Differentiating Tropical Cyclones Exhibiting Strong Updrafts using Combined Satellite, Lightning, and Global Hawk Observations

This study was motivated by concern that the high-altitude NASA Global Hawk (GH) pilotless aircraft might encounter significant turbulence in the course of over-flights of tropical cyclones (TCs) during the HS3 field campaign in the Atlantic. For this reason, strict over-flight rules were put in place to avoid such hazards. However, these rules also meant that many good HS3 science missions would be constrained, especially when investigating the TC core region.

Utilizing a combination of advanced satellite-based image analysis tools and lightning data from the Global Lightning Network as proxy information for locally strong updrafts, we are able to identify likely regions/periods of intense convection in TCs that could lead to turbulence. The key satellite products include Tropical Overshooting Tops (TOTs) and Cloud-Top Heights (CTH), although it is found that using either product alone is insufficient. Remote sensing instruments on the GH (and its predecessor the ER-2) were used to examine past cases that involved TC over-flights. The CTH product in turn also benefits from the GH cloud height observations for calibration/validation purposes.

The primary outcome of this study was an altering of the GH over-flight rules to be more flexible based on analyzed conditions. Our findings in this brief investigation also indicate the potential of the products to contribute towards more extensive studies of TC cloud-top analyses.