{"id":405,"date":"2011-10-24T21:58:09","date_gmt":"2011-10-24T21:58:09","guid":{"rendered":"http:\/\/more.engineering.asu.edu\/windlab\/?page_id=405"},"modified":"2011-10-24T21:58:09","modified_gmt":"2011-10-24T21:58:09","slug":"vector-retrievals","status":"publish","type":"page","link":"https:\/\/labs.engineering.asu.edu\/windlab\/vector-retrievals\/","title":{"rendered":"Vector Retrievals"},"content":{"rendered":"<address><em><span style=\"text-decoration: underline\"><strong>Vector Retrieval from Coherent Doppler Lidar<\/strong><\/span><\/em> <\/address>\n<p>In order to understand how wind profiles are obtained by lidar, it is useful to review the difference between the fundamental measured product of the Doppler lidar and secondary retrieved products.\u00a0 Doppler lidars fundamentally measure a Doppler shift along their laser beam propagation path.\u00a0 Therefore, motion of the air orthogonal to the propagation path of the laser beam produces no Doppler shift.\u00a0 Consequently, the basic Doppler lidar output is the <em>radial velocity<\/em>, or the dot product of the velocity vector with the beam direction unit vector.\u00a0 Interpretation and processing of the radial velocity fields can be complex, requiring the resolution of indeterminacy in the basic data through supplementary assumptions or information. \u00a0Various wind retrieval techniques have been developed to estimate 2D and 3D vector fields from Doppler lidar data.\u00a0 Algorithms range from computationally intensive 4DVAR (four-dimensional variational data assimilation) techniques to simpler and faster methods based on volume velocity processing (VVP) and 2DVAR.\u00a0 Current techniques are generally suitable for many applications such as pollution transport studies and vertical profiling for wind farms assuming that the averaged nature of the products and underlying assumptions are understood. \u00a0Dual Doppler lidar techniques also provide accurate estimates of the 2D wind field.\u00a0 Advanced vector retrieval algorithms such as the optimal interpolation (OI) algorithm based on data assimilation technique was adapted to work with Doppler lidar data.<\/p>\n<h6><a href=\"https:\/\/labs.engineering.asu.edu\/windlab\/wp-content\/uploads\/sites\/207\/2011\/10\/Figure17_Turning_1310UTC_vectors_ext_range1.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-large wp-image-460\" title=\"Figure17_Turning_1310UTC_vectors_ext_range\" src=\"https:\/\/labs.engineering.asu.edu\/windlab\/wp-content\/uploads\/sites\/207\/2011\/10\/Figure17_Turning_1310UTC_vectors_ext_range1-1024x707.jpg\" alt=\"\" width=\"640\" height=\"441\" \/><\/a><em>Figure 1.\u00a0 Horizontal velocity vectors from OI technique on a 3.5<sup>o<\/sup> elevation conical scan showing the rotation of winds with height.\u00a0 The scan takes approximately 38 seconds to complete one revolution shown.\u00a0 The colors on the plot represent radial velocity measurements by lidar.\u00a0 Red color (positive values) represent wind moving away from the lidar and blue color (negative values) shows wind moving towards the lidar.\u00a0 Data with low SNR is not shown (white regions).(Krishnamurthy et al. 2011)<br \/>\n<\/em><\/h6>\n<h6><\/h6>\n","protected":false},"excerpt":{"rendered":"<p class=\"mb-2\">Vector Retrieval from Coherent Doppler Lidar In order to understand how wind profiles are obtained by lidar, it is useful to review the difference between the fundamental measured product of the Doppler lidar and secondary retrieved products.\u00a0 Doppler lidars fundamentally measure a Doppler shift along their laser beam propagation path.\u00a0 Therefore, motion of the air&#8230;<\/p>\n","protected":false},"author":391,"featured_media":0,"parent":0,"menu_order":5,"comment_status":"closed","ping_status":"open","template":"showcase.php","meta":{"_acf_changed":false,"footnotes":""},"class_list":["post-405","page","type-page","status-publish","hentry"],"acf":[],"_links":{"self":[{"href":"https:\/\/labs.engineering.asu.edu\/windlab\/wp-json\/wp\/v2\/pages\/405","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/labs.engineering.asu.edu\/windlab\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/labs.engineering.asu.edu\/windlab\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/labs.engineering.asu.edu\/windlab\/wp-json\/wp\/v2\/users\/391"}],"replies":[{"embeddable":true,"href":"https:\/\/labs.engineering.asu.edu\/windlab\/wp-json\/wp\/v2\/comments?post=405"}],"version-history":[{"count":0,"href":"https:\/\/labs.engineering.asu.edu\/windlab\/wp-json\/wp\/v2\/pages\/405\/revisions"}],"wp:attachment":[{"href":"https:\/\/labs.engineering.asu.edu\/windlab\/wp-json\/wp\/v2\/media?parent=405"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}