All Title Author
Keywords Abstract


Simulation of High Impact Rainfall Events Over Southeastern Hilly Region of Bangladesh Using MM5 Model

DOI: 10.1155/2013/657108

Full-Text   Cite this paper   Add to My Lib

Abstract:

Simulation of high impact rainfall events over southeastern hilly region of Bangladesh has been carried out using Fifth-Generation PSU/NCAR Mesoscale Model (MM5) conducting two historical rainfall events, namely, 21 June, 2004 and 11 July, 2004. These extraordinary rainfall events were localized over the Rangamati region and recorded 304 mm and 337?mm rainfall on 21 June, 2004 and 11 July, 2004, respectively, over Rangamati within a span of 24?h. The model performance was evaluated by examining the different predicted and derived parameters. It is found that the seasonal monsoon trough has northerly position compared to normal and pass through Bangladesh extending up to northeast India for both cases. The heat low was found to be intense (996?hPa) with strong north-south pressure gradient (12–15?hPa). The analysis of the geopotential height field at 200?hPa shows that the Tibetan high is shifted towards south by 7-8° latitudes with axis along 22–25°N for both cases. The analysis of the wind field shows that the areas of high impact rainfall exhibit strong convergence of low level monsoon circulation ( 19–58?knots). The strong southwesterlies were found to exist up to 500?hPa level in both cases. The lower troposphere (925–500?hPa) was characterized by the strong vertical wind shear ( 9–18?ms?1) and high relative vorticity ( 20–40 × 10?5?s?1). The analysis also shows that the areas of high impact rainfall events and neighbourhoods are characterized by strong low level convergence and upper level divergence. The strong southwesterly flow causes transportation of large amount of moisture from the Bay of Bengal towards Bangladesh, especially over the areas of Rangamati and neighbourhoods. The high percentage of relative humidity extends up to the upper troposphere along a narrow vertical column. Model produced details structure of the spatial patterns of rainfall over Bangladesh reasonably well though there are some biases in the rainfall pattern. The model suggests that the highly localized high impact rainfall was the result of an interaction of the mesoscale severe convective processes with the large scale active monsoon system. 1. Introduction Rangamati (22.53°N, 92.20°E), the southeastern hilly city of Bangladesh (latitudes 20°34′–26°38′N and longitudes 88°01′–92°41′E), is situated on the western slopes of Mizo Hills and Arakan Mountains. Rangamati is very different in terms of topography from the rest of Bangladesh, as the city is built on the hilly regions. On 21 June, 2004 and 11 July, 2004, Rangamati received 304?mm and 337?mm rainfall within 24

References

[1]  A. D. Charles, “Scientific approaches for very short-range forecasting of severe convective storms in the United States of America,” International Workshop on Observation, pp. 181–188, 1993.
[2]  S. A. Braun and W.-K. Tao, “Sensitivity of high-resolution simulations of Hurricane Bob (1991) to planetary boundary layer parameterizations,” Monthly Weather Review, vol. 128, no. 12, pp. 3941–3961, 2000.
[3]  P. K. Patra, M. S. Santhanam, K. V. J. Potty, M. Tewari, and P. L. S. Rao, “Simulation of tropical cyclones using regional weather prediction models,” Current Science, vol. 79, no. 1, pp. 70–78, 2000.
[4]  N. L. Seaman, “Meteorological modeling for air-quality assessments,” Atmospheric Environment, vol. 34, no. 12–14, pp. 2231–2259, 2000.
[5]  S. Das, “Mesoscale and cloud resolving scale simulation of a heavy precipitation episode and associated cloud system using MM5 model,” in Weather and Climate Modeling, Singh, Ed., pp. 106–117, New Age International, New Delhi, India, 2002.
[6]  R. K. Jenamani, S. C. Bhan, and S. R. Kalsi, “Observational/forecasting aspects of the meteorological event that caused a record highest rainfall in Mumbai,” Current Science, vol. 90, no. 10, pp. 1344–1362, 2006.
[7]  A. K. Bohra, S. Basu, E. N. Rajagopal et al., “Heavy rainfall episode over Mumbai on 26 July 2005: assessment of NWP guidance,” Current Science, vol. 90, no. 9, pp. 1188–1194, 2006.
[8]  A. J. Litta, B. Chakrapani, and K. Mohankumar, “Mesoscale simulation of an extreme rainfall event over Mumbai, India, using a high-resolution MM5 model,” Meteorological Applications, vol. 14, no. 3, pp. 291–295, 2007.
[9]  M. N. Ahasan and A. Q. Khan, “Simulation of a flood producing rainfall event of 29 July 2010 over northwest Pakistan using WRF-ARW model,” Natural Hazards, vol. 69, no. 1, pp. 351–363, 2013.
[10]  J. Thomas, J. Galarneau, M. H. Thomas, and S. W. Jeffrey, Heavy Rains and Historic Flooding Over Pakistan in Late, synoptic conditions and physical mechanisms, 2010, http://www.esrl.noaa.gov/psd/people/thomas.galarneau/index.html.
[11]  P. J. Webster, V. E. Toma, and H. M. Kim, “Were the 2010 Pakistan floods predictable?” Geophysical Research Letters, vol. 38, no. 4, Article ID 046346, 2011.
[12]  K. Prasad, “Monsoon forecasting with a limited area numerical weather prediction system,” SMRC Scientific 11, SAARC Meteorological Research Centre (SMRC), 2005.
[13]  M. N. Islam, “Studies of summer monsoon rainfall using regional climate model PRECIS,” Scientific Report 22, SAARC Meteorological Research Centre (SMRC), 2008.
[14]  S. Das, “Composite Characteristics of Nor'Westers observed by TRMM & Simulated by WRF Model,” SMRC Scientific Report 25, SAARC Meteorological Research Centre (SMRC), 2009.
[15]  M. N. Ahasan, M. A. M. Chowdhury, and D. A. Quadir, “Prediction of high impact rainfall events of summer monsoon over Bangladesh using high resolution MM5 model,” Sri Lanka Journal of Physics, vol. 12, pp. 43–58, 2011.
[16]  M. N. Ahasan, M. A. M. Chowdhury, and D. A. Quadir, “Simulation of a heavy rainfall event on 14 September 2004 over Dhaka, Bangladesh using MM5 model,” Journal of Scientific Research, vol. 3, no. 2, pp. 261–270, 2011.
[17]  M. N. Ahasan, M. A. M. Chowdhury, and D. A. Quadir, “Simulation of a heavy rainfall event of 11 June 2007 over Chittagong, Bangladesh using MM5 model,” Mausam, vol. 64, no. 3, pp. 405–416, 2013.
[18]  M. N. Ahasan, K. M. Z. Rayhun, M. A. Mannan, and S. K. Debsarma, “Synoptic analysis of a heavy rainfall event over southeast region of Bangladesh using WRF model,” Journal of Scientific Research, vol. 5, no. 3, pp. 421–434, 2013.
[19]  G. A. Grell, J. Dudhia, and D. R. Stauffer, A Description of the 5th Generation Penn State/NCAR Mesoscale Model (MM5), NCAR/TN-398+STR, NCAR technical note, 1994.
[20]  J. Dudhia, D. Gill, K. Manning, W. Wang, and C. Bruyere, PSU/NCAR Mesoscale Modeling System (MM5 VerSion 3) Tutorial Class Notes and User's Guide, National Center for Atmospheric Research, Boulder, Colo, USA, 2002.
[21]  R. A. Anthes, “A cumulus parameterization scheme utilizing a one dimensional cloud model,” Monthly Weather Review, vol. 105, pp. 270–286, 1977.
[22]  S.-Y. Hong and H.-L. Pan, “Nonlocal boundary layer vertical diffusion in a medium-range forecast model,” Monthly Weather Review, vol. 124, no. 10, pp. 2322–2339, 1996.
[23]  J. Dudhia, “Numerical study of convection observed during the Winter Monsoon Experiment using a mesoscale two-dimensional model,” Journal of the Atmospheric Sciences, vol. 46, no. 20, pp. 3077–3107, 1989.
[24]  D. A. Quadir, M. A. Hussain, and M. N. Ahasan, Climatic Characteristics of Temperature and Precipitation of Bhutan, vol. 58, no. 1, MAUSAM, 2007.
[25]  M. N. Islam and H. Uyeda, “Use of TRMM in determining the climatic characteristics of rainfall over Bangladesh,” Remote Sensing of Environment, vol. 108, no. 3, pp. 264–276, 2007.

Full-Text

comments powered by Disqus