- Please check and comment entries here.
Variability of Vertical Wind Shear
Vertical wind shear is caused by a wind of different speed or direction over a relatively short distance in the atmosphere.
This entry explores the relationship between vertical wind shear (VWS) and tropical cyclone (TC) genesis in the Mozambique Channel (MC) for the period 1979–2019. Additionally, SST, low-level relative vorticity, 700 hPa relative humidity and upper-level divergence were also analyzed for the peak cyclogenesis months to explore their relative contributions. The analyses were done using NCEP/NCAR Reanalysis-1 for the atmospheric fields, monthly Optimum Interpolation SST V2, and for the cyclogenesis the TC best track data from the La Reunion–Regional Specialized Meteorological and Joint Typhoon Warning Centre. A total of 43 TCs generated in the MC were observed for the analysed period. The maximum frequency of cyclogenesis in the MC was observed during January and February and the spatial location of maximum TC genesis was coincident with the minimum values of the VWS. The VWS showed significant correlations with TC intensity, particularly when considering the upper atmosphere (200–500 hPa) or the bulk (200–850 hPa) VWS. The mean composites of the cyclogenesis months over the MC of SST, relative humidity at 700 hPa, divergence at upper atmosphere, showed significant values. However, linear correlations between these factors vs. TC genesis frequency and intensity were not significant. Analyses of interannual correlations between VWS and Niño-3.4 (subtropical southwest Indian Ocean dipole-SIOD) showed statistically significant positive (negative) correlations at different lags, suggesting that La Niña and the positive phase of SIOD conditions are favorable to weaker VWS and thus to intensification of TCs in the Mozambique Channel. Thirteen landfall cases were observed with seven over the Madagascar west coast and six over the Mozambique coast. The landfall over the Madagascar (Mozambique) coast was associated with strengthened (weakened) VWS.
2. Tropical Cyclones
The entry is from 10.3390/atmos12060739
- Gray, W.M. Global view of the origin of tropical disturbances and storms. Mon. Weather Rev. 1968, 96, 669–700.
- Chan, K.T.F.; Wang, D.; Zhang, Y.; Wanawong, W.; He, M.; Yu, X. Does strong vertical wind shear certainly lead to the weakening of a tropical cyclone? Environ. Res. Commun. 2019, 1, 1–13.
- Emanuel, K.; DesAutels, C.; Holloway, C.; Korty, R. Environmental control of tropical cyclone intensity. J. Atmos. Sci. 2004, 61, 843–856.
- Finocchio, P.M.; Majumdar, S.J. A Statistical Perspective on Wind Profiles and Vertical Wind Shear in Tropical Cyclone Environments of the Northern Hemisphere. Mon. Weather Rev. 2017, 145, 361–378.
- Aiyyer, A.R.; Thorncroft, C. Climatology of Vertical Wind Shear over the Tropical Atlantic. J. Clim. 2006, 19, 2969–2983.
- Nolan, D.S.; McGauley, M.G. Tropical cyclogenesis in wind shear: Climatological relationships and physical processes. In Cyclones: Formation, Triggers and Control; Nova Science Publishers, Inc.: New York, NY, USA, 2012; pp. 1–36.
- Jones, J.J.; Bell, M.M.; Klotzbach, P.J. Tropical and Subtropical North Atlantic Vertical Wind Shear and Seasonal Tropical Cyclone Activity. J. Clim. 2020, 33, 5413–5426.
- Molinari, J.; Vollaro, D. Rapid Intensification of a Sheared Tropical Storm. Mon. Weather Rev. 2010, 138, 3869–3885.
- Montgomery, M.T.; Lussier, L.L., III; Moore, R.W.; Wang, Z. The genesis of Typhoon Nuri as observed during the Tropical Cyclone Structure 2008 (TCS-08) field experiment—Part 1: The role of the easterly wave critical layer. Atmos. Chem. Phys. 2010, 10, 9879–9900.
- Rios-Berrios, R.; Torn, R.D.; Davis, C.A. An Ensemble Approach to Investigate Tropical Cyclone Intensification in Sheared Environments. Part II: Ophelia (2011). J. Atmos. Sci. 2016, 73, 1555–1575.
- Mundell, D.B. Prediction of Tropical Cyclone Rapid Intensification Events. Master’s Thesis, Colorado State University, Fort Collins, CO, USA, 1990.
- DeMaria, M. The effect of vertical shear on tropical cyclone intensity change. J. Atmos. Sci. 1996, 53, 2076–2087.
- Zehr, R.M. Environmental vertical wind shear with Hurricane Bertha (1996). Weather Forecast. 2003, 18, 345–356.
- Bracken, W.E.; Bosart, L.F. The role of Synoptic-Scale flow during tropical cyclogenesis over the North Atlantic Ocean. Mon. Weather Rev. 2000, 128, 353–376.
- Zehr, R.M. Tropical Cyclogenesis in the Western North Pacific; NOAA Technical Report NESDIS 61; NOAA: St. Petersburg, FL, USA, 1992; p. 181.
- Fink, H.A.; Speth, P. Tropical cyclones. Naturwissenschaften 1998, 85, 482–493.
- Ho, C.-H.; Kim, J.-H.; Jeong, J.-H.; Kim, H.-S.; Chen, D. Variation of tropical cyclone activity in the South Indian Ocean: El Niño–Southern Oscillation and Madden-Julian Oscillation effects. J. Geophys. Res. 2006, 111, 1–9.
- Mavume, A.F.; Rydberg, L.; Rouault, M.; Lutjeharms, J.R.E. Climatology and landfall of tropical cyclones in the SouthWest Indian Ocean. J. Mar. Sci. 2009, 8, 15–36.
- Malherbe, J.; Engelbrecht, F.A.; Landman, W.A.; Engelbrecht, C.J. Tropical systems from the southwest Indian Ocean making landfall over the Limpopo River Basin, southern Africa: A historical perspective. Int. J. Climatol. 2012, 32, 1018–1032.
- WMO. Global Guide to Tropical Cyclone Forecasting; Guard, C., Ed.; WMO: Geneva, Switzerland, 2017; p. 399. Available online: (accessed on 7 January 2020).
- Leroux, M.-D.; Meister, J.; Mekies, D.; Dorla, A.-L. A Climatology of Southwest Indian Ocean Tropical Systems: Their Number, Tracks, Impacts, Sizes, Empirical Maximum Potential Intensity, and Intensity Changes. J. Appl. Meteorol. Climatol. 2018, 57, 1021–1041.
- Bousquet, O.; Barruol, G.; Cordier, E.; Barthe, C.; Bielli, S.; Calmer, R.; Rindraharisaona, E.; Roberts, G.; Tulet, P.; Amelie, V.; et al. Impact of Tropical Cyclones on Inhabited Areas of the SWIO Basin at Present and Future Horizons. Part 1: Overview and Observing Component of the Research Project RENOVRISK-CYCLONE. Atmosphere 2021, 12, 544.
- Chen, S.S.; Knaff, J.A.; Marks, F.D., Jr. Effects of Vertical Wind Shear and Storm Motion on Tropical Cyclone Rainfall Asymmetries Deduced from TRMM. Mon. Weather Rev. 2006, 134, 3190–3208.
- Bessafi, M.; Wheeler, M.C. Modulation of South Indian Ocean Tropical Cyclones by the Madden–Julian Oscillation and Convectively Coupled Equatorial Waves. Mon. Weather Rev. 2006, 134, 638–656.
- Kuleshov, Y.; Ming, F.C.; Qi, L.; Chouaibou, I.; Hoareau, C.; Roux, F. Tropical cyclone genesis in the Southern Hemisphere and its relationship with the ENSO. Ann. Geophys. 2009, 27, 2523–2538.
- Jury, M.R.; Pathack, B. A study of climate and weather variability over the tropical Southwest Indian Ocean. Meteorol. Atmos. Phys. 1991, 47, 37–48.
- Jury, M.R. A preliminary study of climatological associations and characteristics of tropical cyclones in the SW Indian Ocean. Meteor. Atmos. Phys. 1993, 51, 101–115.
- Matyas, C.J. Tropical cyclone formation and motion in the Mozambique Channel. Int. J. Climatol. 2015, 35, 375–390.
- Barimalala, R.; Blamey, R.C.; Desbiolles, F.; Reason, C.J.C. Variability in the Mozambique Channel Trough and Impacts on Southeast African Rainfall. J. Clim. 2020, 33, 749–765.
- Cook, H.H. The South Indian Convergence Zone and Interannual Rainfall Variability over Southern Africa. J. Clim. 2000, 13, 3789–3804.
- Barimalala, R.; Desbiolles, F.; Blamey, R.C.; Reason, C. Madagascar Influence on the South Indian Ocean Convergence Zone, the Mozambique Channel Trough and Southern African Rainfall. Geophys. Res. Lett. 2018, 45, 11380–11389.