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Characteristics of severe thunderstorms over Bangladesh and neighborhood: Observations & WRF-ARW model simulations. Senaka Basnayake. Asian Disaster Preparedness Centre Thailand. WRF Lecture Series, 20 – 24 September 2010 @ BCCR - Norway.

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slide1

Characteristics of severe thunderstorms over Bangladesh and neighborhood: Observations & WRF-ARW model simulations

Senaka Basnayake

Asian Disaster Preparedness Centre

Thailand

WRF Lecture Series, 20 – 24 September 2010 @ BCCR - Norway

history of adpc
History of ADPC

Established in 1986, at the initiative of WMO, UNDP and UNOCHA

Served as the Outreach Center of Asian Institute of Technology, 1986-1999

Independent international foundation, July 1999

Inter-governmental charter signed, February 2005

Over 100 staffs,19 nationalities

slide5

ADPC Organization Chart

Board of Trustees

23 Members 16 Countries

International

Advisory

Council (IAC)

95 members

Regional

Consultative

Committee (RCC)

32 Members

26 Countries

Executive Committee

Office of the Executive Director (OED)

Climate Risk Management (CRM)

Urban Disaster Risk Management (UDRM)

Public Health in Emergencies (PHE)

Disaster Management Systems (DMS)

Training Resource Group (TRG)

slide6

Severe thunderstorms

or

Nor’westers

favorable synoptic conditions for nor westers
Favorable Synoptic conditions for Nor’westers
  • Presence of an active elongated trough of low over the Gangetic plains of north India across north Bangladesh on the mean seal level pressure chart
  • Presence of southerly low level jet with a pole ward meridional component in the lower tropospheric wind flow
  • High magnitude of moisture in the humidity field intruding from the Bay of Bengal into Bangladesh and thereafter north India
  • Presence of sub-tropical jet stream with strong vertical wind shear in the low to middle troposphere levels over Bangladesh and neighborhood
  • Intrusion of high convective available potential energy (CAPE) from the Bay of Bengal into Bangladesh and presence of a low convective inhibition energy (CINE) regime.
  • A pocket of strong warm temperature advection at 850 hpa and cold temperature advection at 300 hpa
slide9

2009

pre-monsoon

slide11

2009 pre-monsoon season

N (10)

(29) NW

NE (9

8) W

E (3)

(4) SW

SE (2)

S (3)

41 – 60 km/h ~ 41, 61 – 90 km/h ~ 27, 91 – 120 km/h ~ 2

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Week instability CAPE < 1000 J/kg

Moderate instability 1000 J/kg < CAPE < 2500 J/kg

Strong instability CAPE > 2500 J/kg

Threshold Value >1500

0 > (NEGATIVE)

CAPE

CINE

Very Stable atmospheric condition LI ≥ 6.0

Stable condition - unlikely to form thunderstorms 1.0 < LI < 6.0

Slightly Unstable - possible thunderstorms with mechanical lifting -2.0 < LI < 0.0

Unstable - likely to form thunderstorms with strong mechanical lifting -6.0< LI < -2.0

Very Unstable - likely to form severe thunderstorms with strong mechanical lifting LI < -6.0

Possible showers or thunderstorms SI ≤ +3.0

Possible severe convective activity SI ≤ -3.0

SI

LI

slide13

TTI

SWEAT

Indicator of occurrence of thunderstorm TTI ≥ 40

Indicator of occurrence of thunderstorm with tornado intensity TTI ≥ 47

Indicator for potential strong convection SWEAT = +250

Indicator for potential severe thunderstorms SWEAT = +300

ndicator for potential tornados SWEAT = +400

Thunderstorms unlikely due to too much wind shear BRN < 10

Possibility of Supercells 10 < BRN < 45

Storms with multicells than supercells BRN > 45

BRN

slide15

(d)

(e) (f)

slide17

Weather Research and Forecasting (WRF)

  • Developed by the Mesoscale and Microscale Meteorology Division of National Centre for Atmospheric Research (NCAR) of USA
  • National Centre for Environment Prediction (NCEP) real time analysis (FNL) data as initial and lateral boundary conditions (LBCs) at six hourly intervals
  • Domain parameters & Model physics;
  • Horizontal Resolution : 9 km
  • No. of grid point along X : 153
  • No. of grid point along Y : 139
  • No. of Vertical sigma levels : 27
  • Iterative Time step : 50 seconds
  • Integration scheme : 3rd order Runga-Kutta
  • mp_physics : WSM 3
  • Cumulus parameterization : Kain-Fritch scheme
  • Sf_sfclay_physics : Monin-Obukhov with
  • Carslon-Bolan viscous sub-layer option
  • Sf_surface_physics : Noah LSM
  • ra_lw_physics : RRTM
  • ra_sw_physics : Dudhia
  • Boundary layer parameterization : Yonsei University scheme
slide28

Concluding Remarks….

  • Convective indices at Patna, Ranchi, Guwahati and Agartala stations are good indicators for identifying possible thunderstorm days over Bangladesh as the systems initiate or conceive over West Bengal, Assam and Meghalaya regions.
  • Some of the factors which are essential for triggering of Nor’westers such as low level moist southerly jet from the head Bay of Bengal, mid-trophospheric cold dry westerly trough, etc. are well simulated by the model.
  • WRF-ARW model is able to simulate some salient features of thunderstorms with some temporal and spatial shifting.
acknowledgement
Acknowledgement
  • SAARC Meteorological Research Centre (SMRC)
  • Bangladesh Meteorological Department (BMD)
  • Dr. Someshwar Das and research team at SMRC
slide31

Mission

• raising awareness and enhancing knowledge and

skills

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• strengthening sustainable institutional mechanisms

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• facilitating exchange of information, experience and

expertise

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• developing and demonstrating innovative disaster

risk reduction practices

slide32

Goals

  • Mainstream Disaster Reduction in Development
  • Build and Strengthen Capacity
  • Facilitate Partnerships and Exchange of Experiences
  • Be recognized as a Proactive and ResponsiveRegional Resource
  • Achieve Quality Service Through a Team Approach
adpc highlights
ADPC Highlights

ADPC Projects and Programs:

  • Longest serving regional center globally
  • Proactiveand responsive regional resource center
  • 81 projects and programs across Asia
  • Regional Early Warning Center provides services to 27 countries in the region