an class="nf">small_subtide</span><span class="p">(</span><span class="n">subtide_scale</span><span class="o">=</span><span class="mf">0.</span><span class="p">,</span> <span class="n">add_nan</span><span class="o">=</span><span class="kc">False</span><span class="p">):</span>
<span class="w">    </span><span class="sd">&quot;&quot;&quot;Inspired by large tidal flow with small Qr undercurrent with 72hr period</span>
<span class="sd">    This is a tough lowpass filtering job because the diurnal band is large