[GTP] Seminar at NCAR--Impacts of Stable Boundary Layer on Tropical Cyclone Structure in Coupled WRF Model

[Silvia Gentile]

Impacts of Stable Boundary Layer on Tropical Cyclone Structure in 
Coupled WRF Model
Chiaying Lee and Shuyi S. Chen
Rosenstiel School of Marine and Atmospheric Science (RSMAS)
University of Miami, Florida

Air-sea interaction in tropical cyclones (TCs) and storm-induced cold 
wake have been studied using idealized models and limited observations 
for decades. However, how exactly the air-sea coupling and the cold wake 
affect the TC structure and intensity remains unresolved. Recent 
observations from the Impact of Typhoon on Ocean in Pacific (ITOP) have 
shown that storm-induced ocean cooling can lead to development of 
persistent stable boundary layer in TCs. High-resolution coupled model 
indicates that the stable boundary layer can have a significant impact 
on the near surface inflow and convection in the eyewall. To fully 
understand the physical processes of stable boundary layer over the cold 
wake in TCs and its impact on storm structure, a comprehensive tracer 
and trajectory analysis is conducted using the coupled WRF-3DPWP (CWRF) 
model simulation of Typhoon Choiwan (2009). Experiments of uncoupled WRF 
and CWRF are compared to quantify the thermodynamic property of the 
inflow air over the storm-induced cold wake/stable boundary layer. It is 
found the near surface inflow air in the stable boundary layer in CWRF 
tends to penetrate further inward into the TC inner core and eyewall 
with higher theta-e value due to enhanced surface heat flux, whereas the 
air in unstable and/or neutral boundary layer in the uncoupled model 
goes into rainbands and lessen the amount into the TC inner core. In 
addition to the thermodynamic impact, the cold wake-induced near surface 
pressure gradient can enhance the inflow angle and strength. These 
results suggest that the cold wake and stable boundary layer have a 
directly impact on TC structure and intensity.

Thursday, 28 July 2011, 3:30 PM
Refreshments 3:15 PM
NCAR-Foothills Laboratory
3450 Mitchell Lane
Bldg 2, Large Seminar Room 1022

MMM SEMINAR COORDINATOR: Jielun Sun, 303-497-8994
jsun at ucar.edu http://www.mmm.ucar.edu/sem/seminars.html

-- 
Silvia Gentile
NCAR IMAGe
1850 Table Mesa Drive
Boulder, CO 803035
www2.image.ucar.edu/IMAGe