Fu Congbin

Comparison of products from ERA-40, NCEP-2, and CRU with station data for summer precipitation over China

Summer precipitation products from the 45-Year European Centre for Medium-Range Weather Forecast (ECMWF) Reanalysis (ERA-40), and NCEP-Department of Energy (DOE) Atmospheric Model Intercomparison Project (AMIP-H) Reanalysis (NCEP-2), and Climatic Research Unit (CRU) TS 2.1 dataset are compared with the corresponding observations over China in order to understand the quality and utility of the reanalysis datasets for the period 1979–2001. The results reveal that although the magnitude and location of the rainfall belts differ among the reanalysis, CRU, and station data over South and West China, the spatial distributions show good agreement over most areas of China. In comparison with the observations in most areas of China, CRU best matches the observed summer precipitation, while ERA-40 reports less precipitation and NCEP-2 reports more precipitation than the observations. With regard to the amplitude of the interannual variations, CRU is better than either of the reanalyses in representing the corresponding observations. The amplitude in NCEP-2 is stronger but that of ERA-40 is weaker than the observations in most study domains. NCEP-2 has a more obvious interannual variability than ERA-40 or CRU in most areas of East China. Through an Empirical orthogonal function (EOF) analysis, the main features of the rainfall belts produced by CRU agree better with the observations than with those produced by the reanalyses in the Yangtze-Huaihe River valley. In East of China, particularly in the Yangtze-Huaihe River valley, CRU can reveal the quasi-biennial oscillation of summer precipitation represented by the observations, but the signal of ERA-40 is comparatively weak and not very obvious, whereas that of NCEP-2 is also weak before 1990 but very strong after 1990. The results also suggest that the magnitude of the precipitation difference between ERA-40 and the observations is smaller than that between NCEP-2 and the observations, but the variations represented by NCEP-2 are more reasonable than those given by ERA-40 in most areas of East China to some extent.

The Influence of Vegetation Cover on Summer Precipitation in China: a Statistical Analysis of NDVI and Climate Data

This study provides new evidence for the feedback effects of vegetation cover on summer precipitation in different regions of China by calculating immediate (same season), and one-and two-season lagged correlations between the normalized difference vegetation index (NDVI) and summer precipitation. The results show that the correlation coefficients between NDVI in spring and the previous winter and precipitation in summer are positive in most regions of China, and they show significant difference between regions. The stronger one-and two-season lagged correlations occur in the eastern arid/semi-arid region, Central China, and Southwest China out of the eight climatic regions of China, and this implies that vegetation cover change has more sensitive feedback effects on summer precipitation in the three regions. The three regions are defined as sensitive regions. Spatial analyses of correlations between spring NDVI averaged over each sensitive region and summer precipitation of 160 stations suggest that the vegetation cover strongly affects summer precipitation not only over the sensitive region itself but also over other regions, especially the downstream region.

Inter-comparison of 10-year precipitation simulated by several RCMs for Asia

In phase II of the Regional Climate Model Inter-comparison Project (RMIP) for Asia, the regional climate has been simulated for July 1988 through December 1998 by five regional climate models and one global variable resolution model. Comparison of the 10-year simulated precipitation with the observations was carried out. The results show that most models have the capacity to reproduce the basic spatial pattern of precipitation for Asia, and the main rainbelt can be reproduced by most models, but there are distinctions in the location and the intensity. Most models overestimate the precipitation over most continental regions. Interannual variability of the precipitation can also be basically simulated, while differences exist between various models and the observations. The biases in the stream field are important reasons behind the simulation errors of the Regional Climate Models (RCMs). The cumulus scheme and land surface process have large influences on the precipitation simulation. Generally, the Grell cumulus scheme produces more precipitation than the Kuo scheme.

Simulation of the radiative effect of black carbon aerosols and the regional climate responses over China

As part of the development work of the Chinese new regional climate model (RIEMS), the radiative process of black carbon (BC) aerosols has been introduced into the original radiative procedures of RIEMS, and the transport model of BC aerosols has also been established and combined with the RIEMS model. Using the new model system, the distribution of black carbon aerosols and their radiative effect over the China region are investigated. The influences of BC aerosole on the atmospheric radiative transfer and on the air temperature, land surface temperature, and total rainfall are analyzed. It is found that BC aerosols induce a positive radiative forcing at the top of the atmosphere (TOA), which is dominated by shortwave radiative forcing. The maximum radiative forcing occurs in North China in July and in South China in April. At the same time, negative radiative forcing is observed on the surface. Based on the radiative forcing comparison between clear sky and cloudy sky, it is found that cloud can enforce the TOA positive radiative forcing and decrease the negative surface radiative forcing. The responses of the climate system in July to the radiative forcing due to BC aerosols are the decrease in the air temperature in the middle and lower reaches of the Changjiang River and Huaihe area and most areas of South China, and the weak increase or decrease in air temperature over North China. The total rainfall in the middle and lower reaches of the Changjiang River area is increased, but it decreased in North China in July.

Twenty first century climatic and hydrological changes over Upper Indus Basin of Himalayan region of Pakistan

This study is based on both the recent and the predicted twenty first century climatic and hydrological changes over the mountainous Upper Indus Basin (UIB), which are influenced by snow and glacier melting. Conformal-Cubic Atmospheric Model (CCAM) data for the periods 1976–2005, 2006–2035, 2041–2070, and 2071–2100 with RCP4.5 and RCP8.5; and Regional Climate Model (RegCM) data for the periods of 2041–2050 and 2071–2080 with RCP8.5 are used for climatic projection and, after bias correction, the same data are used as an input to the University of British Columbia (UBC) hydrological model for river flow projections. The projections of all of the future periods were compared with the results of 1976–2005 and with each other. Projections of future changes show a consistent increase in air temperature and precipitation. However, temperature and precipitation increase is relatively slow during 2071–2100 in contrast with 2041–2070. Northern parts are more likely to experience an increase in precipitation and temperature in comparison to the southern parts. A higher increase in temperature is projected during spring and winter over southern parts and during summer over northern parts. Moreover, the increase in minimum temperature is larger in both scenarios for all future periods. Future river flow is projected by both models to increase in the twenty first century (CCAM and RegCM) in both scenarios. However, the rate of increase is larger during the first half while it is relatively small in the second half of the twenty first century in RCP4.5. The possible reason for high river flow during the first half of the twenty first century is the large increase in temperature, which may cause faster melting of snow, while in the last half of the century there is a decreasing trend in river flow, precipitation, and temperature (2071–2100) in comparison to 2041–2070 for RCP4.5. Generally, for all future periods, the percentage of increased river flow is larger in winter than in summer, while quantitatively large river flow was projected, particularly during the summer monsoon. Due to high river flow and increase in precipitation in UIB, water availability is likely to be increased in the twenty first century and this may sustain water demands.

Simulation of Extreme Climate Events over China with Different Regional Climate Models

Abstract During phase II of the Regional Climate Model Inter-comparison Project (RMIP) for Asia, the Asian climate was estimated from July 1988 to December 1998 using six climate models. In this paper, the abilities of six climate models to simulate several important extreme climate events in China during the last years of the last century were analyzed. The modeled results for the intensity of the precipitation anomaly over the Yangtze-Huaihe Valley during the summers of 1991 and 1998 were weaker than the observed values. The positive precipitation anomaly responsible for a catastrophic flood in 1991 was well reproduced in almost all simulation results, but the intensity and range of the precipitation anomaly in 1998 were weaker in the modeled results. The spatial distribution of extreme climate events in 1997, when severe drought affected North China and flood impacted South China, was reproduced by most of the regional models because the anomaly of the large-scale background field was well-simulated, despite poor simulation of high temperature areas in the north during the summer by all models.

Interdecadal change of atmospheric stationary waves and North China drought

The inderdecadal change of atmospheric stationary waves (ATW) has been investigated for the two periods 1956?77 and 1978?99. The trough of ATW in the middle and low layer of the troposphere over the Asian continent has experienced a significant weakening during the past two decades, which exerts a great influence on the North China climate. The ATW in 200 hPa has also exhibited some changes since 1977, as a stationary ridge appeared over the northwestern China while a stationary trough appeared above North China. This leads to an increasing of the upward motion above northwestern China and a decreasing above North China. A west?east section of the stationary waves at 40 degrees N shows that the ATW above North China tilted westward for the period 1956?77, but was almost upright during 1978?99. The composite analysis confirms that the climate mean ATW pattern after 1977 is similar to the dry pattern for North China, while the rainy pattern is similar to that before 1977. In consequence, the North China drought is partly due to the interdecadal change of the ATW over boreal Asia in the recent two decades.

Streamflow simulation for the Yellow River basin using RIEMS and LRM

The streamflow over the Yellow River basin is simulated by using the high-resolution Regional Integrated Environmental Model System (RIEMS), and an off-line Large-scale Routing Model (LRM). The RIEMS was designed and has been developed by the Global Change System for Analysis, Research and Training Regional Center for Temperate East Asia (START/TEA) since 1991 and has a good capability to simulate the regional climate of East Asia. The LRM is based on the assumption of linearity and time invariance and can calculate the horizontal travel of water. The RIEMS-LRM allows the direct comparison of predicted and observed streamflow data for large-scale rivers. The application of the RIEMS-LRM to the upper reaches of the Yellow River verifies that the coupled model system has the capability to simulate the streamflow over a large-scale river. Furthermore, the paper discusses the reasons leading to simulation errors.The streamflow over the Yellow River basin is simulated by using the high-resolution Regional Integrated Environmental Model System (RIEMS), and an off-line Large-scale Routing Model (LRM). The RIEMS was designed and has been developed by the Global Change System for Analysis, Research and Training Regional Center for Temperate East Asia (START/TEA) since 1991 and has a good capability to simulate the regional climate of East Asia. The LRM is based on the assumption of linearity and time invariance and can calculate the horizontal travel of water. The RIEMS-LRM allows the direct comparison of predicted and observed streamflow data for large-scale rivers. The application of the RIEMS-LRM to the upper reaches of the Yellow River verifies that the coupled model system has the capability to simulate the streamflow over a large-scale river. Furthermore, the paper discusses the reasons leading to simulation errors.

On a simple dynamics model of interaction between oasis and climate

This paper constructs a coupled system of oasis and atmosphere based on an oasis evolvement model by adding atmospheric motion to discuss the problem of oasis evolvement and its effects on regional climate. The results indicate that the range and scope of the negative temperature anomalies become larger when the oasis cover fraction increases. Correspondingly, the positive temperature anomalies becomes smaller in the desert no matter in summer or spring. And the variability is more obvious in summer than in spring. So it may be concluded that the oasis not only maintains and develops itself but also develops partial air over the desert into an oasis climate.

An aridity trend in china and its abrupt feature in association with the global warming

A distinct aridity trend in China in last 100 years is presented by applying a linear fitting to both the climate records and the hydrological records, which is supported by evidence of environmental changes and seems to be associated with a global warming trend during this period.The Mann Kendall Rank statistic tesi reveals a very interesting feature that the climate of China entered into a dry regime abruptly in about 1920s, which synchronized with the rapid warming of the global temperature at almost the same time.According to an analysis of the meridional profile of observed global zonal mean precipitation anomalies during the peak period of global warming (1930-1940), the drought occurred in whole middle latitude zone (25°N-55°N) of the Northern Hemisphere, where the most part of China is located in. Although this pattern is in good agreement with the latitude distribution of the difference of zonal mean rates of precipitation between 4 x CO2 and 1 x CO2 simulated by climate model (Manabe and Wetherald, 1983), more studies are required to understand the linkage between the aridity trend in China and the greenhouse effect.The EOF analysis of the Northern Hemisphere sea level pressure for the season of June to August shows an abrupt change of the time coefficient of its first eigenvector from positive to negative in mid-1920s, indicating an enhancement of the subtropical high over Southeast Asia and the western Pacific after that time. This is an atmospheric circulation pattern that is favorable to the development of dry climate in China.