Retrieving gusts from Doppler lidars

Pub­lished in Atmos. Meas. Tech., 15, 3243–3260, 2022:

Doppler wind lidars (DWLs) have increas­ing­ly been used over the last decade to derive the mean wind in the atmos­pher­ic bound­ary lay­er. DWLs allow the deter­mi­na­tion of wind vec­tor pro­files with high ver­ti­cal res­o­lu­tion and pro­vide an alter­na­tive to clas­sic mete­o­ro­log­i­cal tow­er obser­va­tions. They also receive sig­nals from alti­tudes high­er than a tow­er and can be set up flex­i­bly in any pow­er-sup­plied loca­tion. In this work, we address the ques­tion of whether and how wind gusts can be derived from DWL obser­va­tions. The char­ac­ter­i­za­tion of wind gusts is one cen­tral goal of the Field Exper­i­ment on Sub-Mesoscale Spa­tio-Tem­po­ral Vari­abil­i­ty in Lin­den­berg (FES­ST­VaL). Obtain­ing wind gusts from a DWL is not triv­ial because a mono­sta­t­ic DWL pro­vides only a radi­al veloc­i­ty per line of sight, i.e., only one com­po­nent of a three-dimen­sion­al vec­tor, and mea­sure­ments in at least three lin­ear­ly inde­pen­dent direc­tions are required to derive the wind vec­tor. Per­form­ing them sequen­tial­ly lim­its the achiev­able time res­o­lu­tion, while wind gusts are short-lived phe­nom­e­na. This study com­pares dif­fer­ent DWL con­fig­u­ra­tions in terms of their poten­tial to derive wind gusts. For this pur­pose, we devel­op a new wind retrieval method that is applic­a­ble to dif­fer­ent scan­ning con­fig­u­ra­tions and var­i­ous time res­o­lu­tions. We test eight con­fig­u­ra­tions with Stream­Line DWL sys­tems from HALO Pho­ton­ics and eval­u­ate gust peaks and mean wind over 10 min at 90 m a.g.l. against a son­ic anemome­ter at the mete­o­ro­log­i­cal tow­er in Falken­berg, Ger­many. The best-per­form­ing con­fig­u­ra­tion for retriev­ing wind gusts proves to be a fast con­tin­u­ous scan­ning mode (CSM) that com­pletes a full obser­va­tion cycle with­in 3.4 s. Dur­ing this time inter­val, about 11 radi­al Doppler veloc­i­ties are mea­sured, which are then used to retrieve sin­gle gusts. The fast CSM con­fig­u­ra­tion was suc­cess­ful­ly oper­at­ed over a 3‑month peri­od in sum­mer 2020. The CSM paired with our new retrieval tech­nique pro­vides gust peaks that com­pare well to clas­sic son­ic anemome­ter mea­sure­ments from the mete­o­ro­log­i­cal tow­er.

Offi­cial title: A new scan­ning scheme and flex­i­ble retrieval for mean winds and gusts from Doppler lidar mea­sure­ments

Authors: Stein­heuer, J., Detring, C., Beyrich, F., Löh­n­ert, U., Friederichs, P., and Fiedler, S.

Link to arti­cle