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1.
A coupled aerosol–cloud model is essential for investigating the formation of haze and fog and the interaction of aerosols with clouds and precipitation. One of the key tasks of such a model is to produce correct mass and number size distributions of aerosols. In this paper, a parameterization scheme for aerosol size distribution in initial emission, which took into account the measured mass and number size distributions of aerosols, was developed in the GRAPES–CUACE [Global/Regional Assimilation and PrEdiction System–China Meteorological Administration (CMA) Unified Atmospheric Chemistry Environment model]—an online chemical weather forecast system that contains microphysical processes and emission, transport, and chemical conversion of sectional multi-component aerosols. In addition, the competitive mechanism between nucleation and condensation for secondary aerosol formation was improved, and the dry deposition was also modified to be in consistent with the real depositing length.Based on the above improvements, the GRAPES–CUACE simulations were verified against observational data during 1–31 January 2013, when a series of heavy regional haze–fog events occurred in eastern China. The results show that the aerosol number size distribution from the improved experiment was much closer to the observation, whereas in the old experiment the number concentration was higher in the nucleation mode and lower in the accumulation mode. Meanwhile, the errors in aerosol number size distribution as diagnosed by its sectional mass size distribution were also reduced. Moreover, simulations of organic carbon, sulfate, and other aerosol components were improved and the overestimation as well as underestimation of PM2.5 concentration in eastern China was significantly reduced, leading to increased correlation coefficient between simulated and observed PM2.5 by more than 70%. In the remote areas where bad simulation results were produced previously, the correlation coefficient grew from 0.35 to 0.61, and the mean mass concentration went up from 43% to 87.5% of the observed value. Thus, the simulation of particulate matters in these areas has been improved considerably.  相似文献   

2.
A coupled aerosol–cloud model is essential for investigating the formation of haze and fog and the interaction of aerosols with clouds and precipitation. One of the key tasks of such a model is to produce correct mass and number size distributions of aerosols. In this paper, a parameterization scheme for aerosol size distribution in initial emission,which took into account the measured mass and number size distributions of aerosols, was developed in the GRAPES–CUACE [Global/Regional Assimilation and Pr Ediction System–China Meteorological Administration(CMA) Unified Atmospheric Chemistry Environment model]—an online chemical weather forecast system that contains microphysical processes and emission, transport, and chemical conversion of sectional multi-component aerosols. In addition, the competitive mechanism between nucleation and condensation for secondary aerosol formation was improved, and the dry deposition was also modified to be in consistent with the real depositing length. Based on the above improvements, the GRAPES–CUACE simulations were verified against observational data during 1–31 January 2013, when a series of heavy regional haze–fog events occurred in eastern China. The results show that the aerosol number size distribution from the improved experiment was much closer to the observation, whereas in the old experiment the number concentration was higher in the nucleation mode and lower in the accumulation mode. Meanwhile, the errors in aerosol number size distribution as diagnosed by its sectional mass size distribution were also reduced. Moreover, simulations of organic carbon, sulfate, and other aerosol components were improved and the overestimation as well as underestimation of PM2.5 concentration in eastern China was significantly reduced,leading to increased correlation coefficient between simulated and observed PM2.5 by more than 70%. In the remote areas where bad simulation results were produced previously, the correlation coefficient grew from 0.35 to 0.61, and the mean mass concentration went up from 43% to 87.5% of the observed value. Thus, the simulation of particulate matters in these areas has been improved considerably.  相似文献   

3.
Li Jun 《大气科学进展》1994,11(4):421-426
Linearization of Radiative Transfer Equation (RTE) is the key step in physical retrieval of atmospheric temperature and moisture profiles from InfRared (IR) sounder observations. In this paper, the successive forms of temperature and water vapor mixing ratio component weighting functions are derived by applying one term variation method to RTE with surface emissivity and solar reflectivity contained. Retrivals of temperature and water vapor mixing ratio profiles from simulated Atmospheric Infrared Sounder (AIRS) observations with surface emissivity and solar reflectivity are presented.  相似文献   

4.
Bolivia is located at the crossroad of the major climatic influences of Northern and Southern-South America, which turns this country into a natural laboratory to investigate the interactions between ocean-climate and fire variability. We chose two oceanic indices: MEI (multivariate ENSO Index) and AMO (Atlantic Multidecadal Oscillation) to select the three most representative years for four oceanic conditions: El Niño, La Niña, AMO, and standard years (understood as years with little ocean influences), for the period 1992–2012. We investigated how i) rainfall (dry vs wet seasons) and ii) fire responded in five Bolivian biomes (Tropical Moist Forests, Tropical Dry Forests, Tropical Grasslands, Tropical Montane, and Seasonally Flooded ecosystems) under these oceanic conditions. Bolivia showed a strong rainfall increase in El Niño years in both seasons (wet/dry), while AMO showed the strongest droughts in both seasons. La Niña showed a bipolar response with rainfall increases in the wet season and a very marked rainfall decrease in the dry season. Drought significantly increased fire numbers in AMO years, being the most significant fire condition and suggesting a larger fire influence of the Atlantic than the Pacific at the national level. Surprisingly, the amount of fire was very large under normal years (STD) and similar to fire levels under La Niña, suggesting generalized fire conditions in the country, except for El Niño years that bring rainfall excess and little fire. The most fire-affected biomes were the seasonally flooded and dry forests, followed by the grassland/savannah biome. Montane areas showed the least fire, but satellite fire omission is well known in the Andean region.  相似文献   

5.
In this study,the classification scheme developed by Jenkinson and Collison (1977) based on a typing scheme of Lamb (1950) is applied to obtain circulation types from the mean sea-level pressure on a monthly basis.Monthly mean sea-level pressure data from 1951 to 2002 are used to derive six circulation indices and to provide a circulation catalogue with 27 circulation types.Five major types (N,NW,C,CSW,and SW) which occurred most frequently are analyzed to reveal their relationships with the temperature of Harbin on various time scales.Stepwise multiple regression is used to reconstruct temperature anomaly.The monthly mean rainfall of all types occurring and the composite maps of three major types (C,CSW,and SW) relevant to Harbin's precipitation are studied. The results show that the dominant types in winter are types N and NW.types C,CSW,and SW occur frequently in summer.Types N and NW favor a negative temperature anomaly and correspond to less rainfall,while types C,CSW,and SW often induce a positive temperature anomaly and correspond to more rainfall.Moreover,a successful statistical model can be established with only one of the six indices and large-scale mean temperature.Using the model,77.3% of the total variance in the temperature anomaly between 1951 and 2002 can be reconstructed.Type C has a close relationship with total rainfall and type C precipitation plays a major role in determining the total rainfall of Harbin in recent years.This classification scheme is a statistical downscaling model and its relationships with temperature and precipitation can be used to forecast regional climate.  相似文献   

6.
Summary  Anomalously wet and dry months in the Mediterranean basin were identified during the period 1860–1990 from observations at five stations located along the west-east axis of the Mediterranean basin (Barcelona, Florence, Malta, Athens and Jerusalem), supplemented by data from Madrid and Lisbon. Wet and dry months were characterized by hydric indices (HI) based on values of the standardized precipitation anomalies. Different patterns of anomalously wet and dry months were qualitatively identified on the basis of the spatial distributions of the hydric indices. The standardized sea level pressure values at 56 grid points in the domain 35° N–65° N, 30° W–40° E, for each of the anomalously wet and dry months, were subjected to T-mode Principal Component Analysis. The mean hydric indices associated with each principal component in each season are arranged in four distinct different spatial distributions for wet months and in three for dry months as following: (a) Mediterranean wide distribution of positive/negative anomalies; (b1) Strong positive anomalies to the west, but weaker to eastern Mediterranean; (b2) Strong negative anomalies to the west, but weaker or normal to the east; (c1) Strong positive anomalies to the west and to the east and weaker ones to the central Mediterranean; (c2) Negative anomalies to the west and east, but weaker, or normal, or positive to the central Mediterranean; (d) Relatively strong positive anomalies to the east and weaker ones to the western Mediterranean. Finally, monthly mean charts of standardized anomaly and mean sea level pressure are presented for each principalcomponent in each season. These charts are used to interpret the spatial distribution of the positive and negative precipitation anomalies in terms of mean circulation over the domain. Received December 10, 1998 Revised June 14, 1999  相似文献   

7.
Zonal circulation indices with monthly and seasonal resolutions are calculated based on gridded monthly mean sea-level pressure (SLP) reconstructed back to 1780 by Jones et al. (1999): an overall zonal index for the whole European area between 30°W and 40°E, a normalized index for the North Atlantic Oscillation (NAO), and a similar index for Central Europe. For most of the early time up to the mid-nineteenth century we get preferred negative anomalies in the NAO index for winter and preferred positive ones for summer. The turning points in cumulative anomalies - during the 1850s for winter and during the 1870s for summer - indicate a transition period in circulation modes from the "Little Ice Age" to the recent climate in Europe. Running correlations (time windows of 21 years with time steps of one year) between zonal indices and regional temperature time series from Central England, Stockholm and two Central European regions are all indicating major instationarities in these relationships with a particular decline in winter correlations around the turn from the nineteenth to the twentieth centuries. Aspects of different circulation patterns linked with these variabilities are discussed.  相似文献   

8.
1. Introduction The quasi-biennial oscillation (QBO) of the mean zonal wind in the equatorial stratosphere was discov- ered by Reed et al. (1961) and Veryard and Ebdon (1961). Later, Funk and Garnham (1962) and Ra- manathan (1963) were the first to descri…  相似文献   

9.
Gas and particulate reaction products from the ozonolysis of -caryophyllene (I) in the presence of atmospheric air were investigated using a combination of gas chromatography-mass spectrometry (GC-MS) and high performance liquid chromatography (HPLC). A Scanning Mobility Particle Sizer system (3936, TSI) and a Condensation Particle Counter (3025A, TSI) were used to study secondary organic aerosol formation. The nighttime oxidation was carried out in a large outdoor smog chamber (190 m3). A wide range of ring retaining and ring opening products in the gas and particle phase are reported over the course of the reaction. On average, measured gas and particle phase products accounted for 64% of the reacted -caryophyllene (I) carbon. Measurements show that a number of reaction products with low vapor pressure (e.g., -caryophyllone aldehyde (IV), -norcaryophyllone aldehyde (V), -caryophyllonic acid (VIII), -14-hydroxycaryophyllonic acid (XIV)) were found in the sample taken during the first 20 min of the reaction and may play an important role in the early formation of secondary organic aerosol. A detailed mechanism is proposed to account for most products observed in this investigation.  相似文献   

10.
We analyze the dynamics of global fossil resource markets under different assumptions for the supply of fossil fuel resources, development pathways for energy demand, and climate policy settings. Resource markets, in particular the oil market, are characterized by a large discrepancy between costs of resource extraction and commodity prices on international markets. We explain this observation in terms of (a) the intertemporal scarcity rent, (b) regional price differentials arising from trade and transport costs, (c) heterogeneity and inertia in the extraction sector. These effects are captured by the REMIND model. We use the model to explore economic effects of changes in coal, oil and gas markets induced by climate-change mitigation policies. A large share of fossil fuel reserves and resources will be used in the absence of climate policy leading to atmospheric GHG concentrations well beyond a level of 550 ppm CO2-eq. This result holds independently of different assumptions about energy demand and fossil fuel availability. Achieving ambitious climate targets will drastically reduce fossil fuel consumption, in particular the consumption of coal. Conventional oil and gas as well as non-conventional oil reserves are still exhausted. We find the net present value of fossil fuel rent until 2100 at 30tril.US$ with a large share of oil and a small share of coal. This is reduced by 9 and 12tril.US$ to achieve climate stabilization at 550 and 450 ppm CO2-eq, respectively. This loss is, however, overcompensated by revenues from carbon pricing that are 21 and 32tril.US$, respectively. The overcompensation also holds under variations of energy demand and fossil fuel supply.  相似文献   

11.
Gas phase ozonolysis of -pinene was performedin a 570 l static reactor at 730 Torr and 296 K insynthetic air and the products were analysed by acombination of gas phase FTIR spectroscopy, HPLC andIC analyses of gas phase and aerosol samples,respectively. The reaction mechanism was investigatedby adding HCHO, HCOOH and H2O as Criegeeintermediate scavenger and cyclohexane as OH radicalscavenger. Main identified products (yields inparentheses) in the presence of cyclohexane as OHradical scavenger were HCHO (0.65 ± 0.04),nopinone (0.16 ± 0.04), 3-hydroxy-nopinone (0.15± 0.05), CO2 (0.20 ± 0.04), CO (0.030± 0.002), HCOOH (0.020 ± 0.002), the secondaryozonide of -pinene (0.16 ± 0.05), andcis-pinic acid (0.02 ± 0.01). The decompositionof the primary ozonide was found to yieldpredominantly the excited C9-Criegee intermediateand HCHO (0.84 ± 0.04) and to a minor extent theexcited CH2OO intermediate and nopinone (0.16± 0.04). Roughly 40% of the excitedC9-Criegee intermediate becomes stabilised andcould be shown to react with HCHO, HCOOH and H2O. The atmospherically important reaction of thestabilised C9-Criegee intermediate with H2Owas found to result in a nopinone increase of (0.35± 0.05) and in the formation of H2O2(0.24 ± 0.03). Based on the observed products,the unimolecular decomposition/isomerisationchannels of the C9-Criegee intermediate arediscussed in terms of the hydroperoxide and esterchannels. Subsequent reactions of the nopinonylradical, formed in the hydroperoxide channel, lead tomajor products like 3-hydroxy-nopinone but also tominor products like cis-pinic acid. A mechanismfor the formation of this dicarboxylic acid isproposed and its possible role in aerosol formationprocesses discussed.  相似文献   

12.
Abstract

Teleconnections between sea surface temperature (SST) anomalies over the Pacific and the dominant patterns of wintertime Northern Hemisphere 500‐hPa height are examined by applying statistical techniques such as rotated principal component analysis and composite analysis. It is shown that the Pacific/North American (PNA) patterns in December through March are correlated most significantly with the ENSO‐related SST anomalies in the previous October, while the western Pacific (WP) patterns in December through February are most closely linked to the ENSO‐related SST anomalies in the same season. In addition, the PNA response to the ENSO signal during La Niña events is more significant than that during El Niño events, while the WP response is stronger during El Niño events than during La Niña events. A composite analysis shows that in the El Niño winters the North Pacific centre of the PNA pattern is located about 10 degrees east of its normal position, leading to a less significant correlation between the ENSO signal and the PNA pattern in these winters.

The ENSO‐related SST anomalies include a large centre of action over the tropical Pacific and an oppositely signed anomaly centre over the North Pacific. The North Pacific centre appears to the west of the dateline in September and October. This ENSO‐related seed of SST anomalies slowly moves eastward in the following months, gradually cutting off its connection with SST anomalies over the tropical Pacific and being coupled with the PNA pattern. It is pointed out that, although the wintertime SST anomaly over the North Pacific may appear as a mode linearly independent of the ENSO signal in the same season, it is partially related to the ENSO signal in the preceding autumn.

Possible dynamical explanations of the above results are discussed. It is suggested that the WP pattern can be linked to the tropical Pacific heat source via advection of vorticity by the upper‐tropospheric divergent/convergent flow, and the intensification of vorticity gradients associated with a stronger east Asian jet is likely to be responsible for a more significant WP pattern response to the ENSO signal in the El Niño winters. On the other hand, the ENSO‐related PNA pattern could be considered a manifestation of the eastward extension (El Niño) or westward withdrawal (La Niña) of the east Asian jet stream due to the local Hadley cell over the Pacific. In addition, the ENSO‐related seed of extratropical SST anomaly over the western Pacific in autumn may also play an important role in the development of the PNA pattern in the following winter.  相似文献   

13.
A two-dimensional, multitvariate objective analysis scheme for simultaneous analysis of geopotential height and wind fields has been developed over Indian and adjoining region for use in numerical weather prediction. The height-height correlations calculated using daily data of four July months (1976-1979), are used to derive the other autocorrelations and cross-correlations assuming geostropic relationship. A Gaussian function is used to model the autocorrelation function. Since the scheme is multivariate the regression coefficients (weights) are matrix.Near the equator, the geostrophic approximation relating mass and wind is decoupled in a way similar to Bergman (1979). The objective analyses were made over Indian and adjoining region for 850, 700, 500, 300 and 200 hPa levels for the period from 4 July to 8 July 1979, 12 GMT. The analyses obtained using multivariate optimum interpolation scheme depict the synoptic situations satisfactorily. The analyses were also compared with the FGGE analyses (from  相似文献   

14.
In this study, we investigated the features of Arctic Oscillation （AO） and Antarctic Oscillation （AAO）, that is, the annular modes in the extratropics, in the internal atmospheric variability attained through an ensemble of integrations by an atmospheric general circulation model （AGCM） forced with the global observed SSTs. We focused on the interannual variability of AO/AAO, which is dominated by internal atmospheric variability. In comparison with previous observed results, the AO/AAO in internal atmospheric variability bear some similar characteristics, but exhibit a much clearer spatial structure： significant correlation between the North Pacific and North Atlantic centers of action, much stronger and more significant associated precipitation anomalies, and the meridional displacement of upper-tropospheric westerly jet streams in the Northern/Southern Hemisphere. In addition, we examined the relationship between the North Atlantic Oscillation （NAO）/AO and East Asian winter monsoon （EAWM）. It has been shown that in the internal atmospheric variability, the EAWM variation is significantly related to the NAO through upper-tropospheric atmospheric teleconnection patterns.  相似文献   

15.
Previous studies showed that 4 D-Var technique used for data assimilation could be modified for weather control. This study demonstrates the ability of 4 D-Var to influence the future path of a tropical cyclone by calculating perturbations in WRF simulation. Given the background error covariance matrix, the initial field is improved by the vortex dynamic initialization technique. Our results show that 4 D-Var can be applied to control the trajectory of simulated tropical cyclones by producing "optimal" perturbations. In the numerical simulation experiment of Typhoon Mitag in 2019, after this kind of weather control similar to data assimilation, the tropical cyclone moved obviously,and the damaging wind over the coastline weakened. The prediction results after the initial field modified by 4 D-Var have a great change, and the position of the tropical cyclone moved about 0.5° southeastward after assimilation,which misses the southeast coast of China. Moreover, the damaging wind is also weakened. Since the 4 D-Var is premised on the assumption that the model is perfect and does not consider the model error, then the research plan to consider model error and introduce new methods is discussed in the paper.  相似文献   

16.
We investigate the role of culture in sustaining essential ecosystem services in the arid and erratic climate of an agropastoral landscape in southern Madagascar. Our fieldwork and interviews in Ambovombe subprefecture in Androy addressed land use, agropastoralism, livelihood, institutions and their moral basis. Our analysis points to the interdependence of cultural practices and ecosystem services: sacred forests, crop pollination, subsistence farming, cattle economy and societal transition and purification rituals. We posit a social-ancestral contract that works as a moral attractor structuring and sustaining the agropastoral ecosystem services system. The contract between living and nonliving clan members underpins the cultural practices and rituals that regulate the vulnerable agropastoral system. We conclude that the well-being values of the inhabitants of the south of Madagascar depend upon moralities that lend legitimacy and stability to the management of the social–ecological processes that precondition ecosystem services production. Neither ecosystem nor culture delivers ecosystem services to society. Ecosystem services are generated by an interdependent social–ecological system in which knowledge, practice, and beliefs coevolve: culture is a key factor in their generation and persistence. The study suggests these are significant interdependences to consider in dynamic analyses of ecosystem service production.  相似文献   

17.
Increasing heavy concentrated Meiyu precipitation over the Yangtze–Huaihe river valley (YHRV) during recent years has been previously reported. In fact, the concentrated Meiyu rainfall occurring in a small region or a certain period easily results in floods, thus it is worthy to analyze the heterogeneity of Meiyu rainfall over YHRV. In this study, we use both of precipitation concentration period (PCP) and precipitation concentration degree (PCD) based on vector analysis to identify the heterogeneity of Meiyu rainfall over YHRV. On the climatological mean, the concentrated heavy precipitation occurs in late summer over the Yangtze River Delta, where is usually suffered by floods. The dominant two patterns of PCP and PCD variations are northeast–southwest dipole pattern, homogeneous anomalies and homogeneous variation, north–south dipole pattern, respectively. In addition, the relationship on heterogeneity of Meiyu rainfall with sea surface temperature (SST) and the low level summer intraseasonal oscillation (ISO) are investigated. Two key regions of SST activities are found: Bay of Bengal (BOB) and Equatorial eastern Pacific. From BOB, more abundant water vapor has been brought. On the El Niño-Southern Oscillation variation, it is closely relative with PCD–PC1 during the decaying phase of El Niño, while PCP–PC2 is accompanied with developing phase of La Nina events, suggesting a negative feedback of PCP–PC2 on the Niño3.4 SST, and changes to positive during the later winter. On the ISO activities, the robust regions are located over the high-latitude areas, which are closely related with northeastern cold vortex. The north “cold and dry” air southwardly invaded with the lower-level strong warm air in the rainy area, and easily formed an “upper-wet and lower-dry” unstable layer. Under the trigger of the upward motion, the concentrated heavy rainfall easily occurred over YHRV. In all, the homogeneity variation of the concentrated heavy precipitation over YHRV is closely associated with both of the heating forcing (SST) and dynamical atmospheric forcing (low-level ISO).  相似文献   

18.
The variations of both total and extreme precipitations over Asia are characterized by large regional features and seasonality. Extreme precipitation mainly occurs in summer and then in autumn over South Asia but it is a prominent phenomenon in all seasons over Southeast Asia. It explains above 40% of the total precipitation in winter over India, while the ratio of extreme precipitation to total precipitation is 30% or smaller in all seasons over southern-central China. Over Southeast Asia, the largest ratio appears in winter. The extreme precipitation over Southeast Asia (EPSEA) exhibits significant positive trends in all seasons except autumn. The long-term increase in summer EPSEA is associated with significant surface warming over extratropical Asia and the Indo-Pacific oceans and linked to a large-scale anomalous cyclonic pattern over Southeast Asia. An increase in de-trended summer EPSEA is associated with less significant surface warming. However, it is still clearly linked to an anomalous cyclonic pattern over Southeast Asia, contributed by intensifications of monsoon flow from the west, trade wind from the east, and cross-equatorial flow over Indonesia. The antecedent features of increased summer EPSEA include an overall warming over the tropical–subtropical northern hemisphere and an anomalous cyclonic pattern over Southeast Asia in winter and spring. When the large-scale Asian monsoon (measured by the Webster-Yang monsoon index) or the South Asian monsoon is strong, summer extreme precipitation mainly increases over tropical Asia. When monsoon is strong over Southeast Asia or East Asia, extreme precipitation increases over Southeast Asia and decreases over East Asia. A strong summer monsoon over Southeast Asia or East Asia is also followed by decreased autumn extreme precipitation over Southeast Asia.  相似文献   

19.
Theoretical and Applied Climatology - Since soil temperature (ST) is one of the most critical determinants affecting the soil’s physical and chemical properties, the studies on soil...  相似文献   

20.
A model is developed for the large-eddy simulation (LES) of heterogeneous atmosphere and land-surface processes. This couples a LES model with a land-surface scheme. New developments are made to the land-surface scheme to ensure the adequate representation of atmosphere–land-surface transfers on the large-eddy scale. These include, (1) a multi-layer canopy scheme; (2) a method for flux estimates consistent with the large-eddy subgrid closure; and (3) an appropriate soil-layer configuration. The model is then applied to a heterogeneous region with 60-m horizontal resolution and the results are compared with ground-based and airborne measurements. The simulated sensible and latent heat fluxes are found to agree well with the eddy-correlation measurements. Good agreement is also found in the modelled and observed net radiation, ground heat flux, soil temperature and moisture. Based on the model results, we study the patterns of the sensible and latent heat fluxes, how such patterns come into existence, and how large eddies propagate and destroy land-surface signals in the atmosphere. Near the surface, the flux and land-use patterns are found to be closely correlated. In the lower boundary layer, small eddies bearing land-surface signals organize and develop into larger eddies, which carry the signals to considerably higher levels. As a result, the instantaneous flux patterns appear to be unrelated to the land-use patterns, but on average, the correlation between them is significant and persistent up to about 650 m. For a given land-surface type, the scatter of the fluxes amounts to several hundred W $\text{ m }^{-2}$ , due to (1) large-eddy randomness; (2) rapid large-eddy and surface feedback; and (3) local advection related to surface heterogeneity.  相似文献   

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