Estimation of Stratocumulus-Topped Boundary Layer Depth Using Sea Surface and Remotely Sensed Cloud-Top Temperatures PDF Download
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Author: Marvin B. McBride, III
Publisher:
ISBN: 9781423536123
Category :
Languages : en
Pages : 94
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Book Description
The depth of the marine atmospheric boundary layer (MABL) is an important parameter for both scientific and operational meteorological applications. The depth of the marine boundary layer has a significant influence on the atmospheric dynamics in the coastal zone. Knowledge of the depth of stratocumulus-topped boundary layers (STELs) will enable coastal operations to more accurately anticipate weather, and electromagnetic propagation conditions. This study develops a satellite remote sensing technique for determining the height of MABLs topped with stratocumulus clouds. Validation of the technique using coastal rawinsonde dataset from the Monterey Area Ship Track (MAST) experiment revealed that an assumption of 41% cloud with a moist lapse rate equal to -7.0 deg C/km had the best overall fit to the data. However, for shallow boundary layers with depths below 400m the most accurate assumption was 75% cloud with a moist lapse rate equal to -6.5 deg C/km. The application of this technique to sounding data returned an overall BL depth accuracy of 50m while the satellite application returned an overall accuracy of 65m. A sensitivity analysis of both surface and cloud-top temperature revealed that a 1/2 deg C change in either temperature resulted in an error of 60-70m in boundary layer depth.
Author: Marvin B. McBride, III
Publisher:
ISBN: 9781423536123
Category :
Languages : en
Pages : 94
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Book Description
The depth of the marine atmospheric boundary layer (MABL) is an important parameter for both scientific and operational meteorological applications. The depth of the marine boundary layer has a significant influence on the atmospheric dynamics in the coastal zone. Knowledge of the depth of stratocumulus-topped boundary layers (STELs) will enable coastal operations to more accurately anticipate weather, and electromagnetic propagation conditions. This study develops a satellite remote sensing technique for determining the height of MABLs topped with stratocumulus clouds. Validation of the technique using coastal rawinsonde dataset from the Monterey Area Ship Track (MAST) experiment revealed that an assumption of 41% cloud with a moist lapse rate equal to -7.0 deg C/km had the best overall fit to the data. However, for shallow boundary layers with depths below 400m the most accurate assumption was 75% cloud with a moist lapse rate equal to -6.5 deg C/km. The application of this technique to sounding data returned an overall BL depth accuracy of 50m while the satellite application returned an overall accuracy of 65m. A sensitivity analysis of both surface and cloud-top temperature revealed that a 1/2 deg C change in either temperature resulted in an error of 60-70m in boundary layer depth.
Author: Marvin B. McBride
Publisher:
ISBN:
Category :
Languages : en
Pages : 82
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Book Description
The depth of the marine atmospheric boundary layer (MABL) is an important parameter for both scientific and operational meteorological applications. The depth of the marine boundary layer has a significant influence on the atmospheric dynamics in the coastal zone. Knowledge of the depth of stratocumulus-topped boundary layers (STELs) will enable coastal operations to more accurately anticipate weather, and electromagnetic propagation conditions. This study develops a satellite remote sensing technique for determining the height of MABLs topped with stratocumulus clouds. Validation of the technique using coastal rawinsonde dataset from the Monterey Area Ship Track (MAST) experiment revealed that an assumption of 41% cloud with a moist lapse rate equal to -7.0 deg C/km had the best overall fit to the data. However, for shallow boundary layers with depths below 400m the most accurate assumption was 75% cloud with a moist lapse rate equal to -6.5 deg C/km. The application of this technique to sounding data returned an overall BL depth accuracy of 50m while the satellite application returned an overall accuracy of 65m. A sensitivity analysis of both surface and cloud-top temperature revealed that a 1/2 deg C change in either temperature resulted in an error of 60-70m in boundary layer depth.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 94
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Book Description
The depth of the marine atmospheric boundary layer (MABL) is an important parameter for both scientific and operational meteorological applications. The depth of the marine boundary layer has a significant influence on the atmospheric dynamics in the coastal zone. Knowledge of the depth of stratocumulus-topped boundary layers (STELs) will enable coastal operations to more accurately anticipate weather, and electromagnetic propagation conditions. This study develops a satellite remote sensing technique for determining the height of MABLs topped with stratocumulus clouds. Validation of the technique using coastal rawinsonde dataset from the Monterey Area Ship Track (MAST) experiment revealed that an assumption of 41% cloud with a moist lapse rate equal to -7.0 deg C/km had the best overall fit to the data. However, for shallow boundary layers with depths below 400m the most accurate assumption was 75% cloud with a moist lapse rate equal to -6.5 deg C/km. The application of this technique to sounding data returned an overall BL depth accuracy of 50m while the satellite application returned an overall accuracy of 65m. A sensitivity analysis of both surface and cloud-top temperature revealed that a 1/2 deg C change in either temperature resulted in an error of 60-70m in boundary layer depth.
Author: Mohamed Sherif Ghonima
Publisher:
ISBN:
Category :
Languages : en
Pages : 130
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Book Description
Stratocumulus is the most common cloud type and has a strong impact on global climate. Over coastal lands, which are frequently well populated, these clouds have a strong impact on surface temperature and radiation through reflection of incoming solar radiation. The cloud behavior is determined both by small-scale processes such as turbulent mixing between two-phase, two-component, fluids at the cloud top and large-scale circulation such as anticyclones and their climatological occurrence. Due to the large range of spatial scales associated with stratocumulus clouds, global climate models (GCM) and numerical weather prediction models (NWP) parameterize the physical processes occurring in the stratocumulus-topped boundary layer (STBL). However, these models are unable to simulate the clouds accurately. For instance, in the North American Model stratocumulus clouds over the California coast in the summer dissipate earlier than observed via satellite. In this thesis, we first employ high-resolution Large Eddy Simulations (LES) and Mixed Layer Models (MLM) to study mechanisms regulating the timing of the break up. We find that over coastal lands, as the cloud thins during day, turbulence generated by surface fluxes becomes larger than turbulence generated by longwave cooling across the cloud layer. To capture this shift in turbulence generation in the MLM, we extend an existing entrainment parameterization to account for both sources. We find that cloud lifetime depends on a combination of surface moisture content, cloud-top entrainment flux, and large-scale horizontal advection by sea breeze. Next, we evaluate three different planetary boundary layer (PBL) parameterization schemes in the Weather Research and Forecasting (WRF) model in simulating the STBL by benchmarking them against high-resolution LES. We find that the schemes do not take into account the turbulence generated by longwave cooling across the cloud layer and therefore underestimate the mixing of warm-dry tropospheric into the STBL at the cloud top. Thus, we propose a correction to the eddy diffusivity coefficient by adding a term that accounts for turbulence generated throughout the cloud layer as well as at the surface due to buoyancy flux. The modified scheme is then able to simulate the cloud physics similar to that of the LES. The modeling tools developed in this thesis have improved the understanding of and the ability to forecast stratocumulus-topped boundary layers.
Author: Thomas A. Guinn
Publisher:
ISBN:
Category : Boundary layer (Meteorology)
Languages : en
Pages : 63
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Book Description
A coupled convective-radiative, boundary-layer model of marine stratocumulus clouds is presented. The model, which slightly generalized Lilly's (1968) cloud-topped mixed-layer model, has as dependent variables the cloud-top height, the cloud-base height, mixed-layer equivalent potential temperature and total water mixing ratio, the turbulent fluxes of equivalent potential temperature, total water mixing ratio, and virtual potential temperature, the cloud-top jumps of equivalent potential temperature and total water mixing ratio, the cloud-top temperature, and the net radiative flux divergence at cloud top and in the mixed layer. Keywords: Stratosphere. (EG).
Author: Daniel P. Eleuterio
Publisher:
ISBN: 9781423518709
Category : Boundary layer (Meteorology)
Languages : en
Pages : 134
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Book Description
The ability of the U.S. Navy's Coupled Ocean-Atmosphere Mesoscale Prediction System (COAMPS) (Trademark) to accurately forecast the height and structure of the Marine Boundary Layer (MBL) in the coastal zone is analyzed and compared to surface and aircraft observations from the Dynamics and Evolution of Coastal Stratus (DECS) field study conducted along the central coast of California from June 16 to July 22, 1999. The stratus field was found to have significant mesoscale variability within 100 km of the coast due to interaction between the mean flow and the coastal terrain. This structure is consistent with general hydraulic flow theory and the development of a low-level coastal jet. However, the specific characteristics on any given day were very sensitive to flow direction, inversion height, and synoptic conditions. With some modifications, the model predicted the general evolution of these events with qualitative fidelity, but was slow to dissipate the cloud and frequently produced surface fog versus stratus. A consistent tendency was found in the model's predictions of inversion heights 200-300 meters too low, weak inversion strengths, high integrated liquid water content, and weak buoyancy flux near the cloud top. These observed biases are consistent with underestimating the cloud top entrainment velocity and entrainment fluxes in the modeled boundary layer. An explicit entrainment parameterization was developed to better represent the sub-grid scale processes at cloud top and was tested in the single column and 3D versions of COAMPS. The entrainment parameterization was found to improve the boundary layer height and cloud liquid water content as compared to field observations, but the modeled boundary layer still exhibited a low bias, and the entrainment velocity was higher than is generally expected from field studies for this regime. (2 tables, 53 figures. 80 refs.) ANNOTATION: The Role of Cloud-Top Entrainment in Coastal Stratocumulus-Topped Boundary Layers
Author: M.K. Yau
Publisher: Elsevier
ISBN: 0080570941
Category : Science
Languages : en
Pages : 308
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Book Description
Covers essential parts of cloud and precipitation physics and has been extensively rewritten with over 60 new illustrations and many new and up to date references. Many current topics are covered such as mesoscale meteorology, radar cloud studies and numerical cloud modelling, and topics from the second edition, such as severe storms, precipitation processes and large scale aspects of cloud physics, have been revised. Problems are included as examples and to supplement the text.
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 970
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Book Description
Author:
Publisher:
ISBN:
Category : Astrophysics
Languages : en
Pages : 480
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 22
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Book Description
A 60-hour case study of continental boundary layer cumulus clouds is examined using two large-eddy simulation (LES) models. The case is based on observations obtained during the RACORO Campaign (Routine Atmospheric Radiation Measurement [ARM] Aerial Facility [AAF] Clouds with Low Optical Water Depths [CLOWD] Optical Radiative Observations) at the ARM Climate Research Facility's Southern Great Plains site. The LES models are driven by continuous large-scale and surface forcings, and are constrained by multi-modal and temporally varying aerosol number size distribution profiles derived from aircraft observations. We compare simulated cloud macrophysical and microphysical properties with ground-based remote sensing and aircraft observations. The LES simulations capture the observed transitions of the evolving cumulus-topped boundary layers during the three daytime periods, and generally reproduce variations of droplet number concentration with liquid water content (LWC), corresponding to the gradient between the cloud centers and cloud edges at given heights. The observed LWC values fall within the range of simulated values; the observed droplet number concentrations are commonly higher than simulated, but differences remain on par with potential estimation errors in the aircraft measurements. Sensitivity studies examine the influences of bin microphysics versus bulk microphysics, aerosol advection, supersaturation treatment, and aerosol hygroscopicity. Simulated macrophysical cloud properties are found to be insensitive in this non-precipitating case, but microphysical properties are especially sensitive to bulk microphysics supersaturation treatment and aerosol hygroscopicity.
