Orbital-scale global climatic changes during the late Quaternary are dominated by high-latitude influenced~100,000-year global ice-age cycles and monsoon influenced~23,000-year low-latitude hydroclimate variations.How...Orbital-scale global climatic changes during the late Quaternary are dominated by high-latitude influenced~100,000-year global ice-age cycles and monsoon influenced~23,000-year low-latitude hydroclimate variations.However,the shortage of highly-resolved land temperature records remains a limiting factor for achieving a comprehensive understanding of long-term low-latitude terrestrial climatic changes.Here,we report paired mean annual air temperature(MAAT)and monsoon intensity proxy records over the past 88,000 years from Lake Tengchongqinghai in southwestern China.While summer monsoon intensity follows the~23,000-year precession beat found also in previous studies,we identify previously unrecognized warm periods at 88,000-71,000 and 45,000-22,000 years ago,with 2-3℃amplitudes that are close to our recorded full glacial-interglacial range.Using advanced transient climate simulations and comparing with forcing factors,we find that these warm periods in our MAAT record probably depends on local annual mean insolation,which is controlled by Earth’s~41,000-year obliquity cycles and is anti-phased to annual mean insolation at high latitudes.The coincidence of our identified warm periods and intervals of high-frequent dated archaeological evidence highlights the importance of temperature on anatomically modern humans in Asia during the last glacial stage.展开更多
That a model has sensitivity responses to parameter uncertainties is a key concept in implementing model parameter es- timation using filtering theory and methodology. Depending on the nature of associated physics and...That a model has sensitivity responses to parameter uncertainties is a key concept in implementing model parameter es- timation using filtering theory and methodology. Depending on the nature of associated physics and characteristic variability of the fluid in a coupled system, the response time scales of a model to parameters can be different, from hourly to decadal. Unlike state estimation, where the update frequency is usually linked with observational frequency, the update frequency for parameter estimation must be associated with the time scale of the model sensitivity response to the parameter being esti- mated. Here, with a simple coupled model, the impact of model sensitivity response time scales on coupled model parameter estimation is studied. The model includes characteristic synoptic to decadal scales by coupling a long-term varying deep ocean with a slow-varying upper ocean forced by a chaotic atmosphere. Results show that, using the update frequency deter- mined by the model sensitivity response time scale, both the reliability and quality of parameter estimation can be improved significantly, and thus the estimated parameters make the model more consistent with the observation. These simple model results provide a guideline for when real observations are used to optimize the parameters in a coupled general circulation model for improving climate analysis and prediction initialization.展开更多
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences(XDB40010200 and XDA2009000004)the Program of Global Change and Mitigation+1 种基金Ministry of Science and Technology of China(2016YFA0600502)the National Natural Science Foundation of China(41877293,41672162,41977381,and 41472315)。
文摘Orbital-scale global climatic changes during the late Quaternary are dominated by high-latitude influenced~100,000-year global ice-age cycles and monsoon influenced~23,000-year low-latitude hydroclimate variations.However,the shortage of highly-resolved land temperature records remains a limiting factor for achieving a comprehensive understanding of long-term low-latitude terrestrial climatic changes.Here,we report paired mean annual air temperature(MAAT)and monsoon intensity proxy records over the past 88,000 years from Lake Tengchongqinghai in southwestern China.While summer monsoon intensity follows the~23,000-year precession beat found also in previous studies,we identify previously unrecognized warm periods at 88,000-71,000 and 45,000-22,000 years ago,with 2-3℃amplitudes that are close to our recorded full glacial-interglacial range.Using advanced transient climate simulations and comparing with forcing factors,we find that these warm periods in our MAAT record probably depends on local annual mean insolation,which is controlled by Earth’s~41,000-year obliquity cycles and is anti-phased to annual mean insolation at high latitudes.The coincidence of our identified warm periods and intervals of high-frequent dated archaeological evidence highlights the importance of temperature on anatomically modern humans in Asia during the last glacial stage.
基金funded by the National Natural Science Foundation of China (Grant No.41676088)the National Key Research and Development Project of China (2016YFC1401800,2017YFC1404100,2017YFC1404102)+1 种基金the Fundamental Research Funds for the Central Universities (HEUCF 041705)the Foundation of the Key Laboratory of Marine Environmental Information Technology
文摘That a model has sensitivity responses to parameter uncertainties is a key concept in implementing model parameter es- timation using filtering theory and methodology. Depending on the nature of associated physics and characteristic variability of the fluid in a coupled system, the response time scales of a model to parameters can be different, from hourly to decadal. Unlike state estimation, where the update frequency is usually linked with observational frequency, the update frequency for parameter estimation must be associated with the time scale of the model sensitivity response to the parameter being esti- mated. Here, with a simple coupled model, the impact of model sensitivity response time scales on coupled model parameter estimation is studied. The model includes characteristic synoptic to decadal scales by coupling a long-term varying deep ocean with a slow-varying upper ocean forced by a chaotic atmosphere. Results show that, using the update frequency deter- mined by the model sensitivity response time scale, both the reliability and quality of parameter estimation can be improved significantly, and thus the estimated parameters make the model more consistent with the observation. These simple model results provide a guideline for when real observations are used to optimize the parameters in a coupled general circulation model for improving climate analysis and prediction initialization.
