排序方式： 共有59条查询结果，搜索用时 203 毫秒
31.
On the Lagrangian and Eulerian Time Scales of Turbulence Within a Two-Dimensional Array of Obstacles
Di Bernardino Annalisa Monti Paolo Leuzzi Giovanni Querzoli Giorgio 《Boundary-Layer Meteorology》2022,184(3):375-379
Boundary-Layer Meteorology - Fields of Lagrangian ( $$T^{L}$$ ) and Eulerian ( $$T^{E}$$ ) time scales of the turbulence within a regular array of two-dimensional obstacles of unit aspect ratio... 相似文献
32.
Fabio Manca Giuseppe Capelli Francesco La Vigna Roberto Mazza Annalisa Pascarella 《Environmental Earth Sciences》2014,72(4):1083-1095
The wind effect on river water quality was illustrated by means of thermohaline measurements carried out in the Tiber River in May 2012. The survey was carried out using a boat, in stations located in the two Tiber branches: Fiumara Grande and Traiano Canal. Thermohaline variables (salinity and temperature) were used to describe the water-type patterns and to define the salt-wedge position. Although the river flow rate was rather high, saltwater intrusion happened. Wind data suggested that the more probable cause of salt-wedge intrusion was the wind action. Especially wind speeds higher than 4 m/s are able to dominate the sea current at surface layers, determining an increase in the sea level. Therefore, westerly winds determined a seawater inflow in the river mouths. 相似文献
33.
34.
Fred Kucharski Annalisa Bracco Rondrotiana Barimalala Jin Ho Yoo 《Climate Dynamics》2011,37(3-4):721-735
The focus of this paper is to assess the relative role of the north?Csouth and east?Cwest contrasts in atmospheric heating for the maintenance of the South Asian summer monsoon climatology. The juxtaposition of the Eurasian land mass and the Indian Ocean is responsible for the north?Csouth contrast, while the greater diabatic heating above the western Pacific compared to the one over the African and the tropical South Atlantic Ocean region introduces the east?Cwest gradient. With a series of idealized atmospheric general circulation model experiments, it is found that both contrasts contribute to the maintenance of the South Asian monsoon climatology, but their impact varies at regional scales. The surface atmospheric cyclone and precipitation over northern India are mainly due to the north?Csouth contrast. On the other hand, when the Indian Ocean sea surface temperatures are close to their climatological mean values, the low-level cyclone and consequent rainfall activity in the Bay of Bengal and southern India result from the east?Cwest gradient. The physical mechanism relays on the southern part of the upper-level South Asian monsoon high being forced by the east?Cwest diabatic heating contrast via Sverdrup balance. The east?Cwest heating difference controls also the strength of the Tropical Easterly Jet. Finally, the contribution of the El Ni?o Southern Oscillation to the interannual variability of the Indian monsoon is interpreted as the result of a longitudinal shift of one of the centers of diabatic heating contributing to the east?Cwest contrast. 相似文献
35.
Raffaella De Matteis Annalisa Romeo Giuseppe Pasquale Giovanni Iannaccone Aldo Zollo 《Studia Geophysica et Geodaetica》2010,54(3):367-387
A new dataset of first P-wave arrival times is used to derive the 3D tomographic model of the Campania-Lucania region in the
southern Apennines (Italy). We address the issue related to the non-uniqueness of the tomographic inversion solution through
massive numerical experimentation based on the global exploration of the model parameter space starting from a large variety
of physically plausible initial models. The average of all the realizations is adopted as the best-fit solution and the uncertainty
of the model parameters is studied using a statistical approach based on a Monte Carlo-type analysis. How the uncertainty
in the initial model, earthquake locations, and data influences the inversion result is studied by considering separately
the individual effects. Checkerboard tests are performed to estimate the resolving power of the dataset. Re-located seismicity
in a reliable new 3D tomographic model allows us to correlate the earthquake distribution with the main seismogenic structures
present in the area. 相似文献
36.
Annalisa Bracco Fred Kucharski Franco Molteni Wilco Hazeleger Camiel Severijns 《Climate Dynamics》2007,28(5):441-460
This study investigates how accurately the interannual variability over the Indian Ocean basin and the relationship between the Indian summer monsoon and the El Niño Southern Oscillation (ENSO) can be simulated by different modelling strategies. With a hierarchy of models, from an atmospherical general circulation model (AGCM) forced by observed SST, to a coupled model with the ocean component limited to the tropical Pacific and Indian Oceans, the role of heat fluxes and of interactive coupling is analyzed. Whenever sea surface temperature anomalies in the Indian basin are created by the coupled model, the inverse relationship between the ENSO index and the Indian summer monsoon rainfall is recovered, and it is preserved if the atmospherical model is forced by the SSTs created by the coupled model. If the ocean model domain is limited to the Indian Ocean, changes in the Walker circulation over the Pacific during El-Niño years induce a decrease of rainfall over the Indian subcontinent. However, the observed correlation between ENSO and the Indian Ocean zonal mode (IOZM) is not properly modelled and the two indices are not significantly correlated, independently on season. Whenever the ocean domain extends to the Pacific, and ENSO can impact both the atmospheric circulation and the ocean subsurface in the equatorial Eastern Indian Ocean, modelled precipitation patterns associated both to ENSO and to the IOZM closely resemble the observations. 相似文献
37.
38.
Annalisa?Bracco Fred?KucharskiEmail author Rameshan?Kallummal Franco?Molteni 《Climate Dynamics》2004,23(6):659-678
An atmospheric general circulation model of intermediate complexity is used to investigate the origin and structure of the climate change in the second half of the twentieth century. The variability of the atmospheric flow is considered as a superposition of an internal part, due to intrinsic dynamical variability, and an external part, due to the variations of the sea surface temperature (SST) forcing. The two components are identified by performing a 50-member ensemble of atmospheric simulations with prescribed, observed SSTs in the period 1949–2002. The large number of realizations allows the estimation of statistics of the atmospheric variability with a high confidence level. The analysis performed focuses on interdecadal and interannual variability of 500 hPa geopotential height in the Northern Hemisphere (NH) during winter. The model reproduces well the structure of the observed trend (defined as the difference in the two 25-year intervals 1977–2001 and 1952–1976), particularly in the Pacific region, and about half of the amplitude of the signal. The trend in 500 hPa height projects mainly onto the second empirical orthogonal function (EOF), both in the observations and in the model ensemble. However, differences between the modelled and the observed variability are found in the pattern of the second EOF in the Atlantic sector. SST changes associated with the El Niño southern oscillation (ENSO) are responsible for about 50% of the signal of the 500 hPa height trend in the Pacific. A second 50-member ensemble is used to evaluate the sensitivity of interdecadal variability to an increase in CO2 optical depth compatible with observed concentration changes. In this second experiment, the simulated trend includes a statistically significant contribution from the positive phase of the Arctic oscillation (AO). Such a contribution is also found in observations. Furthermore, the additional CO2 forcing accounts for part of the NH trend in near-surface temperature, and brings the zonal-mean temperature changes in the stratosphere and upper-troposphere closer to observations.
相似文献
| Fred KucharskiEmail: |
39.
40.
Davide Lazzati Gabriele Ghisellini Annalisa Celotti 《Monthly notices of the Royal Astronomical Society》1999,309(2):L13-L17
We investigate, independently of specific emission models, the constraints on the value of the bulk Lorentz factor Γ of a fireball. We assume that the burst emission comes from internal shocks in a region transparent to Thomson scattering, and before deceleration caused by the swept-up external matter is effective. We consider the role of Compton drag in decelerating fast-moving shells before they interact with slower ones, thus limiting the possible differences in the bulk Lorentz factor of shells. Tighter constraints on the possible range of Γ are derived by requiring that the internal shocks transform more than a few per cent of the bulk energy into radiation. Efficient bursts may require a hierarchical scenario, where a shell undergoes multiple interactions with other shells. We conclude that fireballs with average Lorentz factors larger than 1000 are unlikely to give rise to the observed bursts. 相似文献