Cloud Fractions Estimated from Shipboard Whole-Sky Camera and Ceilometer Observations

Abstract

Shipboard observations of cloud fraction were performed along the round-trip research cruise between Japan and Antarctica from November 2013 to April 2014 using both a whole-sky camera and a ceilometer onboard the Research Vessel (R/V) Shirase. Based on the results of the comparison of these cloud fractions, it was found that the correlation coefficient was 0.86 for the 2024 observations acquired between Australia and Antarctica from 27 November to 9 December 2013. Overall, the results were consistent between the two observation methods; however, some underestimation by the whole-sky camera was determined in comparison with the ceilometer. It is intended that shipboard observations will continue onboard the R/V Shirase over subsequent every years in order to improve the retrieval of cloud fractions for the validation of satellite observations.

Cloud Fractions Estimated from Shipboard Whole-Sky Camera and Ceilometer Observations between East Asia and Antarctica

“…The fundamental specifications of the observations and data for JARE 55 were described in Kuji et al (2016). Shipboard observations and the analyzed data from JARE 55 and 56 are described further in this section.…”

“…Table 1 summarizes the R/V Shirase cruises of JARE 55 and 56. Shipboard observations were performed using a whole-sky camera and a ceilometer onboard the R/V Shirase (Kuji et al 2016); visual observation data were available only during JARE 56. The entire journey takes several months from November to March or April of the following year.…”

“…We note that the number of observation events for the sea ice region amounted to approximately half of the entire observations made on both JARE 55 and 56. Kuji et al (2016) estimated the cloud fraction for the open ocean region between Australia and Antarctica using a whole-sky camera during JARE 55 (November to December 2013). They found that the cloud fraction estimates between the whole-sky camera and the ceilometer were consistent with a correlation coefficient of 0.86.…”

“…We show observations and initial results from the dataset in terms of cloud fraction using a whole-sky camera. A previous study found that a constant classification parameter was sufficient for an open water region (Kuji et al 2016). However, this parameter was determined as a function of sun elevation over a sea ice region, because higher surface albedo was usually observed owing to the presence of sea ice in higher latitudes near Antarctica.…”

“…They demonstrated that a ground-based sky camera was complementary to satellite observations. Kuji et al (2016) described an overview of an observation system with a whole-sky camera and ceilometer onboard the R/V Shirase. They showed the initial results of spatiotemporal variations in cloud fractions between Australia and Antarctica during the Japan Antarctic Regional Expedition 55 (JARE 55).…”