Re: seasonal variation of heat trasport in the East China Sea

Subject:

Comments:
: Dear Hiroshi, : From the moored records of temperature and velocity fields, the standard : deviation of flow averaged temperature in the East Taiwan Channel is 0.65 : deg.C during the 21 month from Sept. 1994 to May 1996. : The flow averaged temperature should be integral of v X theta / integral : of v across the interior section. Here v is the absolute meridional velocity, : so I can not calculate the flow averaged temperature from the high : resolution climatology of T and salinity derived from the observational : data. The variation range I showed you is calculated from the : modeled v and theta fields in POP. The vertically and horizontally : averaged theta (sectional mean theta) has a very small annual variation, : within 1 deg.c, in both the model and the observation. So the sectional : mean theta is significantly different with the flow averaged : temperature. : I would love to have your manuscript. Thanks. : Best Regards, : Dongxiao : : Dear Dongxiao, : : Thanks for your reply. : : : We did not calculate the flow averaged temperature theta_K (note the : : : flow averaged temperature is defined as theta_K = temperature transport : : : / volume transport) for the combined flow in the ETC and Taiwan Strait. : : : The flow averaged temperature we calculated from the moored data in the : : : ETC is 19.79+/-0.65 degC. This value has little change with time just as : : : the case in the Florida Current (Molinari et al., 1990), and this is the : : : reason why a very tight linear relationship exist between the : : : temperature transport and volume transport in the ETC. But the flow mean : : : temperature in the shallow Taiwan Strait should have seasonal variation. : : In my opinion, the tight linear relationship between temp transport and volume transport does not show that theta_K (flow weighted mean temp) has nearly a constant value, but show only the fact that the variation range of theta_K is much smaller than its annual mean value. This does not means that we can neglect the variation of theta_K with respect to volume transport. Also we should remind that even small change of theta_K causes large change of Q_K because Q_K depends the difference of theta_K from theta_I as shown in your Eq.(1). Theta_K may have a constant value only when the baroclinic component of temp transport is vanished AND vertically averaged theta has a constant value. But I think it will never be happened in nature. : : : I hate to show you the seasonal variation of the flow averaged : : : temperature in the interior ocean in POP model (a very nice high : : : resolution ocean model run by Los Alomas National Laboratory group), : : : because it is very large (can be from 10 to 20 deg C seasonally). : : : The reason is because the ocean at this latitude response to the wind : : : forcing by barotropic flow on seasonal time scales or high frequency : : : (see the figure of the transport variation in temperature classes and : : : Boning et al., 1994, Wilkin et al., 1995, as well as the thesis of two : : : WHOI students as recommended by Alison's comment.) : : I intended to ask you to show me the seasonal variation of the flow averaged temperature or vertically and horizontally averaged temp in the interior ocean not in POP model but in your high resolution climatology data along the 24?<N section of the Pacific. : : : : For the estimation of flow averaged temperature not only in the interior ocean but also in the Kuroshio region, we (Shiro Imawaki and others analyzing meridianal heat transport across 30 deg?@N) have the same problem. I think not only the estimation of variability of Q_I in the second line but also theta_I in the first line of your Eq.(1) is the most important contributions of POP model. : : : : : Another concern about the heat transport estimate is the East Ryukyu Current. : : : We still know too little about its mean state and variability. Considering the : : : importance of the heat transport by the western boundary current and the : : : Kuroshio recirculation to the climate variability (see Bill Johns's : : : comment on Bo Qiu's poster), a more extensive study about the ERC is : : : necessary. Have Jananese scientists considered to have moored : : : measurements on this current? If you or other Japanese scientists have any : : : plans, we (my advisors, Tom Lee and Bill Johns) would be very interested in any : : : type of collaboration. : : Independent from KOP suggested by Mark Wimbush in another comment in this forum, my group has been studying the northeastward current southeast of Amami-Ohshima Island, southern limit of Tokara Strait, using moored current meters at three sites and combined use of TOPEX/POSEIDON altimeter data with ad-hoc ship-mounted ADCP data along a grand track of T/P. We have confirmed the existence of a rather steady strong (more than 40 cm/s) northeastward current in the top 500 m over continental slope shallower than 2000 m depth. A part of this study was presented WPGM2000 held at Tokyo in this June and will be presented in PORSEC2000 being held at Goa, India, in coming December. I would send you a copy of manuscript for its proceedings. : : : P.S. You paper Ichikawa and Beardsley (1993) is really one of my : : : favorate. Much of my initial knowledge about the Kuroshio in the East : : : China Sea was gained from reading it. : : I am very happy to hear from you that our DSR paper helped you much. : : With best Regards, : : Hiroshi