48 4.3(a) Time variation of observed and model-simulated wind (m/s) for TC. OR 4.30) Model simulated east-west cross section of vertical profile of horizontal. 88 Al 4.17(i) Model simulated east-west cross-section of vertical profile of vertical Model simulated east-west cross-section of vertical profile of horizontal.
Abstract
INTRODUCTION
Objectives & Scope of the Research
Efforts will be made to adapt the physical parameterization schemes and boundary layer parameterization to improve the performance of the models. The main objective of the study is to determine the most suitable model parameterization schemes for the simulation of the TOs over the Bay of Bengal.
Social and Economic Benefit of the Research
Chapter-1 contains an introduction describing the geographical setting of the Bay of Bengal and adjacent land masses, the objectives and scope of the study and explains how the results of the research will yield social and economic benefits. Chapter-4 contains the results and discussion on the genesis, evaluation and movement tracking of selected Bay of Bengal tropical cyclones based on the results obtained.
LITERATURE REVIEW
Numerical Weather Prediction Model
Manipulating the vast data sets and performing the complex calculations necessary for modern numerical weather forecasting requires some of the world's most powerful supercomputers. Although post-processing techniques such as model production statistics (MOS) have been developed to improve the handling of errors in numerical predictions, a more fundamental problem lies in the chaotic nature of the partial differential equations used to simulate the atmosphere.
History of Numerical Weather Prediction Model
These newer models include more physical processes in simplifications of the equations of motion in numerical simulations of the atmosphere. Since the 1990s, model ensemble forecasts have been used to help define forecast uncertainty and to extend the window in which numerical weather prediction is feasible further into the future than otherwise possible.
Description of WRF model
- Introduction
- Major Features of the ARW System, Version 3
- WRF Model Physics
- Microphysics
- Kessler Scheme
- Purdue Lin Scheme
- WRF Single-Moment 3-class (WSM3) Scheme
- WRF Single-Moment 5-class (WSM5) Scheme
- WRF Single-Moment 6-class (WSM6) Scheme
- Eta Grid-scale Cloud and Precipitation (2001) scheme
- Thompson et al. scheme
- Goddard Cumulus Ensemble Model scheme
- Morrison et al. 2-Moment scheme
- Cumulus parameterization
- Kain-Fritsch scheme
- Betts-Miller-Janjic scheme
- Grell-Devenyi Ensemble Scheme
- Surface Layer
- Planetary Boundary Layer
- Land-Surface Model
Memory, ie. the size of the fourth dimension in these arrays is allocated depending on the needs of the selected scheme, and advection of the species also applies to all those required by the microphysics option. Note that large eddy modes with interactive surface fluxes are not yet available in ARW, but are planned for the near future.] The land surface models have different d6grees of sophistication in handling thermal and moist fluxes in multiple layers of the land and can also handle vegetation- , root and canopy effects and prediction of surface snow cover.
Tropical cyclone
However, there is no significant difference between the maximum sustained wind reported on different bases using different averaging methods. A low pressure system over the Indian region is classified based on the maximum sustained wind speed associated with the system and the pressure deficit/number of closed isobars associated with the system. Pressure criteria are used when the system is over land and wind criteria are used when the system is over sea.
The system is called low if it has a closed isobar in the interval of 2 hPa. Considering the wind criteria, a system with wind speed of 17-27 knots is called a depression and a low pressure system with a sustained maximum of 3 minutes. A system with maximum 3 minute sustained surface winds of 34 knots or more is called a cyclonic storm.
When the maximum sustained 3-minute surface winds exceed 119 knots, the low pressure system is called a "Super Cyclone" over the northern Indian Ocean. Joint Typhoon Warning Center for typhoons attaining maximum sustained 1-minute surface winds of at least 130 knots (65 m/s).
Tropical Cyclone Formation
This is the equivalent of a severe Category 4 or Category 5 Saffir-Simpson storm in the Atlantic basin or a severe Category 5 tropical cyclone in the Australian basin.
0`0 rimi,
Eye of the cyclone
Although the wind is calm at the axis of rotation, strong winds can extend well into the eye. The eye is surrounded by the "eyewall," the roughly circular ring of deep convection that is the region of highest surface winds in the tropical cyclone. The eye is composed of slowly sinking air, and the eyewall has a net upward flow as a result of many moderate - sometimes strong - updrafts and downdrafts.
One idea suggests that the eye forms as a result of the downward pressure gradient associated with the weakening and radial spread of the tangential wind field with height (Smith, 1980). Another hypothesis suggests that the eye is formed when latent heat release occurs in the eye wall, which forces. Another feature of tropical cyclones that probably plays a role in the formation and maintenance of the eye is the eyewall convection.
Eventually the band moves toward the center and surrounds it, forming the eye and eye wall. Just as the inner eyewall forms, the convection surrounding the eyewall can organize into separate rings.
Model Selection
- Act of Procedure
- Experiments on simulation of different TC events
- Domain setup and Model Physics
- Initial Data Sources
- Very severe cyclone Nargis (26 April- 02 May, 2008)
- Cyclonic Storm Thane (25-31 December, 2011)
- Cyclonic Storm Mahasen over Bay of Bengal (10 - 16 May, 2013)
These observed characteristics of tropical cyclones Nargis, Thane and Mahasen are illustrated in the following subsections and 3.5.3), respectively. VSCS 'Nargis devastated a large part of the lower Irrawaddy river delta region. It moved northwest and intensified into a deep depression in the evening of the same day.
Under the influence of the anticyclonic circulation in the east, the cyclonic storm initially changed its direction of movement from northwest to north and then to north-northeast on May 13 and 14, respectively. On May 15, it further came under the influence of the mid-latitude westerly trough running roughly along 770E, which further helped strengthen the north-northeastward motion of the cyclonic storm. As this trough approached on the 16th, the north-northeastward speed of the cyclonic storm increased considerably, to about 40-50 km/h.
It was one of the longest tracks over the northern Indian Ocean in recent times after the very violent cyclonic storm, Phet over the Arabian Sea (May 31-June 7, 2010). Due to the faster movement and the unfavorable weather, the severity of the cyclonic storm was relatively less.
SENSITIVITY TEST
- Simulation of TC Nargis
- Pressure Field
- Wind Field
It is rather difficult to find any ratification of model-simulated SLP with real observables from the sea ahead of land, since TOs develop over large oceanic areas where observations are rare or unavailable. It can be seen from the figure that the model-simulated SLP gradually decreases with time and reaches a maximum intensity of 960 hPa at 21 UTO on 01 May 2008 and then gradually increases. The resulting MWS simulated by the model are lower than the observed wind until the first 42 h from the initial one, and then increase from 48 h to 75 h, indicating a slight fluctuation, and then gradually decrease.
The figures show that the pattern has an asymmetrical wind distribution with strong wind bands on the left and right sides, near the center of a north-moving storm. The wind flow in the core area shows an almost circular feature with minimum wind speed at the center. May 01 and 21 UTC on May 1, 2008, indicating that the vertical speed of wind changes with the change of time at different levels.
At the 300 hPa level, a slight cyclonic circulation on the right side of the TO and a weak outflow on the left, which is noticeable in Figure 4.3 (h). At the 100 hPa level, a strong outflow from the central part of the cyclone is predicted in Figure 4.3 (i).
WVA 0 FEOEiRci;2 1 21ei,C) 1
- Vorcity Field
- Temperature Anomaly
- Water Vapor Mixing Ratio
- Rainfall Pattern
- Track Pattern
- Simulation of TC Thane
- Pressure Field
- Wind Field
- Vorcity Field
- Temperature Anomaly
- Water Vapor Mixing Ratio
- Rainfall Pattern
- Simulation of TC Mahasen
- Pressure Field
- WIND FIELD
- Voticity Fied
- Tmperature Anomaly
- Water Vapor Mixing Ratio
- Rainfall Pattern
- Track Pattern
The simulated anomaly demonstrates that the warm core is visible in the lower troposphere and negative anomaly in the middle levels. The simulated anomaly demonstrates that the warm core is visible in the upper and lower troposphere and negative anomaly in the middle levels. The simulated anomaly demonstrates that the warm core is visible in the upper and lower troposphere and negative anomaly is embedded at the middle and lower levels.
The simulated anomaly shows that the warm core is visible in the upper troposphere and the negative anomaly in the mid-levels. The wind at the 300 hPa level shows a slight cyclonic circulation on the lower Ieftt side of the TC and a strong outflow to the upper left, as shown in Fig. 4.10 (e). The simulated anomaly shows that a warm core is visible in the upper troposphere and that any negative anomaly is visible.
The simulated anomaly shows that the warm core is visible in the upper troposphere and a negative anomaly at the upper levels. The simulated anomaly shows that the warm core is visible in the upper troposphere and the negative anomaly is located almost at the mid-level. At the 300 hPa level, the wind shows a small cyclonic circulation in the lower left of the TO and a visible outflow in the upper right, as shown in Figure 4.17(e).
At the 100 hPa level, a strong outflow is seen from the central part of the cyclone shown in Figure 4.17(f).
Conclusion
- Conclusions
In this study, the Advanced Research WRF (ARW) model using 9 km single domain has been used for the simulation of three tropical cyclones namely Nargis, Thane and Mahasen using six combinations of two PBLs (YSU & MYJ) and three OPs (KF, BM & GD). To understand the dynamics of sensitivity, intensity (wind & sIp), eddy, temperature anomaly, accumulated precipitation, water vapor mixing ratio and track of the mentioned TCs have been simulated and thereby analyzed. The broad conclusions materialized in this study are presented in the following: From this study, it is clear that the YSU PBL scheme with KF OP scheme shows less track and intensity errors out of the six combinations.
The YKF experiment could replicate many of the observed characteristics, such as vorticity and water mixing ratio, that conform to cyclone development. From the study of vertical structural features of the cyclone inner core, it is clear that robust features are observed with the YKF combination that produced intense horizontal wind speed and strong convergence with intense updrafts within the warmer cyclone core. The enhanced updraft and storm intensification in the YKF experiment can be attributed to the feedback mechanism between low warm air convergence, latent heat release in the eyewall, and a corresponding decrease in surface pressure in the storm's inner core.
IMD Atlas (2008) Tracks of storms and depressions in the Bay of Bengal and Arabian Sea, India Meteorological Department, New Delhi, India. V Hobbs (1984): Mesoscale and microscale structure and organization of clouds and precipitation in midlatitude cyclones XII: A diagnostic modeling study of precipitation development in narrow cloud-topped rainbands.
