Dear all,
I am currently running SST sensitivity experiments with CAM. After reviewing many papers on the details of experimental design, I still have some questions that I would like to ask:
1. How long should the spin-up period be in CAM simulations?
In different studies, the spin-up time ranges from a few months to 10 years. Since the atmosphere in CAM can typically respond to SST anomalies within just a few months (much faster compared with other components), why do many studies still use 5 to even 10 years for spin-up?
2. Time period for comparing control and sensitivity experiments.
Some studies compare the last 30 years (for decadal-scale analyses), while others only compare results after several months of integration (for intra-seasonal lag/response studies). Although this partly depends on the research timescale (seasonal vs. decadal), why is it that in some cases atmospheric anomalies emerge within just a few months, while in other studies decades of integration are still needed?
3. Influence of the background climate state in control experiments.
In control runs, the background climate is often taken either from a pre-industrial control (pi-control), around the year 2000, or tailored to the specific study period. How much influence does this choice of background state have on the experiment results?
4. Timing of applying SST anomalies.
Some studies impose SST anomalies at the very beginning of the sensitivity experiment, while others run the model for some time (spin-up) and then branch into control and sensitivity runs (hybrid runs) where SST anomalies are introduced. Which approach is more appropriate?
5. Methods for generating ensembles.
Most experiments use ensemble simulations to reduce uncertainty. The main approaches are: (1) perturbing the initial conditions slightly at the same start time (micro-ensemble), and (2) restarting from different years of the same control simulation (macro-ensemble). Which ensemble generation method is generally more recommended?
I am currently running SST sensitivity experiments with CAM. After reviewing many papers on the details of experimental design, I still have some questions that I would like to ask:
1. How long should the spin-up period be in CAM simulations?
In different studies, the spin-up time ranges from a few months to 10 years. Since the atmosphere in CAM can typically respond to SST anomalies within just a few months (much faster compared with other components), why do many studies still use 5 to even 10 years for spin-up?
2. Time period for comparing control and sensitivity experiments.
Some studies compare the last 30 years (for decadal-scale analyses), while others only compare results after several months of integration (for intra-seasonal lag/response studies). Although this partly depends on the research timescale (seasonal vs. decadal), why is it that in some cases atmospheric anomalies emerge within just a few months, while in other studies decades of integration are still needed?
3. Influence of the background climate state in control experiments.
In control runs, the background climate is often taken either from a pre-industrial control (pi-control), around the year 2000, or tailored to the specific study period. How much influence does this choice of background state have on the experiment results?
4. Timing of applying SST anomalies.
Some studies impose SST anomalies at the very beginning of the sensitivity experiment, while others run the model for some time (spin-up) and then branch into control and sensitivity runs (hybrid runs) where SST anomalies are introduced. Which approach is more appropriate?
5. Methods for generating ensembles.
Most experiments use ensemble simulations to reduce uncertainty. The main approaches are: (1) perturbing the initial conditions slightly at the same start time (micro-ensemble), and (2) restarting from different years of the same control simulation (macro-ensemble). Which ensemble generation method is generally more recommended?