scholarly journals THE SKY RADIANCE AND LUMINANCE DISTRIBUTIONS ESTIMA TED BY GLOBAL IRRADIANCE AND DIFFUSE IRRADIANCE

2003 ◽  
Vol 68 (573) ◽  
pp. 33-40 ◽  
Author(s):  
Norio IGAWA ◽  
Hirohi NAKAMURA ◽  
Yasuko KOGA ◽  
Tomoko MATSUZAWA
Keyword(s):  
Global Irradiance ◽  
Diffuse Irradiance ◽  
Sky Radiance

scholarly journals Retrieval of Key Aerosol Optical Parameters from Spectral Direct and Diffuse Irradiances Observed by a Radiometer with Nonideal Cosine Response Characteristic

2012 ◽  
Vol 29 (5) ◽  
pp. 683-696 ◽  
Author(s):  
Pradeep Khatri ◽  
Tamio Takamura ◽  
Akihiro Yamazaki ◽  
Yutaka Kondo
Keyword(s):  
Direct Effect ◽  
Radiative Forcing ◽  
Response Characteristic ◽  
Single Scattering ◽  
Optical Parameters ◽  
Aerosol Radiative Forcing ◽  
Aerosol Direct Effect ◽  
Diffuse Irradiance ◽  
Isotropic Distribution ◽  
Sky Radiance

Abstract The spectral direct and diffuse irradiances observed by a radiometer with a horizontal surface detector have been frequently used to study aerosol optical parameters, such as aerosol optical thickness (τaer) and single scattering albedo (ω). Such radiometers more or less lack an ideal cosine response. Generally, either the cosine error of observed diffuse irradiance was corrected by assuming an isotropic distribution of sky radiance or it was neglected in the past studies. This study presents an algorithm to retrieve τaer and ω from direct and diffuse irradiances observed by a radiometer with a nonideal cosine response characteristic by taking into account the cosine errors of observed irradiances in detail. The proposed algorithm considers the anisotropic distribution of sky radiance while correcting the cosine error of observed diffuse irradiance. This algorithm can also be used to calculate the cosine error correction factor of diffuse irradiance. The results show that the aerosol optical parameters and the aerosol direct effect (aerosol radiative forcing and the heating rate) can be heavily affected by the cosine errors of observed direct and diffuse irradiances. The study further shows that assuming the isotropic distribution of sky radiance while correcting the cosine error of observed diffuse irradiance can affect the retrieved ω at small and large solar zenith angles; thus, the estimated aerosol direct effect can be quantitatively affected. Because of the cosine errors, this study found the actual values of diffuse irradiances at different wavelengths were underestimated by around 5%–11%.

Evaluation of a New Photodiode Sensor for Measuring Global and Diffuse Irradiance, and Sunshine Duration

2003 ◽  
Vol 125 (1) ◽  
pp. 43-48 ◽  
Author(s):  
John Wood ◽  
Tariq Muneer ◽  
J. Kubie
Keyword(s):  
Standard Error ◽  
Sunshine Duration ◽  
New Device ◽  
Global Irradiance ◽  
Diffuse Irradiance ◽  
Reference Measure ◽  
Irradiance Data ◽  
Stable Performance ◽  
Integrated Device ◽  
Story Building

A new integrated device (called the BF3) has been developed, which enables the simultaneous measurement of horizontal global and diffuse irradiance as well as sunshine presence at any time. The sensor needs no specific polar alignment or routine adjustment, and works at any latitude. To evaluate the performance of this new device, a BF3 sensor was installed on the roof of a six-story building in the Merchiston Campus of Napier University, Edinburgh from February 22–July 3, 2001. Horizontal global and diffuse irradiance data were collected from the BF3. To enable a cross check, two Kipp and Zonen CM11 sensors, one with a shade ring, have also been installed beside the BF3 sensor on the same roof. These were used to give a reference measure of the horizontal global and diffuse irradiance. To evaluate the BF3 sunshine duration performance, the direct beam normal irradiance was calculated from the CM11 global and diffuse readings, and compared with a threshold of 120W.m−2 to give sunshine presence according to the WMO definition. This was compared against the BF3 output, and also with data from two Campbell-Stokes sunshine recorders on the same site. The results show a stable performance on the part of the BF3 sensor for the measurement of horizontal global and diffuse irradiance. The global irradiance measured by the BF3 showed values 4.7% high, with a standard error of 16.5W.m−2 compared to the Kipp and Zonen sensors. Diffuse values were 1.4% high with a standard error of 13.4W.m−2. The BF3 sunshine duration was within 2% of that calculated from the WMO definition over the study period, with a typical daily error of less than 20 min. This is well within the WMO requirements for a sunshine recorder. In comparison, the Campbell-Stokes recorders gave readings up to 7% different from the WMO values, with a typical daily error of almost an hour.

scholarly journals Spectral UV Measurements of Global Irradiance, Solar Radiance, and Actinic Flux in New Zealand: Intercomparison between Instruments and Model Calculations

2008 ◽  
Vol 25 (6) ◽  
pp. 945-958 ◽  
Author(s):  
Mario Blumthaler ◽  
Barbara Schallhart ◽  
Michael Schwarzmann ◽  
Richard McKenzie ◽  
Paul Johnston ◽  
...  
Keyword(s):  
New Zealand ◽  
Total Ozone ◽  
Spectral Irradiance ◽  
Atmospheric Composition ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Total Ozone Mapping Spectrometer ◽  
Model Calculations ◽  
Global Irradiance ◽  
Sky Radiance

Abstract Presented here are the results of a short but intense measurement campaign at Lauder, New Zealand, in which spectral irradiance from instruments operated by the National Institute of Water and Atmospheric Research (NIWA) and Austria/Innsbruck (ATI) were traced to different irradiance standards and compared. The observed spectral differences for global irradiance were relatively small (<5%) and were consistent with those expected from observed differences in the radiation standards used by each group. Actinic fluxes measured by both groups were also intercompared and found to agree at the 10% level. The ATI instrument had the additional capability of measuring solar direct beam irradiance and sky radiances. These provided the first series of sky radiance measurements at this pristine Network for the Detection of Atmospheric Composition Change (NDACC) site. The polarization of sky radiance results were compared with estimates from a radiative transfer model without any aerosols and was found to be up to 25% smaller. Total ozone values derived from Total Ozone Mapping Spectrometer (TOMS), Dobson measurements by NIWA, spectral direct sun measurements by ATI, and spectral global irradiance measurements by NIWA agreed generally within 2%–3%.

scholarly journals Global and diffuse solar radiant exposures at Pone

MAUSAM ◽  
2021 ◽  
Vol 51 (4) ◽  
pp. 349-358
Author(s):  
R. R. SHENDE ◽  
V. R. CHIVATE
Keyword(s):  
Atmospheric Transmission ◽  
Rainfall Distribution ◽  
Monsoon Period ◽  
Global Irradiance ◽  
Radiation Data ◽  
Diffuse Irradiance ◽  
Radiation Measurements

Radiation measurements are being carried out at Pune since 1957. The radiation data for the period 1986-90 are studied here with reference to general sky condition and rainfall distribution. Global irradiances show a decrease of about 5 per cent over the last four decades, The diffuse irradiation contributes about 23 per cent to the global irradiance during winter months, Its proportion increases to more than 70 per cent during the monsoon period. The specific rainfall distribution affects both global and diffuse irradiances but in opposite directions, The diffuse irradiance shows increases as the atmospheric transmission decreases, However, the changes found have not become statistically highly significant as yet.

scholarly journals Effect of Mechanical Ventilation on the Thermal Offset of Pyranometers during Cloud-Free Summer Conditions

2017 ◽  
Vol 34 (5) ◽  
pp. 1155-1173 ◽  
Author(s):  
G. Sanchez ◽  
A. Serrano ◽  
M. L. Cancillo
Keyword(s):  
Mechanical Ventilation ◽  
Solar Radiation ◽  
Solar Zenith Angle ◽  
Large Range ◽  
Absolute Value ◽  
Operational Conditions ◽  
Global Irradiance ◽  
Diffuse Irradiance ◽  
The Impact ◽  
Radiation Measurements

AbstractThermal offset is a significant source of uncertainty for solar radiation measurements. This study assesses the influence of mechanical ventilation on the daytime thermal offset of pyranometers. Toward this goal, an intensive unprecedented campaign of measurements was conducted in Badajoz, Spain, during four selected summer days under cloud-free conditions, covering a large range of solar zenith angle, irradiance, and temperature. Three leading manufacturers participated in the campaign, providing secondary standard pyranometers and compatible ventilation units. The thermal offset was experimentally measured following the capping methodology. A total of 372 capping events were conducted, the largest number ever reported in the literature. Each pyranometer was tested under different operational conditions (with/without ventilation and measuring global/diffuse irradiance). Results show that mechanical ventilation generally reduces the thermal offset. The magnitude of this reduction is different for each pyranometer model and depends on whether the instrument is shadowed (for measuring diffuse irradiance) or not (for measuring global irradiance). Mechanical ventilation tends to homogenize the temperature around the pyranometer and therefore reduces the impact of environmental conditions on the thermal offset. CMP11 and SPP pyranometers show notable tendencies in the thermal offset even when mechanical ventilation is applied. The Dutton et al. model, which aimed to correct the daytime thermal offset, is evaluated. Results show this model performs well for the SPP pyranometer but underestimates the absolute value of thermal offset for the CMP11 and SR20 pyranometers.

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