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Seasonal Differences of Model Predictability and the Impact of SST in the Pacific

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Advances in Atmospheric Sciences 2005年第1期22卷 103-113页

作者：郎咸梅王会军 nansen-zhu international research Center

Both seasonal potential predictability and the impact of SST in the Pacific on the forecast skill over China are investigated by using a 9-level global atmospheric general circulation model developed at the Institute of Atmospheric Physics under the Chinese Academy of Sciences (IAP9L-AGCM). For each year during 1970 to 1999, the ensemble consists of seven integrations started from consecutive observational daily atmospheric fields and forced by observational monthly SST. For boreal winter, spring and summer, the variance ratios of the SST-forced variability to the total variability and the differences in the spatial correlation coefficients of seasonal mean fields in special years versus normal years are computed respectively. It follows that there are slightly inter-seasonal differences in the model potential predictability in the Tropics. At northern middle and high latitudes, prediction skill is generally low in spring and relatively high either in summer for surface air temperature and middle and upper tropospheric geopotential height or in winter for wind and precipitation. In general, prediction skill rises notably in western China, especially in northwestern China, when SST anomalies (SSTA) in the Nino-3 region are significant. Moreover, particular attention should be paid to the SSTA in the North Pacific (NP) if one aims to predict summer climate over the eastern part of China, i.e., northeastern China, North China and southeastern China.

关键词： predictability IAP9L-AGCM sea surface temperature

Impact of Topography and Land-Sea Distribution on East Asian Paleoenvironmental Patterns

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Advances in Atmospheric Sciences 2006年第2期23卷 258-266页

作者：张仲石王会军郭正堂姜大膀 Institute of Geology and Geophysics nansen-zhu international research Center

Much geological research has illustrated the transition of paleoenvironmental patterns during the Cenozoic from a planetary-wind-dominant type to a monsoon-dominant type, indicating the initiation of the East Asian monsoon and inland-type aridity. However, there is a dispute about the causes and mechanisms of the transition, especially about the impact of the Himalayan/Tibetan Plateau uplift and the Paratethys Sea retreat, Thirty numerical sensitivity experiments under different land-sea distributions and Himalayan/Tibetan Plateau topography conditions are performed here to simulate the evolution of climate belts with emphasis on changes in the rain band, and these are compared with the changes in the paleoenvironmental patterns during the Cenozoic recovered by geological records. The consistency between simulations and the geological evidence indicates that both the Tibetan Plateau uplift and the Paratethys Sea retreat play important roles in the formation of the monsoon-dominant environmental pattern. Furthermore, the simulations show the monsoon-dominant environmental pattern comes into being when the Himalayan/Tibetan Plateau reaches 1000-2000 m high and the Paratethys Sea retreats to the Turan Plate.

关键词： Paratethys Sea retreat Himalayan/Tibetan Plateau uplift paleoenvironmental pattern precipitation field Turan Plate

Changes in Daily Climate Extremes of Observed Temperature and Precipitation in China

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Atmospheric and Oceanic Science Letters 2013年第5期6卷 312-319页

作者： WANG Ai-Hui FU Jian-Jian nansen-zhu international research centre Institute of Atmospheric Physics

Daily precipitation for 1960-2011 and maximum/minimum temperature extremes for 1960-2008 recorded at 549 stations in China are utilized to investigate climate extreme variations.A set of indices is derived and analyzed with a main focus on the trends and variabilities of daily extreme *** show significant increases in daily extreme warm temperatures and decreases in daily extreme cold temperatures,defined as the number of days in which daily maximum temperature （Tmax） and daily minimum temperature （Tmin） are greater than the 90th percentile and less than thel0th percentile,***,the trend magnitudes are larger in indices derived from Tmin than those from *** of percentile-based precipitation indices show distinct spatial patterns with increases in heavy precipitation events,defined as the top 95th percentile of daily precipitation,in westem and northeastern China and in the low reaches of the Yangtze River basin region,and slight decreases in other *** precipitation,defined as the tail of the 5th percentile of daily precipitation,however,decreases in most *** annual maximum consecutive dry days （CDD） show an increasing trend in southem China and the middle-low reach of the Yellow River basin,while the annual maximum consecutive wet days （CWD） displays a downtrend over most regions except western *** indices vary significantly with regions and ***,occurrences of extreme events in China are more frequent,particularly the night time extreme temperature,and landmasses in China become warmer and wetter.

关键词： climate extremes temperature rain maximum dry/wet days

Influence of Internal Decadal Variability on the Summer Rainfall in Eastern China as Simulated by CCSM4

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Advances in Atmospheric Sciences 2016年第6期33卷 706-714页

作者： Yali zhu Tao WANG Jiehua MA nansen-zhu international research centre Chinese Academy of Sciences Climate Change research centre Chinese Academy of Sciences

The combined impact of the Pacific Decadal Oscillation （PDO） and Atlantic Multidecadal Oscillation （AMO） on the summer rainfall in eastern China was investigated using CCSM4. The strongest signals occur with the combination of a positive PDO and a negative AMO （＋PDO- AMO）, as well as a negative PDO and a positive AMO （-PDO ＋ AMO）. For the ＋PDO- AMO set, significant positive rainfall anomalies occur over the lower reaches of the Yangtze River valley （YR）, when the East Asian summer monsoon becomes weaker, while the East Asian westerly jet stream becomes stronger, and ascending motion over the YR becomes enhanced due to the jet-related secondary circulation. Contrary anomalies occur over East Asia for the -PDO ＋ AMO set. The influence of these two combinations of PDO and AMO on the summer rainfall in eastern China can also be observed in the two interdecadal rainfall changes in eastern China in the late 1970s and late 1990s.

关键词： Pacific Decadal Oscillation Atlantic Multidecadal Oscillation eastern China summer rainfall CCSM4

Ocean Data Assimilation with Background Error Covariance Derived from OGCM Outputs

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Advances in Atmospheric Sciences 2004年第2期21卷 181-192页

作者：符伟伟周广庆王会军 nansen-zhu international research centre (NZC) Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029

The background error covariance plays an important role in modern data assimilation and analysis systems by determining the spatial spreading of information in the data. A novel method based on model output is proposed to estimate background error covariance for use in Optimum Interpolation. At every model level, anisotropic correlation scales are obtained that give a more detailed description of the spatial correlation structure. Furthermore, the impact of the background field itself is included in the background error covariance. The methodology of the estimation is presented and the structure of the covariance is examined. The results of 20-year assimilation experiments are compared with observations from TOGA-TAO (The Tropical Ocean-Global Atmosphere-Tropical Atmosphere Ocean) array and other analysis data.

关键词： data assimilation background error model output covariance

The Springtime North Asia Cyclone Activity Index and the Southern Annular Mode

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Advances in Atmospheric Sciences 2008年第4期25卷 673-679页

作者：乐旭王会军 nansen-zhu international research centre(NZC) Institute of Atmospheric Physics(IAP)Chinese Academy of Sciences(CAS)

The relationship between the North Asia cyclone （NAC） activity and the Southern Annular Mode （SAM） is documented in this research. The definition of the NAC index （NACI） is based on the atmospheric relative vorticity in North Asia. The analysis yields a significant positive correlation between previous winter Southern Annular Mode index （SAMI） and spring NACI in the interannual variability, with a correlation coefficient of 0.51 during 1948-2000. Analysis of the NAC-related and SAM-related atmospheric general circulation variability demonstrates such a relationship. The study further reveals that when the winter SAM becomes strong, the springtime atmospheric convection in tropical western Pacific will intensify and the local Hadley circulation will be strengthened. As a result, the abnormal subsiding motion over South China makes the temperature gradient intensified in the low level and strengthens the jet in the high level, both of which are beneficial to the development of NAC activity.

关键词： North Asia cyclone Southern Annular Mode atmospheric general circulation

The influence of tropical Indian Ocean warming on the Southern Hemispheric stratospheric polar vortex

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Science China Earth Sciences 2009年第3期52卷 323-332页

作者： LI ShuangLin nansen-zhu international research centre, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China nansen-zhu international research centre Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China

During the past decades, concurrent with global warming, most of global oceans, particularly the tropical Indian Ocean, have become warmer. Meanwhile, the Southern Hemispheric stratospheric polar vortex (SPV) exhibits a deepening trend. Although previous modeling studies reveal that radiative cooling effect of ozone depletion plays a dominant role in causing the deepening of SPV, the simulated ozone-depletion-induced SPV deepening is stronger than the observed. This suggests that there must be other factors canceling a fraction of the influence of the ozone depletion. Whether the tropical Indian Ocean warming (IOW) is such a factor is unclear. This issue is addressed by conducting ensemble atmospheric general circulation model (AGCM) experiments. And one idealized IOW with the amplitude as the observed is prescribed to force four AGCMs. The results show that the IOW tends to warm the southern polar stratosphere, and thus weakens SPV in austral spring to summer. Hence, it offsets a fraction of the effect of the ozone depletion. This implies that global warming will favor ozone recovery, since a warmer southern polar stratosphere is un-beneficial for the formation of polar stratospheric clouds (PSCs), which is a key factor to ozone depletion chemical reactions.

关键词： tropical Indian Ocean warming Southern Hemispheric stratospheric polar vortex atmospheric general circulation model ensemble experiments planetary wave

Paleoclimate Modelling at the Institute of Atmospheric Physics, Chinese Academy of Sciences

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Advances in Atmospheric Sciences 2006年第6期23卷 1040-1049页

作者：姜大膀张仲石 nansen-zhu international research centre Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029

Paleoclimate modelling is one of the core topics in the Past Global Changes project under the international Geosphere-Biosphere Programme and has received much attention worldwide in recent decades. Here we summarize the research on the Paleoclimate modeling, including the Holocene, Last Glacial Maximum, and pre-Quaternary climate intervals or events performed at the Institute of Atmospheric Physics under the Chinese Academy of Sciences （IAP/CAS） for over one decade. As an attempt to review these academic activities, we emphasize that vegetation and ocean feedbacks can amplify East Asian climate response to the Earth＇s orbital parameters and atmospheric CO2 concentration at the mid-Holocene. At the Last Glacial Maximum, additional cooling in interior China is caused by the feedback effects of East Asian vegetation and the ice sheet over the Tibetan Plateau, and the regional climate model RegCM2 generally reduces data-model discrepancies in East Asia. The simulated mid-Pliocene climate is characterized by warmer and drier conditions as well as significantly weakened summer and winter monsoon systems in interior China. On a tectonic timescale, both the Tibetan Plateau uplift and the Paratethys Sea retreat play important roles in the formation of East Asian monsoon-dominant environmental pattern during the Cenozoic.

关键词： Paleoclimate modelling mid-Holocene Last Glacial Maximum mid-Pliocene Cenozoic

Interdecadal Variability of the East Asian Summer Monsoon in an AGCM

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Advances in Atmospheric Sciences 2007年第5期24卷 808-818页

作者：韩晋平王会军 nansen-zhu international research centre(NZC) Institute of Atmospheric Physics Chinese Academy of SciencesBeijing 100029 Graduate University of Chinese Academy of SciencesBeijing 100049 nansen-zhu international research centre(NZC) Institute of Atmospheric Physics Chinese Academy of SciencesBeijing 100029

It is well known that significant interdecadal variation of the East Asian summer monsoon （EASM） occurred around the end of the 1970s. Whether these variations can be attributed to the evolution of global sea surface temperature （SST） and sea ice concentration distribution is investigated with an atmospheric general circulation model （AGCM）. The model is forced with observed monthly global SST and sea ice evolution through 1958-1999. A total of four integrations starting from different initial conditions are carried out. It is found that only one of these reproduces the observed interdecadal changes of the EASM after the 1970s, including weakened low-level meridional wind, decreased surface air temperature and increased sea level pressure in central China, as well as the southwestward shift of the western Pacific subtropical high ridge and the strengthened 200-hPa westerlies. This discrepancy among these simulated results suggests that the interdecadal variation of the EASM cannot be accounted for by historical global SST and sea ice evolution. Thus, the possibility that the interdecadal timescale change of monsoon is a natural variability of the coupled climate system evolution cannot be excluded.

关键词： global sea surface temperature sea ice East Asian summer monsoon interdecadal change