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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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-05-01
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| Series: | The Cryosphere |
| Online Access: | https://tc.copernicus.org/articles/17/1913/2023/tc-17-1913-2023.pdf |
| Summary: | <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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| ISSN: | 1994-0416 1994-0424 |