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        <span style="font-family:Georgia;font-size:16px;">Dear all,</span>
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        <span style="font-family:Georgia;font-size:16px;"><br>
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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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