Water Temperature Profiles Research Articles

Radiometric Information Content for Water Vapor and Temperature Profiling in Clear Skies Between 10 and 200 GHz

Atmospheric profiles of water vapor and temperature can be estimated using appropriate retrieval algorithms based on radiometric measurements and atmospheric statistics. Radiometric measurements at multiple frequencies contribute information to profile retrieval, although at some frequencies the information they provide can be highly correlated with that at other frequencies due to similar sensitivities to changes in atmospheric pressure, temperature, and water vapor mixing ratio as a function of altitude. The goal for profile retrieval is to obtain as many independent measurements as possible, both to maximize the vertical resolution and to minimize the retrieval error of the profile. The goal of this study is to determine sets of frequencies in the range from 10 to 200 GHz that provide the largest amount of mutually independent information on water vapor and temperature profiles from ground and airborne instruments for clear sky measurements. Results of such a study are important and useful for frequency selection and design of microwave and millimeter-wave radiometers for humidity and temperature profiling. A branch and bound feature selection algorithm has been used to determine sets of frequencies between 10 and 200 GHz that have the greatest number of degrees of freedom (DOF) for water vapor and temperature retrieval. In general, it has been found that the frequency ranges of 20–23, 85–90, and 165–200 GHz are useful for water vapor profile retrieval, whereas the frequency ranges of 55–65 and 116–120 GHz are useful for temperature profile retrieval. Finally, an analysis has been performed to determine the impact of measurement uncertainty on the number of DOF of measurement and also on the vertical resolution. It was also found that vertical resolution is directly related to the number of DOF.

Initial evaluations of a Gulf of Mexico/Caribbean ocean forecast system in the context of the Deepwater Horizon disaster

In response to the Deepwater Horizon (DwH) oil spill event in 2010, the Naval Oceanographic Office deployed a nowcast-forecast system covering the Gulf of Mexico and adjacent Caribbean Sea that was designated Americas Seas, or AMSEAS, which is documented in this manuscript. The DwH disaster provided a challenge to the application of available ocean-forecast capabilities, and also generated a historically large observational dataset. AMSEAS was evaluated by four complementary efforts, each with somewhat different aims and approaches: a university research consortium within an Integrated Ocean Observing System (IOOS) testbed; a petroleum industry consortium, the Gulf of Mexico 3-D Operational Ocean Forecast System Pilot Prediction Project (GOMEX-PPP); a British Petroleum (BP) funded project at the Northern Gulf Institute in response to the oil spill; and the Navy itself. Validation metrics are presented in these different projects for water temperature and salinity profiles, sea surface wind, sea surface temperature, sea surface height, and volume transport, for different forecast time scales. The validation found certain geographic and time biases/errors, and small but systematic improvements relative to earlier regional and global modeling efforts. On the basis of these positive AMSEAS validation studies, an oil spill transport simulation was conducted using archived AMSEAS nowcasts to examine transport into the estuaries east of the Mississippi River. This effort captured the influences of Hurricane Alex and a non-tropical cyclone off the Louisiana coast, both of which pushed oil into the western Mississippi Sound, illustrating the importance of the atmospheric influence on oil spills such as DwH.

Temperature diagnostic to identify high risk areas and optimize Legionella pneumophila surveillance in hot water distribution systems

Legionella pneumophila is frequently detected in hot water distribution systems and thermal control is a common measure implemented by health care facilities. A risk assessment based on water temperature profiling and temperature distribution within the network is proposed, to guide effective monitoring strategies and allow the identification of high risk areas. Temperature and heat loss at control points (water heater, recirculation, representative points-of-use) were monitored in various sections of five health care facilities hot water distribution systems and results used to develop a temperature-based risk assessment tool. Detailed investigations show that defective return valves in faucets can cause widespread temperature losses because of hot and cold water mixing. Systems in which water temperature coming out of the water heaters was kept consistently above 60 °C and maintained above 55 °C across the network were negative for Legionella by culture or qPCR. For systems not meeting these temperature criteria, risk areas for L. pneumophila were identified using temperature profiling and system's characterization; higher risk was confirmed by more frequent microbiological detection by culture and qPCR. Results confirmed that maintaining sufficiently high temperatures within hot water distribution systems suppressed L. pneumophila culturability. However, the risk remains as shown by the persistence of L. pneumophila by qPCR.

湖水温鉛直分布の季節変動からみた一ノ目潟の水循環機構

湖水温鉛直分布の季節変動からみた一ノ目潟の水循環機構

A propane water-to-water heat pump booster for sanitary hot water production: Seasonal performance analysis of a new solution optimizing COP

Electrical heat pumps for sanitary hot water production achieve a high performance with a good matching of water and refrigerant temperature profiles during the heat rejection stage, as it happens in CO2 systems. This work considers the thermodynamic possibility to adapt the condenser pressure of a propane heat pump to maximize the COP, while producing sanitary hot water up to 60 °C from a heat sink equal to 15 or 25 °C. The performance of the heat pump is calculated through specific models which, in combination with a TRNSYS model of the whole system, allowed to assess its seasonal performance for a hotel in Strasbourg, also varying the control logic and the size of the storage tank. Results obtained led to the conclusion that, for achieving a high seasonal performance, the control logic of the tank has the largest influence.

Experimental validation of a thermodynamic boiler model under steady state and dynamic conditions

Nowadays dynamic building simulation is an essential tool for the design of heating systems for residential buildings. The simulation of buildings heated by biomass systems, first of all needs detailed boiler models, capable of simulating the boiler both as a stand-alone appliance and as a system component. This paper presents the calibration and validation of a boiler model by means of laboratory tests. The chosen model, i.e. TRNSYS “Type 869”, has been validated for two commercially available pellet boilers of 6 and 12kW nominal capacities. Two test methods have been applied: the first is a steady state test at nominal load and the second is a load cycle test including stationary operation at different loads as well as transient operation. The load cycle test is representative of the boiler operation in the field and characterises the boiler’s stationary and dynamic behaviour. The model had been calibrated based on laboratory data registered during stationary operation at different loads and afterwards it was validated by simulating both the stationary and the dynamic tests. Selected parameters for the validation were the heat transfer rates to water and the water temperature profiles inside the boiler and at the boiler outlet. Modelling results showed better agreement with experimental data during stationary operation rather than during dynamic operation. Heat transfer rates to water were predicted with a maximum deviation of 10% during the stationary operation, and a maximum deviation of 30% during the dynamic load cycle. However, for both operational regimes the fuel consumption was predicted within a 10% deviation from the experimental values.

Modeling density currents in a typical tributary of the Three Gorges Reservoir, China

The initial filling of the Three Gorges Reservoir (TGR), China, has caused serious phytoplankton blooms in its tributary bays. A two-dimensional, laterally averaged, hydrodynamic and water quality CE-QUAL-W2 model was used to simulate the hydrodynamics and water temperature of a typical tributary (Xiangxi Bay XXB) of the TGR to study the relationship between phytoplankton and density currents. The CE-QUAL-W2 model was calibrated to data collected in XXB (depth profiles of velocity and water temperature at three locations) from January 2008 through December 2008. The model performed well in simulating (1) flow velocity profiles, (2) unusual water temperature profiles, (3) the plunge point location of the intrusion layer, (4) propagation speed, and (5) the travel distance of the density currents. The model was then used to examine potential factors that affect the density currents, such as water level fluctuations in the mainstem of the TGR, water temperature differences between the mainstem and XXB, and inflow rates to XXB. Therefore, a better understanding of the hydrodynamics of tributaries in the TGR can be used to understand the aquatic ecosystem dynamics of these tributaries.

Numerical simulation of the impacts of water level variation on water age in Dahuofang Reservoir

The transport timescales were investigated in response to water level variation under different constant flow rates in Dahuofang Reservoir. The concept of water age was applied to quantify the transport timescales. A three-dimensional hydrodynamic model was developed based on the Environmental Fluid Dynamics Code (EFDC). The model was calibrated for water surface elevation and temperature profiles from April 1, 2008 to October 31, 2008. Comparisons of observed and modeled data showed that the model reproduced the water level fluctuation and thermal stratification during warm season and vertical mixing during cold season fairly well. The calibrated model was then applied to investigate the response of water age to water level changes in Dahuofang Reservoir. Model results showed that water age increases from confluence toward dam zone. In the vertical direction, the water age is relatively uniform at upstream and stratifies further downstream, with a larger value at bottom layer than at surface layer. Comparisons demonstrated that water level variation has a significant impact on transport timescales in the reservoir. The impact of water level drawdown on water age is stronger at bottom layer than at surface layer. Under high flow conditions, the water age decreases 0–20 days at surface layer and 15–25 days at bottom layer. Under mean flow conditions, the water age decreases 20–30 days at surface layer and 30–50 days at bottom layer. Furthermore, the impact is minor in the upstream and increases further downstream. The vertical stratification of water age weakens as the water level decreases. This study provides a numerical tool to quantify the transport timescale in Dahuofang Reservoir and supports adaptive management of regional water resources by local authorities.

Wind‐driven nearshore sediment resuspension in a deep lake during winter

AbstractOngoing public concern over declining water quality at Lake Tahoe, California‐Nevada (USA) led to an investigation of wind‐driven nearshore sediment resuspension that combined field measurements and modeling. Field data included: wind speed and direction, vertical profiles of water temperature and currents, nearbed velocity, lakebed sediment characteristics, and suspended sediment concentration and particle size distribution. Bottom shear stress was computed from ADV‐measured nearbed velocity data, adapting a turbulent kinetic energy method to lakes, and partitioned according to its contributions attributed to wind‐waves, mean currents, and random motions. When the total shear stress exceeded the critical shear stress, the contribution to overall shear stress was about 80% from wind‐waves and 10% each from mean currents and random motions. Therefore, wind‐waves were the dominant mechanism resulting in sediment resuspension as corroborated by simultaneous increases in shear stress and total measured sediment concentration. The wind‐wave model STWAVE was successfully modified to simulate wind‐wave‐induced sediment resuspension for viscous‐dominated flow typical in lakes. Previous lake applications of STWAVE have been limited to special instances of fully turbulent flow. To address the validity of expressions for sediment resuspension in lakes, sediment entrainment rates were found to be well represented by a modified 1991 García and Parker formula. Last, in situ measurements of suspended sediment concentration and particle size distribution revealed that the predominance of fine particles (by particle count) that most negatively impact clarity was unchanged by wind‐related sediment resuspension. Therefore, we cannot assume that wind‐driven sediment resuspension contributes to Lake Tahoe's declining nearshore clarity.

Impacts of regional warming on long‐term hypolimnetic anoxia and dissolved oxygen concentration in a deep lake

AbstractAlthough few reports have described long‐term continuous anoxia in aquatic systems, Lake Ikeda in Japan experienced such conditions in the hypolimnion from 1990 to 2010. The present study aimed to assess temporal fluctuations in the lake's thermal stability from 1978 to 2011 to understand the influence of regional climate change on hypolimnetic anoxia in this lake. Because complete vertical mixing, which supplies dissolved oxygen (DO) to the hypolimnion, potentially occurs on February, we calculated the Schmidt stability index (S) in February and compared it with hypolimnetic DO dynamics. Vertical water temperature profiles were calculated using a one‐dimensional model, and calculated temperatures and meteorological data were used to analyse annual fluctuations in water temperatures, thermocline depth, meteorological variables and S. We estimated that mean annual air and volume‐weighted water temperatures increased by 0.028 and 0.033 °C year−1, respectively, from 1978 to 2011. Between 1986 and 1990, S and water temperature increased abruptly, probably due to a large upwards trend in air temperature (+0.239 °C year−1). We hypothesize that a mixing regime that lacked overturn took effect at this time and that this regime lasted until 2011, when S was particularly small. These results demonstrate that abrupt climate warming in the late 1980s likely triggered the termination of complete mixing and caused the 21‐year period of successive anoxia in Lake Ikeda. We conclude that the lake response to a rapid shift in regional climate conditions was a key factor in changing the hypolimnetic water environment and that thermal stability in winter is a critical environmental factor controlling the mixing regime and anoxic conditions in deep lakes. Copyright © 2014 John Wiley & Sons, Ltd.

A new empirical procedure for estimating intra-annual heat storage changes in lakes and reservoirs: Review and analysis of 22 lakes

Evaporation is an important component of the water and energy balance of lakes and reservoirs. The energy balance combination method for estimating evaporation requires the heat storage changes (Qt) to be known. The lack of data on water temperature profiles and water depth fluctuations hinders routine computations of Qt. Following successful estimation of the soil heat flux density of land surfaces (G) and heat storage change of urban areas and wetlands from net all wave radiation (Rn), we investigated in this paper whether a similar generic Qt(Rn) empirical relationship can be developed for lakes and reservoirs. A comprehensive literature survey was conducted and experimental datasets for 22 lakes with different characteristics were collected. A linear Qt(Rn) model with a hysteresis function to describe seasonal warming and cooling effects was developed (Qt=a∗Rn+b+c∗dRn/dt) that fits the 22 independently gathered datasets satisfactory (R2 of 0.83 and RMSE of 22Wm−2) for bi-weekly and monthly time scales. Predictive models for the coefficients a, b and c were also developed, using Rn and water surface temperature measurements that can be retrieved from routine earth observation measurements. The average R2 between measured and modeled Qt was 0.84 and the RMSE was 37Wm−2 if predictive models were used for the assessment of lake specific Qt(Rn) functions. Two independent satellite-derived products were explored: the ARC-Lake (ATSR Reprocessing for Climate) product for water surface temperature using the ATSR (Along Track Scanning Radiometer) series data, and the CM SAF (Satellite Application Facility on Climate Monitoring) product for solar radiation Rs based on the AVHRR (Advanced Very High Resolution Radiometer) data. The proposed procedure using purely satellite-derived data as inputs resulted in comparably good Qt estimates as those using in-situ measurements. The new Qt hysteresis model can thus be applied together with satellite measurements for supporting the computation of evaporation from open water bodies based on energy balance equations.

Episodic events imposed on the seasonal nutrient dynamics of an upwelling system off northeastern Taiwan

An upwelling center has been frequently observed on the shelf break of the East China Sea (ECS) off northeastern Taiwan, where the Kuroshio encounters an abrupt shoaling topography. The region is also located under the track of Asian dust (AD) storms and frequently disturbed by typhoons. To examine the seasonal nutrient dynamics of the upwelling and the potential impacts of these episodic events, transect stations across the upwelling center were visited at intervals of 1–3months from November 2003 to January 2005. The results of the water temperature profiles indicated that the upwelling persisted throughout the year with the most intensified events occurring in winter. Seasonally, a higher nitrate concentration was observed during the stronger upwelling period. The highest nitrate value was however observed during an AD storm, with an average value of 8.3μM for the top 30m. Interestingly, the N/P ratio was larger than 16 during these episodic events, and the N/P ratios were equal to or smaller than 16 during other periods. On average, the estimated values from wet deposition constituted 17.3% of the total estimated nitrogen input. This suggests that atmospheric deposition, particularly during the episodic events, might be an important external nutrient source.

Developing an Effective Method to Determine the Deviation of F Value upon the Location of a Still Can during Convection Heating Using CFD and Subzones

AbstractA numerical simulation was applied to determine the temperature profiles of water in a can with a diameter of 52.3 mm and a height of 124.0 mm. Cold points at different heating times were determined, and the degree of pasteurization (F value) of each cold point was calculated. Subzones in both vertical and horizontal directions were introduced to determine the deviation of F value upon the location in the can during a convective heating, and the average F value of each subzone was estimated. The slow heating zone (SHZ) was determined by overwrapping the subzones with the lowest average F values in the vertical and horizontal direction. The cold point was continuously moved during the thermal treatment and even at 600 s, the SHZ determined by this subzone method maintained a single zone, unlike the cold points. The relative difference of F value between the SHZ and the cold point was approximately 0.575%. The subzone method is thus an effective way to determine the SHZ and F value, which is an indicator of the sterilization.Practical ApplicationsFor safety purposes, estimation of the degree of pasteurization is very important for the liquid food in a can. Determination of the slow heating zone (SHZ) and F value in the can is very difficult because of the convection flow during heating. Many previous studies indicated the importance of determining the SHZ for the liquid food in a can, but there was no clear advice to estimate the degree of pasteurization based on the temperature profile from the SHZ. This study suggested to use the subzones to estimate the SHZ and clearly demonstrate that the degree of pasteurization at the SHZ represented by the area average F value obtained from the subzone is more stable and consistent.

Microbial sulfate reduction within the Iheya North subseafloor hydrothermal system constrained by quadruple sulfur isotopes

Subseafloor hydrothermal systems may host spatially extended and numerically abundant microbial communities sustained by sulfate reduction as one of the important terminal electron accepting metabolisms. In order to estimate microbial sulfate reduction in a subseafloor hydrothermal regime, we analyzed sulfur isotopes (S32/S33/S34/S36) of pore-water sulfate and mineralized sulfide in the upper 100 m of sedimentary sequences at the Iheya North hydrothermal field in the Okinawa Trough recovered in Integrated Ocean Drilling Program Expedition 331 (IODP Exp 331). On the basis of the pore water chemistry and temperature profiles, the subseafloor environment is divided into three hydrogeologic units. In the topmost Unit-1, relatively fresh seawater is recharged, and the bottommost Unit-3 is characterized by predominance of endmember-like high-temperature hydrothermal fluid (>300 °C) underlying the impermeable cap rock layers. Intermediate Unit-2 is subject to mixing between the hydrothermal fluid and seawater. The δ34S values of sulfate in the Unit-2 mixing zone were found to be more 34S-enriched than the values expected from simple mixing model of seawater sulfate in the Unit-1 with the hydrothermal fluid in the Unit-3. The observed SSO434-enrichment and sulfate concentration [SO2−4]-depletion suggest sulfate reduction is taking place below the seafloor. Based on our model calculation, the isotope discrimination (ε34) is estimated to be −21‰. This large isotope discrimination together with slight Δ33S′ enrichment and Δ36S′ depletion reveals that sulfate reduction is caused by microbial processes but not by thermochemical processes. In addition, our numerical simulation points out that sulfate may be reduced prior to presently undergoing mixing with high-temperature fluid, probably within the seawater recharge zone. Despite the abundant input of hydrothermal H2S, mineralized sulfide below 10 m seafloor (mbsf) shows characteristic sulfur isotopic signatures that support the significant contribution of subseafloor microbial sulfate reduction, potentially corresponding to approximately 20% of the total sulfide mineral formation. Active microbial sulfate reduction below the seafloor may be promoted by significant input of seawater to the habitats through the vigorous hydrothermal circulation in vicinity of Iheya North field.

Passive acoustics embedded on gliders—Weather observation through ambient noise

Underwater gliders can provide high resolution water temperature and salinity profiles. Being able to associate them with a surface weather conditions estimation would allow to better study sea-air interactions. Since in-situ observations of the marine meteorological parameters are difficult, the development of a glider embedded weather sensor has been studied, based on the WOTAN approach. In the 1–30 kHz frequency range, the background underwater noise is dominated by wind generated noise. Focusing on the sound pressure level at 5, 8, 10, and 20 kHz allows to estimate the wind speed. Thus, deploying a glider with an embedded hydrophone gives an access to the surface weather conditions around its position. We have deployed gliders in the Mediterranean sea, with passive acoustic monitoring devices onboard. Four months of data have been recorded. Wind speed estimations have been confronted to weather buoys observations and atmospheric models predictions. Wind estimates have been obtained with a ~2 m/s error. A specific emphasis has been placed on the robustness of the processing through multi frequencies analysis and depth induced attenuation correction. A downscaling study has been performed on the acoustic sampling protocol, in order to meet the low energy consumption glider standards, for a future real time embedded processing. The glider generated noise and its vertical movement are not perturbing the estimation. Moreover, the surface behavior of the Slocum gliders allows an estimation of the wind direction.

Comparing ice and temperature simulations by four dynamic lake models in Harp Lake: past performance and future predictions

AbstractThe physical dynamics of lake temperature and ice phenology are important in the modelling and management of temperate aquatic ecosystems. One‐dimensional hydrothermal lake models have not been well evaluated in terms of how they simulate ice dynamics in particular. We chose four models (Hostetler, Minlake, Simple Ice Model or SIM and General Lake Model) to test and compare their performance modelling water temperature and ice dynamics using 16 years of field data from Harp Lake, an extensively studied inland lake in south‐central Ontario. Each model produced satisfactory water temperature profiles over the simulated period, with small differences in the model performance. Model fits for ice phenology and ice thickness were, however, considerably lower than those for water temperature, with Minlake generating the best agreement with observed ice‐on and ice‐off dates as well as ice thickness, followed by SIM. The responses of lake ice dynamics to future climate scenarios were simulated by running each of the four models for 91 years, from 2010 to 2100. The predicted decrease in ice season length was significantly different among models, varying between 30 and 81 days, with an average of 48 days. Corresponding decreases in ice thickness varied between 0.11 and 0.20 m, averaging 0.17 m. This study demonstrates that uncertainty due to model performance and selection is considerable, and further testing and refinement of hydrothermal lake dynamic models are needed to improve predictive abilities for ice dynamics. Copyright © 2014 John Wiley & Sons, Ltd.

Analysis of cirrus cloud spectral signatures in the far infrared

This paper analyses high spectral resolution downwelling radiance measurements in the far infrared in the presence of cirrus clouds taken by the REFIR-PAD interferometer, deployed at 3500m above the sea level at the Testa Grigia station (Italy), during the Earth COoling by WAter vapouR emission (ECOWAR) campaign. Atmospheric state and cloud geometry are characterised by the co-located millimeter-wave spectrometer GBMS and by radiosonde profile data, an interferometer (I-BEST) and a Raman lidar system deployed at a nearby location (Cervinia). Cloud optical depth and effective diameter are retrieved from REFIR-PAD data using a limited number of channels in the 820–960cm−1 interval. The retrieved cloud parameters are the input data for simulations covering the 250–1100cm−1 band in order to test our ability to reproduce the REFIR-PAD spectra in the presence of ice clouds. Inverse and forward simulations are based on the same radiative transfer code. A priori information concerning cloud ice vertical distribution is used to better constrain the simulation scheme and an analysis of the degree of approximation of the phase function within the radiative transfer codes is performed to define the accuracy of computations. Simulation-data residuals over the REFIR-PAD spectral interval show an excellent agreement in the window region, but values are larger than total measurement uncertainties in the far infrared. Possible causes are investigated. It is shown that the uncertainties related to the water vapour and temperature profiles are of the same order as the sensitivity to the a priori assumption on particle habits for an up-looking configuration. In case of a down-looking configuration, errors due to possible incorrect description of the water vapour profile would be drastically reduced.

Water Vapor Probabilistic Retrieval Using GNSS Signals

In this paper, we propose a novel Bayesian procedure to update the probability distribution for a set of possible atmospheric states, once ground measures of temperature, pressure, humidity, and tropospheric delay of Global Navigation Satellite System (GNSS) signals are made. It is based on a representative dataset of matching pairs of reanalysis atmospheric states and ground measures. By applying the basic rules of probability theory and logic inference, a computable expression for the conditional probability of the states given the measures is found. This allows us to select the most plausible atmospheric conditions, consistent with ground observations. Compared with more conventional techniques, the proposed approach has the advantage of always giving a result, even if not all the measures are available. Moreover, it provides the probability distributions of the retrieved quantities, which collapse to the corresponding prior distributions in the worst case of no significant measures. In any case, the final uncertainties are fully quantified, as needed for many meteorological applications, including data assimilation and ensemble forecasts for a numerical weather model. In addition to the theoretical details, a practical example of operational application, using a ten-year dataset on a Mediterranean test site, is also presented. The most probable retrieved atmospheric profiles of water vapor and temperature, as well as the corresponding values of precipitable water, are compared with balloon measurements on such a test site, showing good agreement and a significant improvement when the GNSS delay measure is added. In particular, the precipitable water retrieval turns out at least as accurate as that obtained with conventional approaches.

Development of local atmospheric model for estimating solar irradiance in Peninsular Malaysia

Incoming solar irradiance covers a wide range of wavelengths with different intensities which drives almost every biological and physical cycle on earth at a selective wavelength. Estimation of the intensities of each wavelength for the solar irradiance on the earth surface provides a better way to understand and predict the radiance energy. It requires that the atmospheric and geometric input and the availability of atmospheric parameter is always the main concern in estimating solar irradiance. In this study, a local static atmospheric model for Peninsular Malaysia was built to provide the atmospheric parameters in the estimation of solar irradiance. Ten years of monthly Atmospheric Infrared Sounder (AIRS) average data (water vapor, temperature, humidity and pressure profile) of the Peninsular Malaysia was used for the building of the atmospheric model and the atmospheric model were assessed based on the measured meteorological data with RMSE of 4.7% and 0.7k for both humidity and temperature respectively. The atmospheric model were applied on a well-established radiative transfer model namely SMARTS2. Some modifications are required in order to include the atmospheric model into the radiative transfer model. The solar irradiance results were then assessed with measured irradiance data and the results show that both the radiative transfer model and atmospheric model were reliable with RMSE value of 0.5 Wm−2. The atmospheric model was further validated based on the measured meteorological data (temperature and humidity) provided by the Department of Meteorology, Malaysia and high coefficient of determination with R2 value of 0.99 (RMSE value = 4.7%) and 0.90 (RMSE value = 0.7k) were found for both temperature and humidity respectively.

The water circulation near the Danube Delta and the Romanian coast modelled with finite elements

A numerical model, based on a finite element discretisation technique, was used to study water circulation in the Black Sea׳s north-western shelf, particularly near the Danube Delta and the Romanian coast. The numerical grid covers the entire Black Sea and the model resolution is gradually increased versus the Romanian coast to resolve both mesoscale and microscale hydrodynamic features. Sea level, water temperature and CTD profiles, collected in the north-western shelf, were used to validate the model. The seasonal and daily coastal hydrodynamics, in 2009, were studied using 3-D water current and salinity fields. Moreover, different numerical tracers were released on the Danube׳s arms to characterise the Danube׳s plume extension. Results show that near the Danube Delta the strong salinity stratification confines most of the wind momentum input to the surface water layer, while the subsurface current is mostly influenced by the open sea circulation. In the southern Romanian coast, the vertical salinity gradient is weaker and the action of the wind can reach deeper layers. The numerical tracers show a net predominance of the Kilia branch and how coastal anticyclonic eddies can trap the river freshwater, carrying it away from the coast. This happens especially in spring, when the Danube׳s discharge is high and a large eddy is active in front of the Kilia branch.