scholarly journals An Empirical Investigation of Convective Planetary Boundary Layer Evolution and Its Relationship with the Land Surface

2005 ◽  
Vol 44 (6) ◽  
pp. 917-932 ◽  
Author(s):  
Joseph A. Santanello ◽  
Mark A. Friedl ◽  
William P. Kustas
Keyword(s):  
Boundary Layer ◽  
Soil Moisture ◽  
Surface Properties ◽  
Planetary Boundary Layer ◽  
Time Scales ◽  
Land Surface ◽  
Specific Humidity ◽  
Near Surface ◽  
Convective Planetary Boundary Layer ◽  
Daily Time

Abstract Relationships among convective planetary boundary layer (PBL) evolution and land surface properties are explored using data from the Atmospheric Radiation Measurement Program Cloud and Radiation Test Bed in the southern Great Plains. Previous attempts to infer surface fluxes from observations of the PBL have been constrained by difficulties in accurately estimating and parameterizing the conservation equation and have been limited to multiday averages or small samples of daily case studies. Using radiosonde and surface flux data for June, July, and August of 1997, 1999, and 2001, a conservation approach was applied to 132 sets of daily observations. Results highlight the limitations of using this method on daily time scales caused by the diurnal variability and complexity of entrainment. A statistical investigation of the relationship among PBL and both land surface and near-surface properties that are not explicitly included in conservation methods indicates that atmospheric stability in the layer of PBL growth is the most influential variable controlling PBL development. Significant relationships between PBL height and soil moisture, 2-m potential temperature, and 2-m specific humidity are also identified through this analysis, and it is found that 76% of the variance in PBL height can be explained by observations of stability and soil water content. Using this approach, it is also possible to use limited observations of the PBL to estimate soil moisture on daily time scales without the need for detailed land surface parameterizations. In the future, the general framework that is presented may provide a means for robust estimation of near-surface soil moisture and land surface energy balance over regional scales.

scholarly journals Sensitivity of Numerical Weather Forecasts to Initial Soil Moisture Variations in CFSv2

2016 ◽  
Vol 31 (6) ◽  
pp. 1973-1983 ◽  
Author(s):  
Paul A. Dirmeyer ◽  
Subhadeep Halder
Keyword(s):  
Boundary Layer ◽  
Soil Moisture ◽  
Time Scales ◽  
Land Surface ◽  
Forecast Model ◽  
Surface Fluxes ◽  
Near Surface ◽  
Weather Forecasts ◽  
Initial Soil Moisture ◽  
Initial Soil

Abstract When initial soil moisture is perturbed among ensemble members in the operational NWS global forecast model, surface latent and sensible fluxes are immediately affected much more strongly, systematically, and over a greater area than conventional land–atmosphere coupling metrics suggest. Flux perturbations are likewise transmitted to the atmospheric boundary layer more formidably than climatology-based metrics would indicate. Impacts are not limited to the traditional land–atmosphere coupling hot spots, but extend over nearly all ice-free land areas of the globe. Key to isolating this effect is that initial atmospheric states are identical among quantities correlated, pinpointing soil moisture and snow cover. A consequence of this high sensitivity is that significant positive impacts of realistic land surface initialization on the skill of deterministic near-surface temperature and humidity forecasts are also immediate and nearly universal during boreal spring and summer (the period investigated) and persist for at least 3 days over most land areas. Land surface initialization may be more broadly important for weather forecasts than previously realized, as the research focus historically has been on subseasonal-to-seasonal time scales. This study attempts to bridge the gap between climate studies with their associated coupling assessments and weather forecast time scales. Furthermore, errors in land surface initialization and shortcomings in the parameterization of atmospheric processes sensitive to surface fluxes may have greater consequences than previously recognized, the latter exemplified by the lack of impact on precipitation forecasts even though the simulation of boundary layer development is shown to be greatly improved with realistic soil moisture initialization.

scholarly journals Convective Planetary Boundary Layer Interactions with the Land Surface at Diurnal Time Scales: Diagnostics and Feedbacks

2007 ◽  
Vol 8 (5) ◽  
pp. 1082-1097 ◽  
Author(s):  
Joseph A. Santanello ◽  
Mark A. Friedl ◽  
Michael B. Ek
Keyword(s):  
Boundary Layer ◽  
Soil Moisture ◽  
Planetary Boundary Layer ◽  
Mixed Layer ◽  
Land Surface ◽  
Atmospheric Stability ◽  
Surface Fluxes ◽  
Surface Model ◽  
Wide Range ◽  
Convective Planetary Boundary Layer

Abstract The convective planetary boundary layer (PBL) integrates surface fluxes and conditions over regional and diurnal scales. As a result, the structure and evolution of the PBL contains information directly related to land surface states. To examine the nature and magnitude of land–atmosphere coupling and the interactions and feedbacks controlling PBL development, the authors used a large sample of radiosonde observations collected at the southern Atmospheric Research Measurement Program–Great Plains Cloud and Radiation Testbed (ARM-CART) site in association with simulations of mixed-layer growth from a single-column PBL/land surface model. The model accurately predicts PBL evolution and realistically simulates thermodynamics associated with two key controls on PBL growth: atmospheric stability and soil moisture. The information content of these variables and their influence on PBL height and screen-level temperature can be characterized using statistical methods to describe PBL–land surface coupling over a wide range of conditions. Results also show that the first-order effects of land–atmosphere coupling are manifested in the control of soil moisture and stability on atmospheric demand for evapotranspiration and on the surface energy balance. Two principal land–atmosphere feedback regimes observed during soil moisture drydown periods are identified that complicate direct relationships between PBL and land surface properties, and, as a result, limit the accuracy of uncoupled land surface and traditional PBL growth models. In particular, treatments for entrainment and the role of the residual mixed layer are critical to quantifying diurnal land–atmosphere interactions.

scholarly journals Summer temperature response to extreme soil water conditions in the Mediterranean transitional climate regime

2021 ◽  
Author(s):  
Stefano Materia ◽  
Constantin Ardilouze ◽  
Chloé Prodhomme ◽  
Markus G. Donat ◽  
Marianna Benassi ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Soil Moisture ◽  
Soil Water ◽  
Land Surface ◽  
Heat Waves ◽  
Climate Regime ◽  
Seasonal Forecasts ◽  
Near Surface ◽  
Surface Temperatures ◽  
The Mediterranean

AbstractLand surface and atmosphere are interlocked by the hydrological and energy cycles and the effects of soil water-air coupling can modulate near-surface temperatures. In this work, three paired experiments were designed to evaluate impacts of different soil moisture initial and boundary conditions on summer temperatures in the Mediterranean transitional climate regime region. In this area, evapotranspiration is not limited by solar radiation, rather by soil moisture, which therefore controls the boundary layer variability. Extremely dry, extremely wet and averagely humid ground conditions are imposed to two global climate models at the beginning of the warm and dry season. Then, sensitivity experiments, where atmosphere is alternatively interactive with and forced by land surface, are launched. The initial soil state largely affects summer near-surface temperatures: dry soils contribute to warm the lower atmosphere and exacerbate heat extremes, while wet terrains suppress thermal peaks, and both effects last for several months. Land-atmosphere coupling proves to be a fundamental ingredient to modulate the boundary layer state, through the partition between latent and sensible heat fluxes. In the coupled runs, early season heat waves are sustained by interactive dry soils, which respond to hot weather conditions with increased evaporative demand, resulting in longer-lasting extreme temperatures. On the other hand, when wet conditions are prescribed across the season, the occurrence of hot days is suppressed. The land surface prescribed by climatological precipitation forcing causes a temperature drop throughout the months, due to sustained evaporation of surface soil water. Results have implications for seasonal forecasts on both rain-fed and irrigated continental regions in transitional climate zones.

scholarly journals Combined Assimilation of Satellite Precipitation and Soil Moisture: A Case Study Using TRMM and SMOS Data

2017 ◽  
Vol 145 (12) ◽  
pp. 4997-5014 ◽  
Author(s):  
Liao-Fan Lin ◽  
Ardeshir M. Ebtehaj ◽  
Alejandro N. Flores ◽  
Satish Bastola ◽  
Rafael L. Bras
Keyword(s):  
Soil Moisture ◽  
Data Assimilation ◽  
Land Surface ◽  
Specific Humidity ◽  
Surface Model ◽  
Precipitation Data ◽  
Near Surface ◽  
Satellite Precipitation ◽  
Soil Moisture Data ◽  
Mean Square Errors

This paper presents a framework that enables simultaneous assimilation of satellite precipitation and soil moisture observations into the coupled Weather Research and Forecasting (WRF) and Noah land surface model through variational approaches. The authors tested the framework by assimilating precipitation data from the Tropical Rainfall Measuring Mission (TRMM) and soil moisture data from the Soil Moisture Ocean Salinity (SMOS) satellite. The results show that assimilation of both TRMM and SMOS data can effectively improve the forecast skills of precipitation, top 10-cm soil moisture, and 2-m temperature and specific humidity. Within a 2-day time window, impacts of precipitation data assimilation on the forecasts remain relatively constant for forecast lead times greater than 6 h, while the influence of soil moisture data assimilation increases with lead time. The study also demonstrates that the forecast skill of precipitation, soil moisture, and near-surface temperature and humidity are further improved when both the TRMM and SMOS data are assimilated. In particular, the combined data assimilation reduces the prediction biases and root-mean-square errors, respectively, by 57% and 6% (for precipitation); 73% and 27% (for soil moisture); 17% and 9% (for 2-m temperature); and 33% and 11% (for 2-m specific humidity).

scholarly journals Impact of planetary boundary layer turbulence on model climate and tracer transport

2014 ◽  
Vol 14 (23) ◽  
pp. 31627-31674
Author(s):  
E. L. McGrath-Spangler ◽  
A. Molod ◽  
L. E. Ott ◽  
S. Pawson
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Richardson Number ◽  
Surface Wind ◽  
Specific Humidity ◽  
Boreal Summer ◽  
Tracer Transport ◽  
Bulk Richardson Number ◽  
Turbulent Length Scale ◽  
Near Surface

Abstract. Planetary boundary layer (PBL) processes are important for weather, climate, and tracer transport and concentration. One measure of the strength of these processes is the PBL depth. However, no single PBL depth definition exists and several studies have found that the estimated depth can vary substantially based on the definition used. In the Goddard Earth Observing System (GEOS-5) atmospheric general circulation model, the PBL depth is particularly important because it is used to calculate the turbulent length scale that is used in the estimation of turbulent mixing. This study analyzes the impact of using three different PBL depth definitions in this calculation. Two definitions are based on the scalar eddy diffusion coefficient and the third is based on the bulk Richardson number. Over land, the bulk Richardson number definition estimates shallower nocturnal PBLs than the other estimates while over water this definition generally produces deeper PBLs. The near surface wind velocity, temperature, and specific humidity responses to the change in turbulence are spatially and temporally heterogeneous, resulting in changes to tracer transport and concentrations. Near surface wind speed increases in the bulk Richardson number experiment cause Saharan dust increases on the order of 1 × 10−4 kg m−2 downwind over the Atlantic Ocean. Carbon monoxide (CO) surface concentrations are modified over Africa during boreal summer, producing differences on the order of 20 ppb, due to the model's treatment of emissions from biomass burning. While differences in carbon dioxide (CO2) are small in the time mean, instantaneous differences are on the order of 10 ppm and these are especially prevalent at high latitude during boreal winter. Understanding the sensitivity of trace gas and aerosol concentration estimates to PBL depth is important for studies seeking to calculate surface fluxes based on near-surface concentrations and to studies projecting future concentrations.

scholarly journals Response of water use efficiency to summer drought in boreal Scots pine forests in Finland

2016 ◽  
Author(s):  
Yao Gao ◽  
Tiina Markkanen ◽  
Mika Aurela ◽  
Ivan Mammarella ◽  
Tea Thum ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Water Use Efficiency ◽  
Water Use ◽  
Time Scales ◽  
Scots Pine ◽  
Land Surface ◽  
Summer Drought ◽  
Ecosystem Level ◽  
Use Efficiency ◽  
Daily Time

Abstract. The influence of drought on plant functioning has received considerable attention in recent years, although our understanding of the response of carbon and water coupling in terrestrial ecosystems remains unclear. In this study, we investigated the response of water use efficiency to summer drought in boreal forests at daily time scales mainly using eddy covariance flux data. In addition, simulation results from the JSBACH land surface model were evaluated against the observed results. Two Scots pine (Pinus sylvestris) sites at Hyytiälä (southern Finland) and Sodankylä (northern Finland) were used in the study. Based on observed data, the ecosystem level water use efficiency (EWUE) showed a decrease only during a severe soil moisture drought at Hyytiälä, whereas the inherent water use efficiency (IWUE) increased when there was a severe soil moisture drought at Hyytiälä and a moderate soil moisture drought at Sodankylä. This indicates a decrease in surface conductance at the ecosystem level, but the decrease in evapotranspiration (ET) was alleviated because of the increased vapor pressure deficit (VPD) during drought. Moreover, the changes in IWUE implied that Scots pine has weaker response to drought in the southern site than in the northern site. Thus, IWUE is a more appropriate metric than EWUE for capturing the impact of soil moisture drought on plant functioning at daily time scales. In general, the results from transpiration based ecosystem level water use efficiency (EWUEt) and IWUE, and the transpiration based inherent water use efficiency (IWUEt) from JSBACH simulations were similar to the observed results. The deviated groups of gross primary production (GPP) and evapotranspiration (ET) under severe soil moisture drought in observed data at Hyytiälä were also successfully captured in the simulated results. However, deficiencies in the model were clearly seen by the limitation effect of air humidity on stomatal conductance in observed data. Our study provides a deeper understanding of carbon and water dynamics in the major boreal ecosystem. These findings highlight the importance of choosing a suitable plant functioning indicator when investigating the effects of drought, and suggest possible improvements to land surface models, which play an important role in the prediction of biosphere-atmosphere feedbacks in the climate system.

scholarly journals Impact of planetary boundary layer turbulence on model climate and tracer transport

2015 ◽  
Vol 15 (13) ◽  
pp. 7269-7286 ◽  
Author(s):  
E. L. McGrath-Spangler ◽  
A. Molod ◽  
L. E. Ott ◽  
S. Pawson
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Richardson Number ◽  
Surface Wind ◽  
Specific Humidity ◽  
Boreal Summer ◽  
Tracer Transport ◽  
Bulk Richardson Number ◽  
Turbulent Length Scale ◽  
Near Surface

Abstract. Planetary boundary layer (PBL) processes are important for weather, climate, and tracer transport and concentration. One measure of the strength of these processes is the PBL depth. However, no single PBL depth definition exists and several studies have found that the estimated depth can vary substantially based on the definition used. In the Goddard Earth Observing System (GEOS-5) atmospheric general circulation model, the PBL depth is particularly important because it is used to calculate the turbulent length scale that is used in the estimation of turbulent mixing. This study analyzes the impact of using three different PBL depth definitions in this calculation. Two definitions are based on the scalar eddy diffusion coefficient and the third is based on the bulk Richardson number. Over land, the bulk Richardson number definition estimates shallower nocturnal PBLs than the other estimates while over water this definition generally produces deeper PBLs. The near-surface wind velocity, temperature, and specific humidity responses to the change in turbulence are spatially and temporally heterogeneous, resulting in changes to tracer transport and concentrations. Near-surface wind speed increases in the bulk Richardson number experiment cause Saharan dust increases on the order of 1 × 10−4 kg m−2 downwind over the Atlantic Ocean. Carbon monoxide (CO) surface concentrations are modified over Africa during boreal summer, producing differences on the order of 20 ppb, due to the model's treatment of emissions from biomass burning. While differences in carbon dioxide (CO2) are small in the time mean, instantaneous differences are on the order of 10 ppm and these are especially prevalent at high latitude during boreal winter. Understanding the sensitivity of trace gas and aerosol concentration estimates to PBL depth is important for studies seeking to calculate surface fluxes based on near-surface concentrations and for studies projecting future concentrations.

Performance Assessment of New Land Surface and Planetary Boundary Layer Physics in the WRF-ARW

2010 ◽  
Vol 49 (4) ◽  
pp. 760-774 ◽  
Author(s):  
Robert C. Gilliam ◽  
Jonathan E. Pleim
Keyword(s):  
Boundary Layer ◽  
Air Quality ◽  
Planetary Boundary Layer ◽  
Land Surface ◽  
Mesoscale Model ◽  
New Physics ◽  
The Other ◽  
Surface Model ◽  
Temperature Structure ◽  
Near Surface

Abstract The Pleim–Xiu land surface model, Pleim surface layer scheme, and Asymmetric Convective Model (version 2) are now options in version 3.0 of the Weather Research and Forecasting model (WRF) Advanced Research WRF (ARW) core. These physics parameterizations were developed for the fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5) and have been used extensively by the air quality modeling community, so there was a need based on several factors to extend these parameterizations to WRF. Simulations executed with the new WRF physics are compared with simulations produced with the MM5 and another WRF configuration with a focus on the replication of near-surface meteorological conditions and key planetary boundary layer features. The new physics in WRF is recommended for retrospective simulations, in particular, those used to drive air quality simulations. In the summer, the error of all variables analyzed was slightly lower across the domain in the WRF simulation that used the new physics than in the similar MM5 configuration. This simulation had an even lower error than the other more common WRF configuration. For the cold season case, the model simulation was not as accurate as the other simulations overall, but did well in terms of lower 2-m temperature error in the western part of the model domain (plains and Rocky Mountains) and most of the Northeast. Both MM5 and the other WRF configuration had lower errors across much of the southern and eastern United States in the winter. The 2-m water vapor mixing ratio and 10-m wind were generally well simulated by the new physics suite in WRF when contrasted with the other simulations and modeling studies. Simulated planetary boundary layer features were compared with both wind profiler and aircraft observations, and the new WRF physics results in a more precise wind and temperature structure not only in the stable boundary layer, but also within most of the convective boundary layer. These results suggest that the WRF performance is now at or above the level of MM5. It is thus recommended to drive future air quality applications.

Development and Testing of a Surface Flux and Planetary Boundary Layer Model for Application in Mesoscale Models

1995 ◽  
Vol 34 (1) ◽  
pp. 16-32 ◽  
Author(s):  
Jonathan E. Pleim ◽  
Aijun Xiu
Keyword(s):  
Boundary Layer ◽  
Soil Moisture ◽  
Planetary Boundary Layer ◽  
Land Surface ◽  
Field Experiments ◽  
Weather Prediction ◽  
Surface Fluxes ◽  
Heat Fluxes ◽  
Global Climate Models ◽  
Pbl Model

Abstract Although the development of soil, vegetation, and atmosphere interaction models has been driven primarily by the need for accurate simulations of long-term energy and moisture budgets in global climate models, the importance of these processes at smaller scales for short-term numerical weather prediction and air quality studies is becoming more appreciated. Planetary boundary layer (PBL) development is highly dependent on the partitioning of the available net radiation into sensible and latent heat fluxes. Therefore, adequate treatmentof surface properties such as soil moisture and vegetation characteristics is essential for accurate simulation of PBL development, convective and low-level cloud processes, and the temperature and humidity of boundary layer air. In this paper, the development ofa simple coupled surface and PBL model, which is planned for incorporation into the Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model (MM4/5), is described. The soil-vegetation model is based on a simple force-restore algorithm with explicit soil moisture and evapotranspiration. The PBL model is a hybrid of nonlocal closure for convective conditions and eddy diffusion for all other conditions. A one-dimensional version of the model has been applied to several case studies from field experiments in both dry desert-like conditions (Wangara) and moist vegetated conditions(First International Satellite Land Surface Climatology Project Field Experiment) to demonstrate the model's ability to realistically simulate surface fluxes as well as PBL development. This new surface-PBL model is currently being incorporated into the MM4-MM5 system.

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