1. Findings from hindcast runs 04/30-05/21, 2002 Part II

2. List of runs GridHot/cold startMin. mixing length in open sea (m) RUN1originalcold (from week18) 3 RUN2 Refined grid grid cold (from week18) 3 RUN3 (week18 only) originalcold2 Week18-20 (04/30-05/21)

3. Comparison of RUN1 and 3 Differences in the plume region are marginal.plume region Some differences in the estuary; larger mixing length in the plume region leads to lower salinities in the estuary.lower salinities

4. Comparison between RUN1 and 2 May 13, 2002 Differences, although still non-trivial, are much smaller than previously observed. –Temperature comparison is not good as expected. (RUN[12]/CR2325_1205a.gif)RUN[12]/CR2325_1205a.gif) –Salinity values are generally good; TSG shows RUN2 results are slightly better (RUN[12]/CR2325a_tsg_sal.gif).(RUN[12]/CR2325a_tsg_sal.gif). – This is mainly because of the cruise route being essentially east-west (RUN1/CR2325a_tsg_llgif).(RUN1/CR2325a_tsg_llgif). –There are some under-estimations of surface salinity in RUN2 (e.g., CR2325-1205a.gif), and over-estimation in RUN1 (e.g., CR2325-1223a.gif), which suggests plume is still somewhat skewed.CR2325-1205a.gif), CR2325-1223a.gif –Towards end of this week, RUN1 elevations indicate certain instability which magnifies in week20, and may partly explain the large differences between the two results in that week. (COMP-RUN1-RUN2/nf2c5).COMP-RUN1-RUN2/nf2c5

5. Comparison between RUN1 and 2 May 15, 2002 This is a better test for the model as the cruise route traverses a wider latitudes. (CR2327a_tsg_sal_map.gif)CR2327a_tsg_sal_map.gif For casts, RUN2 results capture better vertical profile (RUN[12]/CR2327_1107a.gif).RUN[12]/CR2327_1107a.gif –Cast locations are generally close to the mouth; had they been more away, the accuracy of RUN2 results might deteriorate.Cast locations For TSG, RUN1 results are slightly better (surprise!): –For this period, the wind is upwelling favorable, and plume should be moving southward; (RUN1/anim- sal_plume_min)RUN1/anim- sal_plume_m –RUN2 results generally indicate a plume bent towards north. Cf. animations of plume at min.animations of plume at m

6. Comparison between RUN1 and 2 May 15, 2002 (cont’d) However, RUN1 elevation doesn’t seem to be right; there is a large set-up in the plume and open-sea region (e.g. nf2c5).nf2c5 –This is believed to be the consequence of a larger minimum mixing length (3m) used. –As a result, the fresh water spreads faster towards the boundary and vertically downwards, creating larger baroclinic velocity. (RUN1/anim-sal_far_min.gif)RUN1/anim-sal_far_min.gif Results indicate the direction in which plume is moving is still not right with the refinement, especially for upwelling favorable winds. (RUN2/anim- sal_far_min.gif)RUN2/anim- sal_far_min.gif

7. Future work Since raising the minimum mixing length (xl) didn’t seem to make much difference except creating instability, we’d run the refined grid with original xl (2m).