scholarly journals Estimating a relationship between aerosol optical thickness and surface wind speed over the ocean

2006 ◽  
Vol 6 (6) ◽  
pp. 11621-11651 ◽  
Author(s):  
P. Glantz ◽  
D. E. Nilsson ◽  
W. von Hoyningen-Huene
Keyword(s):  
Wind Speed ◽  
Optical Thickness ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Sea Salt ◽  
Aerosol Optical Thickness ◽  
Marine Aerosols ◽  
Hygroscopic Growth ◽  
The North ◽  
The North Pacific

Abstract. Retrieved aerosol optical thickness (AOT) based on data obtained by the Sea viewing Wide Field Sensor (SeaWiFS) is combined with surface wind speed, obtained at the European Centre for Medium-Range Weather Forecasts (ECMWFs), over the North Pacific for September 2001. In this study a cloud screening approach is introduced in an attempt to exclude pixels partly or fully covered by clouds. The relatively broad swath width for which the nadir looking SeaWiFS instrument scanned over the North Pacific means that the AOT can be estimated according to relatively large range of wind speeds for each of the scenes analyzed. The sensitivity in AOT due to sea salt and hygroscopic growth of the marine aerosols has also been investigated. The validation of the results is based on previous parameterization in combination with the environmental quantities wind speed, RH and boundary layer height (BLH), estimated at the ECMWF. In this study a factor of 2 higher mean AOT is obtained for a wind speed up to about 13 m s−1 for September 2001 over remote ocean areas. Furthermore, a factor of 2 higher AOT is more or less supported by the validation of the results. Approximately, 50% of the enhancement seems to be due to hygroscopic growth of the marine aerosols and the remaining part due to increase in the sea salt particle mass concentrations, caused by a wind driven water vapor and sea salt flux, respectively. Reasonable agreement occurs also between satellites retrieved aerosol optical thickness and AOT observed at several AERONET (Aerosol Robotic NETwork) ground-based remote sensing stations. Finally, possible reasons why relatively large standard deviations occur around the mean values of AOT estimated for a single scene are discussed.

scholarly journals Deriving the effect of wind speed on clean maritime aerosol optical properties using the A-Train satellites

2011 ◽  
Vol 11 (2) ◽  
pp. 4599-4630 ◽  
Author(s):  
V. P. Kiliyanpilakkil ◽  
N. Meskhidze
Keyword(s):  
Optical Properties ◽  
Wind Speed ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Sea Salt ◽  
Marine Aerosol ◽  
Marine Aerosols ◽  
Aerosol Optical Properties ◽  
The Mean ◽  
532 Nm

Abstract. Relationship between "clean marine" aerosol optical properties and ocean surface wind speed is explored using remotely sensed data from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) on board the CALIPSO satellite and the Advanced Microwave Scanning Radiometer (AMSR-E) on board the AQUA satellite. Detailed data analyses are carried out over 15 regions selected to be representative of different areas of the global ocean for the time period from June 2006 to June 2010. Based on remotely sensed optical properties the CALIPSO algorithm is capable of discriminating "clean marine" aerosols from other types often present over the ocean (such as urban/industrial pollution, desert dust and biomass burning). The global mean optical depth of "clean marine" aerosol at 532 nm (AOD532) is found to be 0.052 ± 0.038. The mean layer integrated volume depolarization ratio of marine aerosols is 0.016 ± 0.012, the value representative of sea salt crystals. Integrated attenuated backscatter and color ratio of marine aerosols at 532 nm were obtained to be 0.003 ± 0.002 sr−1 and 0.530 ± 0.149, respectively. A logistic regression between AOD532 and 10-meter surface wind speed (U10) revealed three distinct regions. For surface winds lower than 4 m s−1, the mean CALIPSO-derived AOD532 is found to be 0.02 ± 0.003 with little dependency on the surface wind speed. For surface winds from 4 m s−1 to 12 m s−1, representing the dominant fraction of all available data, marine aerosol optical depth is linearly correlated with the U10, with a slope of 0.0062 s m−1. In this intermediate wind speed region, the AOD532 vs. U10 regression derived here is comparable to previously reported relationships. At very high wind speed values (U10 > 18 m s−1), the AOD532-wind speed relationship showed a tendency toward leveling off, suggesting the existence of some maximum value for maritime AOD. Results of our calculations suggest that considerable improvements to both optical properties of marine aerosols and their production mechanisms can be achieved by discriminating "clean marine" aerosols (or sea salt particles) from all other types of aerosols present over the ocean.

scholarly journals Regional Dependence of Atmospheric Responses to Oceanic Eddies in the North Pacific Ocean

2020 ◽  
Vol 12 (7) ◽  
pp. 1161 ◽  
Author(s):  
Jinlin Ji ◽  
Jing Ma ◽  
Changming Dong ◽  
John Chiang ◽  
Dake Chen
Keyword(s):  
Wind Speed ◽  
Pacific Ocean ◽  
North Pacific ◽  
North Pacific Ocean ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Sea Surface ◽  
The North ◽  
Oceanic Eddies ◽  
The North Pacific

Based on sea surface height anomaly (SSHA) from satellite altimeter and microwave radiometer datasets, this study investigates atmospheric responses to oceanic eddies in four subdomains of the North Pacific Ocean with strongest eddy activity: Kuroshio Extension (KE), Subtropical Front (SF), California Coastal Current (CC) and Aleutian Islands (AI). Analyses show that anticyclonic eddies cause sea surface temperature, surface wind speed and precipitation rate to increase in all four subdomains, and vice versa. Through a further examination of the regional dependence of atmospheric responses to oceanic eddies, it is found that the strongest and the weakest surface wind speed responses (in winter and summer) are observed in the KE and AI region, respectively. For precipitation rate, seasonal variation of the atmospheric responses to oceanic eddies is strongest in winter and weakest in summer in the KE, CC and AI regions, but stronger in summer in the SF area. The reasons for such regional dependence and seasonality are the differences in the strength of SST anomalies, the vertical kinetic energy flux and atmospheric instability in the four subdomains.

scholarly journals Effects of Sea-Salt Aerosols on Precipitation in Simulations of Shallow Cumulus

2012 ◽  
Vol 69 (2) ◽  
pp. 463-483 ◽  
Author(s):  
Yefim L. Kogan ◽  
David B. Mechem ◽  
Kityan Choi
Keyword(s):  
Wind Speed ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Sea Salt ◽  
Negative Slope ◽  
Cloud Base ◽  
Precipitation Process ◽  
Sea Salt Aerosols ◽  
Rain Drops ◽  
Microphysical Processes

Abstract A suite of large-eddy simulations with size-resolving microphysical processes was performed in order to assess effects of sea-salt aerosols on precipitation process in trade cumulus. Simulations based on observations from the Rain in Cumulus over the Ocean (RICO) field campaign explored the effects of adding sea-salt nuclei in different size ranges by following the evolution of 369 cloud cells over the 24-h simulation period. The addition of large (small) sea-salt nuclei tends to accelerate (suppress) precipitation formation; however, in marine environments the sea-salt spectra always include a combination of both small (film) and large (jet) nuclei. When realistic sea-salt spectra are specified as a function of surface wind, the effect of the larger nuclei to enhance the precipitation predominates, and accumulated precipitation increases with wind speed. This effect, however, is strongly influenced by the choice of background CCN spectrum. Adding the same sea-salt specification to an environment with a higher background aerosol load results in a decrease in accumulated precipitation with increasing surface wind speed. Results also suggest that the slope of the relationship between vertical velocity W and the concentration of embryonic precipitation particles at cloud base Nr may indicate the role of sea-salt nuclei. A negative slope (Nr decreasing with increasing W) points to the predominance of small sea-salt nuclei, in which larger updrafts activate a greater number of smaller cloud drops with smaller coalescence efficiencies, resulting in fewer embryonic rain drops. A positive slope, on the other hand, indicates the presence of large sea-salt nuclei, which are the source of embryonic rain drops.

scholarly journals Evaluation of Extratropical Cyclone Precipitation in the North Atlantic Basin: An Analysis of ERA-Interim, WRF, and Two CMIP5 Models

2018 ◽  
Vol 31 (6) ◽  
pp. 2345-2360 ◽  
Author(s):  
James F. Booth ◽  
Catherine M. Naud ◽  
Jeff Willison
Keyword(s):  
Wind Speed ◽  
North Atlantic ◽  
Surface Wind ◽  
Wrf Model ◽  
Surface Wind Speed ◽  
Convective Precipitation ◽  
Cmip5 Models ◽  
Convection Scheme ◽  
The North ◽  
The North Atlantic

The representation of extratropical cyclone (ETC) precipitation in general circulation models (GCMs) and the Weather Research and Forecasting (WRF) Model is analyzed. This work considers the link between ETC precipitation and dynamical strength and tests if parameterized convection affects this link for ETCs in the North Atlantic basin. Lagrangian cyclone tracks of ETCs in ERA-Interim (ERAI), GISS and GFDL CMIP5 models, and WRF with two horizontal resolutions are utilized in a compositing analysis. The 20-km-resolution WRF Model generates stronger ETCs based on surface wind speed and cyclone precipitation. The GCMs and ERAI generate similar composite means and distributions for cyclone precipitation rates, but GCMs generate weaker cyclone surface winds than ERAI. The amount of cyclone precipitation generated by the convection scheme differs significantly across the datasets, with the GISS model generating the most, followed by ERAI and then the GFDL model. The models and reanalysis generate relatively more parameterized convective precipitation when the total cyclone-averaged precipitation is smaller. This is partially due to the contribution of parameterized convective precipitation occurring more often late in the ETC’s life cycle. For reanalysis and models, precipitation increases with both cyclone moisture and surface wind speed, and this is true if the contribution from the parameterized convection scheme is larger or not. This work shows that these different models generate similar total ETC precipitation despite large differences in the parameterized convection, and these differences do not cause unexpected behavior in ETC precipitation sensitivity to cyclone moisture or surface wind speed.

scholarly journals Deriving the effect of wind speed on clean marine aerosol optical properties using the A-Train satellites

2011 ◽  
Vol 11 (22) ◽  
pp. 11401-11413 ◽  
Author(s):  
V. P. Kiliyanpilakkil ◽  
N. Meskhidze
Keyword(s):  
Optical Properties ◽  
Wind Speed ◽  
Optical Depth ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Marine Aerosol ◽  
Marine Aerosols ◽  
Aerosol Optical Properties ◽  
The Mean ◽  
532 Nm

Abstract. The relationship between "clean marine" aerosol optical properties and ocean surface wind speed is explored using remotely sensed data from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) on board the CALIPSO satellite and the Advanced Microwave Scanning Radiometer (AMSR-E) on board the AQUA satellite. Detailed data analyses are carried out over 15 regions selected to be representative of different areas of the global ocean for the time period from June 2006 to April 2011. Based on remotely sensed optical properties the CALIPSO algorithm is capable of discriminating "clean marine" aerosols from other types often present over the ocean (such as urban/industrial pollution, desert dust and biomass burning). The global mean optical depth of "clean marine" aerosol at 532 nm (AOD532) is found to be 0.052 ± 0.038 (mean plus or minus standard deviation). The mean layer integrated particulate depolarization ratio of marine aerosols is 0.02 ± 0.016. Integrated attenuated backscatter and color ratio of marine aerosols at 532 nm were found to be 0.003 ± 0.002 sr−1 and 0.530 ± 0.149, respectively. A logistic regression between AOD532 and 10-m surface wind speed (U10) revealed three distinct regimes. For U10 ≤ 4 m s−1 the mean CALIPSO-derived AOD532 is found to be 0.02 ± 0.003 with little dependency on the surface wind speed. For 4 < U10 ≤ 12 m s−1, representing the dominant fraction of all available data, marine aerosol optical depth is linearly correlated with the surface wind speed values, with a slope of 0.006 s m−1. In this intermediate wind speed region, the AOD532 vs. U10 regression slope derived here is comparable to previously reported values. At very high wind speed values (U10 > 18 m s−1), the AOD532-wind speed relationship showed a tendency toward leveling off, asymptotically approaching value of 0.15. The conclusions of this study regarding the aerosol extinction vs. wind speed relationship may have been influenced by the constant lidar ratio used for CALIPSO-derived AOD532. Nevertheless, active satellite sensor used in this study that allows separation of maritime wind induced component of AOD from the total AOD over the ocean could lead to improvements in optical properties of sea spray aerosols and their production mechanisms.

scholarly journals Evaluation and Projection of Wind Speed in the Arid Region of Northwest China Based on CMIP6

2021 ◽  
Vol 13 (20) ◽  
pp. 4076
Author(s):  
Yunxia Long ◽  
Changchun Xu ◽  
Fang Liu ◽  
Yongchang Liu ◽  
Gang Yin
Keyword(s):  
Wind Speed ◽  
Arid Region ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Northwest China ◽  
Tianshan Mountains ◽  
Model Ensemble ◽  
The West ◽  
The North ◽  
Temporal And Spatial

Near surface wind speed has significant impacts on ecological environment change and climate change. Based on the CN05.1 observation data (a gridded monthly dataset with the resolution of 0.25 latitude by 0.25 longitude over China), this study evaluated the ability of 25 Global Climate Models (GCMs) from Coupled Model Intercomparison Project phase 6 (CMIP6) in simulating the wind speed in the Arid Region of Northwest China (ARNC) during 1971–2014. Then, the temporal and spatial variations in the surface wind speed of ARNC in the 21st century were projected under four Shared Socioeconomic Pathways (SSPs), SSP1-2.6, SSP2-4.5, SSP3-7.0, and SP5-8.5. The results reveal that the preferred-model ensemble (PME) can fairly evaluate the temporal and spatial distribution of surface wind speed with the temporal and spatial correlation coefficients exceeding 0.5 at the significance level of p = 0.05 when compared to the 25 single models and their ensemble mean. After deviation correction, the PME can reproduce the distribution characteristics of high wind speed in the east and low in the west, high in mountainous areas, and low in basins. Unfortunately, no models or model ensemble can accurately reproduce the decreasing magnitude of observed wind speed. In the 21st century, the surface wind speed in the ARNC is projected to increase under SSP1-2.6 scenario but will decrease remarkably under the other three scenarios. Moreover, the higher the emission scenarios, the more significant the surface wind speed decreases. Spatially, the wind speed will increase significantly in the west and southeast of Xinjiang, decrease in the north of Xinjiang and the south of Tarim Basin. What’s more, under the four scenarios, the surface wind speed will decrease in spring, summer and autumn, especially in summer, and increase in winter. The wind speed will decrease significantly in the north of Tianshan Mountains in summer, decrease significantly in the north of Xinjiang and the southern edge of Tarim Basin in spring and autumn, and increase in fluctuation with high values in Tianshan Mountains in winter.

scholarly journals Quantifying the impact of sub-grid surface wind variability on sea salt and dust emissions in CAM5

2015 ◽  
Vol 8 (8) ◽  
pp. 7249-7312
Author(s):  
K. Zhang ◽  
C. Zhao ◽  
H. Wan ◽  
Y. Qian ◽  
R. C. Easter ◽  
...  
Keyword(s):  
Wind Speed ◽  
Surface Wind ◽  
Dust Emission ◽  
Surface Wind Speed ◽  
Sea Salt ◽  
Dust Emissions ◽  
Wind Variability ◽  
Wind Events ◽  
The Impact ◽  
Meso Scale

Abstract. This paper evaluates the impact of sub-grid variability of surface wind on sea salt and dust emissions in the Community Atmosphere Model version 5 (CAM5). The basic strategy is to calculate emission fluxes multiple times, using different wind speed samples of a Weibull probability distribution derived from model-predicted grid-box mean quantities. In order to derive the Weibull distribution, the sub-grid standard deviation of surface wind speed is estimated by taking into account four mechanisms: turbulence under neutral and stable conditions, dry convective eddies, moist convective eddies over the ocean, and air motions induced by meso-scale systems and fine-scale topography over land. The contributions of turbulence and dry convective eddy are parameterized using schemes from the literature, while the wind variabilities caused by moist convective eddies and fine-scale topography are estimated using empirical relationships derived from an operational weather analysis dataset at 15 km resolution. The estimated sub-grid standard deviations of surface wind speed agree well with reference results derived from one year of global weather analysis at 15 km resolution and from two regional model simulations with 3 km grid spacing. The wind-distribution-based emission calculations are implemented in CAM5. Simulations at 2° resolution indicate that sub-grid wind variability has relatively small impacts (about 7 % increase) on the global annual mean emission of sea salt aerosols, but considerable influence on the emission of dust. Among the considered mechanisms, dry convective eddies and meso-scale flows associated with topography are major causes of dust emission enhancement. With all the four mechanisms included and without additional adjustment of uncertain parameters in the model, the simulated global and annual mean dust emission increase by about 50 % compared to the default model. By tuning the globally constant dust emission scale factor, the global annual mean dust emission, aerosol optical depth, and top-of-atmosphere radiative fluxes can be adjusted to the level of the default model, but the frequency distribution of dust emission changes, with more contribution from weaker wind events and less contribution from stronger wind events.

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