Southeast China has comparable stratus cloud to that over the oceans,especially in the cold seasons(winter and spring),and this cloud has a substantial impact on energy and hydrological cycles.However,uncertainties re...Southeast China has comparable stratus cloud to that over the oceans,especially in the cold seasons(winter and spring),and this cloud has a substantial impact on energy and hydrological cycles.However,uncertainties remain across datasets and simulation results about the long-term trend in low-cloud cover in Southeast China,making it difficult to understand climate change and related physical processes.In this study,multiple datasets and numerical simulations were applied to show that low-cloud cover in Southeast China has gone through two stages since 1980—specifically,a decline and then a rise,with the turning point around 2008.The regional moisture transport plays a crucial role in low-cloud cover changes in the cold seasons and is mainly affected by the Hadley Cell in winter and the Walker Circulation in spring,respectively.The moisture transport was not well simulated in CMIP6 climate models,leading to poor simulation of the low-cloud cover trend in these models.This study provides insights into further understanding the regional climate changes in Southeast China.展开更多
The present study investigates the interdecadal variability of seasonal mean surface solar radiation over Northwest China using station observations from 1961-2003. Spring and summer surface solar radiation over North...The present study investigates the interdecadal variability of seasonal mean surface solar radiation over Northwest China using station observations from 1961-2003. Spring and summer surface solar radiation over Northwest China was lower in the late 1970s through 1990s than in the 1960s through the mid-1970s, and fall and winter surface solar radiation displayed similar patterns. These results indicate that the decrease in spring and summer surface solar radiation may be associated with increased low-cloud cover over Northwest China. Rainfall anomalies were closely related to the low-cloud cover over Northwest China and with the Northern Hemisphere circumglobal teleconnection in spring, summer, and winter.展开更多
Coral reefs produce atmospheric dimethylsulfide (DMSa) which oxidises to non-sea-salt (nss) sulfate aerosols, precursors of cloud condensation nuclei (CCN) and low level cloud (LLC), reducing solar radiation and regul...Coral reefs produce atmospheric dimethylsulfide (DMSa) which oxidises to non-sea-salt (nss) sulfate aerosols, precursors of cloud condensation nuclei (CCN) and low level cloud (LLC), reducing solar radiation and regulating sea surface temperatures (SSTs). Here we report measurements of solar radiation, SST, LLC, DMS flux, , and rainfall before, during and after a major coral bleaching event at Magnetic Island in the central Great Barrier Reef (GBR). Measurements are compared with those made at the nearby fringing reef of Or-pheus Island where coral bleaching did not occur. Extreme solar radiation levels occurred from November to late January and could have reflected cloud radiative effects that increased downwelling of solar radiation. High levels of LLC often coincided with high periodic fluxes of DMS from the unbleached coral reef at Orpheus Island (e.g. 14 - 20 μmol·m-2·d-1), in direct contrast to the very low fluxes of DMS that were emitted from the bleached, human-impacted Magnetic Island fringing reef (nd-0.8 μmol·m-2·d-1) when SSTs were >30°C. Continuous SSTs measurements at the Magnetic Island reef revealed various heating and cooling periods, interspersed with stable SSTs. Cooling periods (negative climate feedback) ranged from -1°C to -3°C (7 day mean -1.6°C), and often seemed to occur during low tides, periodic pulses of DMS flux and LLC, keeping SSTs °C. In contrast warming periods of +1°C to +3°C (positive climate feedback, 7 day mean +1.52°C), seemed to occur during increasing tides, decreasing DMS flux and low to medium levels of LLC which increased solar radiation and caused SSTs over 30°C and corals to bleach. Alternation between these two states or types of feedback is indicated in this research and may be a function of enhanced scattering of solar radiation from nss-sulfate aerosols that originate from oxidation of DMSa produced from the coral reefs in the GBR. The net radiative forcing from clouds can be as high as four times as large as the radiative forcing from a doubling of 展开更多
基金This work was supported by the Ministry of Science and Technology of China[grant number 2017YFA0604002]the National Natural Science Foundation of China[grant numbers 41925023,41575073,41621005,and 91744208]the Collaborative Innovation Center of Climate Change,Jiangsu Province.
文摘Southeast China has comparable stratus cloud to that over the oceans,especially in the cold seasons(winter and spring),and this cloud has a substantial impact on energy and hydrological cycles.However,uncertainties remain across datasets and simulation results about the long-term trend in low-cloud cover in Southeast China,making it difficult to understand climate change and related physical processes.In this study,multiple datasets and numerical simulations were applied to show that low-cloud cover in Southeast China has gone through two stages since 1980—specifically,a decline and then a rise,with the turning point around 2008.The regional moisture transport plays a crucial role in low-cloud cover changes in the cold seasons and is mainly affected by the Hadley Cell in winter and the Walker Circulation in spring,respectively.The moisture transport was not well simulated in CMIP6 climate models,leading to poor simulation of the low-cloud cover trend in these models.This study provides insights into further understanding the regional climate changes in Southeast China.
基金supported by the Special Scientific Research Project for Public Interest(Grant No.GYHY201006021)the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No.KZCX2-EW-QN204)+1 种基金the National Basic Research Program of China(Grant No.2009CB421405)the National Natural Science Foundation of China(Grant Nos.40905027 and 40730952)
文摘The present study investigates the interdecadal variability of seasonal mean surface solar radiation over Northwest China using station observations from 1961-2003. Spring and summer surface solar radiation over Northwest China was lower in the late 1970s through 1990s than in the 1960s through the mid-1970s, and fall and winter surface solar radiation displayed similar patterns. These results indicate that the decrease in spring and summer surface solar radiation may be associated with increased low-cloud cover over Northwest China. Rainfall anomalies were closely related to the low-cloud cover over Northwest China and with the Northern Hemisphere circumglobal teleconnection in spring, summer, and winter.
文摘Coral reefs produce atmospheric dimethylsulfide (DMSa) which oxidises to non-sea-salt (nss) sulfate aerosols, precursors of cloud condensation nuclei (CCN) and low level cloud (LLC), reducing solar radiation and regulating sea surface temperatures (SSTs). Here we report measurements of solar radiation, SST, LLC, DMS flux, , and rainfall before, during and after a major coral bleaching event at Magnetic Island in the central Great Barrier Reef (GBR). Measurements are compared with those made at the nearby fringing reef of Or-pheus Island where coral bleaching did not occur. Extreme solar radiation levels occurred from November to late January and could have reflected cloud radiative effects that increased downwelling of solar radiation. High levels of LLC often coincided with high periodic fluxes of DMS from the unbleached coral reef at Orpheus Island (e.g. 14 - 20 μmol·m-2·d-1), in direct contrast to the very low fluxes of DMS that were emitted from the bleached, human-impacted Magnetic Island fringing reef (nd-0.8 μmol·m-2·d-1) when SSTs were >30°C. Continuous SSTs measurements at the Magnetic Island reef revealed various heating and cooling periods, interspersed with stable SSTs. Cooling periods (negative climate feedback) ranged from -1°C to -3°C (7 day mean -1.6°C), and often seemed to occur during low tides, periodic pulses of DMS flux and LLC, keeping SSTs °C. In contrast warming periods of +1°C to +3°C (positive climate feedback, 7 day mean +1.52°C), seemed to occur during increasing tides, decreasing DMS flux and low to medium levels of LLC which increased solar radiation and caused SSTs over 30°C and corals to bleach. Alternation between these two states or types of feedback is indicated in this research and may be a function of enhanced scattering of solar radiation from nss-sulfate aerosols that originate from oxidation of DMSa produced from the coral reefs in the GBR. The net radiative forcing from clouds can be as high as four times as large as the radiative forcing from a doubling of
