Time filter

Source Type

Wang Y.,Tongji University | Jian Z.M.,Tongji University | Zhao P.,National Meteorological Information Center | Zhao P.,State Key Laboratory of Severe Weather
Geophysical Research Letters | Year: 2012

In a 46-kyrs' transient accelerated simulation with the NCAR Community Climate System Model version 3 (CCSM3), the increased July insolation at precessional bands causes a drastic summer warming in North Africa, the midlatitudes of Eurasia from surface to the upper troposphere, with a cooling troposphere in the Northwest Pacific (NWP), which intensifies the land-ocean thermal contrast between Eurasia and its adjacent oceans. Associated with the tropospheric temperature variations are a lower-tropospheric strengthened low-pressure system from North Africa to the mid-high latitudes of Eurasia and a lower-tropospheric strengthened high-pressure system over the NWP. Meanwhile, the strengthened southwesterly or southerly winds prevail over the Asian monsoon region, indicating a stronger Asian summer monsoon. Summer precipitation increases in tropical Africa, South Asia, and the mid-high latitudes of East Asia, with a decreased precipitation over South China and the NWP. This response of atmospheric circulation and monsoon precipitation to the precessional changes is explained in the context of the extratropical Asian-Pacific Oscillation. © 2012. American Geophysical Union.

Lu E.,Nanjing University of Information Science and Technology | Lu E.,National Oceanic and Atmospheric Administration | Zeng Y.,Nanjing University of Information Science and Technology | Luo Y.,State Key Laboratory of Severe Weather | And 7 more authors.
Journal of Geophysical Research D: Atmospheres | Year: 2014

Using observed precipitation and the National Centers for Environmental Prediction-National Center for Atmospheric Research reanalysis, the changes in the metrics of the summer precipitation in China, the dominance of frequency and intensity of daily extreme precipitation, and the linkage with changes in moisture and air temperature are explored. Results show that over the recent 50 years, the total summer rainfall increased over the southeast and the west and decreased over the northeast. The changes in the frequency, identified with the 95% threshold and Poisson regression, and rainfall extremes show similar spatial patterns. The relative importance of the changes in frequency and intensity in the variability and changes in extreme precipitation are estimated. It is shown that, while the interannual variability of the rainfall amount is dominated by the frequency change in almost all stations, the long-term change of rainfall amount can be dominated by both frequency and intensity, depending on the station. The change in the rainfall total is linked to changes in atmospheric moisture and temperature. The results show that the variability and change of the rainfall total can be dominated by changes in both moisture and air temperature, and the relative importance depends on the region. ©2014. American Geophysical Union. All Rights Reserved.

Xiao D.,Chinese Academy of Meteorological Sciences | Zhou X.,Chinese Academy of Meteorological Sciences | Zhou X.,State Key Laboratory of Severe Weather | Zhao P.,National Meteorological Information Center
Science China Earth Sciences | Year: 2012

Despite many studies on reconstructing the climate changes over the last millennium in China, the cause of the China's climate change remains unclear. We used the UVic Earth System Climate Model (UVic Model), an Earth system model of intermediate complexity, to investigate the contributions of climate forcings (e. g. solar insolation variability, anomalous volcanic aerosols, greenhouse gas, solar orbital change, land cover changes, and anthropogenic sulfate aerosols) to surface air temperature over East China in the past millennium. The simulation of the UVic Model could reproduce the three main characteristic periods (e. g. the Medieval Warm Period (MWP), the Little Ice Age (LIA), and the 20th Century Warming Period (20CWP)) of the northern hemisphere and East China, which were consistent with the corresponding reconstructed air temperatures at century scales. The simulation result reflected that the air temperature anomalies of East China were larger than those of the global air temperature during the MWP and the first half of 20CWP and were lower than those during the LIA. The surface air temperature of East China over the past millennium has been divided into three periods in the MWP, four in the LIA, and one in the 20CWP. The MWP of East China was caused primarily by solar insolation and secondarily by volcanic aerosols. The variation of the LIA was dominated by the individual sizes of the contribution of solar insolation variability, greenhouse gas, and volcano aerosols. Greenhouse gas and volcano aerosols were the main forcings of the third and fourth periods of the LIA, respectively. We examined the nonlinear responses among the natural and anthropogenic forcings in terms of surface air temperature over East China. The nonlinear responses between the solar orbit change and anomalous volcano aerosols and those between the greenhouse gases and land cover change (or anthropogenic sulfate aerosols) all contributed approximately 0. 2°C by the end of 20th century. However, the output of the energy-moisture balance atmospheric model from UVic showed no obvious nonlinear responses between anthropogenic and natural forcings. The nonlinear responses among all the climate forcings (both anthropogenic and natural forcings) contributed to a temperature increase of approximately 0. 27°C at the end of the 20th century, accounting for approximately half of the warming during this period; the remainder was due to the climate forcings themselves. © 2012 Science China Press and Springer-Verlag Berlin Heidelberg.

Wang Z.,National Climate Center | Yang S.,Sun Yat Sen University | Yang S.,State Key Laboratory of Severe Weather | Ke Z.,National Climate Center | Jiang X.,Institute of Plateau Meteorology
Journal of Applied Meteorology and Climatology | Year: 2014

Based on the observational datasets of rime and glaze from 743 stations in China and the atmospheric circulation data from the NCEP-NCAR reanalysis during 1954-2009, large-scale atmospheric and oceanic conditions for extensive and persistent rime and glaze events were examined with a composite analysis. Results show that rime events mostly occur in northern China while glaze events are mainly observed in southern China. The icing events are accompanied by low temperature and high humidity but not necessarily by abovenormal precipitation. The Asian low, blocking highs, strong moisture transport, and an inversion layer related to major abnormal circulation systems contribute to the occurrence and persistence of icing events in China. The Ural blocking high plays a major role in the glaze events, and the Okhotsk blocking high is closely related to the rime events. For glaze events, extratropical circulation anomalies and the southward outbreak of cold air play a dominant role. In contrast, the strong northward transport of warm and moist airflows plays a leading role and the blocking high and the southward outbreak of extratropical cold air take a supporting role for rime events. There is nearly an equal chance for occurrences of rime events under La Niña and El Niño backgronally, the sea surface temperatures from the tropical Indian Ocean to the tropical northwestunds. However, glaze events more likely occur under the background of La Niña. Additioern Pacific Ocean also contribute to the occurrence and maintenance of icing events in China. © 2014 American Meteorological Society.

Zhou Y.,CAS Institute of Atmospheric Physics | Zhou Y.,State Key Laboratory of Severe Weather | Cui C.,Institute of Heavy Rain
Advances in Atmospheric Sciences | Year: 2011

The surface rainfall processes associated with the torrential rainfall event over Hubei, China, during July 2007 were investigated using a two-dimensional cloud-resolving model. The model integrated the large-scale vertical velocity and zonal wind data from National Centers for Environmental Prediction (NCEP)/Global Data Assimilation System (GDAS) for 5 days. The time and model domain mean surface rain rate was used to identify the onset, mature, and decay periods of rainfall. During the onset period, the descending motion data imposed in the lower troposphere led to a large contribution of stratiform rainfall to the model domain mean surface rainfall. The local atmospheric drying and transport of rain from convective regions mainly contributes to the stratiform rainfall. During the mature periods, the ascending motion data integrated into the model was so strong that water vapor convergence was the dominant process for both convective and stratiform rainfall. Both convective and stratiform rainfalls made important contributions to the model domain mean surface rainfall. During the decay period, descending motion data input into the model prevailed, making stratiform rainfall dominant. Stratiform rainfall was mainly caused by the water vapor convergence over raining stratiform regions. © 2011 Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg.

Discover hidden collaborations