Trends in aerosol optical depth in northern China retrieved from sunshine duration data

Abstract. We present a 3-D climatology of the desert dust distribution over South and East Asia derived using CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) data. To distinguish desert dust from total aerosol load we apply a methodology developed in the framework of EARLINET (European Aerosol Research Lidar Network). The method involves the use of the particle linear depolarization ratio and updated lidar ratio values suitable for Asian dust, applied to multiyear CALIPSO observations (January 2007–December 2015). The resulting dust product provides information on the horizontal and vertical distribution of dust aerosols over South and East Asia along with the seasonal transition of dust transport pathways. Persistent high D_AOD (dust aerosol optical depth) values at 532 nm, of the order of 0.6, are present over the arid and semi-arid desert regions. Dust aerosol transport (range, height and intensity) is subject to high seasonality, with the highest values observed during spring for northern China (Taklimakan and Gobi deserts) and during summer over the Indian subcontinent (Thar Desert). Additionally, we decompose the CALIPSO AOD (aerosol optical depth) into dust and non-dust aerosol components to reveal the non-dust AOD over the highly industrialized and densely populated regions of South and East Asia, where the non-dust aerosols yield AOD values of the order of 0.5. Furthermore, the CALIPSO-based short-term AOD and D_AOD time series and trends between January 2007 and December 2015 are calculated over South and East Asia and over selected subregions. Positive trends are observed over northwest and east China and the Indian subcontinent, whereas over southeast China trends are mostly negative. The calculated AOD trends agree well with the trends derived from Aqua MODIS (Moderate Resolution Imaging Spectroradiometer), although significant differences are observed over specific regions.

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Decadal variations in retrieved aerosol optical depth from sunshine duration measurements over Europe since the late 19th century

10.5194/egusphere-egu2020-1351 ◽

2020 ◽

Author(s):

William Wandji ◽

Antti Lipponen ◽

Else van den Besselaar ◽

Arturo Sanchez–Lorenzo ◽

Martin Wild ◽

...

Keyword(s):

Aerosol Optical Depth ◽

Optical Depth ◽

Atmospheric Aerosols ◽

Sunshine Duration ◽

Volcanic Eruptions ◽

Accurate Estimation ◽

Historical Evolution ◽

Aerosol Forcing ◽

Physically Based ◽

Decadal Variations

A better knowledge of the present&#8211;day aerosol forcing requires an accurate estimation of the historical evolution of aerosol optical depth (AOD), which is also crucial to better understand the role played by atmospheric aerosols in the dimming/brightening phenomena that have occurred since the mid-20th century. A physically-based approach using daily sunshine duration and cloud cover measurements is applied over Europe for retrieving AOD (Wandji Nyamsi et al., 2019). Both European Climate Assessment & Dataset (ECA&D) and national meteorological offices/institutes provide suitable measurements, from ~ 1000 ground-based stations, to carry out our study.The retrieved long-term AOD shows reasonable seasonal and annual variabilities including signals induced by major volcanic eruptions. The trends of atmospheric aerosols and associated increase and decrease of AOD over the periods 1960&#8211;1984 and 1985&#8211;2010, respectively, are in good agreement with the dimming/brightening periods reported before. In addition, a more dominant decrease in AOD including high variability from the early-1900s to the 1950s is observed, which agrees with some earlier studies reporting &#8220;early brightening&#8221; for this period. The high inter-annual AOD variability during that period may be partly due to the transition from coal to gas in some European countries and also due to the possible influence of the Word Wars I & II.ReferencesWandji Nyamsi, W.; Lipponen, A.; Sanchez&#8211;Lorenzo, A.; Wild, M. and Arola, A. (2019), A hybrid method for reconstructing the historical evolution of aerosol optical depth from sunshine duration measurements, submitted.

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Reconstruction of long‐term aerosol optical depth series with sunshine duration records

Geophysical Research Letters ◽

10.1002/2015gl067543 ◽

2016 ◽

Vol 43 (3) ◽

pp. 1296-1305 ◽

Cited By ~ 13

Author(s):

A. Sanchez‐Romero ◽

A. Sanchez‐Lorenzo ◽

J. A. González ◽

J. Calbó

Keyword(s):

Aerosol Optical Depth ◽

Optical Depth ◽

Sunshine Duration

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Spatiotemporal characteristics of TOMS-based dust aerosol optical depth in northern China during 1978–2005

Earth Science Informatics ◽

10.1007/s12145-016-0277-z ◽

2016 ◽

Vol 10 (1) ◽

pp. 41-53 ◽

Cited By ~ 1

Author(s):

Xiaoyu Ren ◽

Yun Xie ◽

Guoyu Ren

Keyword(s):

Aerosol Optical Depth ◽

Optical Depth ◽

Northern China ◽

Dust Aerosol ◽

Spatiotemporal Characteristics

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Impacts of aerosol–radiation interaction on meteorological forecasts over northern China by offline coupling of the WRF-Chem-simulated aerosol optical depth into WRF: a case study during a heavy pollution event

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-12527-2020 ◽

2020 ◽

Vol 20 (21) ◽

pp. 12527-12547

Author(s):

Yang Yang ◽

Min Chen ◽

Xiujuan Zhao ◽

Dan Chen ◽

Shuiyong Fan ◽

...

Keyword(s):

Wind Speed ◽

Aerosol Optical Depth ◽

Optical Depth ◽

Meteorological Parameters ◽

Northern China ◽

Satellite Observations ◽

Surface Radiation ◽

Pollution Event ◽

Heavy Pollution

Abstract. To facilitate the future inclusion of aerosol–radiation interactions in the regional operational numerical weather prediction (NWP) system RMAPS-ST (adapted from Weather Research and Forecasting, WRF) at the Institute of Urban Meteorology (IUM), China Meteorological Administration (CMA), the impacts of aerosol–radiation interactions on the forecast of surface radiation and meteorological parameters during a heavy pollution event (6–10 December 2015) over northern China were investigated. The aerosol information was simulated by RMAPS-Chem (adapted from the WRF model coupled with Chemistry, WRF-Chem) and then offline-coupled into the Rapid Radiative Transfer Model for General Circulation Models (RRTMG) radiation scheme of WRF to enable the aerosol–radiation feedback in the forecast. To ensure the accuracy of the high-frequency (hourly) updated aerosol optical depth (AOD) field, the temporal and spatial variations of simulated AOD and aerosol extinction coefficient at 550 nm were evaluated against in situ and satellite observations. Comparisons with in situ and Moderate Resolution Imaging Spectroradiometer (MODIS), AErosol Robotic NETwork (AERONET), and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite observations showed that the model could reproduce the spatial and vertical distribution as well as the temporal variation of the polluted episode. Further comparison of PM2.5 with in situ observation showed WRF-Chem reasonably captured the PM2.5 field in terms of spatial distribution and magnitude, with the correlation coefficients of 0.85, 0.89, 0.76, 0.92 and 0.77 in Beijing, Shijiazhuang, Tianjin, Hebei and Henan, respectively. Forecasts with and without the aerosol information were conducted further, and the differences of surface radiation, energy budget and meteorological parameters were evaluated against surface and sounding observations. The offline-coupling simulation (with aerosol–radiation interaction active) showed a remarkable decrease in downward shortwave (SW) radiation reaching the surface, thus helping to reduce the overestimated SW radiation during the daytime. The simulated surface radiation budget was also improved, with the biases of net surface radiation decreased by 85.3 %, 50.0 %, 35.4 % and 44.1 % during the daytime in Beijing, Tianjin, Taiyuan and Jinan respectively, accompanied by the reduction of sensible (16.1 W m−2, 18.5 %) and latent (6.8 W m−2, 13.4 %) heat fluxes emitted by the surface around noon. In addition, the cooling of 2 m temperature (∼0.40 ∘C) and the decrease in horizontal wind speed near the surface (∼0.08 m s−1) caused by the aerosol–radiation interaction over northern China helped to reduce the bias by ∼73.9 % and ∼7.8 % respectively, particularly during the daytime. Further comparisons indicated that the simulation-implemented AOD could better capture the vertical structure of atmospheric wind. Accompanied with the lower planetary boundary layer and the increased atmospheric stability, both U and V wind at 850 hPa showed convergences which were unfavorable for pollutant dispersion. Since RMPAS-ST provides meteorological initial conditions for RMAPS-Chem, the changes of meteorology introduced by aerosol–radiation interaction would routinely impact the simulations of pollutants. To verify the statistical significance of the results, we further conducted the 24 h forecasts for a longer period lasting 27 d (13 January–8 February 2017), with no AOD field (NoAero) and WRF-Chem-simulated hourly AOD fields (Aero) included, as well as a constant AOD value of 0.12 (ClimAero). The 1-month results were statistically significant and indicated that the mean RMSE of 2 m temperature (wind speed at 10 m) in Aero and ClimAero relative to NoAero was reduced by 4.0 % (1.9 %) and 1.2 % (1.6 %). More detailed evaluations and analysis will be addressed in a future article. These results demonstrated the influence of aerosol–radiation interactions on the improvement of predictive accuracy and the potential prospects to offline coupling of near-real-time aerosol information in regional RMAPS-ST NWP in northern China.

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A hybrid method for reconstructing the historical evolution of aerosol optical depth from sunshine duration measurements

Atmospheric Measurement Techniques ◽

10.5194/amt-13-3061-2020 ◽

2020 ◽

Vol 13 (6) ◽

pp. 3061-3079

Author(s):

William Wandji Nyamsi ◽

Antti Lipponen ◽

Arturo Sanchez-Lorenzo ◽

Martin Wild ◽

Antti Arola

Keyword(s):

Aerosol Optical Depth ◽

Optical Depth ◽

Sunshine Duration ◽

Volcanic Eruptions ◽

Preliminary Evidence ◽

Global Scale ◽

Historical Evolution ◽

Physically Based ◽

Daily Water ◽

Novel Method

Abstract. A novel method has been developed to estimate aerosol optical depth (AOD) from sunshine duration (SD) measurements under cloud-free conditions. It is a physically based method serving for the reconstruction of the historical evolution of AOD during the last century. In addition to sunshine duration data, it requires daily water vapor and ozone products as inputs taken from the ECMWF 20th century reanalysis ERA-20C, available at the global scale over the period 1900–2010. Surface synoptic cloud observations are used to identify cloud-free days. For 16 sites over Europe, the accuracy of the estimated daily AOD, and its seasonal variability, is similar to or better than those from two earlier methods when compared to AErosol RObotic NETwork measurements. In addition, it also improves the detection of the signal from massive aerosol events such as important volcanic eruptions (e.g., Arenal and Fernandina Island in 1968, El Chichón in 1982 and Pinatubo in 1992). Finally, the reconstructed AOD time series are in good agreement with the dimming/brightening phenomenon and also provide preliminary evidence of the early-brightening phenomenon.

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Comparison of aerosol optical depth over northern China derived from ground-based measurements and MODIS

10.1117/12.891045 ◽

2011 ◽

Author(s):

Kaixu Bai ◽

Chaoshun Liu ◽

Runhe Shi ◽

Wei Gao

Keyword(s):

Aerosol Optical Depth ◽

Optical Depth ◽

Northern China

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Validation of JAXA Himawari-8 Aerosol Optical Depth Products over China with AERONET and CARSNET Observations

10.5194/egusphere-egu2020-18695 ◽

2020 ◽

Author(s):

Ling Gao ◽

Chengcai Li ◽

Lin Chen ◽

Jun Li ◽

Huizheng Che

Keyword(s):

Aerosol Optical Depth ◽

Optical Depth ◽

Southern China ◽

Correlation Coefficients ◽

Northern China ◽

Temporal Variations ◽

Retrieval Algorithm ◽

High Temporal Resolution ◽

Surface Reflectance ◽

Modis Aod

The performance of JAXA Himawari-8 Advanced Himawari Imager (AHI) aerosol optical depth (AOD) products over China is evaluated with ground-based AErosol&#160;RObotic&#160;NETwork (AERONET) and Sun-Sky Radiometer Observation Network (CARSNET) observations as well as the Moderate Resolution Imaging Spectroradiometer (MODIS) AOD products. Considering the quality and quantity of valid data, the study was limited to AOD products from AHI with a Quality Assurance Flag (QA_Flag) of &#8220;good&#8221; and &#8220;very good.&#8221; The spatial distribution of the AHI AOD product is similar to that of the MODIS AOD product. The AOD correlation between AHI and MODIS is better in the morning than in the afternoon after March, however, using MODIS AOD as a reference resulted in underestimation in the morning and overestimation in the afternoon. The bias is also larger in spring and autumn than in summer and winter. Validation with sun-photometer observations indicates good correlation between AHI AOD and ground-based observations with correlation coefficients larger than 0.75 (N>1000) when barren and sparsely vegetated surfaces are excluded. At 02:30 UTC, 53% of the collocated AHI AOD observations fall in the expected error (EE) range and at 5:30 UTC, 59.3% fall above the EE. The AHI AOD overestimation was apparent at the Northern China stations in April and after October, whereas the underestimation was apparent in southern China throughout the year. The temporal variations of AHI and AERONET AOD also show that the overestimation occurred in the afternoon and underestimation occurred in the morning.The assumption that the solar geometries were nearly identical and the surface reflectance unchanged for a month causes the surface reflectance underestimation and leads to the AOD overestimation for barren surfaces in autumn and winter. Because background aerosols were neglected, the surface reflectance was overestimated, leading to AOD underestimation in vegetated surfaces.Overall, the JAXA AOD provides a reliable and high temporal resolution aerosol product for environmental and climate research and the aerosol retrieval algorithm requires improvement.

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