Links with the Tibetan uplift and the ice buildup in the northern hemisphere
Two main factors may be invoked to explain the desertification in the interior of Asia in the Late Miocene-Pliocene time. Climate models suggest that the uplift of the Tibetan Plateau may have played an important role in Asian aridification through modulating the atmospheric circulation and its barrier effect to moisture (Ruddiman and Kutzbach, 1989 Manabe and Broccoli, 1990 An et al., 2001). Another factor is the ongoing global cooling and the expansion of Arctic ice-sheet, which is likely to...
Droughts
Meteorological droughts are normally defined as abnormal periods of moisture deficiency relative to the long-term average over a given region (Heddinghaus et al., 1991). It is well known that droughts are one of the most damaging climate-related hazards to impact societies (Woodhouse and Overpeck, 1998). The Palmer Drought Severity Index (PDSI) (Dai et al., 2004) show the global very dry areas (PDSI< -3.0) increased remarkably since the late 1970s due to decreased precipitation and increased...
Simulations of the effect of snow on precipitation
In order to simulate the influences of the TP snow anomalies on the re gional climate in China, the second version of the NCAR (National Center for Atmospheric Research) regional climate model (RegCM2) is used with the model domain containing the TP and the horizontal resolution being 120 km with 11 levels in the vertical. The turbulence kinetic energy (TKE) scheme and a new computational scheme of boundary layer tops with much better effectiveness of simulation are incorporated to replace the...
Desert migrations during the past Ma
The long-term evolution of the deserts of northern China remains poorly understood because of the sparseness of directly extractable geological evidence of suitable type and quality to be found within them. Given that the loess deposits making up the Loess Plateau of China lie immediately south and southeast of these deserts, and so are largely a product of winds from these dryland sources, it is considered that well-dated, semi-continuous loess records may provide valuable insights into the...
Stratus generated by the TP and its possible climate effects
Stratus in the southeast China is very common during the winter and early spring season, with stratus cloud amounts near 50 during DJF and MAM. Klein and Hartmann (1993) noticed that all of the regions with a significant fraction of stratus clouds are located over cold oceans except over China. Distinctive from low marine stratus clouds, the stratus clouds over eastern China are primarily middle clouds (Yu et al. 2001). In this section, special attention will be paid to the radiative...
Droughts and floods in China In Reaches of Yangtze and Huaihe Rivers
Most of the flood drought events in the eastern part of China are due to the anomalous Meiyu precipitation in June and July in reaches of Yangtze and Huaihe rivers. Meiyu is known as a phenomena designated by a rain belt that elongates in zonal and moves in a quasi-stationary way in meridional. This rain belt is always related to some fronts with sometime the strong convections around them. Meiyu can be influenced by ENSO. In different stages of El Ni o events, rainfall in the eastern part of...
Interdecadal variation of aridity trend in northern China associated with the Pacific Decadal Oscillation PDO
Recently, the relationships between the climate variations in China and the PDO have been explicitly examined (Yang et al., 2002 Zhu and Yang, 2003b Yang et. al. 2004 Ma et al., 2006). The oceanic features of the Pacific Decadal Oscillation (PDO) and the associated interdecadal climate anomalies in East Asia and China are described with NCEP NCAR reanalysis data and station records for 19511998 by using regression analysis. The interdecadal change of the impact of ENSO on the summertime climate...
Projections of changes in temperature Global climate modeling
There are two main experiments using global climate models to pro ject the future temperature changes over China. The first one is the near-equilibrium or transient experiment, i.e. the equilibrium climate sensitivity derived from doubled CO2 or the transient climate response at the CO2 doubling in 1 yr or 2 yr CO2 increasing experiment. Table 10.1 gives the temperature changes in East Asia due to the doubled CO2 by Chinese scientists (Li et al, 1995 Chen et al, 1996 and Guo et al, 2001), and...
Warm days and cool days
The development of a suite of climate change indices which primarily focus on extremes provided a useful tool to monitor and detect climate change (Alexander et al., 2006). Temperature indices derived from daily maximum and minimum temperature comprises absolute and percentile-based indices. Percentile-based indices include occurrence of warm days (TX90p), cool days (TX10p), warm nights (TN90p) and cool nights (TN10p) (Table 8.1) (Zhang et al., 2005). Results showed the warm days in China...
Impact of climate change on water supplydemand balance
Climate anomaly is an important factor influencing the demand of agricultural and industrial water resource. Taking the Nanjing and Hangzhou city located in eastern China as examples, the demand of production water exhibits a moderate positive correlation with the July temperature. In addition, the irrigation water for agriculture is closely correlated with the precipitation in Jiangsu province (Yuan et al. 2000). Liu (1997) used the output of GCM model with 2 * CO2 concentration (by 2030) as...
Introduction
As a natural process of earth evolution, huge arid and semi-arid regions formed over northern part of China, occupy nearly 40 of China terrestrial area (Fig. 5.1) (Liu Tungsheng and Ding Zhongli, 1999 An et al., 2001 Zhang Jiacheng, 1991). The landscape of these areas are featured largely by desert, semi-desert and grassland and characterized by dry climate, low nutrition content and low capacity of water conservation of the soil (Fu and Wen, 2002 Zhu Zhenda, 1985 Dong Guangrong, 1997). The...
Impact of land surface degradation in northern China on regional climate
The climatic and environmental effect of land use cover change has always been considered as one important aspect of global change study, and is also one of focuses of four international global environmental change research programs (IGBP, IHDP, WCRP, and DIVERSATE). But up to now, the studies of land-atmosphere interaction especially the feedback effects of vegetation cover on climate have mostly focused on the tropic region, where the impact of thermodynamic forcing is large and the impact of...
Impact of climate change on evaporation
Besides runoff, evaporation is also a major component of water cycle. Its variation is closely related to the climate conditions, such as temperature, wind speed, etc. Guo et al. (2005) investigated the trend of evaporation in Yellow river-Huaihe river basin and analyzed its possible reasons based on the observed pan evaporation data from 117 observatories during the period of 19562000. A significant decrease trend of -50 mm 10a in the evaporation was found in the area. The maximum rate of...
Design of simulation
In this experiment 21ka BP simulation is driven by two kinds of forcing conditions. One is associated with solar radiation, e.g. earth orbital parameters (perihelion, eccentricity and obliquity). The other is associated with the earth surface conditions, including sea surface temperatures (SSTs), snow and ice coverage, atmospheric CO2 concentration and vegetation. In order to identify the climate change at 21ka BP from the present, we run both Oka and 21ka BP experiments. In the Oka (control)...
The earliest onset of Asian summer monsoon and the regional characteristics
As the onset of summer monsoon is always accompanied with convec-tive rainfalls, and, low TBB can figure convective clouds and rainfalls, TBB data are used to discuss the characteristics of seasonal transition in Asian-Australian monsoon region and the initial onset of ASM. Fig 1.2 shows the horizontal distribution of the climatological TBB from March to June. The distribution of TBB in March (Fig 1.2a) is still the same as in January (figure omitted). There is a high TBB belt in the subtropics...
Temporal and spatial variation characteristics of soil moisture
The temporal and spatial variations of soil moisture are analyzed using in-situ soil moisture data from 98 agricultural meteorological gauge stations in Eastern China for the years 1981 - 1991. The data includes gravimetric soil moisture, field capacity, bulk density of soil and wilting level. Distributions of gauge stations for soil moisture measurement are shown by Fig. 7.3, in which F represents non irrigation and T for irrigation. Irrigation stations will not be used in analysis in order to...
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 records
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
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...
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 of regional climate models
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...
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 Miocene Pliocene 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...
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 semiarid region of China
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
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
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 of China
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...
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...
