Hurricane Boundary Layer Height Relative to Storm Motion from GPS Dropsonde Composites

Abstract

This study investigates the asymmetric distribution of hurricane boundary layer height scales in a storm-motion-relative framework using global positioning system (GPS) dropsonde observations. Data from a total of 1916 dropsondes collected within four times the radius of maximum wind speed of 37 named hurricanes over the Atlantic basin from 1998 to 2015 are analyzed in the composite framework. Motion-relative quadrant mean composite analyses show that both the kinematic and thermodynamic boundary layer height scales tend to increase with increasing radius in all four motion-relative quadrants. It is also found that the thermodynamic mixed layer depth and height of maximum tangential wind speed are within the inflow layer in all motion-relative quadrants. The inflow layer depth and height of the maximum tangential wind are both found to be deeper in the two front quadrants, and they are largest in the right-front quadrant. The difference in the thermodynamic mixed layer depth between the front and back quadrants is smaller than that in the kinematic boundary layer height. The thermodynamic mixed layer is shallowest in the right-rear quadrant, which may be due to the cold wake phenomena. The boundary layer height derived using the critical Richardson number ( R i c ) method shows a similar front-back asymmetry as the kinematic boundary layer height.

Transition of the Hurricane Boundary Layer during the Landfall of Hurricane Irene (2011)

“…1) was dropped just beyond the continental shelf, but is retained as it was very near the gradient in bathymetry. Hence, we take the dropsonde profiles as representative of shoaling wave conditions (Powell et al 2003), where drag coefficients are increased relative to deep water (e.g., beyond the continental shelf). Each profile shows normalized wind speed maxima well above the surface.…”

“…However, the adjustment of the HBL to the inland surface roughness regime implies that the HBL wind profile through the coastal transition may deviate from a logarithmic profile (or log-linear profile). Over the ocean on average, dropsonde profiles suggest that the HBL is indeed log linear (e.g., Franklin et al 2003;Powell et al 2003;Giammanco et al 2013). This notion is examined via the dual-Doppler coastal-composite analyses by computing the aerodynamic surface roughness needed to maintain a log-linear profile between 200 m (the lowest available dual-Doppler wind measurement) and the height of the maximum wind (calculated for each profile as a function of distance from the coast).…”

“…Observations of the mean HBL structure over the open ocean are generally plentiful (Zhang et al 2011;Ren et al 2019). dropsonde (Hock and Franklin 1999) observations have been collected by several airborne platforms including the National Oceanic and Atmospheric Administration's (NOAA's) WP-3D Orion and G-IV jet (Aberson et al 2006) operated by the NOAA Aircraft Operations Center, the C-130 Hurricane Hunter aircraft operated by the U.S. Air Force (USAF; e.g., Franklin et al 2003), the HIAPER aircraft operated by National Science Foundation (NSF; UCAR/NCAR 2005), and the DC-8 and Global Hawk operated by the National Aeronautics and Space Administration (NASA;Naftel 2009).…”

Wind profile analysis for selected tropical cyclones over the South China Sea based on dropsonde measurements

“…Since the 1990s, the deployments of global positioning system (GPS)-based dropsondes by the United States National Oceanic and Atmospheric Administration (NOAA) hurricane research aircraft have provided a wealth of information of TCs in the North Atlantic Ocean. With the aid of high-resolution profile observations, a number of aspects of TCs have been investigated, including air-sea interaction (Powell et al, 2003;D'Asaro et al, 2014), boundary layer height scales (Zhang et al, 2011;Ren et al, 2019), outflow characteristics (Komaromi and Doyle, 2017), inflow angles (Zhang and Uhlhorn, 2012), etc. In particular, composite mean wind profiles measured in the vicinity of TC eyewalls suggest that wind speed increases logarithmically with height in the lowest 200 m, peaks at 500 m, and decreases aloft (Powell et al, 2003;Knupp et al, 2006;Kepert, 2006aKepert, , 2006b.…”

Lower Atmosphere Meteorology

“…Turbulence mixing in the atmosphere near the surface is determined by the height of the atmospheric boundary layer and data remains scarce in hurricane conditions. Under such extreme conditions, Ren et al [2] investigated the asymmetric distribution of atmospheric boundary layer height scales using dropsondes.…”