Project CONVERGE 1/13/15. How to Read CONVERGE CODAR Imagery Data Primer

Transcription

1 Hw t Read CONVERGE CODAR Imagery Data Primer Overall Ntes abut the data: Everything is in Greenwich Mean Time (GMT), which is 5 hurs ahead f the east cst. All time is presented in military time, which means it is frm 0:00 (12:00am) t 23:59 (11:59pm). Wind measurements are in m/s and surface current measurements are in cm/s, check the units carefully when lking at arrwed maps t knw which yu are lking at. 2) CODAR Imagery Current Map Viewer This website allws yu t select a specific date and hur time range t see the data frm all f the three CODAR statins. Yu can use the Date and Hur fields t input specific timeframes in which yu want t plt the data. Yu als can use the << Play (back) and Play >> (frward) buttns t have the data be animated thrugh time (using Faster and Slwer t change the speed with which the hurly graphs switch n the screen and the Stp buttn t stp the animatin). Or yu can use the Back and Frward buttns t self- select what time perid/map yu are interested in lking at. The black arrws in the water represent the directin and speed that the surface water was mving. The clr f the water under the arrws represents the different data being viewed in the map (the clr scale bar n the right and title prvide the units fr the data). The black carrt arrw in the upper right crner is the Nrth arrw. The three CODAR statins are marked with green shapes: triangle is at Palmer Statin, square is at Jubin Island, and the diamnd is at Wauwermans Island. In the zmed in data files, the black line dentes the bating limit (this is the maximum distance the scientists can g in small bats frm Palmer Statin). The red vectr pltted at the lcatin f the CODAR statins (green shapes) indicates the wind speed and directin at the statin. The red arrw at the bttm f sme maps is the scale bar fr the wind measurements and represents 10 m/s. The PLDP drp dwn menu allws yu t select the type f CODAR data yu are lking at: Raw Vectrs: This is the base bservatin frm the CODAR data. It is a plt the net mvement f water at the surface with all variables that culd impact the water mvement included like tide, wind, density currents, etc. Raw Vectrs Zm: This is the zmed in image f the Raw Vectrs CODAR data arund Palmer Statin. Divergence: This is a prcessing that estimates divergence and cnvergence frm the Raw Vectrs CODAR data. Cnvergence and divergence are presented frm the vertical mvement f water frm the surface t 1 m dwn. CODAR des nt have a depth reslutin (it cannt read dwn int the water clumn). Rather, cnvergence r divergence is inferred frm changes in the hrizntal mvement/velcity f water. If currents are crashing int each ther, scientists assume (which is a gd assumptin) that water has t

2 be frced dwn at a speed that is directly related t the hrizntal speeds f the water at the surface measured by CODAR. If currents are accelerating away frm each ther, we assume that water cmes frm deeper layers t replace it at a speed that is directly related t the hrizntal speeds f the water at the surface measured by CODAR. S, vertical mvements f water are calculated based n the measured hrizntal mvements f water. A psitive vertical mvement f the water indicates water cming frm the deeper cean t replace water that is mving away (divergence zne, red areas). Negative vertical mvement f the water indicates water that is ging dwn tward the deeper cean as water builds up in ne place because it is being pushed there (cnvergence zne, blue areas). Divergence Zm: This is the zmed in image f the Divergence CODAR data arund Palmer Statin. Divergence Trend: This is a prcessing that estimates the persistence if divergence ver the last three days frm the Divergence prcessed CODAR data. A Divergent Trend value f 1 (red) indicates that the area was always divergent ver three days, and a value f - 1 (blue) indicates that the area was always cnvergent ver three days. This is helpful in detecting regins f persistent cnvergence r divergence znes that the penguins might be using. Divergence Trend Zm: This is the zmed in image f the Divergence Trend CODAR data arund Palmer Statin. Vrticity: This is an estimate the rtatin a particle wuld feel if it were mving thrugh the Raw Vectrs CODAR data current map. Psitive values indicate that the currents are causing a particle t spin in the clckwise directin. Negative values indicate that the currents are causing a particle t spin in the clckwise directin. Scientists calculate vrticity because it helps them identify regins f spinning water, which allws us t identify regins where currents slide past each ther (shear) and/r currents frm circular patterns (eddies) that might be imprtant fr aggregatins f krill and phytplanktn. Vrticity Zm: This is the zmed in image f the Vrticity CODAR data arund Palmer Statin. Detided: This is a prcessing f the Raw Vectrs CODAR data that has the influence f tides n the mvement f water subtracted ut. Filtered: This is a prcessing f the Detided CODAR data that has remved any mvement f the water that happens ver a time perid shrter than 30 hurs t remve lnger term backgrund mvement f the water. Tidal: This is an estimate f the prtin f the water mvement in the Raw Vectrs CODAR data current map that is due t tides. The maps shw the tidal current nly ver the cverage area. The blue and yellw clrs indicate the velcity f the tidal currents measured by CODAR. Yellw are faster currents, and blue are slwer currents.

3 Current Map Images This links t a directry f flders and files f the different CODAR raw and prcessed data ver time frm the prject that yu can tggle thrugh using the Current Map Viewer. The flders include: a. 2014_11/ - This includes all f the Nvember 2014 Measured Pattern f the CODAR raw data that enables scientists t determine hw the data needs t be crrected fr the naturally ccurring variatin due t the fact that the data is being triangulated frm three CODAR statins and the ptential aspects f the envirnment that wuld distrt the data. These data are then prcessed t make the Raw Vectrs CODAR data maps. The files are labeled as: OI_PLDP_YYYY_MM_DD_HHMM.png. b. 2014_12/ - This includes all f the December 2014 Measured Pattern f the CODAR raw data. c. 2015_01/ - This includes all f the January 2015 Measured Pattern f the CODAR raw data.

4 d. detided/ (by each mnth) - This is a prcessing f the Raw Vectrs CODAR data that has the influence f tides n the mvement f water subtracted ut. The files are labeled as: OI_PLDP_YYYY_MM_DD_HHMM- detided.png.

5 e. divergence/ (by each mnth) - This is a prcessing that estimates divergence and cnvergence frm the Raw Vectrs CODAR data. Cnvergence and divergence are presented frm the vertical mvement f water frm the surface t 1 m dwn. CODAR des nt have a depth reslutin (it cannt read dwn int the water clumn). Rather, cnvergence r divergence is inferred frm changes in the hrizntal mvement/velcity f water. If currents are crashing int each ther, scientists assume (which is a gd assumptin) that water has t be frced dwn at a speed that is directly related t the hrizntal speeds f the water at the surface measured by CODAR. If currents are accelerating away frm each ther, we assume that water cmes frm deeper layers t replace it at a speed that is directly related t the hrizntal speeds f the water at the surface measured by CODAR. S, vertical mvements f water are calculated based n the measured hrizntal mvements f water. A psitive vertical mvement f the water indicates water cming frm the deeper cean t replace water that is mving away (divergence zne, red areas). Negative vertical mvement f the water indicates water that is ging dwn tward the deeper cean as water builds up in ne place because it is being pushed there (cnvergence zne, blue areas). The files are labeled as: OI_PLDP_YYYY_MM_DD_HHMM- divergence.png.

6 f. divergencetrend/ (by each mnth) - This is a prcessing that estimates the persistence if divergence ver the last three days frm the Divergence prcessed CODAR data. A Divergent Trend value f 1 (red) indicates that the area was always divergent ver three days, and a value f - 1 (blue) indicates that the area was always cnvergent ver three days. This is helpful in detecting regins f persistent cnvergence r divergence znes that the penguins might be using. The files are labeled as: OI_PLDP_YYYY_MM_DD_HHMM- divergencetrend.png.

7 g. divergencetrendzm/ (by each mnth) - This is the zmed in image f the Divergence Trend CODAR data arund Palmer Statin. The files are labeled as: OI_PLDP_YYYY_MM_DD_HHMM- divergencetrendzm.png.

8 h. divergencezm/ (by each mnth) - This is the zmed in image f the Divergence CODAR data arund Palmer Statin. The files are labeled as: OI_PLDP_YYYY_MM_DD_HHMM- divergencezm.png. i. rawzm/ (by each mnth) - This is the zmed in image f the Raw Vectrs CODAR data arund Palmer Statin. The files are labeled as: OI_PLDP_YYYY_MM_DD_HHMM- rawzm.png.

9 j. tidal/ (by each mnth) - This is an estimate f the prtin f the water mvement in the Raw Vectrs CODAR data current map that is due t tides. The maps shw the tidal current nly ver the cverage area. The blue and yellw clrs indicate the velcity f the tidal currents measured by CODAR. Yellw are faster currents, and blue are slwer currents. The files are labeled as: OI_PLDP_YYYY_MM_DD_HHMM- tidal.png.

10 k. vrticity/ (by each mnth) - This is an estimate the rtatin a particle wuld feel if it were mving thrugh the Raw Vectrs CODAR data current map. Psitive values indicate that the currents are causing a particle t spin in the clckwise directin. Negative values indicate that the currents are causing a particle t spin in the clckwise directin. Scientists calculate vrticity because it helps them identify regins f spinning water, which allws us t identify regins where currents slide past each ther (shear) and/r currents frm circular patterns (eddies) that might be imprtant fr aggregatins f krill and phytplanktn. The files are labeled as: OI_PLDP_YYYY_MM_DD_HHMM- vrticity.png.

11 l. vrticityzm/ (by each mnth) - This is the zmed in image f the Vrticity CODAR data arund Palmer Statin. The files are labeled as: OI_PLDP_YYYY_MM_DD_HHMM- vrticityzm.png.

12 24 Hur Average Currents This map represents that average surface currents speed and directin ver the past 25 hurs. The date and time range f the map is listed in the title. The clr f the arrws indicates the speed (cm/s) the surface current was traveling, s blue arrws indicate slwer speeds and yellw arrws indicate faster speeds. The three black triangles dente the lcatin f the three CODAR statins. Nrth is up n these maps. The NOTE: Data utside clr range will be saturated means that if the surface current speed was lwer r higher than the scale bar f 0-30 cm/s then that data wuld nt be included in the figure.

13 Animatin f Simulated Drifter Trajectries This link shws a daily estimate f the mvement f virtual particles released in the Raw Vectrs CODAR data current maps. The red triangle labeled PALM is at the Palmer CODAR statin, the red triangle labeled JOUB is at Jubin Island, and the red triangle labeled WAUW is at the Wauwermans Island. The red dts are the lcatins f the drifters. If they mve utside the range f ur data cverage they turn blue and stp mving. The black line trailing behind the dts indicates the path the virtual drifter tk since its release. The scientists create these simulatins because they shw them what a drifter might d if acted upn by the surface currents ver 24 hurs. This is useful if scientists want t knw what a drifting particle (like a krill r phytplanktn patch) might experience. It is als very useful fr understanding why certain gliders might drift in certain directins ver time.

14