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<p>The Orbiting Carbon Observatory 2 (OCO-2) carries a hyperspectral A-band sensor that can obtain information about cloud geometric thickness (<span class="inline-formula"><i>H</i></span>). The OCO2CLD-LIDAR-AUX product retrieved <span class="inline-formula"><i>H</i></span> with the aid of collocated CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) lidar data to identify suitable clouds and provide a priori cloud top pressure (<span class="inline-formula"><i>P</i>_top</span>). This collocation is no longer possible, since CALIPSO's coordination flying with OCO-2 has ended, so here we introduce a new cloud flagging and a priori assignment using only OCO-2 data, restricted to ocean footprints where solar zenith angle&thinsp;<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>&lt;</mo><mn mathvariant="normal">45</mn><msup><mi/><mo>∘</mo></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="29pt" height="11pt" class="svg-formula" dspmath="mathimg" md5hash="16ec502caa9dbf27a4d780e57cc99066"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-13-4947-2020-ie00001.svg" width="29pt" height="11pt" src="amt-13-4947-2020-ie00001.png"/></svg:svg></span></span>. Firstly, a multi-layer perceptron network was trained to identify liquid clouds over the ocean with sufficient optical depth (<span class="inline-formula"><i>τ</i>&gt;1</span>) for a valid retrieval, and agreement with MODIS–CALIPSO (Moderate Resolution Imaging Spectroradiometer) is 90.0&thinsp;%. Secondly, we developed a lookup table to simultaneously retrieve cloud <span class="inline-formula"><i>τ</i></span>, effective radius (<span class="inline-formula"><i>r</i>_e</span>) and <span class="inline-formula"><i>P</i>_top</span> from A-band and <span class="inline-formula">CO₂</span> band radiances, with the intention that these will act as the a priori state estimate in a future retrieval. Median <span class="inline-formula"><i>P</i>_top</span> difference vs. CALIPSO is 12&thinsp;<span class="inline-formula">hPa</span> with an inter-decile range of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M12" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>[</mo><mo>-</mo><mn mathvariant="normal">11</mn><mo>,</mo><mn mathvariant="normal">87</mn><mo>]</mo><mspace linebreak="nobreak" width="0.125em"/><mrow class="unit"><mi mathvariant="normal">hPa</mi></mrow></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="65pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="72a498f1da1f4a6f69a77aeeeb1831d1"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-13-4947-2020-ie00002.svg" width="65pt" height="12pt" src="amt-13-4947-2020-ie00002.png"/></svg:svg></span></span>, substantially better than the MODIS–CALIPSO range of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M13" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>[</mo><mo>-</mo><mn mathvariant="normal">83</mn><mo>,</mo><mn mathvariant="normal">81</mn><mo>]</mo><mspace width="0.125em" linebreak="nobreak"/><mrow class="unit"><mi mathvariant="normal">hPa</mi></mrow></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="65pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="e932bb9884eef525652f01403ba16156"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-13-4947-2020-ie00003.svg" width="65pt" height="12pt" src="amt-13-4947-2020-ie00003.png"/></svg:svg></span></span>. The MODIS–OCO-2 <span class="inline-formula"><i>τ</i></span> difference is <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M15" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">0.8</mn><mo>[</mo><mo>-</mo><mn mathvariant="normal">3.8</mn><mo>,</mo><mn mathvariant="normal">6.9</mn><mo>]</mo></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="66pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="f4614f65ef68c96d0ce827c0e544225b"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-13-4947-2020-ie00004.svg" width="66pt" height="12pt" src="amt-13-4947-2020-ie00004.png"/></svg:svg></span></span>, and <span class="inline-formula"><i>r</i>_e</span> is <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M17" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">0.3</mn><mo>[</mo><mo>-</mo><mn mathvariant="normal">2.8</mn><mo>,</mo><mn mathvariant="normal">2.1</mn><mo>]</mo><mspace width="0.125em" linebreak="nobreak"/><mrow class="unit"><mi mathvariant="normal">µ</mi><mi mathvariant="normal">m</mi></mrow></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="90pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="639c4fb379db1fa17e3208e08cb7ab2d"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-13-4947-2020-ie00005.svg" width="90pt" height="12pt" src="amt-13-4947-2020-ie00005.png"/></svg:svg></span></span>. The <span class="inline-formula"><i>τ</i></span> difference is due to optically thick and horizontally heterogeneous cloud scenes. As well as an improved passive <span class="inline-formula"><i>P</i>_top</span> retrieval, this a priori information will allow for a purely OCO-2-based Bayesian retrieval of cloud droplet number concentration (<span class="inline-formula"><i>N</i>_d</span>). Finally, our cloud flagging procedure may also be useful for future partial-column above-cloud <span class="inline-formula">CO₂</span> abundance retrievals.</p>