Global aspects of aridity trend Palmer Drought Severity Index for
Aridity trend over northern China is not an isolated phenomenon, but with significant worldwide linkage. The Palmer Drought Severity Index PDSI is the most prominent index of meteorological drought used in the United States Heim 2002 . The PDSI was created by Palmer 1965 with the intent to measure the cumulative departure relative to local mean conditions in atmospheric moisture supply and demand at the surface. A monthly dataset of Palmer Drought Severity Index PDSI from 1870 to 2002 is...
Aridity trend in northwestern China during last ka as seen from lake sediment
As a natural comprehensive unnit which is relatively isolated from the surrounding environment in the continent, lake has been resulted from the interaction among land, atmosphere, water body, and ecosystem in a certain region. The lake level, lake area, water depth and water salinity are therefore used as the indices to reflect the environmental evolution of the region. Lake sediment record is characterized by its rich information, wide distribution and high consistency, which makes it an...
Stratus cloudclimate feedback over the lee side of the TP
Over subtropical eastern China, the cloud amount and surface temperature exhibits a pronounced negative correlation. The spatial pattern of the correlation coefficients between the observed anomalous monthly cloud fractions and the anomalous surface temperatures shows that the most significant negative correlation is found along the Yangtze River valley Figure not shown . Over the Sichuan basin 27 32 N, 103 108 E where the cloud-radiative forcing is strongest, the correlation coefficient of...
Fsi a a saT Fxw FA Flh F Fm
where FS is the downward shortwave radiation flux density at the surface, aS the surface reflectivity, s the surface longwave radiation emissivity, G the Stefan-Boltzmann constant, TS the surface temperature, FlW the downward atmospheric longwave radiation flux density at the surface, Fsh the upward surface sensible heat flux density, the upward surface latent heat flux density, Fgi the sensible heat flux density to soil, which may be neglected due to its smaller value than the other terms, and...
Western Pacific subtropical high
The summertime rainfall in China and the East Asian monsoon activities are strongly influenced by the western Pacific subtropical high WPSH . The WPSH, particularly its location changes on seasonal and interannual timescales are strongly affected by both the ENSO-related thermodynamics in the tropical western Pacific and the convection activities in this region. When the west Pacific is in its warmer episode during the developing phase of a La Ni a event, the convections around the Philippine...
Severe agrometeorological disasters caused by the climate change
The recent research demonstrated that the trends of frequency and intensity of extreme precipitation events had increased under the background of global warming, especially the ratio of extreme precipitation events in the 1990s. The annual rainfall and the extreme rainfall have increased in the areas of the Yangtze River basin, which are the important agricultural areas in China. Most of the rainfall and water-logging in the middle-lower reaches of the Yangtze River are concentrated in the...
References Fde
Barnett TP, Dumenil L, Schiese V, Roeckner E, Latif M 1989 The effect of Eurasian snow cover on regional and global climate variations. J. Atmos. Sci. 46 661-685 Bolin B 1950 On the influence of the earth's orography on the westerlies. Tellus 2 184-195 Broccoli AJ, Manabe S 1992 The Effects of Orography on Midlatitude Northern Hemisphere Dry Climates. J. Climate 5 1181-1201 Charney JG, Eliassen A 1949 A numerical method for predicting the perturbations of the middle latitude westerlies. Tellus...
Computational methods of the atmospheric heat sourcesink
The heat source sink for a given air column is defined as lt gt SH Rnet LP 6.1 where SH is the sensible heat flux at the surface Rnet the radiation in the atmosphere and LP the condensation-released latent heat they are defined as follows Rnet So 1 - Ap - S 1 - A Re - Rm 6-4 where Cp denotes the specific heat constant of air at constant pressure p the surface air density Ch the turbulent heat exchange coefficient V Vu2 v2 the surface scalar wind ta the temperature at screen height ts the soil...
Formation of the nimbostratus and altostratus clouds
Nimbostratus and altostratus clouds generally cover a vast area and have a bulky vertical extent. The nimbostratus is sometimes thick enough to block out entirely the direct solar beam. The nimbostratus clouds have low cloud base and considerable vertical development, bringing the tops into the middle tropospheric level. The nimbostratus and altostratus often form when stably stratified moist air is forced by steady mechanical lifting over a large area. This often happens at a warm or cold...
Introduction Sfs
Having steadily improved their general performance in simulation of global climate, Coupled Global Climate Models CGCMs are now the primary tools to study the climatic processes, natural variability and response to external forcings. However, due to their significant complexity and the climate change community's requirement for long-term integration, the atmospheric components of the most CGCMs usually have their horizontal resolutions limited from 400 km to 125 km, so they are unable to...
Study on multiRCM ensemble of regional climate simulation for Asia
The performance of climate models are affected by many factors such as the dynamic framework, parameterization scheme of physical processes, initial and driving fields, horizontal and vertical resolution, and so on. So far neither any single global or regional model can be satisfied in every aspects of climate simulation. Since the chaos phenomenon in the atmosphere was discovered by Lorenz 1963 , meteorologists have carried on many researches on the forecast uncertainty. Due to the limitation...
Simulation of climate of China and East Asia through intercomparison of a set
Although regional climate models have shown promising performance in reproducing the regional detail in surface climate characteristics as forced by regional details, such as topography, lakes, the coastline, and land-use distribution, more systematic and wider application of RCMs to adequately assess their performance and uncertainties in producing the regional climate information is required. To serve this purpose, several inter-comparison projects on regional climate modeling are being...
Historical documents
Documentary data is one of the main proxy data in examining climate change in historical time. China has a long history and a plenty of historical document records. The historical documents most distributed in the eastern China, which including direct climate records about droughts, floods, rainfall, snow, freezing, frost, wind and fall dust. And also some of indirect records on climate are available, such as crop production, famine, population, insect diseases etc. Chinese historiographers and...
Loess
In the northwestern China, the loess plateau with maximum depth of 3000 m provides very important paleoclimate records Ding et al., 1994 for the million years before present. Temperatures and precipitation in the Quaternary 2.4 2.5Ma BP to present are reconstructed based on the analyses of magnetization and the size of particles of loess. The reconstruction from loess records show that there were about thirty-seven glacial-interglacial cycles in the past 2.5Ma and with different periodicities....
A hydrological model embedded in BATs
A hydrological model VXM including the heterogeneities of precipitation and infiltration facility is embedded in land surface scheme BATs in RIEMS Version 2. While some models ignoring the heterogeneity and use uniform soil when calculating infiltration capacity, the Xinanjiang Model Zhao, 1984 , on the other hand, considers the heterogeneity in infiltration capacity mainly due to soil texture, and is also applied to many investigations. VIC model the Variable Infiltration Capacity Model was...
Glossary Acronyms
4DDA - Four-dimensional data assimilation models ACC - Anomalous Correlation Coefficients AGCM - Atmospheric General Circulation Model AMOGCM - Atmospheric General Circulation Model with Mixed-layer Ocean and Sea Ice Thermodynamic Models AO - Antarctic Oscillation ASM - Asian summer monsoon BC - black carbon BCC_CM1 - Beijing Climate Center_climate system model version1 BIOME - a major region of distinctive plant and animal groups well adapted to the physical environment of its distribution...
Late MiocenePliocene aridification history of the Asian interior
The climates of Asia are affected significantly by the extent and height of the Himalayan Mountains and the Tibetan plateau. Uplift of this region began about 50Myr ago, and further significant increases in altitude of the Tibetan plateau are thought to have occurred about 10 8Myr ago, or more recently An Zhisheng, et al., 2001 . The deserts of northern China, covering an area of about 1.5 x 106 km2, together make up the world's largest mid-latitude, temperate, continental interior desert. The...
References Tzm
Avissar R, Pielke RA 1989 A parameterization of heterogeneous land surfaces for atmospheric numerical models and its impact on regional meteorology. Monthly Weather Review 117 2113-2136 Avissar R, Chen F 1994 The impact of land-surface wetness heterogeneity on mesoscale heat fluxes. J Applied Meteorology 33 1382-1401 Chang JT, Wetzel PJ 1991 Effect of special variation of soil moisture and vegetation on the evolution of a pre-storm enviroment A numerical case study. Monthly Weather Review 119...
Phase one of RMIP
Ten research groups from the Asia-Pacific area are currently participating in the project, and eight of them have contributed their simulation results to RMIP's phase one. Phase one of RMIP for Asia reveals the capacities of regional climate models RCMs for simulating the Asian monsoon climate and extreme events as well Fu et al., 2005 . The simulation domain covers most of Asia and parts of the surrounding ocean waters in order to encompass the Asian monsoon circulation internally. Standard...
Longterm field observation at Tongyu a Reference Site of CEOP program in
From 2002, long-term intensified CO2, sensible and latent heat fluxes were measured continuously in the semi-arid cropland and degraded grassland surfaces in Tongyu, Northeastern China. The Tongyu observation site is also one the reference sites of the international CEOP program Coordinate Water and Energy cycle Observation Project, Bosilovich et al., 2002 . The main objectives of this long-term observation are the following Liu HZ et al., 2004 investigate the effects of the land use on the...
Features of vertically integrated moisture transport
Moisture transport, especially the vertically integrated moisture transport VIMT , is directly associated with monsoon rainfalls. The moisture carried by monsoon plays an important role in the moisture balance in the monsoon regions Xu, 1958 Xie and Dai, 1959 , therefore, investigations on moisture transport have always been in the highlight He and Murakami, 1983 Tang et al., 1985 Wu, 1990 Ding 1995 . Many recent studies have pointed out that the moisture transport by the southerly in summer...
Annual cycle of snow cover
Over the TP snow season normally begins in mid-September Figure not shown . Snow cover growth is rapid in the first half of winter, with the maximum occurring in January. This is followed by a slow decline until June. The long snow season, early snow peak, rapid snow growth, and slow snow decay are evident. Of all snow seasons, winter December, January, and February has the greatest snow storage. The winter, spring March, April and May , and autumn September, October and November are...
Possible mechanisms of the influences of the Northeast Cold Vortex on Meiyu
Studies Sun, 1997 showed that the NECV is reflected as a cold low center at the 500 hPa weather chart. In order to testify whether NECVI defined here can describe effectively the conceptual picture of NECV and its structure, the composite difference fields of geopotential height and temperature at 500 hPa between strong NECV high NECVI years and weak NECV low NECVI years in the First Flood Period are calculated Fig. 1.14 . It can be seen from the height field Fig. 1.14a that regions from North...
Climate effect of the Northeast Cold Vortex and its influence on Meiyu
Meiyu i.e. Changma in Korea or Baiu in Japan , which is the product of the advancement of the East Asian summer monsoon Zhu, 1934 Tu, 1944 , occurs in June-July in boreal summer extending eastward from the mid-lower reaches of Yangtze River to Korea Peninsula and Japan. There are quantities of studies on Meiyu in many countries Tao and Chen, 1987 Fu and Teng, 1988 Wu and Liu, 1995 Zhang, 2001 Zhang and Qian, 2002 Xu et al., 2002 Zhang et al., 2002 Huang et al., 2005 , but affecting factors in...
Extratropical cyclones
One of the hypothesized effects of global warming from increasing concentrations of greenhouse gases is a change in the frequency and or intensity of extra-tropical cyclones McCabe et al., 2001 . Extra-tropical cy-conles are baroclinic low pressure systems that occur throughout the mid-latitudes of both hemispheres. Their potential for causing property damage, particular as winter storms, is well documented IPCC, 2001 . Severe storms cause tremendous property damage in the country each year....
Seasonal distribution
The total vertically integrated water vapor flux vector Q can be expressed as Where S is the acceleration of gravity, Ps represents surface pressure, and P stands for top pressure which is 300 hPa here. The amount of specific humidity above 300 hPa is poorly known and therefore is not considered Kalnay et al., 1996 . In the tropics, specific humidity above 300 hPa is at least two orders smaller than that near the surface, and moisture transport is therefore of negligible influence to the...
Impacts of human activity on river runoff in the northern area of China
Global environment has changed very much with human activity. There is no exception to hydrological regimes Conway, 2001 Garcia, et al., 1998 . In fact, due to agricultural, industrial, urban development, such as irrigation and drainage, hydraulic structure across a river, the elements of hydrological cycle have changed in terms of quantity and quality, both in time and in space. In this section, an attempt is made to analyze quantitatively the effect of human activity on river runoff in...
Temperature simulation in Exp
Fig.2.9 plotted the differences of simulated temperature between 6 kaPB and 0 kaBP. In the west of Eurasia, annual temperature at 6 kaBP was 00.5 C warmer than that in the present in the south of 50 N, and colder than present in the north of 50 N Fig.2.9a . In the East Asia, summer temperature was about 2.0 C warmer at 6 kaBP than the present in the south of 40 N Fig.2.9b , and winter temperature decreased about 2.0 C Fig.2.9c at 6 kaBP comparing with the present. This result agrees with those...
Relationship between the Northeast Cold Vortex and Meiyu rainfall amount
Fig. 1.13 shows correlation coefficients of the NECVI and rainfall amounts during Meiyu period. The areas from the mid-lower reaches of Yangtze River to the Korea Peninsula and Japan are positively correlated, indicating that when NECVI is larger i.e. NECV is stronger , there may be more rainfalls, but when NECVI is smaller i.e. NECV is weaker , there may be less rainfalls in the Meiyu region in East Asia Wu et al., 2006a . That is, the Meiyu rainfall amount may be more in strong NECV years and...
Wet spells
Due to its localized feature, definitions of wet spells vary from region to region. In order to reveal the comparative characteristics of wet spells throughout China, uniform criteria on wet spell have been defined based on previous definitions used in different regions. The detailed definition is described in the following. 1 In a wet spell, the number of rainy days daily precipitation 0.1mm should be no less than 4 days, and no dry day daily precipitation lt 0.1mm in the first 3 days. 2 A wet...
Validation of land surface model based on field observations over semiarid area
The terrestrial biosphere is an integral part of both the global carbon and hydrological cycles. Every year about 14 of the carbon in the atmospheric is exchanged with the terrestrial biosphere, and about 20 of the water added to the atmosphere annually derives from evapotranspiration from the land Wesfall and Stumm, 1980 Friend 1997 . Researches on carbon and hydrological cycles of the terrestrial ecosystem have been one of the main issues in the global change science. For the purpose of...
Interdecadal oceanic anomalies in the North Pacific
The PDO is a coherent ocean-atmosphere signature in the North Pacific on the interdecadal timescales. The fingerprint of the PDO is visible both in the atmosphere and ocean. The typical PDO patterns can be illustrated by regressing the SST and upper-ocean 500m heat content anomalies upon the PDO index. Fig 3.1a shows the temporal variation of the PDO index during 19002000, which is calculated with the GISST dataset. A remarkable feature of this index is its tendency for multiyear and...
References Rsr
Chen KM, Zhang XH, Jin XZ, Lin WY, Yu YQ, Guo YF 1996 Primary analysis on experiments of increasing greenhouse effects by a coupled atmospheric and oceanic general circulation model. In Collection of Climate Change and Numerical Simulations II, ed. by 85-913-02 project, China Meteorological Press, Beijing, pp.61-84 in Chinese . Chen LX, Song YK 1996 Analysis of the simulations by the CCM1 and the in-tercomparison with other GCMs. In Collection of Climate Change and Numerical Simulations II, ed....
References Tov
Alley RB, Mayewski PA, Sowers T, Stuiver M, Taylor KC, Clark TU. 1997. Holocene climate instability aprominent, widespread event 8200 years ago. Geology 25 483-6. An ZS, Kukla G, Porter SC, Xiao JL, 1991 Magnetic susceptibility evidence of monsoon variation on the Loess Plateau of central China during the last 130,000 years. Quaternary Research 36, 29-36. An ZS, Thompson, LG 1998 Paleoclimatic change of monsoonal China linked to global change. In Galloway, J.N. Ed. , Proceedings of Global...
Palaeoclimate simulations of midHolocene and LGM
Reconstructions from proxy data, including pollen, lake-level, and loess records, have been providing a picture of regional climate changes of China during the Quaternary. The General Circulation Models GCMs has been used to explore the mechanisms of observed regional and global climate in the past decades. By use of GCMs, we can simulate the atmospheric response to the external forcing in LGM 21ka B.P. and mid-Holocene 6ka B.P. . Some model simulations have demonstrated the importance of...
IOD phenomenon
The Indian Ocean dipole IOD is a manifestation of the Indian Ocean Variability IOV on the interannual timescale Saji et al., 1999 . It explains about 12 of the total variance of anomalous Indian Ocean Sea Surface Temperatures SST . The Indian Ocean Dipole Mode Index IODMI is defined as the difference in SST anomaly between the tropical western Indian Ocean 50oE-70oE, -10oS-10oN, named as Box A and the southeastern Indian Ocean 90oE- 110oE, 10oS- equator, named as Box B . To describe the IOD...
Individual influences of IOD and ENSO
People nowadays have been paying more and more attention to the IOD impacts on the EASC e.g., Behera et al., 1999 Ashok et al., 2001 Guan and Yamagata, 2003 Saji and Yamagata, 2003 Xiao et al., 2000 . Without having the ENSO influences removed, the significant correlation is found between the IOD and variables including winds in South Asia, Tibetan High, and WPSH Li and Mu, 2001 . However, because some positive negative IOD events co-occurred with El Ni o La Ni a , it is obviously very...
Semiarid regionthe area with most significant aridity trend
As a natural process of earth evolution, the huge arid and semi-arid regions formed at the Asia continent at the time of rapid uplifting of Tibetan plateau in about 3.6-2.6 million years B.P. An et al, 2003 . Based on the Koppen classification of climate Henry Kendall et al, 1976 , The geographic location of semi-arid regions covers central Asia as well as some part of India sub-continent, where the potential evaporation excess the precipitation on annual average and the landscapes are...