<div dir="auto">You can mean along longitude or latitude.<div dir="auto"><br></div><div dir="auto">Your aim is to reduce 1 dimension from the dataset you are using.<div dir="auto"><br></div><div dir="auto">Hope this helps.</div><div dir="auto"><br></div><div dir="auto">Cheers!!</div><div dir="auto">Soma</div></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Fri, May 21, 2021, 00:48 Chathurika via ncl-talk <<a href="mailto:ncl-talk@mailman.ucar.edu">ncl-talk@mailman.ucar.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><p style="font-family:Arial">
        <span style="font-family:Georgia;font-size:16px">Dear all,</span>
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        <span style="font-family:Georgia;font-size:16px">I want to calculate zonal mean meridional stream function using "zonal_mpsi" function. I have a dataset which is meridional velocity (time, plev, lat, lon). </span>
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        <span style="font-family:Georgia"><span style="font-size:16px"><br>
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        <span style="font-family:Georgia"><span style="font-size:16px">I am little bit confused about what is 'ps' (surface pressures).  Same dimensions as velocity but the level and unit must be pa. Could you please tell me what should I use for the ps?</span></span>
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        <span style="font-family:Georgia"><span style="font-size:16px"><br>
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        <span style="font-family:Georgia"><span style="font-size:16px">I am sorry about the silly question but please help me.</span></span>
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        <span style="font-family:Georgia"><span style="font-size:16px"><br>
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        <span style="font-family:Georgia"><span style="font-size:16px">Many many thanks </span></span>
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        <span style="font-family:Georgia"><span style="font-size:16px">and best regards,</span></span>
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Chathu<br>
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        <strong>WCH</strong>
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