The Chinese aerosol optical monitoring network

Transcription

1 Seasonal variations in aerosol optical properties over China and Validation of MODIS aerosol products Jinyuan Xin, Yuesi Wang, Lili Wang Z. Li, Pucai Wang, et al. Institute of Atmospheric Physics Chinese Academy of Sciences

2 The Chinese aerosol optical monitoring network The Chinese Sun Hazemeter Network CERN station (9) Hailun Typical city site (4) Sanjiang Calibration site () Changbai Mountain Fukang Beijing City Shenyang Eerduosi Xianghe Beijing Forest Shapotou Haibei Lanzhou City Ansai Fengqiu Jiaozhou bay It s the first background network through the wide Chinese region. Lhasa Shanghai City Tai lake Yanting Taoyuan Based on the Chinese Ecosystem Research Network Sanya Taipei City Dinghu Mountain Xishuangbanna Observe regional aerosol optical properties; Validate satellite aerosol retrieval results; Validate aerosol radiation transfer models. Sanya LED hazemeter CEMIL AERONET

3 Calibration at Lhasa and Comparison of CEMIL. 5.5 At the Beijing site 45nm y=.53x-.437 (R =.98) LED hazemeter.langley plot.comparison 3.Transport CIM MEL's AOD..5 y=x (a) 5nm y=.996x-.9 (R =.983) ID4 hazemeter'saod Data from Aug to Dec 4 at Beijing site At the Xianghe site 65nm y=.977x-.84 (R =.94) s AOD CIMEL'..5 y=x (d) CEMIL 88nm y=.88x-.33 (R =.96) ID5 hazemeter's AOD Data from Feb to Aug 5 at Xianghe site

4 Some results and some beautiful prospects Seasonal variations in aerosol optical properties over China

5 Monitoring at Northeastern China Sanjiang Changbai Mountain (a marsh/farmland ecosystem) (a temperate forest ecosystem) Hailun (a farmland ecosystem in the Songnen Plain) Shenyang (a suburban farmland ecosystem)

6 .5. Changbai Mt. Hailun Sanjiang Shenyang 3 V max <5m/s V max 5-m/s V max >m/s Northeastern China Representatives =5nm AOD.5 Small er Larg ger Year Changbai Mt. Hailun Sanjiang Shenyang Year AOD( 5nm ) Figures show a marked seasonal cycle in the monthly-averaged AOD at 5 nm and the monthly-averaged Angstrom exponent (α) from August 4 to August 7 in northeast China. Remote sites, such as Sanjiang, Hailun and Changbai Mt., have clean air so the annual mean AOD is low and ranges from.8 to.; the annual mean α ranges from.7 to.96 at these sites.

7 Sma ller 3 The mean and T for the -interval T AOD <. AOD:.-.5 AOD >.5 Northeastern China The mean AOD and RH for the -interval RH <.5 :.5-.5 >.5 Northeastern China Hygroscopicity AOD( 5nm ) La arger Biomass burning T ( ) Relative Humidity RH α increases with T decreasing, the scatterplot reflects the agricultural practice of burning crop stalks in autumn and the increase in fossil fuel and biomass burning for heating as winter approaches. Meanwhile, a gradual increase in snow and ice cover on the ground prevents soil erosion and thus restricts the emission of coarsemode mineral particles. In spring and summer, AOD increasing with α decreasing, the aerosols seem to be more of a continental type due to regional dust transmission and local soil emission. The scatterplot of AOD as a function of RH illustrates that continental aerosols (.5<α<.5) α are hygroscopic in nature and that small smoke aerosols (α>.5) and large dust aerosols (α<.5) are water-insoluble.

8 Monitoring at the arid region of north China Fukang (an oasis ecosystem in the transition zone from Tianshan Mountain to Gurbantunggut Desert) Ordos (a sandy grassland ecosystem in the temperate semi-arid grassland zone) Shapotou (a desert ecosystem in the arid region of northern China) Ansai (an agricultural ecosystem in the Loess Plateau)

9 .5. Fukang Shapotou Ordos Ansai 3 V max <5m/s V max 5-m/s V max >m/s North desert Representatives =5nm AOD Year 6 7 AOD( 5nm ) Small er Larg ger Fukang Shapotou Ordos Ansai 5 Year 6 7 The annual mean AOD and α show similar seasonal variations and range from.7 to.37 and from.47 to.96, respectively. AODs and atmospheric turbidity are larger over the desert (Sapotou) and arid agricultural (Ansai) sites than at the two other sites. Because the sole source of aerosols in the more desert-like region is natural dust emission, dust aerosols are more persistent at the Shapotou site.

10 Sma ller 3 The mean and T for the -interval T AOD <. AOD:.-.5 AOD >.5 North desert The mean AOD and RH for the -interval RH <.5 :.5-.5 >.5 North desert Hygroscopicity AOD( 5nm ) La arger Biomass burning T ( ) Relative Humidity RH Aerosol particles are generally bigger than when Vmax< m/s, which implies that powerful winds blow local large dust particles into the atmosphere during the springtime in northern China. The scatterplot shows that α increases as T decreases when AOD<.5, which indicates the background presence of smoke aerosols in autumn and winter due to biomass burning by the local farmers. For RH>6%, the scatterplot of AOD as a function of RH shows the hygroscopicity of continental aerosols (.5<α<.5) in these areas.

11 Monitoring at Tibet Plateau Hibi( Haibei (an alpine li meadow ecosystem) on Lhasa (an alpine shrub-grassland the Tibetan Plateau ecosystem) on the Tibet Plateau

12 .5 Lhasa Haibei 3 V max <5m/s V max 5-m/s V max >m/s. Haibei Representatives =5nm AOD.5 Lhasa. 4 5 Year 6 7 AOD( 5nm ) Small er Larg ger Lhasa Haibei Year 6 7 The annual mean AOD is.3±.5 and.5±.4 at the Haibei and Lhasa sites, respectively; the annual mean α is.8±.5 and -.5±.5, respectively. Both sites have very clean air with low and stable AODs throughout the year, although the windy springtime weather can cause a mild increase in AOD.

13 Sma ller 3 The mean and T for the -interval T AOD <. AOD:.-.5 AOD >.5 Haibei AOD( 5nm ) The mean AOD and RH for the -interval RH <.5 :.5-.5 >.5 Tibet Plateau Hygroscopicity La arger Biomass burning Lhasa T ( ) Relative Humidity RH At Haibei, there is an increase in small aerosol particles during the long winter due to regional biomass burning. However, frequent cold air surges from Siberia i often bring clean air into the region, which washes away pollutants and causes the large day-to-day variations in α. At Lhasa, without significant anthropogenic impact and pollution emission, large continental/dust aerosol particles are simplex aerosol type. Because of the very narrow range of AOD, the scatterplot of AOD as afunction of RH cannot describe the hygroscopicity y of aerosol particles.

14 Monitoring at the forest ecosystems Beijing Forest (a warm temperate forest ecosystem to the west of Beijing City) Dinghu Mountain (a subtropical evergreen forest ecosystem at the Pearl River Delta) Xishuangbanna (a tropical rainforest ecosystem in Yunnan Province)

15 .5 Beijing Forest Dinghu Mt. Xishuangbanna 3 V max <5m/s V max 5-m/s V max >m/s Beijing Forest Representatives =5nm AOD..5 3 AOD( 5nm ) V max <5m/s V max 5-m/s V max >m/s Dinghu Mt. & Xishuangbanna Small er Larg ger Year Beijing Forest Dinghu Mt. Xishuangbanna Year AOD( 5nm ) At Beijing Forest, the seasonal variations of AOD and α are similar to the other sites in northern China. At Dinghu Mt., The relatively high aerosol loading is the result of the rapid development of regional industrialization. AODs decrease with northwesterly winds in winter and southeasterly winds in summer. At Xishuangbanna, anomalous seasonal variations in AOD and more smoke aerosol type.

16 Sma ller 3 The mean and T for the -interval T AOD <. AOD:.-.5 AOD >.5 Beijing forest South forests The mean AOD and RH for the -interval RH <.5 :.5-.5 >.5 Forests Hygroscopicity AOD( 5nm ) La arger Biomass burning T ( ) Relative Humidity RH At Beijing forest, in autumn and winter, fossil fuel and biomass burning generate smoke and soot aerosols, which reduces the size of the dominant aerosol particles. In spring and summer, dust storm transportation and local soil dust emission increase both AOD and the size of dominant aerosol particles..5<α<.5, the hygroscopicity of continental aerosols. At Dinghu Mt., Southeasterly winds blow in large sea salt particles, resulting in a decrease in α in summer. aerosols are hygroscopic in this region. At Xishuangbanna, dense foggy weather frequently occurs in the region, especially in autumn and winter. During the rainy season from May to October, a large amount of aerosol is removed from the atmosphere which h reduces AOD. During the dry spring season, AOD and α are at ttheir highest, which implies large emissions of smoke and soot due to biomass burning which is most active in the whole of southeast Asia.

17 Monitoring at the farmland ecosystems Fengqiu (a farmland ecosystem on the Huang-huai-hai hai Plain) Taoyuan (a subtropical farmland ecosystem) Yanting g( (a farmland ecosystem in the hilly region of the Sichuan Basin)

18 .5. Fengqiu Taoyuan Yanting 3 V max <5m/s V max 5-m/s V max >m/s Farmlands Representatives =5nm AOD Year 6 7 AOD( 5nm ) Small er Larg ger Fengqiu Taoyuan Yanting 5 Year 6 7 AODs at these locations are much higher than in more remote areas because of agricultural and industrial development and human activities in this part of China. The annual mean α is approximately equal to with a little standard deviation (~.6).

19 Sma ller 3 The mean and T for the -interval T AOD <. AOD:.-.5 AOD >.5 Farmlands The mean AOD and RH for the -interval RH <.5 :.5-.5 >.5 Farmlands Hygroscopicity AOD( 5nm ) La arger Biomass burning T ( ) Relative Humidity RH The regional government has advocated and reinforced a policy for comprehensive utilization of crop stalks, so that smoke aerosol emissions from biomass burning is minimized. More mineral dust aerosols and anthropogenic sulphate aerosols are emitted in eastern China, southern China and the Sichuan Basin, due to intensive farming and industrial activities and the exposure of bare soil. In winter and spring, weather patterns instigating serious pollution events usually occur in Hunan Province and over the Sichuan Basin. The scatterplot shows that AODs increase with increasing RH, implying thatt the abundant anthropogenicsulphate lht and soil aerosols in the region are hygroscopic.

20 Monitoring at the bay and lake Jiaozhou Bay (a marine ecosystem on the west coast of the Yellow Sea) Lake Tai (a freshwater lake ecosystem at the Yangtze River Delta) Sanya Bay (a tropical marine ecosystem in the South China Sea)

21 .5. Jiaozhou Bay Tai Lake Sanya Bay 3 V max <5m/s V max 5-m/s V max >m/s Bays and lake Representatives =5nm AOD Year 6 7 AOD( 5nm ) Small er Jiaozhou Bay Tai Lake Sanya Bay The annual mean AOD &α: Jiaozhou Bay:.64±.3 &.6±.9, pollution.5..5 Tai Lake:.45±.9 &.8±.4, pollution Larg ger Year 6 7 Sanya Bay:.3±. &.39±.38, clean day

22 Sma ller 3 The mean and T for the -interval T AOD <. AOD:.-.5 AOD >.5 Bays and lake The mean AOD and RH for the -interval RH <.5 :.5-.5 >.5 Bays and lake Hygroscopicity AOD( 5nm ) La arger Biomass burning T ( ) Relative Humidity RH At Jiaozhou Bay, AODs are high because rapid industrial development and human activities increase aerosol emissions, especially sulphate aerosols along the eastern coastal area and northern China. Dust and continental pollution transport from spring to summer contribute to large AOD. Aerosol pollution is also strong at Tai Lake because the region is dotted with thousands of small privately-owned factories emitting huge amounts of pollutants Sanya Bay is very clean and large sea salt particles dominate. In spring, the transition period from the monsoon season, some aerosols originate from Hainan Island so that AOD and α rise. The scatterplot of AOD as a function of RH (α<.5) indicates that aerosols along the east/south coast are hygroscopic in nature.

23 Similar monthly and seasonal variations of AODs and aerosol types In spring In summer Dust Vapor Smoke In autumn Smoke In winter Smoke Smoke Smoke Smoke

24 The annual mean of AOD and aerosol types ( ) 7.7) Annual mean AOD <.5 Angstrom exponent.5 AOD >.5 Angstrom exponent The annual mean AOD at 5 nm central/eastern, southern and eastern mean value over the relatively remote averaged over the active anthropogenic regions, e.g. the coastal areas, is.6, which is about 3 times the regional background dry or clean regions in China (mean AOD~.3, e.g. at the northeast (smoke), the north desert (dust), Tibet Plateau (dust), Hainan Inland (sea salt). Furthermore, biomass burning which is most active in the wholeof hl southeast t Ai Asia.

25 The correlation between annual AOD changes and annual temperature changes, precipitation changes Tempera t ature changes changes AOD changes Precipita rainf ation fall changes s AOD changes Figures show that there is a negative correlation between AOD and temperature changes, while a positive correlation between AOD and precipitation changes. With AOD or aerosol emission increasing, temperature will decrease and precipitation will increase in most parts of China. And the climate effect of aerosol is significant.

26 Compare MODIS aerosol products with the network results over China over one-hour interval over 5 km area Comparison Ground-base observation MODIS remote sensing The Chinese Sun Hazemeter Network Point Fukang CERN station (9) Hailun Typical city site (4) Sanjiang Calibration site () Changbai Mountain Beijing City Shenyang Eerduosi Xianghe Beijing Forest Shapotou Haibei Jiaozhou bay Lanzhou City Ansai Fengqiu Area Lhasa Yanting Taoyuan Shanghai City Tai lake Sanya Dinghu Mountain Taipei City Xishuangbanna Sanya

27 Compare MODIS C4 aerosol products with the network results over China (the manual mean) Available data: 6% Within NASA error: 5% Overestimate: % Valuation of MODIS Products with CSHNET Ground-base observation R: Ratio of MODIS to Site's Result R: Percentage within NASA Error MODIS remote sensing

28 Compare MODIS C5 aerosol products with the network results over China (the manual mean) Available data: 45% Within NASA error: 6% Underestimate: 5% MODIS remote sensing Valuation of MODIS Products with CSHNET From Aug 4 to Jul 7 R: Ratio of MODIS to Site's Result R: Percentage within NASA Error Ground-base observation

29 Compare MODIS products with the network results Due to extensive terrain, complex surface, diverse ecological types and aerosol models, MODIS aerosol products have a lack of applicability and generally over (C4) or under (C5) estimate AOD over China. As far as MODIS product errors are concerned, south less north, east less west, vegetation ti less novegetation, and growing season less non-growing season. Currently, before MODIS product can be applied widely in China, it is necessary to systematically ti correct satellite retrieval process using the ground- based observation and develop new algorithms according to different surfaces and aerosol types.

30 The sun hazemeter network established by IAP-CAS at Beijing and its ambient area The new network was established db by IAP-CAS, including 6 CERN stations and 7 urban sites. The network is monitoring aerosol properties and particle pollution at Beijing and its ambient area.

31 The distribution of the annual AOD and aerosol types at Beijing and its ambient area The mean AOD The mean Angstrom Exponent Angstrom exponent The aerosol concentration i is i high i at the great region, the annual back back-ground ground AOD is about.3,.58 at Beijing,.69 at the ambient area area. The annual back-ground Angstrom g exponent p is about.95,.4 at Beijing,.3 at the ambient area area. The fine particles is relative high at Beijing.

32 A technology of monitoring aerosol & particles at the great area of Beijing For the workshop! The high resolution distribution of AOD and PM.5 at the region Ae Mixin erosol typ ng layer h pes height Control Factors Establish a model between AOD and MODIS-AOD, PM.5 Control Factors Relat Su tive humi rface typ idity pes Compare the network AOD with PM.5 and MODIS-AOD The hazemeter AOD network The PM.5 network MODIS AOD product

33 Some references about the network results Seasonal variations in aerosol optical properties over China, ACPD, 8. Photometric measurements of spring aerosol optical properties in dust and non-dust periods in China, Atmospheric Environment, 8. 3 Aerosol optical depth over the Tibetan Plateau and its relation to aerosols over the Taklimakan Desert, JGRL, 7. 4 Aerosol Single Scattering Albedo Estimated across China from a Combination of Ground and Satellite Measurements. JGR, 7. 5 Validation and Understanding of MODIS Aerosol Products Using Groundbased Measurements from the Handheld Sunphotometer Network in China. JGR, 7. 6 Evaluation of the MODIS aerosol optical depth retrieval over different ecosystems in China during EAST-AIRE. Atmospheric Environment, 7. 7 Validation of MODIS aerosol products by CSHNET over China. Chinese Science Bulletin, 7. 8 Aerosol optical depth (AOD) and Angstrom exponent of aerosols observed by the Chinese Sun Hazemeter Network from August 4 to September 5. JGR, 7. 9 Optical properties and size distribution ib ti of dust aerosols over the Tengger Desert in Northern China. Atmospheric Environment, 5. Observation and simulation of aerosol optical properties affected by a strong dust storm in Central and Northern China, AAS, 9. And several Chinese papers.

34 Seasonal variations in aerosol optical properties over China and Validation of MODIS aerosol products Thank you for your attention Jinyuan Xin, Yuesi Wang, Lili Wang Z. Li, Pucai Wang, et al. Institute of Atmospheric Physics Chinese Academy of Sciences