On the generation and propagation of Makran swells in the Arabian Sea

Abstract

Persistent and periodic northerly low-level jets have been identified in the South Asian mid?latitudes and subtropics, which are modified by the presence of Makran mountain ranges adjacent to the central south coast of Pakistan, where they blow predominantly in the west-northwest to northeast directions. These winds lead to the generation of a new wave system and propagate through the Arabian Sea as "makran swells". They are prevalent during October to May. The measurements along the west coast of India reveal systematic variations in the wave spectra relating the makran events. This has been further verified through the WaveWatch III simulations forced by the CFSR winds. The significant wave heights up to 4.5 m were hindcasted in the northern Arabian Sea during these events. Once generated, the makran swells propagate to the eastern Arabian Sea and western Arabian Sea with directional sectors of 300-360° and 0-60°, respectively. The characteristic features and the spatial extension of the makran swells are particularly analysed.