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Markowicz, KM, Flatau PJ, Ramana MV, Crutzen PJ, Ramanathan V.  2002.  Absorbing mediterranean aerosols lead to a large reduction in the solar radiation at the surface. Geophysical Research Letters. 29   10.1029/2002gl015767   AbstractWebsite

[1] We present direct radiometric observations of aerosol radiative forcing taken during the MINOS experiment (2001) at Finokalia Sampling Station located on North-Eastern shores of Crete, Greece. The mean value of aerosol optical thickness was 0.21 at 500 nm. Aerosols, mostly of anthropogenic origin, lead to a diurnal average reduction of 17.9 W m(-2) in the surface solar radiation, an increase of 11.3 W m(-2) in the atmospheric solar absorption, and an increase of 6.6 W m(-2) in the reflected solar radiation at the top-of-the atmosphere. Thus, the present data gives observational proof for the large role of absorbing aerosols in the Mediterranean. The negative surface forcing and large positive atmospheric forcing values observed for the Mediterranean aerosols is nearly identical to the highly absorbing south Asian haze observed over the Arabian Sea.

Wells, KC, Witek M, Flatau P, Kreidenwei SM, Westphal DL.  2007.  An analysis of seasonal surface dust aerosol concentrations in the western US (2001-2004): Observations and model predictions. Atmospheric Environment. 41:6585-6597.   10.1016/j.atmosenv.2007.04.034   AbstractWebsite

Long-term surface observations indicate that soil dust represents over 30% of the annual fine (particle diameter less than 2.5 mu m) particulate mass in many areas of the western US; in spring and summer, it represents an even larger fraction. There are numerous dust-producing playas in the western US, but surface dust aerosol concentrations in this region are also influenced by dust of Asian origin. This study examines the seasonality of surface soil dust concentrations at 15 western US sites using observations from the Interagency Monitoring of PROtected Visual Environments (IMPROVE) network from 2001 to 2004. Average soil concentrations in particulate matter less than 10 mu m in diameter (PM 10) were lowest in winter and peaked during the summer months at these sites; however, episodic higher-concentration events (> 10 mu g m(-3)) occurred in the spring, the time of maximum Asian dust transport to the western US. Simulated surface dust concentrations from the Navy Aerosol Analysis and Prediction System (NAAPS) suggested that long-range transport from Asia dominates surface dust concentrations in the western US in the spring, and that, although some long-range transport does occur throughout the year (1-2 mu g m(-3)), locally generated dust plays a larger role in the region in summer and fall. However, NAAPS simulated some anomalously high concentrations (> 50 mu g m(-3)) of local dust in the fall and winter months over portions of the western US. Differences between modeled and observed dust concentrations were attributed to overestimation of total observed soil dust concentrations by the assumptions used to convert IMPROVE measurements into PM(10) soil concentrations, lack of inhibition of model dust production in snow-covered regions, and lack of seasonal agricultural sources in the model. (c) 2007 Elsevier Ltd. All rights reserved.

Verlinde, J, Flatau PJ, Cotton WR.  1990.  Analytical Solutions to the Collection Growth Equation - Comparison with Approximate Methods and Application to Cloud Microphysics Parameterization Schemes. Journal of the Atmospheric Sciences. 47:2871-2880.   10.1175/1520-0469(1990)047<2871:asttcg>2.0.co;2   AbstractWebsite

A closed form solution for the collection growth equation as used in bulk microphysical parameterizations is derived. Although the general form is mathematically complex, it can serve as a benchmark for testing a variety of approximations. Two special cases that can immediately be implemented in existing cloud models are also presented. This solution is used to evaluate two commonly used approximations. The effect of the selection of different basis functions is also investigated.

Goodman, JJ, Draine BT, Flatau PJ.  1991.  Application of Fast-Fourier-Transform Techniques to the Discrete-Dipole Approximation. Optics Letters. 16:1198-1200.   10.1364/ol.16.001198   AbstractWebsite

We show how fast-Fourier-transform methods can be used to accelerate computations of scattering and absorption by particles of arbitrary shape using the discrete-dipole approximation.

Flatau, PJ, Pielke RA, Cotton WR.  1988.  Application of symbolic algebra to the generation of coordinate transformations . Environmental Software. 3:158-160. Abstract

In this paper we present tools for automatic generation of generalized (variable and terrain-following) coordinate transformations and its use in numerical models of atmospheric flows. Such methodology should be competitive with the more cornraonly employed nested grid schemes. We discuss the symbolic (computer) algebra program for analytical calculation of Christoffel symbols, metric tensor and other geometrical objects describing a transformation. An example, related to the numerical modeling of mesoscale flows, is given. This example shows how coupled terrain-following m~d stretching transformation can be easily created. The possible application of such methodology in numerical modeling of air pollution on cirrus clouds is briefly discussed.

Flatau, PJ, Piskozub J, Zaneveld JRV.  1999.  Asymptotic light field in the presence of a bubble-layer. Optics Express. 5:120-124.   10.1364/OE.5.000120   AbstractWebsite

We report that the submerged microbubbles are an efficient source of diffuse radiance and may contribute to a rapid transition to the diffuse asymptotic regime. In this asymptotic regime an average cosine is easily predictable and measurable. (C) 1999 Optical Society of America.

Valero, FPJ, Bucholtz A, Bush BC, Pope SK, Collins WD, Flatau P, Strawa A, Gore WJY.  1997.  Atmospheric Radiation Measurements Enhanced Shortwave Experiment (ARESE): Experimental and data details. Journal of Geophysical Research-Atmospheres. 102:29929-29937.   10.1029/97jd02434   AbstractWebsite

Atmospheric Radiation Measurements Enhanced Shortwave Experiment (ARESE) was conducted to study the magnitude and spectral characteristics of the absorption Of solar radiation by the clear and cloudy atmosphere. Three aircraft platforms, a Grob Egrett, a NASA ER-2, and a Twin Otter, were used during ARESE in conjunction with the Atmospheric Radiation Measurements (ARM) central and extended facilities in north central Oklahoma. The aircraft were coordinated to simultaneously measure solar irradiances in the total spectral broadband (0.224-3.91 mu m), near infrared broadband (0.678-3.3 mu m), and in seven narrow band-pass (similar to 10 nm width) channels centered at 0.500, 0.862, 1.064, 1.249, 1.501, 1.651, and 1.750 mu m. Instrumental calibration issues are discussed in some detail, in particular radiometric power, angular, and spectral responses. The data discussed in this paper are available at the ARM ARESE data archive via anonymous FTP to ftp.arm.gov.

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Markowicz, KM, Flatau PJ, Kardas AE, Remiszewska J, Stelmaszczyk K, Woeste L.  2008.  Ceilometer retrieval of the boundary layer vertical aerosol extinction structure. Journal of Atmospheric and Oceanic Technology. 25:928-944.   10.1175/2007jtecha1016.1   AbstractWebsite

The CT25K ceilometer is a general-purpose cloud height sensor employing lidar technology for detection of clouds. In this paper it is shown that it can also be used to retrieve aerosol optical properties in the boundary layer. The authors present a comparison of the CT25K instrument with the aerosol lidar system and discuss its good overall agreement for both the range-corrected signals and the retrieved extinction coefficient profiles. The CT25K aerosol profiling is mostly limited to the boundary layer, but it is capable of detecting events in the lower atmosphere such as mineral dust events between 1 and 3 km. Assumptions needed for the estimation of the aerosol extinction profiles are discussed. It is shown that, when a significant part of the aerosol layer is in the boundary layer, knowledge of the aerosol optical depth from a sun photometer allows inversion of the lidar signal. In other cases, surface observations of the aerosol optical properties are used. It is demonstrated that additional information from a nephelometer and aethalometer allows definition of the lidar ratio. Extinction retrievals based on spherical and randomly oriented spheroid assumptions are performed. It is shown, by comparison with the field measurements during the United Arab Emirates Unified Aerosol Experiment, that an assumption about specific particle shape is important for the extinction profile inversions. The authors indicate that this limitation of detection is a result of the relatively small sensitivity of this instrument in comparison to more sophisticated aerosol lidars. However, in many cases this does not play a significant role because globally only about 20% of the aerosol optical depth is above the boundary layer.

Markowicz, KM, Flatau PJ, Vogelmann AM, Quinn PK, Welton EJ.  2003.  Clear-sky infrared aerosol radiative forcing at the surface and the top of the atmosphere. Quarterly Journal of the Royal Meteorological Society. 129:2927-2947.   10.1256/qj.02.224   AbstractWebsite

We study the aerosol radiative forcing at infrared (IR) wavelengths using data from the Aerosol Characterization Experiment. ACE-Asia, cruise of the National Oceanic and Atmospheric Administration research vessel Ronald H. Brown. The analyses apply to the daytime periods of clear-sky conditions for the area within the immediate vicinity of the ship. An optical model is derived from chemical measurements, lidar profiles, and visible-extinction measurements, which are used to estimate the IR aerosol optical thickness and the single-scattering albedo. The IR model results are compared to detailed Fourier transform interferometer-based IR aerosol forcing estimates, pyrgeometer-based IR downward fluxes, and to observations of the direct aerosol solar forcing. This combined approach attests to the self-consistency of the optical model, and allows us to derive quantities such as the IR forcing at the top of the atmosphere (TOA) and the IR optical thickness. The mean IR aerosol optical thickness at 10 mum is 0.08 and the single-scattering albedo is 0.55. The modelled IR aerosol surface forcing reaches 10 W m(-2) during the cruise, which is a significant contribution compared to the total direct aerosol forcing. The surface IR aerosol radiative forcing is between 10 and 25% of the short-wave aerosol forcing. The IR aerosol forcing at the TOA can be up to 19% of the solar aerosol forcing. We show good agreement between TOA aerosol IR forcing derived from the model and from the CERES (Clouds and the Earth's Radiant Energy System) satellite data. Over the Sea of Japan, the average IR aerosol radiative forcing is 4.6 W m(-2) at the surface. and 1.5 W m(-2) at the TOA. The IR forcing efficiency at the TOA is a strong function of aerosol temperature (which is coupled to vertical structure) and changes between 10 and 18 W m(-2) (per IR optical depth unit), while the surface IR forcing efficiency varies between 37 and 55 W m(-2) (per IR optical depth unit).

Schmidt, JM, Flatau PJ, Yates RD.  2014.  Convective cells in altocumulus observed with a high-resolution radar. Journal of the Atmospheric Sciences. 71:2130-2154.   10.1175/jas-d-13-0172.1   AbstractWebsite

Very-high-resolution Doppler radar observations are used together with aircraft measurements to document the dynamic and thermodynamic structure of a dissipating altocumulus cloud system associated with a deep virga layer. The cloud layer circulation is shown to consist of shallow vertical velocity couplets near cloud top and a series of subkilometer-scale Rayleigh-Benard-like cells that extend vertically through the depth of the cloud layer. The subcloud layer was observed to contain a number of narrow virga fall streaks that developed below the more dominant Rayleigh-Benard updraft circulations in the cloud layer. These features were discovered to be associated with kilometer-scale horizontally orientated rotor circulations that formed along the lateral flanks of the streaks collocated downdraft circulation. The Doppler analysis further reveals that a layer mean descent was present throughout both the cloud and subcloud layers. This characteristic of the circulation is analyzed with regard to the diabatic and radiative forcing on horizontal length scales ranging from the Rayleigh-Benard circulations to the overall cloud layer width. In particular, linear analytical results indicate that a deep and broad mesoscale region of subsidence is quickly established in middle-level cloud layers of finite width when a layer-wide horizontal gradient in the cloud-top radiative cooling rate is present. A conceptual model summarizing the primary observed and inferred circulation features of the altocumulus layer is presented.

Witek, ML, Flatau PJ, Teixeira J, Westphal DL.  2007.  Coupling an ocean wave model with a global aerosol transport model: A sea salt aerosol parameterization perspective. Geophysical Research Letters. 34   10.1029/2007gl030106   AbstractWebsite

[1] A new approach to sea salt parameterization is proposed which incorporates wind- wave characteristics into the sea salt emission function and can be employed globally and under swell- influenced conditions. The new source function was applied into Navy Aerosol Analysis and Prediction System model together with predictions from the global wave model Wave Watch III. The squared surface wind velocity U-10 and the wave's orbital velocity V-orb= pi H-s/ T-P are shown to be the key parameters in the proposed parameterization. Results of the model simulations are validated against multi- campaign shipboard measurements of the sea salt aerosol. The validations indicate a good correlation between V-orb and the measured surface concentrations. The model simulations with the new parameterization exhibit an improved agreement with the observations when compared to a wind- speed- only approach. The proposed emission parameterization has the potential to improve the simulations of sea salt emission in aerosol transport models.

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Flatau, MK, Flatau PJ, Schmidt J, Kiladis GN.  2003.  Delayed onset of the 2002 Indian monsoon. Geophysical Research Letters. 30   10.1029/2003gl017434   AbstractWebsite

[1] We show that there is a set of dynamical predictors, which facilitate forecasting of a delayed monsoon onset. The main dynamical contributor is the early May propagation of the "bogus onset Intraseasonal Oscillation'' which triggers a set of events precluding the climatological monsoon onset. We analyze in detail the 2002 monsoon onset and show that it followed a pattern described in our previous study. We notice that the 2003 monsoon onset followed very similar pattern and was delayed.

Collins, WD, Bucholtz A, Flatau P, Lubin D, Valero FPJ, Weaver CP, Pilewski P.  2000.  Determination of surface heating by convective cloud systems in the central equatorial Pacific from surface and satellite measurements. Journal of Geophysical Research-Atmospheres. 105:14807-14821.   10.1029/2000jd900109   AbstractWebsite

The heating of the ocean surface by longwave radiation from convective clouds has been estimated using measurements from the Central Equatorial Pacific Experiment (CEPEX). The ratio of the surface longwave cloud forcing to the cloud radiative forcing on the total atmospheric column is parameterized by the f factor. The f factor is a measure of the partitioning of the cloud radiative effect between the surface and the troposphere. Estimates of the f factor have been obtained by combining simultaneous observations from ship, aircraft, and satellite instruments. The cloud forcing near the ocean surface is determined from radiometers on board the National Oceanic and Atmospheric Administration P-3 aircraft and the R/V John Vickers. The longwave cloud forcing at the top of the atmosphere has been estimated from data obtained from the Japanese Geostationary Meteorological Satellite GMS 4. A new method for estimating longwave fluxes from satellite narrowband radiances is described. The method is based upon calibrating the satellite radiances against narrowband and broadband infrared measurements from the high-altitude NASA ER-2 aircraft. The average value of f derived from the surface and satellite observations of convective clouds is 0.15 +/- 0.02. The area-mean top-of-atmosphere longwave forcing by convective clouds in the region 10 degrees S-10 degrees N, 160 degrees E-160 degrees W is 40 W/m(2) during CEPEX. Those results indicate that the surface longwave forcing by convective clouds was approximately 5 W/m(2) in the central equatorial Pacific and that this forcing is the smallest radiative component of the surface energy budget.

Valero, FPJ, Collins WD, Pilewskie P, Bucholtz A, Flatau PJ.  1997.  Direct radiometric observations of the water vapor greenhouse effect over the equatorial Pacific ocean. Science. 275:1773-1776.   10.1126/science.275.5307.1773   AbstractWebsite

Airborne radiometric measurements were used to determine tropospheric profiles of the clear sky greenhouse effect. At sea surface temperatures (SSTs) larger than 300 kelvin, the clear sky water vapor greenhouse effect was found to increase with SST at a rate of 13 to 15 watts per square meter per kelvin. Satellite measurements of infrared radiances and SSTs indicate that almost 52 percent of the tropical oceans between 20 degrees N and 20 degrees S are affected during all seasons. Current general circulation models suggest that the increase in the clear sky water vapor greenhouse effect with SST may have climatic effects an a planetary scale.

Draine, BT, Flatau PJ.  2008.  Discrete-dipole approximation for periodic targets: theory and tests. Journal of the Optical Society of America a-Optics Image Science and Vision. 25:2693-2703.   10.1364/josaa.25.002693   AbstractWebsite

The discrete-dipole approximation (DDA) is a powerful method for calculating absorption and scattering by targets that have sizes smaller than or comparable to the wavelength of the incident radiation. The DDA can be extended to targets that are singly or doubly periodic. We generalize the scattering amplitude matrix and the 4 x 4 Mueller matrix to describe scattering by singly and doubly periodic targets and show how these matrices can be calculated using the DDA. The accuracy of DDA calculations using the open-source code DDSCAT is demonstrated by comparison with exact results for infinite cylinders and infinite slabs. A method for using the DDA solution to obtain fields within and near the target is presented, with results shown for infinite slabs. (C) 2008 Optical Society of America

Draine, BT, Flatau PJ.  1994.  Discrete-Dipole Approximation for Scattering Calculations. Journal of the Optical Society of America a-Optics Image Science and Vision. 11:1491-1499.   10.1364/josaa.11.001491   AbstractWebsite

The discrete-dipole approximation (DDA) for scattering calculations, including the relationship between the DDA and other methods, is reviewed. Computational considerations, i.e., the use of complex-conjugate gradient algorithms and fast-Fourier-transform methods, are discussed. We test the accuracy of the DDA by using the DDA to compute scattering and absorption by isolated, homogeneous spheres as well as by targets consisting of two contiguous spheres. It is shown that, for dielectric materials (Absolute value of m less than or similar to 2), the DDA permits calculations of scattering and absorption that are accurate to within a few percent.

Flatau, MK, Flatau PJ, Rudnick D.  2001.  The dynamics of double monsoon onsets. Journal of Climate. 14:4130-4146.   10.1175/1520-0442(2001)014<4130:tdodmo>2.0.co;2   AbstractWebsite

Double monsoon onset develops when the strong convection in the Bay of Bengal is accompanied by the monsoonlike circulation and appears in the Indian Ocean in early May, which is about 3 weeks earlier than the climatological date of the onset (1 Jun). The initial "bogus onset'' is followed by the flow weakening or reversal and clear-sky and dry conditions over the monsoon region. The best example of such a phenomenon is the development of the summer monsoon in 1995, when monsoonlike perturbations that appeared in mid-May disappeared by the end of the month and were followed by a heat wave in India, delaying onset of the monsoon. The climatology of double onsets is analyzed, and it is shown that they are associated with delay of the monsoon rainfall over India. This analysis indicates that the development of bogus onsets depends on the timing of intraseasonal oscillation in the Indian Ocean and the propagation of convective episodes into the western Pacific. There is evidence that an SST evolution in the Bay of Bengal and the western Pacific plays an important role in this phenomenon. It is shown that in the case of the double monsoon onset it is possible to predict hot and dry conditions in India before the real monsoon onset. In the 32 yr of climatological data, six cases of double monsoon onset were identified.

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Schmidt, JM, Flatau PJ, Harasti PR.  2017.  Evidence for a nimbostratus uncinus in a convectively generated mixed-phase stratiform cloud shield. Journal of the Atmospheric Sciences. 74:4093-4116.   10.1175/jas-d-17-0074.1   AbstractWebsite

The structure of a melting layer associated with a mesoconvective system is examined using a combination of in situ aircraft measurements and a unique Doppler radar operated by the U.S. Navy that has a range resolution as fine as 0.5 m. Interest in this case was motivated by ground-based all-sky camera images that captured the transient development of midlevel billow cloud structures within a precipitating trailing stratiform cloud shield associated with a passing deep convective system. A sequence of high-fidelity time-height radar measurements taken of this storm system reveal that the movement of the billow cloud structure over the radar site corresponded with abrupt transitions in the observed low-level precipitation structure. Of particular note is an observed transition from stratiform to more periodic and vertically slanted rain shaft structures that both radar and aircraft measurements indicate have the same temporal periodicity determined to arise visually between successive billow cloud bands. Doppler, balloon, and aircraft measurements reveal these transient bands are associated with a shallow circulation field that resides just above the melting level in a layer of moist neutral stability and strong negative vertical wind shear. The nature of these circulations and their impact on the evolving precipitation field are described in the context of known nimbostratus cloud types.

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Flatau, PJ, Draine BT.  2012.  Fast near field calculations in the discrete dipole approximation for regular rectilinear grids. Optics Express. 20:1247-1252.   10.1364/OE.20.001247   AbstractWebsite

A near-field calculation of light electric field intensity inside and in the vicinity of a scattering particle is discussed in the discrete dipole approximation. A fast algorithm is presented for gridded data. This algorithm is based on one matrix times vector multiplication performed with the three dimensional fast Fourier transform. It is shown that for moderate and large light scattering near field calculations the computer time required is reduced in comparison to some of the other methods. (C) 2012 Optical Society of America

Flatau, PJ.  2004.  Fast solvers for one dimensional light scattering in the discrete dipole approximation. Optics Express. 12:3149-3155.   10.1364/OPEX.12.003149   AbstractWebsite

In this paper we propose new algorithms for solution of light scattering on non-spherical particles using one-dimensional variant of discrete dipole approximation. We discuss recent advances in algorithms for matrices with structures in context of the discrete dipole approximation and show that it is possible to apply these advances to form non-iterative solvers and improve algorithmic complexity in case of many incoming plane parallel waves. (C) 2004 Optical Society of America.

Flatau, M, Flatau PJ, Phoebus P, Niller PP.  1997.  The feedback between equatorial convection and local radiative and evaporative processes: The implications for intraseasonal oscillations. Journal of the Atmospheric Sciences. 54:2373-2386.   10.1175/1520-0469(1997)054<2373:tfbeca>2.0.co;2   AbstractWebsite

Existing theories of the Madden-Julian oscillation neglect the feedback between the modification of sea surface temperature by the convection and development of a convective cluster itself. The authors show that the convection-generated SST gradient plays an important role in cluster propagation and development. The relative importance of radiative and evaporative fluxes in SST regulation is also discussed. Various Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment and Central Equatorial Pacific Experiment observation platforms are used to estimate the effects of equatorial convection on SST changes during March 1993. The data include drifting buoys and TAO-buoy array measurements, combined with the Navy Operational Global Atmospheric Prediction System analyzed surface wind fields and Geostationary Meteorological Satellite cloud-top temperatures. It is shown that during the equatorial convection episode SST is decreasing under and to the west of the convective heat source due to the large wind velocities and solar flux reduction. To the east of the source, in the convergence region of a Kelvin wave, low wind speeds and high insolation cause the SST to increase. The data are used to formulate an empirical relationship between wind speed and the 24-h SST change on the equator. Although formulated in terms of wind speed, this relationship implicitly includes radiative effects. This equation is then used in a global circulation model to examine the effect of SST feedback on the behavior of equatorial convection. A series of experiments is performed using an R15 general circulation model of the ''aquaplanet'' with a zonally symmetric SST distribution. In the case with fixed SSTs, equatorial wind fluctuations have the character of waves propagating around the globe with a phase speed of about 20 m s(-1). When the effect of SST modification is included, the fluctuations slow down and become more organized. In addition, a 40-60-day peak appears in the spectral analysis of equatorial precipitation.

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Lelieveld, J, Berresheim H, Borrmann S, Crutzen PJ, Dentener FJ, Fischer H, Feichter J, Flatau PJ, Heland J, Holzinger R, Korrmann R, Lawrence MG, Levin Z, Markowicz KM, Mihalopoulos N, Minikin A, Ramanathan V, de Reus M, Roelofs GJ, Scheeren HA, Sciare J, Schlager H, Schultz M, Siegmund P, Steil B, Stephanou EG, Stier P, Traub M, Warneke C, Williams J, Ziereis H.  2002.  Global air pollution crossroads over the Mediterranean. Science. 298:794-799.   10.1126/science.1075457   AbstractWebsite

The Mediterranean Intensive Oxidant Study, performed in the summer of 2001, uncovered air pollution layers from the surface to an altitude of 15 kilometers. In the boundary layer, air pollution standards are exceeded throughout the region, caused by West and East European pollution from the north. Aerosol particles also reduce solar radiation penetration to the surface, which can suppress precipitation. In the middle troposphere, Asian and to a lesser extent North American pollution is transported from the west. Additional Asian pollution from the east, transported from the monsoon in the upper troposphere, crosses the Mediterranean tropopause, which pollutes the lower stratosphere at middle latitudes.

Witek, ML, Flatau PJ, Quinn PK, Westphal DL.  2007.  Global sea-salt modeling: Results and validation against multicampaign shipboard measurements. Journal of Geophysical Research-Atmospheres. 112   10.1029/2006jd007779   AbstractWebsite

[1] Open-ocean measurements of sea-salt concentrations from five different campaigns are used to validate the sea-salt parameterization in numerical models. The data set is unique in that it is from open-ocean shipboard measurements which alleviates typical problems associated with onshore wave breaking on land stations ( surf zone). The validity of the sea-salt parameterizations is tested by employing a global forecasting model and transport model with detailed representation of dry and wet deposition, advection and diffusion, and other physical processes. It is shown that the inclusion of these processes leads to good agreement with shipboard measurements. The correlation coefficient of measured and modeled sea-salt mass concentrations for all data points was 0.76 and varied from 0.55 to 0.84 for different experiments. Average sea-salt mass concentration was 4.6 mu g/m(3) from measurements and 7.3 mu g/m(3) from the model, for all considered experiments. It was found that model-measurements discrepancies were affected by wet deposition uncertainties but also suggested was the influence of source uncertainties in the strong wind-speed regime, lack of a wind-speed threshold for emission onset, and lack of size differentiation in applied deposition velocity. No apparent relationship between the water temperature and the measured sea-salt concentration was found in the analyzed data set.

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Baranowski, DB, Flatau MK, Flatau PJ, Matthews AJ.  2016.  Impact of atmospheric convectively coupled equatorial Kelvin waves on upper ocean variability. Journal of Geophysical Research: Atmospheres. 121:2045-2059.   10.1002/2015JD024150   Abstract

Convectively coupled Kelvin waves (CCKWs) are atmospheric weather systems that propagate eastward along the equatorial wave guide with phase speeds between 11 and 14 m s−1. They are an important constituent of the convective envelope of the Madden-Julian oscillation (MJO), for which ocean-atmosphere interactions play a vital role. Hence, ocean-atmosphere interactions within CCKWs may be important for MJO development and prediction and for tropical climate, in general. Although the atmospheric structure of CCKWs has been well studied, their impact on the underlying ocean is unknown. In this paper, the ocean-atmosphere interactions in CCKWs are investigated by a case study from November 2011 during the CINDY/DYNAMO field experiment, using in situ oceanographic measurements from an ocean glider. The analysis is then extended to a 15 year period using precipitation data from the Tropical Rainfall Measuring Mission and surface fluxes from the TropFlux analysis. A methodology is developed to calculate trajectories of CCKWs. CCKW events are strongly controlled by the MJO, with twice as many CCKWs observed during the convectively active phase of the MJO compared to the suppressed phase. Coherent ocean-atmosphere interaction is observed during the passage of a CCKW, which lasts approximately 4 days at any given longitude. Surface wind speed and latent heat flux are enhanced, leading to a transient suppression of the diurnal cycle of sea surface temperature (SST) and a sustained decrease in bulk SST of 0.1°C. Given that a typical composite mean MJO SST anomaly is of the order of 0.3°C, and more than one CCKW can occur during the active phase of a single MJO event, the oceanographic impact of CCKWs is of major importance to the MJO cycle.

Flatau, PJ.  1997.  Improvements in the discrete-dipole approximation method of computing scattering and absorption. Optics Letters. 22:1205-1207.   10.1364/ol.22.001205   AbstractWebsite

Improvements in complex-conjugate gradient algorithms applied to the discrete-dipole approximation are reported. It is shown that computational time is reduced by use of the stabilized version of the biconjugate gratings algorithm, with diagonal left preconditioning. (C) 1997 Optical Society of America.