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Fang Y.,Beijing Climate Center | Zhang Y.,Nanjing University | Huang A.,Nanjing University | Li B.,Key Laboratory of Radiometric Calibration and Validation for Environmental Satellites
Advances in Atmospheric Sciences | Year: 2013

The performance of a regional air-sea coupled model, comprising the Regional Integrated Environment Model System (RIEMS) and the Princeton Ocean Model (POM), in simulating the seasonal and intraseasonal variations of East Asian summer monsoon (EASM) rainfall was investigated. Through comparisons of the model results among the coupled model, the uncoupled RIEMS, and observations, the impact of air-sea coupling on simulating the EASM was also evaluated. Results showed that the regional air-sea coupled climate model performed better in simulating the spatial pattern of the precipitation climatology and produced more realistic variations of the EASM rainfall in terms of its amplitude and principal EOF modes. The coupled model also showed greater skill than the uncoupled RIEMS in reproducing the principal features of climatological intraseasonal oscillation (CISO) of EASM rainfall, including its dominant period, intensity, and northward propagation. Further analysis indicated that the improvements in the simulation of the EASM rainfall climatology and its seasonal variation in the coupled model were due to better simulation of the western North Pacific Subtropical High, while the improvements of CISO simulation were owing to the realistic phase relationship between the intraseasonal convection and the underlying SST resulting from the air-sea coupling. © 2013 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg.

Bodas-Salcedo A.,UK Met Office | Williams K.D.,UK Met Office | Ringer M.A.,UK Met Office | Beau I.,Meteo - France | And 6 more authors.
Journal of Climate | Year: 2014

Current climate models generally reflect too little solar radiation over the Southern Ocean, which may be the leading cause of the prevalent sea surface temperature biases in climate models. The authors study the role of clouds on the radiation biases in atmosphere-only simulations of the Cloud Feedback Model Intercomparison Project phase 2 (CFMIP2), as clouds have a leading role in controlling the solar radiation absorbed at those latitudes. The authors composite daily data around cyclone centers in the latitude band between 40° and 70°S during the summer. They use cloud property estimates from satellite to classify clouds into different regimes, which allow them to relate the cloud regimes and their associated radiative biases to themeteorological conditions in which they occur. The cloud regimes are defined using cloud properties retrieved using passive sensors and may suffer from the errors associated with this type of retrievals. The authors use information from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) lidar to investigate inmore detail the properties of the "midlevel" cloud regime.Most of the model biases occur in the cold-air side of the cyclone composite, and the cyclone composite accounts formost of the climatological error in that latitudinal band. The midlevel regime is themain contributor to reflected shortwave radiation biases. CALIPSO data show that themidlevel cloud regime is dominated by two main cloud types: cloud with tops actually at midlevel and low-level cloud. Improving the simulation of these cloud types should help reduce the biases in the simulation of the solar radiation budget in the Southern Ocean in climate models. © 2014 American Meteorological Society.

Todd-Brown K.E.O.,University of California at Irvine | Randerson J.T.,University of California at Irvine | Hopkins F.,University of California at Irvine | Arora V.,Environment Canada | And 8 more authors.
Biogeosciences | Year: 2014

Soil is currently thought to be a sink for carbon; however, the response of this sink to increasing levels of atmospheric carbon dioxide and climate change is uncertain. In this study, we analyzed soil organic carbon (SOC) changes from 11 Earth system models (ESMs) contributing simulations to the Coupled Model Intercomparison Project Phase 5 (CMIP5). We used a reduced complexity model based on temperature and moisture sensitivities to analyze the drivers of SOC change for the historical and high radiative forcing (RCP 8.5) scenarios between 1850 and 2100. ESM estimates of SOC changed over the 21st century (2090-2099 minus 1997-2006) ranging from a loss of 72 Pg C to a gain of 253 Pg C with a multi-model mean gain of 65 Pg C. Many ESMs simulated large changes in high-latitude SOC that ranged from losses of 37 Pg C to gains of 146 Pg C with a multi-model mean gain of 39 Pg C across tundra and boreal biomes. All ESMs showed cumulative increases in global NPP (11 to 59%) and decreases in SOC turnover times (15 to 28%) over the 21st century. Most of the model-to-model variation in SOC change was explained by initial SOC stocks combined with the relative changes in soil inputs and decomposition rates (R2 Combining double low line 0.89,p< 0.01). Between models, increases in decomposition rate were well explained by a combination of initial decomposition rate, ESM-specificQ10-factors, and changes in soil temperature (R2 Combining double low line 0.80,p< 0.01). All SOC changes depended on sustained increases in NPP with global change (primarily driven by increasing CO2). Many ESMs simulated large accumulations of SOC in high-latitude biomes that are not consistent with empirical studies. Most ESMs poorly represented permafrost dynamics and omitted potential constraints on SOC storage, such as priming effects, nutrient availability, mineral surface stabilization, and aggregate formation. Future models that represent these constraints are likely to estimate smaller increases in SOC storage over the 21st century. ©Author(s) 2014. CC Attribution 3.0 License.

Fengjin X.,Beijing Climate Center | Ziniu X.,Beijing Climate Center
Natural Hazards | Year: 2010

This paper discusses the characteristics of tropical cyclones (TCs) based on available data from 1951 to 2008, including the frequency of TC generation in the Western North Pacific (WNP) and those which make landfall in China. The impacts of TCs on both human and economic losses for the period 1983-2008 are also discussed. Examination of the frequency indicates a decreasing trend in the generation of TCs in the WNP since the 1980s, but the number of TCs making landfall has remained constant or shown only a slight decreasing trend. The number of casualties caused by TCs in China appears to show a slight decreasing trend while the value of economic loss is increasing significantly. These results can be attributed to increased natural disaster prevention and mitigation efforts by the Chinese government in recent years, and also reflect the rapid economic development in China particularly in TC-prone areas. © 2010 Springer Science+Business Media B.V.

Fengjin X.,Beijing Climate Center | Lianchun S.,Beijing Climate Center
Natural Hazards | Year: 2011

The trends of global warming are increasingly significant, especially in the middle and high latitude regions of the northern hemisphere, where the impact of climate change on extreme events is becoming more noticeable. Northeast China is located in a high latitude region and is sensitive to climate change. Extreme minimum temperatures causing cold damage during the warm season is a major type of agro-meteorological disaster in Northeast China, which causes serious reductions in crop yield. In this paper, we analyzed the temporal and spatial trends in the frequency of extreme minimum temperatures during the warm season (from May to September) during 1956-2005 in Northeast China. Abrupt climatic changes were identified using the Mann-Kendall test. The results show that the frequency of extreme minimum temperature days during the warm season in Northeast China decreases significantly from 1956 to 2005 with a background of climate warming. The highest number of extreme minimum temperature days occurred in the 1970s and 1980s, and there was an abrupt climatic change in 1993. The spatial analysis identified that the north and southeast of the region experienced a larger decrease in the number of extreme low temperature days than the west and south of the region. Rice, sorghum, corn, and soybeans are most vulnerable to cold damage. In severe low temperature years, the average crop yield was reduced by 15. 2% in Northeast China. ©. 2011 Springer Science+Business Media B.V.

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