2017 Vol. 34, No. 8
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2017, 34(8): 941-951.
doi: 10.1007/s00376-017-6238-8
Abstract:
This paper presents new high-resolution proxies and paleoclimatic reconstructions for studying climate changes in China for the past 2000 years. Multi-proxy synthesized reconstructions show that temperature variation in China has exhibited significant 50-70-yr, 100-120-yr, and 200-250-yr cycles. Results also show that the amplitudes of decadal and centennial temperature variation were 1.3C and 0.7C, respectively, with the latter significantly correlated with long-term changes in solar radiation, especially cold periods, which correspond approximately to sunspot minima. The most rapid warming in China occurred over AD 1870-2000, at a rate of 0.56 0.42C (100 yr)-1; however, temperatures recorded in the 20th century may not be unprecedented for the last 2000 years, as data show records for the periods AD 981-1100 and AD 1201-70 are comparable to the present. The ensemble means of dryness/wetness spatial patterns in eastern China across all centennial warm periods illustrate a tripole pattern: dry south of 25N, wet from 25-30N, and dry to the north of 30N. However, for all centennial cold periods, this spatial pattern also exhibits a meridional distribution. The increase in precipitation over the monsoonal regions of China associated with the 20th century warming can primarily be attributed to a mega El Nio-Southern Oscillation and the Atlantic Multidecadal Oscillation. In addition, a significant association between increasing numbers of locusts and dry/cold conditions is found in eastern China. Plague intensity also generally increases in concert with wetness in northern China, while more precipitation is likely to have a negative effect in southern China.
This paper presents new high-resolution proxies and paleoclimatic reconstructions for studying climate changes in China for the past 2000 years. Multi-proxy synthesized reconstructions show that temperature variation in China has exhibited significant 50-70-yr, 100-120-yr, and 200-250-yr cycles. Results also show that the amplitudes of decadal and centennial temperature variation were 1.3C and 0.7C, respectively, with the latter significantly correlated with long-term changes in solar radiation, especially cold periods, which correspond approximately to sunspot minima. The most rapid warming in China occurred over AD 1870-2000, at a rate of 0.56 0.42C (100 yr)-1; however, temperatures recorded in the 20th century may not be unprecedented for the last 2000 years, as data show records for the periods AD 981-1100 and AD 1201-70 are comparable to the present. The ensemble means of dryness/wetness spatial patterns in eastern China across all centennial warm periods illustrate a tripole pattern: dry south of 25N, wet from 25-30N, and dry to the north of 30N. However, for all centennial cold periods, this spatial pattern also exhibits a meridional distribution. The increase in precipitation over the monsoonal regions of China associated with the 20th century warming can primarily be attributed to a mega El Nio-Southern Oscillation and the Atlantic Multidecadal Oscillation. In addition, a significant association between increasing numbers of locusts and dry/cold conditions is found in eastern China. Plague intensity also generally increases in concert with wetness in northern China, while more precipitation is likely to have a negative effect in southern China.
2017, 34(8): 952-964.
doi: 10.1007/s00376-017-6226-z
Abstract:
Taking winter and summer in eastern China as an example application, a grid-cell method of aerosol direct radiative forcing (ADRF) calculation is examined using the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model with inputs from MODIS and AERONET observations and reanalysis data. Results show that there are significant seasonal and regional differences in climatological mean aerosol optical parameters and ADRF. Higher aerosol optical depth (AOD) occurs in summer and two prominent high aerosol loading centers are observed. Higher single scattering albedo (SSA) in summer is likely associated with the weak absorbing secondary aerosols. SSA is higher in North China during summer but higher in South China during winter. Aerosols induce negative forcing at the top of the atmosphere (TOA) and surface during both winter and summer, which may be responsible for the decrease in temperature and the increase in relative humidity. Values of ADRF at the surface are four times stronger than those at the TOA. Both AOD and ADRF present strong interannual variations; however, their amplitudes are larger in summer. Moreover, patterns and trends of ADRF do not always correspond well to those of AOD. Differences in the spatial distributions of ADRF between strong and weak monsoon years are captured effectively. Generally, the present results justify that to calculate grid-cell ADRF at a large scale using the SBDART model with observational aerosol optical properties and reanalysis data is an effective approach.
Taking winter and summer in eastern China as an example application, a grid-cell method of aerosol direct radiative forcing (ADRF) calculation is examined using the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model with inputs from MODIS and AERONET observations and reanalysis data. Results show that there are significant seasonal and regional differences in climatological mean aerosol optical parameters and ADRF. Higher aerosol optical depth (AOD) occurs in summer and two prominent high aerosol loading centers are observed. Higher single scattering albedo (SSA) in summer is likely associated with the weak absorbing secondary aerosols. SSA is higher in North China during summer but higher in South China during winter. Aerosols induce negative forcing at the top of the atmosphere (TOA) and surface during both winter and summer, which may be responsible for the decrease in temperature and the increase in relative humidity. Values of ADRF at the surface are four times stronger than those at the TOA. Both AOD and ADRF present strong interannual variations; however, their amplitudes are larger in summer. Moreover, patterns and trends of ADRF do not always correspond well to those of AOD. Differences in the spatial distributions of ADRF between strong and weak monsoon years are captured effectively. Generally, the present results justify that to calculate grid-cell ADRF at a large scale using the SBDART model with observational aerosol optical properties and reanalysis data is an effective approach.
2017, 34(8): 965-976.
doi: 10.1007/s00376-017-6221-4
Abstract:
Monitoring atmospheric carbon dioxide (CO2) from space-borne state-of-the-art hyperspectral instruments can provide a high precision global dataset to improve carbon flux estimation and reduce the uncertainty of climate projection. Here, we introduce a carbon flux inversion system for estimating carbon flux with satellite measurements under the support of The Strategic Priority Research Program of the Chinese Academy of SciencesClimate Change: Carbon Budget and Relevant Issues. The carbon flux inversion system is composed of two separate parts: the Institute of Atmospheric Physics Carbon Dioxide Retrieval Algorithm for Satellite Remote Sensing (IAPCAS), and CarbonTracker-China (CT-China), developed at the Chinese Academy of Sciences. The Greenhouse gases Observing SATellite (GOSAT) measurements are used in the carbon flux inversion experiment. To improve the quality of the IAPCAS-GOSAT retrieval, we have developed a post-screening and bias correction method, resulting in 25%-30% of the data remaining after quality control. Based on these data, the seasonal variation of XCO2 (column-averaged CO2 dry-air mole fraction) is studied, and a strong relation with vegetation cover and population is identified. Then, the IAPCAS-GOSAT XCO2 product is used in carbon flux estimation by CT-China. The net ecosystem CO2 exchange is -0.34 Pg C yr-1 ( 0.08 Pg C yr-1), with a large error reduction of 84%, which is a significant improvement on the error reduction when compared with in situ-only inversion.
Monitoring atmospheric carbon dioxide (CO2) from space-borne state-of-the-art hyperspectral instruments can provide a high precision global dataset to improve carbon flux estimation and reduce the uncertainty of climate projection. Here, we introduce a carbon flux inversion system for estimating carbon flux with satellite measurements under the support of The Strategic Priority Research Program of the Chinese Academy of SciencesClimate Change: Carbon Budget and Relevant Issues. The carbon flux inversion system is composed of two separate parts: the Institute of Atmospheric Physics Carbon Dioxide Retrieval Algorithm for Satellite Remote Sensing (IAPCAS), and CarbonTracker-China (CT-China), developed at the Chinese Academy of Sciences. The Greenhouse gases Observing SATellite (GOSAT) measurements are used in the carbon flux inversion experiment. To improve the quality of the IAPCAS-GOSAT retrieval, we have developed a post-screening and bias correction method, resulting in 25%-30% of the data remaining after quality control. Based on these data, the seasonal variation of XCO2 (column-averaged CO2 dry-air mole fraction) is studied, and a strong relation with vegetation cover and population is identified. Then, the IAPCAS-GOSAT XCO2 product is used in carbon flux estimation by CT-China. The net ecosystem CO2 exchange is -0.34 Pg C yr-1 ( 0.08 Pg C yr-1), with a large error reduction of 84%, which is a significant improvement on the error reduction when compared with in situ-only inversion.
2017, 34(8): 977-982.
doi: 10.1007/s00376-017-6228-x
Abstract:
Using the southern limit of snowfall recorded in Chinese documents, chronologies of tree-ring width, and tree-ring stable oxygen isotope (\(\updelta^{18}\)O), the annual temperature anomaly in southern China during 1850-2009 is reconstructed using the method of signal decomposition and synthesis. The results show that the linear trend was 0.47C (100 yr)-1 over 1871-2009, and the two most rapid warming intervals occurred in 1877-1938 and 1968-2007, at rates of 0.125C (10 yr)-1 and 0.258C (10 yr)-1, respectively. The decadal variation shows that the temperature in the moderate warm interval of the 1910s-1930s was notably lower than that of the 1980s-2000s, which suggests that the warming since the 1980s was unprecedented for the past 160 years, though a warming hiatus existed in the 2000s. Additionally, there was a rapid cooling starting from the 1860s, followed by a cold interval until the early 1890s, with the coldest years in 1892 and 1893. A slight temperature decline was also found from the 1940s to the late 1960s. This study provides an independent case to validate the global warming for the past 160 years and its hiatus recently, because the proxy data are not affected by urbanization.
Using the southern limit of snowfall recorded in Chinese documents, chronologies of tree-ring width, and tree-ring stable oxygen isotope (\(\updelta^{18}\)O), the annual temperature anomaly in southern China during 1850-2009 is reconstructed using the method of signal decomposition and synthesis. The results show that the linear trend was 0.47C (100 yr)-1 over 1871-2009, and the two most rapid warming intervals occurred in 1877-1938 and 1968-2007, at rates of 0.125C (10 yr)-1 and 0.258C (10 yr)-1, respectively. The decadal variation shows that the temperature in the moderate warm interval of the 1910s-1930s was notably lower than that of the 1980s-2000s, which suggests that the warming since the 1980s was unprecedented for the past 160 years, though a warming hiatus existed in the 2000s. Additionally, there was a rapid cooling starting from the 1860s, followed by a cold interval until the early 1890s, with the coldest years in 1892 and 1893. A slight temperature decline was also found from the 1940s to the late 1960s. This study provides an independent case to validate the global warming for the past 160 years and its hiatus recently, because the proxy data are not affected by urbanization.
2017, 34(8): 983-992.
doi: 10.1007/s00376-017-6242-z
Abstract:
To investigate the potential effects of aerosols on the microphysical properties of warm clouds, airborne observational data collected from 2009 to 2011 in Tongliao, Inner Mongolia, China, were statistically analyzed in this study. The results demonstrated that the vertical distribution of the aerosol number concentration (N a) was similar to that of the clean rural continent. The average aerosol effective diameter (D e) was maintained at approximately 0.4 μm at all levels. The data obtained during cloud penetrations showed that there was a progressive increase in the cloud droplet concentration (N c) and liquid water content (LWC) from outside to inside the clouds, while the N a was negatively related to the N c and LWC at the same height. The fluctuation of the N a, N c and LWC during cloud penetration was more obvious under polluted conditions (Type 1) than under clean conditions (Type 2). Moreover, the wet scavenging of cloud droplets had a significant impact on the accumulation mode of aerosols, especially on particles with diameters less than 0.4 μm. The minimum wet scavenging coefficient within the cloud was close to 0.02 under Type 1 conditions, while it increased to 0.1 under Type 2 conditions, which proved that the cloud wet scavenging effect under Type 1 conditions was stronger than that under Type 2 conditions. Additionally, cloud droplet spectra under Type 1 conditions were narrower, and their horizontal distributions were more homogeneous than those under Type 2 conditions.
To investigate the potential effects of aerosols on the microphysical properties of warm clouds, airborne observational data collected from 2009 to 2011 in Tongliao, Inner Mongolia, China, were statistically analyzed in this study. The results demonstrated that the vertical distribution of the aerosol number concentration (N a) was similar to that of the clean rural continent. The average aerosol effective diameter (D e) was maintained at approximately 0.4 μm at all levels. The data obtained during cloud penetrations showed that there was a progressive increase in the cloud droplet concentration (N c) and liquid water content (LWC) from outside to inside the clouds, while the N a was negatively related to the N c and LWC at the same height. The fluctuation of the N a, N c and LWC during cloud penetration was more obvious under polluted conditions (Type 1) than under clean conditions (Type 2). Moreover, the wet scavenging of cloud droplets had a significant impact on the accumulation mode of aerosols, especially on particles with diameters less than 0.4 μm. The minimum wet scavenging coefficient within the cloud was close to 0.02 under Type 1 conditions, while it increased to 0.1 under Type 2 conditions, which proved that the cloud wet scavenging effect under Type 1 conditions was stronger than that under Type 2 conditions. Additionally, cloud droplet spectra under Type 1 conditions were narrower, and their horizontal distributions were more homogeneous than those under Type 2 conditions.
2017, 34(8): 993-1002.
doi: 10.1007/s00376-016-6217-5
Abstract:
The quality of the MODIS C6 3-km and 10-km aerosol optical depth (AOD) products retrieved by the Dark Target (DT) method is discussed using ground-based observations in the Beijing-Tianjin-Hebei region from 1 August 2007 to 31 July 2008. Good consistency exists between the 3-km and 10-km products and ground-based observations. The retrieval accuracy of the two products both show distinctive seasonality. The percentage falling within the expected error (EE) is largest in the winter, moderate in the spring and autumn, and smallest in the summer. A worse overestimation appears in the spring and summer (27%-66%). However, the 3-km and 10-km products over different surfaces still exhibit obvious deviations. The 10-km product performs better in the large cities, while the 3-km product has advantages in the suburbs. In urban areas, the percentage falling within EE of the 3-km AOD product (18%-59%) is lower than that for the 10-km AOD product (31%-69%). However, in suburban areas, the percentage falling within EE of the 3-km AOD product (61%-84%) is higher than for the 10 km AOD product (54%-83%).The percentages falling within EE differ considerably when the AOD is greater than 1.5 (73% and 63% for the 3-km and 10-km products, respectively). On the whole, the 3-km (10-km) AOD product performs better in suburban (urban) areas.
The quality of the MODIS C6 3-km and 10-km aerosol optical depth (AOD) products retrieved by the Dark Target (DT) method is discussed using ground-based observations in the Beijing-Tianjin-Hebei region from 1 August 2007 to 31 July 2008. Good consistency exists between the 3-km and 10-km products and ground-based observations. The retrieval accuracy of the two products both show distinctive seasonality. The percentage falling within the expected error (EE) is largest in the winter, moderate in the spring and autumn, and smallest in the summer. A worse overestimation appears in the spring and summer (27%-66%). However, the 3-km and 10-km products over different surfaces still exhibit obvious deviations. The 10-km product performs better in the large cities, while the 3-km product has advantages in the suburbs. In urban areas, the percentage falling within EE of the 3-km AOD product (18%-59%) is lower than that for the 10-km AOD product (31%-69%). However, in suburban areas, the percentage falling within EE of the 3-km AOD product (61%-84%) is higher than for the 10 km AOD product (54%-83%).The percentages falling within EE differ considerably when the AOD is greater than 1.5 (73% and 63% for the 3-km and 10-km products, respectively). On the whole, the 3-km (10-km) AOD product performs better in suburban (urban) areas.
2017, 34(8): 1003-1016.
doi: 10.1007/s00376-017-6219-y
Abstract:
A set of vertical profiles of aerosol number concentrations, size distributions and cloud condensation nuclei (CCN) spectra was observed using a passive cloud and aerosol spectrometer (PCASP) and cloud condensation nuclei counter, over the Tongliao area, East Inner Mongolia, China. The results showed that the average aerosol number concentration in this region was much lower than that in heavily polluted areas. Monthly average aerosol number concentrations within the boundary layer reached a maximum in May and a minimum in September, and the variations in CCN number concentrations at different supersaturations showed the same trend. The parameters c and k of the empirical function N=cSk were 539 and 1.477 under clean conditions, and their counterparts under polluted conditions were 1615 and 1.42. Measurements from the airborne probe mounted on a Yun-12 (Y12) aircraft, together with Hybrid Single-Particle Lagrangian Integrated Trajectory model backward trajectories indicated that the air mass from the south of Tongliao contained a high concentration of aerosol particles (1000-2500 cm-3) in the middle and lower parts of the troposphere. Moreover, detailed intercomparison of data obtained on two days in 2010 indicated that the activation efficiency in terms of the ratio of N CCN to N a (aerosols measured from PCASP) was 0.74 (0.4 supersaturations) when the air mass mainly came from south of Tongliao, and this value increased to 0.83 on the relatively cleaner day. Thus, long-range transport of anthropogenic pollutants from heavily polluted mega cities, such as Beijing and Tianjin, may result in slightly decreasing activation efficiencies.
A set of vertical profiles of aerosol number concentrations, size distributions and cloud condensation nuclei (CCN) spectra was observed using a passive cloud and aerosol spectrometer (PCASP) and cloud condensation nuclei counter, over the Tongliao area, East Inner Mongolia, China. The results showed that the average aerosol number concentration in this region was much lower than that in heavily polluted areas. Monthly average aerosol number concentrations within the boundary layer reached a maximum in May and a minimum in September, and the variations in CCN number concentrations at different supersaturations showed the same trend. The parameters c and k of the empirical function N=cSk were 539 and 1.477 under clean conditions, and their counterparts under polluted conditions were 1615 and 1.42. Measurements from the airborne probe mounted on a Yun-12 (Y12) aircraft, together with Hybrid Single-Particle Lagrangian Integrated Trajectory model backward trajectories indicated that the air mass from the south of Tongliao contained a high concentration of aerosol particles (1000-2500 cm-3) in the middle and lower parts of the troposphere. Moreover, detailed intercomparison of data obtained on two days in 2010 indicated that the activation efficiency in terms of the ratio of N CCN to N a (aerosols measured from PCASP) was 0.74 (0.4 supersaturations) when the air mass mainly came from south of Tongliao, and this value increased to 0.83 on the relatively cleaner day. Thus, long-range transport of anthropogenic pollutants from heavily polluted mega cities, such as Beijing and Tianjin, may result in slightly decreasing activation efficiencies.
2017, 34(8): 1017-1026.
doi: 10.1007/s00376-016-6224-6
Abstract:
Aerosol observational data for 2012 obtained from Dunhuang Station of CARE-China (Campaign on Atmospheric Aerosol Research Network of China) were analyzed to achieve in-depth knowledge of aerosol optical properties over Dunhuang region. The results showed that the annual average aerosol optical depth (AOD) at 500 nm was 0.32 0.06, and the ngstrm exponent () was 0.73 0.27. Aerosol optical properties revealed significant seasonal characteristics. Frequent sandstorms in MAM (March-April-May) resulted in the seasonal maximum AOD, 0.41 0.04, and a relatively smaller value, 0.44 0.04. The tourism seasons, JJA (June-July-August) and SON (September-October-November) coincide with serious emissions of small anthropogenic aerosols. While in DJF (December-January-February), the composition of the atmosphere was a mixture of dust particles and polluted aerosols released by domestic heating; the average AOD and were 0.29 0.02 and 0.66 0.17, respectively. Different air masses exhibited different degrees of influence on the aerosol concentration over Dunhuang in different seasons. During MAM, ranges of AOD (0.11-1.18) and (0.06-0.82) were the largest under the dust influence of northwest-short-distance air mass in the four trajectories. Urban aerosols transported by northwest-short-distance air mass accounted for a very large proportion in JJA and the mixed aerosols observed in SON were mainly conveyed by air masses from the west. In DJF, the similar ranges of AOD and under the three air mass demonstrated the analogous diffusion effects on regional pollutants over Dunhuang.
Aerosol observational data for 2012 obtained from Dunhuang Station of CARE-China (Campaign on Atmospheric Aerosol Research Network of China) were analyzed to achieve in-depth knowledge of aerosol optical properties over Dunhuang region. The results showed that the annual average aerosol optical depth (AOD) at 500 nm was 0.32 0.06, and the ngstrm exponent () was 0.73 0.27. Aerosol optical properties revealed significant seasonal characteristics. Frequent sandstorms in MAM (March-April-May) resulted in the seasonal maximum AOD, 0.41 0.04, and a relatively smaller value, 0.44 0.04. The tourism seasons, JJA (June-July-August) and SON (September-October-November) coincide with serious emissions of small anthropogenic aerosols. While in DJF (December-January-February), the composition of the atmosphere was a mixture of dust particles and polluted aerosols released by domestic heating; the average AOD and were 0.29 0.02 and 0.66 0.17, respectively. Different air masses exhibited different degrees of influence on the aerosol concentration over Dunhuang in different seasons. During MAM, ranges of AOD (0.11-1.18) and (0.06-0.82) were the largest under the dust influence of northwest-short-distance air mass in the four trajectories. Urban aerosols transported by northwest-short-distance air mass accounted for a very large proportion in JJA and the mixed aerosols observed in SON were mainly conveyed by air masses from the west. In DJF, the similar ranges of AOD and under the three air mass demonstrated the analogous diffusion effects on regional pollutants over Dunhuang.
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