Probing the Tropopause Region of Mesoscale Weather Systems Using a Microwave Temperature Profiler

Temperature data in the upper-troposphere and lower stratosphere, retrieved from a microwave temperature profiler (MTP) deployed on the National Science Foundation – National Center for Atmospheric Research Gulfstream V (G-V) aircraft during two recent field experiments, are analyzed. Data from the Pre-depression Investigation of Cloud Systems in the Tropics (PREDICT) will be emphasized, but preliminary analyses from the Mesoscale Predictability Experiment (MPEX) will also be presented. In the tropical maritime regions, space and time temperature variations within mesoscale systems are seldom greater than 1-2 K. It is therefore not obvious that meaningful spatial and temporal temperature variations can be recovered from the MTP in these regions, partly because of limitations of the statistical retrieval method that relies on widely-space radiosonde data for a priori information. This presentation will show that useful information can indeed be obtained. MTP data during PREDICT reveal that the lowest cold-point temperature was reached at the time of genesis of hurricane Karl (2010), and the observed cold-point variations appear consistent with the expected influence of a Kelvin wave in the upper troposphere and lower stratosphere. In a pre-genesis composite of four cases, a warm anomaly of nearly 1 K appears in the upper troposphere (10-14 km) within 200 km of the nascent center of circulation in the lower troposphere. The upper-tropospheric radial variations of temperature are consistent with dropsonde observations. Furthermore, the MTP data reveal systematic diurnal temperature changes associated with deep convective clouds, with warming in the upper troposphere near 10-12 km, cooling near 15 km and warming in the lower stratosphere near the peak convective activity near and following sunrise. Data from MPEX will contrast these subtle variations in the tropics with mid-latitude temperature anomalies that reveal more baroclinic precursors of mesoscale convective systems.