A study of the shortwave direct aerosol forcing using ESSP/CALIPSO observation and GCM simulation

Eiji Oikawa, Teruyuki Nakajima, Toshiro Inoue, David Winker

研究成果: Contribution to journalArticle査読

22 被引用数 (Scopus)

抄録

Shortwave direct aerosol radiative forcing (DARF) is derived at the top of the atmosphere (TOA) and at the surface under clear-sky, cloudy-sky, and all-sky conditions using data of space-borne CALIOP lidar and MODIS sensor. We investigate four scenarios for evaluating the DARF: clear-sky, the case that aerosols exist above clouds, the case that aerosols exist below high-level clouds, and the case that aerosols are not detected by CALIOP in cloudy-sky condition. The cloudy-sky DARF is estimated by the latter three scenarios. The all-sky DARF is the combination of clear-sky and cloudy-sky DARF weighted by the cloud occurrence. They are then compared with DARF calculated by a global aerosol model, SPRINTARS. The results show that the TOA forcing over desert regions caused by dust with single scattering albedo (SSA) of 0.92 is positive regardless of cloud existence, due to high solar surface albedo. Off southern Africa, smoke aerosols with SSA of 0.84 above low-level clouds are observed and simulated and the annual mean TOA cloudy-sky DARF is estimated at more than +3 Wm2, consistent with past studies. Aerosols with SSA of 0.96 within optically thin clouds cause a TOA negative forcing, while that within optically thick clouds cause a TOA positive forcing. This indicates that aerosols within optically thick clouds cause positive forcing in our radiative transfer calculation, regardless of SSA. Annual zonal averages of DARF from 60S to 60N under clear-sky, cloudy-sky, and all-sky are 2.97, +0.07, and 0.61 Wm2 from CALIOP and 2.78, +1.07, and 0.58 Wm2 from SPRINTARS.

本文言語英語
ページ(範囲)3687-3708
ページ数22
ジャーナルJournal of Geophysical Research: Atmospheres
118
9
DOI
出版ステータス出版済み - 8 16 2013
外部発表はい

All Science Journal Classification (ASJC) codes

  • 大気科学
  • 地球物理学
  • 地球惑星科学(その他)
  • 宇宙惑星科学

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