Typical(?) Diurnal Variation of Radar Echo over Bangla.

Toru Terao(Osaka Gakuin Univ.)Md. N. Islam(BUET, Banlgadesh)

Bangladesh RADAR Four RADAR data

Dhaka RADAR is used mainly

Intensive rawin sonde obs.

Dhaka RADAR Continuous observations are

conducted basically only for one hour duration for every other three hours, as follows; 5-6, 8-9, 11-12, 14-15, 17-18, 20-21, 23-

24BST. Almost all area of this country except

for southeastern most part is covered.

Fig10

Fig. 10. Same as Fig. 7 except averaged for 1 August to 30 August 2000.

NE part:Night-E. Morning

S part:E.

Morning

C-W part:Daytime

Area & Number of Echoes

Dhaka Radar

0

2

4

6

8

10

12

14

00 06 09 12 15 18 21

TIME(LST)

Ech

o E

mbe

dded

Are

a(10

3 k

m2/s

can)

APR MAY JUNJUL AUG AMJJA

Echo Embedded Area Dhaka Radar

0

10

20

30

40

50

60

70

80

90

100

00 06 09 12 15 18 21TIME(LST)

Fre

quen

cy o

f Occ

urre

nce/

scan

APR MAY JUN

JUL AUG AMJJA

Freq. of Occurrence

Afternoon: many small

echoes

Midnight: max. echo area

Statistical Results NE part:

Heavy rain, Midnight-morning peak Larger echoes

S part(coastal area): Heavy rain, Morning peak

C-W part(plain): Light rain, Afternoon peak Many smaller echoes.

Convection: 17/18 July 2001A typical pattern of the diurnal variation will be shown

using Dhaka RADAR data.

17 July 18 July

8:30, 11:30, 14:30, 17:30, 20:30, and 23:30

A case study

Convection: 17/18 July 2001A typical pattern of the diurnal variation will be shown

using Dhaka RADAR data.

17 July 18 July8:30

No conv.

Convection: 17/18 July 2001A typical pattern of the diurnal variation will be shown

using Dhaka RADAR data.

17 July 18 July11:30

SWscattering

Convection: 17/18 July 2001A typical pattern of the diurnal variation will be shown

using Dhaka RADAR data.

17 July 18 July14:30

SWdeveloping

Convection: 17/18 July 2001A typical pattern of the diurnal variation will be shown

using Dhaka RADAR data.

17 July 18 July17:30

Eforming

Convection: 17/18 July 2001A typical pattern of the diurnal variation will be shown

using Dhaka RADAR data.

17 July 18 July20:30

E -> NESquall line

Convection: 17/18 July 2001A typical pattern of the diurnal variation will be shown

using Dhaka RADAR data.

17 July 18 July23:30

NEspread

Morning to afternoon: Scattering convectionsover the south western part of Bangladesh

Typical Diurnal Variation

Evening to Midnight: Organized convectionsover the north eastern part of Bangladesh

Patterns are strikingly similar for two days

17 and 18 July 2001

We should clarify why such pattern appeared.

Comparison with prev. study

RADAR data Ohsawa et al. (2001)

Midnight

Noon