ISCCP cloud fraction consistenty

[Li Dong]

Dear all,

I have checked "cltisccp" and the sum of high/mid/low derived from "clisccp" in the COSP outputs of our model (annual mean of 30 years), and found they are not equal. I also checked it in observation data, and they are equal. So do I miss something? Thanks in advance!

Best regards,

Li Dong

[Klein, Stephen A.]

Have you realized that cltisccp will not count the portion of clisccp for
tau < 0.3?

[Li Dong]

Dear Klein,

Thanks for replying! I have read about that threshold in the literature, but I have compared them in the same way in both the COSP outputs and the observations. And I also exclude the first bin with tau < 0.3 as following in NCL:

    high_lev_idx = ind(f->plev_bnds(:,0) .ge. 0.0 .and. \

                       f->plev_bnds(:,0) .lt. 44000.0)

    mid_lev_idx = ind(f->plev_bnds(:,0) .ge. 44000.0 .and. \

                      f->plev_bnds(:,0) .lt. 68000.0)

    low_lev_idx = ind(f->plev_bnds(:,0) .ge. 68000.0 .and. \

                      f->plev_bnds(:,0) .le. 100000.0)

    opt_idx = ind(f->tau .gt. 0.3)

    clhisccp = dim_sum_n_Wrap(f->clisccp(:,opt_idx,high_lev_idx,:,:), (/1,2/))

    clmisccp = dim_sum_n_Wrap(f->clisccp(:,opt_idx,mid_lev_idx,:,:), (/1,2/))

    cllisccp = dim_sum_n_Wrap(f->clisccp(:,opt_idx,low_lev_idx,:,:), (/1,2/))

    tmp = dim_avg_n_Wrap(cltisccp, 0)- \

          dim_avg_n_Wrap(clhisccp, 0)- \

          dim_avg_n_Wrap(clmisccp, 0)- \

          dim_avg_n_Wrap(cllisccp, 0)

    print(min(tmp))

    print(max(tmp))

where clisccp, cltisccp with units % are the mean annual cycle (12 months) of the 30-year AMIP results. The result is:

(0) -43.32574

(0) 38.15734

The MODIS outputs show the equality of "cltmodis = clhmodis+clmmodis+cllmodis".

Best regards,

Li Dong

[Klein, Stephen A.]

Dear Li,

What you report is not possible with the ISCCP simulator. This suggests to me that either the simulator has not been properly implemented in your model or that your diagnostic code below does not do what you think it is doing. Another possibility is that you are not correctly performing time averaging of the output from the result of instantaneous averages to monthly means and/or climatological averages. More careful scrutiny is needed.

Steve

[Li Dong]

Dear Steve,

I run COSP offline, so can this exclude the fault with the implementation?

Best,

Li

[Li Dong]

Dear all,

Sorry for bothering! I found my silly mistake. As you can see, I have wrongly put the plev index into the tau index! So, the COSP outputs are OK.

I hope no one will commit such error again!

Best regards,

Li