Cloud Radiative Effect on the Earth's Surface

• 資料種別: 文書・図像類
• タイトル: Cloud Radiative Effect on the Earth's Surface
• 著者・編者: YAMADA, Kyohei; HAYASAKA, Tadahiro; IWABUCHI, Hironobu
• 著者標目: YAMADA, Kyohei; HAYASAKA, Tadahiro; IWABUCHI, Hironobu
• 出版事項: Chiba University. Center for Environmental Remote Sensing
• 出版年月日等: 2013-07-04
• 出版年（W3CDTF）: 2013-07-04
• タイトル（掲載誌）: Proceedings of the CEReS international symposium = CEReS国際シンポジウム資料集
• 巻号年月日等（掲載誌）: 19
• 掲載巻: 19
• 掲載ページ: 51-52
• 本文の言語コード: eng
• 対象利用者: 一般
• 一般注記: type:text; [ABSTRACT]Cloud has strong influence on radiation budget at the surface. For shortwave radiation, cloud reflects downward shortwave radiation (DSR) and shows cooling effect on surface atmosphere. On the other hand, cloud absorbs upward longwave radiation and emits downward longwave radiation (DLR). The absorption and emission make surface atmosphere warm up. The cooling and warming effects offset each other. Warming effect is strong in the low latitude because of frequent appearance of high cloud. Conversely, low cloud causes cooling effect stronger than warming effect, especially in the high latitude (Slingo and Slingo, 1988). On the global average, the cooling effect is greater than the warming effect. However, our understanding of the cloud effect on surface radiation budget is limited because cloud microphysics, cloud amount, and cloud position are sensitive to the local climate condition. In the present study, we quantify cloud radiative effect (CRE) both on DSR and DLR. CRE is defined with the subtraction of the calculated value assumed clear-sky from the observed value under all-sky condition. To calculate radiation at the surface, we use mstrnX (Sekiguchi and Nakajima, 2008), which is two-stream one-dimensional radiative transfer calculation model considering vertical profiles of temperature and humidity obtained with radiosonde observation. Observation sites are eight stations of Baseline Surface Radiation Network (BSRN; Ohmura et al. 1998) from the subtropics to polar regions. Observation period is from 1994 to 2012 and each station has at least 1 year data. Calculated value is compensated with the subtraction of the average under clear-sky condition. Cloud cover (CC) is one of the factors which affect on CRE both on shortwave and longwave. For longwave radiation, the average of CRE increased with the increment of CC, but the CRE varies largely with climate condition. The effect of CC on DSR is more complex than DLR because the cloud position is important for reflection of sunlight. Therefore, in order to estimate CRE on shortwave radiation, we evaluated the cloud position using sunshine duration. CRE on DSR normally takes negative value because cloud reflects incoming solar radiation. However, CRE on DSR sometimes took positive value because of three-dimensional effects. If cloud does not obstruct direct shortwave radiation, sunlight reflected at the cloud side and global solar radiation becomes strong. The three-dimensional effects were getting more intense and occurred more frequently with increase of CC, but positive value was almost never under complete cloudy condition without instrumental error. For DLR, cloud base height (CBH) and cloud base temperature (CBT) are important factors because thick cloud can be assumed to be block body and emits longwave radiation from cloud base. However, the variation in CBT was small when CC is less than half of 8 oktas. Height of cloud is not directly important, but albedo of water cloud is generally larger than ground albedo without ice surface. Atmosphere is transparent but opaque for longwave radiation. Water vapor is one of the important absorbers. CRE on longwave increased with increase of precipitable water amount (PW) under dry condition, such that PW is less than 10 mm. In areas where PW is 10-40 mm, CRE weakened with increasing PW. Under wet condition, which PW is larger 40 mm, CRE was almost invariable. In comparison with CRE of A-train product by Stephens et al. (2012), the present study showed large negative value under very dry condition and very small value at the region with small PW around 10 mm. The former discrepancy was caused by strong temperature inversion near the surface at polar regions, and the latter was caused by small amount of CC which satellite missed. These discrepancies showed the importance of the local and small climate condition which is too small for satellite resolution for CRE.
• オンライン閲覧公開範囲: 限定公開
• 連携機関・データベース: 国立情報学研究所 : 学術機関リポジトリデータベース（IRDB）（機関リポジトリ）; https://irdb.nii.ac.jp
• 提供元機関・データベース: 千葉大学 : 千葉大学学術成果リポジトリ