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Assessment on the impact of corrected GODAS initial conditions in the CFS hindcasts

Assessment on the impact of corrected GODAS initial conditions in the CFS hindcasts for 1981 - 1990 Contributors: Wanqiu Wang, Yan Xue, Jae Schemm, Hui Wang .

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Assessment on the impact of corrected GODAS initial conditions in the CFS hindcasts

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  1. Assessment on the impact of corrected GODAS initial conditions in the CFS hindcasts for 1981 - 1990 Contributors: Wanqiu Wang, Yan Xue, Jae Schemm, Hui Wang

  2. To investigate the impact of GODAS corrections made for 1981-1990 on the CFS hindcast skill, 15 ensemble member runs are made for each January and July month in 1981-1990 with five atmospheric I.C. paired with each oceanic I.C. centered on Dec. 11, 21, Jan. 1 and June 11, 21, July 1. • Impact of GODAS corrections on model’s climatologies and hindcast skill in 1981-2004 is assessed for sea surface temperature, precipitation and 2m temperature. • Mean SST is reduced by 0.2-0.4 degree due to GODAS corrections, which reduces warm biases but worsens cold biases, particularly for June IC’s. Changes in precipitation bias are confined in the Tropics. • SST hindcast skill is significantly increased, most prominent in the Pacific and Indian Ocean for December IC’s and in the Atlantic Ocean for June IC’s. • Slight increase in skill over the North American Sector for 2m temperature and spring precipitation with corrected GODAS.

  3. Average SST at Equatorfor 1981-1990 Dec Start June Start newGodas - Standard Standard - Obs newGodas - Standard Standard - Obs JFM AMJ JAS

  4. Average TAUX at Equatorfor 1981-1990 Dec Start June Start newGodas - Standard Standard - Obs newGodas - Standard Standard - Obs JFM AMJ JAS

  5. SST indices from the web site of Ocean Observations Panel for Climate (OOPC)

  6. SST Indices Hindcast Skill in 1981-2005 (red  improvement) JAS OND JFM

  7. SST hindcast averaged in the hurricane main development region (MDR) for July-November starting from June 11-31 I.C.. The SST hindcast is reduced (green) in 1981-1990 and increased (red) in 1991-2005 due to GODAS corrections. CFS realistically simulated the peaks of the index in 1987, 1995, 1998 and 2003-2005, and valleys in 1984-1986 and 1994, which suggests a potential contribution of the CFS forecast for the hurricane outlook.

  8. North America

  9. Summary • Continue to investigate the impact of GODAS corrections on atmospheric circulation and subsurface ocean temperature with December and June runs. • The two test cases clearly demonstrate that the GODAS corrections have significant positive impact on tropical SST prediction, and also positive impact on U.S. precipitation and 2m temperature. • CST’s approval is requested at this time for the extension of hindcast reruns for April and October ICs. These cases will be used to evaluate impact on the hurricane and winter season predictions.

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