Agricultural Research Management Information System

Home
Research Summary
Search
About Us
- ARMIS
- Brochure
Contact Us
Report
User Request
Data Input
Help
- Operation Manual
  - PDF
  - Video
- Program Area & Commodity
We have reached 37600 number of research entries at this moment.

- Logout

Research Detail

Home
Research
Detail

Synoptic Analysis of a Heavy Rainfall Event Over Southeast Region of Bangladesh Using Wrf Model

M. N. Ahasan
SAARC Meteorological Research Centre (SMRC), Dhaka, Bangladesh

K. M. Z. Rayhun
Department of Physics, Jahangirnagar University, Dhaka, Bangladesh

M. A. Mannan
SAARC Meteorological Research Centre (SMRC), Dhaka, Bangladesh

S. K. Debsarma
SAARC Meteorological Research Centre (SMRC), Dhaka, Bangladesh

Abstract/ Executive Summary:

Synoptic analysis of the heavy rainfall event of 7 September 2011 was carried out using the Weather Research and Forecasting (WRF) Model. This extraordinary rainfall event was localized over the southeast region of Bangladesh and recorded rainfall was 331 mm at Chittagong and 226 mm at Sandwip within a span of 24-h. The model was run at 9 km horizontal resolution using KF CPS with YSU PBL scheme. The model performance was evaluated by examining the different predicted parameters like mean sea level pressure, upper and lower level circulations, wind shear, relative vorticity, convergence, moisture and rainfall. The rainfall was validated with TRMM 3B42RT and observed rainfall data. The results indicate that the WRF model was able to simulate the heavy rainfall event, and associated synoptic features reasonably well, though there are some biases in the rainfall pattern. The results suggest that the highly localized heavy rain over southeast Bangladesh was the result of an interaction of the large scale monsoon system with cyclonic disturbances and required moisture have been supplied from the Bay of Bengal. The low level flow facilitated strong convergence over the region due to horizontal wind shear, which resulted in maintenance of the storms.

Keywords: Heavy Rainfall; WRF Model; Simulation; Validation; TRMM.

Location: Southeast region of Bangladesh

Start Date:

End Date:

Program Area: Socio-economic and Policy

Non-commodity: Performance

Objectives:

The primary objective of this study is to identify and document the possible synoptic and environmental characteristics of the heavy rainfall events of 7 September 2011 over southeast coastal region of Bangladesh. The secondary objective is to test the performance of the WRF model to simulate the selected rainfall event.

Methodology:

Model experimental setup: The WRF model is run on single domain at 9 km horizontal resolution. The domain size is taken 117x134 km. The domain is centered (23.50°N, 90.00°E) over Dhaka, Bangladesh to represent the regional-scale circulations and to solve the complex flows in this region. There are 27 vertical layers. The model is run using the Kain-Fritsch (new Eta) scheme for cumulus parameterization, Yonsei University (YSU) scheme for the boundary layer parameterization, WSM 3 class Simple Ice schemes for microphysics and RRTM for longwave and Dudhia for short wave radiation scheme for the selected case. The physics and dynamics employed in the model for the present study. The initial condition of the model simulation is taken as 0000 UTC of 06 September 2011 (about 48-h before of the event).Data used The United States Geological Survey (USGS) Global datasets with 30sec horizontal resolution were used to create terrain and land-use field. The Final (FNL) Global ModelTropospheric data of NCEP with the 1⁰×1⁰ resolution were used as the initial and lateral boundary condition. The daily 0.25° x 0.25° resolution TRMM 3B42RT rainfall data have been downloaded from website of NASA [19] to justify the model simulated rainfall structure, development time and location. The daily observed rainfall data have been collected from the archive of Bangladesh Meteorological Department (BMD) to compare or validate the model output. The Meteosat-5 cloud images are also used to see the signature of cloud activities and moisture presence over the study area.

The model outputs help to investigate the synoptic and environmental characteristics for the event. The mean sea level pressure, low level and upper level wind flow, horizontal and vertical profile of moisture flux, low level relative vorticity, vertical wind shear of u component of wind, convective available potential energy, convective inhibition energy and rainfall etc fields have been investigated. The high amount of rainfall occurred during the end of the day. Thus all synoptic maps are prepared for the 2100 UTC (peak time of heavy rainfall spell) of 7 September 2011. Observed daily rainfall data of BMD and daily TRMM 3B42RT rainfall data have been used to validate / compare the model simulated rainfall. Both spatial and temporal comparison methods have been used to compare the model simulated rainfall with observed rainfall.

Source of Information: J. Sci. Res. 5 (3), 421-434 (2013)

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Finally, it may be concluded that the WRF Model (Version 3.2.1, Release August 2010) might be able to simulate the heavy rainfall event over southeast region of Bangladesh and associated synoptic features reasonably well, though there are some spatial and temporal biases in the simulated rainfall pattern.

Knowledge Management: Journal