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Retrieving vertical ozone profiles from measurements of global spectral irradiance
摘要： A new method is presented to determine vertical ozone profiles from measurements of spectral global (direct Sun plus upper hemisphere) irradiance in the ultraviolet. The method is similar to the widely used Umkehr technique, which inverts measurements of zenith sky radiance. The procedure was applied to measurements of a high-resolution spectroradiometer installed near the centre of the Greenland ice sheet. Retrieved profiles were validated with balloon-sonde observations and ozone profiles from the space-borne Microwave Limb Sounder (MLS). Depending on altitude, the bias between retrieval results presented in this paper and MLS observations ranges between ?5 and +3 %. The magnitude of this bias is comparable, if not smaller, to values reported in the literature for the standard Dobson Umkehr method. Total ozone columns (TOCs) calculated from the retrieved profiles agree to within 0.7±2.0 % (±1σ) with TOCs measured by the Ozone Monitoring Instrument on board the Aura satellite. The new method is called the “Global-Umkehr” method.
关键词： atmospheric composition,spectral irradiance,ozone profiles,UV monitoring,Umkehr technique
更新于2025-09-09 09:28:46
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[ACM Press the 10th International Conference - Sydney, Australia (2018.01.08-2018.01.10)] Proceedings of the 10th International Conference on Computer Modeling and Simulation - ICCMS 2018 - Mathematical Modeling the Irradiance of Multiple Upper-Room Ultraviolet Germicidal Fixtures for Airborne Pathogens Disinfection
摘要： Upper-room ultraviolet germicidal (UR-UVGI) fixture has been recommended as one of choices for preventing the transmission of the airborne pathogens in poor ventilated room. To theoretically predict the irradiance of multiple UR-UVGI fixtures is key importance for the practical evaluation of their disinfection efficiencies. In this study, a mathematical model based on the view factor approach from radiative heat transfer was developed to predict the irradiance of multiple UR-UVGI fixtures. In the model, the reflector and tedious fixture were simplified as a fictitious surface and the shading effect of the louvers was considered. The model was validated by the literature experiment case. It should be instrumental for the design of the UR-UVGI disinfection system.
关键词： View factor,Irradiance,Ultraviolet germicidal lamp,Disinfection
更新于2025-09-09 09:28:46
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[ACM Press the 1st International Workshop - New Delhi, India (2018.10.29-2018.10.29)] Proceedings of the 1st International Workshop on Communication and Computing in Connected Vehicles and Platooning - C3VP '18 - On Feasibility of VLC Based Car-to-Car Communication Under Solar Irradiance and Fog Conditions
摘要： This paper investigates the impact of solar irradiance and fog condition on visible light communication (VLC) based car-to car (C2C) communication for two capital cities, New Delhi and London. The bit error rate (BER) variation over a day has been compared for both the cities for the month of March, June and December. It has been shown that for a given BER threshold performance, the impact of solar irradiance is more pronounced in month of June especially at New Delhi when solar irradiance reaches its peak. It has also been shown that in month of December, fog is one of the most significant climatic factors that greatly influences the VLC based C2C communication in terms of atmospheric attenuation. This paper also establishes the relationship for the minimum safety distance required between cars based on two-second rule, car speed and angle between cars. The minimum safety distance which would be required to avoid any rear-end collision especially during light or dense fog in the month of December has also been compared for New Delhi and London.
关键词： safety distance,fog conditions,solar irradiance,car-to-car communication,visible light communication,bit error rate
更新于2025-09-09 09:28:46
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Cloud height and tracking accuracy of three all sky imager systems for individual clouds
摘要： Solar irradiance nowcasts can be derived with sky images from all sky imagers (ASI) by detecting and analyzing transient clouds, which are the main contributor of intra-hour solar irradiance variability. The accuracy of ASI based solar irradiance nowcasting systems depends on various processing steps. Two vital steps are the cloud height detection and cloud tracking. This task is challenging, due to the atmospheric conditions that are often complex, including various cloud layers moving in di?erent directions simultaneously. This challenge is addressed by detecting and tracking individual clouds. For this, we developed two distinct ASI nowcasting approaches with four or two cameras and a third hybridized approach. These three systems create individual 3-D cloud models with unique attributes including height, position, size, optical properties and motion. This enables us to describe complex multi-layer conditions. In this paper, derived cloud height and motion vectors are compared with a reference ceilometer (height) and shadow camera system (motion) over a 30 day validation period. The validation data set includes a wide range of cloud heights, cloud motion patterns and atmospheric conditions. Furthermore, limitations of ASI based nowcasting systems due to image resolution and image perspective constrains are discussed. The most promising system is found to be the hybridized approach. This approach uses four ASIs and a voxel carving based cloud modeling combined with a cloud segmentation independent stereoscopic cloud height and tracking detection. We observed for this approach an overall mean absolute error of 648 m for the height, 1.3 m/s for the cloud speed and 16.2° for the motion direction.
关键词： Cloud height,Cloud tracking,Nowcasting,Irradiance map,All sky imager,3-D cloud modeling
更新于2025-09-09 09:28:46
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Cloud shadow speed sensor
摘要： Changing cloud cover is a major source of solar radiation variability and poses challenges for the integration of solar energy. A compact and economical system is presented that measures cloud shadow motion vectors to estimate power plant ramp rates and provide short-term solar irradiance forecasts. The cloud shadow speed sensor (CSS) is constructed using an array of luminance sensors and a high-speed data acquisition system to resolve the progression of cloud passages across the sensor footprint. An embedded microcontroller acquires the sensor data and uses a cross-correlation algorithm to determine cloud shadow motion vectors. The CSS was validated against an artificial shading test apparatus, an alternative method of cloud motion detection from ground-measured irradiance (linear cloud edge, LCE), and a UC San Diego sky imager (USI). The CSS detected artificial shadow directions and speeds to within 15? and 6 % accuracy, respectively. The CSS detected (real) cloud shadow directions and speeds with average weighted root-mean-square difference of 22? and 1.9 m s?1 when compared to USI and 33? and 1.5 m s?1 when compared to LCE results.
关键词： cloud motion vectors,solar irradiance,cloud shadow speed sensor,forecasting,solar energy
更新于2025-09-09 09:28:46
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Workshop on Lunar Calibration for Satellite Remote Sensing
摘要： Tracking climate variables at the levels of precision and accuracy required to detect global change requires satellite sensors to make highly consistent measurements that can be compared to measurements made at different times and with different instruments. Gaps in climate data records, such as those resulting from launch delay or instrument failure, and inconsistencies in radiometric scales between satellites can introduce unnecessary measurement error and thus undermine the credibility of fundamental climate data records. To address these issues, leading experts in satellite remote sensing and lunar observation and modeling assembled at the National Institute of Standards and Technology from 12-15 May 2012 for a workshop to discuss the utility of and strategies for using the Moon to calibrate satellite remote sensing measurements. This report summarizes the outcome of the workshop, including suggested steps to maximize the value of the Moon as an exoatmospheric calibration source for satellite remote sensing.
关键词： lunar spectral irradiance,remote sensing,calibration,moon,radiometry
更新于2025-09-09 09:28:46
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SmartPatch: A Self-Powered and Patchable Cumulative UV Irradiance Meter
摘要： Ultraviolet (UV) irradiance affects human bodies both positively and negatively. We introduce SmartPatch, a self-powered, small-form-factor, light-weight, low-cost, and a patch-type UV meter, that provides a scienti?c measure of UV irradiation on a particular skin area. It is powered by a tiny PV (photovoltaic) cell without a battery and a power converter and performs UI (user interface) without a physical switch.
关键词： UV irradiance meter,Ultraviolet,dynamic power management,skin damage
更新于2025-09-09 09:28:46
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The spectral signature of cloud spatial structure in shortwave irradiance
摘要： We found that cloud spatial structure manifests itself as spectral signature in shortwave irradiance fields – specifically in transmittance and net horizontal photon transport in the visible and near-ultraviolet wavelength range. In this paper, we demonstrate this through radiative transfer calculations with cloud imagery from a field experiment, and show that such three-dimensional effects may occur on scales up to 60 kilometers. Neglecting net horizontal photon transport leads to a transmittance bias on the order of ±12-19% even at the relatively coarse spatial resolution of 20 kilometers, and of more than ±50% for 1 kilometer. This poses a problem for radiative energy budget estimates from space because the bias for any pixel depends on its spatial context in a non-trivial way. The key for solving this problem may lie in the spectral dimension, since we found a robust correlation between the magnitude of net horizontal photon transport (H) and its spectral dependence (slope). It is scale-invariant and holds for the entire pixel population of a domain. This was at first surprising given the large degree of spatial inhomogeneity, but seems to be valid for any cloud field. We prove that the underlying physical mechanism for this phenomenon is molecular scattering in conjunction with cloud inhomogeneity. On this basis, we developed a simple parameterization through a single parameter ??, which quantifies the characteristic spectral signature of spatial heterogeneities. In a companion paper, we will show that it is accompanied by spectral radiance perturbations, which can be detected from multi-spectral imagers and may be translated into bias reductions for cloud radiative effect estimates in the future.
关键词： cloud spatial structure,molecular scattering,shortwave irradiance,spectral signature,radiative transfer,cloud radiative effect,horizontal photon transport
更新于2025-09-04 15:30:14
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Autonomous marine hyperspectral radiometers for determining solar irradiances and aerosol optical properties
摘要： We have developed two hyperspectral radiometer systems which require no moving parts, shade rings or motorised tracking, making them ideally suited for autonomous use in the inhospitable remote marine environment. Both systems are able to measure direct and diffuse hyperspectral irradiance in the wavelength range 350–1050 nm at 6 nm (Spectrometer 1) or 3.5 nm (Spectrometer 2) resolution. Marine field trials along a 100? transect (between 50? N and 50? S) of the Atlantic Ocean resulted in close agreement with existing commercially available instruments in measuring (1) photosynthetically available radiation (PAR), with both spectrometers giving regression slopes close to unity (Spectrometer 1: 0.960; Spectrometer 2: 1.006) and R2 ～ 0.96; (2) irradiant energy, with R2～ 0.98 and a regression slope of 0.75 which can be accounted for by the difference in wavelength integration range; and (3) hyperspectral irradiance where the agreement on average was between 2 and 5 %. Two long duration land-based field campaigns of up to 18 months allowed both spectrometers to be well calibrated. This was also invaluable for empirically correcting for the wider field of view (FOV) of the spectrometers in comparison with the current generation of sun photometers (～ 7.5? compared with ～ 1?). The need for this correction was also confirmed and independently quantified by atmospheric radiative transfer modelling and found to be a function of aerosol optical depth (AOD) and solar zenith angle. Once Spectrometer 2 was well calibrated and the FOV effect corrected for, the RMSE in retrievals of AOD when compared with a CIMEL sun photometer were reduced to ～ 0.02–0.03 with R2 > 0.95 at wavelengths 440, 500, 670 and 870 nm. Corrections for the FOV as well as ship motion were applied to the data from the marine field trials. This resulted in AOD500 nm ranging between 0.05 in the clear background marine aerosol regions and ～ 0.5 within the Saharan dust plume. The RMSE between the handheld Microtops sun photometer and Spectrometer 2 was between 0.047 and 0.057 with R2 > 0.94.
关键词： hyperspectral radiometer,autonomous measurement,marine environment,solar irradiance,aerosol optical depth
更新于2025-09-04 15:30:14
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Light regulation of vitamin C in tomato fruit is mediated through photosynthesis
摘要： Higher levels of irradiance result in higher accumulation of ascorbate in leaves and fruits. Photosynthesis and respiration are an integral part of the physiological mechanism of light regulation of ascorbate in leaves, but little is known about the light regulation of ascorbate in fruit. The aim of this study was to investigate whether fruit illumination alone is sufficient for ascorbate increase in tomato fruit and whether this light signal is mediated by respiration and photosynthesis. First the changes of ascorbate with the progress of fruit development were investigated and subsequently detached fruit of different tomato genotypes were exposed to different irradiances and spectra. Measurements were performed on ascorbate, respiration, photosynthesis and chlorophyll content of the fruit. When attached to the plant, there was no effect of development on ascorbate from the mature green to the red stage. Detached fruit stored in darkness did not accumulate ascorbate. However, when exposed to 300-600 μmol m-2 s-1 light detached mature green fruit (photosynthetically active) substantially accumulated ascorbate, while mature red fruit (non-photosynthetically active) did not respond to light. Photosynthesis correlated with this increase of ascorbate while no correlation between respiration and ascorbate was found. Spectral effects on ascorbate in detached tomato fruit were limited. These results indicate that the signal for light regulation of ascorbate is perceived locally in the fruit and that fruit illumination alone is sufficient for a considerable increase in ascorbate levels for as long as the fruit contains chlorophyll. It is shown that photosynthetic activity of the fruit is an integral part of the response of ascorbate to light in tomato fruit. The light induced increase in ascorbate levels occurred in a range of genotypes, indicating a universal effect of light to ascorbate in tomato fruit.
关键词： photosynthesis,respiration,vitamin C,irradiance,ascorbic acid,spectrum
更新于2025-09-04 15:30:14