High frequency ground temperature fluctuation in a Convective Boundary Layer

A. Garai, J. Kleissl, M. Lothon, F. Lohou, E. Pardyjak, F. Saïd, J. Cuxart, G.J. Steeneveld, C. Yaguë, S. Derrien, D. Alexander, D.M. Villagrasa

Research output: Chapter in Book/Report/Conference proceedingConference paperAcademic

Abstract

To study influence of the turbulent structures in the convective boundary layer (CBL) on the ground temperature, during the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST) observational campaign, high frequency ground temperature was recorded through infra-red imagery from 13 June - 8 July, 2011. The 2-D ground temperature characteristics were then studied and compared to surface layer turbulence data for clear days. The ground temperature standard deviation follows the power-law exponent similar to surface layer similarity theory. The high correlation region between the air and the ground temperatures is aligned with the wind direction; the spanwise spread of the correlation region depends on the wind direction variability. The upwind part of the high correlation region is comparable with the flux footprint function by Hsieh et al. (2000). Conditional averaging shows that when a cold air parcel descends through the atmospheric surface layer (ASL) during a sweep event, the ground cools down. As the air parcel remains near the ground, it warms up and the heat transport from the ground to the air decreases. Thus the ground warms up during this period. After attaining a certain buoyancy the warm air parcel ascends, creating an ejection event. During the initial period of ejection, the ground temperature peaks, and subsequently the ground starts to cool down as the ground heat flux starts to decrease. Animation of ground temperature fluctuations reveals that the imprints of these ejection and sweep events move along with the wind. The estimated speed of these coherent structures is of the same order as the wind speed at 8 m above ground level or higher. With increasing stability of the CBL, the mean size of these structures increases and they become streakier.
Original languageEnglish
Title of host publication20th Symposium on Boundary Layers and Turbulence/18th Conference on Air-Sea Interaction, American Meteorological Society (9-13 July 2012, Boston, MA)
Place of PublicationBoston
PublisherAmerican Meteorological Society
Pages14B.3
Publication statusPublished - 2012
Event20th Symposium on Boundary Layers and Turbulence/18th Conference on Air-Sea Interaction - Boston, United States
Duration: 9 Jul 201213 Jul 2012

Conference

Conference20th Symposium on Boundary Layers and Turbulence/18th Conference on Air-Sea Interaction
CountryUnited States
CityBoston
Period9/07/1213/07/12

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convective boundary layer
temperature
surface layer
air
wind direction
turbulence
infrared imagery
cold air
footprint
buoyancy
heat flux
power law
boundary layer
wind velocity

Cite this

Garai, A., Kleissl, J., Lothon, M., Lohou, F., Pardyjak, E., Saïd, F., ... Villagrasa, D. M. (2012). High frequency ground temperature fluctuation in a Convective Boundary Layer. In 20th Symposium on Boundary Layers and Turbulence/18th Conference on Air-Sea Interaction, American Meteorological Society (9-13 July 2012, Boston, MA) (pp. 14B.3). Boston: American Meteorological Society.
Garai, A. ; Kleissl, J. ; Lothon, M. ; Lohou, F. ; Pardyjak, E. ; Saïd, F. ; Cuxart, J. ; Steeneveld, G.J. ; Yaguë, C. ; Derrien, S. ; Alexander, D. ; Villagrasa, D.M. / High frequency ground temperature fluctuation in a Convective Boundary Layer. 20th Symposium on Boundary Layers and Turbulence/18th Conference on Air-Sea Interaction, American Meteorological Society (9-13 July 2012, Boston, MA). Boston : American Meteorological Society, 2012. pp. 14B.3
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title = "High frequency ground temperature fluctuation in a Convective Boundary Layer",
abstract = "To study influence of the turbulent structures in the convective boundary layer (CBL) on the ground temperature, during the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST) observational campaign, high frequency ground temperature was recorded through infra-red imagery from 13 June - 8 July, 2011. The 2-D ground temperature characteristics were then studied and compared to surface layer turbulence data for clear days. The ground temperature standard deviation follows the power-law exponent similar to surface layer similarity theory. The high correlation region between the air and the ground temperatures is aligned with the wind direction; the spanwise spread of the correlation region depends on the wind direction variability. The upwind part of the high correlation region is comparable with the flux footprint function by Hsieh et al. (2000). Conditional averaging shows that when a cold air parcel descends through the atmospheric surface layer (ASL) during a sweep event, the ground cools down. As the air parcel remains near the ground, it warms up and the heat transport from the ground to the air decreases. Thus the ground warms up during this period. After attaining a certain buoyancy the warm air parcel ascends, creating an ejection event. During the initial period of ejection, the ground temperature peaks, and subsequently the ground starts to cool down as the ground heat flux starts to decrease. Animation of ground temperature fluctuations reveals that the imprints of these ejection and sweep events move along with the wind. The estimated speed of these coherent structures is of the same order as the wind speed at 8 m above ground level or higher. With increasing stability of the CBL, the mean size of these structures increases and they become streakier.",
author = "A. Garai and J. Kleissl and M. Lothon and F. Lohou and E. Pardyjak and F. Sa{\"i}d and J. Cuxart and G.J. Steeneveld and C. Yagu{\"e} and S. Derrien and D. Alexander and D.M. Villagrasa",
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Garai, A, Kleissl, J, Lothon, M, Lohou, F, Pardyjak, E, Saïd, F, Cuxart, J, Steeneveld, GJ, Yaguë, C, Derrien, S, Alexander, D & Villagrasa, DM 2012, High frequency ground temperature fluctuation in a Convective Boundary Layer. in 20th Symposium on Boundary Layers and Turbulence/18th Conference on Air-Sea Interaction, American Meteorological Society (9-13 July 2012, Boston, MA). American Meteorological Society, Boston, pp. 14B.3, 20th Symposium on Boundary Layers and Turbulence/18th Conference on Air-Sea Interaction, Boston, United States, 9/07/12.

High frequency ground temperature fluctuation in a Convective Boundary Layer. / Garai, A.; Kleissl, J.; Lothon, M.; Lohou, F.; Pardyjak, E.; Saïd, F.; Cuxart, J.; Steeneveld, G.J.; Yaguë, C.; Derrien, S.; Alexander, D.; Villagrasa, D.M.

20th Symposium on Boundary Layers and Turbulence/18th Conference on Air-Sea Interaction, American Meteorological Society (9-13 July 2012, Boston, MA). Boston : American Meteorological Society, 2012. p. 14B.3.

Research output: Chapter in Book/Report/Conference proceedingConference paperAcademic

TY - GEN

T1 - High frequency ground temperature fluctuation in a Convective Boundary Layer

AU - Garai, A.

AU - Kleissl, J.

AU - Lothon, M.

AU - Lohou, F.

AU - Pardyjak, E.

AU - Saïd, F.

AU - Cuxart, J.

AU - Steeneveld, G.J.

AU - Yaguë, C.

AU - Derrien, S.

AU - Alexander, D.

AU - Villagrasa, D.M.

N1 - recorded presentation: https://ams.confex.com/ams/20BLT18AirSea/flvgateway.cgi/id/21856?recordingid=21856

PY - 2012

Y1 - 2012

N2 - To study influence of the turbulent structures in the convective boundary layer (CBL) on the ground temperature, during the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST) observational campaign, high frequency ground temperature was recorded through infra-red imagery from 13 June - 8 July, 2011. The 2-D ground temperature characteristics were then studied and compared to surface layer turbulence data for clear days. The ground temperature standard deviation follows the power-law exponent similar to surface layer similarity theory. The high correlation region between the air and the ground temperatures is aligned with the wind direction; the spanwise spread of the correlation region depends on the wind direction variability. The upwind part of the high correlation region is comparable with the flux footprint function by Hsieh et al. (2000). Conditional averaging shows that when a cold air parcel descends through the atmospheric surface layer (ASL) during a sweep event, the ground cools down. As the air parcel remains near the ground, it warms up and the heat transport from the ground to the air decreases. Thus the ground warms up during this period. After attaining a certain buoyancy the warm air parcel ascends, creating an ejection event. During the initial period of ejection, the ground temperature peaks, and subsequently the ground starts to cool down as the ground heat flux starts to decrease. Animation of ground temperature fluctuations reveals that the imprints of these ejection and sweep events move along with the wind. The estimated speed of these coherent structures is of the same order as the wind speed at 8 m above ground level or higher. With increasing stability of the CBL, the mean size of these structures increases and they become streakier.

AB - To study influence of the turbulent structures in the convective boundary layer (CBL) on the ground temperature, during the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST) observational campaign, high frequency ground temperature was recorded through infra-red imagery from 13 June - 8 July, 2011. The 2-D ground temperature characteristics were then studied and compared to surface layer turbulence data for clear days. The ground temperature standard deviation follows the power-law exponent similar to surface layer similarity theory. The high correlation region between the air and the ground temperatures is aligned with the wind direction; the spanwise spread of the correlation region depends on the wind direction variability. The upwind part of the high correlation region is comparable with the flux footprint function by Hsieh et al. (2000). Conditional averaging shows that when a cold air parcel descends through the atmospheric surface layer (ASL) during a sweep event, the ground cools down. As the air parcel remains near the ground, it warms up and the heat transport from the ground to the air decreases. Thus the ground warms up during this period. After attaining a certain buoyancy the warm air parcel ascends, creating an ejection event. During the initial period of ejection, the ground temperature peaks, and subsequently the ground starts to cool down as the ground heat flux starts to decrease. Animation of ground temperature fluctuations reveals that the imprints of these ejection and sweep events move along with the wind. The estimated speed of these coherent structures is of the same order as the wind speed at 8 m above ground level or higher. With increasing stability of the CBL, the mean size of these structures increases and they become streakier.

M3 - Conference paper

SP - 14B.3

BT - 20th Symposium on Boundary Layers and Turbulence/18th Conference on Air-Sea Interaction, American Meteorological Society (9-13 July 2012, Boston, MA)

PB - American Meteorological Society

CY - Boston

ER -

Garai A, Kleissl J, Lothon M, Lohou F, Pardyjak E, Saïd F et al. High frequency ground temperature fluctuation in a Convective Boundary Layer. In 20th Symposium on Boundary Layers and Turbulence/18th Conference on Air-Sea Interaction, American Meteorological Society (9-13 July 2012, Boston, MA). Boston: American Meteorological Society. 2012. p. 14B.3