The 1995 North American Interagency Intercomparison of Ultraviolet Monitoring Spectroradiometers

Concern over stratospheric ozone depletion has prompted several government agencies in North America to establish networks of spectroradiometers for monitoring solar ultraviolet irradiance at the surface of the Earth. To assess the ability of spectroradiometers to accurately measure solar ultraviolet irradiance, and to compare the results between instruments of different monitoring networks, the second North American Intercomparison of Ultraviolet Monitoring Spectroradiometers was held June 12 to 23, 1995 at Table Mountain outside Boulder, Colorado, USA. This Intercomparison was coordinated by the National Institute of Standards and Technology (NIST) and the National Oceanic and Atmospheric Administration (NOAA). Participating agencies were the Environmental Protection Agency; the National Science Foundation; the Smithsonian Environmental Research Center; the Department of Agriculture; and the Atmospheric Environment Service, Canada. Instruments were characterized for wavelength uncertainty, bandwidth, stray-light rejection, and spectral irradiance responsivity, the latter with a NIST standard lamp operating in a specially designed field calibration unit. The spectral irradiance responsivity, determined once indoors and twice outdoors, demonstrated that while the responsivities changed upon moving the instruments, they were relatively stable when the instruments remained outdoors. Synchronized spectral scans of the solar irradiance were performed over several days. Using the spectral irradiance responsivities determined with the NIST standard lamp and three different convolution functions to account for the different bandwidths of the instruments, the measured solar irradiances generally agreed to within 3 %.     

An International Comparison of Absolute Radiant Power Measurement Capabilities

We report the results of an intercomparison of monochromatic radiant power measurement capabilities recently completed by 11 national laboratories. The intercomparison radiometers, distributed in pairs, included an amplifier with six decades of precision gain and one of two types of silicon photodiode (pn or np-type construction). Eleven of the laboratories measured the absolute responsivity of the radiometers at 633 nm and nine at 488 nm. The standard deviation of the overall difference was 0.36% at both wavelengths. The agreement between the various participating laboratories and NIST was within the measurement accuracy stated by the participants.     

车载测风激光雷达风廓线同步观测实验

多普勒测风激光雷达能够实现高时空分辨率的大气风场测量,中国海洋大学成功研制了可以测量风廓线和三维大气风场的车载多普勒测风激光雷达,并已交付中国气象局使用。为了检验该激光雷达的测量性能,2011年春季开展了车载激光雷达与探空气球风廓线同步观测实验,获取了55组比对数据。本文介绍了此次同步观测实验,给出了激光雷达和探空气球风廓线数据的比对个例,并对所有比对数据进行了统计分析。同步比对结果显示,激光雷达与探空气球风廓线数据的风速均方根偏差为2.76 m/s。通过分析比对偏差,证明了激光雷达风廓线测量结果的准确性。     

The RAMI On-line Model Checker (ROMC): A web-based benchmarking facility for canopy reflectance models

The exploitation of global Earth Observation data hinges increasingly on physically-based radiative transfer (RT) models. These models simulate the interactions of solar radiation within a given medium (e.g., clouds, plant canopies) and are used to generate look-up-tables that are embedded into quantitative retrieval algorithms, such as those delivering the operational surface products for MODIS, MISR and MERIS. An assessment of the quality of canopy RT models thus appears essential if accurate and reliable information is to be derived from them. Until recently such an undertaking was a time consuming and labour intensive process that was made even more challenging by the general lack of absolute reference standards. Several years of benchmarking activities in the frame of the RAdiation transfer Model Intercomparison (RAMI) exercise have now led to the development of the RAMI On-line Model Checker (ROMC). The ROMC is a web-based tool allowing model developers and users to autonomously assess the performance of canopy RT models (http://romc.jrc.ec.europa.eu/). Access to the ROMC is free and enables users to obtain both statistical and graphical indications as to the performance of their canopy RT model. In addition to providing an overall indication of the skill of a given model to correctly match the reference data, the ROMC allows also for interactive comparison/evaluations of different model versions/submissions of a given user. All ROMC graphs can be downloaded in PostScript format and come with a reference number for easy usage in presentations and publications. It is hoped that the ROMC will prove useful for the RT modeling community as a whole, not only by providing a convenient means to evaluate models outside the triennial phases of RAMI but also to attract participation in future RAMI activities.     

Overview of pressure coefficient data in building energy simulation and airflow network programs

Wind pressure coefficients (C_p) are influenced by a wide range of parameters, including building geometry, facade detailing, position on the facade, the degree of exposure/sheltering, wind speed and wind direction. As it is practically impossible to take into account the full complexity of pressure coefficient variation, building energy simulation (BES) and Airflow network (AFN) programs generally incorporate it in a simplified way. This paper provides an overview of pressure coefficient data and the extent to which they are currently implemented in BES–AFN programs. A distinction is made between primary sources of C_p data, such as full-scale measurements, reduced-scale measurements in wind tunnels and computational fluid dynamics (CFD) simulations, and secondary sources, such as databases and analytical models. The comparison between data from secondary sources implemented in BES–AFN programs shows that the C_p values are quite different depending on the source adopted. The two influencing parameters for which these differences are most pronounced are the position on the facade and the degree of exposure/sheltering. The comparison of C_p data from different sources for sheltered buildings shows the largest differences, and data from different sources even present different trends. The paper concludes that quantification of the uncertainty related to such data sources is required to guide future improvements in C_p implementation in BES–AFN programs.     

三台测氡仪的现场比对测量及分析

介绍了一次室内氡测量现场比对。三台氡测量仪取样位置相近,测量时间18h·三台仪器相对偏差小于25%,但1h的数据波动较大。     

Determination of low level trans unsaturation in physically refined vegetable oils by capillary GLC — Results of 3 intercomparison studies

The analytical performance of capillary gas‐liquid chromatographic (GLC) methods for the quantitative determination of trans fatty acids (TFA) in physically refined rapeseed and soybean oils was evaluated by 3 intercomparison studies. The participants were allowed to use their own methodology regarding derivatization and GLC conditions and were not requested to follow a fixed method protocol. However, certain requirements relating to the separation efficiency (chromatographic separation of critical pairs) and the accuracy (validation of the response factors using a certified reference material) of the method(s) applied, had to be fulfilled. All 12 participating laboratories employed fused silica capillary columns coated with cyanopropyl polysiloxane for the separation of fatty acid methyl esters. Analytical precision was sufficient (relative standard deviation for reproducibility 13%) for the quantification of trans isomers occurring at levels >0.1 g/100 g in physically refined vegetable oils, i.e. trans isomers of linolenic acid. For TFA levels <0.1 g/100 g (trans isomers of oleic and linoleic acid) precision dropped sharply (relative standard deviation for reproducibility >30%).     

The 1994 North American Interagency Intercomparison of Ultraviolet Monitoring Spectroradiometers

Concern over stratospheric ozone depletion has prompted several government agencies in North America to establish networks of spectroradiometers for monitoring solar ultraviolet irradiance at the surface of the Earth. To assess the ability of spectroradiometers to accurately measure solar ultraviolet irradiance, and to compare the results between instruments of different monitoring networks, the first North American Intercomparison of Ultraviolet Monitoring Spectroradiometers was held September 19–29, 1994 at Table Mountain outside Boulder, Colorado, USA. This Intercomparison was coordinated by the National Institute of Standards and Technology and the National Oceanic and Atmospheric Administration (NOAA). Participating agencies were the Environmental Protection Agency, National Science Foundation, Smithsonian Environmental Research Center, and Atmospheric Environment Service, Canada. Instruments were characterized for wavelength accuracy, bandwidth, stray-light rejection, and spectral irradiance responsivity, the latter with a NIST standard lamp calibrated to operate in the horizontal position. The spectral irradiance responsivity was determined once indoors and twice outdoors, and demonstrated that, while the responsivities changed upon moving the instruments, they were relatively stable when the instruments remained outdoors. Synchronized spectral scans of the solar irradiance were performed over several days. Using the spectral irradiance responsivities determined with the NIST standard lamp, and a simple convolution technique to account for the different bandwidths of the instruments, the measured solar irradiances agreed within 5 %.     

A Compendium on the NIST Radionuclidic Assays of the Massic Activity of 63Ni and 55Fe Solutions Used for an International Intercomparison of Liquid Scintillation Spectrometry Techniques

The National Institute of Standards and Technology recently participated in an international measurement intercomparison for ⁶³Ni and ⁵⁵Fe, which was conducted amongst principal national radionuclidic metrology laboratories. The intercomparison was sponsored by EUROMET, and was primarily intended to evaluate the capabilities of liquid scintillation (LS) spectrometry techniques for standardizing nuclides that decay by low-energy β-emission (like ⁶³Ni) and by low-Z (atomic number) electron capture (like ⁵⁵Fe). The intercomparison findings exhibit a very good agreement for ⁶³Ni amongst the various participating laboratories, including that for NIST, which suggests that the presently invoked LS methodologies are very capable of providing internationally-compatible standardizations for low-energy β-emitters. The results for ⁵⁵Fe are in considerably poorer agreement, and demonstrated the existence of several unresolved problems. It has thus become apparent that there is a need for the various international laboratories to conduct rigorous, systematic evaluations of their LS capabilities in assaying radionuclides that decay by low-Z electron capture.     

A Limited International Intercomparison of Responsivity Scales at Fiber Optic Wavelengths

We report here on a recent limited international intercomparison of responsivity scales at wavelengths of interest to the optical communications community. Participants in the comparison were the national laboratories in the United States, the United Kingdom, Germany, and Australia. The wavelengths tested were 1300 and 1550 nm. Data taken at 850 nm are only briefly discussed. The disagreement between the national laboratories’ responsivity scale is comfortably within the uncertainty claimed by each laboratory.