Nudging E-Series Experiments


Synopsis:

The E-Series experiments are longer term CESM runs on the order of years for which the history outputs are smaller and less frequent. These outputs are primarily for AMWG diagnostics and statistical analysis of model results.

Ideally, the experiments will be partitioned into nice, clean, neat, stand-alone studies. However, since the nudging functionality, is still under development there will likely be some cross-over as improvements and adjustments are made to address unforeseen problems.


Preliminary Information:

As the nudging module has undergone initial development, some preliminary long-term runs were conducted using 2 years of YOTC data. The results of those runs are not included here, but they may on occasion be referenced and compared with the E-series results.

Two significant changes to the nudging tendencies have been made since then.

Initially the nudging tendencies were calculated and applied at the end of the tphysbc() routine. Validation tests indicated that this placed the nudging between the contending tendencies of convective processes in tphysbc() and diffusive processes in the subsequent tphysac() routine. To avoid being in the middle of this tug-of-war, the nudging tendencies were moved to the end of tphysac() [An alternative possibility is to move the tendencies to the beginning of tphysbc()].

Also revealed was that the temperature nudging was off by a factor of Cp. While temperature is used as a state variable in the dynamical core, dry static energy is used for calculations in the physics package. In the initial development, a factor of Cp was erroneously left out in the conversion which lead to negligible (1/Cp) temperature nudging tendencies.

The experiments here will begin with V2 of the nudging module which incorporates these and numerous other small changes. Currently, validation tests show that nudging effectively drives the model toward observations. Still outstanding in the nudging development is the inability to apply consistent surface forcing (fluxes), which leads to a "small" diurnally varying bias observed over the convective centers in South America and Africa. This will be resolved once the appropriate surface values are added to the preprocessed nudging data sets. Also, there is the still unresolved problem of instability when nudging tendencies are not updated frequently enough.

As further development and revisions are made, they will be appropriately documented from this starting point.


Experiment Case Names:

E-series experiments are indexed using the tag "Ennn.mmm" in the case names of the relevant CESM runs, where Ennn refers to the study being undertaken, and mmm refers to the individual CESM runs used in the study.
Case names follow the CESM convention:


<compset char>.<code base>.<compset shortname>.<res shortname>[.opt_desc_string].<nnn>[opt_char]

  example:   f.e13b6.FAMIPC5.ne30_ne30.NudgeV2_E000.001
f                  ==> First character of compset
e13b6         ==> CESM tag:    cesm1_3_beta06
FAMIPC5   ==> COMPSET short name
ne30_ne30 ==> RESOLUTION short name
NudgeV2   ==> Description string ( V2 of nudging module)
E000.001   ==> E-series study 000, CESM run 001


Index of Nudging Studies:

E-series Nudging Studies:
Nudging Data/Resolution
E000: YOTC Low Resolution Atmosphere Only Nudging            
[YOTC/ne30]
E001: CLUBB Response to Nudging 
[YOTC/ne30]
E002:
E003:






Table of All E-series Experiments:

   [ADD link to the table containing a record of all E-series experiments here]







                E000: YOTC Low Resolution Atmosphere Only Nudging

Description:

Using the current nudging module (V2), the goal of this study is to run the low resolution(ne30) atmosphere-only experiments for various nudging scenarios using YOTC data.

Summary of Results:






                E001: CLUBB Response to Nudging

Description:

Results from E000 showed that temperature nudging has an adverse effect on annual mean precipitation values. Since the ZM(default) and CLUBB parameterize convection differently, carry out nudging experiments using CLUBB and evaluate the precipitation response.

Summary of Results:





                E002:

Description:



Summary of Results: