pher ic ▁surface ▁layer . ▁He ▁came ▁up ▁with ▁a ▁similar ▁concept ▁around ▁the ▁same ▁time ▁as ▁the ▁Mon in – O bu kh ov ▁similarity ▁theory ▁was ▁founded ▁in ▁the ▁Soviet ▁Union , ▁with ▁the ▁two ▁concepts ▁varying ▁slightly . ▁B using er ▁subsequently ▁spend ▁some ▁time ▁at ▁the ▁Institute ▁of ▁H ort icult ural ▁Engineering ▁of ▁W agen ingen ▁University . ▁At ▁the ▁inst itute ▁he ▁studied ▁micro cl imate ▁in ▁green h ouses ▁and ▁the ▁protection ▁of ▁cro ps ▁from ▁fro st ▁by ▁use ▁of ▁spr ink lers . ▁W ishing ▁to ▁study ▁atmos pher ic ▁science ▁further , ▁B using er ▁saw ▁no ▁options ▁to ▁do ▁so ▁in ▁the ▁Netherlands . ▁He ▁thus ▁sent ▁out ▁inqu iry ▁letters ▁to ▁different ▁univers ities ▁in ▁the ▁United ▁States , ▁and ▁in ▁ 1 9 5 6 ▁was ▁h ired ▁as ▁research ▁associate ▁by ▁the ▁University ▁of ▁Wisconsin – Mad ison . ▁ ▁In ▁ 1 9 5 8 ▁B using er ▁was ▁h ired ▁assistant ▁professor ▁at ▁the ▁University ▁of ▁Washington . ▁In ▁ 1 9 6 1 ▁he ▁was ▁promoted ▁to ▁associate ▁professor . ▁He ▁became ▁a ▁full ▁professor ▁in ▁ 1 9 6 4 . ▁B using er ▁retired ▁from ▁the ▁University ▁of ▁Washington ▁in ▁ 1 9 8 3 . ▁He ▁then ▁started ▁working ▁at ▁the ▁National ▁Center ▁for ▁At mos pher ic ▁Research ▁and ▁retired ▁fully ▁in ▁ 1 9 8 9 . ▁ ▁B using er ▁has ▁been ▁described ▁as ▁one ▁of ▁the ▁first ▁to ▁recognize