Probing into the impact of 3DVAR assimilation of surface PM<sub>10</sub> observations over China using process analysis

Jiang, Zhe; Liu, Zhiquan; Wang, Tijian; Schwartz, Craig S.; Lin, Hui-Chuan; Jiang, Fei

doi:10.1002/jgrd.50495

Cited by 84 publications

(89 citation statements)

References 90 publications

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“…The CO emission optimization follows (35), which optimize monthly CO emissions independently with initial conditions for each month estimated from a sub-optimal Kalman filter (65). The CO2:CO emission ratio ( CO2:CO ) at each grid point is calculated using CO2 and CO emission factors ( co 2 , co ) and dry mass matter ( ) for six vegetation types used in GEOS-Chem:…”

Section: (C) Quantification Of Biomass Burning Carbon Fluxesmentioning

confidence: 99%

Contrasting carbon cycle responses of the tropical continents to the 2015–2016 El Niño

Liu

Bowman

Schimel

et al. 2017

Science

381

504

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INTRODUCTION The influence of El Niño on climate is accompanied by large changes to the carbon cycle, and El Niño–induced variability in the carbon cycle has been attributed mainly to the tropical continents. However, owing to a dearth of observations in the tropics, tropical carbon fluxes are poorly quantified, and considerable debate exists over the dominant mechanisms (e.g., plant growth, respiration, fire) and regions (e.g., humid versus semiarid tropics) on the net carbon balance. RATIONALE The launch of the Orbiting Carbon Observatory-2 (OCO-2) shortly before the 2015–2016 El Niño, the second strongest since the 1950s, has provided an opportunity to understand how tropical land carbon fluxes respond to the warm and dry climate characteristics of El Niño conditions. The El Niño events may also provide a natural experiment to study the response of tropical land carbon fluxes to future climate changes, because anomalously warm and dry tropical environments typical of El Niño are expected to be more frequent under most emission scenarios. RESULTS The tropical regions of three continents (South America, Asia, and Africa) had heterogeneous responses to the 2015–2016 El Niño, in terms of both climate drivers and the carbon cycle. The annual mean precipitation over tropical South America and tropical Asia was lower by 3.0σ and 2.8σ, respectively, in 2015 relative to the 2011 La Niña year. Tropical Africa, on the other hand, had near equal precipitation and the same number of dry months between 2015 and 2011; however, surface temperatures were higher by 1.6σ, dominated by the positive anomaly over its eastern and southern regions. In response to the warmer and drier climate anomaly in 2015, the pantropical biosphere released 2.5 ± 0.34 gigatons more carbon into the atmosphere than in 2011, which accounts for 83.3% of the global total 3.0–gigatons of carbon (gigatons C) net biosphere flux differences and 92.6% of the atmospheric CO 2 growth-rate differences between 2015 and 2011. It indicates that the tropical land biosphere flux anomaly was the driver of the highest atmospheric CO 2 growth rate in 2015. The three tropical continents had an approximately even contribution to the pantropical net carbon flux anomaly in 2015, but had diverse dominant processes: gross primary production (GPP) reduced carbon uptake (0.9 ± 0.96 gigatons C) in tropical South America, fire increased carbon release (0.4 ± 0.08 gigatons C) in tropical Asia, and respiration increased carbon release (0.6 ± 1.01 gigatons C) in Africa. We found that most of the excess carbon release in 2015 was associated with either extremely low precipitation or high temperatures, or both. CONCLUSION Our results indicate that the global El Niño effect is a superposition of regionally specific effects. The heterogeneous climate forcing and carbon response over the three tropical continents to the 2015–2016 El Niño challenges previous studies that suggested that a single dominant process determines carbon cycle interannual variability, which could also be due to previous disturbance and soil and vegetation structure. The similarity between the 2015 tropical climate anomaly and the projected climate changes imply that the role of the tropical land as a buffer for fossil fuel emissions may be reduced in the future. The heterogeneous response may reflect differences in temperature and rainfall anomalies, but intrinsic differences in vegetation species, soils, and prior disturbance may contribute as well. A synergistic use of multiple satellite observations and a long time series of spatially resolved fluxes derived from sustained satellite observations will enable tests of these hypotheses, allow for a more process-based understanding, and, ultimately, aid improved carbon-climate model projections. Diverse climate driver anomalies and carbon cycle responses to the 2015–2016 El Niño over the three tropical continents. Schematic of climate anomaly patterns over the three tropical continents and the anomalies of the net carbon flux and its dominant constituent flux (i.e., GPP, respiration, and fire) relative to the 2011 La Niña during the 2015–2016 El Niño. GtC, gigatons C.

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Section: (C) Quantification Of Biomass Burning Carbon Fluxesmentioning

confidence: 99%

Contrasting carbon cycle responses of the tropical continents to the 2015–2016 El Niño

Liu

Bowman

Schimel

et al. 2017

Science

381

504

View full text Add to dashboard Cite

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“…Additionally, this work will help to improve aerosol model performance as well as the modelled climatic effects in the relevant regions. Firstly, the observed aerosol parameters can be used for data assimilation to obtain more accurate inputs (including improved initial conditions and air pollutant emissions) for the model (Jiang et al, 2013;Peng et al, 2017). Secondly, more precise aerosol refractive indexes and size distributions used in these numerical models will yield more reasonable aerosol loadings and DRFs (Ma et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

The optical properties, physical properties and direct radiative forcing of urban columnar aerosols in the Yangtze River Delta, China

et al. 2018

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Abstract. The optical and physical properties as well as the direct radiative forcings (DRFs) of fractionated aerosols in the urban area of the western Yangtze River Delta (YRD) are investigated with measurements from a Cimel sun photometer combined with a radiation transfer model. Ground-based observations of aerosols have much higher temporal resolutions than satellite retrievals. An initial analysis reveals the characteristics of the optical properties of different types of fractionated aerosols in the western YRD. The total aerosols, mostly composed of scattering components (93.8 %), have mean optical depths of 0.65 at 550 nm and refractive index of 1.44 + 0.0084i at 440 nm. The fine aerosols are approximately four times more abundant and have very different compositions from coarse aerosols. The absorbing components account for only ∼ 4.6 % of fine aerosols and 15.5 % of coarse aerosols and have smaller sizes than the scattering aerosols within the same mode. Therefore, fine particles have stronger scattering than coarse ones, simultaneously reflecting the different size distributions between the absorbing and scattering aerosols. The relationships among the optical properties quantify the aerosol mixing and imply that approximately 15 and 27.5 % of the total occurrences result in dustand black-carbon-dominating mixing aerosols, respectively, in the western YRD. Unlike the optical properties, the size distributions of aerosols in the western YRD are similar to those found at other sites over eastern China on a climatological scale, peaking at radii of 0.148 and 2.94 µm. However, further analysis reveals that the coarse-dominated particles can also lead to severe haze pollution over the YRD. Observation-based estimations indicate that both fine and coarse aerosols in the western YRD exert negative DRFs, and this is especially true for fine aerosols (−11.17 W m −2 at the top of atmosphere, TOA). A higher absorption fraction leads directly to the negative DRF being further offset for coarse aerosols (−0.33 W m −2 ) at the TOA. Similarly, the coarsemode DRF contributes to only 13.3 % of the total scattering aerosols but > 33.7 % to the total absorbing aerosols. A sensitivity analysis states that aerosol DRFs are not highly sensitive to their profiles in clear-sky conditions. Most of the aerosol properties and DRFs have substantial seasonality in the western YRD. The results further reveal the contributions of each component of the different size particles to the total aerosol optical depths (AODs) and DRFs. Additionally, these results can be used to improve aerosol modelling performance and the modelling of aerosol effects in the eastern regions of China.

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“…Hakami et al (2005) and Yumimoto et al (2007Yumimoto et al ( , 2008 attempted to apply a four-dimensional variational method (a so-called advanced data assimilation method) to inverse modeling of black carbon (BC) and dust aerosols with ground-based observations and regional models. To date, measurements obtained by various observation platforms, including MODIS (Dai et al, 2014;Huneeus et al, 2012;Wang et al, 2012;Zhang et al, 2008), CALIPSO (Sekiyama et al, 2010;Zhang et al, 2011Zhang et al, , 2014, Himawari 8 (Yumimoto et al, 2016), AERONET (Schutgens et al, 2010a), and surface PM 10 (particulate matter with diameters less than 10 µm) monitoring systems (Tombette et al, 2009;Lee et al, 2013;Jiang et al, 2013), have been used in assimilation studies adopting both variational (Benedetti et al, 2009;Dubovik et al, 2008;Hakami et al, 2007;Henze et al, 2007;Yumimoto and Takemura, 2013) and ensemble-based Schutgens et al, 2010b;Di Tomaso et al, 2017;Yumimoto and Takemura, 2011) methods.…”

Section: Introductionmentioning

confidence: 99%

JRAero: the Japanese Reanalysis for Aerosol v1.0

et al. 2017

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Abstract. A global aerosol reanalysis product named the Japanese Reanalysis for Aerosol (JRAero) was constructed by the Meteorological Research Institute (MRI) of the Japan Meteorological Agency. The reanalysis employs a global aerosol transport model developed by MRI and a twodimensional variational data assimilation method. It assimilates maps of aerosol optical depth (AOD) from MODIS onboard the Terra and Aqua satellites every 6 h and has a TL159 horizontal resolution (approximately 1.1 • × 1.1 • ). This paper describes the aerosol transport model, the data assimilation system, the observation data, and the setup of the reanalysis and examines its quality with AOD observations.Comparisons with MODIS AODs that were used for the assimilation showed that the reanalysis showed much better agreement than the free run (without assimilation) of the aerosol model and improved under-and overestimation in the free run, thus confirming the accuracy of the data assimilation system. The reanalysis had a root mean square error (RMSE) of 0.05, a correlation coefficient (R) of 0.96, a mean fractional error (MFE) of 23.7 %, a mean fractional bias (MFB) of 2.8 %, and an index of agreement (IOA) of 0.98. The better agreement of the first guess, compared to the free run, indicates that aerosol fields obtained by the reanalysis can improve short-term forecasts.AOD fields from the reanalysis also agreed well with monthly averaged global AODs obtained by the Aerosol Robotic Network (AERONET) (RMSE = 0.08, R = 0.90, MFE = 28.1 %, MFB = 0.6 %, and IOA = 0.93). Site-by-site comparison showed that the reanalysis was considerably better than the free run; RMSE was less than 0.10 at 86.4 % of the 181 AERONET sites, R was greater than 0.90 at 40.7 % of the sites, and IOA was greater than 0.90 at 43.4 % of the sites. However, the reanalysis tended to have a negative bias at urban sites (in particular, megacities in industrializing countries) and a positive bias at mountain sites, possibly because of insufficient anthropogenic emissions data, the coarse model resolution, and the difference in representativeness between satellite and ground-based observations.

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Probing into the impact of 3DVAR assimilation of surface PM₁₀ observations over China using process analysis

Cited by 84 publications

References 90 publications

Contrasting carbon cycle responses of the tropical continents to the 2015–2016 El Niño

Contrasting carbon cycle responses of the tropical continents to the 2015–2016 El Niño

The optical properties, physical properties and direct radiative forcing of urban columnar aerosols in the Yangtze River Delta, China

JRAero: the Japanese Reanalysis for Aerosol v1.0

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Probing into the impact of 3DVAR assimilation of surface PM10 observations over China using process analysis

Cited by 84 publications

References 90 publications

Contrasting carbon cycle responses of the tropical continents to the 2015–2016 El Niño

Contrasting carbon cycle responses of the tropical continents to the 2015–2016 El Niño

The optical properties, physical properties and direct radiative forcing of urban columnar aerosols in the Yangtze River Delta, China

JRAero: the Japanese Reanalysis for Aerosol v1.0

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Product

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Probing into the impact of 3DVAR assimilation of surface PM₁₀ observations over China using process analysis