Improvements in Wintertime Surface Temperature Variability in the Community Earth System Model Version 2 (CESM2) Related to the Representation of Snow Density
Abstract The Community Earth System Model (CESM) is widely used for the prediction and understanding of climate variability and change. Accurate simulation of the behavior of near surface air temperature (T2m) is critical in such a model for addressing societally relevant problems. However, previous...
| Main Authors: | , , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
American Geophysical Union (AGU)
2022-04-01
|
| Series: | Journal of Advances in Modeling Earth Systems |
| Subjects: | |
| Online Access: | https://doi.org/10.1029/2021MS002880 |
| _version_ | 1818268978130190336 |
|---|---|
| author | Isla R. Simpson David M. Lawrence Sean C. Swenson Cecile Hannay Karen A. McKinnon John E. Truesdale |
| author_facet | Isla R. Simpson David M. Lawrence Sean C. Swenson Cecile Hannay Karen A. McKinnon John E. Truesdale |
| author_sort | Isla R. Simpson |
| collection | DOAJ |
| description | Abstract The Community Earth System Model (CESM) is widely used for the prediction and understanding of climate variability and change. Accurate simulation of the behavior of near surface air temperature (T2m) is critical in such a model for addressing societally relevant problems. However, previous versions of CESM suffered from an overestimation of wintertime T2m variability in Northern Hemisphere (NH) land regions. Here, it is shown that the latest version of CESM (CESM2) exhibits a much improved representation of wintertime T2m variability compared to its predecessor and it now compares well with observations. A series of targeted experiments reveal that an important contributor to this improvement is the local effects of changes to the representation of snow density within the land surface component. Increased snow densities in CESM2 lead to enhanced conductance of the snow layer. As a result, larger heat fluxes across the snow layer are induced in the presence of T2m anomalies, leading to a greater dampening of surface and near surface atmospheric temperature anomalies. The implications for future projections with CESM2 are also considered through comparison of the CESM1 and CESM2 large ensembles. Aligned with the reduction in surface temperature variability, compared to CESM1, CESM2 exhibits reduced ensemble spread in future projections of NH winter mean temperature and a smaller decline in daily wintertime T2m variability under climate change. Overall, this improvement has increased the accuracy of CESM2 as a tool for the study of wintertime T2m variability and change. |
| first_indexed | 2024-12-12T20:47:04Z |
| format | Article |
| id | doaj.art-abbfb1f3867d426f828cb63739b58e3c |
| institution | Directory Open Access Journal |
| issn | 1942-2466 |
| language | English |
| last_indexed | 2024-12-12T20:47:04Z |
| publishDate | 2022-04-01 |
| publisher | American Geophysical Union (AGU) |
| record_format | Article |
| series | Journal of Advances in Modeling Earth Systems |
| spelling | doaj.art-abbfb1f3867d426f828cb63739b58e3c2022-12-22T00:12:33ZengAmerican Geophysical Union (AGU)Journal of Advances in Modeling Earth Systems1942-24662022-04-01144n/an/a10.1029/2021MS002880Improvements in Wintertime Surface Temperature Variability in the Community Earth System Model Version 2 (CESM2) Related to the Representation of Snow DensityIsla R. Simpson0David M. Lawrence1Sean C. Swenson2Cecile Hannay3Karen A. McKinnon4John E. Truesdale5Climate and Global Dynamics Laboratory National Center for Atmospheric Research Boulder CO USAClimate and Global Dynamics Laboratory National Center for Atmospheric Research Boulder CO USAClimate and Global Dynamics Laboratory National Center for Atmospheric Research Boulder CO USAClimate and Global Dynamics Laboratory National Center for Atmospheric Research Boulder CO USADepartment of Statistics and Institute of the Environment and Sustainability University of California Los Angeles CA USAClimate and Global Dynamics Laboratory National Center for Atmospheric Research Boulder CO USAAbstract The Community Earth System Model (CESM) is widely used for the prediction and understanding of climate variability and change. Accurate simulation of the behavior of near surface air temperature (T2m) is critical in such a model for addressing societally relevant problems. However, previous versions of CESM suffered from an overestimation of wintertime T2m variability in Northern Hemisphere (NH) land regions. Here, it is shown that the latest version of CESM (CESM2) exhibits a much improved representation of wintertime T2m variability compared to its predecessor and it now compares well with observations. A series of targeted experiments reveal that an important contributor to this improvement is the local effects of changes to the representation of snow density within the land surface component. Increased snow densities in CESM2 lead to enhanced conductance of the snow layer. As a result, larger heat fluxes across the snow layer are induced in the presence of T2m anomalies, leading to a greater dampening of surface and near surface atmospheric temperature anomalies. The implications for future projections with CESM2 are also considered through comparison of the CESM1 and CESM2 large ensembles. Aligned with the reduction in surface temperature variability, compared to CESM1, CESM2 exhibits reduced ensemble spread in future projections of NH winter mean temperature and a smaller decline in daily wintertime T2m variability under climate change. Overall, this improvement has increased the accuracy of CESM2 as a tool for the study of wintertime T2m variability and change.https://doi.org/10.1029/2021MS002880temperature variabilityclimate modelingland‐atmosphere couplingsnow density |
| spellingShingle | Isla R. Simpson David M. Lawrence Sean C. Swenson Cecile Hannay Karen A. McKinnon John E. Truesdale Improvements in Wintertime Surface Temperature Variability in the Community Earth System Model Version 2 (CESM2) Related to the Representation of Snow Density Journal of Advances in Modeling Earth Systems temperature variability climate modeling land‐atmosphere coupling snow density |
| title | Improvements in Wintertime Surface Temperature Variability in the Community Earth System Model Version 2 (CESM2) Related to the Representation of Snow Density |
| title_full | Improvements in Wintertime Surface Temperature Variability in the Community Earth System Model Version 2 (CESM2) Related to the Representation of Snow Density |
| title_fullStr | Improvements in Wintertime Surface Temperature Variability in the Community Earth System Model Version 2 (CESM2) Related to the Representation of Snow Density |
| title_full_unstemmed | Improvements in Wintertime Surface Temperature Variability in the Community Earth System Model Version 2 (CESM2) Related to the Representation of Snow Density |
| title_short | Improvements in Wintertime Surface Temperature Variability in the Community Earth System Model Version 2 (CESM2) Related to the Representation of Snow Density |
| title_sort | improvements in wintertime surface temperature variability in the community earth system model version 2 cesm2 related to the representation of snow density |
| topic | temperature variability climate modeling land‐atmosphere coupling snow density |
| url | https://doi.org/10.1029/2021MS002880 |
| work_keys_str_mv | AT islarsimpson improvementsinwintertimesurfacetemperaturevariabilityinthecommunityearthsystemmodelversion2cesm2relatedtotherepresentationofsnowdensity AT davidmlawrence improvementsinwintertimesurfacetemperaturevariabilityinthecommunityearthsystemmodelversion2cesm2relatedtotherepresentationofsnowdensity AT seancswenson improvementsinwintertimesurfacetemperaturevariabilityinthecommunityearthsystemmodelversion2cesm2relatedtotherepresentationofsnowdensity AT cecilehannay improvementsinwintertimesurfacetemperaturevariabilityinthecommunityearthsystemmodelversion2cesm2relatedtotherepresentationofsnowdensity AT karenamckinnon improvementsinwintertimesurfacetemperaturevariabilityinthecommunityearthsystemmodelversion2cesm2relatedtotherepresentationofsnowdensity AT johnetruesdale improvementsinwintertimesurfacetemperaturevariabilityinthecommunityearthsystemmodelversion2cesm2relatedtotherepresentationofsnowdensity |