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Section A A index 191-199 of 917 terms Previous 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 Next adiabatic trial—Older expression for the process of lifting a parcel adiabatically on a thermodynamic diagram to ascertain when convective instability will occur. adiabatic wet-bulb temperature—See wet-bulb temperature. adiabatic—See adiabatic process. adiabatically enclosed system—A thermodynamic system in which no heat or mass is transported across its boundaries. adjoint assimilation—A form of variational data assimilation in which adjoint equations are used to obtain gradients of a scalar measure of a forecast (J) with respect to model control variables. The complete assimilation generally involves an iterative procedure to reduce the cost-function in which a minimization algorithm is used to adjust initial conditions based on a sensitivity gradient (∇xJ) provided by the adjoint model. See adjoint sensitivity, variational objective analysis. adjoint equation—An equation of the form x0 = Tx1, in which the linear operator T is the adjoint of the matrix operator that satisfies (Tx1,x0) = (x1,x0), where x0 and x1 are vectors and (,) represents an inner product. If (,) is the standard dot product (Euclidean inner product) then T is simply the transpose of . See adjoint sensitivity, adjoint model, tangent linear equation. adjoint model—A model composed of adjoint equations that maps a sensitivity gradient vector, ∇xJ(t0) = T∇xJ(t1) , from a forecast time, t1, to an earlier time, t0, which can be the initial time of a forecast trajectory. J is some scalar measure of the forecast, T is a linear adjoint operator, and x is the model state vector. An adjoint model can provide a first-order (tangent linear) approximation to sensitivity in a nonlinear model. See adjoint equation, adjoint sensitivity, tangent linear equation. adjoint sensitivity—A gradient, ∇xJ, of some scalar measure of a forecast, J, with respect to the vector of model control variables, x, that can include initial conditions, boundary conditions, and parameters. The inner product (δx, ∇xJ), where δx is a perturbation vector and ∇xJ is an adjoint sensitivity vector, provides δJ, a first-order (tangent linear) approximation to the difference, ΔJ, between an unperturbed nonlinear forecast and a nonlinear forecast with control variables perturbed by δx. See adjoint model, tangent linear equation, tangent linear approximation. adjustable cistern barometer—A mercury barometer that is read by first bringing the free mercury surface in the cistern to a fixed level coincident with the zero of the scale. See Fortin barometer. admissible concentration limit—Upper limit of concentration of a substance in water that is deemed not harmful. The definition of harmful substance is regulatory dependant. Previous 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 Next