Variability of Surface Air Temperature over Gently Sloped Terrain

Abstract Temperature and wind data from a rural micronet and nearby site of the Oklahoma Mesonet are analyzed to study the frequency, strength, and formation processes of cold-pool events in a region with gentle terrain. Spatial analyses were performed for a 2-yr-long temperature record from 26 temperature/humidity surface stations, deployed across a 120 m × 320 m micronet located in a region of gently sloped terrain with maximum elevation changes of ∼25 m. Cold pools frequently formed at the base of a gentle slope in a small depression of only ∼6-m depth that is also sheltered by trees. The strength of each cold-pool event was classified according to a cold-pool index based on average nocturnal temperature perturbations within the cold-pool region. Wind data collected with sonic anemometers on a 15-m-tall tower at the micronet for a period of three months (spring 2005) suggest that flow sheltering by vegetation plays an important role in the cold-pool formation. The wind data also show signatures of kata...

[1]  L. Mahrt,et al.  Nocturnal surface temperature distribution as remotely sensed from low-flying aircraft , 1983 .

[2]  T. W. Horst,et al.  Heat Balance in the Nocturnal Boundary Layer during CASES-99 , 2003 .

[3]  L. Mahrt.  Variation of Surface Air Temperature in Complex Terrain , 2006 .

[4]  R. Tabony,et al.  Relations between minimum temperature and topography in great britain , 1985 .

[5]  R. Grossman,et al.  Horizontal Variability of 2-m Temperature at Night during CASES-97 , 2003 .

[6]  E. Fedorovich,et al.  Coriolis effects in homogeneous and inhomogeneous katabatic flows , 2008 .

[7]  D. Lenschow,et al.  Shallow Drainage Flows , 2001 .

[8]  J. Horel,et al.  Cold Air Pool Structure and Evolution in a Mountain Basin: Peter Sinks, Utah , 2003 .

[9]  Sutherland,et al.  Statewide Monitoring of the Mesoscale Environment: A Technical Update on the Oklahoma Mesonet , 2007 .

[10]  D. Fitzjarrald,et al.  The Early Evening Surface-Layer Transition: Temporal and Spatial Variability , 2001 .

[11]  J. C. Kaimal,et al.  Atmospheric boundary layer flows , 1994 .

[12]  Kristina Blennow,et al.  Modelling minimum air temperature in partially and clear felled forests , 1998 .

[13]  T. Haiden,et al.  Minimum Temperatures, Diurnal Temperature Ranges, and Temperature Inversions in Limestone Sinkholes of Different Sizes and Shapes , 2004 .

[14]  Jeffrey B. Basara,et al.  Significant Inversions and Rapid In Situ Cooling at a Well-Sited Oklahoma Mesonet Station , 2007 .

[15]  R. Stull,et al.  Meteorology for Scientists and Engineers , 1999 .

[16]  L. Mahrt,et al.  The Nocturnal Surface Inversion and Influence of Clear-Air Radiative Cooling , 1982 .

[17]  E. Fedorovich,et al.  Katabatic flow along a differentially cooled sloping surface , 2005, Journal of Fluid Mechanics.

[18]  Minimum temperature surveys based on near‐surface air temperature measurements and airborne thermal scanner data , 1986 .

[19]  C. Jackson,et al.  The Climate near the Ground , 1966 .

[20]  I. Karlsson.  Nocturnal Air Temperature Variations between Forest and Open Areas. , 2000 .

[21]  C. Whiteman.  Observations of Thermally Developed Wind Systems in Mountainous Terrain , 1990 .

[22]  L. Mahrt,et al.  Observations Of Nocturnal Drainage Flow In A Shallow Gully , 2002 .

[23]  Christopher A. Fiebrich,et al.  The Impact of Unique Meteorological Phenomena Detected by the Oklahoma Mesonet and ARS Micronet on Automated Quality Control , 2001 .

[24]  B. W. Thompson.  SMALL‐SCALE KATABATICS AND COLD HOLLOWS , 1986 .

[25]  Torbjörn Gustavsson,et al.  Development of Temperature Patterns during Clear Nights , 1998 .