Anomalous COAMPS-TC Boundary Layer Thermodynamic Structures Revealed through Novel Aircraft Observations

To accurately forecast tropical cyclone (TC) track, intensity, and structure using numerical weather prediction techniques, properly representing TC inner-core thermodynamic processes is essential. To validate these processes, COAMPS-TC simulations from multiple Atlantic TCs are compared with aircraft observations, with an emphasis placed on studying boundary layer thermodynamics. Temperature and water vapor measurements from dropsondes, a well-established yet spatially-limited measurement technique, and the Compact Raman Lidar (CRL), a novel remote sensing system, are used for these comparisons. The CRL records curtains of temperature and moisture below the NOAA P-3 aircraft flight height, with measurements reaching from flight level to the sea surface or low level cloud top at all flight times.

Statistical composites and case study methods focused on individual center passes are utilized to address this research question. First, certain COAMPS-TC deterministic forecasts, like for TC Sam (2021), produced horizontal temperature gradients that were too weak compared with observations, helping to explain the slower than observed intensification rates for these cases. Moisture is also overestimated in COAMPS-TC boundary layers across most cases. This combination of thermodynamic anomalies has significant implications for COAMPS-TC boundary layer scheme adjustments. Other features, like atmospheric stability and the TC mixed layer height, are compared between models and observations. Overall, this work highlights the necessity of applying both case study and statistical approaches in observation-model intercomparisons in the effort to improve physical parameterizations.