We describe and show results from a series of field campaigns that used balloonborne instruments launched from India and Saudi Arabia during the summers 2014–17 to study the nature, formation, and impacts of the Asian Tropopause Aerosol Layer (ATAL). The campaign goals were to i) characterize the optical, physical, and chemical properties of the ATAL; ii) assess its impacts on water vapor and ozone; and iii) understand the role of convection in its formation. To address these objectives, we launched 68 balloons from four locations, one in Saudi Arabia and three in India, with payload weights ranging from 1.5 to 50 kg. We measured meteorological parameters; ozone; water vapor; and aerosol backscatter, concentration, volatility, and composition in the upper troposphere and lower stratosphere (UTLS) region. We found peaks in aerosol concentrations of up to 25 cm–3 for radii > 94 nm, associated with a scattering ratio at 940 nm of ∼1.9 near the cold-point tropopause. During medium-duration balloon flights near the tropopause, we collected aerosols and found, after offline ion chromatography analysis, the dominant presence of nitrate ions with a concentration of about 100 ng m–3. Deep convection was found to influence aerosol loadings 1 km above the cold-point tropopause. The Balloon Measurements of the Asian Tropopause Aerosol Layer (BATAL) project will continue for the next 3–4 years, and the results gathered will be used to formulate a future National Aeronautics and Space Administration–Indian Space Research Organisation (NASA–ISRO) airborne campaign with NASA high-altitude aircraft.

This study investigates the impacts of solar activity on the performance of the latest release of International Reference Ionosphere (IRI) model version 2012 (IRI-2012)

No abstract

In the present study, the occurrence and characteristics of equatorial plasma bubble (EPB) has been analyzed using the GPS data from continuously operating reference stations network over Hong Kong during 2001–2012. The analysis found maximum EPB occurrences during the equinoctial months and minimum EPB occurrences during the December solstice throughout 2001–2012 except during the solar minimum in 2007–2009. The maximum EPB occurrences were observed in June solstice during 2007–2008, whereas for 2009, EPB occurrences were quite higher for June solstice but slightly smaller than the March equinox. The seasonal maximum in EPB occurrences have been discussed in terms of plasma density seed perturbation caused by gravity waves as well as the post sunset F‐layer rise due to the pre‐reversal enhancement of zonal electric field. Generally, EPB occurrences are found to be more prominent during nighttime hours (19:00–24:00 h) than daytime hours. The day and nighttime EPB occurrences were inferred and found to vary linearly with solar activity and have an annual correlation coefficient (R) of ~ 0.92 with F10.7 cm solar flux and ~0.88 with sunspot number. Moreover, the impact of solar activity on EPB occurrences is found to be dependent on seasons with maximum during the equinox (R = 0.80) and minimum during the summer season (R = 0.68). The detail study of EPB occurrences during two typical cases of geomagnetic storms on 6 November and 24 November 2001 found that the storm on 24 November triggered the EPB occurrence whereas storm on 6 November suppressed the EPB occurrence. The enhancement/suppression of EPB occurrences during storms periods is a consequence of a storm‐induced prompt penetration electric field as well as disturbance dynamo electric field effects associated with the main phase of the geomagnetic storm.