Sensible heating as a potential mechanism for enhanced cloud formation over temperate forest

Peter J.M. Bosman*, Chiel C. van Heerwaarden, Adriaan J. Teuling

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

2 Citations (Scopus)

Abstract

It has been recently shown for two forests in France (Les Landes and Sologne) that summer cloud cover over the forest is increased relative to its surroundings. This study aims to contribute to the elucidation of the physical mechanisms responsible for this increased cloud cover, focusing on surface flux partitioning. This was done by performing a case study for a heatwave day on which enhanced cloud cover over the forest of Les Landes was observed. Two numerical experiments (large-eddy simulations) with a homogeneous forest cover were performed, one in which the sensible heat flux was increased by approximately 5% of the total available energy and another one in which the same amount of energy was added to the latent heat flux. The addition of energy to the sensible heat flux led to a stronger increase in cloud cover than the same addition to the latent heat flux. The mean relative humidity at the boundary layer top showed only small differences, indicating it was not a sufficient indicator for cloud formation in this case. Important information, which immediately underlines the need for large-eddy simulations, is contained in modifications of the shape of the probability density functions of temperature and humidity. With enhanced sensible heating, the higher peak values of relative humidity contribute to an increased cloud cover. A crucial reason for the differences in cloud cover between the experiments is conjectured to be a decrease in the required amount of energy for air parcels to reach the lifting condensation level, indirectly caused by the boundary layer and near-surface warming associated with the stronger sensible heat flux. As forests in the region do have a higher sensible heat flux than their surroundings, we highlight one potential mechanism for enhanced cloud cover.

Original languageEnglish
Pages (from-to)450-468
JournalQuarterly Journal of the Royal Meteorological Society
Volume145
Issue number719
DOIs
Publication statusPublished - 1 Jan 2019

Fingerprint

temperate forest
cloud cover
heating
sensible heat flux
large eddy simulation
latent heat flux
energy
relative humidity
boundary layer
surface flux
probability density function
forest cover
condensation
humidity
partitioning
warming
experiment
air
summer
temperature

Keywords

  • cloud formation
  • flux partitioning
  • forest cloud cover
  • large-eddy simulation
  • sensible heat flux
  • sensible heating
  • surface heat fluxes

Cite this

@article{18923c735f9c48c7bb238cf4b51edd2a,
title = "Sensible heating as a potential mechanism for enhanced cloud formation over temperate forest",
abstract = "It has been recently shown for two forests in France (Les Landes and Sologne) that summer cloud cover over the forest is increased relative to its surroundings. This study aims to contribute to the elucidation of the physical mechanisms responsible for this increased cloud cover, focusing on surface flux partitioning. This was done by performing a case study for a heatwave day on which enhanced cloud cover over the forest of Les Landes was observed. Two numerical experiments (large-eddy simulations) with a homogeneous forest cover were performed, one in which the sensible heat flux was increased by approximately 5{\%} of the total available energy and another one in which the same amount of energy was added to the latent heat flux. The addition of energy to the sensible heat flux led to a stronger increase in cloud cover than the same addition to the latent heat flux. The mean relative humidity at the boundary layer top showed only small differences, indicating it was not a sufficient indicator for cloud formation in this case. Important information, which immediately underlines the need for large-eddy simulations, is contained in modifications of the shape of the probability density functions of temperature and humidity. With enhanced sensible heating, the higher peak values of relative humidity contribute to an increased cloud cover. A crucial reason for the differences in cloud cover between the experiments is conjectured to be a decrease in the required amount of energy for air parcels to reach the lifting condensation level, indirectly caused by the boundary layer and near-surface warming associated with the stronger sensible heat flux. As forests in the region do have a higher sensible heat flux than their surroundings, we highlight one potential mechanism for enhanced cloud cover.",
keywords = "cloud formation, flux partitioning, forest cloud cover, large-eddy simulation, sensible heat flux, sensible heating, surface heat fluxes",
author = "Bosman, {Peter J.M.} and {van Heerwaarden}, {Chiel C.} and Teuling, {Adriaan J.}",
year = "2019",
month = "1",
day = "1",
doi = "10.1002/qj.3441",
language = "English",
volume = "145",
pages = "450--468",
journal = "Quarterly Journal of the Royal Meteorological Society",
issn = "0035-9009",
publisher = "Wiley",
number = "719",

}

Sensible heating as a potential mechanism for enhanced cloud formation over temperate forest. / Bosman, Peter J.M.; van Heerwaarden, Chiel C.; Teuling, Adriaan J.

In: Quarterly Journal of the Royal Meteorological Society, Vol. 145, No. 719, 01.01.2019, p. 450-468.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

T1 - Sensible heating as a potential mechanism for enhanced cloud formation over temperate forest

AU - Bosman, Peter J.M.

AU - van Heerwaarden, Chiel C.

AU - Teuling, Adriaan J.

PY - 2019/1/1

Y1 - 2019/1/1

N2 - It has been recently shown for two forests in France (Les Landes and Sologne) that summer cloud cover over the forest is increased relative to its surroundings. This study aims to contribute to the elucidation of the physical mechanisms responsible for this increased cloud cover, focusing on surface flux partitioning. This was done by performing a case study for a heatwave day on which enhanced cloud cover over the forest of Les Landes was observed. Two numerical experiments (large-eddy simulations) with a homogeneous forest cover were performed, one in which the sensible heat flux was increased by approximately 5% of the total available energy and another one in which the same amount of energy was added to the latent heat flux. The addition of energy to the sensible heat flux led to a stronger increase in cloud cover than the same addition to the latent heat flux. The mean relative humidity at the boundary layer top showed only small differences, indicating it was not a sufficient indicator for cloud formation in this case. Important information, which immediately underlines the need for large-eddy simulations, is contained in modifications of the shape of the probability density functions of temperature and humidity. With enhanced sensible heating, the higher peak values of relative humidity contribute to an increased cloud cover. A crucial reason for the differences in cloud cover between the experiments is conjectured to be a decrease in the required amount of energy for air parcels to reach the lifting condensation level, indirectly caused by the boundary layer and near-surface warming associated with the stronger sensible heat flux. As forests in the region do have a higher sensible heat flux than their surroundings, we highlight one potential mechanism for enhanced cloud cover.

AB - It has been recently shown for two forests in France (Les Landes and Sologne) that summer cloud cover over the forest is increased relative to its surroundings. This study aims to contribute to the elucidation of the physical mechanisms responsible for this increased cloud cover, focusing on surface flux partitioning. This was done by performing a case study for a heatwave day on which enhanced cloud cover over the forest of Les Landes was observed. Two numerical experiments (large-eddy simulations) with a homogeneous forest cover were performed, one in which the sensible heat flux was increased by approximately 5% of the total available energy and another one in which the same amount of energy was added to the latent heat flux. The addition of energy to the sensible heat flux led to a stronger increase in cloud cover than the same addition to the latent heat flux. The mean relative humidity at the boundary layer top showed only small differences, indicating it was not a sufficient indicator for cloud formation in this case. Important information, which immediately underlines the need for large-eddy simulations, is contained in modifications of the shape of the probability density functions of temperature and humidity. With enhanced sensible heating, the higher peak values of relative humidity contribute to an increased cloud cover. A crucial reason for the differences in cloud cover between the experiments is conjectured to be a decrease in the required amount of energy for air parcels to reach the lifting condensation level, indirectly caused by the boundary layer and near-surface warming associated with the stronger sensible heat flux. As forests in the region do have a higher sensible heat flux than their surroundings, we highlight one potential mechanism for enhanced cloud cover.

KW - cloud formation

KW - flux partitioning

KW - forest cloud cover

KW - large-eddy simulation

KW - sensible heat flux

KW - sensible heating

KW - surface heat fluxes

U2 - 10.1002/qj.3441

DO - 10.1002/qj.3441

M3 - Article

VL - 145

SP - 450

EP - 468

JO - Quarterly Journal of the Royal Meteorological Society

JF - Quarterly Journal of the Royal Meteorological Society

SN - 0035-9009

IS - 719

ER -