Re: Zhang et al. poster

Subject:

Comments:
: Hi Alison, : Thanks for your time to lead the discussion and your intriguing : comments and suggestions, and also again for your kind support by providing : us your initial results of the North Pacific Hydrobase data set. : : Dongxiao, : : This is an interesting setup for looking at other : : people's work. I like the poster you present, though I must : : say that I found parts of it difficult to understand either : : because the text and/or figures were too small or too out of : : focus to read, or just because it was hard to view some of the : : comparisons simultaneously. I guess this is something which : : we will all get practice in, as we create our posters for : : internet viewing. : Yes, just like a real poster, we can not show the detailed interpretation of : the figures and tables, this makes it hard to understand in detail : especially the comparisons without discussion between the presenter and : viewers. This is exactly what the Forum is for. : We just submitted this paper and would like to mail a copy to you. The : mail address I have is still the one at OSU. Can you give me your : current address? : : : I haven't had a great deal of time to go through the : : poster in detail, but since I have been asked, let me pose : : a few questions and make a few comments and suggestions. : : In the introduction you mention the fairly large range in : : available estimates of heat flux across 24N, but note, that : : if one tosses out the two oldest (Talley 84 and Hastenrath 80), : : everybody else's solutions are consistent with yours to within : : what we shall assume are 1 sigma standard deviation error bars. : : I guess you could quibble about Trenberth and Solomon, but why : : bother? I would venture to guess, but please correct me if I : : am wrong, that this is because the indirect methods do include : : some estimate of seasonal variations. And the direct methods : : included some estimate in the error bar for the uncertainty : : associated with the synopticity of a hydrographic section. : : Also, note that in particular, your estimate is not only : : consistent with mine, it is also consistent with Bryden et al. : : That is, to within the uncertainties you cannot distinguish : : them. : Yes, in some sense, all the estimates are close to some medium value : within error bar (either large or small), but this can not rule out any : one or favor the medium one in representing the "truth". There are some : systematic errors in these estimates, e.g. the error of satellite : measurement and bad data coverage in the interior ocean in some previous : indirect methods as pointed out by Trenberth. One purpose of this study : is to show the variability and possible error sources for different : components and to understand what the total error could be for the method we : use. : One major difference can be distinguished between your estimate and Bryden : et al. (although close to each other within error bar) was the : different wind products chosen in the two studies (see detailed comparisons of : the four wind products in our study). Without this difference, your two : estimates could be different by only 0.1PW. : : : By the way have you seen any of the results of Alex Ganchaud's : : global inverse model? His thesis has a nice discussion on the : : errors for his model and uses the results of Stephen Jayne's : : thesis to point out that much of the seasonal variation in : : Ekman mass transport is compensated for by a depth independent : : return flow with the adjustment taking place in an inertial : : period. Therefore, as long as time mean winds are used, estimates : : of mass and heat transport from hydrographic surveys will not : : be affected by large wind-induced seasonal signals. : Great. Do you know if they have published their results or do they have : preprints? From all these results, together with Boning (1994) and : Wilkin (1995)'s model results, the fact that the seasonal variation in : Ekman mass transport is compensated for by a depth independent : return flow with the adjustment taking place almost simultaneously : has been well established. : Another fact that favoring the transbasin hydrographic surveys in estimating the : annual mean heat transport is that the interior baroclinic adjustment is so : slow that the interior baroclinic heat transport component estimated from a : single survey is not biased by seasonal variations. : Then, the only potential large seasonal bias for the single hydrographic : survey is the seasonal variability of the Kuroshio component. Though much : smaller than the Ekman heat flux, the seasonal amplitude of the Q_K is about : 0.45 PW, certainly unnegligible. : : : You might mention that your estimated eddy contribution to the : : heat flux is even smaller than the estimate used by Bryden et : : al. in determining their uncertainty. : Yes. The only backup, I can find, to the small eddy contribution at this : latitude band of the Pacific is Stammer (1998), who showed : negligible meridional eddy heat flux at this section but : quickly increased away from this latitude band. : : You have used ETC in the "methods" section before writing it : : out in the next section. I don't actually see it defined : : anywhere. You really ought have both ETC and ERC labelled : : on both versions of the geographic plots. : Thanks. : : The tiny text in the method section is almost unreadable. I am : : also confused about your use of Q_I. "Interior" as Harry : : Bryden uses it, means the interior of the basin, so that : : a term V_k <Theta_I> would never exist. What am I missing? : V_k does not exist in our Q_I calculation either. We should have : made the method section larger. (Kathy: Can you do this? Thanks.) : : The curves in the volume and temperature transport plots : : in the moored array section are not distinguishable. Did : : this plot used to be in color? : : Hydrography section: What does it mean: Levitus 1994 with : : an enhanced hydrobase? (hydrobase is derived from levitus 1994). : We have included more data between 20-30N in the hydrobase you sent to us. : These data recently available to us include the new data in NODC 1998, the new : surveys in the western Pacific, and the XBT data paired with salinity : based on T-S relationship. : : Where is Keelung and Ishigaki? : Keelung and Ishigaki are shown in the geographic map by the diamonds for : tide gauges (KL and IG). : : Why does this temperature/volume transport relationship : : exist between the Kuroshio and the Florida Current? : The flow averaged temperature in both Kuroshio and Florida Current have : little variation in time so that the temperature transport can be : estimated by the products of rho.Cd, mean temperature, and : volume transport time series, where the rho.Cd is about the same in both the : two currents. Note the flow averaged temperature in the Florida Current : is larger than that in the Kuroshio. : : Why is a large amplitude seasonal cycle across 24N in the : : Pacific surprising? : : -0.07 PW with a fairly hefty error bar is hardly a nonintuitive : : southward heat flux. Until fairly recently (1990) the sign : : of the heat flux at this latitude was in question (see : : Bryden et al). : The model simulated southward heat flux in Feb., also in Husing et al, suggest : this southward heat flux might exist at this latitude in winter due to heat : content change. : : There are probably other questions I could ask, but this : : isn't meant to be a review. By the way - the seasonal cycle : : broken into vertical and horizontal cells, and their : : differences is an interesting result, and I'll need to : : read over this last section of the poster more carefully : : before I can make any comments. : Thanks. : Best Regards, : Dongxiao