Observation of sensible and latent heat flux profiles with lidar

• Main Authors: A. Behrendt, V. Wulfmeyer, C. Senff, S. K. Muppa, F. Späth, D. Lange, N. Kalthoff, A. Wieser
• Format: Article
• Language: English
• Published: Copernicus Publications 2020-06-01
• Series: Atmospheric Measurement Techniques
• Online Access: https://www.atmos-meas-tech.net/13/3221/2020/amt-13-3221-2020.pdf

<p>We present the first measurement of the sensible heat flux (<span class="inline-formula"><i>H</i></span>) profile in the convective boundary layer (CBL) derived from the covariance of collocated vertical-pointing temperature rotational Raman lidar and Doppler wind lidar measurements. The uncertainties of the <span class="inline-formula"><i>H</i></span> measurements due to instrumental noise and limited sampling are also derived and discussed. Simultaneous measurements of the latent heat flux profile (<span class="inline-formula"><i>L</i>)</span> and other turbulent variables were obtained with the combination of water-vapor differential absorption lidar (WVDIAL) and Doppler lidar. The case study uses a measurement example from the HOPE (HD(CP)<span class="inline-formula">²</span> Observational Prototype Experiment) campaign, which took place in western Germany in 2013 and presents a cloud-free well-developed quasi-stationary CBL. The mean boundary layer height <span class="inline-formula"><i>z</i>_i</span> was at 1230&thinsp;m above ground level. The results show – as expected – positive values of <span class="inline-formula"><i>H</i></span> in the middle of the CBL. A maximum of (<span class="inline-formula">182±32</span>)&thinsp;W&thinsp;m<span class="inline-formula">⁻²</span>, with the second number for the noise uncertainty, is found at 0.5 <span class="inline-formula"><i>z</i>_i</span>. At about 0.7 <span class="inline-formula"><i>z</i>_i</span>, <span class="inline-formula"><i>H</i></span> changes sign to negative values above. The entrainment flux was <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">62</mn><mo>±</mo><mn mathvariant="normal">27</mn><mo>)</mo></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="53pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="237aead43ca935715b3ac2e3e902abab"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-13-3221-2020-ie00001.svg" width="53pt" height="12pt" src="amt-13-3221-2020-ie00001.png"/></svg:svg></span></span>&thinsp;W&thinsp;m<span class="inline-formula">⁻²</span>. The mean sensible heat flux divergence in the observed part of the CBL above 0.3 <span class="inline-formula"><i>z</i>_i</span> was <span class="inline-formula">−0.28</span>&thinsp;W&thinsp;m<span class="inline-formula">⁻³</span>, which corresponds to a warming of 0.83&thinsp;K&thinsp;h<span class="inline-formula">⁻¹</span>. The <span class="inline-formula"><i>L</i></span> profile shows a slight positive mean flux divergence of 0.12&thinsp;W&thinsp;m<span class="inline-formula">⁻³</span> and an entrainment flux of <span class="inline-formula">(214±36)</span>&thinsp;W&thinsp;m<span class="inline-formula">⁻²</span>. The combination of <span class="inline-formula"><i>H</i></span> and <span class="inline-formula"><i>L</i></span> profiles in combination with variance and other turbulent parameters is very valuable for the evaluation of large-eddy simulation (LES) results and the further improvement and validation of turbulence parameterization schemes.</p>