Dynamical propagation and growth mechanisms for convectively coupled equatorial Kelvin waves over the Indian Ocean

Abstract

Convectively coupled equatorial Kelvin waves (CCKWs) are high-impact tropical weather systems that can lead to severe flooding over the Maritime Continent. Here, a vorticity budget for CCKWs over the Indian Ocean is constructed using reanalysis data, to identify the basic mechanisms of eastward propagation and growth. The budget is reasonably well closed, with a small residual/subgrid-scale term. In the lower troposphere, CCKWs behave like strongly modified theoretical equatorial Kelvin waves. Vortex stretching, from the divergence of the Kelvin wave acting on planetary vorticity (the −fD term), is the sole mechanism by which the vorticity structure of a theoretical Kelvin wave propagates eastward. In the lower and middle troposphere, this term is also the key mechanism for the eastward propagation of CCKWs but, due to subtleties in its structure and phasing linked to a combination of modal structures, it also contributes to growth. Unlike in the theoretical Kelvin wave, other vorticity source terms also play a role in the propagation and growth of CCKWs. In particular, vortex stretching from relative vorticity (the −𝜁D term) is the largest source term, and this leads strongly to growth, through interactions between the background and perturbation vorticity and divergence. Horizontal vorticity advection by the background flow contributes to propagation, and also acts to retard the growth of the CCKW. The sum of the source terms in this complex vorticity budget leads to eastward propagation and growth of CCKWs. The structure and vorticity budget of CCKWs in the upper troposphere is quite unlike that of a Kelvin wave, and appears to arise as a forced response to the lower-tropospheric structure. The implications for numerical weather prediction and climate simulations are discussed.

The TRAPPIST-1 Habitable Atmosphere Intercomparison (THAI). II. Moist Cases—The Two Waterworlds

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The role of tropical waves in the genesis of Tropical Cyclone Seroja in the Maritime Continent

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“…This deflection was crucial for structuring the convection over Timor by positioning the CCKW westerly wind anomaly in the Java sea. Recently, Matthews 51 showed that the meridional gradient of the zonal wind anomaly results in significant relative vorticity south of a CCKW axis. This study shows that over the Indian Ocean, a major contribution to the vorticity tendency comes from CCKW divergence acting on background environmental vorticity.…”

Search for close encounters of stars with the Solar System using Gaia DR3 catalog

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“…The early history of searches for close encounters of stars with the Solar System using various catalogs is reflected in the works of Revina (1988), Matthews (1994), Mülläri, Orlov (1996), Garcia-Sánchez et al (1999;2001), Bobylev (2010a;2010b) , Anderson, Francis (2012), Dybczyński, Berski (2015), Bailer-Jones (2015), Feng, Bailer-Jones (2015). In particular, it was found that one of the record holders, a candidate for penetration into the Oort Cloud, is the star GJ 710 (Garcia-Sanchez et al, 2001;Bobylev, 2010a;Berski and Dybczyński, 2016).…”