Through thick and thin: quantitative classification of photometric observing conditions on Paranal

Kerber, F.; Querel, Richard; Neureiter, Bianca; Hanuschik, R. W.

doi:10.1117/12.2232333

Cited by 7 publications

(10 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This is especially true for the high altitude and thin clouds with the warm and humid atmosphere [13,29]. Overall, during the warm and humid summer, the spectral test for the cold clouds, but over −50 • C, becomes less effective than the temporal test [3,8]. Thus, the POD difference among the four experimental datasets is mainly determined by the temporal test, which shows a better performance with the lower NEdT.…”

Section: Reference Datamentioning

confidence: 97%

“…Compared with other instruments for cloud detection-active and passive sensors alike-the IRT used for the current study is relatively simple and easy to operate [3,4]. The measured radiances of approximately 10 µm correspond to the atmospheric window region and are quite sensitive to cloud presence, resulting in the measured radiance in cloudy conditions showing a warmer (spectral) and more variable (temporal) characteristic compared with clear-sky radiation.…”

Section: Introductionmentioning

confidence: 99%

“…Since Tb CLR and its temporal variability changes with the atmospheric conditions, the most important part of the detection algorithm is to have an accurate Tb CLR and its temporal variability. Here, it should be emphasized that Tb CLR has a rather large variation, even at the atmospheric window region, which is mainly depending on the variability of water vapor and the temperature of the lower atmosphere [3,[12][13][14]. It has been shown that a sufficiently accurate Tb CLR is obtained with an empirical formula as a function of the real-time surface temperature (T SFC ) and humidity (e) (a detailed description for the derivation of the empirical formula is given elsewhere [9], while a summary is also given in Appendix A).…”

Section: Data and Pre-processingmentioning

confidence: 99%

“…Furthermore, Brocard et al [6] tried to utilize a temporal fluctuation of brightness temperature (hereafter Tb) obtained from the infrared radiometer to detect cirrus cloud, which regulates outgoing longwave radiation. From these studies, it has been shown that the detection algorithm using the spectral and temporal characteristics of the cloud radiation provides quite satisfactory and reliable cloud detection [3,[6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Effects of Dynamic Range and Sampling Rate of an Infrared Thermometer to the Accuracy of the Cloud Detection

Won

Ahn

2018

Remote Sensing

View full text Add to dashboard Cite

Cloud detection using downwelling radiation measured by infrared thermometer (IRT) has been utilized for many applications. The current study investigates the effects of disparate IRT specifications, including the dynamic range and sampling rates on the performance of cloud detection, which utilizes the spectral and temporal characteristics of cloudy radiation. To analyze the effects, the detection algorithm that was prepared with and applied to the IRT data with different specifications is compared with reference data, a ceilometer, and micro-pulse lidar (MPL). The comparison results show that the low-altitude clouds are detected with a sufficient accuracy: better than 97% probability of detection (POD). This is due to the much warmer brightness temperature (Tb) of the low clouds compared with the clear sky in the atmospheric window region where the IRT measurement was made. Conversely, the high-altitude cold clouds are hard to detect with the spectral test due to the much-reduced Tb contrast between cloudy and clear sky. Thus, the algorithm performance is largely dependent on the performance of the temporal test. Since the lower measurement noise provides a better estimation of the temporal variability of clear sky Tb with less estimation uncertainty, the IRT data having a better noise performance shows a better POD value by as much as 52.2% compared with the MPL result. However, the improvement is realized only when the dynamic range of IRT covers sufficiently cold Tb, such as −100 • C.

show abstract

Section: Reference Datamentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Section: Data and Pre-processingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Effects of Dynamic Range and Sampling Rate of an Infrared Thermometer to the Accuracy of the Cloud Detection

Won

Ahn

2018

Remote Sensing

View full text Add to dashboard Cite

show abstract

“…variations in the detected star magnitude of order 0.1 to 0.2 magnitudes. 4 Importantly, in the context of new large aperture telescopes as the European Extremely-Large Telescope (ELT), 5 TMT 6 and the Giant Magellan Telescope (GMT), 7 which will use sodium LGS extensively, cirrus clouds will have a significant impact on performance. In telescopes employing adaptive optic (AO) systems using multiple center-launched lasers, such as the Gemini South (GeMS) 8 and the TMT (NFIRAOS), 9 the backscattered laser light due to Rayleigh scattering from air molecules, and Mie scattering in cirrus clouds and from aerosol particles, is detected by the wavefront sensors matched to neighboring LGS.…”

Section: Background Informationmentioning

confidence: 99%

Study of cirrus clouds and implications for the variability of laser guide star intensity and fratricide effects

Otárola¹

2017

Proceedings of the Adaptive Optics for Extremely Large Telescopes 5

View full text Add to dashboard Cite

Measurements of back-scattering, at a wavelength of 532 nm, from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite, over the period June 2006-November 2016, are analyzed to characterize cirrus clouds at the location of several observatory sites worldwide. From these data, we derive statistics of altitude, thickness and optical depth of cirrus clouds. These parameters are relevant for understanding and modeling the effects of cloud and aerosols on laser propagation for adaptive optics and the temporal variability of the fratricide pattern. The latter is particularly important for facilities employing center-launched lasers, such as the Thirty Meter Telescope.

show abstract

Climatologies of Various OH Lines From About 90,000 X‐Shooter Spectra

et al. 2023

View full text Add to dashboard Cite

The nocturnal mesopause region of the Earth's atmosphere radiates chemiluminescent emission from various roto‐vibrational bands of hydroxyl (OH), which is therefore a good tracer of the chemistry and dynamics at the emission altitudes. Intensity variations can, for example, be caused by the general circulation, gravity waves, tides, planetary waves, and the solar activity. While the basic OH response to the different dynamical influences has been studied quite frequently, detailed comparisons of the various individual lines are still rare. Such studies can improve our understanding of the OH‐related variations as each line shows a different emission profile. We have therefore used about 90,000 spectra of the X‐shooter spectrograph of the Very Large Telescope at Cerro Paranal in Chile in order to study 10 years of variations of 298 OH lines. The analysis focuses on climatologies of intensity, solar cycle effect (SCE), and residual variability (especially with respect to time scales of hours and about 2 days) for day of year and local time. For a better understanding of the resulting variability patterns and the line‐specific differences, we applied decomposition techniques, studied the variability depending on time scale, and calculated correlations. As a result, the mixing of thermalized and nonthermalized OH level populations clearly influences the amplitude of the variations. Moreover, the local times of the variability features shift depending on the effective line emission height, which can mainly be explained by the propagation of the migrating diurnal tide. This behavior also contributes to remarkable differences in the effective SCE.

show abstract

Through thick and thin: quantitative classification of photometric observing conditions on Paranal

Cited by 7 publications

References 11 publications

Effects of Dynamic Range and Sampling Rate of an Infrared Thermometer to the Accuracy of the Cloud Detection

Effects of Dynamic Range and Sampling Rate of an Infrared Thermometer to the Accuracy of the Cloud Detection

Study of cirrus clouds and implications for the variability of laser guide star intensity and fratricide effects

Climatologies of Various OH Lines From About 90,000 X‐Shooter Spectra

Contact Info

Product

Resources

About