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Creators/Authors contains: "Rocque, Marquette N."

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  1. Abstract

    Global satellite studies show a maximum in deep convection and lightning downstream of the Andes in subtropical South America. The Remote sensing of Electrification, Lightning, And Mesoscale/microscale Processes with Adaptive Ground Observations (RELAMPAGO) field campaign was designed to investigate the physical processes that contribute to the rapid development of deep convection and mesoscale convective systems (MCSs) in Argentina. A lightning mapping array (LMA) was deployed to Argentina as part of RELAMPAGO to collect lightning observations from extreme storms in the region. This study combines lightning data from the LMA and the Geostationary Lightning Mapper onboardGOES‐16with 1‐km gridded radar data to examine the electrical characteristics of a variety of convective storms throughout their life cycle observed during RELAMPAGO. Results from the full campaign show 48% of flashes are associated with deep convection that occurs along the eastern edge of the Sierras de Córdoba (SDC) overnight. These flashes are 65 km2smaller on average compared to stratiform flashes, which occur most frequently 50–100 km east of the SDC in the early morning hours, consistent with the upscale growth of MCSs off the terrain. Analysis of the 13–14 December MCS shows that sharp increases in flash rates correspond to deep and wide convective cores that have high graupel and hail mass, 35‐dBZ volume, and ice water path. This work validates previous satellite studies of lightning in the region, but also provides higher spatial and temporal resolution information across the convective life cycle that has not been available in previous studies.

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  2. Abstract Intense deep convection and large mesoscale convective systems (MCSs) are known to occur downstream of the Andes in subtropical South America. Deep convection is often focused along the Sierras de Córdoba (SDC) in the afternoon and then rapidly grows upscale and moves to the east overnight. However, how the Andes and SDC impact the life cycle of MCSs under varying synoptic conditions is not well understood. Two sets of terrain-modification experiments using WRF are used to investigate the impact of topography in different synoptic regimes. The first set is run on the 13–14 December 2018 MCS case from RELAMPAGO, which featured a deep synoptic trough, strong lee cyclogenesis near the SDC, an enhanced low-level jet, and rapid upscale growth of an MCS. When the Andes are reduced by 50%, the lee cyclone and low-level jet that develop are weaker than with the full Andes, and the resulting MCS is weak and moves faster to the east. When the SDC are removed, few differences between the environment and resulting MCS relative to the control run are seen. A second set of experiments are run on the 25–26 January 2019 case in which a large MCS developed over the SDC and remained tied there for an extended period under weak synoptic forcing. The experiment that produces the most similar MCS to the control is when the Andes are reduced by 50% while maintaining the height of the SDC, suggesting the SDC may play a more important role in the MCS life cycle under quiescent synoptic conditions. 
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  3. Abstract This study uses shipborne [R/V Roger Revelle and R/V Mirai ] radar, upper-air, ocean, and surface meteorology datasets from the DYNAMO field campaign to investigate the diurnal cycle (DC) of precipitation over the central Indian Ocean related to two distinct Madden-Julian oscillations (MJOs) observed. This study extends earlier studies on the MJO DC by examining the relationship between the DC of convective organization and the local environment and comparing these results on- and off-equator. During the suppressed phase on-equator, the DC of rain rates exhibited two weak maxima at 15 LT and 01 LT, which was largely controlled by the presence of sub-MCS nonlinear precipitation features (PFs). During the active phase on-equator, MCS nonlinear features dominated the rain volume, and the greatest increase in rain rates occurred between 21-01 LT. This maximum coincided with the maxima in convective available potential energy (CAPE) and sensible heat flux, and the column moistened significantly over night. Off-equator, the environment was much drier and there was little large-scale upward motion as a result of limited deep convection. The DC of rain rates during the active phase off-equator was most similar to the DC observed during the suppressed phase on-equator, while rainfall off-equator during the suppressed phase did not vary much throughout the day. The DC of MCS nonlinear PFs closely resembled the DC of rainfall during both phases off-equator, and the DC of environmental parameters, including sea surface temperature, CAPE, and latent heat flux, was typically much weaker off-equator compared to on-equator. 
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