Intertropical Convergence Zone as the Possible Source Mechanism for Southward Propagating Medium-Scale Traveling Ionospheric Disturbances over South American Low-Latitude and Equatorial Region

Abstract

This paper presents the Intertropical Convergence Zone (ITCZ) as the possible source mechanism of the medium-scale traveling ionospheric disturbances (MSTIDs) propagating to the southeast direction over the South American region. Using the data collected by the GNSS dual-frequency receivers network from January 2014 to December 2019, detrended TEC maps were generated to identify and characterize 144 MSTIDs propagating southeastward over the South American low-latitude and equatorial region. We also used images from the Geostationary Operational Environmental Satellite (GOES) 13 and 16 in the infrared (IR) and water vapor (WV) channel, and reanalisys data from the National Centers for Environmental Prediction (NCEP) of the National Oceanic and Atmospheric Administration (NOAA) to study the daily features and seasonal migration of ITCZ. In the winter, when ITCZ migrates to the northern hemisphere around 10–15° N, 20 MSTIDs propagated southeastward. During summer, when the ITCZ lies within the continent, around 0–5° S 80 MSTIDs were observed to propagate southeastward; in the equinoxes (spring and fall), 44 MSTIDs were observed. Again, the MSTIDs propagating southeastward showed a clear seasonality of their local time dependence; in summer, the MSTIDs occurred frequently in the evening hours, whereas those in winter occurred during the daytime. We also found for the first time that the day-to-day observation of ITCZ position and MSTIDs propagation directions were consistent. With regard to these new findings, we report that the MSTIDs propagating southeastward over the South American region are possibly induced by the atmospheric gravity waves, which are proposed as being generated by the ITCZ in the troposphere. The mean distribution of the horizontal wavelength, period, and phase velocity are 698 ± 124 km, 38 ± 8 min, and 299 ± 89 m s−1, respectively. For the first time, we were able to use MSTID propagation directions as a proxy to study the source region.

Land cover classification of Andean sub-basins in Colombia based on Sentinel-2 satellite images and deep learning

“…The study area is located within the intertropical convergence zone, which is an area near the equator where trade winds from the northern and southern hemispheres converge. This convergence often results in the formation of cumulus clouds, which can lead to high levels of cloud cover in the region 32 . Therefore, obtaining clear images of the area of interest is challenging due to the frequent presence of clouds.…”

Multiclass Land Use and Land Cover Classification of Andean Sub-Basins in Colombia with Sentinel-2 and Deep Learning

“…The study area is located within the intertropical convergence zone, which is an area near the equator where trade winds from the northern and southern hemispheres converge. This convergence often results in the formation of cumulus clouds, which can lead to high levels of cloud cover in the region [30]. Therefore, obtaining clear images of the area of interest is challenging due to the frequent presence of clouds.…”

Daytime Medium Scale Traveling Ionospheric Disturbances (MSTIDS) Over the Andes Mountains at Equatorial and Low Magnetic Latitudes

“…Theoretically, this phenomenon was first investigated in the 1960s by the pioneering work of Hines (1960), although the first observation of the wavelike disturbances was in the 1940s (Munro, 1948). In the last 10 years, dozens of theoretical and observational studies in different geographic regions have been carried out using diverse instruments, such as ionosondes (e.g., Amorim et al., 2011; Sherstyukov et al., 2018), satellites (e.g., Bolmgren et al., 2020), incoherent scatter radars (e.g., Negale et al., 2018; Nicolls et al., 2010, 2014; Vadas & Nicolls, 2009), and all‐sky airglow imagers (e.g., Figueiredo et al., 2018b; Martinis et al., 2019; Paulino et al., 2016; Smith et al., 2013; Terra et al., 2020), total electron content (e.g., Azeem et al., 2015, 2017; Chen et al., 2019; Essien et al., 2021, 2022; Figueiredo et al., 2018a; Sivakandan et al., 2021), and Doppler radar sounder (Crowley & Rodrigues, 2012; Vadas & Crowley, 2010).…”