4C.3
Thermal structure of Hurricane Erin's (2001) Core Using Dropsonde Data from 68,000 Feet and Comparison with AMSU Satellite Measurements
Jeffrey B. Halverson, Univ. of Maryland Baltimore County, Baltimore, MD; and T. Hock, H. Cole, J. Simpson, G. M. Heymsfield, H. Pierce, C. Velden, and K. F. Brueske
During CAMEX-4 the first high altitude (20 km) dropsonde data were collected within the eye and inner core region of Hurricane Erin, a mature Category 3 hurricane over the western Atlantic. Twenty dropsondes from the NASA DC-8 and ER-2 were deployed within five degrees of the center location, including eight high altitude drops made from the ER-2 . The ER-2 drosponde system was designed by NCAR ATD as a fully autonomous system, capable of launching up to four dropsondes simultaneously. These measurements permit an unprecedented in situ mapping of Erin’s three dimensional thermal structure from above tropopause height down to sea surface. Positive (warm) temperature anomalies (i.e. eye center minus coolest available environmental value) exist at every level from sea surface through 75 mb, with the maximum perturbation of +11.5 C located at 500 mb and values as large as +9 C extending up to 200 mb. The horizontal thermal gradient is largest at 700 mb and the radial envelope of warming broadens considerably above this level. Above 400 mb, the three dimensional temperature structure reveals an asymmetry, whereby the warmest values are displaced to the south of the eye’s (surface) center position. What appears to be unusual about the warm core in this storm is not its maximum value, which is modest, but its vertical extent. Calculations based on hydrostatic theory are next shown which relate the magnitude of the observed eye warming to the surface pressure reduction. The observed warming profile is also compared with a retrieved thermodynamic profile obtained from NOAA AMSU, which overflew the eye within two hours of the center dropsonde release. Taken together, these detailed datasets provide a comprehensive snapshot of the inner core of a symmetric, strong category Atlantic hurricane and offer clues into the energetics involved in maintaining its warm anomaly.
Session 4C, HL2001/CAMEX-4
Tuesday, 30 April 2002, 8:30 AM-10:30 AM
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