Towards a multi-year urban precipitation climatology at 100 m scale using X-band radar observations
Authors: Burgemeister Finn , Clemens Marco , Ament Felix 
Published: March 2021

&lt;p&gt;An operational, single-polarized X-band weather radar provides measurements in Hamburg&amp;#8217;s city center for almost eight years. This weather radar operates at an elevation angle (~3.5&amp;#176;) with a high temporal (30 s), range (60 m), and sampling (1&amp;#176;) resolution resulting&lt;span&gt; in a&lt;/span&gt; high information density within &lt;span&gt;the&lt;/span&gt; 20 km &lt;span&gt;scan radius&lt;/span&gt;. &lt;span&gt;Studies on short time periods (several months) proofs the performance of this low-cost local area weather radar. &lt;/span&gt;&lt;span&gt;For example, a&lt;/span&gt;&lt;span&gt; case study on a tornado in a rain event demonstrates its refined resolution &lt;/span&gt;&lt;span&gt;compared to&lt;/span&gt;&lt;span&gt; the German nationwide C-band radars. &lt;/span&gt;&lt;span&gt;Now, we aim for a eight-year precipitation climatology with 100 m resolution. This data set will enable reliable studies on urban extreme precipitation. This presentation will describe h&lt;/span&gt;&lt;span&gt;ow we &lt;/span&gt;&lt;span&gt;can&lt;/span&gt;&lt;span&gt; infer a precipitation estimate based on multi-&lt;/span&gt;&lt;span&gt;year&lt;/span&gt;&lt;span&gt; weather radar observations in the urban area of Hamburg.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;The single-polarization and &lt;span&gt;small&lt;/span&gt; &lt;span&gt;wavelength&lt;/span&gt; &lt;span&gt;comes along with&lt;/span&gt; high resolution &lt;span&gt;but at the same time&lt;/span&gt; high uncertainties. We address several sources of errors affecting th&lt;span&gt;e&lt;/span&gt; radar-based &lt;span&gt;precipitation&lt;/span&gt; estimate, like the radar calibration, alignment, attenuation, noise, non-meteorologial echoes, &lt;span&gt;and &lt;/span&gt;&lt;span&gt;&lt;em&gt;Z&lt;/em&gt;&lt;/span&gt;&lt;span&gt;-&lt;/span&gt;&lt;span&gt;&lt;em&gt;R&lt;/em&gt;&lt;/span&gt;&lt;span&gt; relation. The deployment of additional vertically pointing micro rain radars yields drop size distributions at relevant heights reducing errors effectively concerning the radar calibration and required statistical relations (&lt;/span&gt;&lt;span&gt;&lt;em&gt;k&lt;/em&gt;&lt;/span&gt;&lt;span&gt;-&lt;/span&gt;&lt;span&gt;&lt;em&gt;Z&lt;/em&gt;&lt;/span&gt;&lt;span&gt; and &lt;/span&gt;&lt;span&gt;&lt;em&gt;Z&lt;/em&gt;&lt;/span&gt;&lt;span&gt;-&lt;/span&gt;&lt;span&gt;&lt;em&gt;R&lt;/em&gt;&lt;/span&gt;&lt;span&gt; relation). We outline the performance of the correction methods for long time periods and discuss open issues and limitations.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;With this high-quality and -resolution weather radar product, refined studies on the spatial and temporal scale of &lt;/span&gt;&lt;span&gt;urban &lt;/span&gt;&lt;span&gt;precipitation will be possible. &lt;/span&gt;&lt;span&gt;This data set will be used for&lt;/span&gt;&lt;span&gt; further hydrological research in an urban area &lt;/span&gt;&lt;span&gt;within the project &lt;em&gt;Sustainable Adaption Scenarios for Urban Areas &amp;#8211; Water from Four Sides&lt;/em&gt; of the&lt;/span&gt;&lt;span&gt; Cluster of Excellence &lt;em&gt;Climate Climatic Change, and Society&lt;/em&gt; (CliCCS).&lt;/span&gt;&lt;/p&gt;