The baroclinic primitive equation model used for short and medium range forecasting admits high frequency as well as desirable
Rossby modes. These high frequency oscillations are excited by initial imbalances between the observed mass and wind fields.
In this paper we determine and describe the normal modes of the linearized version of the general circulation model of Laboratoire
de Meteorologie Dynamique, Paris. These normal modes are then used to initialize the model through Machenhauer’s nonlinear
correction scheme. The adiabatic nonlinear normal mode initialization technique is shown to be superior to dynamic initialization
in terms of elimination of high-frequency oscillations in the forecast. Normal modes of a particular model depend on the finite
difference scheme chosen to approximate the governing system of model equations. The results presented correspond to enstrophy-conserving
finite difference scheme. 相似文献
The experiments reported here emphasize the importance of observations in the prediction of tropical cyclones. Towards this
end a symmetric numerical model in which convection, parametrized by the Arakawa-Schubert (AS) scheme, was adopted. A mean
thermodynamical state, which represents the monsoon conditions over the Bay of Bengal, with constant moist static energy for
the mixed layer was adopted. Experiments were then done with different initial conditions.
We found that tropical cyclone development measured by the central pressure was very sensitive to the initial convergence
field. In the present state of satellite technology, it was impossible to predict even a gross parameter like the central
pressure with an accuracy better than 6 mb for 12 hours. However, it was seen that under a variety of initial conditions the
final state characterized by the magnitude of the central low pressure remained practically unaltered. We suggest that, given
the necessary conditions for genesis, the final state of the cyclone acts as an attractor (regarding its central pressure)
and the diverse initial conditions, under the influence of thermodynamic forcing, will lead to the same final state. 相似文献
Summary A new entrainment/detrainment formulation in the Tiedtke’s mass flux cumulus parameterization is discussed here. Apart from
validating it with observations both in one and three dimensional cases, it is also evaluated in the light of the results
from the original Tiedtke scheme and another mass flux scheme due to Emanuel. The proposed analytical profiles of entrainment
and detrainment, easier to implement in any mass flux scheme, give reasonable results in GCM experiments. 相似文献
The major element relationships in ferromanganese (Fe-Mn) crusts from Afanasiy-Nikitin seamount (ANS), eastern equatorial
Indian Ocean, appear to be atypical. High positive correlations (r = 0.99) between Mn/Co and Fe/Co ratios, and lack of correlation of those ratios with Co, Ce, and Ce/Co, indicate that the
ANS Fe-Mn crusts are distinct from Pacific seamount Fe-Mn crusts, and reflect region-specific chemical characteristics. The
platinum group elements (PGE: Ir, Ru, Rh, Pt, and Pd) and Au in ANS Fe-Mn crusts are derived from seawater and are mainly
of terrestrial origin, with a minor cosmogenic component. The Ru/Rh (0.5–2) and Pt/Ru ratios (7–28) are closely comparable
to ratios in continental basalts, whereas Pd/Ir ratios exhibit values (<2) similar to CI-chondrite (∼1). The chondrite-normalized
PGE patterns are similar to those of igneous rocks, except that Pd is relatively depleted. The water depth of Fe-Mn crust
formation appears to have a first-order control on both major element and PGE enrichments. These relationships are defined
statistically by significant (r > 0.75) correlations between water depth and Mn/Co, Fe/Co, Ce/Co, Co, and the PGEs. Fractionation of the PGE-Au from seawater
during colloidal precipitation of the major-oxide phases is indicated by well-defined linear positive correlations (r > 0.8) of Co and Ce with Ir, Ru, Rh, and Pt; Au/Co with Mn/Co; and by weak or no correlations of Pd with water depth, Co-normalized
major-element ratios, and with the other PGE (r < 0.5). The strong enrichment of Pt (up to 1 ppm) relative to the other PGE and its positive correlations with Ce and Co
demonstrate a common link for the high concentrations of all three elements, which likely involves an oxidation reaction on
the Mn-oxide and Fe-oxyhydroxide surfaces. The documented fractionation of PGE-Au and their positive association with redox
sensitive Co and Ce may have applications in reconstructing past-ocean redox conditions and water masses. 相似文献
Co-rich Mn crusts from four different locations of the world ocean have been studied to understand the role of dissolved oxygen of the ambient seawater in the formation of Co-rich Mn crusts. WOCE (World Ocean Circulation Experiment) oxygen profiles of modern seawater in the Equatorial North Pacific Ocean, Equatorial South Indian Ocean and the North East Atlantic Ocean have been evaluated with respect to the occurrence of Co-rich Mn crusts at depths ranging from 1500 to 3200 m. The oxygen content at these depths varied from ∼90–240 µmol/kg. The oxygen minimum zone (OMZ), with oxygen contents in the range ∼45–100 µmol/kg, is located in the depth range 800–900 m in these regions. The age of the ocean crust on which seamounts formed is in the range 80.3–180 Ma. Profiles of the oxygen contents of seawater with depth in the oceans are shown to be extremely useful in establishing the optimum conditions for the formation of Co-rich Mn crusts. The use of WOCE oxygen profiles to study geochemical processes in the oceans is highly recommended. 相似文献
Global climate change governance has changed substantially in the last decade, with a shift in focus from negotiating globally agreed greenhouse gas (GHG) reduction targets to nationally determined contributions, as enshrined in the 2015 Paris Agreement. This paper analyses trends in adoption of national climate legislation and strategies, GHG targets, and renewable and energy efficiency targets in almost all UNFCCC Parties, focusing on the period from 2007 to 2017. The uniqueness and added value of this paper reside in its broad sweep of countries, the more than decade-long coverage and the use of objective metrics rather than normative judgements. Key results show that national climate legislation and strategies witnessed a strong increase in the first half of the assessed decade, likely due to the political lead up to the Copenhagen Climate Conference in 2009, but have somewhat stagnated in recent years, currently covering 70% of global GHG emissions (almost 50% of countries). In comparison, the coverage of GHG targets increased considerably in the run up to adoption of the Paris Agreement and 89% of global GHG emissions are currently covered by such targets. Renewable energy targets saw a steady spread, with 79% of the global GHG emissions covered in 2017 compared to 45% in 2007, with a steep increase in developing countries.
Key policy insights
The number of countries that have national legislation and strategies in place increased strongly up to 2012, but the increase has levelled off in recent years, now covering 70% of global emissions by 2017 (48% of countries and 76% of global population).
Economy-wide GHG reduction targets witnessed a strong increase in the build up to 2015 and are adopted by countries covering 89% of global GHG emissions (76% not counting USA) and 90% of global population (86% not counting USA) in 2017.
Renewable energy targets saw a steady increase throughout the last decade with coverage of countries in 2017 comparable to that of GHG targets.
Key shifts in national measures coincide with landmark international events – an increase in legislation and strategy in the build-up to the Copenhagen Climate Conference and an increase in targets around the Paris Agreement – emphasizing the importance of the international process to maintaining national momentum.
Summary ?A three-dimensional Ocean General Circulation Model has been developed in stretched coordinate from scratch. The same model
has been used to perform some numerical experiments to simulate the basic circulation pattern and the model variability to
atmospheric forcing. For numerical simulations 72 × 25 grid points in the horizontal directions and nine (10, 30, 75, 250,
500, 1000, 1500, 2000 and 3000 m) vertical levels are considered. The lateral boundaries are set at 60° N and 60° S. The basic
focus of the paper is on the demonstration of the performance of the model and its assessment by employing appropriate forcing
from the outputs of an atmospheric general circulation model. Hence, the model was forced with the forcing (wind and thermodynamic)
derived from the ECMWF runs from the AMIP archives. The preliminary results show the realistic simulation of basic pattern
of different fields. The model simulations show that the model is able to reproduce some of the general features of the ocean,
such as surface currents, surface temperature and salinity, mass transport and meridional heat transport. It is also to be
noted that the model is capable to capture the El-Ni?o and La-Ni?a type events.
Received April 3, 2002; revised June 6, 2002; accepted July 24, 2002
Published online: February 20, 2003 相似文献