A 3D-variational data assimilation scheme for a quasi-geostrophic channel model (Morss. 1998) is used to study the structure of the background error and its relationship to the corresponding bred vectors. The "true" evolution of the model atmosphere is defined by an integration of the model and "rawinsonde observations" are simulated by randomly perturbing the true... https://www.adaptsurvival.com/product-category/organic-soap/