Decadal Trends in Oxygen Concentration in Subsurface Waters of the Northeast Pacific Ocean

Previous studies have shown decreasing oxygen concentration (O₂) in subsurface waters of the continental slope from California to Canada since about 1980. With longer time series we show that from southern California to northern Canada increasing O₂ preceded these decreases from 1950 to about 1980. Because there has been no clear trend since 1950, we cannot yet conclude that anthropogenic climate change is the cause of these decreasing trends after 1980. These findings are based mainly on O₂ on the 26.7 potential density (σ_θ) surface in the region north of 30°N and east of 170°W, covering both the continental margin and deep-sea regions. On the continental slope, O₂ increased at most locations by 10 to 20?µmol?kg^?1 to about 1980, followed by declines of similar magnitude in recent years. Changes in O₂ were associated with changes in temperature of the opposite sign south of 37°N, but correlation of temperature and O₂ is irregular in more northerly locations. At all locations, temperature-related solubility change was a minor cause of these O₂ trends. In deep-sea waters, O₂ decreased with time with a more rapid decrease from about 1995 to about 2003. At Ocean Station P (OSP; 50°N, 145°W), which has the longest uninterrupted record of observations, significant linear trends of ?0.4 to ?0.5?µmol?kg^?1?y^?1 were found on the 26.5, 26.7, and 26.9 σ_θ surfaces. In addition, a significant sinusoidal oscillation of period 18.61 years and amplitude of 18?µmol?kg^?1 was found on the 26.9 σ_θ surface at OSP and a station 400?km to the east, which fits reasonably well with the lunar nodal cycle. The phase of this oscillation was identical at both locations. Clear evidence of similar variability did not emerge at other open-ocean locations or along the continental slope.     

Molecular dissipation of turbulent fluctuations in the convective mixed layer part II: Height variations of characteristic time scales and experimental test of molecular dissipation models

Extensive turbulence measurements from the Limagne and Beauce experiments were used to compute a characteristic time scale of the turbulence field (Τ = second moment/dissipation rate) for turbulent kinetic energy, temperature and humidity variances, and temperature-humidity covariance. The height variations of these time scales were analysed. The characteristic half-time scale Τ/2 of the turbulent velocity field was found, as expected, to be of the same order of magnitude as the large-eddy time scale Τ _L = Z_i/w*, showing that the turbulence structure is controlled by large eddies in the bulk of the mixed layer. The increase of Τ/2 above z/Z _i ～- 0.7 implies, however, that this time scale is no longer relevant to destruction of turbulent kinetic energy in the statically stable region with negative heat fluxes. An effective time scale Τ_eff, introduced by Zeman (1975), has been computed and its behaviour discussed. The scales for θ′ ², q′², and θ′q′ were found to be much shorter than Τ. Furthermore, a significant difference in behaviour was also revealed between the characteristic time scales of temperature and humidity fields in the stable layer. By using these experimental estimates, we tested some of the models for molecular dissipations, which are currently in use in higher order closure atmospheric boundary-layer models. The parameterized dissipation rates for θ′ ², and q′ ² agree well qualitatively with experimental estimates in the bulk of the mixed layer. In the stable layer, however, the parameterized dissipation rate ε _θ tends to become larger than the experimental ones although the parameterized dissipation rate ε _q still agrees with the experimental ones. For the molecular dissipation of θ′q′, this current model becomes physically inconsistent in the middle part of the mixed layer, because this term may become a production term for temperature-humidity covariance.     

Effect of the variation in the lower tropospheric temperature on the wind onset of the Indian summer monsoon

There is a large thermal contrast between the Arabian Peninsula and India (Δθ _AI) at the mature stage of the Indian summer monsoon (ISM). The forming process of Δθ _AI is investigated analyzing various datasets. It forms earlier in the lower troposphere than in the middle and upper layers. The potential temperature in the lower troposphere over the west coast of India (θ _IW) abruptly decreases in advance of the rapid enhancement of the westerly wind over the Arabian Sea corresponding to the ISM onset. Such a process was observed for all the target years and the rapid decrease in θ _IW could trigger the ISM onset. The decrease in θ _IW had two patterns. In one case, cooler air is brought by the strong winds around a cyclone over the Arabian Sea. In another case, θ _IW decreases gradually by a synergy of a southwesterly wind over the Arabian Sea and the enlargement of Δθ _AI.     

Possibility of Solid Hydrometeor Growth Zone Identification Using Radar Spectrum Width

In this study, the correlation between simulated and measured radar velocity spectrum width(σ_v) is investigated. The results show that the dendrites growth zones(DGZs) and needles growth zones(NGZs) mostly contain dendrites(DN) and needles(NE), respectively.Clear σ_v zones(1.1 < σ_v(m s^–1) < 1.3 and 0.3 < σ_v(m s^–1) < 0.7 for the DGZ and NGZ, respectively) could be identified in the case studies(27 and 28 February 2016) n...     

Molecular dissipation of turbulent fluctuations in the convective mixed layer part I: Height variations of dissipation rates

During the Limagne and Beauce experiments, the INAG-IGN Aerocommander FL 280 aircraft made extensive ‘in situ’ measurements of turbulent fluctuations in diurnally evolving convective boundary layers. In this paper, these measurements were used to investigate characteristics of the molecular dissipation of turbulent fluctuations through the mixed layer and well into the overlying stable layer. The dimensionless dissipation rates of turbulent kinetic energy, temperature and humidity variances, and temperature-humidity covariance (ψ, ψ_θ, ψ _qand ψ _θq) were computed and their height variations analysed. The behaviour of the dissipation rate ψ was found to differ significantly from those observed for the other rates. In the lowest region of the mixed layer, ψ does not obey the local free convection prediction. Instead, it follows practically a relationship similar to the one established in the surface layer by Wyngaard et al. (1971). The dissipation rate ψ remains fairly constant in the bulk of the mixed layer (0.3 ≤ z/Z _i≤ 0.8) and shows a very rapid decrease above the inversion. These results confirm those reported previously from the Minnesota and Ashchurch data by Kaimal et al. (1976), Caughey and Palmer (1979), etc. The height variations for the other dissipation rates were found to obey, as expected, the (z/Z _i)^-4/3 decrease predicted under the local free convection similarity hypothesis in the lowest region of the mixed layer. This region extends to the height z/Z _i- 0.4, 0.1, and 0.3, respectively, for ψ_θ, ψ_q, and ψ_θq. Above these levels, the dissipation rates ψ_θ and ψ_q show, on average, a slight increase to reach peak-values near the mixed-layer top, while the ‘dissipation’ rate ψ _θqchanges sign from positive to negative around the height z/Z _i, - 0.7. These characteristics confirm the fact that the structures of temperature and humidity fluctuations are considerably affected by their entrainment-induced fluctuations. Therefore, an attempt has been made to non-dimensionalize the dissipation rates near the mixed-layer top with the interfacial scaling factors.     

Interannual variability of North Pacific eastern subtropical mode water formation in the 1990s derived from a 4-dimensional variational ocean data assimilation experiment

The interannual variability of eastern subtropical mode water (ESTMW) formation in the North Pacific is examined using a new ocean dataset constructed by a 4-dimensional variational data assimilation experiment covering the decade of the 1990s. The volume of newly formed ESTMW varies due to interannual variability in the following three physical processes taking place in the surface layer: (1) convergence in the transport of surface saline water induced by Ekman flow in the vicinity of the formation region, (2) thermal stratification in the preconditioning phase in association with the insolation anomaly induced largely by low-level cloud coverage, and (3) wintertime surface cooling in the eastern subtropics. We find that, in addition to the surface forcing, the properties of both the ESTMW and the upper mixed-layer water are broadly controlled by the volume of the new ESTMW component, and that the variations in the upper mixed-layer water affect the properties of ESTMW formed in the following winter. Due to the combined effect of these processes, the ESTMW subducts down to subsurface layers with a wide range of σ_θ values lying between 24.8 and 25.4 and with significant interannual variation in water mass formation.     

Warming of intermediate layers in the upper Oyashio in 1953–2007

Considerable variations in intermediate water characteristics were found in the upper Oyashio based on the oceanographic data from 1953 to 2007. The long-term temperature trend at the 26.75σ_? isopycnal is 0.03°C/year. This temperature trend is considerably higher than that determined earlier for the Sea of Okhotsk intermediate water and much higher than the World Ocean temperature trend. The westward transport of warm and salty water of the Alaskan Stream is most likely to cause the changes in the Kamchatka Current and upper Oyashio. It is established that Aleutian mesoscale eddies move westward from the location of their formation south of the Blizhniy Strait and transport warm water (3.8–4.2°C) in their core (100–600 m, ～26.75σ_?)). As the trajectory of eddies is quite stable, the westward flow of warm and salty intermediate waters considerably influences the upper Oyashio characteristics.     

Insight into the Role of Lower-Layer Vertical Wind Shear in Tropical Cyclone Intensification over the Western North Pacific

Vertical wind shear fundamentally influences changes in tropical cyclone (TC) intensity. The effects of vertical wind shear on tropical cyclogenesis and evolution in the western North Pacific basin are not well understood. We present a new statistical study of all named TCs in this region during the period 2000-2006 using a second-generation partial least squares (PLS) regression technique. The results show that the lower-layer (between 850 hPa and 10 m above the sea surface) wind shear is more important than the commonly analyzed deep-layer shear (between 200 and 850 hPa) for changes in TC intensity during the TC intensification period. This relationship is particularly strong for westerly low-level shear. Downdrafts induced by the lower-layer shear bring low θ e air into the boundary layer from above, significantly reducing values of θ e in the TC inflow layer and weakening the TC. Large values of deep-layer shear over the ocean to the east of the Philippine Islands inhibit TC formation, while large values of lower-layer shear over the central and western North Pacific inhibit TC intensification. The critical value of deep-layer shear for TC formation is approximately 10 ms-1 , and the critical value of lower-layer shear for TC intensification is approximately ±1.5 ms-1 .     

Evaluation of the boundary layer depth in semi-arid region of India

The annual variation in Planetary Boundary Layer (PBL) height is determined from the profiles of conserved thermodynamic variables, i.e. virtual potential temperature θ_v, equivalent potential temperature θ_e and saturated equivalent potential temperature θ_es, using radiosonde data at Anand (23°35′N, 72°55′E, 45.1 m a.s.l.), India. Out of all the variables, the θ_v profile seems to provide the most reasonable estimate of the PBL height. This has been supplemented by T–Phi gram analysis for specific days. The analysis has been done for 00, 03, 06, 09 and 12 GMT for the 14th and 15th day of each month in the year 1997 based on LASPEX-97 data. In winters the height of boundary layer is very low due to subsidence and radiation cooling while heights in pre-monsoon months exhibit large variations.     

Mesoscale observational analysis of lifting mechanism of a warm-sector convective system producing the maximal daily precipitation in China mainland during pre-summer rainy season of 2015

A long-lived, quasi-stationary mesoscale convective system (MCS) producing extreme rainfall (maximum of 542 mm) over the eastern coastal area of Guangdong Province on 20 May 2015 is analyzed by using high-resolution surface observations, sounding data, and radar measurements. New convective cells are continuously initiated along a mesoscale boundary at the surface, leading to formation and maintenance of the quasi-linear-shaped MCS from about 2000 BT 19 to 1200 BT 20 May. The boundary is originally formed between a cold dome generated by previous convection and southwesterly flow from the ocean carrying higher equivalent potential temperature (θ _e) air. The boundary is subsequently maintained and reinforced by the contrast between the MCS-generated cold outflow and the oceanic higher-θ _e air. The cold outflow is weak (wind speed ≤ 5 m s ^?1), which is attributable to the characteristic environmental conditions, i.e., high humidity in the lower troposphere and weak horizontal winds in the middle and lower troposphere. The low speed of the cold outflow is comparable to that of the near surface southerly flow from the ocean, resulting in very slow southward movement of the boundary. The boundary features temperature contrasts of 2–3°C and is roughly 500-m deep. Despite its shallowness, the boundary appears to exert a profound influence on continuous convection initiation because of the very low level of free convection and small convection inhibition of the near surface oceanic air, building several parallel rainbands (of about 50-km length) that move slowly eastward along the MCS and produce about 80% of the total rainfall. Another MCS moves into the area from the northwest and merges with the local MCS at about 1200 BT. The cold outflow subsequently strengthens and the boundary moves more rapidly toward the southeast, leading to end of the event in 3 h.     

Hydrographic effects of an intense “medicane” over the central-eastern Mediterranean Sea in 2018

The formation of cyclones over the sea surface is driven by air-sea interaction with feedbacks on wave generation, thermohaline structures, and biochemical properties of upper-ocean layers. In the Mediterranean basin, strong cyclonic systems having tropical-like characteristics are called “medicanes”. The consequences of such events are usually assessed over the land, however, hydrographic effects are particularly difficult to be quantified mostly due to the rarity of oceanographic in-situ monitoring systems. In this study, the hydrographic effects of a high-impact medicane, crossing the central-eastern Mediterranean in late September 2018 are investigated mainly based on Argo float measurements. We traced its hydrographic fingerprint and examined its effects on the upper-layer physical properties by analyzing temperature and salinity profiles from floats that overlapped with its track. Float data is supported by satellite sea surface temperature reanalysis data and meteorological records. The synergistic effects of intense evaporation and vertical mixing mechanisms triggered by the medicane, resulted in abrupt surface cooling, especially in the Ionian and Aegean Seas. A relatively homogenous decrease of temperature in the upper 50-m-depth layer followed, along with the deepening of the mixed-layer depth, corresponding to an estimated per profile average deficit of (-2.72 ± 1.23) x 10⁸ J m⁻² in the ocean heat content. Simultaneously, significant upper-layer freshening occurred because of vertical mixing and heavy rainfall. However, a salinity increase in the subsurface waters was observed after the medicane event, which is associated with both horizontal advection and vertical mixing which followed the weakening of the Atlantic Water signal and the dominance of the Levantine Surface Water in this zone. Our findings highlight strong, short-scale hydrographic alterations made available due to the expansion of the marginal seas operational oceanographic network.     

Buoyancy in tropical cyclones and other rapidly rotating atmospheric vortices

Motivated primarily by its application to understanding tropical-cyclone intensification and maintenance, we re-examine the concept of buoyancy in rapidly rotating vortices, distinguishing between the buoyancy of the symmetric balanced vortex or system buoyancy, and the local buoyancy associated with cloud dynamics. The conventional definition of buoyancy is contrasted with a generalized form applicable to a vortex, which has a radial as well as a vertical component. If, for the special case of axisymmetric motions, the balanced density and pressure distribution of a rapidly rotating vortex are used as the reference state, the buoyancy field then characterizes the unbalanced density perturbations, i.e. the local buoyancy. We show how to determine such a reference state without approximation.The generation of the toroidal circulation of a vortex, which is necessary for vortex amplification, is characterized in the vorticity equation by the baroclinicity vector. This vector depends, inter-alia, on the horizontal (or radial) gradient of buoyancy evaluated along isobaric surfaces. We show that for a tropical-cyclone-scale vortex, the buoyancy so calculated is significantly different from that calculated at constant height or on surfaces of constant σ (σ = (p − p^*)/(p_s − p^*), where p is the actual pressure, p^* some reference pressure and p_s is the surface pressure). Since many tropical-cyclone models are formulated using σ-coordinates, we examine the calculation of buoyancy on σ-surfaces and derive an expression for the baroclinicity vector in σ-coordinates. The baroclinic forcing term in the azimuthal vorticity equation for an axisymmetric vortex is shown to be approximately equal to the azimuthal component of the curl of the generalized buoyancy. A scale analysis indicates that the vertical gradient of the radial component of generalized buoyancy makes a comparatively small contribution to the generation of toroidal vorticity in a tropical cyclone, but may be important in tornadoes and possibly also in dust devils.We derive also a form of the Sawyer–Eliassen equation from which the toroidal (or secondary) circulation of a balanced vortex may be determined. The equation is shown to be the time derivative of the toroidal vorticity equation in which the time rate-of-change of the material derivative of potential toroidal vorticity is set to zero. In analogy with the general case, the diabatic forcing term in the Sawyer–Eliassen equation is shown to be approximately equal to the time rate-of-change of the azimuthal component of the curl of generalized buoyancy.Finally, we discuss the generation of buoyancy in tropical cyclones and contrast the definitions of buoyancy that have been used in recent studies of tropical cyclones. We emphasize the non-uniqueness of the buoyancy force, which depends on the choice of a reference density and pressure, and note that different, but equivalent interpretations of the flow dynamics may be expected to arise if different reference quantities are chosen.     

Characteristics of Turbulent Transfer during Episodes of Heavy Haze Pollution in Beijing in Winter 2016/17

We analyzed the structure and evolution of turbulent transfer and the wind profile in the atmospheric boundary layer in relation to aerosol concentrations during an episode of heavy haze pollution from 6 December 2016 to 9 January 2017. The turbulence data were recorded at Peking University’s atmospheric science and environment observation station. The results showed a negative correlation between the wind speed and the PM_2.5 concentration. The turbulence kinetic energy was large and showed obvious diurnal variations during unpolluted (clean) weather, but was small during episodes of heavy haze pollution. Under both clean and heavy haze conditions, the relation between the non-dimensional wind components and the stability parameter z/L followed a 1/3 power law, but the normalized standard deviations of the wind speed were smaller during heavy pollution events than during clean periods under near-neutral conditions. Under unstable conditions, the normalized standard deviation of the potential temperature σ _θ /|θ_*| was related to z/L, roughly following a –1/3 power law, and the ratio during pollution days was greater than that during clean days. The three-dimensional turbulence energy spectra satisfied a –2/3 power exponent rate in the high-frequency band. In the low-frequency band, the wind velocity spectrum curve was related to the stability parameters under clear conditions, but was not related to atmospheric stratification under polluted conditions. In the dissipation stage of the heavy pollution episode, the horizontal wind speed first started to increase at high altitudes and then gradually decreased at lower altitudes. The strong upward motion during this stage was an important dynamic factor in the dissipation of the heavy haze.     

Turbulence characteristics in the atmospheric surface layer during summer monsoon of 1997 over a semi-arid location in India

A land surface processes experiment (LASPEX) was conducted in the semi-arid region of Northwest India during January 1997–February 1998. Analysis of turbulent components of wind and air temperature collected in the surface layer (SL) at Anand (22°35′N, 72°55′E) during the Indian summer monsoon season from June to September 1997 is presented. Turbulent fluctuation of wind components and air temperature observed at Anand varied as a function of terrain features and stability of the surface layer. Under neutral conditions, the standard deviation of vertical velocity (σ _w ) and temperature (σ _T ) were normalized using respective surface layer scaling parameter u _* and T _* which fitted the expressions σ _w /u _* = 1.25 and σ _T /T _* ≈ 4. Micrometeorological spectrum of wind and temperature at 5 m above ground level (AGL) at Anand showed peaks at time scale of 1–3 min at the low-frequency end. The inertial sub-range characteristics (?2/3 slope) of the spectrum are exhibited mostly. However, in some occasions, slope of ?1 denoting brown noise was depicted by the wind and temperature spectrum, which indicated anisotropy in turbulence.     

Dynamical and Thermal Problems in Vortex Development and Movement. Part II: Generalized Slantwise Vorticity Development

The development of vertical vorticity under adiabatic condition is investigated by virtue of the view of potential vorticity and potential temperature (PV-θ) and from a Lagrangian perspective. A new concept of generalized slantwise vorticity development (GSVD) is introduced for adiabatic condition. The GSVD is a coordinate independent framework of vorticity development (VD), which includes slantwise vorticity development (SVD) when a particle is sliding down the concave slope or up the convex slope of a sharply tilting isentropic surface under stable or unstable condition. The SVD is a special VD for studying the severe weather systems with rapid development of vertical vorticity. In addition, the GSVD clarifies VD and SVD. The criteria for VD and SVD demonstrate that the demand for SVD is much more restricted than the demand for VD. When an air parcel is moving down the concave slope or up the convex slope of a sharply tilting isentropic surface in a stable stratified atmosphere with its stability decreasing, or in an unstable atmosphere with its stability increasing, i.e., its stability θ z approaches zero, its vertical vorticity can develop rapidly if its C D is decreasing. The theoretical results are employed to analyze a Tibetan Plateau (TP) vortex (TPV), which appeared over the TP, then slid down and moved eastward in late July 2008, resulting in heavy rainfall in Sichuan Province and along the middle and lower reaches of the Yangtze River. The change of PV 2 contributed to the intensification of the TPV from 0000 to 0600 UTC 22 July 2008 when it slid upward on the upslope of the northeastern edge of the Sichuan basin, since the changes in both horizontal vorticity η s and baroclinity θ s have positive effects on the development of vertical vorticity. At 0600 UTC 22 July 2008, the criterion for SVD at 300 K isentropic surface is satisfied, meaning that SVD occurred and contributed significantly to the development of vertical vorticity. The appearance of the stronger signals concerning the VD and SVD surrounding the vortex indicates that the GSVD concept can serve as a useful tool for diagnosing the development of weather systems.     

Analysis of potential impacts on coastal areas due to changes in wave conditions

This study examines the main physical processes related to coastal and port engineering that could be altered by future changes in wave parameters as a consequence of climate change. To estimate the order of magnitude of the potential changes in these processes, several assumptions and simplifications are made and, in most cases, they are assessed by using simple, empirical state-of-the-art expressions. The studied processes are grouped in three categories according to whether they affect beaches, harbors or coastal structures in general. The changes in these processes are estimated as a function of the deepwater variations of the main wave parameters: wave height (H ₀), wave period (T) and wave direction (θ ₀). A moderate range of variation is assumed for these parameters at deep water (±10 or ±20 % in H ₀ and its square root in T, and ±10º in θ ₀), taking into account recent studies of future wave projections. The results indicate that potential changes in wave height will strongly affect overtopping discharge, stability and scouring of rubble-mound structures and, to a lesser extent, siltation, wave transmission and longshore sediment transport. Changes in wave direction will affect longshore sediment transport in particular and, at a lower magnitude, processes related to port operability (agitation and siltation). Siltation is the only process affected significantly by changes in T alone.     

Formulation of stability-dependent empirical relations for turbulent intensities from surface layer turbulence measurements for dispersion parameterization in a lagrangian particle dispersion model

Season- and stability-dependent turbulence intensity (σ _u /u _*, σ _v /u _*, σ _w /u _*) relationships are derived from experimental turbulence measurements following surface layer scaling and local stability at the tropical coastal site Kalpakkam, India for atmospheric dispersion parameterization. Turbulence wind components (u′, v′, w′) measured with fast response UltraSonic Anemometers during an intense observation campaign for wind field modeling called Round Robin Exercise are used to formulate the flux–profile relationships using surface layer similarity theory and Fast Fourier Transform technique. The new relationships (modified Hanna scheme) are incorporated in a Lagrangian Particle Dispersion model FLEXPART-WRF and tested by conducting simulations for a field tracer dispersion experiment at Kalpakkam. Plume dispersion analysis of a ground level hypothetical release indicated that the new turbulent intensity formulations provide slightly higher diffusivity across the plume relative to the original Hanna scheme. The new formulations for σ _u , σ _v , σ _w are found to give better agreement with observed turbulent intensities during both stable and unstable conditions under various seasonal meteorological conditions. The simulated concentrations using the two methods are compared with those obtained from a classical Gaussian model and the observed SF₆ concentration. It has been found that the new relationships provide comparatively higher diffusion across the plume relative to the model default Hanna scheme and provide downwind concentration results in better agreement with observations.     

Bulk characteristics of heat transfer in the unstable,baroclinic atmospheric boundary layer

Field data for the unstable, baroclinic, atmospheric boundary layer over land and over the sea are considered in the context of a general similarity theory of vertical heat transfer. The dependence of δθ/θ_* upon logarithmic functions of h _c z _T and stability (through the similarity function C) is clearly demonstrated in the data. The combined data support the conventional formulation for the heat transfer coefficient δθ/θ_* when,

1. the surface scaling length is z _T (« z ₀), the height at which the surface temperature over land is obtained by extrapolation of the temperature profile
2. the height scale is taken as the depth of convective mixing h _c
3. the temperature profile equivalent of the von Karman constant is taken as 0.41
4. areal average, rather than single point, values of δθ are employed in strongly baroclinic conditions. No significant effect of baroclinity or the height scale ratio as proposed in the general theory is found. Variations in C about a linear regression relation against stability are most probably due to uncertainties in the areal surface temperature and to experimental errors in general temperature measurements.

     

Estimates of anthropogenic CO<Subscript>2</Subscript> uptake in a global ocean model

A global ocean general circulation model (L30T63) is employed to study the uptake and distribution of anthropogenic CO₂ in the ocean. A subgrid-scale mixing scheme called GM90 is used in the model. There are two main GM90 parameters including isopycnal diffusivity and skew (thickness) diffusivity. Sensitivities of the ocean circulation and the redistribution of dissolved anthropogenic CO₂ to these two parameters are examined. Two runs estimate the global oceanic anthropogenic CO₂ uptake to be 1.64 and 1.73 Pg C yr^-1 for the 1990s, and that the global ocean contained 86.8 and 92.7 Pg C of anthropogenic CO₂ at the end of 1994, respectively. Both the total inventory and uptake from our model are smaller than the data-based estimates. In this presentation, the vertical distributions of anthropogenic CO₂ at three meridional sections are discussed and compared with the available data-based estimates. The inventory in the individual basins is also calculated. Use of large isopycnal diffusivity can generally improve the simulated results, including the exchange flux, the vertical distribution patterns, inventory, storage, etc. In terms of comparison of the vertical distributions and column inventory, we find that the total inventory in the Pacific Ocean obtained from our model is in good agreement with the data-based estimate, but a large difference exists in the Atlantic Ocean, particularly in the South Atlantic. The main reasons are weak vertical mixing and that our model generates small exchange fluxes of anthropogenic CO₂ in the Southern Ocean. Improvement in the simulation of the vertical transport and sea ice in the Southern Ocean is important in future work.     

Simulating the effects of climate changes on Eastern Eurasia forests

The extensive forests of Eastern Eurasia cover an area of ca. 6 million km². The FAREAST model, a forest gap model that simulates the stand composition and dynamics of Eastern Eurasian forests under the current climate, was used to simulate the responses of the Eastern Eurasia Forests to the climate change. Two different scenarios of possible future climatic change were obtained from the IPCC (2001) report (CMIP2 and IS92a-GS) and were used as input to the FAREAST model to determine the compositional and structural sensitivity to climate changes for several locations and along montane elevation gradients. The simulation results suggest that, under the influence of the conditions in the two climate-change scenarios, the underlying forest dynamics should be quite different. Further, Eastern Eurasian forests maintain currents forest structure and biomass only within a small range of climate change. Broad-leaved deciduous trees of such genera as Fraxinus, Quercus and Tilia increase their ranges over Eastern Eurasia under the climate-change scenarios. Conifers, such as Larix and Picea, decrease sharply under climate change and the area of their distributions are reduced. The overall biomass of Pinus is not decreased over the region. While the Pinus distribution range shifts, the area associated with the range of the taxa is not changed.