Reducing systematic biases over the Indian region in CFS V2 by dynamical downscaling

The usefulness of dynamical downscaling of seasonal reforecasts of Indian Monsoon is explored to address the seasonal mean biases in the reforecasts. Almost all the current generation global coupled models, including the Climate Forecast System version 2 (CFSv2, T126 ∼110 km), exhibit systematic mea...

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Main Authors: Hari Prasad, K. B. R. R., Ramu, Dandi A., Rao, Suryachandra A., Hameed, Saji N., Samanta, Dhrubajyoti, Srivastava, Ankur
Other Authors: Asian School of the Environment
Format: Article
Language:English
Published: 2024
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Online Access:https://hdl.handle.net/10356/174097
https://doi.org/10.1029/2020EA001507
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spelling sg-ntu-dr.10356-1740972024-03-19T15:36:56Z Reducing systematic biases over the Indian region in CFS V2 by dynamical downscaling Hari Prasad, K. B. R. R. Ramu, Dandi A. Rao, Suryachandra A. Hameed, Saji N. Samanta, Dhrubajyoti Srivastava, Ankur Asian School of the Environment Earth Observatory of Singapore Earth and Environmental Sciences The usefulness of dynamical downscaling of seasonal reforecasts of Indian Monsoon is explored to address the seasonal mean biases in the reforecasts. Almost all the current generation global coupled models, including the Climate Forecast System version 2 (CFSv2, T126 ∼110 km), exhibit systematic mean dry bias over the central Indian region during the summer monsoon season. Cold sea surface temperature (SST) biases in the Indian Ocean and a weak monsoon circulation due to a colder tropospheric temperature contribute to this dry bias. Such systematic biases restrict the use of skillful forecasts from these models in climate applications (such as agriculture or hydrology). Dynamical downscaling of seasonal forecasts (∼110 km resolution) using the Weather Research and Forecasting (WRF) model coupled to a simple ocean mixed layer model (OML; WRFOML) at 38 km resolution significantly reduces the majority of the systematic biases reported earlier. The seasonal mean dry bias reduces to 16% in WRFOML as compared to 44% (33%) in the CFSv2-T126 (WRFCTL) over the Indian land region. Warmer SSTs in the Indian Ocean and a more robust monsoon circulation emanating from a realistic simulation of the tropospheric temperature reduced the systematic biases in WRFOML compared to CFSv2-T126 and WRFCTL. Additionally, category-wise rainfall distributions are also improved drastically in the downscaled simulations (WRFOML). Downscaled reforecasts with reduced systematic biases have better suitability for climate applications. Published version 2024-03-18T03:02:12Z 2024-03-18T03:02:12Z 2021 Journal Article Hari Prasad, K. B. R. R., Ramu, D. A., Rao, S. A., Hameed, S. N., Samanta, D. & Srivastava, A. (2021). Reducing systematic biases over the Indian region in CFS V2 by dynamical downscaling. Earth and Space Science, 8(6), e2020EA001507-. https://dx.doi.org/10.1029/2020EA001507 2333-5084 https://hdl.handle.net/10356/174097 10.1029/2020EA001507 2-s2.0-85108556708 WOS:000667881300023 https://doi.org/10.1029/2020EA001507 6 8 e2020EA001507 en Earth and Space Science © 2021 The Authors. Earth and Space Science published by Wiley Periodicals LLC on behalf of American Geophysical Union.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. application/pdf
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic Earth and Environmental Sciences
spellingShingle Earth and Environmental Sciences
Hari Prasad, K. B. R. R.
Ramu, Dandi A.
Rao, Suryachandra A.
Hameed, Saji N.
Samanta, Dhrubajyoti
Srivastava, Ankur
Reducing systematic biases over the Indian region in CFS V2 by dynamical downscaling
description The usefulness of dynamical downscaling of seasonal reforecasts of Indian Monsoon is explored to address the seasonal mean biases in the reforecasts. Almost all the current generation global coupled models, including the Climate Forecast System version 2 (CFSv2, T126 ∼110 km), exhibit systematic mean dry bias over the central Indian region during the summer monsoon season. Cold sea surface temperature (SST) biases in the Indian Ocean and a weak monsoon circulation due to a colder tropospheric temperature contribute to this dry bias. Such systematic biases restrict the use of skillful forecasts from these models in climate applications (such as agriculture or hydrology). Dynamical downscaling of seasonal forecasts (∼110 km resolution) using the Weather Research and Forecasting (WRF) model coupled to a simple ocean mixed layer model (OML; WRFOML) at 38 km resolution significantly reduces the majority of the systematic biases reported earlier. The seasonal mean dry bias reduces to 16% in WRFOML as compared to 44% (33%) in the CFSv2-T126 (WRFCTL) over the Indian land region. Warmer SSTs in the Indian Ocean and a more robust monsoon circulation emanating from a realistic simulation of the tropospheric temperature reduced the systematic biases in WRFOML compared to CFSv2-T126 and WRFCTL. Additionally, category-wise rainfall distributions are also improved drastically in the downscaled simulations (WRFOML). Downscaled reforecasts with reduced systematic biases have better suitability for climate applications.
author2 Asian School of the Environment
author_facet Asian School of the Environment
Hari Prasad, K. B. R. R.
Ramu, Dandi A.
Rao, Suryachandra A.
Hameed, Saji N.
Samanta, Dhrubajyoti
Srivastava, Ankur
format Article
author Hari Prasad, K. B. R. R.
Ramu, Dandi A.
Rao, Suryachandra A.
Hameed, Saji N.
Samanta, Dhrubajyoti
Srivastava, Ankur
author_sort Hari Prasad, K. B. R. R.
title Reducing systematic biases over the Indian region in CFS V2 by dynamical downscaling
title_short Reducing systematic biases over the Indian region in CFS V2 by dynamical downscaling
title_full Reducing systematic biases over the Indian region in CFS V2 by dynamical downscaling
title_fullStr Reducing systematic biases over the Indian region in CFS V2 by dynamical downscaling
title_full_unstemmed Reducing systematic biases over the Indian region in CFS V2 by dynamical downscaling
title_sort reducing systematic biases over the indian region in cfs v2 by dynamical downscaling
publishDate 2024
url https://hdl.handle.net/10356/174097
https://doi.org/10.1029/2020EA001507
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