| With the rapid development of computer technology, there has also been a rapid advance in the climate system model, which has become an important tool for studying the mechanisms and forecast of climate change and has been paid much more attention. So far, there have been many valuable research results. However, there are still some basic or deep-seated problems which are needed to be studied. For example, for a newly developed coupled climate system model, the most basic and critical work is to evaluate its simulation capabilities comprehensively and systematically, which is important for the rational numerical experimentation to study the mechanisms of the external forcing effecting on climate change and the credibility of predicting future climate change. Based on this, according to the mission requirements of the National Science and Technology Support Program project "the numerical simulation of extreme weather and climate events", the ability of the global climate system model BCC_CSM (developed by the National Climate Center) in simulating climatic conditions in China and the surrounding area has been assessed including the atmospheric circulation and meteorological elements. Firstly, the statistics of the height field, average error, the root mean square error, relative root mean square error and spatial correlation coefficient are calculated. Secondly, the capability of the model simulation in simulating the extreme temperatures, the daily average temperature, daily maximum and minimum temperatures, extreme temperature index and its long-term trend has been assessed. Based on this, a numerical experiment of the climate effects of volcanic aerosol has been conducted by using this model, and the radiation forcing and climate changes has been indicated. Finally, the capability of the BCC_CSM model and other models are assessed by comparing the simulation results of12models from CMIP5plan including BCC_CSM model. Moreover, three types of long-term climate test (historical test, controlled trial, climate sensitivity test) have been analyzed and compared, and the effect of the external forcing on climate change has been analyzed. The main conclusions are as follows,1. Through testing, it is found that BCC_CSM1.0model has good ability in simulating the atmospheric circulation and meteorological elements in East Asia especially in simulating the location and intensity of the South Asia High and West Pacific subtropical high, and the simulation results at low levels are better than those at high levels. In addition, the model can also simulate the temperature field in every layer, humidity field and vertical movement very well. Through analyzing the system error deviation of500hPa height field, it is indicated that the model system error is small and affected by seasons, which is positive in spring, summer and autumn, and is negative in winter. Mean square root error is small in low latitudes and slightly large in the high latitudes. Analysis on the relative mean square root error shows that the model system error is mainly affected by terrain, and it is small in all the regions except Qinghai-Tibet Plateau The results stated above shows that the model BCC_CSM1.0is applicable in most of East Asia.The results of the test and evaluation also show that BCC CSM1.0model can simulate the extreme temperature very well. Moreover, the simulation of inter-annual variation, annual variation and seasonal variation of the daily mean temperature is consistent with the observation, except an anomalously low region in the Tibetan Plateau. The simulation of the maximum and minimum temperatures is small in most regions, and the deviation of the simulated maximum and minimum temperatures are slightly low in the southeast coastal region, Xinjiang, Qinghai-Tibet Plateau. The simulation of extreme temperature index is in good agreement in the observation, and both of them show an upward tendency. Hence, it is found that this mode also has the ability to simulate the extreme temperatures evens and associated climate events.2. The climate effects of volcanic ash aerosol are simulated by utilizing BCC_CSM1.0coupled climate system model. The results show that the simulation errors of various meteorological elements are reduced significantly with the volcanic ash aerosol put into the model, and the overall effect of simulation is improved. This indicates that the model atmosphere with the volcanic aerosol is closer to the real atmosphere, and the simulation error decreases significantly in northern hemisphere (NH) than the southern hemisphere (SH). In addition, the most sensitive area of the simulation error change is the area between30°N and35°N. The simulation error decreases more significant in summer than in winter. The trends of the simulation error of height field, sea level pressure and wind fields are consistent with each other. The comprehensive analysis of the global simulation error shows that the simulation of height field is better in low levels than in high level with the radiative forcing effects of volcanic ash aerosol, while it is opposite for temperature field and the absolute humidity field.3. After adding volcanic ash aerosol into the model, the results show that the effects of radiative forcing of volcanic ash aerosol are obvious, which leads to the reduction of downward solar flux near the surface, and the radiative forcing (RF) is negative. The long wave radiation flux varies is different with latitude, which is positive in low latitudes, while negative in high latitudes, and the reduction of radiant flux is mainly in the subtropical and polar regions. Shortwave radiative forcing is negative at the sea ice surface and the open ocean, and the long wave radiative forcing is not obvious. The vertical atmosphere heating rate is also affected by volcanic ash aerosol, that is the long wave radiative cooling is increased in the troposphere and decreased in the stratosphere, and shortwave radiation heating is reduced in the troposphere and increased in the stratosphere. Therefore, the RF of the net radiation heating rate is negative in the troposphere and positive in the stratosphere, which is called "Parasol effect". In addition, the overall effect of the radiative forcing of volcanic aerosols on cloud is that the cloud cooling effect is enhanced. In short, due to the volcanic ash aerosols, the surface of the earth receives less radiation, resulting in that atmospheric heating rate is decreasing in the troposphere and increasing in the stratosphere, which is called "Parasol effect" restraining the troposphere atmospheric heating.4. Three types of simulation test (controlled trial before the industrial revolution, history test; climate sensitivity test) are carried out in China and the surrounding area using BCC_CSM1.1model. The results show that the simulation of temperature, precipitation and evaporation are close to the average value of12models. In the range of35°N-40°N, the change of temperature is smooth compared to other models, and it is highly reliable. Generally speaking, BCC_CSM model has the same trends and range compared to the other11models, indicating its performance and universal is very well.5. The simulation of temperature field from the BCC_CSM1.1model shows that the inner-annual temperature is overall decreasing with small amplitude for the function of comprehensive extra forcing of the difference between historical test and the control test before the industrial revolution. However, the inner-annual temperature is overall increasing for the function of the pre-industrial CO2four times sudden increase reflected by the difference between climate sensitivity test and the control test before the industrial revolution, and the rate of warming is larger on the land than the ocean. In the four seasons, the warming is increasing with latitude, especially in winter. It reveals the fact that the warming has been more significant in the mid-and high latitudes than the low-latitude and more obvious in winter than the other seasons mainly caused by sharp increase of CO2since the global warming which began in the1980s. The changes of precipitation show that either the function of comprehensive external forcing or CO2sudden increase four times has much more impact on summer precipitation in low latitudes than high latitudes. In low latitudes, the effect on the land is greater than that on the ocean. The effect of comprehensive external forcing leads to the increasing of precipitation in summer and winter in most areas, except the equation.For the atmospheric circulation, the combined effects of external forcing are the reduction of the simulation value of the height field in spring, summer and autumn, but increase in winter. The effect of CO2sudden four times increase is the increasing of the simulated troposphere height filed throughout a year. The impact of the high-rise in two experiments is greater in the high levels than the low levels, and the impact on the height field is greater in winter than other seasons.For the effects of the snow cover percentage, the percentage of snow cover increases significantly in the most area due to the combined effects of external forcing, especially in autumn and winter in the Tibetan Plateau. However, the snow cover reduces in all the research areas due to the sudden4times increase of CO2concentration.In summary, the results of three experiments using BCC_CSM1.1show that the temperature decreases and the precipitation reduces due to the overall combined effect of external forcing. Due to the CO2sudden4times increase, both the temperature and precipitation increase. Moreover, the warming range is larger on the land than the ocean, and is larger in high latitudes than in low latitudes especially in winter. Therefore, it reveals the warming in the mid-and high latitudes has been more significant than that in the low-latitude, and the warming has been more obvious in winter than the other seasons mainly caused by sharp increase of CO2since the1980s. |
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