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This paper reports about a novel approach to the absolute intensity calibration of an electron cyclotron emission (ECE) spectroscopy system. Typically, an ECE radiometer consists of tens of separated frequency channels corresponding to different plasma locations. An absolute calibration of the overall diagnostic including near plasma optics and transmission line is achieved with blackbody sources at LN2 temperature and room temperature via a hot/cold calibration mirror unit. As the thermal emission of the calibration source is typically a few thousand times lower than the receiver noise temperature, coherent averaging over several hours is required to get a sufficient signal to noise ratio. A forward model suitable for any radiometer calibration using the hot/cold method and a periodic switch between them has been developed and used to extract the voltage difference between the hot and cold temperature source via Bayesian analysis. In contrast to the classical analysis which evaluates only the reference temperatures, the forward model takes into account intermediate effective temperatures caused by the finite beam width and thus uses all available data optimally. This allows the evaluation of weak channels where a classical analysis would not be feasible, is statistically rigorous, and provides a measurement of the beam width. By using a variance scaling factor, a model sensitive adaptation of the absolute uncertainties can be implemented, which will be used for the combined diagnostic Bayesian modeling analysis.

Strong scattering of high-power millimeter waves at 140 GHz has been shown to take place in heating and current-drive experiments at TEXTOR when a tearing mode is present in the plasma. The scattering signal is at present supposed to be generated by the parametric decay instability. Here we describe the heterodyne detection system used to characterize the newly discovered signal measured at TEXTOR, and we present spectral shapes in which the signal can appear under different conditions. The radiation is collected by the receiver through a quasi-optical transmission line that is independent of the electron cyclotron resonance heating transmission line, and so the scattering geometry is variable. The signal is detected with 42 frequency channels ranging from 136 to 142 GHz. We demonstrate that the large signal does not originate from gyrotron spurious radiation. The measured signal agrees well with independent backscattering radiometer data.

UV reconstruction is a method of estimation of surface UV with the use of available actinometrical and aerological measurements. UV reconstruction is necessary for the study of long‐term UV change. A typical series of UV measurements is not longer than 15 years, which is too short for trend estimation. The essential problem in the reconstruction algorithm is the good parameterization of clouds. In our previous algorithm we used an empirical relation between Cloud Modification Factor (CMF) in global radiation and CMF in UV. The CMF is defined as the ratio between measured and modelled irradiances. Clear sky irradiance was calculated with a solar radiative transfer model. In the proposed algorithm, the time variability of global radiation during the diurnal cycle is used as an additional source of information. For elaborating an improved reconstruction algorithm relevant data from Legionowo [52.4 N, 21.0 E, 96 m a.s.l], Poland were collected with the following instruments: NILU‐UV multi channel radiometer, ...

In this paper, results from the partition of downward surface solar radiation between direct and diffuse components under distinct aerosol loadings will be presented. The field experiment was conducted during 2007 dry season in the Reserva Biologica do Jaru, located in the Southwestern portion of the Amazon Basin (−10.145°, −61.908°), in a region with tropical rainforest vegetation. A Multi‐Filter Rotating Shadow‐band Radiometer (MFRSR) was used to measure global and diffuse components of solar radiation in narrow bands (centered at 415, 670, 870 and 1036 nm) as well as broadband (from about 350 to 1100 nm) spectral regions. Due to biomass burning emissions, high values of aerosol optical depth were observed (accompanying paper by Rosario et al., 2008). Consequently, a significant increase in diffuse solar irradiance was also observed. For example, at channel around 670 nm, the diffuse fraction corresponded to about 80%, even at noon, for aerosol optical depth of about 2 at the same wavelength, which is e...

The earth’s radiant energy budget is a balance between absorbed solar radiation and emitted outgoing longwave radiation (OLR). For almost 50 years now, accurate, long term records of solar insolation, planetary albedo, and OLR have been collected to monitor climate change. This paper describes results of two closure studies: one tests how well a state of the art radiative model using satellite retrievals from Atmospheric Infrared Sounder (AIRS) reproduces clear sky observations of OLR obtained by the Clouds and the Earth’s Radiant Energy System (CERES) broadband radiometer, and the other tests how well the AIRS retrievals input into the radiative model reproduces AIRS radiances. In both studies the methodologies were tested at the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) program site in the US Southern Great Plains (SGP) then applied globally. The clear sky OLR comparisons were impressive; RRTM calculations agree with CERES observations to ∼1 W/m2 with an uncertainty of ∼1 W/m2 a...

The absorption of short wave incoming solar radiation by the organic component of aerosols has been examined by using data from the MCMA‐2003 and the 2006 MILAGRO field campaigns. Both field efforts took place in and around Mexico City. Single Scattering Albedo (SSA) was derived as a function of wavelength (300–870 nm) by combining irradiance measurements from a Multi‐Filter Rotating Shadowband Radiometer (MFRSR) and spectrally resolved actinic flux measurements by spectroradiometry with a radiative transfer model (TUV). In addition, organic aerosol mass measured by a surface deployed aerodyne aerosol mass spectrometer was used to estimate the Mass Absorption Cross‐section (MAC) of Organic Carbon (OC). It was found that the MAC for OC is about 10.5 m2/g at 300 nm and falls close to zero at about 500 nm; these values are roughly consistent with previous MAC estimates of OC, and present first in‐situ observations of this quantity.

An intensive measurement campaign aiming to study Photosynthetically Active Radiation profiles inside the canopy at the Amazon Forest took place during 2007 biomass burning season, from 22 August to 30 October. During this period, aerosol optical properties were monitored using distinct radiometers: a Multi‐Filter Rotating Shadowband Radiometer (MFRSR), the AERONET sunphotometer, a handheld Microtops sunphotometer and Moderate Imaging Spectrometer (MODIS) aboard Terra and Aqua satellites. The Aerosol Optical Depth (AOD) varied strongly during the campaign with the daily average at 670 nm reaching values from 0.5 to 3.0. Angstrom coefficient (α) calculated with AOD at 670 and 870 nm increase from 1.5, before the burning season, to 2.0 as a result of an increase of fine particles into the atmosphere. In early October, the AOD decreased and, as a consequence of the increasing frequency of rain events, AOD went back to the levels observed before burning season. Despite the fact that the distance of AERONET sunphotometer from the experimental site was 80 km, the retrievals obtained from all ground‐based radiometers were consistent and showed good agreement. On the other hand, MODIS retrievals overestimated the AOD during high aerosol concentration when compared with ground‐based radiometers.

A field campaign of the Saharan Mineral Dust Experiment (SAMUM‐2) took place in the Cape Verde islands in January‐February 2008, to investigate the properties of long‐range transported dust over the Atlantic. The Meteorological Institute of the University of Munich deployed a set of active and passive remote sensing instruments: one sun photometer, for the measurement of the direct sun irradiance and sky radiances; a broad‐band UV radiometer; and 2 tropospheric lidar systems. The measurements were made in close cooperation with the other participating groups. During the measurement period the aerosol scenario over Cape Verde mostly consisted of a dust layer below 2 km and a smoke layer above 2 km height. The Saharan dust arrived in the site from the NE, whereas the smoke originated in the African equatorial region is transported from the SE. The aerosol load was also very variable over this area, with AOD (500 nm) ranging from 0.04 to 0.74. The optical properties of the layers are shown: extinction and pa...

To aid the scientific research program on the Toroidal Experiment for Technology Oriented Research (TEXTOR)-94 tokamak, the existing electron cyclotron emission (ECE) diagnostics for the electron temperature studies are being extended with new systems that feature a good temporal and radial resolution. Using the possibility of obtaining the data on a fast time scale, ECE systems allow one to study fast phenomena like the dynamics of small-scale structures such as magnetic islands and transport barriers and microscopic temperature fluctuations throughout the plasma. The quantitative information about nonthermal electron populations can be obtained from the comparison of the second and third harmonic emission. A new 16-channel frequency tunable radiometer and a four-channel second harmonic system were recently installed at TEXTOR-94. The detailed description of the new TEXTOR-94 ECE systems and the recent results will be given and discussed in this article. (C) 2001 American Institute of Physics.

Knowledge of the energy spectrum of fast ions in magnetically confined fusion plasmas is important and fundamental for achieving fusion energy production. Collective Thomson scattering (CTS) of high-power electromagnetic radiation is one of the most promising diagnostic methods for measuring the energy spectrum of confined fast ions. A CTS diagnostic has been implemented on the TEXTOR tokamak for the study of fast ions. It uses a 400 kW, 110 GHz gyrotron source as the probe and a high-resolution heterodyne radiometer as the receiver. Details of the system are given in this article. First results from the diagnostic show that scattered radiation has been detected. (C) 2001 American Institute of Physics.

A simple waveguide arrangement has been developed for the study of microwave absorption and emission from a magnetized afterglow plasma column. The time and frequency resolved measurements are performed by a sampling radiometer. A comparison and null technique permits the direct measurement of the electron temperature. Continuous plots of the temperature vs frequency, magnetic field, and afterglow time are made possible by means of a servoloop. The width of the emission or absorption spectrum in the range of upper hybrid frequencies is used to derive the electron density which, together with the temperature measurement, allows a more complete analysis of the plasma decay.