Validation of MODIS aerosol retrievals and evaluation of potential cloud contamination in East Asia

MODIS aerosol retrievals onboard Terra/Aqua and ground truth data obtained from AERONET(Aerosol Robtic Network) solar direct radiance measurements are collocated to evaluate the quality of the former in East Asia. AERONET stations in East Asia are separated into two groups according to their locations and the preliminary validation results for each station. The validation results showed that the accuracy of MODIS aerosol retrievals in East Asia is a little worse than that obtained in other regions such as Eastern U.S., Western Europe, Brazil and so on. The primary reason is due to the improper aerosol model used in MODIS aerosol retrieval algorithm, so it is of significance to characterize aerosol properties properly according to long term ground-based remote sensing or other relevant in situ observations in order to improve MODIS retrievals in East Asia. Cloud contamination is proved to be one of large errors, which is demonstrated by the significant relation between MODIS aerosol retrievals versus cloud fraction, as well as notable improvement of linear relation between satellite and ground aerosol data after potential cloud contamination screened. Hence, it is suggested that more stringent clear sky condition be set in use of MODIS aerosol data. It should be pointed out that the improvement might be offset by other error sources in some cases because of complex relation between different errors. Large seasonal variation of surface reflection and uncertainties associated with it result in large intercepts and random error in MODIS aerosol retrievals in northern inland of East Asia. It remains to be a big problem to retrieve aerosols accurately in inland characterized by relatively larger surface reflection than the requirement in MODIS aerosol retrieval algorithm.

ENSO and Indian Ocean dipole mode in three coupled GCMs

The simulated ENSO and Indian Ocean dipole (IOD) mode events from three coupled GCMs with the same oceaniccomponent model, CPM0, CPM1 and FGCM0, are compared. The only difference between the CPM0 and theCPM1 comes from the coupling scheme at the airsea interface, e.g., flux anomaly coupling scheme for the former anddirect coupling scheme for the latter. The FGCM0 is also a directly coupled GCM, but its atmospheric componentmodel is the NCAR CCM3 rather than the NCC T63AGCM as in the other two coupled GCMs CPM0 and CPM1.All three coupled models show El Nio-like interannual variability in the tropic Pacific, but the FGCM0 shows a bitstronger amplitude of El Nio events and both the CPM0 and the CPM1 show much weaker amplitude than theobserved one. In the meanwhile, the quasi-biennial variability dominates in the FGCM0 simulations, and 4 a andlonger periods are significant in both the CPM0 and CPM1 models. As the El Nio events simulated by the threecoupled GCMs, the simulated Indian Ocean dipole mode events are stronger from the coupled model FGCM0 andweaker from both the CPM0 and CPM1 models than those from observation.

Comparative study on CO_2 emissions from different types of alpine meadows during grass exuberance period

Potentilla fruticosascrub, Kobresia humilismeadow and Kobresia tibeticameadow are widely distributed on the Qinghai-Tibet Plateau. During the grass exuberance period from 3 July to 4 September, based on close chamber-GC method, a study on CO 2 emissions from different treatments was conducted in these meadows at Haibei research station, CAS. Results indicated that mean CO 2 emission rates from various treatments were 672.09±152.37 mgm -2 h -1 for FC (grass treatment); 425.41±191.99 mgm -2 h -1 for FJ (grass exclusion treatment); 280.36±174.83 mgm -2 h -1 for FL (grass and roots exclusion treatment); 838.95±237.02 mgm -2 h -1 for GG (scrub+grass treatment); 528.48±205.67 mgm -2 h -1 for GC (grass treatment); 268.97±99.72 mgm -2 h -1 for GL (grass and roots exclusion treatment); and 659.20±94.83 mgm -2 h -1 for LC (grass treatment), respectively (FC, FJ, FL, GG, GC, GL, LC were the Chinese abbreviation for various treatments). Furthermore, Kobresia humilismeadow, Potentilla fruticosascrub meadow and Kobresia tibeticameadow differed greatly in average CO 2 emission rate of soil-plant system, in the order of GG>FC>LC>GC. Moreover, in Kobresia humilismeadow, heterotrophic and autotrophic respiration accounted for 42% and 58% of the total respiration of soil-plant system respectively, whereas, in Potentilla fruticosascrub meadow, heterotrophic and autotrophic respiration accounted for 32% and 68% of total system respiration from GG; 49% and 51% from GC. In addition, root respiration from Kobresia humilismeadow approximated 145 mgCO 2 m -2 h -1 , contributed 34% to soil respiration. During the experiment period, Kobresia humilismeadow and Potentilla fruticosascrub meadow had a net carbon fixation of 111.11 gm -2 and 243.89 gm -2 , respectively. Results also showed that soil temperature was the main factor which influenced CO 2 emission from alpine meadow ecosystem, significant correlations were found between soil temperature at 5 cm depth and CO 2 emission from GG, GC, FC and FJ treatments. In addition, soil moisture may be the inhibitory factor of CO 2 emission from Kobresia tibeticameadow, and more detailed analyses should be done in further research.

Effects of adjusting vertical resolution on the eastern equatorial Pacific cold tongue

The vertical resolution of LICOM1.0 (LASG/IAP Climate System Ocean Model, version 1.0) is adjusted by increasing the level amount within the upper 150 m while keeping the total of levels. It is found that the eastern equatorial Pacific cold tongue is sensitive to the adjustment. Compared with the simulation of the original level scheme, the adjusting yields a more realistic structure of cold tongue extending from the coast of Peru to the equator, as well as a temperature minimum at Costa Rica coast, north of the cold tongue. In the original scheme experiment, the sharp heating by net surface heat flux at the beginning of spin-up leads to a great warm- ing in the eastern equatorial Pacific Ocean. The weak vertical advection due to a too thick mixed layer in the coarse vertical structure also accounts for the warm bias. The fact that most significant improvements of the upper 50 m temperature appear at the region of the thinnest mixed layer indicates the necessity of fine vertical resolution for the eastern equatorial Pacific Ocean. However, the westward extension of equatorial cold tongue, a defect in the original scheme, gets even more serious in the adjusting scheme due to the intensi- fied vertical velocity and hence vertical advection in the central-eastern equatorial Pacific Ocean.

Mesoscale eddies in the South China Sea and their impact on temperature profiles

Some life history statistics of the mesoscale eddies of the South China Sea (SCS) derived from altimetry data will be further discussed according their different formation periods. A total of three ATLAS (autonomous temperature line acquisition system)mooring buoys data will be analyzed to discuss eddies' impact on temperature profiles.They identify that the intraseasonal variation of SCS thermocline is partly controlled by mesoscale eddies.

A field experimental study of lignin sand stabilizing material(LSSM) extracted from spent-liquor of straw pulping paper mills

A new technique was introduced for sand stabilization and re-vegetation by use of lignin sand stabilizing material(LSSM). LSSM is a reconstructed organic compound with lignin as the most dominant component from the extracts of black-liquor issued by straw pulp paper mills. Unlike the polyvinyl acetate or foamed asphalt commonly used for dune stabilization, the new material is plant-friendly and can be used with virescence actions simultaneously. The field experimental study was conducted since 2001 in China's Northwest Ningxia Hui Autonomous Region and has been proved that LSSM is effective in stabilizing the fugitive dunes, making the arenaceous plants survive and the bare dune vegetative. The advisable solution concentration is 2% and the optimal field spraying quantity is 2 5 L/m^2 The soil nutrients of the stabilized and greened dune, such as organic matter, available phosphorous and total nitrogen are all increased compared with the control treatment, which is certainly helpful to the growth of arenaceous plants. The technique is worthwhile to be popularized because it is provided not only a new method for desertification control but also an outlet for cleaning contaminants issued from the straw paper mills.

Interannual variability of mixed layer depth and heat storage of upper layer in the tropical Pacific Ocean

By using the upper layer data(downloaded from the web of the Scripps Institution of Oceanography),the interannual variability of the heat storage of upper layer(from surface to 400 m depth) and the mixed layer depth in the tropical Pacific Ocean are investigated. The abnormal signal of the warm event comes from the central and west Pacific Ocean, whereas it is regarded that the abnormal signal of the warm event comes from the east Pacific Ocean in the popular viewpoint. From the viewpoint on the evolution of the interannual variability of the mixed layer depth and the heat storage of the whole upper layer, the difference between the two types of El Nino is so small that it can be neglected. During these two El Nino/La Nina events(1972/1973 and 1997/1998), other than the case of the heat storage or for the mixed layer depth, the abnormal signal propagates from the central and west Pacific Ocean to the east usually by the path along the equator whereas the abnormal signal propagates from the east to the west by the path northern to the equator. For the interannual variability, the evolution of the mixed layer depth corresponds to that of the heat storage in the upper layer very well. This is quite different from the evolution of seasonality.

CARBON DYNAMICS OF WETLAND IN THE SANJIANG PLAIN

Methane (CH4) and carbon dioxide (CO2) emission was measured from mires in the Sanjiang Plain, Northeast China, by using a static chamber technique during free snow-covered periods. The seasonal mean emission of CH4 was 12.4mg/(m2·h) and the emission range of CO2 was 8.7-16.6g/(m2·d) (gross CO2 flux) during plant growth period. CO2 emission rate in the day was stronger than that at night, and the daily peak appears at 19:00. The mire plants in the Sanjiang Plain begin to sprout at the end of April. The aboveground biomass of the mire plants increased from zero to the peak from July to September and showed single peak form. The aboveground biomass of Carex lasiocarpa (464.8g/m2) was lower than that of Deyeuxia platyphylla (530.8g/m2), but the underground biomass was higher than that of Deyeuxia platyphylla. Gross CO2 flux showed the significance positive correlation relationship with plant biomass. Gross CO2 flux and CH4 emission were also correlated with soil temperature (0-5cm) and water temperature. However, the highest CH4 emission rate lagged behind the highest soil temperature in the root area during plant growth period. The data also indicated that wet and warm conditions during the early spring led to greater value of CH4 emission flux. Inundation is the necessary condition for the existence of methane bacteria, but there is no significant positive correlation between the inundation depth and CH4 emission rate in this region. Within the same growing season and under the same inundation condition, the variations of CH4 emission rate could be markedly different.

Parameterization of the Absorption of the H_(2)O Continuum,CO_(2),O_(2),and Other Trace Gases in the Fu-Liou Solar Radiation Program

The absorption properties of the water vapor continuum and a number of weak bands for H2O, O2, CO2, CO, N2O, CH4, and O3 in the solar spectrum are incorporated into the Fu-Liou radiation parameterization program by using the correlated k-distribution method (CKD) for the sorting of absorption lines. The overlap absorption of the H2O lines and the H2O continuum (2500-14500 cm-1) are treated by taking the two gases as a single-mixture gas in transmittance calculations. Furthermore, in order to optimize the computation efforts, CO2 and CH4 in the spectral region 2850-5250 cm-1 are taken as a new single-mixture gas as well. For overlap involving other absorption lines in the Fu-Liou spectral bands, the authors adopt the multiplication rule for transmittance computations under which the absorption spectra for two gases are assumed to be uncorrelated. Compared to the line-by-line (LBL) computation, it is shown that the errors in fluxes introduced by these two approaches within the context of the CKD method are small and less than 0.48% for the H2O line and continuum in the 2500-14500 cm-1 solar spectral region, -1% for H2O (line)+H2O (continuum)+CO2+CH4 in the spectral region 2850-5250 cm-1, and -1.5% for H2O (line)+H2O (continuum)+O2 in the 7700-14500 cm-1 spectral region. Analysis also demonstrates that the multiplication rule over a spectral interval as wide as 6800 cm-1 can produce acceptable errors with a maximum percentage value of about 2% in reference to the LBL calculation. Addition of the preceding gases increases the absorption of solar radiation under all sky conditions. For clear sky, the increase in instantaneous solar absorption is about 9%-13% (~12 W m^2) among which the H2O continuum produces the largest increase, while the contributions from O2 and CO2 rank second and third, respectively. In cloudy sky, the addition of absorption amounts to about 6-9 W m-2. The new, improved program with the incorporation of the preceding gases produces a smaller solar absorption in clouds due to the reduced solar flux reaching the cloud top.

Determination of the Current System on Isopycnal Surface Between Mindanao and New Guinea from GDEM

In this study, we used the Navy’s Generalized Digital Environmental Model (GDEM) climatological temperature and salinity data on a 0.5°×0.5° grid to investigate the seasonal variabilities of the southwest Philippines Sea (0.5°–9°N, 123.5°–136.5°) thermohaline structure and circulation. The GDEM for the area was built up on historical (1930–1997) temperature and salinity profiles. A three-dimensional estimate of the absolute geostrophic velocity field on isopycnal surface was obtained from the GDEM temperature and salinity fields using the P-vector method. The seasonal variabilities of the thermohaline structure and currents (obtained from the inverse method) such as the Mindanao Current, Mindanao Undercurrent, North Equatorial Counter Current, New Guinea Coastal Undercurrent, and dual-eddies (cyclinic Mindanao Eddy and anticyclonic Halmahera Eddy) are identified.

Simulation and Prediction of Soil Organic Carbon Dynamics in Jiangsu Province Based on Model and GIS Techniques

Based on the databases of soils, meteorology, crop production, and agricultural management, changes in the soil organic carbon (SOC) of agro ecosystems in Jiangsu Province were simulated by using a soil organic carbon model with a linkage of GIS. Four data sets of soil organic carbon measured from various field experiments in Jiangsu Province were used to validate the model. It was demonstrated that the model simulation in general agreed with the field measurements. Model simulation indicated that the SOC content in approximately 77% of the agricultural soils in Jiangsu Province has increased since the Second National Soil Survey completed in the early 1980s. Compared with the values in 1985, the SOC content in 2000 was estimated to increase by 1.03.0 g kg 1 for the north and the coastal areas of the province, and by 3.55.0 g kg 1 for the region of Tai Lake in the south. A slight decrease (about 0.51.5 g kg 1 ) was estimated for the central region of Jiangsu Province and the Nanjing Zhenjiang hilly area. Model prediction for 2010 A.D. under two scena rios, i.e., with 30 and 50% of the harvested crop straw incorporation, suggested that the SOC in Jiangsu Province would increase, and thus that the agricultural soils would have potential as organic carbon storage. The incorporation of crop straw into soils is of great benefit to increase soil carbon storage, consequently to benefit the control of the rise of atmospheric CO 2 concentration and to maintain the sustainable development of agriculture.

Effects of Water Regime and Straw Application in Paddy Rice Season on N2O Emission from Following Wheat Growing Season

A split-plot experiment in a rice-winter wheat rotation system was performed to study the effects of water regime and wheat straw application in rice-growing season on N2O emission from following wheat growing season. Water regime in the rice-growing season was designed as the conventional irrigation (flooding/drainage cycle) and the permanent flooding. Wheat straw was incorporated with three rates of 0, 225 and 450 g m-2 into the paddy soil for each water regime just before rice was transplanted. N2O emission was measured by static chamber-gas chromatograph method. Results from the variance analysis indicated that the permanent flooding in rice-growing season markedly enhanced N2O emission in following wheat growing season (P=0. 003), and that the effect of straw application on N2O emission was distinguished between two water regimes. Under the conventional irrigation, incoporation of wheat straw reduced N2O emission in the following wheat growing season, while there were no significant differences in the emission for the straw application rates of 225 and 450 g m-2. No significant differences in N2O emissions were observed among the three rates of straw application for the permanent flooding regime. In addition, the seasonal variation of N2O emission was regulated by soil temperature and moisture. The daily N2O flux (Y, mg m-2 d-1) can be quantitatively described by soil temperature (T, ℃) and moisture (W, WFPS %) asY=A0+A1T+A2W+A3W2(n=23, R2 ≥0. 4159** )or y=C0+C1W+C2W2(n=23,R2≥0. 4074** ). Compared with the effect of soil temperature on N2O emission, soil moisture was an important factor regulating the seasonal pattern of N2O emission.

Role of Anthropogenic Volatile Organic Compounds and Nitrogen Oxides as Ozone Precursors in the Wintertime over East Asia

As an exercise in model sensitivity, the Models-3 Community Multiscale Air Quality (CMAQ) modeling system with meteorological fields from the Regional Atmospheric Modeling System (RAMS) was applied to study the response of photochemical oxidants to systematic increases in anthropogenic volatile organic compounds (VOC) and nitrogen oxides (NO x) emissions in January 1997 over East Asia. Three simulations-one base case and two sensitivity simulations were carried out. Two sensitivity simulations were performed by assuming a 35% separate increase in anthropogenic VOC and NO x emissions comparing with the base case. Biogenic VOC emissions were held constant across the sensitivity simulations. To evaluate the model performance, ozone mixing ratios (O 3) from the base case simulation were compared with surface observations at five remote sites in Japan, and it was found that the model reproduces most of the important features in the observations. Monthly average O 3 concentrations in the daytime were examined to gain an understanding of how the increase in anthropogenic emissions affected the overall chemical system for each sensitivity simulation.

Automatic and continuous measurement of aerosol properties in Dunhuang,China

Ground-based simultaneous observations of sun direct and scattering radiation were carried out in Dunhuang for nearly 2 years. Aerosol optical depth, Angstrom wavelength exponent and size distribution were obtained from solar extinction and sky radiation. Water vapor content was obtained from sun direct radiation measurement at 940 nm. Relationship between aerosol properties and water vapor was discussed. Results showed that distinct seasonality of aerosol optical depth and Angstrom wavelength exponent was corresponding to seasonal variation of dust activity. Aerosol relative size distribution kept stable and volume concentration change was the reason resulting in variation of aerosol optical depth. Water vapor had minor effects on aerosol optical and physical properties.

RELATIONSHIP BETWEEN DIPOLE OSCILLATION OF SSTA OF INDIAN OCEAN REGION AND PRECIPITATION AND TEMPERATURE IN CHINA

The work is a general survey using SSTA data of the Indian Ocean and of precipitation at 160Chinese weather stations over 1951～1997 (47 years). It reveals that the dipole oscillation of SST, especially the dipole index of March～May, in the eastern and western parts of the ocean correlates well with the precipitation during the June～August raining season in China. As shown in analysis of 500-hPa Northern Hemisphere geopotential height height by NCEP for 1958～1995, the Indian Ocean dipole index (IODI) is closely related with geopotential height anomalies in the middle- and higher- latitudes in the Eurasian region. As a negative phase year of IODI corresponds to significant Pacific-Japan (P J) wavetrain, it is highly likely that the SST for the dipole may affect the precipitation in China through the wavetrain. Additionally, correlation analysis of links between SST dipole index of the Indian Ocean region and air temperature in China also shows good correlation between the former and wintertime temperature in southern China.

The influence of 30~60 d oscillation on the development of the South China Sea summer monsoon

Using the National Center for Enviromental Prediction/National Center for Atmospheric Research (NCEP/NCAR)reanalysis data and NOAA satellite-observed outgoing long-wave radiation (OLR) data, the development of theSouth China Sea (SCS) summer monsoon and intraseasonal (30~60 d) oscillation (ISO) have been examined. Theresults show that there exists obvious interannual variability of intraseasonal oscillaiton. Using the 16 a time series offiltered OLR averaged over the SCS, an index is defined to define onset events over the SCS on the ISO time scales.Of the 16 a examined here, 10 shows a strong ISO signal in the onset of monsoon convection over the SCS. In thesecases, the ISO initially suppresses the seasonal development of southwesterly and cyclonic circulation over the SCSbefore the ISO onset. As the ISO propagates northeastward, the low frequency cyclonic circulation anomaly occursin the SCS and the low frequency southwesterly wind and convection over here dramatically intensify. The northeastprogression of the ISO anomaleis plays a role in the initial suppression and then acceleration of the seasonal cycle ofthe SCS summer monsoon.

Nonlinear Oscillations of Semigeostrophic Eady Waves in the Presence of Diffusivity

Analyses are performed to examine the physical processes involved innonlinear oscillations of Eady baroclinic waves obtained from viscous semigeostrophic models withtwo types of boundary conditions (free-slip and non-slip). By comparing with previous studies forthe case of the free-slip boundary condition, it is shown that the nonlinear oscillations areproduced mainly by the interaction between the baroclinic wave and zonal-mean state (totalzonal-mean flow velocity and buoyancy stratification) but the timescale of the nonlinearoscillations is largely controlled by the diffusivity. When the boundary condition is non-slip, thenonlinear oscillations are further damped and slowed by the diffusive process. Since the free-slip(non-slip) boundary condition is the zero drag (infinite drag) limit of the more realistic dragboundary condition, the nonlinear oscillations obtained with the two types of boundary conditionsare two extremes for more realistic nonlinear oscillations.

SINGULAR PERTURBATION FOR REACTION DIFFUSION EQUATIONS

The singularly perturbed initial boundary value problems for reaction diffusion equations are considered.Under suitable conditions and by using the theory of differential inequality,the asymptotic behavior of solution for initial boundary value problems are studied,where the reduced problems possess two intersecting solutions.

A preliminary study of 3D difference scheme with energy dynamic equilibrium

In this paper, a difference scheme with energy dynamic equilibrium (DS-EDE) is presented, which can be used for the simulation of long-term atmosphere and sea motion. Based on three dimensional nonlinear evolution equations for atmosphere and sea motion, a three dimensional compact upwind scheme (CUWS) is constructed, as the basis of the DS-EDE. The DS-EDE satisfies the following condition of energy dynamic equilibrium (EDE): the total work of external forces on the region boundary is equal to the sum of the total effective variation of the kinetic energy and the energy dissipation in the average flow motion and the effective variation of the potential energy per unit time within the region of interest. It really reflects the basic mechanism of the action of external forces and dissipation in atmosphere and sea movement. Therefore, the DS-EDE developed in this paper is a suitable model for simulating long-term atmosphere and sea movement with forcing and dissipation.