Evidence of Saharan mineral aerosols transport to the Mediterranean inside well-defined layers

Hamonou, Eric; Chazette, Patrick

doi:10.1016/s0021-8502(98)90814-x

Cited by 5 publications

(4 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Dust profiles were also documented by the lidar observations in PRIDE [ Colarco et al , 2003b], ACE‐2 [ Welton et al , 2000], and Surface of the Ocean, Fluxes and Interactions with the Atmosphere/Atlantic Stratocumulus Transition Experiment (SOFIA/ASTEX) [ Chazette et al , 1997]. Over the Mediterranean, field measurements reported that the stable Saharan layer was situated above the trade wind marine boundary layer [ Hamonou et al , 1997; Hamonou and Chazette , 1998; Pérez et al , 2006; Mattis et al , 2002; Müller et al , 2003; di Sarra et al , 2001].…”

Section: Climatological Resultsmentioning

confidence: 99%

Dust plumes over the Pacific, Indian, and Atlantic oceans: Climatology and radiative impact

Zhu¹,

Ramanathan²,

Li³

et al. 2007

J. Geophys. Res.

188

141

View full text Add to dashboard Cite

[1] Multiple satellite data sets in conjunction with the Monte Carlo Aerosol-CloudRadiation (MACR) model are employed to determine climatological distributions and radiative impacts of dust plumes over the Pacific, Indian, and Atlantic oceans. Three target regions, namely the Yellow Sea (YS), Arabian Sea (AS), and Saharan Coast (SC), are examined for quantitative comparisons of dust properties and their impacts on climate. Twenty year averaged Advanced Very High Resolution Radiometer (AVHRR) aerosol optical depth (AOD) data clearly show the peak dust season for the three target regions, March-April-May for YS and June-July-August for AS and SC. Georgia Institute of Technology-Goddard Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) modeled dust AOD fraction and Moderate Imaging Spectroradiometer (MODIS) large-mode AOD ratio are adopted to evaluate the dust fraction estimate. Stratospheric Aerosol and Gas Experiment (SAGE) II aerosol extinction coefficient data are used to define the vertical distribution of dust. The elevated dust plumes are detected by subtracting the non-dust-season values from dust season values of SAGE II data, showing extinction peak around $4 km over AS and SC. Over YS, dust plumes are found presenting multilayered structure. The shortwave (SW) forcing of dust, although moderated by the longwave (LW) effect, dominates the net effects (SW + LW) of dust plumes. Under clear-sky (i.e., cloudless) conditions, dust plumes reduce about 5.9 W m À2 , 17.8 W m À2 , and 14.2 W m À2 regional and seasonal mean radiative flux reaching the surface over YS, AS, and SC, respectively. Of the three regions, dust plumes over AS have the largest effect on atmospheric heating owing to a lower single-scattering albedo and the relatively large dust loading. The maximum SW heating occurs over AS with the value around +0.5 K/day inside the dust layer at $4 km. The LW effect results in strong cooling throughout the dust layer and moderate heating below the dust layer, and dust plumes over SC exert the maximum LW effect on heating rates, with up to À0.5 K/day LW cooling in the free troposphere and about +0.3 K/day warming in the boundary layer. As the sum of the SW and the LW heating rates, net heating rate shows a more complex pattern. Over SC, large LW cooling inside the dust layer offsets up to 80% SW heating and results in about À0.1 K/day net heating rate change at the height $5 km over SC. Over AS the net heating rate change is dominated by SW heating because the maximum LW cooling is less than 60% of the SW heating, which leads to +0.3 K/day net heating inside the dust layer and moderate heating below the dust base. The net heating rate change over YS is the smallest among the three regions, with magnitude within 0.1 K/day.

show abstract

Section: Climatological Resultsmentioning

confidence: 99%

Dust plumes over the Pacific, Indian, and Atlantic oceans: Climatology and radiative impact

Zhu¹,

Ramanathan²,

Li³

et al. 2007

J. Geophys. Res.

188

141

View full text Add to dashboard Cite

show abstract

“…The aerosol extinction coefficient vertical profile in our radiative transfer model varies exponentially with height [ Ricchiazzi et al , 1998]. However, it has been observed by lidar measurements [ Chazette et al , 1998; Hamomou and Chazette , 1998] and balloon‐borne scattering measurements [ Dulac and Chazette , 1998] that aerosols are often observed in complex multilayer structures. The Lidar In‐Space Technology Experiment also has shown that the Saharan dust layer is inhomogeneous and often characterized by several dust and cloud layers [ Winker et al , 1996].…”

Section: Sensitivity Analysismentioning

confidence: 99%

GOES 8 retrieval of dust aerosol optical thickness over the Atlantic Ocean during PRIDE

et al. 2003

View full text Add to dashboard Cite

[1] Using 30 days of half-hourly, high temporal resolution GOES 8 imager data and radiative transfer calculations, dust aerosol optical thickness (AOT) was retrieved over the Atlantic Ocean (14°N $ 26°N, 73°W-63°W) during the Puerto Rico Dust Experiment (PRIDE). Dust aerosol size distributions and complex index of refraction inferred from ground-based measurements (1.53-0.0015i at 0.55 mm), which were used in Mie calculations and a plane-parallel discrete ordinate radiative transfer model (DISORT) to compute look up tables for AOT retrievals. Using a combination of spectral, spatial, and temporal tests, a dust detection algorithm was developed from the GOES 8 imager data. The degradation of the signal response relative to the prelaunched calibration of the GOES 8 visible channel was 39% in July 2000 and the GOES 8 AOT detection limit was estimated to be 0.04 in AOT (0.67 mm). The satellite-retrieved AOT were then compared with AOT values derived from ground-based Sun photometer (SP) sites. The comparison showed that GOES 8 retrieved AOT are in good agreement with the SP derived values, with linear correlation coefficient of 0.91 and 0.80 for the two sites. The GOES 8 monthly mean 0.67 mm AOT (0.19 ± 0.13, 0.22 ± 0.12) over the two SP sites matched the monthly mean SP AOT values (0.23 ± 0.13, 0.22 ± 0.10). The linear correlation between the GOES 8 retrieved AOT and the aircraft derived values from particle probe data and airborne Sun photometer AATS-6 measurements were 0.88 and 0.83, respectively. Besides the uncertainties from the nonspherical effect of dust aerosols, sensitivity studies showed that the uncertainties (Át) of the GOES 8 retrieved AOT values were mainly from the uncertainties due to the imaginary part of refractive index (Át = ±0.05) and surface reflectance [Át = ±(0.02 $ 0.04)]. This paper demonstrates the application of geostationary satellites to detect and retrieve dust AOT even at low to moderate AOTs. The GOES 8 imager with high temporal resolutions also captures aerosol diurnal variation in this study that can further reduce the uncertainties in the current aerosol forcing estimations caused by the high temporal variations of AOT, thereby playing a complementary role with global AOT retrievals from polar orbiting satellites.

show abstract

“… techniques in microwaves (measure the intensity and polarization of the centimetres waves, between 0.1 to 100 cm) Table A1.2: The electromagnetic spectrum with wavelengths. In case of the solar spectrum (visible) we have: Meteosat (Paronis et al, 1998;Hamanou et al, 1998;Dulac et al, 2001;Ourtirane et al, 2002), NOAA (Dammann et al, 2002;Flores et al, 2002;Takeuchi et al, 2003). In case of the infrared: Meteosat (Ourtirane et al, 2002;Noyes et al, 2002;Dash et al, 2003), NOAA (Göttsche et al, 2002;Wang et al, 2002;Morales et al, 2002;Iino et al, 2004).…”

Section: Basic Review Of Remote Sensingmentioning

confidence: 99%

“…were realized. In case of the geostationary satellites we have: Meteosat (Paronis et al, 1998;Hamanou et al, 1998;Dulac et al, 2001, Ourtirane et al, 2002.…”

Section: A111 Satellite Typementioning

confidence: 99%

Turbulent structure in environmental flows: effects of stratification and rotation

Matulka

View full text Add to dashboard Cite

Several series of experiments in stratified and in rotating/stratified decaying flows after a grid is used to stir the two layer stable fluid brine and fresh water set up. We measure by comparing the gained potential energy with the available kinetic energy AKE, the relative efficiency of mixing. The experiments in stratified rotating flows with grid driven turbulence were both periodic (quasi stationary) and non-monotonic (decaying) forcing. This thesis compares experimental, numerical and field observations on the structure and Topology of the Stratified Rotating Flows as well as their decay, the horizontal spectra changes appreciable with slopes from 1.1 to 5, but vorticity and local circulation, and also the initial topology and forcing of the flow. A detailed study of the vorticity decay and vortex and energy structure has been performed, the new results show that neither stratified nor rotating flows exhibit pure 2D structures. The work parameterizes the role of the Richardson number and the Rossby number, both in the experiments and in the ocean visualizations is very important. The conditions of vortex decay show the effects of the internal waves in the decay turbulent conditions both for stratified and rotating flows. The parameter space (Re,Ri,Ro) has been used to interpret many previously disconnected explanations of the 2D-3D turbulent behaviour. The comparison of numerical simulations with experiments has allowed implementing new theoretical aspects of the interaction between waves and vortices finding the surprising and very interesting result that these interactions depend on the level of enstrophy. This also leads to new ways of using multifractal analysis ad intermittency in ocean environmental observations. A large collection of SAR images obtained from three European coastal areas were used for routine satellite analysis by SAR and other sensors, which seem very important to build seasonal databases of the dynamic conditions of ocean mixing. The topology of the basic flow is very important and in particular the topology of the vortices and their decay which depends on ambient factors such as wave activity, wind and currents. We find more realistic estimates of the spatial/temporal non-homogeneities (and intermittency obtained as spatial correlations of the turbulent dissipation); these values are used to parameterize the sea surface turbulence, as well as a laboratory experiments at a variety of scales. Using multi-fractal geometry as well, we can establish now a theoretical pattern for the turbulence behaviour that is reflected in the different descriptors. Vorticity evolution is smoother and different than that of scalar or tracer density. The correlation between the local Ri and the fractal dimension detected from energy or entropy is good. Using multi-fractal geometry we can also establish certain regions of higher local activity used to establish the geometry of the turbulence mixing that needs to be studied in detail when interpreting the complex balance between the direct 3D Kolmogorov type cascade and the Inverse 2D Kraichnan type cascade.

show abstract

Evidence of Saharan mineral aerosols transport to the Mediterranean inside well-defined layers

Cited by 5 publications

References 6 publications

Dust plumes over the Pacific, Indian, and Atlantic oceans: Climatology and radiative impact

Dust plumes over the Pacific, Indian, and Atlantic oceans: Climatology and radiative impact

GOES 8 retrieval of dust aerosol optical thickness over the Atlantic Ocean during PRIDE

Turbulent structure in environmental flows: effects of stratification and rotation

Contact Info

Product

Resources

About