Open AccessConcurrent OH imager and sodium temperature/wind lidar observation of localized ripples over northern Colorado
Author(s) -
Li Tao,
She C. Y.,
Williams Bifford P.,
Yuan Tao,
Collins Richard L.,
Kieffaber Lois M.,
Peterson Alan W.
Publication year - 2005
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2004jd004885
Subject(s) - lidar , instability , wind shear , gravity wave , geology , atmospheric sciences , wavelength , perturbation (astronomy) , wind speed , atmosphere (unit) , physics , meteorology , gravitational wave , astrophysics , remote sensing , mechanics , optics , astronomy
On 3 and 5 September 2002 the OH all‐sky imager at Platteville, Colorado (40.2°N, 104.7°W), observed small‐scale, wavelike patterns (known as ripples), with horizontal wavelengths of ∼9 km and ∼7 km and lifetimes of ∼9 min and ∼15 min, respectively. The Colorado State University sodium lidar at nearby Fort Collins, Colorado (40.6°N, 105°W), also made concurrent observations of temperature and zonal and meridional winds, which allowed us to determine the nature of the ripples observed. Our observations suggest that the 3 September ripple was induced by a convective instability located at 87.5 km and the 5 September ripple was induced by a dynamic instability at 88.5 km. The ripples clearly advected as packets with the background wind. Lidar measurements also allowed us to relate the directions of wind shear to the phase front alignments of both the ripples and the nearby short‐period atmospheric gravity waves. These spatial relationships provided a meaningful comparison with previously observed ripples as well as with current theoretical models. Using the 16‐hour continuous lidar data set for each case, we deduced that long‐period waves created an unusually large temperature perturbation at the ripple times on 3 September and an unusually large wind shear perturbation on 5 September. These perturbations prepared the background atmosphere to be near the verge of local instability, but, as revealed again by lidar observation, it was the superposition of smaller‐scale perturbations at the time of the ripples that helped to actually reach the conditions required for instability and generation of the ripples.