scholarly journals Mesoscale interactions during the genesis and intensification of October 1999 Orissa super cyclone

MAUSAM ◽  
2021 ◽  
Vol 57 (1) ◽  
pp. 31-36
Author(s):  
T. N. VENKATESH
Keyword(s):  
Tropical Cyclone ◽  
Tropical Cyclones ◽  
Large Scale ◽  
Tropical Cyclone Genesis ◽  
Vortex Interactions ◽  
Formation Stage ◽  
The Pacific ◽  
Axisymmetric Structure ◽  
Super Cyclone ◽  
Cyclone Genesis

  lkj & ;g loZfofnr rF; gS fd iw.kZ fodflr m".kdfVca/kh; pØokr esa izk;% v{klekuqikfrd lajpuk ikbZ tkrh gS tcfd pØokr ds cuus dh voLFkk esa vR;kf/kd vlaxfr fn[kkbZ nsrh gSA iz’kkar egklkxj esa gky gh esa fd, x, v/;;uksa vkSj izs{k.kksa ls ;g irk pyk gS fd m".kdfVca/kh; pØokrksa dh mRifRr dk irk yxkkus esa eslksLdsy dh ijLij fØ;k,sa egRoiw.kZ Hkwfedk fuHkk ldrh gSaA m".kdfVca/kh; pØokr dh mRifRr ds vk/kqfud fl)kar Hkh mi;qZDr iwoZdfFkr rF; ij vk/kkfjr gSaA bl 'kks/k&Ik= esa vkbZ- vkj-  mixzg ls izkIr foEckoyh vkSj cM+s iSekus ij Hkzfeyrk ds {ks=ksa dk fo’ys"k.k izLrqr fd;k x;k gSA ftuesa ;g ns[kk x;k gS fd 1999 esa mM+hlk esa vk, egkpØokr dh Hkh izkjfEHkd voLFkkvksa esa eslksLdsy ls pØokr ds coaMj dh ijLij fØ;kvksa dk irk yxk gSA  It is well known that a mature tropical cyclone is known to have a nearly axisymmetric structure but that the formation stage exhibits considerable asymmetry. Recent studies and observations in the Pacific indicate that mesoscale interactions could play an important role in the genesis of tropical cyclones. Modern theories of tropical cyclone genesis are also based on this premise. In this paper, an analysis of the IR satellite imagery and large scale vorticity fields is presented, which shows that mesoscale vortex interactions occur in the early stages of the 1999 Orissa super cyclone also.

scholarly journals Tropical cyclone genesis across palaeoclimates

2015 ◽  
Vol 11 (1) ◽  
pp. 181-220 ◽  
Author(s):  
J. H. Koh ◽  
C. M. Brierley
Keyword(s):  
Carbon Dioxide ◽  
Tropical Cyclone ◽  
Tropical Cyclones ◽  
Large Scale ◽  
Climate Models ◽  
Tropical Cyclogenesis ◽  
Tropical Cyclone Genesis ◽  
Inter Tropical Convergence Zone ◽  
Potential Index ◽  
Cyclone Genesis

Abstract. Tropical cyclone genesis is investigated for the Pliocene, Last Glacial Maximum (LGM) and the mid-Holocene through analysis of five climate models. The genesis potential index is used to estimate this from large scale atmospheric properties. The mid-Pliocene and LGM characterise periods where carbon dioxide levels were higher and lower than pre-industrial respectively, while the mid-Holocene differed primarily in its orbital configuration. The number of tropical cyclones formed each year is found to be fairly consistent across the various palaeoclimates. Although there is some model uncertainty in the change of global annual tropical cyclone frequency, there are coherent changes in the spatial patterns of tropical cyclogenesis. During the Pliocene and LGM, changes in carbon dioxide led to sea surface temperature changes throughout the tropics, yet the potential intensity of tropical cyclones appears relatively insensitive to these variations. Changes in tropical cyclone genesis during the mid-Holocene are observed to be asymmetric about the Equator: genesis is reduced in the Northern Hemisphere, but enhanced in the Southern Hemisphere. This is clearly driven by the altered seasonal insolation. Nonetheless, the enhanced seasonality may have driven localised effects on tropical cyclone genesis, through changes to the strength of monsoons and shifting of the inter-tropical convergence zone. Trends in future tropical cyclone genesis are neither consistent between the five models studied, nor with the palaeoclimate results. It is not clear why this should be the case.

Developing versus Nondeveloping Disturbances for Tropical Cyclone Formation. Part II: Western North Pacific

2012 ◽  
Vol 140 (4) ◽  
pp. 1067-1080 ◽  
Author(s):  
Bing Fu ◽  
Melinda S. Peng ◽  
Tim Li ◽  
Duane E. Stevens
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
Large Scale ◽  
Relative Vorticity ◽  
Tropical Cyclone Genesis ◽  
Horizontal Shear ◽  
The North ◽  
Thermodynamic Variables ◽  
Cyclone Genesis

Global daily reanalysis fields from the Navy Operational Global Atmospheric Prediction System (NOGAPS) are used to analyze Northern Hemisphere summertime (June–September) developing and nondeveloping disturbances for tropical cyclone (TC) formation from 2003 to 2008. This is Part II of the study focusing on the western North Pacific (WNP), following Part I for the North Atlantic (NATL) basin. Tropical cyclone genesis in the WNP shows different characteristics from that in the NATL in both large-scale environmental conditions and prestorm disturbances. A box difference index (BDI) is used to identify parameters in differentiating between the developing and nondeveloping disturbances. In order of importance, they are 1) 800-hPa maximum relative vorticity, 2) rain rate, 3) vertically averaged horizontal shear, 4) vertically averaged divergence, 5) 925–400-hPa water vapor content, 6) SST, and 7) translational speed. The study indicates that dynamic variables are more important in TC genesis in the WNP, while in Part I of the study the thermodynamic variables are identified as more important in the NATL. The characteristic differences between the WNP and the NATL are compared.

scholarly journals Impact of Large-Scale Dynamic versus Thermodynamic Climate Conditions on Contrasting Tropical Cyclone Genesis Frequency

2017 ◽  
Vol 30 (22) ◽  
pp. 8865-8883 ◽  
Author(s):  
S. Sharmila ◽  
K. J. E. Walsh
Keyword(s):  
Tropical Cyclone ◽  
Large Scale ◽  
Formation Rate ◽  
Tropical Cyclone Genesis ◽  
Climate Conditions ◽  
The North ◽  
Spatial Changes ◽  
Mean Climate ◽  
Cyclone Genesis ◽  
Made In

Significant advances have been made in understanding the key climate factors responsible for tropical cyclone (TC) activity, yet any theory that estimates likelihood of observed TC formation rates from mean climate states remains elusive. The present study investigates how the extremes of observed TC genesis (TCG) frequency during peak TC seasons are interrelated with distinct changes in the large-scale climate conditions over different ocean basins using the global International Best Track Archive for Climate Stewardship (IBTrACS) dataset and ERA-Interim for the period 1979–2014. Peak TC seasons with significantly high and low TCG frequency are identified for five major ocean basins, and their substantial spatial changes in TCG are noted with regionally distinct differences. To explore the possible climate link behind such changes, a suite of potentially relevant dynamic and thermodynamic climate conditions is analyzed. Results indicate that the observed changes in extreme TCG frequency are closely linked with distinct dominance of specific dynamic and thermodynamic climate conditions over different regions. While the combined influences of dynamic and thermodynamic climate conditions are found to be necessary for modulating TC formation rate over the North Atlantic, eastern Pacific, and southern Indian Oceans, significant changes in large-scale dynamic conditions appear to solely control the TCG frequency over the western Pacific and South Pacific basins. Estimation of the fractional changes in genesis-weighted climate conditions also indicates the coherent but distinct competing effects of different climate conditions on TCG frequency. The present study further points out the need for revising the existing genesis indices for estimating TCG frequency over individual basins.

scholarly journals Testing the Performance of Tropical Cyclone Genesis Indices in Future Climates Using the HiRAM Model

2014 ◽  
Vol 27 (24) ◽  
pp. 9171-9196 ◽  
Author(s):  
Suzana J. Camargo ◽  
Michael K. Tippett ◽  
Adam H. Sobel ◽  
Gabriel A. Vecchi ◽  
Ming Zhao
Keyword(s):  
Tropical Cyclone ◽  
Large Scale ◽  
Atmospheric Model ◽  
The Other ◽  
Tropical Cyclone Genesis ◽  
Good Prediction ◽  
Present Climate ◽  
Environmental Predictors ◽  
Saturation Deficit ◽  
Cyclone Genesis

Abstract Tropical cyclone genesis indices (TCGIs) are functions of the large-scale environment that are designed to be proxies for the probability of tropical cyclone (TC) genesis. While the performance of TCGIs in the current climate can be assessed by direct comparison to TC observations, their ability to represent future TC activity based on projections of the large-scale environment cannot. Here the authors examine the performance of TCGIs in high-resolution atmospheric model simulations forced with sea surface temperatures (SST) of future, warmer climate scenarios. They investigate whether the TCGIs derived for the present climate can, when computed from large-scale fields taken from future climate simulations, capture the simulated global mean decreases in TC frequency. The TCGIs differ in their choice of environmental predictors, and several choices of predictors perform well in the present climate. However, some TCGIs that perform well in the present climate do not accurately reproduce the simulated future decrease in TC frequency. This decrease is captured when the humidity predictor is the column saturation deficit rather than relative humidity. Using saturation deficit with relative SST as the other thermodynamic predictor overpredicts the TC frequency decrease, while using potential intensity in place of relative SST as the other thermodynamic predictor gives a good prediction of the decrease’s magnitude. These positive results appear to depend on the spatial and seasonal patterns in the imposed SST changes; none of the indices capture correctly the frequency decrease in simulations with spatially uniform climate forcings, whether a globally uniform increase in SST of 2 K, or a doubling of CO2 with no change in SST.

scholarly journals Tropical cyclone genesis potential across palaeoclimates

2015 ◽  
Vol 11 (10) ◽  
pp. 1433-1451 ◽  
Author(s):  
J. H. Koh ◽  
C. M. Brierley
Keyword(s):  
Carbon Dioxide ◽  
Tropical Cyclone ◽  
Last Glacial Maximum ◽  
Large Scale ◽  
Climate Models ◽  
Glacial Maximum ◽  
Tropical Cyclone Genesis ◽  
Last Glacial ◽  
Potential Index ◽  
Cyclone Genesis

Abstract. The favourability of the mid-Pliocene, Last Glacial Maximum (LGM) and mid-Holocene for tropical cyclone formation is investigated in five climate models. This is measured by a genesis potential index, derived from large-scale atmospheric properties known to be related to storm formation. The mid-Pliocene and Last Glacial Maximum (LGM) were periods where carbon dioxide levels were higher and lower than preindustrial levels respectively, while the mid-Holocene differed primarily in its orbital configuration. The cumulative global genesis potential is found to be fairly invariant across the palaeoclimates in the multi-model mean. Despite this all ensemble members agree on coherent responses in the spatial patterns of genesis potential change. During the mid-Pliocene and LGM, changes in carbon dioxide led to sea surface temperature changes throughout the tropics, yet the potential intensity (a measure associated with maximum tropical cyclone strength) is calculated to be relatively insensitive to these changes. Changes in tropical cyclone genesis potential during the mid-Holocene are found to be asymmetric about the Equator: being reduced in the Northern Hemisphere but enhanced in the Southern Hemisphere. This is clearly driven by the altered seasonal insolation. Nonetheless, the enhanced seasonality drove localised changes in genesis potential, by altering the strength of monsoons and shifting the intertropical convergence zone. Trends in future tropical cyclone genesis potential are consistent neither between the five models studied nor with the palaeoclimate results. It is not clear why this should be the case.

scholarly journals Possible Cause of Seasonal Inhomogeneity in Interdecadal Changes of Tropical Cyclone Genesis Frequency over the Western North Pacific

2021 ◽  
Vol 34 (2) ◽  
pp. 635-642
Author(s):  
Minhee Chang ◽  
Doo-Sun R. Park ◽  
Chang-Hoi Ho
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
Large Scale ◽  
Tropical Cyclone Genesis ◽  
Easterly Wind ◽  
Sst Warming ◽  
Cyclone Genesis ◽  
Interdecadal Changes ◽  
Genesis Frequency

AbstractAn abrupt decrease in annual tropical cyclone genesis frequency (TCGF), which is statistically significant only from October to December (OND), has been noticed over the western North Pacific Ocean. However, the seasonal inhomogeneity of interdecadal changes in TCGF between OND and the other seasons (from January to September) and the associated mechanisms are not clearly documented. This study examines and compares the different interdecadal changes in OND and in January–September from 1979 to 2018. According to our analysis, the TCGF decrease in OND (2.2) accounts for 79% of the total decrease (2.8) in annual TCGF after 1998, whereas the TCGF in January to September remains unchanged. The key differences in large-scale environment are found from the extension of equatorial easterly wind anomalies and attendant anticyclone anomalies in the subtropics. Under similar sea surface temperature (SST) warming pattern in the tropical Indo-Pacific region (i.e., the La Niña–like SST warming), tropical precipitation is significantly enhanced over the area where its seasonal peak occurs: the tropical Indian Ocean in OND and the tropical western Pacific in January–September. Thus, the equatorial easterly wind anomalies extend westward to 110°E in OND and to 145°E in January–September. Different extension of easterly wind anomalies results in different expansion of attendant large-scale anticyclone anomaly over the subtropical western Pacific, which dominates the entire main development region in OND but not in January–September. To summarize, the different extensions of easterly wind anomalies under similar La Niña–like SST warming are responsible for the seasonal inhomogeneity of interdecadal changes in TCGF.

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