Chinese blue days: a novel index and spatio-temporal variations
As part of the Blue-Sky Protection Campaign, we develop the Chinese Blue Days Index based on meteorology data from 385 stations in China during 1980–2014. This index is defined as the days with no rain, low cloud cover ≤75th percentile, and visibility ≥15 km at 2 pm. The spatio-temporal variations a...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2019-01-01
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| Series: | Environmental Research Letters |
| Subjects: | |
| Online Access: | https://doi.org/10.1088/1748-9326/ab29bb |
| _version_ | 1827870540370542592 |
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| author | Su Wang Gang Huang Jintai Lin Kaiming Hu Lin Wang Hainan Gong |
| author_facet | Su Wang Gang Huang Jintai Lin Kaiming Hu Lin Wang Hainan Gong |
| author_sort | Su Wang |
| collection | DOAJ |
| description | As part of the Blue-Sky Protection Campaign, we develop the Chinese Blue Days Index based on meteorology data from 385 stations in China during 1980–2014. This index is defined as the days with no rain, low cloud cover ≤75th percentile, and visibility ≥15 km at 2 pm. The spatio-temporal variations and possible driving factors of Chinese Blue Days (CBD) are further investigated, revealing a steadily rising rate of 1.6 day (d)/10 year (y) for the nationally averaged CBD during 1980–2014. At regional scales, the CBD exhibit an increasing trend >4 d/10 y in western China and a decreasing trend <−2 d/10 y in southeastern China, northwestern Xinjiang, and Qinghai. The minimum/maximum trends (−7.5/9.5 d/10 y) appear in Yangtze–Huai River Valley (YHRV)/southwestern China (SWC). The interannual variations in CBD are highly related to wind speed and windless days in YHRV but are closely associated with wind speed, rainless days and relative humidity in SWC, suggesting that the two regions are governed by different meteorological factors. Moreover, a dynamic adjustment method called partial least squares is used to remove the atmospheric circulation-related CBD trend. The residual CBD contributions for the total trend in summer and winter are 43.62% and 35.84% in YHRV and are 14.25% and 60.38% in SWC. The result indicates that considerable parts of the CBD trend are due to the change of atmospheric circulation in the two regions. |
| first_indexed | 2024-03-12T15:58:15Z |
| format | Article |
| id | doaj.art-064bff3899ea436e9ff0d77c8e23bf2b |
| institution | Directory Open Access Journal |
| issn | 1748-9326 |
| language | English |
| last_indexed | 2024-03-12T15:58:15Z |
| publishDate | 2019-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | Environmental Research Letters |
| spelling | doaj.art-064bff3899ea436e9ff0d77c8e23bf2b2023-08-09T14:44:22ZengIOP PublishingEnvironmental Research Letters1748-93262019-01-0114707402610.1088/1748-9326/ab29bbChinese blue days: a novel index and spatio-temporal variationsSu Wang0Gang Huang1https://orcid.org/0000-0002-8692-7856Jintai Lin2Kaiming Hu3https://orcid.org/0000-0002-9988-5747Lin Wang4Hainan Gong5State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, People’s Republic of China; University of Chinese Academy of Sciences , Beijing 100049, People’s Republic of ChinaState Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, People’s Republic of China; University of Chinese Academy of Sciences , Beijing 100049, People’s Republic of China; Laboratory for Regional Oceanography and Numerical Modeling, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, People’s Republic of China; Joint Center for Global Change Studies (JCGCS), Beijing 100875, People’s Republic of ChinaLaboratory for Climate and Ocean-Atmosphere Studies, Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University , Beijing, 100871, People’s Republic of ChinaState Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, People’s Republic of China; Center for Monsoon System Research, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, People’s Republic of ChinaKey Laboratory of Regional Climate-Environment for Temperate East Asia, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, People’s Republic of ChinaState Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, People’s Republic of China; Center for Monsoon System Research, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, People’s Republic of ChinaAs part of the Blue-Sky Protection Campaign, we develop the Chinese Blue Days Index based on meteorology data from 385 stations in China during 1980–2014. This index is defined as the days with no rain, low cloud cover ≤75th percentile, and visibility ≥15 km at 2 pm. The spatio-temporal variations and possible driving factors of Chinese Blue Days (CBD) are further investigated, revealing a steadily rising rate of 1.6 day (d)/10 year (y) for the nationally averaged CBD during 1980–2014. At regional scales, the CBD exhibit an increasing trend >4 d/10 y in western China and a decreasing trend <−2 d/10 y in southeastern China, northwestern Xinjiang, and Qinghai. The minimum/maximum trends (−7.5/9.5 d/10 y) appear in Yangtze–Huai River Valley (YHRV)/southwestern China (SWC). The interannual variations in CBD are highly related to wind speed and windless days in YHRV but are closely associated with wind speed, rainless days and relative humidity in SWC, suggesting that the two regions are governed by different meteorological factors. Moreover, a dynamic adjustment method called partial least squares is used to remove the atmospheric circulation-related CBD trend. The residual CBD contributions for the total trend in summer and winter are 43.62% and 35.84% in YHRV and are 14.25% and 60.38% in SWC. The result indicates that considerable parts of the CBD trend are due to the change of atmospheric circulation in the two regions.https://doi.org/10.1088/1748-9326/ab29bbpartial least squaressouthwest ChinaChinese Blue Days IndexYangtze–Huai river valley |
| spellingShingle | Su Wang Gang Huang Jintai Lin Kaiming Hu Lin Wang Hainan Gong Chinese blue days: a novel index and spatio-temporal variations Environmental Research Letters partial least squares southwest China Chinese Blue Days Index Yangtze–Huai river valley |
| title | Chinese blue days: a novel index and spatio-temporal variations |
| title_full | Chinese blue days: a novel index and spatio-temporal variations |
| title_fullStr | Chinese blue days: a novel index and spatio-temporal variations |
| title_full_unstemmed | Chinese blue days: a novel index and spatio-temporal variations |
| title_short | Chinese blue days: a novel index and spatio-temporal variations |
| title_sort | chinese blue days a novel index and spatio temporal variations |
| topic | partial least squares southwest China Chinese Blue Days Index Yangtze–Huai river valley |
| url | https://doi.org/10.1088/1748-9326/ab29bb |
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