皆様
１１月８日に、地球フロンティア（横浜）で、韓国ソウル大学の
B.J.Sohn教授のセミナーを開きますのでお知らせ致します。
Sohn教授は１１月６・７日は、GAME International Science Panelの
会議に出席されます。
------------IGCR FORMAL SEMINAR ---------------------
Speaker: Dr. Byung-Ju Sohn
Professor, School of Earth and Environmental
Sciences, Seoul National University
Date & Time: November 8(Fri) 16:00 - 17:30 pm
Place: Small Conference Room 1, 2 of IGCR, YES
Title: "A New Look at Cloud Radiative Forcing: Coupling
with Water Vapor Forcing"
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Abstract:
It has been noted that the ERBE cloud radiative forcing (CRF) has a
significant bias of up to about 20 Wm-2 over the tropical moist region,
compared model analysis results (e.g., Collins and Inamdar, 1995; Slingo et
al., 1998). However, it has never been clarified why there are such large
differences and where those systematic differences are from. Here we
provide evidences that those discrepancies are caused by different
definitions of cloud forcing (or clear-sky fluxes) employed by two
different approaches. Model analysis employs CRF defined as the radiation
changes by clouds during the transition from cloud-free state to cloudy
state of the earth-atmosphere system, while other surface atmospheric
variables are held fixed during the transition. In contrast, ERBE CRF
implicitly includes additional radiative effects due to the variations of
surface and atmospheric variables that are correlated with clouds.
A positive relationship between SSM/T-2 derived upper tropospheric
water-vapor (UTW) and collocated CERES CRF strongly supports the notion that
the aforementioned biases are largely due to different distributions of
upper tropospheric water vapor employed in the model analysis and ERBE
clear-sky climatologies. We computed a possible range of the CRF bias using
a relationship between ISCCP high cloud and SSM/T-2 derived UTW. Up to 20
Wm-2 of CRF bias appears to be contributed by UTW change alone over
convectively active regions, indicating that at most one quarter of ERBE CRF
is the water vapor forcing associated with high cloud development.
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Miyoko Oki
Research Promotion Staff
Frontier Research System for Global Change (FRSGC)
3173-25 Showa-machi, Kanazawa-ku, Yokohama,
Kanagawa 236-0001, Japan
TEL: +81-45-778-5686
FAX: +81-45-778-5497
E-mail: ookim@jamstec.go.jp
URL: http://jamstec.go.jp/frsgc/
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