Subseasonal prediction with and without a well-represented stratosphere in CESM1

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  • 1 Climate and Global Dynamics Laboratory, National Center for Atmospheric Research, Boulder, CO
  • 2 Department of Atmospheric, Oceanic, and Earth Sciences, George Mason University, Fairfax, Virginia
  • 3 Colorado State University, Fort Collins, CO
  • 4 School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY
  • 5 NOAA/NCEP/Climate Prediction Center, College Park MD, USA
  • 6 Innovim, Inc., College Park MD, USA
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Abstract

There is a growing demand for understanding sources of predictability on subseasonal to seasonal (S2S) time scales. Predictability at subseasonal time scales is believed to come from processes varying slower than the atmosphere such as soil moisture, snowpack, sea ice, and ocean heat content. The stratosphere as well as tropospheric modes of variability, can also provide predictability at subseasonal time scales. However, the contributions of the above sources to S2S predictability are not well quantified. Here we evaluate the subseasonal prediction skill of the Community Earth System Model, version 1 (CESM1) in the default version of the model as well as a version with the improved representation of stratospheric variability to assess the role of an improved stratosphere on prediction skill. We demonstrate that the subseasonal skill of CESM1 for surface temperature and precipitation is comparable to that of operational models. We find that a better-resolved stratosphere improves stratospheric but not surface prediction skill for weeks 3 - 4.

Corresponding Author: Jadwiga H. Richter jrichter@ucar.edu Climate and Global Dynamics Laboratory (CGD), National Center for Atmospheric Research (NCAR). P. O. Box 3000 Boulder, CO 80307 USA

Abstract

There is a growing demand for understanding sources of predictability on subseasonal to seasonal (S2S) time scales. Predictability at subseasonal time scales is believed to come from processes varying slower than the atmosphere such as soil moisture, snowpack, sea ice, and ocean heat content. The stratosphere as well as tropospheric modes of variability, can also provide predictability at subseasonal time scales. However, the contributions of the above sources to S2S predictability are not well quantified. Here we evaluate the subseasonal prediction skill of the Community Earth System Model, version 1 (CESM1) in the default version of the model as well as a version with the improved representation of stratospheric variability to assess the role of an improved stratosphere on prediction skill. We demonstrate that the subseasonal skill of CESM1 for surface temperature and precipitation is comparable to that of operational models. We find that a better-resolved stratosphere improves stratospheric but not surface prediction skill for weeks 3 - 4.

Corresponding Author: Jadwiga H. Richter jrichter@ucar.edu Climate and Global Dynamics Laboratory (CGD), National Center for Atmospheric Research (NCAR). P. O. Box 3000 Boulder, CO 80307 USA
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