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

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

doi:10.1002/qj.3441

Cited by 25 publications

(39 citation statements)

References 56 publications

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“…A4 and A5). An increase in cloud coverage as a consequence of an increase in the sensible heat flux was found in previous studies (Khanna et al, 2017;Bosman et al, 2019). It is therefore In the mid-and high-latitudes, changes in LST often exhibit a similar spatial pattern to surface air temperature changes, which are discussed in more detail in the next section (compare Fig.…”

Section: Lst Responsesupporting

confidence: 68%

Impacts of a Revised Surface Roughness Parameterization in the Community Land Model 5.1

Meier

Davin

Bonan

et al. 2021

Preprint

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Abstract. The roughness of the land surface (z0) is a key property for the amount of turbulent activity above the land surface and through that for the turbulent exchange of energy, water, momentum, and chemical species between the land and the atmosphere. Variations in z0 are substantial across different types of land cover from typically less than 1 mm over fresh snow or sand deserts up to more than 1 m over urban areas or forests. In this study, we revise the parameterizations and parameter choices related to z0 in the Community Land Model 5.1 (CLM), the land component of the Community Earth System Model 2.1.2 (CESM). We propose a number modifications for z0 in CLM, which are guided by observational data. Most importantly, we increase the z0 for all types of forests, while we decrease the momentum z0 for bare soil, snow, glaciers, and crops. We then assess the effect of those modifications in land-only (CLM) and land-atmosphere coupled (CESM) simulations. Diurnal variations of the land surface temperature (LST) are dampened in regions with forests, while they are amplified over warm deserts. These changes mitigate model biases compared to MODIS remote sensing observations, which have been identified in several earlier studies. The alterations in LST are mostly stronger during the day than at night. For example, the LST at 13:30 increases by more than 4.80 K during boreal summer across the entire Sahara. The induced changes in the diurnal variability of air temperatures at the bottom of the atmosphere generally oppose changes in LST in sign and are of smaller magnitude. Further, winds close to the land surface accelerate in areas where the momentum z0 was lowered, such as the Sahara desert, the Middle East, or the Antarctica, and decelerate in regions with forests. Overall, this study highlights that the current representation of z0 in CLM is not in agreement with observational constraints for several types of land cover. The resultant model modifications are shown to considerably alter the simulated climate in terms of temperatures and wind speed at the land surface.

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Section: Lst Responsesupporting

confidence: 68%

Impacts of a Revised Surface Roughness Parameterization in the Community Land Model 5.1

Meier

Davin

Bonan

et al. 2021

Preprint

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“…This difference is largest for low wind speeds, with cc − cc up to 20% over the centre of London. Satellite observations during low wind speed conditions also show enhanced cloud cover over the forested area southwest of London, consistent with forested areas in France (Teuling et al, 2017;Bosman et al, 2019). However, the UKV forecasts do not reproduce this enhancement.…”

Section: Cloudsmentioning

confidence: 78%

Understanding London's summertime cloud cover

Theeuwes

Boutle

Clark

et al. 2021

Quart J Royal Meteoro Soc

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Cities are a source of complex land-atmosphere interactions. Spatial differences in the energy balance and enhanced surface roughness interact with the atmosphere to alter clouds and precipitation. Here, we explore how London (UK) alters cloud formation during the spring and summer. The Met Office's high-resolution operational forecasts predict enhanced cloud cover over the city, as found in observations, but underpredicts the intensity. During low wind speeds, cloud enhancement over the city is strongest and linked to an urban-induced thermal circulation. These circulations advect moist air from the city edge inwards, transporting it upwards with a large moisture convergence over the urban area. At around 1,000 m above the surface, the turbulent moisture flux takes over the moisture transport to the cloud layer. A relative humidity budget shows the moisture flux in the upper boundary layer to be the largest contribution to the urban-rural differences in relative humidity.

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“…For instance, some areas (e.g. much of Mid-Europe; figures 2(c) and (f)) experience significant changes in energy partitioning, with an increase in latent heat fluxes and decreases in sensible heat fluxes, but an increase in cloud cover ( figure 3(a)), which may contradict recent case studies with a convection-resolving model (Bosman et al 2019) and points to the importance of finer-resolution future simulations to resolve potential issues associated with convection parameterizations (Prein et al 2016.…”

Section: Resultsmentioning

confidence: 85%

Land use change impacts on European heat and drought: remote land-atmosphere feedbacks mitigated locally by shallow groundwater

Zipper

Keune

Kollet³

2019

Environ. Res. Lett.

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Heat and drought are projected to increase globally but may be mitigated or exacerbated by land use/land cover (LULC) change. Here, we show that remote land-atmosphere feedbacks caused by historical European LULC change led to widespread changes in the energy and water balances, drought, and heat. Using a continental-scale bedrock-to-atmosphere model, we find that LULC change following the Soviet Union collapse and European Union formation may have substantially increased cloud cover and decreased incoming shortwave radiation in western Europe, even in locations where LULC did not change. These changes to the water and energy balances had spatially heterogeneous impacts on drought and heat, including drying in the Mediterranean and Eastern Europe regions. The response of the water and energy balances to remote feedbacks was lessened in areas with shallow groundwater, indicating that local-and continental-scale responses to LULC change are influenced by the coupling between the subsurface, land surface, and atmosphere.

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

Cited by 25 publications

References 56 publications

Impacts of a Revised Surface Roughness Parameterization in the Community Land Model 5.1

Impacts of a Revised Surface Roughness Parameterization in the Community Land Model 5.1

Understanding London's summertime cloud cover

Land use change impacts on European heat and drought: remote land-atmosphere feedbacks mitigated locally by shallow groundwater

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