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

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 of the springtime mean and five transport events were input to 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 characteristics of the aerosol vertical profiles in Tsukuba are as follows: (1) the retrieval results in the spring showed that aerosol optical thickness at 532 nm in the free atmosphere (FA) was 0.13, greater than 0.08 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. (2) The aerosol optical and physical properties in the ABL showed a dependency on the extinction coefficient. With an increase in the extinction coefficient from 0.00 to 0.24 km−1, the Ångström exponent increased from 0.0 to 2.0, the single-scattering albedo increased from 0.87 to 0.99, and the asymmetry factor decreased from 0.75 to 0.50. (3) The 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). The results of the numerical sensitivity experiments using the aerosol vertical profiles of the springtime mean and five transport events in the FA are as follows: (1) 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. The decrease in temperature in the ABL (−0.2 to −0.6 K) and the direct heating of aerosols in the FA (0.0 to 0.4 K) strengthened the capping inversion around the top of the ABL. Consequently, the ABL height was decreased by 133 to 208 m in simulations with aerosols compared to simulations without aerosols. (2) 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. However, the capping inversion in the simulations with compression was weakened owing to aerosol direct heating in the ABL and the lack of direct heating in the FA. This resulted in an increase in the ABL height, compared with that in the simulations without compression. (3) The dependencies of the 2 m temperature and ABL height on the optical thickness and Ångström exponent in the FA were investigated using the results of the numerical sensitivity tests. The 2 m temperature and ABL height was decreased with an increase in the optical thickness, and their reduction rates increase with a decrease in the Ångström exponent because the optical thickness in the near-infrared wavelength region was large when the Ångström exponent was small. However, there was a case in which the Ångström exponent was large but the decrease in the ABL height was the largest of all the simulation results. In this case, the strong capping inversion due to the large extinction coefficient around the top of the ABL was an import factor. These results suggest that the vertical profiles of the aerosol physical and optical properties, and the resulting direct heating has important effects on the ABL evolution.

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Stabilization of the Atmospheric Boundary Layer and the Muted Global Hydrological Cycle Response to Global Warming

Journal of Hydrometeorology ◽

10.1175/2008jhm1058.1 ◽

2009 ◽

Vol 10 (1) ◽

pp. 347-352 ◽

Cited By ~ 23

Author(s):

Jianhua Lu ◽

Ming Cai

Keyword(s):

Boundary Layer ◽

Global Warming ◽

Atmospheric Boundary Layer ◽

Latent Heat ◽

Hydrological Cycle ◽

Sensible Heat Flux ◽

Bowen Ratio ◽

Heat Fluxes ◽

Global Ocean ◽

Global Hydrological Cycle

Abstract Both the global precipitation and evaporation in global warming simulations increase at 1%–3% K−1, much smaller than the rate suggested from the Clausius–Clapeyron (C–C) relation (6%–6.5% K−1). However, the reduction of surface sensible heat flux over the global ocean (5.2% K−1) matches the difference between the fractional increase of evaporation and the C–C relation, implying that the fractional decrease of the Bowen ratio over the global ocean follows the C–C relation closely. The analysis suggests that the stabilization of the atmospheric boundary layer (ABL) in response to global warming is the main factor responsible for the simultaneous reduction of the surface sensible flux and the muted increase in the surface latent heat. Because the stabilization of the ABL causes the same amount of fractional change in both the sensible and latent heat fluxes, the fractional decrease of the Bowen ratio closely follows the C–C relation. The ABL stabilization mechanism for the muted increase in the global hydrological cycle in response to global warming is physically consistent with two other proposed mechanisms, namely, the atmospheric energy constraint and the reduction of convective mass flux.

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

Journal of Physical Oceanography ◽

10.1175/jpo-d-18-0240.1 ◽

2019 ◽

Vol 49 (7) ◽

pp. 1927-1948 ◽

Cited By ~ 1

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.

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Vertical profiles of the structure characteristic of air temperature in the atmospheric boundary layer from sodar measurements

Оптика атмосферы и океана ◽

10.15372/aoo20160813 ◽

2016 ◽

Keyword(s):

Boundary Layer ◽

Atmospheric Boundary Layer ◽

Air Temperature ◽

Structure Characteristic ◽

Vertical Profiles ◽

Sodar Measurements

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Subcloud and Cloud-Base Latent Heat Fluxes during Shallow Cumulus Convection

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-19-0122.1 ◽

2019 ◽

Vol 77 (3) ◽

pp. 1081-1100 ◽

Cited By ~ 1

Author(s):

Neil P. Lareau

Keyword(s):

Boundary Layer ◽

Water Vapor ◽

Latent Heat ◽

Surface Fluxes ◽

Heat Fluxes ◽

Cloud Base ◽

Cumulus Convection ◽

Mixing Ratio ◽

Convective Boundary ◽

Water Vapor Mixing Ratio

Abstract Doppler and Raman lidar observations of vertical velocity and water vapor mixing ratio are used to probe the physics and statistics of subcloud and cloud-base latent heat fluxes during cumulus convection at the ARM Southern Great Plains (SGP) site in Oklahoma, United States. The statistical results show that latent heat fluxes increase with height from the surface up to ~0.8Zi (where Zi is the convective boundary layer depth) and then decrease to ~0 at Zi. Peak fluxes aloft exceeding 500 W m−2 are associated with periods of increased cumulus cloud cover and stronger jumps in the mean humidity profile. These entrainment fluxes are much larger than the surface fluxes, indicating substantial drying over the 0–0.8Zi layer accompanied by moistening aloft as the CBL deepens over the diurnal cycle. We also show that the boundary layer humidity budget is approximately closed by computing the flux divergence across the 0–0.8Zi layer. Composite subcloud velocity and water vapor anomalies show that clouds are linked to coherent updraft and moisture plumes. The moisture anomaly is Gaussian, most pronounced above 0.8Zi and systematically wider than the velocity anomaly, which has a narrow central updraft flanked by downdrafts. This size and shape disparity results in downdrafts characterized by a high water vapor mixing ratio and thus a broad joint probability density function (JPDF) of velocity and mixing ratio in the upper CBL. We also show that cloud-base latent heat fluxes can be both positive and negative and that the instantaneous positive fluxes can be very large (~10 000 W m−2). However, since cloud fraction tends to be small, the net impact of these fluxes remains modest.

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Study of the air-sea interactions at the mesoscale: the SEMAPHORE experiment

Annales Geophysicae ◽

10.1007/s00585-996-0986-6 ◽

1996 ◽

Vol 14 (9) ◽

pp. 986-1015 ◽

Cited By ~ 50

Author(s):

L. Eymard ◽

S. Planton ◽

P. Durand ◽

C. Le Visage ◽

P. Y. Le Traon ◽

...

Keyword(s):

Boundary Layer ◽

Atmospheric Boundary Layer ◽

Ocean Circulation ◽

Wave Model ◽

Heat Fluxes ◽

Sea Surface ◽

Upper Ocean ◽

Test Model ◽

Model Simulations ◽

Drifting Buoys

Abstract. The SEMAPHORE (Structure des Echanges Mer-Atmosphère, Propriétés des Hétérogénéités Océaniques: Recherche Expérimentale) experiment has been conducted from June to November 1993 in the Northeast Atlantic between the Azores and Madeira. It was centered on the study of the mesoscale ocean circulation and air-sea interactions. The experimental investigation was achieved at the mesoscale using moorings, floats, and ship hydrological survey, and at a smaller scale by one dedicated ship, two instrumented aircraft, and surface drifting buoys, for one and a half month in October-November (IOP: intense observing period). Observations from meteorological operational satellites as well as spaceborne microwave sensors were used in complement. The main studies undertaken concern the mesoscale ocean, the upper ocean, the atmospheric boundary layer, and the sea surface, and first results are presented for the various topics. From data analysis and model simulations, the main characteristics of the ocean circulation were deduced, showing the close relationship between the Azores front meander and the occurrence of Mediterranean water lenses (meddies), and the shift between the Azores current frontal signature at the surface and within the thermocline. Using drifting buoys and ship data in the upper ocean, the gap between the scales of the atmospheric forcing and the oceanic variability was made evident. A 2 °C decrease and a 40-m deepening of the mixed layer were measured within the IOP, associated with a heating loss of about 100 W m-2. This evolution was shown to be strongly connected to the occurrence of storms at the beginning and the end of October. Above the surface, turbulent measurements from ship and aircraft were analyzed across the surface thermal front, showing a 30% difference in heat fluxes between both sides during a 4-day period, and the respective contributions of the wind and the surface temperature were evaluated. The classical momentum flux bulk parameterization was found to fail in low wind and unstable conditions. Finally, the sea surface was investigated using airborne and satellite radars and wave buoys. A wave model, operationally used, was found to get better results compared with radar and wave-buoy measurements, when initialized using an improved wind field, obtained by assimilating satellite and buoy wind data in a meteorological model. A detailed analysis of a 2-day period showed that the swell component, propagating from a far source area, is underestimated in the wave model. A data base has been created, containing all experimental measurements. It will allow us to pursue the interpretation of observations and to test model simulations in the ocean, at the surface and in the atmospheric boundary layer, and to investigate the ocean-atmosphere coupling at the local and mesoscales.

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Soil Moisture-Boundary Layer Feedbacks on the Loess Plateau in China Using Radiosonde Data with 1-D Atmospheric Boundary Layer Model

Atmosphere ◽

10.3390/atmos12121619 ◽

2021 ◽

Vol 12 (12) ◽

pp. 1619

Author(s):

Yingsai Ma ◽

Xianhong Meng ◽

Yinhuan Ao ◽

Ye Yu ◽

Guangwei Li ◽

...

Keyword(s):

Boundary Layer ◽

Soil Moisture ◽

Atmospheric Boundary Layer ◽

Loess Plateau ◽

Atmospheric Stability ◽

Heat Fluxes ◽

Radiosonde Data ◽

Atmospheric Conditions ◽

The Loess Plateau ◽

The Impact

The Loess Plateau is one land-atmosphere coupling hotspot. Soil moisture has an influence on atmospheric boundary layer development under specific early-morning atmospheric thermodynamic structures. This paper investigates the sensitivity of atmospheric convection to soil moisture conditions over the Loess Plateau in China by using the convective triggering potential (CTP)—humidity index (HIlow) framework. The CTP indicates atmospheric stability and the HIlow indicates atmospheric humidity in the low-level atmosphere. By comparing the model outcomes with the observations, the one-dimensional model achieves realistic daily behavior of the radiation and surface heat fluxes and the mixed layer properties with appropriate modifications. New CTP-HIlow thresholds for soil moisture-atmosphere feedbacks are found in the Loess Plateau area. By applying the new thresholds with long-time scales sounding data, we conclude that negative feedback is dominant in the north and west portion of the Loess Plateau; positive feedback is predominant in the south and east portion. In general, this framework has predictive significance for the impact of soil moisture on precipitation. By using this new CTP-HIlow framework, we can determine under what atmospheric conditions soil moisture can affect the triggering of precipitation and under what atmospheric conditions soil moisture has no influence on the triggering of precipitation.

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Diagnosing Monthly Mean Boundary Layer Properties from Reanalysis Data Using a Bulk Boundary Layer Model

Journal of the Atmospheric Sciences ◽

10.1175/jas3669.1 ◽

2006 ◽

Vol 63 (3) ◽

pp. 998-1012 ◽

Cited By ~ 13

Author(s):

Maike Ahlgrimm ◽

David A. Randall

Keyword(s):

Boundary Layer ◽

Pacific Ocean ◽

Latent Heat ◽

Reanalysis Data ◽

Heat Fluxes ◽

South Pacific Convergence Zone ◽

Trade Wind ◽

Layer Model ◽

The West ◽

Boundary Layer Model

Abstract The mixed-layer approach to modeling the planetary boundary layer (PBL) is particularly well suited to inversion-topped PBLs, such as the stratocumulus-topped boundary layer found off the west coast of America in the subtropical Pacific Ocean at northern and southern latitudes. However, a strong temperature inversion near 850 hPa (the trade wind inversion) is not confined to the stratocumulus regimes, but has been observed over most parts of the subtropical–tropical Pacific Ocean. In this paper, the authors test the ability of a simple bulk boundary layer model (BBLM) to diagnose entrainment velocity, cumulus mass flux, and surface latent heat flux from monthly mean reanalysis data. The PBL depth is estimated from Geoscience Laser Altimeter System data. The model is based on the conservation equations for mass, total water mixing ratio, and moist static energy. The BBLM diagnoses entrainment velocities between 1 and 8 mm s−1 in the stratocumulus and trade wind regions, with increasing rates toward the west. Large cumulus mass fluxes (1.3–2 cm s−1) mark the ITCZ and South Pacific convergence zone. Unreasonably large surface latent heat fluxes are diagnosed in regions where the vertical resolution of both model and input data are insufficient to represent the sharp gradients of moist conservable variables and winds across the PBL top. The results demonstrate that the potential exists to extract useful information about the large-scale structure of PBL physical processes by combining available observations with simple models.

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Evaluation of Polar WRF from Modeling the Atmospheric Boundary Layer over Antarctic Sea Ice in Autumn and Winter

Monthly Weather Review ◽

10.1175/mwr-d-12-00016.1 ◽

2012 ◽

Vol 140 (12) ◽

pp. 3919-3935 ◽

Cited By ~ 25

Author(s):

Esa-Matti Tastula ◽

Timo Vihma ◽

Edgar L Andreas

Keyword(s):

Boundary Layer ◽

Sea Ice ◽

Surface Temperature ◽

Atmospheric Boundary Layer ◽

Inversion Layer ◽

Temperature Inversion ◽

Heat Fluxes ◽

Poor Correlation ◽

Antarctic Sea Ice ◽

Autumn And Winter

Abstract Regional simulations of the atmospheric boundary layer over Antarctic sea ice that have been adequately validated are rare. To address this gap, the authors use the doubly nested Polar Weather Research and Forecasting (Polar WRF) mesoscale model to simulate conditions during Ice Station Weddell (ISW) in the austral autumn and winter of 1992. The WRF simulations test two boundary layer schemes: Mellor–Yamada–Janjic and the Asymmetric Convective Model. Validation is against surface-layer and sounding observations from ISW. Simulated latent and sensible heat fluxes for both boundary layer schemes had poor correlation with the observed fluxes. Simulated surface temperature had better correlation with the observations, with a typical bias of 0–2 K and a root-mean-square error of 6–7 K. For surface temperature and wind speed, the Polar WRF yielded better results than the ECMWF Re-Analysis Interim (ERA-Interim). A more challenging test of the simulations is to reproduce features of the low-level jet and the temperature inversion, which were observed, respectively, in 80% and 96% of the ISW radiosoundings. Both boundary layer schemes produce only about half as many jets as were observed. Moreover, the simulated jet coincided with an observed jet only about 30% of the time. The number of temperature inversions and the height at the inversion base were better reproduced, although this was not the case with the depth of the inversion layer. Simulations of the temperature inversion improved when forecasts of cloud fraction agreed to within 0.3 with observations. The modeled inversions were strongest when the incoming longwave radiation was smallest, but this relationship was not observed at ISW.

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The vertical variability of black carbon observed in the atmospheric boundary layer during DACCIWA

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-7911-2020 ◽

2020 ◽

Vol 20 (13) ◽

pp. 7911-7928 ◽

Cited By ~ 2

Author(s):

Barbara Altstädter ◽

Konrad Deetz ◽

Bernhard Vogel ◽

Karmen Babić ◽

Cheikh Dione ◽

...

Keyword(s):

Boundary Layer ◽

Atmospheric Boundary Layer ◽

Black Carbon ◽

West African Monsoon ◽

Ground Level ◽

Cloud Base ◽

Small Scale ◽

Vertical Profiles ◽

Scale Modelling ◽

Reactive Trace Gases

Abstract. This study underlines the important role of the transported black carbon (BC) mass concentration in the West African monsoon (WAM) area. BC was measured with a micro-aethalometer integrated in the payload bay of the unmanned research aircraft ALADINA (Application of Light-weight Aircraft for Detecting IN situ Aerosol). As part of the DACCIWA (Dynamics–Aerosol–Chemistry–Cloud Interactions in West Africa) project, 53 measurement flights were carried out at Savè, Benin, on 2–16 July 2016. A high variability of BC (1.79 to 2.42±0.31 µg m−3) was calculated along 155 vertical profiles that were performed below cloud base in the atmospheric boundary layer (ABL). In contrast to initial expectations of primary emissions, the vertical distribution of BC was mainly influenced by the stratification of the ABL during the WAM season. The article focuses on an event (14 and 15 July 2016) which showed distinct layers of BC in the lowermost 900 m above ground level (a.g.l.). Low concentrations of NOx and CO were sampled at the Savè supersite near the aircraft measurements and suggested a marginal impact of local sources during the case study. The lack of primary BC emissions was verified by a comparison of the measured BC with the model COSMO-ART (Consortium for Small-scale Modelling–Aerosols and Reactive Trace gases) that was applied for the field campaign period. The modelled vertical profiles of BC led to the assumption that the measured BC was already altered, as the size was mainly dominated by the accumulation mode. Further, calculated vertical transects of wind speed and BC presume that the observed BC layer was transported from the south with maritime inflow but was mixed vertically after the onset of a nocturnal low-level jet at the measurement site. This report contributes to the scope of DACCIWA by linking airborne BC data with ground observations and a model, and it illustrates the importance of a more profound understanding of the interaction between BC and the ABL in the WAM region.

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