scholarly journals Effect of Evaporating Sea Spray on Heat Fluxes in a Marine Atmospheric Boundary Layer

2019 ◽  
Vol 49 (7) ◽  
pp. 1927-1948 ◽  
Author(s):  
Yevgenii Rastigejev ◽  
Sergey A. Suslov
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Air Temperature ◽  
Weather Prediction ◽  
Heat Fluxes ◽  
Total Heat ◽  
Vertical Profiles ◽  
Marine Atmospheric Boundary Layer ◽  
Wide Range ◽  
Vertical Distributions

AbstractA detailed analysis of the evaporating ocean spray effect on the vertical latent and sensible heat fluxes in a marine atmospheric boundary layer (MABL) for different droplet sizes, vertical distributions of air temperature, humidity, and turbulent intensity is presented. For our analysis we have employed a two-temperature nonequilibrium MABL model developed in our previous work. The obtained analytical and numerical solutions show that the latent and total heat fluxes are significantly enhanced by large droplets because these droplets produce steep vertical gradients of moisture and air temperature in a MABL. Small droplets, however, do not noticeably change the total heat flux but rather redistribute the energy between its sensible and latent components. It has been shown that evaporating spray affects the turbulent kinetic energy (thus the intensity of the vertical turbulent transport) mostly mechanically by altering the vertical distribution of the mass density of the air–spray mixture rather than thermodynamically by changing vertical profiles of the air temperature and moisture. Furthermore, we have found that the vertical profiles of heat fluxes are approximately self-similar for a wide range of defining parameters, that is, can be approximately scaled to a reference heat profile for a wide range of vertical distributions of the temperature, humidity, and turbulence intensity. The obtained analytical expressions for the vertical heat fluxes affected by the spray presence enable their quick and efficient calculations. This will allow for the future construction of a computationally efficient spray and accurate parameterization to be used in global weather prediction models.

scholarly journals A Review of Techniques for Diagnosing the Atmospheric Boundary Layer Height (ABLH) Using Aerosol Lidar Data

2019 ◽  
Vol 11 (13) ◽  
pp. 1590 ◽  
Author(s):  
Ruijun Dang ◽  
Yi Yang ◽  
Xiao-Ming Hu ◽  
Zhiting Wang ◽  
Shuwen Zhang
Keyword(s):  
Boundary Layer ◽  
Air Quality ◽  
Atmospheric Boundary Layer ◽  
Weather Prediction ◽  
Mixing Layer ◽  
Accurate Estimation ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Vertical Distributions ◽  
Multi Wavelength

The height of the atmospheric boundary layer (ABLH) or the mixing layer height (MLH) is a key parameter characterizing the planetary boundary layer, and the accurate estimation of that is critically important for boundary layer related studies, which include air quality forecasts and numerical weather prediction. Aerosol lidar is a powerful remote sensing instrument frequently used to retrieve the ABLH through detecting the vertical distributions of aerosol concentration. Presently available methods for ABLH determination from aerosol lidar are summarized in this review, including a lot of classical methodologies as well as some improved versions of them. Some new recently developed methods applying advanced techniques such as image edge detection, as well as some new methods based on multi-wavelength lidar systems, are also summarized. Although a lot of techniques have been proposed and have already given reasonable results in several studies, it is impossible to recommend a technique which is suitable in all atmospheric scenarios. More accurate instantaneous ABLH from robust techniques is required, which can be used to estimate or improve the boundary layer parameterization in the numerical model, or maybe possible to be assimilated into the weather and environment models to improve the simulation or forecast of weather and air quality in the future.

scholarly journals Continuous Daily Observation of the Marine Atmospheric Boundary Layer over the Kuroshio by a Helicopter Shuttle Service

2015 ◽  
Vol 32 (1) ◽  
pp. 3-21 ◽  
Author(s):  
Youichi Tanimoto ◽  
Kou Shimoyama ◽  
Shoichi Mori
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Dynamic Pressure ◽  
Japan Meteorological Agency ◽  
Observation System ◽  
Vertical Profiles ◽  
Marine Atmospheric Boundary Layer ◽  
Near Surface ◽  
Ocean Front ◽  
Observation Method

AbstractThis paper describes a new initiative in which in situ observations of the marine atmospheric boundary layer (MABL) are made by a helicopter shuttle connecting six islands south of Tokyo. This observation method aims to make frequent measurements of temperature and moisture in the MABL across an ocean front, where direct measurements of the MABL have been limited. An onboard observation system to meet flight regulations was developed. Observed temperature and moisture as a function of pressure at 1-s intervals provided vertical profiles up to the 900-hPa level above each of the islands, from 24 December 2010 to 6 April 2011, with the exception of an accidental power down in mid-February 2011. The observed values are validated by intercomparison with surface measurements from weather stations, atmospheric soundings, and mesoscale weather analysis provided by the Japan Meteorological Agency. Temperature and moisture values obtained using the system described here at the surface are significantly correlated with those from the weather station. The meridional changes revealed by the observed vertical profiles depict rich MABL structures, such as a cold-air intrusion and a strong near-surface inversion, that are not captured by the mesoscale weather analysis. However, this discrepancy is probably due to insufficient treatment in the mesoscale numerical model rather than observational errors. Additional intercomparisons indicate no influence from either artificial mixing by the helicopter rotor or by dynamic pressure caused by the fast-moving helicopter when obtaining the vertical profiles. Following these validations, the continuation of the initiative will allow for examining the influence of the ocean front on the overlying MABL on a synoptic time scale.

Submesoscale physical processes in the atmospheric boundary layer above fragmented sea ice.

2020 ◽  
Author(s):  
Marta Wenta ◽  
Agnieszka Herman
Keyword(s):  
Boundary Layer ◽  
Numerical Modelling ◽  
Sea Ice ◽  
Atmospheric Boundary Layer ◽  
Weather Prediction ◽  
Heat Fluxes ◽  
Physical Processes ◽  
Sea Ice Extent ◽  
Field Campaign ◽  
Modelling Studies

<p>In consequence of sea ice fragmentation in winter a range of physical processes take place between the sea/sea ice and the atmospheric boundary layer (ABL). Most of them occur on the level of individual ice floes and cracks and thus cannot be directly resolved by numerical weather prediction (NWP) models.  Parametrizations of those processes aim to describe their overall effect on grid scale values, given the grid scale variables. However, as many of the processes taking place during winter sea ice fragmentation remain largely unrecognized they cannot be incorporated into the NWP models. </p><p>The aim of the presented study is to determine whether the floe size distribution (FSD) has an effect on the ABL. Our previous research (Wenta, Herman 2018 and 2019) indicates that FSD might determine the intensity and spatial arrangement of convection and heat fluxes. A coefficient has been proposed for the correction of moisture heat flux, which can be incorporated into the NWP models. However, this research is based entirely on idealized model simulations and requires further modelling and observations based studies.</p><p>In order to address this shortcoming, a field campaign is going to take place in the Bay of Bothnia in March 2020. Our goal is to create a 3D view of the atmosphere above fragmented sea and verify whether the processes and effects we found in the modeling results take similar form in real situations. Measurements results will be useful in the validation of our numerical modelling studies and will provide a unique dataset about the sea-ice-atmosphere interactions in the Bay of Bothnia area. Considering a significant decreasing trend in winter sea ice extent in the Baltic Sea it might contribute to our understanding of the role of ice in the local weather patterns. The field campaign is going to be complemented by numerical modelling with full version of Weather Research and Forecasting (WRF) model adjusted to the conditions over the Bay of Bothnia. </p><p>Combined together - the results of our previous modelling studies and the results from the Bay of Bothnia field campaign, may considerably increase our knowledge about the surface-atmosphere coupling in the event of winter sea ice fragmentation.</p>

The Use of Ship-Launched Fixed-Wing UAVs for Measuring the Marine Atmospheric Boundary Layer and Ocean Surface Processes

2016 ◽  
Vol 33 (9) ◽  
pp. 2029-2052 ◽  
Author(s):  
Benjamin D. Reineman ◽  
Luc Lenain ◽  
W. Kendall Melville
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Meteorological Data ◽  
Ocean Surface ◽  
Heat Fluxes ◽  
Surface Processes ◽  
Marine Atmospheric Boundary Layer ◽  
Central Pacific ◽  
Spatiotemporal Resolution ◽  
X Band

AbstractThe deployment and recovery of autonomous or remotely piloted platforms from research vessels have become a way of significantly extending the capabilities and reach of the research fleet. This paper describes the use of ship-launched and ship-recovered Boeing–Insitu ScanEagle unmanned aerial vehicles (UAVs). The UAVs were instrumented to characterize the marine atmospheric boundary layer (MABL) structure and dynamics, and to measure ocean surface processes during the October 2012 Equatorial Mixing (EquatorMix) experiment in the central Pacific and during the July 2013 Trident Warrior experiment off the Virginia coast. The UAV measurements, including atmospheric momentum and radiative, sensible, and latent heat fluxes, are complemented by measurements from ship-based instrumentation, including a foremast MABL eddy-covariance system, lidar altimeters, and a digitized X-band radar system. During EquatorMix, UAV measurements reveal longitudinal atmospheric roll structures not sampled by ship measurements, which contribute significantly to vertical fluxes of heat and momentum. With the nadir-looking UAV lidar, surface signatures of internal waves are observed, consistent and coherent with measurements from ship-based X-band radar, a Hydrographic Doppler Sonar System, and a theoretical model. In the Trident Warrior experiment, the instrumented UAVs were used to demonstrate real-time data assimilation of meteorological data from UAVs into regional coupled ocean–atmosphere models. The instrumented UAVs have provided unprecedented spatiotemporal resolution in atmospheric and oceanographic measurements in remote ocean locations, demonstrating the capabilities of these platforms to extend the range and capabilities of the research fleet for oceanographic and atmospheric studies.

scholarly journals Estimation of Turbulent Heat Fluxes via Assimilation of Air Temperature and Specific Humidity into an Atmospheric Boundary Layer Model

2020 ◽  
Vol 21 (2) ◽  
pp. 205-225 ◽  
Author(s):  
E. Tajfar ◽  
S. M. Bateni ◽  
S. A. Margulis ◽  
P. Gentine ◽  
T. Auligne
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Air Temperature ◽  
Potential Temperature ◽  
Heat Fluxes ◽  
Specific Humidity ◽  
Turbulent Heat ◽  
Layer Model ◽  
Ground Heat Flux ◽  
Turbulent Heat Fluxes

AbstractA number of studies have used time series of air temperature and specific humidity observations to estimate turbulent heat fluxes. These studies require the specification of surface roughness lengths for heat and momentum (that are directly related to the neutral bulk heat transfer coefficient CHN) and/or ground heat flux, which are often unavailable. In this study, sequences of air temperature and specific humidity are assimilated into an atmospheric boundary layer model within a variational data assimilation (VDA) framework to estimate CHN, evaporative fraction (EF), turbulent heat fluxes, and atmospheric boundary layer (ABL) height, potential temperature, and humidity. The developed VDA approach needs neither the surface roughness parameterization (as it is optimized by the VDA approach) nor ground heat flux measurements. The VDA approach is tested over the First International Satellite Land Surface Climatology Project Field Experiment (FIFE) site in the summers of 1987 and 1988. The results indicate that the estimated sensible and latent heat fluxes agree fairly well with the corresponding measurements. For FIFE 1987 (1988), the daily sensible and latent heat fluxes estimates have a root-mean-square error of 25.72 W m−2 (27.77 W m−2) and 53.63 W m−2 (48.22 W m−2), respectively. In addition, the ABL height, specific humidity, and potential temperature estimates from the VDA system are in good agreement with those inferred from the radiosondes both in terms of magnitude and diurnal trend.

Evolution of Marine Atmospheric Boundary Layer Structure across the Cold Tongue–ITCZ Complex

2005 ◽  
Vol 18 (5) ◽  
pp. 737-753 ◽  
Author(s):  
Hollis E. Pyatt ◽  
Bruce A. Albrecht ◽  
Chris Fairall ◽  
J. E. Hare ◽  
Nicholas Bond ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Layer Structure ◽  
Surface Wind ◽  
Surface Fluxes ◽  
Heat Fluxes ◽  
Cold Tongue ◽  
Marine Atmospheric Boundary Layer ◽  
Cold Side ◽  
Sst Front

Abstract The structure of the marine atmospheric boundary layer (MABL) over the tropical eastern Pacific Ocean is influenced by spatial variations of sea surface temperature (SST) in the region. As the MABL air is advected across a strong SST gradient associated with the cold tongue–ITCZ complex (CTIC), substantial changes occur in the thermodynamic structure, surface fluxes, and cloud properties. This study attempts to define and explain the variability in the MABL structure and clouds over the CTIC. Using data collected on research cruises from the fall seasons of 1999–2001, composite soundings were created for both the cold and warm sides of the SST front to describe the mean atmospheric boundary layer (ABL) structure and its evolution across this front. The average difference in SST across this front was ∼6°C; much of this difference was concentrated in a band only ∼50 km wide. During the fall seasons, on the cold side of the gradient, a well-defined inversion exists in all years. Below this inversion, both fair-weather cumulus and stratiform clouds are observed. As the MABL air moves over the SST front to warmer waters, the inversion weakens and increases in height. The MABL also moistens and eventually supports deeper convection over the ITCZ. Both the latent and sensible heat fluxes increase dramatically across the SST front because of both an increase in SST and surface wind speed. Cloudiness is variable on the cold side of the SST front ranging from 0.2 to 0.9 coverage. On the warm side, cloud fraction was quite constant in time, with values generally greater than 0.8. The highest cloud-top heights (>3 km) are found well north of the SST front, indicating areas of deeper convection. An analysis using energy and moisture budgets identifies the roles of various physical processes in the MABL evolution.

scholarly journals Assessment of NWP Forecast Models in Simulating Offshore Winds through the Lower Boundary Layer by Measurements from a Ship-Based Scanning Doppler Lidar

2017 ◽  
Vol 145 (10) ◽  
pp. 4277-4301 ◽  
Author(s):  
Yelena L. Pichugina ◽  
Robert M. Banta ◽  
Joseph B. Olson ◽  
Jacob R. Carley ◽  
Melinda C. Marquis ◽  
...  
Keyword(s):  
Boundary Layer ◽  
High Resolution ◽  
Atmospheric Boundary Layer ◽  
Weather Prediction ◽  
Doppler Lidar ◽  
Marine Atmospheric Boundary Layer ◽  
Lidar Measurements ◽  
Forecast Models ◽  
The Impact ◽  
The U.S

Evaluation of model skill in predicting winds over the ocean was performed by comparing retrospective runs of numerical weather prediction (NWP) forecast models to shipborne Doppler lidar measurements in the Gulf of Maine, a potential region for U.S. coastal wind farm development. Deployed on board the NOAA R/V Ronald H. Brown during a 2004 field campaign, the high-resolution Doppler lidar (HRDL) provided accurate motion-compensated wind measurements from the water surface up through several hundred meters of the marine atmospheric boundary layer (MABL). The quality and resolution of the HRDL data allow detailed analysis of wind flow at heights within the rotor layer of modern wind turbines and data on other critical variables to be obtained, such as wind speed and direction shear, turbulence, low-level jet properties, ramp events, and many other wind-energy-relevant aspects of the flow. This study will focus on the quantitative validation of NWP models’ wind forecasts within the lower MABL by comparison with HRDL measurements. Validation of two modeling systems rerun in special configurations for these 2004 cases—the hourly updated Rapid Refresh (RAP) system and a special hourly updated version of the North American Mesoscale Forecast System [NAM Rapid Refresh (NAMRR)]—are presented. These models were run at both normal-resolution (RAP, 13 km; NAMRR, 12 km) and high-resolution versions: the NAMRR-CONUS-nest (4 km) and the High-Resolution Rapid Refresh (HRRR, 3 km). Each model was run twice: with (experimental runs) and without (control runs) assimilation of data from 11 wind profiling radars located along the U.S. East Coast. The impact of the additional assimilation of the 11 profilers was estimated by comparing HRDL data to modeled winds from both runs. The results obtained demonstrate the importance of high-resolution lidar measurements to validate NWP models and to better understand what atmospheric conditions may impact the accuracy of wind forecasts in the marine atmospheric boundary layer. Results of this research will also provide a first guess as to the uncertainties of wind resource assessment using NWP models in one of the U.S. offshore areas projected for wind plant development.

Direct numerical simulation of droplet-mediated exchange fluxes in the marine atmospheric boundary layer

2021 ◽  
Author(s):  
Oleg Druzhinin
Keyword(s):  
Numerical Simulation ◽  
Boundary Layer ◽  
Direct Numerical Simulation ◽  
Atmospheric Boundary Layer ◽  
Common Knowledge ◽  
Numerical Algorithms ◽  
Heat Fluxes ◽  
Marine Atmospheric Boundary Layer ◽  
Russian Science ◽  
Bulk Parameters

<p>Now it is a common knowledge that at sufficiently strong winds, sea-spray droplets interfere with  turbulent exchange processes occurring between atmosphere and hydrosphere. The results of field and laboratory experiments show that mass fraction of air-borne spume water droplets increases with the wind speed and their impact on the marine atmospheric boundary layer may become significant. The contribution of droplets to the momentum and sensible and latent heat fluxes may be crucial for our understanding of conditions favorable for the development of anomalous weather phenomena such as tropical hurricanes and polar lows. Phenomenological models and bulk algorithms are mostly based on hypothetical assumptions concerning the properties of droplet-air interaction which strongly influence the accuracy of their forecast. Lagrangian stochastic modeling also requires an adhoc knowledge of the properties of turbulent fields ‘seen’ by the droplets along their trajectories. These details of droplet-air interaction are difficult to measure in lab conditions and can be gleaned via direct numerical simulation (DNS). DNS solves primitive equations for the carrier air in the Eulerian frame and of droplets motion in a Lagrangian frame and accounts for the two-way coupling of momentum, heat and moisture between the carrier and dispersed phases, and allows us to investigate the droplet contribution to the exchange fluxes under different injection conditions and flow bulk parameters. The results obtained for different conditions show us that droplets dynamics and their contribution to the momentum and heat fluxes are controlled by many factors including droplets velocity at injection, the gravitational settling velocity, surface wave slope, bulk relative humidity and temperature of the atmospheric boundary layer as compared to the sea surface conditions.</p><p>This work is supported by the Ministry of Education and Science of the Russian Federation (Task No. 0030-2019-0020). Numerical algorithms were developed under the support of RFBR (20-05-00322, 21-55-52005, 18-05-60299). Postprocessing was performed under the support of the Russian Science Foundation (No. 19-17-00209).</p>

scholarly journals Characteristics of aerosol vertical profiles in Tsukuba, Japan, and their impacts on the evolution of the atmospheric boundary layer

2018 ◽  
Author(s):  
Rei Kudo ◽  
Toshinori Aoyagi ◽  
Tomoaki Nishizawa
Keyword(s):  
Boundary Layer ◽  
Optical Properties ◽  
Atmospheric Boundary Layer ◽  
Latent Heat ◽  
Optical Thickness ◽  
Heat Fluxes ◽  
Vertical Profiles ◽  
Direct Heating ◽  
Downward Radiation ◽  
Capping Inversion

Abstract. Vertical profiles of the aerosol physical and optical properties, with a focus on seasonal means and on transport events, were investigated in Tsukuba, Japan, by a synergistic remote sensing method that uses lidar and sky radiometer data. The retrieved aerosol vertical profiles were input into our developed one-dimensional atmospheric model, and the impacts of the aerosol vertical profiles on the evolution of the atmospheric boundary layer (ABL) were studied by numerical sensitivity experiments. The retrieval results in the spring showed that aerosol optical thickness was greater in the free atmosphere (FA) than in the ABL owing to the frequent occurrence of transported aerosols in the FA. In other seasons, optical thickness in the FA was almost the same as that in the ABL. The aerosol optical and physical properties in the ABL showed a dependency on the extinction coefficient, whereas large variability in the physical and optical properties of aerosols in the FA were attributed to transport events, during which the transported aerosols consisted of varying amounts of dust and smoke particles depending on where they originated (China, Mongolia, or Russia). Numerical sensitivity experiments based on simulations conducted with and without aerosols showed that aerosols caused the net downward radiation and the sensible and latent heat fluxes at the surface to decrease. Direct heating of aerosols in the FA strengthened the capping inversion around the top of the ABL. Consequently, the ABL height was decreased in simulations with aerosols compared with simulations without aerosols. We also conducted simulations in which all aerosols were compressed into the ABL but in which the columnar properties were the same and compared with the simulation results for uncompressed aerosol profiles. The results showed that the reductions in net downward radiation and in sensible and latent heat fluxes were the same in both types of simulations, but in the simulations with compression the capping inversion was weakened owing to aerosol direct heating in the ABL, and as a result the ABL height was increased compared with that in the simulations without compression. These results suggest that the vertical profile of aerosol direct heating has important effects on the ABL evolution.

Sign in / Sign up

Export Citation Format

Share Document