Tropical singular vectors computed with linearized diabatic physics

With the introduction of diabatic processes in the forward and adjoint tang ent models of the European Centre for Medium-Range Weather Forecasts's mode l, it is possible to determine singular vectors (SVs) for situations where diabatic physics may be important in producing perturbation growth. In this paper, the linear physical parametrizations are used to compute SVs for th e tropical region, or subsets thereof, with an optimization time of 48 h. P erturbation growth is measured in terms of the so-called total energy norm, augmented with a term for specific humidity. Difficulties that may arise in computing tropical SVs, such as associated w ith spurious upper-tropospheric perturbation growth, are described. Also, t he impact on the SV structure by including a specific-humidity term in the defining norm is discussed. Using a term for specific humidity based on bac kground-error statistics in the norm. at initial time yields SVs with a mor e realistic specific-humidity vertical profile. SVs are determined in various configurations for two tropical cyclones. Res ults show that targeting in the vicinity of the cyclone is required to obta in SVs associated with the cyclone dynamics. The dominant targeted SVs for tropical cyclones show resemblance to fast-growing structures found for ide alized vortices.