P177
バングラデシュにおける
プレモンスーン期およびモンスーン期の
降水の特徴
寺尾
村田
林
徹(大阪学院大学情報学部)
文絵(地球環境学研究所)
泰一(京都大学防災研究所)
Introduction
Bangladesh is one of the
heaviest rainfall areas.
Meso-scale characteristics


Diurnal variations. Midnightearly morning peak is found
in northeastern part of the
country (Ohsawa et al.
2001). Mechanism unknown.
Pre-monsoon meso-scale
disturbances.
Observation plan

Instruments with higher
temporal resolutions.
AWS and raingauges



AWS at Dhaka
Automatic raingauges: 6
Almost one year obs.
Some results is shown today.

Pre-monsoon rainfall
 -> A

Diurnal variations
 -> B

AWS obs. case study.
 -> C
Locations of AWS and raingauges
AWS


Dhaka(ICDDR,B)
Data are browsable
from everywhere in
the world through
the network.
Raingauges



6-locations:□
0.5mm tipping
buckets
Raingauges are
installed in BMD
observatories

Dinajpur

Mymensingh
 Rajshahi
INDIA
(Meghalaya)


Sylhet


INDIA

  Dhaka
(Tripura)

INDIA
  

(West Bengal)
     Chittagong
     




BAY OF
BENGAL
Obs. time table of AWS and RGs.
AWS
Dhaka
2004/03/03
2005/07/18
RGs
Chittagong
Dhaka
Dinajpur
Mymensingh
Rajshahi
Sylhet
2004/07/29
2004/08/24
2004/08/01
2004/08/11
2004/08/05
2005/02/28
2005/03/04
2005/03/01
2005/03/03
2005/03/01
2005/07/22
2005/07/18
2005/07/14
2005/07/17
2005/07/15
2005/07/20
30 Jun.- no data
Seasonal march in Bangladesh
Max. temp
Sunshine
1980-1999/Dhaka
Rain inc.: Apr->May
Sunshine dec.:May->Jun.
Pre-monsoon rainfall
begins in May
Rainfall
Def. of pre- and mature monsoon
Pre-monsoon

Jan.->May
Dinajpur
Mature monsoon

Jul.->Dec.
Sylhet
Pre-monsoon rain.

Northeast>West
Mymensingh
Rajshahi
Dhaka
Chittagong
A
Pre-monsoon and mature monsoon [1]
Rainfall intensity
Hourly rainfall
Complicated.
Pre-monsoon and mature monsoon [1]
Rainfall intensity
10-min rainfall
Short intense
downpower


Pre>mature
monsoon.
>5mm/10mi
nexceeds
50% of total
rain.
Intense
Intense
Intense
Pre-monsoon and mature monsoon [1]
Rainfall intensity
1-min rainfall
Almost same
results as 10min rainfall.
Intense
Intense
Intense
Pre-monsoon and mature monsoon [1]
Rainfall intensity
Summary
Intense rain in
pre-monsoon


>5mm/10min
exceeds 50%
of total rain
>1mm/min
exceeds 50%
of total rain

Dinajpur

Mymensingh
 Rajshahi
INDIA
(Meghalaya)


Sylhet


INDIA

  Dhaka
(Tripura)

INDIA
  

(West Bengal)
     Chittagong
     




BAY OF
BENGAL
B
Pre-monsoon and mature monsoon [2]
Diurnal variations
Premonsoon
diurnal var.


Evident
peak
Somewhat
differs from
mature
monsoon.
UTC(BST-6h)
Pre-monsoon and mature monsoon [2]
Diurnal variations
Summary I
Diurnal variations
in pre-monsoon



Central part:
afternoon peak.
Northern part:
Midnight-early
morning peak.
Steep peak is
founr mainly in
western part.
Pre-monsoon

Dinajpur

Mymensingh
 Rajshahi
INDIA
(Meghalaya)


Sylhet


INDIA

  Dhaka
(Tripura)

INDIA
  

(West Bengal)
     Chittagong
     




BAY OF
BENGAL
Pre-monsoon and mature monsoon [2]
Diurnal variations
Summary II
mature monsoon
Diurnal variations
in mature
monsoon

Mymensingh is
also in afternoon
peak area.

Dinajpur

Mymensingh
 Rajshahi
INDIA
(Meghalaya)


Sylhet


INDIA

  Dhaka
(Tripura)

INDIA
  

(West Bengal)
     Chittagong
     




BAY OF
BENGAL
C
Case study of pre-monsoon storm.
AWS
まとめ
バングラデシュ各地にAWSと
雨量計を設置した


AWS×1(2004年3月~)
雨量計×6(2004年8月~)
プレモンスーン期とモンスーン
期の違いを重視して解析した
プレモンスーン期はモンスーン
期に比べて短時間強雨が多い


プレモンスーン期にも降水の
日変化が見られる

データを増や
して確認する
必要がある
Chittagongは例外
5mm/10min, 1mm/min の強
雨が降水量の50%を超える

Mymensinghも夜間ピーク
明確なピークが見られる
AWSや雨量計を用いてメソ擾
乱を観測することができた

構造の解明に有効
ダウンロード

AWS, 雨量計の設置場所