Parameterization of the Planetary Boundary Layer in Large-Scale Atmospheric Models

1988 ◽  
pp. 331-374 ◽  
Author(s):  
G. Sommeria
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Large Scale ◽  
Atmospheric Models

Rising Planetary Boundary Layer Height over the Sahara Desert and Arabian Peninsula in a Warming Climate

2021 ◽  
Vol 34 (10) ◽  
pp. 4043-4068
Author(s):  
Liming Zhou ◽  
Yuhong Tian ◽  
Nan Wei ◽  
Shu-peng Ho ◽  
Jing Li
Keyword(s):  
Boundary Layer ◽  
Relative Humidity ◽  
Planetary Boundary Layer ◽  
Large Scale ◽  
Arabian Peninsula ◽  
Climate Model ◽  
Statistical Significance ◽  
Maximum Height ◽  
Sahara Desert ◽  
Sensible Heat

AbstractTurbulent mixing in the planetary boundary layer (PBL) governs the vertical exchange of heat, moisture, momentum, trace gases, and aerosols in the surface–atmosphere interface. The PBL height (PBLH) represents the maximum height of the free atmosphere that is directly influenced by Earth’s surface. This study uses a multidata synthesis approach from an ensemble of multiple global datasets of radiosonde observations, reanalysis products, and climate model simulations to examine the spatial patterns of long-term PBLH trends over land between 60°S and 60°N for the period 1979–2019. By considering both the sign and statistical significance of trends, we identify large-scale regions where the change signal is robust and consistent to increase our confidence in the obtained results. Despite differences in the magnitude and sign of PBLH trends over many areas, all datasets reveal a consensus on increasing PBLH over the enormous and very dry Sahara Desert and Arabian Peninsula (SDAP) and declining PBLH in India. At the global scale, the changes in PBLH are significantly correlated positively with the changes in surface heating and negatively with the changes in surface moisture, consistent with theory and previous findings in the literature. The rising PBLH is in good agreement with increasing sensible heat and surface temperature and decreasing relative humidity over the SDAP associated with desert amplification, while the declining PBLH resonates well with increasing relative humidity and latent heat and decreasing sensible heat and surface warming in India. The PBLH changes agree with radiosonde soundings over the SDAP but cannot be validated over India due to lack of good-quality radiosonde observations.

scholarly journals A Framework for Convection and Boundary Layer Parameterization Derived from Conditional Filtering

2018 ◽  
Vol 75 (3) ◽  
pp. 965-981 ◽  
Author(s):  
John Thuburn ◽  
Hilary Weller ◽  
Geoffrey K. Vallis ◽  
Robert J. Beare ◽  
Michael Whitall
Keyword(s):  
Boundary Layer ◽  
Large Scale ◽  
Spatial Filter ◽  
Transport Processes ◽  
Atmospheric Models ◽  
Physical Processes ◽  
Straightforward Application ◽  
Different Types ◽  
Conceptual Link ◽  
Natural Way

Abstract A new theoretical framework is derived for parameterization of subgrid physical processes in atmospheric models; the application to parameterization of convection and boundary layer fluxes is a particular focus. The derivation is based on conditional filtering, which uses a set of quasi-Lagrangian labels to pick out different regions of the fluid, such as convective updrafts and environment, before applying a spatial filter. This results in a set of coupled prognostic equations for the different fluid components, including subfilter-scale flux terms and entrainment/detrainment terms. The framework can accommodate different types of approaches to parameterization, such as local turbulence approaches and mass flux approaches. It provides a natural way to distinguish between local and nonlocal transport processes and makes a clearer conceptual link to schemes based on coherent structures such as convective plumes or thermals than the straightforward application of a filter without the quasi-Lagrangian labels. The framework should facilitate the unification of different approaches to parameterization by highlighting the different approximations made and by helping to ensure that budgets of energy, entropy, and momentum are handled consistently and without double counting. The framework also points to various ways in which traditional parameterizations might be extended, for example, by including additional prognostic variables. One possibility is to allow the large-scale dynamics of all the fluid components to be handled by the dynamical core. This has the potential to improve several aspects of convection–dynamics coupling, such as dynamical memory, the location of compensating subsidence, and the propagation of convection to neighboring grid columns.

scholarly journals Current challenges in modelling far-range air pollution induced by the 2014–2015 Bárðarbunga fissure eruption (Iceland)

2016 ◽  
Vol 16 (17) ◽  
pp. 10831-10845 ◽  
Author(s):  
Marie Boichu ◽  
Isabelle Chiapello ◽  
Colette Brogniez ◽  
Jean-Christophe Péré ◽  
Francois Thieuleux ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Air Pollution ◽  
Vertical Distribution ◽  
Planetary Boundary Layer ◽  
Large Scale ◽  
Temporal Dynamics ◽  
Ground Level ◽  
Optical Absorption Spectroscopy ◽  
Sulfate Aerosols ◽  
Volcanic Cloud

Abstract. The 2014–2015 Holuhraun lava-flood eruption of Bárðarbunga volcano (Iceland) emitted prodigious amounts of sulfur dioxide into the atmosphere. This eruption caused a large-scale episode of air pollution throughout Western Europe in September 2014, the first event of this magnitude recorded in the modern era. We gathered chemistry-transport simulations and a wealth of complementary observations from satellite sensors (OMI, IASI), ground-based remote sensing (lidar, sunphotometry, differential optical absorption spectroscopy) and ground-level air quality monitoring networks to characterize both the spatial-temporal distributions of volcanic SO2 and sulfate aerosols as well as the dynamics of the planetary boundary layer. Time variations of dynamical and microphysical properties of sulfate aerosols in the aged low-tropospheric volcanic cloud, including loading, vertical distribution, size distribution and single scattering albedo, are provided. Retrospective chemistry-transport simulations at low horizontal resolution (25 km  ×  25 km) capture the correct temporal dynamics of this far-range air pollution event but fail to reproduce the correct magnitude of SO2 concentration at ground-level. Simulations at higher spatial resolution, relying on two nested domains with finest resolution of 7.3 km  ×  7.3 km, improve substantially the far-range vertical distribution of the volcanic cloud and subsequently the description of ground-level SO2 concentrations. However, remaining discrepancies between model and observations are shown to result from an inaccurate representation of the planetary boundary layer (PBL) dynamics. Comparison with lidar observations points out a systematic under-estimation of the PBL height by the model, whichever the PBL parameterization scheme. Such a shortcoming impedes the capture of the overlying Bárðarbunga cloud into the PBL at the right time and in sufficient quantities. This study therefore demonstrates the key role played by the PBL dynamics in accurately modelling large-scale volcanogenic air pollution.

Sensitivity of high-resolution precipitation to physics parameterization options in WRF over equatorial regions

2020 ◽  
Author(s):  
Martina Messmer ◽  
Santos J. González-Rojí ◽  
Christoph C. Raible ◽  
Thomas F. Stocker
Keyword(s):  
Boundary Layer ◽  
High Resolution ◽  
Planetary Boundary Layer ◽  
Large Scale ◽  
Wrf Model ◽  
Cumulus Parameterization ◽  
Wave Radiation ◽  
Strong Increase ◽  
Simulated Precipitation ◽  
The Impact

<p>Precipitation patterns and climate variability in East Africa and Western South America present high heterogeneity and complexity. This complexity is a result of large-scale and regional controls, such as surrounding oceans, lakes and topography. The combined effect of these controls has implications on precipitation and temperature, and hence, on water availability, biodiversity and ecosystem services. This study focuses on the impact of different physics parameterization in high-resolution experiments performed over equatorial regions with the Weather Research and Forecasting (WRF) model, and how these options affect the representation of precipitation in those regions.</p><p>As expected, weather and climate in equatorial regions are driven by physical processes different to those important in the mid-latitudes. Hence, it is necessary to test the parameterizations available in the WRF model. Several sensitivity simulations are performed over Kenya and Peru nesting the WRF model inside the state-of-the-art ERA5 reanalysis. A cascade of increasing grid resolutions is used in these simulations, reaching the spatial resolutions of 3 and 1 km in the innermost domains, and thus, convection permitting scales. Parameterization options of the planetary boundary layer (PBL), lake model, radiation, cumulus and microphysics schemes are changed, and their sensitivity to precipitation is tested. The year 2008 is simulated for each of the sensitivity simulations. This year is chosen as a good representative of precipitation dynamics and temperature, as it is neither abnormally wet or hot, nor dry or cold over Kenya and Peru. The simulated precipitation driven by the ERA5 reanalysis is compared against station data obtained from the WMO, and over Kenya additionally against observations from the Centre for Training and Integrated Research in ASAL Development (CETRAD).</p><p>Precipitation is strongly underestimated when adopting a typical parameterization setup for the mid-latitudes. However, results indicate that precipitation amounts and also patterns are substantially improved when changing the cumulus and PBL parameterisations. This strong increase in the simulated precipitation is obtained when using the Grell-Freitas ensemble, RRTM and the Yonsei University schemes for cumulus, long-wave radiation and planetary boundary layer, respectively. During some summer months, the accumulated precipitation is improved by up to 100 mm (80 %) compared to mid-latitudes configuration in several regions of the domains (near the Andes in Peru and over the flatlands in Kenya). Additionally, because the 1- and 2-way nesting options show a similar performance with respect to precipitation, the 1-way nesting option is preferred, as it does not overwrite the solutions in the parent domains. Hence, discontinuous solutions related to switching off the cumulus parameterization can be avoided.</p>

scholarly journals Planetary boundary layer height from CALIOP compared to radiosonde over China

2016 ◽  
Vol 16 (15) ◽  
pp. 9951-9963 ◽  
Author(s):  
Wanchun Zhang ◽  
Jianping Guo ◽  
Yucong Miao ◽  
Huan Liu ◽  
Yong Zhang ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Large Scale ◽  
Accurate Estimation ◽  
Orthogonal Polarization ◽  
Planetary Boundary Layer Height ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Spatial Coverage ◽  
Ground Based Lidar

Abstract. Accurate estimation of planetary boundary layer height (PBLH) is key to air quality prediction, weather forecast, and assessment of regional climate change. The PBLH retrieval from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) is expected to complement ground-based measurements due to the broad spatial coverage of satellites. In this study, CALIOP PBLHs are derived from combination of Haar wavelet and maximum variance techniques, and are further validated against PBLHs estimated from ground-based lidar at Beijing and Jinhua. Correlation coefficients between PBLHs from ground- and satellite-based lidars are 0.59 at Beijing and 0.65 at Jinhua. Also, the PBLH climatology from CALIOP and radiosonde are compiled over China during the period from 2011 to 2014. Maximum CALIOP-derived PBLH can be seen in summer as compared to lower values in other seasons. Three matchup scenarios are proposed according to the position of each radiosonde site relative to its closest CALIPSO ground tracks. For each scenario, intercomparisons were performed between CALIOP- and radiosonde-derived PBLHs, and scenario 2 is found to be better than other scenarios using difference as the criteria. In early summer afternoon over 70 % of the total radiosonde sites have PBLH values ranging from 1.6 to 2.0 km. Overall, CALIOP-derived PBLHs are well consistent with radiosonde-derived PBLHs. To our knowledge, this study is the first intercomparison of PBLH on a large scale using the radiosonde network of China, shedding important light on the data quality of initial CALIOP-derived PBLH results.

scholarly journals Parameterization of a surface drag coefficient in conventionally neutral planetary boundary layer

2004 ◽  
Vol 22 (10) ◽  
pp. 3353-3362 ◽  
Author(s):  
I. N. Esau
Keyword(s):  
Boundary Layer ◽  
Drag Coefficient ◽  
Planetary Boundary Layer ◽  
Large Scale ◽  
Surface Drag ◽  
Free Atmosphere ◽  
Mean Velocity ◽  
Dimensional Parameter ◽  
Drag Coefficients ◽  
Computational Level

Abstract. Modern large-scale models (LSMs) rely on surface drag coefficients to parameterize turbulent exchange between surface and the first computational level in the atmosphere. A classical parameterization in an Ekman boundary layer is rather simple. It is based on a robust concept of a layer of constant fluxes. In such a layer (log-layer), the mean velocity profile is logarithmic. It results in an universal dependence of the surface drag coefficient on a single internal non-dimensional parameter, namely the ratio of a height within this layer to a surface roughness length scale. A realistic near-neutral planetary boundary layer (PBL) is usually much more shallow than the idealized Ekman layer. The reason is that the PBL is developing against a stably stratified free atmosphere. The ambient atmospheric stratification reduces the PBL depth and simultaneously the depth of the log-layer. Therefore, the first computational level in the LSMs may be placed above the log-layer. In such a case, the classical parameterization is unjustified and inaccurate. The paper proposes several ways to improve the classical parameterization of the surface drag coefficient for momentum. The discussion is focused on a conventionally neutral PBL, i.e. on the neutrally stratified PBL under the stably stratified free atmosphere. The analysis is based on large eddy simulation (LES) data. This data reveals that discrepancy between drag coefficients predicted by the classical parameterization and the actual drag coefficients can be very large in the shallow PBL. The improved parameterizations provide a more accurate prediction. The inaccuracy is reduced to one-tenth of the actual values of the coefficients.

scholarly journals Planetary boundary layer height from CALIOP compared to radiosonde over China

2016 ◽  
Author(s):  
Wanchun Zhang ◽  
Jianping Guo ◽  
Yucong Miao ◽  
Huan Liu ◽  
Zhengqiang Li ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Large Scale ◽  
Early Summer ◽  
Accurate Estimation ◽  
Planetary Boundary Layer Height ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Spatial Coverage ◽  
Ground Based Lidar

Abstract. The accurate estimation of boundary layer height is key to air quality prediction, weather forecast and so on. The planetary boundary layer height (PBLH) retrieval from CALIOP is expected to complement the ground-based site measurement due to its large spatial coverage. To such end, we estimated PBLHs from CALIOP, using the combination of Haar wavelet and maximum variance techniques, which was validated against PBLHs from ground-based lidar at Beijing and Jinhua. Comparison between ground-based and satellite lidar shows good agreement with a correlation coefficient of 0.59 in Beijing and 0.65 in Jinhua. The PBLH climatology from CALIOP was compiled over China during 2011 to 2014. Maximum PBLH was seen in summer as compared to lower value in other seasons. Prior to intercomparisons between CALIOP- and radiosonde-derived PBLHs, three matchup scenarios were proposed according to the position of each radiosonde site relative to its closest CALIPSO ground tracks. The CALIOP observations belonging to Scenario 2 were found to be better for comparison with radiosonde-derived PBLH, owing to smaller difference between them. The PBLHs at early summer afternoon range from 1.6 km to 2.0 km, accounting for over 70 % of the total radiosonde sites. Overall, CALIOP-derived PBLHs seem to be well consistent with radiosonde-derived PBLHs. To our knowledge, this study is the first intercomparison study of PBLH over large scale using the radiosonde network of China, shedding important light on the data quality of initial CALIOP-derived PBLH results.

scholarly journals The dynamic-thermal structures of the planetary boundary layer dominated by synoptic circulations and the regular effect on air pollution in Beijing

2020 ◽  
Author(s):  
Yunyan Jiang ◽  
Jinyuan Xin ◽  
Ying Wang ◽  
Guiqian Tang ◽  
Yuxin Zhao ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Diurnal Variation ◽  
Planetary Boundary Layer ◽  
Large Scale ◽  
Coupling Effect ◽  
Thermal Structure ◽  
Regional Scale ◽  
Vertical Shear ◽  
Strong Wind ◽  
Vertical Coupling

Abstract. Synoptic circulations play important roles in meteorological conditions and air quality within the planetary boundary layer (PBL). Based on Lamb-Jenkinson weather typing and multiple field measurements, this study reveals the mechanism of how the coupling effects of multiscale circulations influence PBL structure and pollution. Due to the topographic blocking in the daytime, pollutants accumulate in the plain areas horizontally. The sinking divergent flows overlying on the rising convergent flows within the PBL inhibit the continuously upward dispersion of aerosols vertically. At night, the horizontal and vertical coupling mechanisms synergistically worsen the pollution. The large-scale environmental winds and regional-scale breezes affect the pollution directly via the horizontal coupling effect, which generates a pollution convergent zone of different directional flows. The relative strength of flows causes the severely polluted area to move around horizontally from 39° N to 41° N. In addition, the multiscale circulations regulate the mixing and diffusion of pollutants indirectly via the vertical coupling effect, which changes the PBL dynamic-thermal structure. The warm advection transported by the upper environmental winds overlies the cold advection transported by the lower regional breezes, generating strong wind direction shear and advective inversion. The capping inversion and the convergent sinking motion within the PBL suppress massive pollutants below the zero speed zone. The multilayer PBL under cyclonic circulation has no diurnal variation. Weak ambient winds strengthen the mountain breezes observably at night, the temperature inversion can reach 900 m. The nocturnal shallower PBL, consistent with the zero velocity zone between ambient and mountain winds, can reach 600 m. By contrast, the PBL under southwesterly circulation is a mono-layer with obvious diurnal variation, reaching 2000 m in the daytime. The strong winds circulations restrain the development of regional breezes, the zero speed zone is located at 400 m and the inversion is lower than 200 m at night. The PBL under westerly circulation has a hybrid structure with both multiple aerosol layers and diurnal variation. The inversion is generated by the vertical shear of zonal winds. Clean and strong north winds are dominated under anticyclone circulation, the vertical shear and the diurnal variation of thermal field disappear because of strong turbulent mixing, and there is no significant PBL structure. Our results imply that the algorithm of atmospheric environmental capacity under synoptic circulations, such as the cyclonic type, with a multilayer PBL needs to be improved.

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