A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in the Department of Physics, Khulna University of Engineering & Technology. This is to confirm that the thesis entitled “Impact of Environmental Moisture on the Intensification of Tropical Cyclone in the Bay of Bengal Using WRF-ARW Model” has been carried out by SUMON KUMAR DAS in the Department of Physics, Khulna University of Engineering & Technology, Khulna, Bangladesh. Mahbub Alam, Professor, Department of Physics, Khulna University of Engineering & Technology, Khulna, for his kind guidance and supervision and for his constant encouragement during the research work.
Shibendra Shekher Sikder, Head, Department of Physics, Khulna University of Engineering and Technology for his strong support in various ways throughout the period of my studies in this department.
List of Table
Nomenclature
ABSTRACT
Introduction
The increased release of latent heat in the outer spiral rainbands reduced the intensity but increased the size of the TC. Evans et al. (2012) constructed a relationship between sea surface temperature (SST) and OLR using atmosphere–ocean general circulation models (AOGCMs). The objective of this research is to investigate the effects of the aforementioned intensification parameters on the ambient moisture of TCs in the Bay of Bengal.
An attempt will be made to identify the effect of environmental moisture on the movements and intensification of tropical cyclones in the Bay of Bengal.
Literature Review
- Tropical Cyclone (TC)
- Classification of Tropical Cyclone
- Life Cycle of Tropical Cyclones
- Environmental moisture on the intensification of TC .1 Front
- Rear
- Temperature Anomaly
- Sea Level Pressure (SLP)
- Water Vapor Mixing Ratio (WVMR)
- Wind Speed
- Convective Available Potential Energy (CAPE)
The RH is the amount of water vapor (moisture) in the air compared to the maximum amount that the air can contain at a certain temperature. At the other end of the scale, when there is no water vapor in the air, the RH is 0% regardless of temperature. The factors that influence SH are the partial pressure of water vapor, PW, and the total pressure of the water vapor/air mixture, P.
Note that the partial pressure of water vapor cannot be greater than the total pressure of the water vapor/air mixture.
T CIN T
Weather Research & Forecasting (WRF) Model
- WRF Single-Moment 6-class Scheme (WSM6)
- Thompson et al., Scheme
- WRF Double-Moment 6-class (WDM6) Scheme
- NSSL-1 Microphysics Scheme
- Cumulus Parameterization Schemes
- Kain - Fritsch (KF) Scheme
- Planetary Boundary Layer (PBL)
- Yonsei University (YSU) Scheme
- Map Projection
- Mercator projection
- Shortwave Radiation
- Downward long wave radiation flux
Memory, i.e. the size of the fourth dimension in these arrays is assigned according to the needs of the selected scheme, and species advection also applies to all those required by the microphysics option. Outgoing longwave radiation (OLR) is the emission of terrestrial radiation into space from the top of the Earth's atmosphere. Note that if s 1, some of the incoming longwave radiation is reflected from the surface.
Longwave radiation flux is an important part of the surface heat budget, generally represented by εstr4.
Chapter-3
Model Description and Methodology
Model Description
To investigate the impact of moisture of TC, we used these schemes for the simulation of TC Hudhud and TC Mora. Initial conditions Three-dimensional real data (FNL: 1°× 1°) Lateral boundary conditions Specified options for real data. Top boundary conditions Gravitational wave absorbing Bottom boundary conditions Physical or free-slip Diffusion and damping Simple diffusion.
The NCEP FNL data are interpolated to the model horizontal and vertical grids and the model is integrated for and 96-hour period for Hudhud and Mora. 8 experiments were performed in each case using different microphysics schemes (e.g. WSM6-class graupel scheme, Thompson graupel, WDM6 scheme and NSSL mom-1) in combinations with Kain-Fritsch (KF) CP scheme with different initial conditions. The different periods for different cyclones were characterized by TC formation to dissipation.
The model simulated MSLP, maximum wind at 10 m level, track, convective available potential energy (CAPE), convective inhibition (CIN), water vapor mixing ratio (WVMR), temperature deviation, relative humidity (RH), specific humidity (SH). , Wind speed (WS), Wind direction (WD) were analyzed. We calculated the impact of ambient moisture on the intensification of TC in different regions using the software Grid Analysis and Display Systems (GrADS). The Grid. Data from different datasets can be graphically overlaid, with correct spatial and temporal registration.
Data can be displayed using a variety of graphical techniques: line and bar graphs, scatter plots, smooth contours, shaded contours, streamlines, wind vectors, grid boxes, shaded grid boxes, and model plots of the station. We have graphed the data in Excel at every 24-hour interval to observe the changing scenario of energy and its fluxes for TC movement.
Results and Discussion
Tropical Cyclone Hudhud
- Synoptic Situation of Tropical Cyclone Hudhud
- Minimum Sea Level Pressure (MSLP)
- Maximum Wind Speed (MWS) at 10 m level
- Track of TC Hudhud
- Water Vapor Mixing Ratio (WVMR)
- Relative Humidity (RH)
- Temperature anomaly
- Wind Speed (WS) at different pressure level
- Wind Direction (WD)
- Convective Available Potential Energy (CAPE)
- Convective Inhibition (CIN)
- Synoptic situation of Tropical Cyclone Mora
- Minimum Sea Level Pressure (SLP)
- Track of TC Mora
- Specific Humidity (SH)
- Water Vapor Mixing Ratio (WVMR)
- Relative Humidity (RH)
- Temperature Anomaly
- Wind Speed (WS) at different pressure level
- Convective Available Potential Energy (CAPE)
The similar pattern of MSLP is found for all MPs with the initial conditions at 0000 UTC of 6, 7, 8, and 9 October. The simulated track is deviated to the right from observed for all MPs with the initial conditions at 0000 UTC of 6 October 2014. The simulated track for all MPs is deviated to the right for the initial conditions at 0000 UTC of 7 October.
For the initial conditions at 0000 UTC of 9 October, the area-averaged WVMR increased at the leading position ( Figure 8d ) for all MPs and reached maximum at 0600 of 12 October for different MPs with few exceptions. The area-averaged WVMR ( Figure 8h ) is found to increase until 1200 UTC of 9 October and thereafter shows almost constant values for all MPs for the initial conditions of 0000 UTC of 9 October. Model-simulated vertical profiles of area-averaged RH (%) at the leading position with four different MPs coupled with KF scheme are shown in Figures 9(a–p) for initial conditions at 0000 UTC of 6, 7, 8 and 9 October 2014 presented.
For the initial conditions 0000 UTC on 8 October, the area-averaged RF is found to increase with advancing days for all MP schemes during 9–11 October (Figure 9(i–l)) and the. The vertical variation of areal average RH is found to increase for all MP schemes during 9-11. October (Figure 9(m–p)) and decrease on October 12 with a small exception for the initial conditions at 0000 UTC on October 9. The area average RF is found to increase for all MP schemes during 9-12. October (Figure 10(m-p)) for the 0000 UTC 9 October initial conditions.
The area-averaged CAPE is found to increase from October 9 to 12 (Figure 18(i-l)) for the initial conditions of 0000 UTC of October 8. The area-averaged CAPE is found to decrease between October 9 and 10 (Figure 18(m-p)) and increase until October 12 for all schemes, with few exceptions for the initial 0000 UTC conditions of October 9. The area-averaged CIN is found to increase for WSM6, Thompson, WDM6, and NSSL schemes during October 9-12 (Figure 19(m-p)), with few exceptions for the initial 0000 UTC conditions of October 9.
The zonal mean CIN was found to increase for all MP schemes between 8–12 October (Figure 20(i–l) ) and 9–12 October. October (Figure 20(m-p)) with the small exception of the WDM6 scheme for the 0000 UTC initial conditions on 8 and 9 October. For the initial conditions at 0000 UTC 28 May, the zonally averaged WVMR at the front position ( Fig. 28d ) increased. The zonal mean CIN is found to decrease for all MP schemes between 26 and 30 May ( Figure 39(e–h) ), except for the NSSL scheme for the 0000 UTC 26 May initial conditions.
Conclusions
This suggests that the WVMR in front position is increased in the direction of the movement of TCs. The temperature has increased at all vertical levels for all MPs in front of TC Hudhud under all initial conditions with few exceptions. The temperature is found to increase at the front of TC Mora from 650-150 hPa and decrease from 900-700 hPa for all initial conditions of the model run, with small deviations over time.
At the trailing position, it found two peaks, one at 750 hPa and another at 200 hPa and one trough at 400 hPa level where the area mean temperature continuously decreased and reached negative for all initial conditions and for all MP schemes . The areal mean WS for TC Hudhud and Mora at the leading position is found to increase from 950 to 250 hPa levels for all MPs before crossing the land and after the crossing is found to decrease for all initial conditions. It is found that the area-averaged WS at the trailing position of TC Hudhud decreases from 950 to 450 hPa levels for all MPs for all initial conditions and for TC Mora it decreases and reaches minimum at 400 hPa level for all MPs for all initial conditions.
Due to the northeasterly to easterly wind from surface to 200 hPa level during 8-10 October 2014 and southeasterly wind on 11 October at the leading position, the TC Hudhud moved towards the east coast of India and for southwesterly wind in the upper troposphere during 27-29 May 2017 and westerly wind at all levels on 30 May, the TC Mora moved towards Bangladesh coast. The area mean CAPE at lower troposphere increased for all LP schemes during 9-10 October for TC Hudhud and 27-29 May for TC Mora in the leading position. The CIN at the leading and trailing position at or below 900 hPa level for TC Hudhud and TC Mora is found to increase during the onset of the initial conditions of model run and when the cyclone is near the front it is found to decrease, but the simulated values of CIN are insignificant, which is suitable for the intensification of TCs.
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