共查询到20条相似文献，搜索用时 31 毫秒
1.
Steven L. Morey Mark A. Bourassa Dmitry S. Dukhovskoy James J. O’Brien 《Ocean Dynamics》2006,56(5-6):594-606
A coupled ocean and boundary layer flux numerical modeling system is used to study the upper ocean response to surface heat
and momentum fluxes associated with a major hurricane, namely, Hurricane Dennis (July 2005) in the Gulf of Mexico. A suite
of experiments is run using this modeling system, constructed by coupling a Navy Coastal Ocean Model simulation of the Gulf
of Mexico to an atmospheric flux model. The modeling system is forced by wind fields produced from satellite scatterometer
and atmospheric model wind data, and by numerical weather prediction air temperature data. The experiments are initialized
from a data assimilative hindcast model run and then forced by surface fluxes with no assimilation for the time during which
Hurricane Dennis impacted the region. Four experiments are run to aid in the analysis: one is forced by heat and momentum
fluxes, one by only momentum fluxes, one by only heat fluxes, and one with no surface forcing. An equation describing the
change in the upper ocean hurricane heat potential due to the storm is developed. Analysis of the model results show that
surface heat fluxes are primarily responsible for widespread reduction (0.5°–1.5°C) of sea surface temperature over the inner
West Florida Shelf 100–300 km away from the storm center. Momentum fluxes are responsible for stronger surface cooling (2°C)
near the center of the storm. The upper ocean heat loss near the storm center of more than 200 MJ/m2 is primarily due to the vertical flux of thermal energy between the surface layer and deep ocean. Heat loss to the atmosphere
during the storm’s passage is approximately 100–150 MJ/m2. The upper ocean cooling is enhanced where the preexisting mixed layer is shallow, e.g., within a cyclonic circulation feature,
although the heat flux to the atmosphere in these locations is markedly reduced. 相似文献
2.
The response of the thermobaric characteristics of the high-latitude troposphere to short-term events attributed to solar
activity (solar cosmic rays and geomagnetic storms) has been investigated. The spatial manifestation of these disturbances
in the troposphere is shown to be of a “focal” character. It is found that the manifestation is most evident in the cold period
and depends on the properties of the underlying surface (land, ocean). The properties of the variations of the troposphere
air temperature in the manifestation “foci” on the standard isobaric surfaces, as well as the variations of the altitude profile
of temperature and the long-wave radiation flux at the upper boundary of the atmosphere, have been considered. The variations
of the heat content of the high-latitude troposphere after solar flares have been analyzed. The variation of the thermobaric
field is shown to be accompanied by the rearrangement of circulation forms in moderate and polar latitudes. The revealed properties
are completely explained within the mechanism proposed here for the solar activity effect on the climatic characteristics
of the troposphere. 相似文献
3.
Fangli Qiao Yeli Yuan Tal Ezer Changshui Xia Yongzeng Yang Xingang Lü Zhenya Song 《Ocean Dynamics》2010,60(5):1339-1355
A theoretical framework to include the influences of nonbreaking surface waves in ocean general circulation models is established
based on Reynolds stresses and fluxes terms derived from surface wave-induced fluctuation. An expression for the wave-induced
viscosity and diffusivity as a function of the wave number spectrum is derived for infinite and finite water depths; this
derivation allows the coupling of ocean circulation models with a wave number spectrum numerical model. In the case of monochromatic
surface wave, the wave-induced viscosity and diffusivity are functions of the Stokes drift. The influence of the wave-induced
mixing scheme on global ocean circulation models was tested with the Princeton Ocean Model, indicating significant improvement
in upper ocean thermal structure and mixed layer depth compared with mixing obtained by the Mellor–Yamada scheme without the
wave influence. For example, the model–observation correlation coefficient of the upper 100-m temperature along 35° N increases
from 0.68 without wave influence to 0.93 with wave influence. The wave-induced Reynolds stress can reach up to about 5% of
the wind stress in high latitudes, and drive 2–3 Sv transport in the global ocean in the form of mesoscale eddies with diameter
of 500–1,000 km. The surface wave-induced mixing is more pronounced in middle and high latitudes during the summer in the
Northern Hemisphere and in middle latitudes in the Southern Hemisphere. 相似文献
4.
P. C. Chu 《Pure and Applied Geophysics》1989,130(1):31-45
An important part of the influence of the oceans on the atmosphere is through direct radiation, sensible heat flux and release of latent heat of evaporation, whereby all of these processes are directly related to the surface temperature of the oceans. A main effect of the atmosphere on the oceans is through momentum exchange at the air-ocean interface, and this process is directly related to the surface wind stress. The sea surface temperature (SST) and the surface wind stress are the two important components in the air-ocean system. If SST is given, a thermally forced boundary layer atmospheric circulation can be simulated. On the other hand, if the surface wind stress is given, the wind-driven ocean waves and ocean currents can be computed.The relationship between SST and surface wind is a coupling of the atmosphere and the oceans. It changes a one-way effect (ocean mechanically driven by atmosphere, or atmosphere thermally forced by oceans) into two-way air-sea interactions. Through this coupling the SST distribution, being an output from an ocean model, leads to the thermally forced surface winds, which feeds back into the ocean model as an additional forcing.Based on Kuo's planetary boundary layer model a linear algebraic equation is established to link the SST gradient with the thermally forced surface wind. The surface wind blows across the isotherms from cold to warm region with some deflection angle to the right (left) in the Northern (Southern) Hemisphere. Results from this study show that the atmospheric stratification reduces both the speed and the deflection angle of the thermally forced wind, however, the Coriolis' effect increases the wind speed in stable atmosphere (Ri>10–4) and increases the deflection angle. 相似文献
5.
The possible contribution of solar and geomagnetic activity to changes in the characteristics of the main components of the climatic system—the ocean and the atmosphere—is considered and discussed. The mechanisms and models of the solar activity impact on thermobaric and climatic characteristics of the troposphere are presented. Based on a complex analysis of hydrometeorological data, it has been shown that changes in the temperature of the troposphere and the World Ocean reflect a response both to individual helio-geophysical perturbations and to long-term changes (1854–2015) of solar and geomagnetic activity. It is established that the climatic response to the influence of solar and geomagnetic activity is characterized by considerable spatio-temporal heterogeneity, is of a regional nature, and depends on the general circulation of the atmosphere. The largest contribution of solar activity to the global climate changes was observed in the period 1910–1943. 相似文献
6.
Ogurtsov M. G. Jungner H. Lindholm M. Helama S. Dergachev V. A. 《Geomagnetism and Aeronomy》2009,49(7):1056-1062
Paleoclimatological reconstructions of temperature of the Earth’s Northern Hemisphere for the last thousand years have been
studied using the up-to-date methods of statistical analysis. It has bee indicated that the quasisecular (a period of 60–130
years) cyclicity, which is observed in the climate of the Earth’s Northern Hemisphere, has a bimodal structure, i.e., being
composed of the 60–85 and 85–130 year periodicities. The possible relation of the quasisecular climatic rhythm to the corresponding
Gleissberg solar cycle has been studied using the solar activity reconstructions performed with the help of the solar paleoastrophysics
methods. 相似文献
7.
The spatial and temporal structure of the effects of solar activity (SA) and galactic cosmic ray (GCR) flux variations on the lower atmosphere circulation has been studied based on NCEP/NCAR reanalysis archive for 1948–2006 and MSLP (Climatic Research Unit, UK) data for 1873–2000. It has been shown that the GCR effects on pressure variations are characterized by a strong latitudinal and regional dependence, which is determined by specific features of the tropospheric circulation in the studied regions. The distribution of the correlation coefficients for mean yearly values of atmospheric pressure with the GCR flux intensity is closely related to the position of the main climatological fronts. The periodic (∼60 years) changes in the correlation sign of the pressure at high and middle latitudes with Wolf numbers have been revealed. It has been suggested that the changes of the sign of SA/GCR effects on atmospheric pressure are caused by the changes of the macrocirculation epochs, which, in turn, may be related to large-scale processes on the Sun. 相似文献
8.
The ocean takes up approximately 2 GT carbon per year due to the enhanced CO2 concentrations in the atmosphere. Several options have been suggested in order to reduce the emissions of CO2 into the atmosphere, and among these are CO2 storage in the deep ocean. Topographic effects of dissolution and transport from a CO2 lake located at 3,000-m depth have been studied using the z-coordinate model Massachusetts Institute of Technology general circulation model (MITgcm) and the σ-coordinate model Bergen ocean model (BOM). Both models have been coupled with the general ocean turbulence model (GOTM) in
order to account for vertical subgrid processes. The chosen vertical turbulence mixing scheme includes the damping effect
from stable stratification on the turbulence intensity. Three different topographic scenarios are presented: a flat bottom
and the CO2 lake placed within a trench with depths of 10 and 20 m. The flat case scenario gives good correlation with previous numerical
studies of dissolution from a CO2 lake. When topography is introduced, it is shown that the z-coordinate model and the σ-coordinate model give different circulation patterns in the trench. This leads to different dissolution rates, 0.1 μmol cm − 2 s − 1 for the scenario of a 20-m-deep trench using BOM and 0.005–0.02 μmol cm − 2 s − 1 for the same scenario using the MITgcm. The study is also relevant for leakages of CO2 stored in geological formations and to the ocean. 相似文献
9.
L. A. Vasilyeva G. A. Zherebtsov V. A. Kovalenko S. I. Molodykh 《Geomagnetism and Aeronomy》2009,49(8):1285-1287
The results of an analysis of the spatial-temporal variations in the tropospheric temperature regime in the Northern and Southern
hemispheres in 1948–2006 are presented. The possible effect of solar activity on the tropospheric temperature regime is discussed
in the scope of the proposed mechanism by which the heliogeophysical factors affect the climatic characteristics and atmospheric
circulation in the high-latitude troposphere through atmospheric electricity. 相似文献
10.
Oleg V. Melnichenko Nikolai A. Maximenko Niklas Schneider Hideharu Sasaki 《Ocean Dynamics》2010,60(3):653-666
Recently, prominent jet-like features of the ocean circulation, called striations, with a meridional scale of O(300–500 ;km)
and extending for thousands of kilometers in length, have been detected in satellite and in situ observations and in high-resolution numerical models. In this paper, we study quasi-stationary striations, which are best
seen in the multi-year time-averaged velocity fields. Using 1993–2002 mean dynamic ocean topography, satellite altimeter observations,
and output of the Ocean General Circulation Model for the Earth Simulator, the dynamics of the quasi-stationary striations
in the eastern parts of the subtropical North and South Pacific are examined by assessing individual terms in the time-averaged
equations of relative and potential vorticity. While non-linear effects are found to be essential in the dynamics of the striations,
rejecting some linear hypotheses forwarded in the earlier studies, the relevance of the Rhines mechanism is not confirmed.
Eddy flux does not act as a relative vorticity source for the striations. Using the potential vorticity (PV) diagnostics,
we show that the time-mean PV is not conserved along the time-mean streamlines, and on the scale of the striations these changes
in PV are largely induced by the eddy flux of layer thickness. The fact that eddy fluxes contribute to the striations’ time-mean
PV budget suggests that the striations are not a kinematical artifact of time-averaging of westward-propagating eddies. 相似文献
11.
This paper discusses the variability of surface currents around Sekisei Lagoon using a nested grid ocean circulation model.
We developed a triple-nested grid system that consists of a coarse-resolution (1/60° or ∼1.85 km) model off Taiwan, an intermediate-resolution
(1/300° or ∼370 m) model around the Yaeyama Islands, and a fine-resolution (1/900° or ∼123 m) model of Sekisei Lagoon. The
nested grid system was forced by wind and heat flux calculated from six-hourly atmospheric reanalysis data and integrated
over the period from May to July 2003. The coarse-resolution model was driven by lateral boundary conditions calculated from
daily ocean reanalysis data to include realistic variation of the Kuroshio and mesoscale eddies with spatial scales of ∼500–700 km
in the open ocean. The tidal forcing was included in the intermediate-resolution model by interpolating sea level data obtained
from a data-assimilative tidal model. The results were then used to drive the fine-resolution model to simulate the surface
water circulation around Sekisei lagoon. Model results show that (1) currents inside the lagoon are mainly driven by tide
and wind; (2) there exists a strong southwestward current along the bottom slope in the southeast portion of the lagoon; the
current is mainly driven by remote mesoscale eddies and at times intensified by the local wind; (3) the flow relaxation scheme
is effective in reducing biases along the open boundaries. The simulated currents were used to examine the retention and dispersion
of passive particles in the surface layer. Results show that the surface dispersion in the strong open ocean current region
is significantly higher than that inside the lagoon. 相似文献
12.
I. V. Kudryavtsev D. M. Volobuev V. A. Dergachev Yu. A. Nagovitsyn M. G. Ogurtsov 《Geomagnetism and Aeronomy》2016,56(7):858-862
Data on the content of the 14C cosmogenic isotope in tree rings, which were obtained as a result of laboratory measurements, are often used when solar activity (SA) is reconstructed for previous epochs, in which direct observations are absent. However, these data contain information not only about SA variations but also about changes in the Earth climatic parameters, such as the global temperature and the CO2 content in the Earth’s atmosphere. The effect of these variations on the 14C isotope content in different natural reservoirs after the last glacial termination to the middle of the Holocene is considered. The global temperature and the CO2 content increased on this time interval. In this case the 14C absolute content in the atmosphere increased on this time interval, even though the 14С to 12С isotope concentration ratio (as described by the Δ14С parameter) decreased. These variations in the radiocarbon absolute content can be caused by its redistribution between natural reservoirs. It has been indicated that such a redistribution is possible only when the rate of carbon exchange between the ocean and atmosphere depends on temperature. The values of the corresponding temperature coefficient for the 17–10 ka BC time interval, which make it possible to describe the carbon redistribution between the ocean and atmosphere, have been obtained. 相似文献
13.
We examine the seasonal mixed-layer temperature (MLT) and salinity (MLS) budgets in the Banda–Arafura Seas region (120–138°
E, 8–3° S) using an ECCO ocean-state estimation product. MLT in these seas is relatively high during November–May (austral
spring through fall) and relatively low during June–September (austral winter and the period associated with the Asian summer
monsoon). Surface heat flux makes the largest contribution to the seasonal MLT tendency, with significant reinforcement by
subsurface processes, especially turbulent vertical mixing. Temperature declines (the MLT tendency is negative) in May–August
when seasonal insolation is smallest and local winds are strong due to the southeast monsoon, which causes surface heat loss
and cooling by vertical processes. In particular, Ekman suction induced by local wind stress curl raises the thermocline in
the Arafura Sea, bringing cooler subsurface water closer to the base of the mixed layer where it is subsequently incorporated
into the mixed layer through turbulent vertical mixing; this has a cooling effect. The MLT budget also has a small, but non-negligible,
semi-annual component since insolation increases and winds weaken during the spring and fall monsoon transitions near the
equator. This causes warming via solar heating, reduced surface heat loss, and weakened turbulent mixing compared to austral
winter and, to a lesser extent, compared to austral summer. Seasonal MLS is dominated by ocean processes rather than by local
freshwater flux. The contributions by horizontal advection and subsurface processes have comparable magnitudes. The results
suggest that ocean dynamics play a significant part in determining both seasonal MLT and MLS in the region, such that coupled
model studies of the region should use a full ocean model rather than a slab ocean mixed-layer model. 相似文献
14.
ＧｒａｖｉｔａｔｉｏｎａｌｅｆｆｅｃｔｏｆｗａｔｅｒｃｉｒｃｕｌａｔｉｏｎｉｎｔｈｅｎｏｒｔｈｗｅｓｔＹｕｎｎａｎＭｉｎ－ＹｕＪＩＡ；（贾民育）Ｓｈａｏ－ＡｎＳＵＮ；（孙少安）Ａｉ－ＭｉｎＸＩＡＮＧ；（项爱民）ａｎｄＤｏｎｇ－ＺｈｉＬＩＵ（刘冬至）（... 相似文献
15.
High-resolution oxygen isotope records over the last 2249 ka (MIS 1–86) have been obtained from cores of the upper section
(105.08 m) at ODP Site 1143 (water depth of 2772 m) drilled in the Nansha area, southern South China Sea. The sampling resolution
is at about 2 ka intervals, resulting in one of the best oxygen isotope records over the global ocean. The oxygen isotope
curves, displaying details in the Pleistocene glacial cycles, have revealed a nearly 300 ka long stage of transition from
a predominant 40 ka to 100 ka periodicity. Therefore, the “Mid-Pleistocene Revolution” should be considered as a process of
transition rather than an abrupt change. Within the 100 ka glacial cycles, the changes in tropical sea surface water were
found to lead those in high-latitude ice sheet. Our comparisons show that the ice sheet expansion and the glacial stage extension
in the Northern Hemisphere with the 100 ka cycles must have been driven not by ice sheet itself, but by processes outside
the high latitudes of the Northern Hemisphere. 相似文献
16.
Origin of the Red Earth sequence on the northeastern Tibetan Plateau and its implications for regional aridity since the middle Miocene 总被引：4，自引：0，他引：4
Desiccation in the interior of Asia is an important aspect of paleoclimate change during the Cenozoic era[1,2]. Research[3,4] shows that the widely distributed loess deposits in China were mainly transported by northwesterly and northerly winds from deserts and the Gobi region; in addition, an indispensable re- quirement for the generation of aeolian sediment is the presence of dry lands in central Asia[5,6]. The aeolian deposits in China provide an especially useful record of desiccation pr… 相似文献
17.
This study examines the circulation and associated monthly-to-seasonal variability in the Caribbean Sea using a regional ocean
circulation model. The model domain covers the region between 99.0 and 54.0°W and between 8.0 and 30.3°N, with a horizontal
resolution of 1/6°. The ocean circulation model is driven by 6-hourly atmospheric reanalysis data from the National Center
for Environmental Prediction and boundary forcing extracted from 5-day global ocean reanalysis data produced by Smith et al.
(Mercator Newsletter 36:39–49, 2010), and integrated for 7 years. A comparison of model results with observations demonstrates that the regional ocean circulation
model has skill in simulating circulation and associated variability in the study region. Analysis of the model results, as
well as a companion model run that uses steady annual mean forcing, illustrates the role of Caribbean eddies for driving monthly-to-seasonal
circulation variability in the model. It is found that vertically integrated transport between Nicaragua and Jamaica is influenced
by the interaction between the density perturbations associated with Caribbean eddies and the Nicaraguan Ridge. The impact
of Caribbean eddies squeezing through the Yucatan Channel is also discussed. 相似文献
18.
Jin-Song von Storch 《Ocean Dynamics》2003,53(1):11-20
The three-dimensional time-mean density distribution in the ocean is determined not only by the time-mean fluxes of heat
and freshwater at the sea surface, but also by time-mean vertical currents and time-mean density fluxes due to oceanic transients
excited by fluctuating fluxes at the sea surface. The effects of these various processes on the global density fields are
assessed using a balance equation of the variance of spatial density anomalies and a millennium integration with an atmosphere–ocean
general circulation model. It is found that spatial density anomalies are generated by the time-mean heat fluxes at the sea
surface and destroyed by the time-mean surface freshwater flux, by sinking of dense water and rising of less dense water,
and finally by density fluxes associated with transients. The last two processes take place essentially in the oceanic interior.
Since density fluxes of transient eddies act to reduce the existing density differences between the Atlantic/Southern Oceans
and the other oceans, their presence could affect the global density balance, and from that the thermohaline circulation and
the stability of this circulation.
Received: 4 October 2001 / Accepted: 10 October 2002
Responsible Editor: Richard J. Greatbatch
Acknowledgements I thank Ulrich Cubasch and his colleagues for providing me with the ECHAM3/LSG integration, Peter Müller and Richard Greatbatch
for valuable suggestions. 相似文献
19.
Precipitation variation in the northeastern Tibetan Plateau recorded by the tree rings since 850 AD and its relevance to the Northern Hemisphere temperature 总被引：17，自引：2，他引：17
John K. Kutzbach 《中国科学D辑(英文版)》2006,49(4):408-420
With their high resolution and reliability, tree rings play a very important role in global climate change study. The long tree-ring chronology is considered as one of the most important information sources to study the climatic change in the past several thousands years. In recent years, the tree-ring researches in China have made great progress, and the temperature and precipita- tion in some areas were reconstructed[1-20] which on- tributed to the global change studies in China. Due to the… 相似文献
20.
A circum-earth shear zone at low-latitudes and episodic large earthquakes in it and the circum-Pacific seismic zone 总被引：1，自引：0，他引：1
MA Zongjin DU Pinren REN Jinwei & GAO Xianglin . Institute of Geology China Earthquake Administration Beijing China . Institute of Earthquake Science China Earthquake Administration Beijing China 《中国科学D辑(英文版)》2006,49(9):897-903
Although the temporal and spatial distribution of earthquakes looks like non-uniform, it is not com- pletely random. Locations of seismic zones are associ- ated with active tectonics. On a global or regional scale, several major or great earthquakes occur… 相似文献