Data assimilation (DA) methods for convective‐scale numerical weather prediction at operational centres are surveyed. The operational methods include variational methods (3D‐Var and 4D‐Var), ensemble methods (LETKF) and hybrids between variational and ensemble methods (3DEnVar and 4DEnVar). At several operational centres, other assimilation algorithms, like latent heat nudging, are additionally applied to improve the model initial state, with emphasis on convective scales. It is demonstrated that the quality of forecasts based on initial data from convective‐scale DA is significantly better than the quality of forecasts from simple downscaling of larger‐scale initial data. However, the duration of positive impact depends on the weather situation, the size of the computational domain and the data that are assimilated. Furthermore it is shown that more advanced methods applied at convective scales provide improvements over simpler methods. This motivates continued research and development in convective‐scale DA. Challenges in research and development for improvements of convective‐scale DA are also reviewed and discussed. The difficulty of handling the wide range of spatial and temporal scales makes development of multi‐scale assimilation methods and space–time covariance localization techniques important. Improved utilization of observations is also important. In order to extract more information from existing observing systems of convective‐scale phenomena (e.g. weather radar data and satellite image data), it is necessary to provide improved statistical descriptions of the observation errors associated with these observations.

The assimilation of surface observations using an ensemble Kalman filter (EnKF) approach is evaluated for the potential to improve short-range forecasting. Two severe weather cases are examined, in which the assimilation is performed over a 6-h period using hourly surface observations followed by an 18-h simulation period. Ensembles are created in three different ways—by using different initial and boundary conditions, by using different model physical process schemes, and by using both different initial and boundary conditions and different model physical process schemes. The ensembles are compared in order to investigate the role of uncertainties in the initial and boundary conditions and physical process schemes in EnKF data assimilation. In the initial condition ensemble, spread is associated largely with the displacement of atmospheric baroclinic systems. In the physics ensemble, spread comes from the differences in model physics, which results in larger spread in temperature and dewpoint temperature than the initial condition ensemble, and smaller spread in the wind fields. The combined initial condition and physics ensemble has properties from both of the previous two ensembles. It provides the largest spread and produces the best simulation for most of the variables, in terms of the rms difference between the ensemble mean and observations. Perhaps most importantly, this combined ensemble provides very good guidance on the mesoscale features important to the severe weather events of the day.

The baryon-baryon interaction for the complete baryon octet is investigated in a unified framework of the resonating-group method which employs the spin-flavor SU 6 wave functions with explicit color degrees of freedom. The interaction Hamiltonian is composed of the phenomenological confinement potential, the color Fermi-Breit interaction with explicit flavor symmetry breaking, and the effective meson-exchange potentials of scalar, pseudoscalar, and vector-meson types, acting between quarks. For the scalar-and vector-meson exchanges, the momentum-dependent higher-order terms are incorporated to reduce the attractive effect of the central interaction at higher energies. The single-particle potentials of the octet baryons, predicted by the G-matrix calculation, now have proper repulsive behavior in the momentum region q 1 ϭ5-20 fm Ϫ1. A moderate contribution of the spin-orbit interaction from the scalar-meson exchange is also included. As to the vector mesons, a dominant contribution is the quadratic spin-orbit force generated from the-meson exchange. This paper discusses the nucleon-nucleon interaction up to T lab ϭ800 MeV. The nucleon-nucleon phase shifts at the nonrelativistic energies up to T lab ϭ350 MeV are greatly improved, and now have attained the accuracy almost comparable to that of one-boson-exchange potentials. The deuteron properties and the low-energy observables of the nucleon-nucleon interaction are examined in the particle basis by incorporating the isospin symmetry breaking through the mass difference of the neutral and charged pions and the Coulomb effect as well. The nuclear saturation properties and the single-particle potential of the nucleon in symmetric nuclear matter are examined through the G-matrix calculation which uses the quark-exchange kernel directly.

No abstract

Using the SU 6 quark-model baryon-baryon interaction recently developed by the Kyoto-Niigata group, we calculate N N , ΛN and ΣN G-matrices in ordinary nuclear matter. This is the first attempt to discuss the Λ and Σ single-particle potentials in nuclear medium, based on the realistic quark-model potential. The Λ potential has the depth of more than 40 MeV, which is more attractive than the value expected from the experimental data of Λ-hypernuclei. The Σ potential turns out to be repulsive, the origin of which is traced back to the strong Pauli repulsion in the ΣN (I = 3/2) 3 S 1 state.

Bradykinin (BK) is a major kinin with well-documented pharmacological properties including vascular leakage and induction of a variety of cytokines. However, the intracellular signalling mechanisms by which BK induced proinflammatory cytokine production have not been fully elucidated. This study investigated the role of the extracellular signal-regulated protein kinase 1/2 (ERK 1/2) and p38 mitogen-activated protein kinase (p38 MAPK) in the BK-induced interleukin (IL)-6 and IL-8 production by human lung fibroblasts.Lung fibroblasts were stimulated with BK in the presence or in the absence of PD98059, a specific MAPK/ERK kinase-1 inhibitor, or SB203580, a specific p38 MAPK inhibitor, and IL-6 or IL-8 production and their gene expression was examined. BK-induced ERK 1/2 or p38 MAPK phosphorylation was also analysed by Western blot analysis.BK at nanomolar concentrations stimulated lung fibroblasts to produce IL-6 and IL-8 along with increased ERK 1/2 and p38 MAPK phosphorylation. BK-induced IL-6 and IL-8 synthesis was inhibited by a B2-type BK receptor antagonist. Furthermore, PD98059 or SB203580 significantly suppressed BK-induced IL-6 and IL-8 production and their gene expression.These results indicate that bradykinin-induced interleukin-6 and interleukin-8 production are at least partly mediated through the extracellular signal-related protein kinase 1/2 and p38 mitogen-activated protein kinase pathway-dependent activation in human lung fibroblasts, and suggest that bradykinin appears to be involved in the inflammatory reaction leading to acute lung injury through stimulating interleukin-6 and interleukin-8 production by lung fibroblasts. Eur Respir J 2000; 16: 452±458.

Radiation pneumonitis is a major complication of radiation therapy. However, the detailed cellular mechanisms have not been clearly defined. Based on the recognition that basement membrane disruption occurs in acute lung injury and that matrix metalloproteinase (MMP)-2 can degrade type IV collagen, one of the major components of the basement membrane, we hypothesized that ionizing radiation would modulate MMP-2 production in human lung epithelial cells. To evaluate this, the modulation of MMP-2 with irradiation was investigated in normal human bronchial epithelial cells as well as in A549 cells. We measured the activity of MMP-2 in the conditioned medium with zymography and the MMP-2 mRNA level with RT-PCR. Both of these cells constitutively expressed 72-kDa gelatinolytic activity, corresponding to MMP-2, and exposure to radiation increased this activity. Consistent with the data of zymography, ionizing radiation increased the level of MMP-2 mRNA. This radiation-induced increase in MMP-2 expression was mediated via p53 because the p53 antisense oligonucleotide abolished the increase in MMP-2 activity as well as the accumulation of p53 after irradiation in A549 cells. These results indicate that MMP-2 expression by human lung epithelial cells is involved in radiation-induced lung injury.

No abstract