Penetration Depth Of Solar Radiation Research Articles

Variations and Depth of Formation of Submesoscale Eddy Structures in Satellite Ocean Color Data in the Southwestern Region of the Peter the Great Bay

The aim of this study was to develop methods for determining the most significant contrasts in satellite ocean color data arising in the presence of a submesoscale eddy structure, as well as to determine the corresponding depths of the upper layer of the sea where these contrasts are formed. The research was carried out on the example of the chain of submesoscale eddies identified in the Tumen River water transport area in the Japan/East Sea. MODIS Aqua/Terra satellite data of the remotely sensed reflectance (Rrs) and Rrs band ratio at various wavelengths, chlorophyll-a concentration, and, for comparison, sea surface temperature (sst) were analyzed. Additionally, the results of ship surveys in September 2009 were used to study the influence of eddy vertical structure on the obtained remote characteristics. The best characteristic for detecting the studied eddies in satellite ocean color data was the MODIS chlor_a standard product, which is an estimate of chlorophyll-a concentration obtained by a combination of the three-band reflectance difference algorithm (CI) for low concentrations and the band-ratio algorithm (OCx) for high concentrations. At the same time, the weakest contrasts were in sst data due to similar water heating inside and outside the eddies. The best eddy contrast-to-noise ratio according to Rrs spectra is achieved at 547 nm in the spectral region of seawater with maximum transparency and low relative errors of measurements. The Rrs at 678 nm and associated products may be a significant characteristic for eddy detection if there are many phytoplankton in the eddy waters. The maximum depth of the remotely sensed contrast formation of the considered eddy vertical structure was ~6 m, which was significantly less than the maximum spectral penetration depth of solar radiation for remote sensing, which was in the 14–17 m range. The results obtained can be used to determine the characteristics that provide the best contrast for detecting eddy structures in remotely sensed reflectance data and to improve the interpretation of remote spectral ocean color data in the areas of eddies activity.

A Dynamics of Surface Temperature Forced by Solar Radiation

AbstractDue to lack of a unified description of the Earth surface temperature, a generic dynamic equation is postulated as an inference from the special case of snow. Solar radiation is explicitly included in the formulation for transparent media such as snow, ice and water while implicitly through (conductive) surface heat flux for non‐transparent media such as soil. The physical parameters of the equation are medium thermal inertia, thermal and radiative diffusivity. The equation for transparent media reduces to the familiar force‐restore model of soil surface temperature when the penetration depth of solar radiation tends to zero. Proof‐of‐concept validation for snow surface temperature as a paradigm of transparent media at three sites in the Arctic and Antarctica confirms the postulated equation as a generic description of the dynamics of surface temperature.

Natural Convection Induced by Diurnal Heating and Cooling over a Fully Vegetated Slope

In this study, by assuming a small bottom slope, asymptotic solutions were developed to discuss natural convection within rooted emergent vegetation in response to different heating and cooling mechanisms. Based upon the maximum water depth in comparison to the penetration depth of solar radiation, two scenarios in shallow and deep waters were examined. The temperature structures showed that isotherms in shallows are near vertical but become stable stratified layers (horizontal isotherms) in deep regions. In shallow regions, horizontal velocity profiles perform classic cubic shapes, while the horizontal velocity in deep regions is constant near the surface, and a local upslope flow occurs near the bottom. In shallow water, viscous effects are dominant to shape the velocity profiles, whereas vegetation drag becomes more important in deep regions. By using turbulent parameters, horizontal exchange flowrates and velocities predicted by the asymptotic solutions show good agreements with the existing measurements.

Optical and radiative properties analysis and optimization study of the gradually-varied volumetric solar receiver

The volumetric solar receiver is an important component of Concentrated Solar Power (CSP) system. In recent years, some studies concerned with the novel structures of the volumetric solar receiver have been conducted. In this paper, a gradually-varied volumetric solar receiver is proposed. The major feature of this structure is its porosity which decreases gradually from the front surface to the rear surface. Based on the modified random spherical bubbles method, a 3D computational model of this porosity-changed solar receiver is reconstructed. In addition, by combining with the Monte Carlo Ray Tracing (MCRT) method, the optical and radiative properties of this receiver are investigated. The results show that the reflection loss could be reduced owing to the lower reflectivity of this structure. It also outperforms in solar energy absorption compared with the uniform structures that are examined in this paper and exhibits a uniform solar radiative flux distribution inside the receiver. Finally, with the use of genetic algorithm, the porosity distribution of the gradually-varied volumetric solar receiver is further optimized, which leads to a much larger penetration depth of solar radiation. These results suggest that the gradually-varied porous structure provides a novel design method to enhance the solar radiation absorption and the volumetric absorption of a volumetric solar receiver.

Natural convection induced by radiation in a water filled square cavity: Experimental observations

This investigation is motivated by interest in the mixing caused by the absorption of solar radiation in the near-shore regions of lakes. In the daytime, incoming solar radiation is absorbed by the water following Beer’s law. In the near-shore region where the water depth is less than the penetration depth of solar radiation, the residual radiation reaches the bottom and is absorbed and re-emitted back into the water body as a bottom heat flux, resulting in an adverse temperature gradient which may become unstable. In this laboratory-scale experimental study, this situation is modelled with a water-filled, open top tank with a black bottom subjected to radiative heating from a halogen theatre spotlight. Concurrent shadowgraph and Particle Image Velocimetry (PIV) are utilised for simultaneous visualisation of the temperature field and flow measurements. Initially, there is no motion and two distinct thermal boundary layers simultaneously grow from the water surface and from the bottom boundary. The bottom boundary layer becomes unstable at a certain thickness, and rising plumes are formed. The plumes transfer heat and cause circulation and vertical mixing in the water body. Subsequently the plumes disappear as the bottom boundary layer is dismantled, the bottom boundary layer is re-established, and the plumes re-formed. This paper will focus on characterising the first and the second stages. Accordingly, the onset of convection, plume rise height, and plume rise velocity are investigated through analysis of the PIV and shadowgraph images and compared with previously published scaling.

An ocean‐biology‐induced negative feedback on ENSO as derived from a hybrid coupled model of the tropical Pacific

AbstractBiological conditions in the tropical Pacific Ocean (e.g., phytoplankton biomass) are strongly regulated by physical changes that are associated with the El Niño‐Southern Oscillation (ENSO). The existence and variation of phytoplankton biomass act to modulate the vertical penetration of the incoming sunlight into the upper ocean, which causes an ocean‐biology‐induced heating (OBH) effect on the climate system. Previously, the penetration depth of solar radiation in the upper ocean (Hp) has been defined to describe the related bioclimate connections. An empirical model for interannual Hp variability that is parameterized in terms of its relationship with the sea surface temperature (SST) in the tropical Pacific was derived from remotely sensed ocean color data and is incorporated into a hybrid coupled model (HCM) to represent the OBH effects. In this paper, several HCM experiments are performed to demonstrate the biofeedback onto the ENSO, including a climatological Hp run (in which Hp is prescribed as only seasonally varying), interannual Hp runs (with different intensities of the interannually varying OBH effects), and a run in which the sign of the OBH effect is reversed. Significant modulating impacts on the interannual variability are found in the HCM and are characterized by a negative feedback between the ocean biology and the climate system in the tropical Pacific; stronger the OBH feedback, weaker the interannual variability. The processes that are involved in the feedback are analyzed. The SST is modulated indirectly by dynamic ocean processes that are induced by OBH. The significance and implication of the OBH effects are discussed in terms of their roles in ENSO variability and the model biases in the tropical Pacific.

Theoretical and Experimental Investigations Regarding Open Volumetric Receivers of CRS

Concentrated sunlight is absorbed in solar thermal power plants by heat resistant absorbers and converted into usable heat which is transferred to a carrier medium. In solar tower power plants such as the plant in Jülich porous absorbers can reach temperatures up to 1000°C and higher. At this power plant air as heat transfer medium is sucked in through the absorber and heated up to about 700°C. The absorber is composed of highly porous ceramic or metal wire structures. The SIJ investigates the optimization of solar absorption and the convective heat transfer to the air using thermo and fluid mechanical calculations. In such simulations the key quantities are the penetration depth of solar radiation κ and the volumetric heat transfer coefficient αv, which indicates how much energy - depending on the volume and temperature difference - is transferred by convection between solid and fluid. The attenuation of the radiation into the depth of the absorber is described generally by an exponential function with parameter κ. This is accompanied by heat transfer to the structure. Existing models of the key quantities have been validated by experimental data.

Experimental determination of the absorption enhancement parameter of snow

AbstractIn optical models snow is commonly treated as a disperse collection of particles. In this representation, the penetration depth of solar radiation is sensitive to the shape of the particles, in particular to the absorption enhancement parameter, B, that quantifies the lengthening of the photon path inside grains due to internal multiple reflections. Spherical grains, with theoretical B = 1.25, are often used. We propose an experimental method to determine B, and apply it to 36 snow samples and 56 snow strata. The method is based on radiative transfer modeling and combined measurements of reflectance and irradiance profiles. Such measurements are performed in the laboratory and in the field, in Antarctica and the French Alps. The retrieved values of B are in the range 0.7–2.4, with a wide peak between 1.4 and 1.8. An analysis of measurement error propagation based on a Bayesian framework shows that the uncertainty on B is ± 0.1, which is the order of magnitude of variations between different snow types. Thus, no systematic link between B and snow type can be inferred. Here we recommend using shapes with B = 1.6 to model snow optical properties, rather than spherical grains.

Experimental determination of the absorption enhancement parameter of snow

Abstract In optical models snow is commonly treated as a disperse collection of particles. In this representation, the penetration depth of solar radiation is sensitive to the shape of the particles, in particular to the absorption enhancement parameter, B, that quantifies the lengthening of the photon path inside grains due to internal multiple reflections. Spherical grains, with theoretical B = 1.25, are often used. We propose an experimental method to determine B, and apply it to 36 snow samples and 56 snow strata. The method is based on radiative transfer modeling and combined measurements of reflectance and irradiance profiles. Such measurements are performed in the laboratory and in the field, in Antarctica and the French Alps. The retrieved values of B are in the range 0.7–2.4, with a wide peak between 1.4 and 1.8. An analysis of measurement error propagation based on a Bayesian framework shows that the uncertainty on B is ± 0.1, which is the order of magnitude of variations between different snow types. Thus, no systematic link between B and snow type can be inferred. Here we recommend using shapes with B = 1.6 to model snow optical properties, rather than spherical grains.

Using Satellite Ocean Color Data to Derive an Empirical Model for the Penetration Depth of Solar Radiation (Hp) in the Tropical Pacific Ocean

Abstract Satellite-based ocean color measurements indicate clear evidence for bioclimate interactions in the tropical Pacific associated with El Niño–Southern Oscillation (ENSO). Recent modeling studies have demonstrated that ocean biology can potentially affect the climate through the penetration depth of solar radiation in the upper ocean (Hp), a primary parameter in coupling biology to physics in the ocean. At present, interannual variability in Hp and its related bioclimate feedback effects have not been adequately represented in coupled ocean–atmosphere models. In this work, chlorophyll (Chl) concentration data from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS), available since 1997, are used to characterize interannual Hp variability in the tropical Pacific and to quantify its relationships with physical fields, including sea surface temperature (SST) and sea level (SL). It is found that interannual Hp variability is dominated by ENSO signals, with the largest variability located in the central basin near the date line and a coherent relationship with SST. A singular value decomposition (SVD) analysis is adopted to extract interannual covariability patterns between Hp and SST during the period 1997–2007. Their close relationships are then utilized to construct an empirical anomaly model for Hp, allowing for its prognostic estimate in terms of SST anomalies without explicit involvement of a marine ecosystem model. Validation and sensitivity experiments indicate that the empirical model can reasonably well capture interannual Hp responses to SST anomalies in association with ENSO. The derived empirical Hp model offers a simple and an effective way to parameterize and represent the effects of Chl containing biomass on penetrative solar radiation in the tropical Pacific, demonstrating the dynamical implication of remotely sensed Chl data for bioclimate coupling studies. Further improvements and applications of the empirical Hp model to climate modeling are discussed.

Response of sea surface temperature to chlorophyll-a concentration in the tropical Pacific: Annual mean, seasonal cycle, and interannual variability

The response of the upper-ocean temperatures and currents in the tropical Pacific to the spatial distribution of chlorophyll-a and its seasonal cycle is investigated using a coupled atmosphere-ocean model and a stand-alone oceanic general circulation model. The spatial distribution of chlorophyll-a significantly influences the mean state of models in the tropical Pacific. The annual mean SST in the eastern equatorial Pacific decreases accompanied by a shallow thermocline and stronger currents because of shallow penetration depth of solar radiation. Equatorial upwelling dominates the heat budget in that region. Atmosphere-ocean interaction processes can further amplify such changes. The seasonal cycle of chlorophyll-a can dramatically change ENSO period in the coupled model. After introducing the seasonal cycle of chlorophyll-a concentration, the peak of the power spectrum becomes broad, and longer periods (>3 years) are found. These changes led to ENSO irregularities in the model. The increasing period is mainly due to the slow speed of Rossby waves, which are caused by the shallow mean thermocline in the northeastern Pacific.

Flow response to periodic thermal forcing in a reservoir with water depth beyond the penetration depth of the solar radiation

The present investigation is concerned with the transient response of the flow in a reservoir to diurnal heating and cooling due to heat transfer through the water surface. In this study, the maximum water depth in the reservoir is assumed to be five times the penetration depth of solar radiation. The numerical results reveal that, in the present case, the flow response to radiative heating is very weak compared with the response to surface cooling. There is also a clear time lag in the flow response to the switches of the thermal forcing. The lag time depends on the Grashof number.

Variations of the snow physical parameters and their effects on albedo in Sapporo, Japan

AbstractContinuous measurements of the radiation budget and meteorological components, along with frequent snow-pit work, were performed in Sapporo, Hokkaido, Japan, during two winters from 2003 to 2005. The measured relationships between broadband albedos and the mass concentration of snow impurities were compared with theoretically predicted relationships calculated using a radiative transfer model for the atmosphere–snow system in which different types (in light absorption) of impurity models based on mineral dust and soot were assumed. The result suggests that the snow in Sapporo was contaminated not only with mineral dust but also with more absorptive soot. A comparison of the measured relationships between broadband albedos and snow grain size for two different layers with the theoretically predicted relationships revealed that the visible albedo contains information about the snow grain size in deeper snow layers (10 cm), and the near-infrared albedo contains only surface information. This is due to the difference in penetration depth of solar radiation into snow between the visible and the near-infrared wavelengths.