TY - JOUR
T1 - On the Formation of an Elevated Nocturnal Inversion Layer in the Presence of a Low-Level Jet
T2 - A Case Study
AU - Kutsher, Jakob
AU - Haikin, Nitsa
AU - Sharon, Avi
AU - Heifetz, Eyal
N1 - Funding Information:
Acknowledgments The authors would like to thank Mr. Rony Neuman (NRCN) and Prof. Uri Dayan (HUJI) for useful discussions; NCEP Reanalysis data provided by the NOAA/OAR/ESRL PSD, Boulder, CO, USA, from their Web site at http://www.esrl.noaa.gov/psd/. The authors are also in debt to the anonymous reviewers for their valuable comments. E.H is grateful to the United States–Israel Binational Science Foundation (BSF) grant # 2008436.
PY - 2012/9
Y1 - 2012/9
N2 - We report on observed nocturnal profiles, in which an inversion layer is located at the core of a low-level jet, bounded between two well-mixed layers. High-resolution vertical profiles were collected during a field campaign in a small plain in the Israeli desert (Negev), distant 100 km from the eastern shore of the Mediterranean Sea. During the evening hours, the synoptic flow, superposed on the late sea breeze, forms a low-level jet characterized by a maximum wind speed of 12 ms -1 at an altitude of 150 m above the ground. The strong wind shear at the jet maximum generates downward heat fluxes that act against the nocturnal ground cooling. As a result, the typical ground-based nocturnal inversion is "elevated" towards the jet centre, hence a typical early morning thermal profile is observed a few hours after sunset. Since the jet is advected into the region, its formation does not depend on the presence of a surface nocturnal inversion layer to decouple the jet from surface friction. On the contrary, here the advected low-level jet acts to hinder the formation of such an inversion. These unusual temperature and wind profiles are expected to affect near-ground dispersion processes.
AB - We report on observed nocturnal profiles, in which an inversion layer is located at the core of a low-level jet, bounded between two well-mixed layers. High-resolution vertical profiles were collected during a field campaign in a small plain in the Israeli desert (Negev), distant 100 km from the eastern shore of the Mediterranean Sea. During the evening hours, the synoptic flow, superposed on the late sea breeze, forms a low-level jet characterized by a maximum wind speed of 12 ms -1 at an altitude of 150 m above the ground. The strong wind shear at the jet maximum generates downward heat fluxes that act against the nocturnal ground cooling. As a result, the typical ground-based nocturnal inversion is "elevated" towards the jet centre, hence a typical early morning thermal profile is observed a few hours after sunset. Since the jet is advected into the region, its formation does not depend on the presence of a surface nocturnal inversion layer to decouple the jet from surface friction. On the contrary, here the advected low-level jet acts to hinder the formation of such an inversion. These unusual temperature and wind profiles are expected to affect near-ground dispersion processes.
KW - Low-level jet
KW - Nocturnal inversion
KW - Stable boundary layer
KW - Turbulent mixing
UR - http://www.scopus.com/inward/record.url?scp=84865421702&partnerID=8YFLogxK
U2 - 10.1007/s10546-012-9720-y
DO - 10.1007/s10546-012-9720-y
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AN - SCOPUS:84865421702
SN - 0006-8314
VL - 144
SP - 441
EP - 449
JO - Boundary-Layer Meteorology
JF - Boundary-Layer Meteorology
IS - 3
ER -