Verification of boundary layer wind patterns in COSMO-REA2 using clear-air radar echoes

Pub­lished in Geosci. Mod­el Dev.,14, 6765–6780, 2021:

The ver­i­fi­ca­tion of high-res­o­lu­tion mete­o­ro­log­i­cal mod­els requires high­ly resolved val­i­da­tion data and appro­pri­ate tools of analy­sis. While much progress has been made in the case of pre­cip­i­ta­tion, wind fields have received less atten­tion, large­ly due to a lack of spa­tial mea­sure­ments. Clear-sky radar echoes could be an unex­pect­ed part of the solu­tion by afford­ing us an indi­rect look at hor­i­zon­tal wind pat­terns: regions of hor­i­zon­tal con­ver­gence attract non-mete­o­ro­log­i­cal scat­ter­ers such as insects; their con­cen­tra­tion visu­al­izes the struc­ture of the con­ver­gence field. Using a two-dimen­sion­al wavelet trans­form, this study demon­strates how diver­gences and reflec­tiv­i­ties can be quan­ti­ta­tive­ly com­pared in terms of their spa­tial scale, anisotropy (hor­i­zon­tal), and direc­tion. A long-term val­i­da­tion of the high­ly resolved region­al reanaly­sis COSMO-REA2 against the Ger­man radar mosa­ic shows sur­pris­ing­ly close agree­ment. Despite the­o­ret­i­cal­ly pre­dict­ed prob­lems with sim­u­la­tions in or near the “grey zone” of tur­bu­lence, COSMO-REA2 is shown to pro­duce a real­is­tic diur­nal cycle of the spa­tial scales larg­er than 8 km. In agree­ment with the lit­er­a­ture, the ori­en­ta­tion of the pat­terns in both datasets close­ly fol­lows the mean wind direc­tion. Con­verse­ly, an analy­sis of the hor­i­zon­tal anisotropy reveals that the mod­el has an unre­al­is­tic ten­den­cy towards high­ly lin­ear, roll-like pat­terns ear­ly in the day.

Authors: Sebas­t­ian Buschow and Petra Friederichs

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