Abstract

To study the seeding mechanism of ionospheric irregularity occurrences, a correlation study has been carried out between the global monthly/latitudinal (m/l) distributions of irregularity occurrences and the deep atmospheric convective clouds in the intertropical convergence zone (ITCZ) indicated by the outgoing longwave radiation (OLR) measurements. Seven longitude sectors - the African, Indian, West Pacific, Central Pacific, East Pacific, South American, and Atlantic sectors - are selected to study the correlations between the two distributions. The results indicate that good correlations exist only in the South American sector and to some extent in the African sector. For the other five sectors, no correlations are found in the m/l distributions between the irregularities and OLRs. This implies that the gravity wave induced in the ITCZ cannot be the sole seeding agent for the Rayleigh-Taylor (RT) instability in the global irregularity occurrences every season. We suspect that the post-sunset ionospheric electrodynamic perturbations could be the prevailing seeds for the RT instability globally year long. Together with the favorable post-sunset ionospheric condition, the global m/l distributions of irregularity occurrences could be adequately explained.

Highlights

  • To study the seeding mechanism of ionospheric irregularity occurrences, a correlation study has been carried out between the global monthly/latitudinal (m/l) distributions of irregularity occurrences and the deep atmospheric convective clouds in the intertropical convergence zone (ITCZ) indicated by the outgoing longwave radiation (OLR) measurements

  • Discussions and conclusions Correlation studies carried out between the m/l distributions of density irregularities and the m/l distributions of OLR observations in the ITCZ as the proxy of gravity wave occurrences at seven longitude sectors indicate that good correlations between the irregularities and OLRs only exist in the South American sector and to some extent in the African sector

  • The irregularity occurrences are either much higher than the OLR occurrences in some months as in the Atlantic sector or, the other way around, much lower than the OLR occurrences as in the Indian, West Pacific, and Central Pacific sectors

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Summary

Introduction

To study the seeding mechanism of ionospheric irregularity occurrences, a correlation study has been carried out between the global monthly/latitudinal (m/l) distributions of irregularity occurrences and the deep atmospheric convective clouds in the intertropical convergence zone (ITCZ) indicated by the outgoing longwave radiation (OLR) measurements. Correlation between the irregularity occurrences and the ITCZ cloud distributions was first suggested in the report of McClure et al (1998) and extensively studied by Tsunoda (2010a, c) who demonstrated that the atmospheric gravity waves generated in the ITCZ can serve as seeds of the RT instabilities during solstices at some longitude sectors.

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