The long-term adjustment processes of atmosphere and ocean in response to gradually increased atmospheric CO2 concentration have been analyzed in 70 and 140 a integrations with NCAR fully-coupled climate system model ...The long-term adjustment processes of atmosphere and ocean in response to gradually increased atmospheric CO2 concentration have been analyzed in 70 and 140 a integrations with NCAR fully-coupled climate system model (CSM). In these experiments the CO2 concentration has been increased to double and quadruples the initial concentration, respectively. After 70 a, at the time of CO2 doubling, the model predicts surface air temperature rises by 1.2 and 1.5 K for the globe and the northwestern Pacific Ocean, respectively. The behavior of the quadrupling run is similar: each global and regional mean surface air temperatures increase by 2.8 and 3.0 K at the time of CO2 quadrupling. From the experiments, surface air temperature changes in the northwestern Pacific Ocean will be more distinctive compared with the global average, mainly due to exceptionally large wanning and sea level change near the entrance of the Kuroshio extension.展开更多
In order to investigate the effects of trace gases on climate variation in the atmosphere, we have devel- oped a primitive equation two-dimensional dynamical climate model with five levels. A series of simula- tion re...In order to investigate the effects of trace gases on climate variation in the atmosphere, we have devel- oped a primitive equation two-dimensional dynamical climate model with five levels. A series of simula- tion results and discussions are shown in this paper, indicating that the model is useful and can correctly reproduced the main feature of the general atmospheric circulation and its seasonal changes. In addition, we have discussed the role of the Qinghai-Xizang Plateau on the formation process of summer monsoon in South Asia and found that the thermal effect of the Qjnghai-Xizang Plateau may not be the main factor controlling the onset and the variation of the summer monsoon in South Asia.展开更多
Tree-ring based temperature reconstructions have successfully inferred the past inter-annual to millennium scales summer temperature variability. A clear relationship between annual and summer temperatures can provide...Tree-ring based temperature reconstructions have successfully inferred the past inter-annual to millennium scales summer temperature variability. A clear relationship between annual and summer temperatures can provide insights into tile variability of past annual mean tem- perature from the reconstructed summer temperature. However, how similar are summer and annual temperatures is to a large extent still unknown. This study aims at investigating the relationship between annual and summer temperatures at different timescales in central Sweden during the last millennium. The temperature variability in central Sweden can represent large parts of Scandinavia which has been a key region for dendroclimatological research. The observed annual and summer temperatures during 1901-2005 were firstly decomposed into different frequency bands using ensemble empirical mode decomposition （EEMD） method, and then the scale-dependent relationship was quantified using Pearson correlation coefficients. The relationship between the observed annual and summer temperatures determined by the instrumental data was subsequently used to evaluate 7 climate models. The model with the best performance was used to infer the relationship for the last millennium. The results show that the relationship between the observed annual and summer temperatures becomes stronger as the timescale increases, except for the 4--16 years timescales at which it does not show any relationship. The summer temperature variability at short timescales （2--4 years） shows much higher variance than the annual variability, while the annual temperature variability at long timescales （〉32 years） has a much higher variance than the summer one. During the last millennium, the simulated summer temperature also shows higher variance at the short timescales （2-4 years） and lower variance at the long timescales （〉1024 years） than those of the annual temperature. The relationship between the two temperatures is generally close at the long timescales, and weak at the short timescales. Overall the summer temperature variability cannot well reflect the annual mean temperature variability for the study region during both the 20th century and the last millennium. Furthermore, all the climate models examined overestimate the annual mean temperature variance at the 2--4 years timescales, which indicates that the overestimate could be one of reasons why the volcanic eruption induced cooling is larger in climate models than in proxy data.展开更多
Polar regions are highly sensitive to climate change and are crucial for regulating the Earth’s climate.While the past climatic changes were forced differently than the ongoing and future anthropogenic changes,such p...Polar regions are highly sensitive to climate change and are crucial for regulating the Earth’s climate.While the past climatic changes were forced differently than the ongoing and future anthropogenic changes,such periods may provide insights into potential future climate impacts and ecosystem feedbacks,especially over centennial-to-millennial timescales that are often not covered by climate model simulations.展开更多
This study reveals the possible future changes in tropical cyclone(TC)landfalling activity along the East Asian coast under different climate change scenarios based on global circulation model(GCM)simulations.Wefirst i...This study reveals the possible future changes in tropical cyclone(TC)landfalling activity along the East Asian coast under different climate change scenarios based on global circulation model(GCM)simulations.Wefirst identify those GCMs that have the“best”performance in simulating the TC activity over the western North Pacific(WNP)during the current climate(1979–2014)by examining the simulated TCs in each of the GCMs and then compare these simulated TCs with the observed TC climatological features of annual frequency,track densities and genesis locations.Based on such comparisons,we have identifiedfive(TaiESM1,EC-Earth3,ACCESS-CM2,ACCESS-ESM1-5 and HadGEM3-GC31-LL)models among all the available GCMs.A multi-model ensemble gives a further improvement when compared with observations.Future projections from some of these models are then used to identify the frequency of TC activity over the entire WNP as well as landfalling TCs in six East Asia coastal regions under two climate change scenarios(SSP2-4.5 and SSP5-8.5)for two periods,2041-70 and 2071-2100.A bias-correction method is also applied to the projected intensity of these landfalling TCs to estimate the landfall intensity.In general,these GCMs project a possible decrease in TC genesis frequency over the entire WNP,consistent with the results of most of the other studies.At mid-century,decreases in TC genesis frequency are projected to be around 10%for both scenarios.Towards the end of the century,the decreases will be more significant,with the percentage changes of 14.9%(SSP2-4.5)and 22.4%(SSP5-8.5).For landfalling TCs,the northern part of the East Asian coast will likely have an increase in frequency,ranging from 17 to 60%but a decrease of 14–27%in the southern part.In general,the average intensity of landfalling TCs will likely increase although the percentages are not large,ranging from 2 to 14%.展开更多
文摘The long-term adjustment processes of atmosphere and ocean in response to gradually increased atmospheric CO2 concentration have been analyzed in 70 and 140 a integrations with NCAR fully-coupled climate system model (CSM). In these experiments the CO2 concentration has been increased to double and quadruples the initial concentration, respectively. After 70 a, at the time of CO2 doubling, the model predicts surface air temperature rises by 1.2 and 1.5 K for the globe and the northwestern Pacific Ocean, respectively. The behavior of the quadrupling run is similar: each global and regional mean surface air temperatures increase by 2.8 and 3.0 K at the time of CO2 quadrupling. From the experiments, surface air temperature changes in the northwestern Pacific Ocean will be more distinctive compared with the global average, mainly due to exceptionally large wanning and sea level change near the entrance of the Kuroshio extension.
文摘In order to investigate the effects of trace gases on climate variation in the atmosphere, we have devel- oped a primitive equation two-dimensional dynamical climate model with five levels. A series of simula- tion results and discussions are shown in this paper, indicating that the model is useful and can correctly reproduced the main feature of the general atmospheric circulation and its seasonal changes. In addition, we have discussed the role of the Qinghai-Xizang Plateau on the formation process of summer monsoon in South Asia and found that the thermal effect of the Qjnghai-Xizang Plateau may not be the main factor controlling the onset and the variation of the summer monsoon in South Asia.
文摘Tree-ring based temperature reconstructions have successfully inferred the past inter-annual to millennium scales summer temperature variability. A clear relationship between annual and summer temperatures can provide insights into tile variability of past annual mean tem- perature from the reconstructed summer temperature. However, how similar are summer and annual temperatures is to a large extent still unknown. This study aims at investigating the relationship between annual and summer temperatures at different timescales in central Sweden during the last millennium. The temperature variability in central Sweden can represent large parts of Scandinavia which has been a key region for dendroclimatological research. The observed annual and summer temperatures during 1901-2005 were firstly decomposed into different frequency bands using ensemble empirical mode decomposition （EEMD） method, and then the scale-dependent relationship was quantified using Pearson correlation coefficients. The relationship between the observed annual and summer temperatures determined by the instrumental data was subsequently used to evaluate 7 climate models. The model with the best performance was used to infer the relationship for the last millennium. The results show that the relationship between the observed annual and summer temperatures becomes stronger as the timescale increases, except for the 4--16 years timescales at which it does not show any relationship. The summer temperature variability at short timescales （2--4 years） shows much higher variance than the annual variability, while the annual temperature variability at long timescales （〉32 years） has a much higher variance than the summer one. During the last millennium, the simulated summer temperature also shows higher variance at the short timescales （2-4 years） and lower variance at the long timescales （〉1024 years） than those of the annual temperature. The relationship between the two temperatures is generally close at the long timescales, and weak at the short timescales. Overall the summer temperature variability cannot well reflect the annual mean temperature variability for the study region during both the 20th century and the last millennium. Furthermore, all the climate models examined overestimate the annual mean temperature variance at the 2--4 years timescales, which indicates that the overestimate could be one of reasons why the volcanic eruption induced cooling is larger in climate models than in proxy data.
基金Ministry of Earth Sciences and the National Centre for Polar and Ocean Research are acknowledged for sustained support under various research grants.This is the NCAOR contribution No.J-60/2019-20.
文摘Polar regions are highly sensitive to climate change and are crucial for regulating the Earth’s climate.While the past climatic changes were forced differently than the ongoing and future anthropogenic changes,such periods may provide insights into potential future climate impacts and ecosystem feedbacks,especially over centennial-to-millennial timescales that are often not covered by climate model simulations.
文摘This study reveals the possible future changes in tropical cyclone(TC)landfalling activity along the East Asian coast under different climate change scenarios based on global circulation model(GCM)simulations.Wefirst identify those GCMs that have the“best”performance in simulating the TC activity over the western North Pacific(WNP)during the current climate(1979–2014)by examining the simulated TCs in each of the GCMs and then compare these simulated TCs with the observed TC climatological features of annual frequency,track densities and genesis locations.Based on such comparisons,we have identifiedfive(TaiESM1,EC-Earth3,ACCESS-CM2,ACCESS-ESM1-5 and HadGEM3-GC31-LL)models among all the available GCMs.A multi-model ensemble gives a further improvement when compared with observations.Future projections from some of these models are then used to identify the frequency of TC activity over the entire WNP as well as landfalling TCs in six East Asia coastal regions under two climate change scenarios(SSP2-4.5 and SSP5-8.5)for two periods,2041-70 and 2071-2100.A bias-correction method is also applied to the projected intensity of these landfalling TCs to estimate the landfall intensity.In general,these GCMs project a possible decrease in TC genesis frequency over the entire WNP,consistent with the results of most of the other studies.At mid-century,decreases in TC genesis frequency are projected to be around 10%for both scenarios.Towards the end of the century,the decreases will be more significant,with the percentage changes of 14.9%(SSP2-4.5)and 22.4%(SSP5-8.5).For landfalling TCs,the northern part of the East Asian coast will likely have an increase in frequency,ranging from 17 to 60%but a decrease of 14–27%in the southern part.In general,the average intensity of landfalling TCs will likely increase although the percentages are not large,ranging from 2 to 14%.
