Changes in March mean snow water equivalent since the mid-20th century and the contributing factors in reanalyses and CMIP6 climate models

<p>Trends in March mean snow water equivalent (SWE) in the Northern Hemisphere are attributed to changes in three main factors: total precipitation (<span class="inline-formula"><i>P</i></span>), fraction of precipitation as snowfall (<span class="inli...

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Main Author: J. Räisänen
Format: Article
Language:English
Published: Copernicus Publications 2023-05-01
Series:The Cryosphere
Online Access:https://tc.copernicus.org/articles/17/1913/2023/tc-17-1913-2023.pdf
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author J. Räisänen
author_facet J. Räisänen
author_sort J. Räisänen
collection DOAJ
description <p>Trends in March mean snow water equivalent (SWE) in the Northern Hemisphere are attributed to changes in three main factors: total precipitation (<span class="inline-formula"><i>P</i></span>), fraction of precipitation as snowfall (<span class="inline-formula"><i>F</i></span>), and fraction of accumulated snowfall remaining on the ground (<span class="inline-formula"><i>G</i></span>). This trend attribution is repeated for two reanalyses (ERA5-Land from March 1951 to 2022 and MERRA2 – Modern-Era Retrospective analysis for Research and Applications, Version 2 – from 1981 to 2022) and simulations by 22 climate models from the 6th phase of the Coupled Model Intercomparison Project (CMIP6). The results reveal a decrease in SWE in most of the Northern Hemisphere, as decreases in <span class="inline-formula"><i>F</i></span> and <span class="inline-formula"><i>G</i></span> dominate over mostly positive trends in <span class="inline-formula"><i>P</i></span>. However, there is spatial variability in both the magnitude and sign of these trends. There is substantial variation between the individual CMIP6 models, but the agreement between the CMIP6 multi-model mean and ERA5-Land is reasonable for both the area means and the geographical distribution of the trends from 1951 to 2022, with a spatial correlation of 0.51 for the total SWE trend. The agreement for the trends from 1981 to 2022 is worse, probably partly due to internal climate variability but also due to the overestimation of the recent warming in the CMIP6 models. Over this shorter period for which ERA5-Land can be compared with MERRA2, there are also marked trend differences between these two reanalyses. However, the SWE decreases associated with reduced snowfall fraction (<span class="inline-formula"><i>F</i></span>) are more consistent between the different data sets than the trends resulting from changes in <span class="inline-formula"><i>P</i></span> and <span class="inline-formula"><i>G</i></span>.</p>
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spelling doaj.art-f3b2b7e82d4c4bb49c69f8adc97cf6862023-05-09T10:15:11ZengCopernicus PublicationsThe Cryosphere1994-04161994-04242023-05-01171913193410.5194/tc-17-1913-2023Changes in March mean snow water equivalent since the mid-20th century and the contributing factors in reanalyses and CMIP6 climate modelsJ. Räisänen<p>Trends in March mean snow water equivalent (SWE) in the Northern Hemisphere are attributed to changes in three main factors: total precipitation (<span class="inline-formula"><i>P</i></span>), fraction of precipitation as snowfall (<span class="inline-formula"><i>F</i></span>), and fraction of accumulated snowfall remaining on the ground (<span class="inline-formula"><i>G</i></span>). This trend attribution is repeated for two reanalyses (ERA5-Land from March 1951 to 2022 and MERRA2 – Modern-Era Retrospective analysis for Research and Applications, Version 2 – from 1981 to 2022) and simulations by 22 climate models from the 6th phase of the Coupled Model Intercomparison Project (CMIP6). The results reveal a decrease in SWE in most of the Northern Hemisphere, as decreases in <span class="inline-formula"><i>F</i></span> and <span class="inline-formula"><i>G</i></span> dominate over mostly positive trends in <span class="inline-formula"><i>P</i></span>. However, there is spatial variability in both the magnitude and sign of these trends. There is substantial variation between the individual CMIP6 models, but the agreement between the CMIP6 multi-model mean and ERA5-Land is reasonable for both the area means and the geographical distribution of the trends from 1951 to 2022, with a spatial correlation of 0.51 for the total SWE trend. The agreement for the trends from 1981 to 2022 is worse, probably partly due to internal climate variability but also due to the overestimation of the recent warming in the CMIP6 models. Over this shorter period for which ERA5-Land can be compared with MERRA2, there are also marked trend differences between these two reanalyses. However, the SWE decreases associated with reduced snowfall fraction (<span class="inline-formula"><i>F</i></span>) are more consistent between the different data sets than the trends resulting from changes in <span class="inline-formula"><i>P</i></span> and <span class="inline-formula"><i>G</i></span>.</p>https://tc.copernicus.org/articles/17/1913/2023/tc-17-1913-2023.pdf
spellingShingle J. Räisänen
Changes in March mean snow water equivalent since the mid-20th century and the contributing factors in reanalyses and CMIP6 climate models
The Cryosphere
title Changes in March mean snow water equivalent since the mid-20th century and the contributing factors in reanalyses and CMIP6 climate models
title_full Changes in March mean snow water equivalent since the mid-20th century and the contributing factors in reanalyses and CMIP6 climate models
title_fullStr Changes in March mean snow water equivalent since the mid-20th century and the contributing factors in reanalyses and CMIP6 climate models
title_full_unstemmed Changes in March mean snow water equivalent since the mid-20th century and the contributing factors in reanalyses and CMIP6 climate models
title_short Changes in March mean snow water equivalent since the mid-20th century and the contributing factors in reanalyses and CMIP6 climate models
title_sort changes in march mean snow water equivalent since the mid 20th century and the contributing factors in reanalyses and cmip6 climate models
url https://tc.copernicus.org/articles/17/1913/2023/tc-17-1913-2023.pdf
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