 6 July, 1996.

(a) (b)


GMS IR images with 3 hour intervals from 1800 LST 5 July, 19 96 to 1500 LST 6 July, 1996 (Case 2).

(a) 1800 LST 5 July 1996

(b) 2100 LST 5 July 1996

(c) 0000 LST 6 July 1996

(d) 0300 LST 6 July 1996


continued

(e) 0600 LST 6 July 1996

(f) 0900 LST 6 July 1996

(g) 1200 LST 6 July 1996

(h) 1500 LST 6 July 1996


Three hourly rainfall amounts around Yakushima from 1800 LST 5 July, 1996 to 1800 LST 6 July, 1996 (Case 2).


The vertical profiles of potential temperature (θ), equivalent potential temperature (θe), and saturated potential temperature (θes) at (a) 2100 LST 5 July, (b) 0900 LST 5 July and (c) 1500 LST 6 July, and the vertical profiles of (d) temperature, (e) wind speed and (f) wind direction at period of (a), (b), and (c), respectively.


Time-height cross sections of (a) reflectivity (dBZ) and (b) divergence(1.0x10-4 s-1) from 1900 LST 5 to 1600 LST 6 July, 1996.


Time-height cross sections of (a) fall velocity (ms-1) and and (b) vertical velocity of air (ms-1).


Time-height cross sections of divergence components(×10-4 s-1) parallel (a) and perpendicular (b) to the front of Case 2, respectively.


Time-height cross section of vertical wind shear (×10-

3s-1) of Case 2.


Schematic diagram of precipitation structure developed on Baiu front of Case 1 and 2. The C1 represents a convective system ahead of the Baiu front, and the C1, and C2 are convective systems developed on the line of wind shear. The S1 and S2 represent a large stratiform cloud system with bright band and stratiform cloud on the shear line, respectively.

Case 1 Case 2


The vertical profiles (a) radar reflectivity (dBZ), (b) divergence (×10-4 s-1), (c) vertical velocity of air (ms-1), and (d) fall velocity (ms-1) averaged from 1900 LST to 2200 LST 6 July, 1996.`


The vertical profiles (a) radar reflectivity (dBZ), (b) divergence (×10-4 s-

1), (c) vertical velocity of air (ms-1), and (d) fall velocity (ms-1) averaged from 1145 LST 6 to 1600 LST 7 July, 1996.


Time height cross sections of vertical wind shear components (×10-3 s-

1) parallel (a) and perpendicular (b) to the front of Case 2, respectively.


V. Summary and conclusions


1). The present study shows that the precipitation structure and kinematic characteristics and structure of the precipitation developed along the Baiu front highly depends on its type, that is, cold-type or warm-type.

2). The analyzed Baiu frontal precipitation system were found to be composed of three different systems: convective system whose top higher than the melting level, stratiform cloud with bright band, and clouds developed along the vertical shear line of the horizontal wind.

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Kim, Kyung-Eak