Validation of estimated cloud fraction from MERRA-2 and AIRS data using ground based observation over IAO, Hanle

Ningombam, Shantikumar S.; Narendra, Aditya; Bhatt, B. C.; Prabhu, T. P.; Anupama, G. C.; Angchuk, Dorje; Jorphail, Sonam

doi:10.1016/j.asr.2020.05.001

Cited by 4 publications

(3 citation statements)

References 32 publications

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“…These effects result in a limited range (around 30%–90%) of the average CC values from AIRS over Chiba. Such limited CC range from nighttime AIRS data was also reported in a previous study (Ningombam et al., 2020). Nevertheless, Figure 10b indicates that the difference between the two observation methods is approximately normally distributed.…”

Section: Resultssupporting

confidence: 85%

“…Traditionally, ground-based and manual observation of CC relies on the evaluation of octa, which corresponds to the situation that clouds cover 12.5% (i.e., 1/8) of the whole hemisphere. This visual method can lead to only a few observations per day, though the results exhibit a good correlation with satellite and reanalysis data (Ningombam et al, 2020). In the present work, we use cameras to gather CC data every 5 min to obtain a deeper understanding of cloud occurrence, dynamics, and clouds' role in atmospheric radiative transfer.…”

Section: Detection Of Nighttime Clouds and CC Algorithmmentioning

confidence: 99%

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Observations of Nighttime Clouds Over Chiba, Japan, Using Digital Cameras and Satellite Images

2021

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Nighttime cloud cover (CC) is analyzed from the data observed for 34 months over Chiba, Japan, using continuously operated digital cameras. The normal camera works in the visible region, providing quantitative and temporal changes of nighttime CC. The second camera captures sky images without the near‐infrared cut filter, and by applying the thresholding method, we obtain information on the temporal changes of thin (pixel values between 72 and 115) and thick (>115) clouds. Comparing the CC from the visible camera with cloud fraction from Atmospheric Infrared Sounder (AIRS) shows that long‐term data from the camera are valuable for correcting the underestimation of the cloud fraction product from AIRS for low‐level clouds. Furthermore, a comparison between the near‐ground temperature and CC results in estimating the seasonal changes of feedback effects of upward thermal radiation from the ground. The current results reveal that thick clouds contribute to longwave cloud forcing (LWCF) below 100 Wm−2, while thin clouds with CC below 30% contribute to LWCF below 10.2 Wm−2.

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Section: Resultssupporting

confidence: 85%

Section: Detection Of Nighttime Clouds and CC Algorithmmentioning

confidence: 99%

Observations of Nighttime Clouds Over Chiba, Japan, Using Digital Cameras and Satellite Images

2021

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“…The estimation of the nighttime cloud fraction is one of the key parameters for evaluating the number of useful nights at an astronomical site [42][43][44]. In order to estimate the number of useful nights at the BTA, we used a similar approach to that described in paper [42].…”

Section: Nighttime Cloud Fraction Fractionmentioning

confidence: 99%

Precipitable Water Vapor and Fractional Clear Sky Statistics within the Big Telescope Alt-Azimuthal Region

et al. 2022

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The development of a network of ground-based telescopes requires detailed astroclimatic studies. This paper presents the spatial distributions of precipitable water vapor (PWV), total cloud cover (TCC) and cloud base height (CBH). With the aim of a representative description of the precipitable water vapor, a method for correcting this characteristic which takes into account the underlying surface is proposed. The method uses the exponential decrease in the water vapor content with the altitude and is based on the calculation of the averaged elevation of the grid nodes around the site. By applying this correction method, the seasonal changes in the median PWV values at the sites of Ali, Muztag-Ata and Suffa, as well as within the Chajnantor area are estimated. We show that the decrease of PWV with the altitude is exponential with a height scale of 1000 m for the sites in South America and Eurasia. The astroclimatic characteristics within the Big Telescope Alt-azimuthal (BTA) region (40∘N–50∘N; 35∘E–55∘E) are estimated. In this region, the sites suitable for the millimeter and submillimeter (mm/submm) observations are revealed. New sites are Mt. Horai and Mt. Kurapdag. In addition, we show that the Era-5 reanalysis data overestimate the PWV values by 1–2 mm and describe changes in the monthly medians of PWV. Comparison of the calculated medians with the measured PWV show that the correlation coefficient between these characteristics is 0.97.

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Impact of aerosols on warm clouds over the Sichuan Basin, China in winter based on the MERRA-2 reanalysis dataset

Zhu

Xiao

Che

et al. 2022

Atmospheric Pollution Research

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Validation of estimated cloud fraction from MERRA-2 and AIRS data using ground based observation over IAO, Hanle

Cited by 4 publications

References 32 publications

Observations of Nighttime Clouds Over Chiba, Japan, Using Digital Cameras and Satellite Images

Observations of Nighttime Clouds Over Chiba, Japan, Using Digital Cameras and Satellite Images

Precipitable Water Vapor and Fractional Clear Sky Statistics within the Big Telescope Alt-Azimuthal Region

Impact of aerosols on warm clouds over the Sichuan Basin, China in winter based on the MERRA-2 reanalysis dataset

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