<html xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<meta name="Generator" content="Microsoft Word 15 (filtered medium)">
<style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:"Helvetica Neue";
panose-1:2 0 5 3 0 0 0 2 0 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:#0563C1;
text-decoration:underline;}
p.MsoListParagraph, li.MsoListParagraph, div.MsoListParagraph
{mso-style-priority:34;
margin-top:0in;
margin-right:0in;
margin-bottom:0in;
margin-left:.5in;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
p.p1, li.p1, div.p1
{mso-style-name:p1;
margin:0in;
font-size:10.0pt;
font-family:"Helvetica Neue";}
p.p2, li.p2, div.p2
{mso-style-name:p2;
margin:0in;
font-size:10.0pt;
font-family:"Helvetica Neue";}
span.apple-converted-space
{mso-style-name:apple-converted-space;}
span.EmailStyle22
{mso-style-type:personal-reply;
font-family:"Calibri",sans-serif;
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
/* List Definitions */
@list l0
{mso-list-id:454104551;
mso-list-type:hybrid;
mso-list-template-ids:-1907295812 67698705 67698713 67698715 67698703 67698713 67698715 67698703 67698713 67698715;}
@list l0:level1
{mso-level-text:"%1\)";
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-.25in;}
@list l0:level2
{mso-level-number-format:alpha-lower;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-.25in;}
@list l0:level3
{mso-level-number-format:roman-lower;
mso-level-tab-stop:none;
mso-level-number-position:right;
text-indent:-9.0pt;}
@list l0:level4
{mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-.25in;}
@list l0:level5
{mso-level-number-format:alpha-lower;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-.25in;}
@list l0:level6
{mso-level-number-format:roman-lower;
mso-level-tab-stop:none;
mso-level-number-position:right;
text-indent:-9.0pt;}
@list l0:level7
{mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-.25in;}
@list l0:level8
{mso-level-number-format:alpha-lower;
mso-level-tab-stop:none;
mso-level-number-position:left;
text-indent:-.25in;}
@list l0:level9
{mso-level-number-format:roman-lower;
mso-level-tab-stop:none;
mso-level-number-position:right;
text-indent:-9.0pt;}
ol
{margin-bottom:0in;}
ul
{margin-bottom:0in;}
--></style>
</head>
<body lang="EN-US" link="#0563C1" vlink="#954F72" style="word-wrap:break-word">
<div class="WordSection1">
<p class="MsoNormal">Hi Helene,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Definitely have some pointers. <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<ol style="margin-top:0in" start="1" type="1">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1">Looking at your figure VT_closure_issue I see that you are multiplying NVEL*hFacC. In fact, instead of the NVEL * hFacC terms you should use the fields called UVELMASS and VVELMASS.
In V4, the hFacC field changes through time. Our UVELMASS and VVELMASS terms track that variation and represent the true mean volume transports.<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1">In the c-grid system the u points start counting on the ‘west side of the grid cell and the v points start counting on the ‘south’ side of the grid cell. See the diagram “c-grid horizontal
coordinates” here: <a href="https://ecco-v4-python-tutorial.readthedocs.io/ECCO_v4_Coordinates_and_Dimensions_of_ECCOv4_NetCDF_files.html">
https://ecco-v4-python-tutorial.readthedocs.io/ECCO_v4_Coordinates_and_Dimensions_of_ECCOv4_NetCDF_files.html</a>
<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1">Consequently, when you combine tiles from ‘face 1’ with tiles from ‘face 5’ you have to shift the indices of the u’s and v’s arrays by 1. I’ve attached a pdf which I hope will make
that clear for you. The same goes for the corresponding DXG and DYG arrays. <o:p>
</o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1">The latest V4 volume flux fields with UVELMASS and VVELMASS can be found via
<a href="https://search.earthdata.nasa.gov/search">https://search.earthdata.nasa.gov/search</a> and searching for the following terms:<o:p></o:p></li></ol>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">ECCO_L4_OCEAN_3D_VOLUME_FLUX_LLC0090GRID_MONTHLY_V4R4<o:p></o:p></p>
<p class="MsoNormal">ECCO_L4_OCEAN_3D_VOLUME_FLUX_LLC0090GRID_DAILY_V4R4<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The corresponding grid geometries (e.g., DXG, DYG) are here:<o:p></o:p></p>
<p class="MsoNormal">ECCO_L4_GEOMETRY_LLC0090GRID_V4R4<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoListParagraph"><o:p> </o:p></p>
<p class="MsoNormal">-Ian<o:p></o:p></p>
<p class="MsoListParagraph"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<div>
<p class="MsoNormal" style="margin-left:.5in"><span lang="EN-GB">On 3/4/22, 5:19 PM, "ecco-support on behalf of Helene Asbjørnsen" <<a href="mailto:ecco-support-bounces@mit.edu">ecco-support-bounces@mit.edu</a> on behalf of
<a href="mailto:H.Asbjornsen@uib.no">H.Asbjornsen@uib.no</a>> wrote:<o:p></o:p></span></p>
</div>
</div>
<div>
<p class="MsoNormal" style="margin-left:.5in"><span lang="EN-GB"><o:p> </o:p></span></p>
</div>
<p class="p1" style="margin-left:.5in"><span lang="EN-GB">Hi,<span class="apple-converted-space"> </span><o:p></o:p></span></p>
<p class="p2" style="margin-left:.5in"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="p1" style="margin-left:.5in"><span lang="EN-GB">I was wondering if I could get some pointers on how to correctly calculate meridional volume transports across zonal lines on the ECCOv4 native grid.<span class="apple-converted-space"> </span><o:p></o:p></span></p>
<p class="p2" style="margin-left:.5in"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="p1" style="margin-left:.5in"><span lang="EN-GB">I’ve been looking at calc_MeridionalTransports.m, which is helpful. But I ultimately want to end up with a full 3D velocity/VT field for the North Atlantic to do further operations on (so only ending
up with one total transport value at each latitude is not ideal). <span class="apple-converted-space">
</span><o:p></o:p></span></p>
<p class="p2" style="margin-left:.5in"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="p2" style="margin-left:.5in"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="p1" style="margin-left:.5in"><span lang="EN-GB">Some details:<span class="apple-converted-space"> </span><o:p></o:p></span></p>
<p class="p1" style="margin-left:.5in"><span lang="EN-GB">I’ve extracted face 1 and 5 and pieced the fields together (recognising that VVEL is -UVEL and dx is dy for face 5). I’ve tried to integrate transports along the x-dimension of the extracted North Atlantic
area, but also along near zonal and meridional lines based on output from gcmfaces_lines_zonal.m.<span class="apple-converted-space"> </span><o:p></o:p></span></p>
<p class="p2" style="margin-left:.5in"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="p1" style="margin-left:.5in"><span lang="EN-GB">I end up not getting a near zero net transport at around 62N in the North Atlantic. The imbalance is large - around 6 Sv or so, and seems to originate from the part of the section east of Greenland.<span class="apple-converted-space"> </span><o:p></o:p></span></p>
<p class="p2" style="margin-left:.5in"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="p2" style="margin-left:.5in"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="p1" style="margin-left:.5in"><span lang="EN-GB">All help is much appreciated,<span class="apple-converted-space"> </span><o:p></o:p></span></p>
<p class="p1" style="margin-left:.5in"><span lang="EN-GB">Helene<span class="apple-converted-space"> </span><o:p></o:p></span></p>
<p class="MsoNormal" style="margin-left:.5in"><span lang="EN-GB"><o:p> </o:p></span></p>
</div>
</body>
</html>