scholarly journals GOME-2A retrievals of tropospheric NO<sub>2</sub> in different spectral ranges – influence of penetration depth

2018 ◽  
Vol 11 (5) ◽  
pp. 2769-2795 ◽  
Author(s):  
Lisa K. Behrens ◽  
Andreas Hilboll ◽  
Andreas Richter ◽  
Enno Peters ◽  
Henk Eskes ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Radiative Transfer ◽  
Spectral Range ◽  
Biomass Burning ◽  
Vertical Profile ◽  
Lower Troposphere ◽  
Optical Absorption Spectroscopy ◽  
Tropical Africa ◽  
Profile Shape ◽  
Spectral Ranges

Abstract. In this study, we present a novel nitrogen dioxide (NO2) differential optical absorption spectroscopy (DOAS) retrieval in the ultraviolet (UV) spectral range for observations from the Global Ozone Monitoring Instrument 2 on board EUMETSAT's MetOp-A (GOME-2A) satellite. We compare the results to those from an established NO2 retrieval in the visible (vis) spectral range from the same instrument and investigate how differences between the two are linked to the NO2 vertical profile shape in the troposphere.As expected, radiative transfer calculations for satellite geometries show that the sensitivity close to the ground is higher in the vis than in the UV spectral range. Consequently, NO2 slant column densities (SCDs) in the vis are usually higher than in the UV if the NO2 is close to the surface. Therefore, these differences in NO2 SCDs between the two spectral ranges contain information on the vertical distribution of NO2 in the troposphere. We combine these results with radiative transfer calculations and simulated NO2 fields from the TM5-MP chemistry transport model to evaluate the simulated NO2 vertical distribution.We investigate regions representative of both anthropogenic and biomass burning NO2 pollution. Anthropogenic air pollution is mostly located in the boundary layer close to the surface, which is reflected by large differences between UV and vis SCDs of  ∼  60 %. Biomass burning NO2 in contrast is often uplifted into elevated layers above the boundary layer. This is best seen in tropical Africa south of the Equator, where the biomass burning NO2 is well observed in the UV, and the SCD difference between the two spectral ranges is only  ∼  36 %. In tropical Africa north of the Equator, however, the biomass burning NO2 is located closer to the ground, reducing its visibility in the UV.While not enabling a full retrieval of the vertical NO2 profile shape in the troposphere, our results can help to constrain the vertical profile of NO2 in the lower troposphere and, when analysed together with simulated NO2 fields, can help to better interpret the model output.

scholarly journals Investigation of NO<sub>2</sub> vertical distribution using two DOAS retrievals for GOME-2A measurements in the UV and vis spectral range

2017 ◽  
Author(s):  
Lisa K. Behrens ◽  
Andreas Hilboll ◽  
Andreas Richter ◽  
Enno Peters ◽  
Henk Eskes ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Radiative Transfer ◽  
Vertical Distribution ◽  
Spectral Range ◽  
Biomass Burning ◽  
Vertical Profile ◽  
Lower Troposphere ◽  
Tropical Africa ◽  
Profile Shape ◽  
Spectral Ranges

Abstract. In this study, we present a novel NO2 DOAS retrieval in the ultraviolet (UV) spectral range for satellite observations from the Global Ozone Monitoring Instrument 2 on board EUMETSAT’s MetOp-A (GOME-2A) satellite. We compare the results to those from an established NO2 retrieval in the visible (vis) spectral range from the same instrument and infer information about the NO2 vertical profile shape in the troposphere. As expected, radiative transfer calculations for satellite geometries show that the sensitivity close to the ground is higher in the vis than in the UV spectral range. Consequently, NO2 slant column densities (SCDs) in the vis are usually higher than in the UV, if the NO2 is close to the surface. Therefore, these differences in NO2 SCDs between the two spectral ranges contain information on the vertical distribution of NO2 in the troposphere. We combine these results with radiative transfer calculations and simulated NO2 fields from the TM5 chemistry transport model to evaluate the simulated NO2 vertical distribution. We investigate regions representative for both anthropogenic and biomass burning NO2 pollution. Anthropogenic air pollution is mostly located in the boundary layer close to the surface, which is reflected by the large differences between UV and vis SCDs of ~ 60 %. Biomass burning NO2 in contrast is often uplifted into elevated layers above the boundary layer. This is best seen in tropical Africa south of the equator, where the biomass burning NO2 is well observed in the UV, and the difference between the two spectral ranges is only ~ 36 %. In tropical Africa north of the equator, however, the biomass burning NO2 is located closer to the ground, reducing its visibility. While not enabling a full retrieval of the vertical NO2 profile shape in the troposphere, our results can help to constrain the vertical profile of NO2 in the lower troposphere and, when analyzed together with simulated NO2 fields, can help interpret the model output.

Black Carbon profiles from tethered balloon flights over the Southeastern Tibetan Plateau

2020 ◽  
Author(s):  
Mo Wang ◽  
Baiqing Xu ◽  
Song Yang ◽  
Jing Gao ◽  
Taihua Zhang ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Relative Humidity ◽  
Tibetan Plateau ◽  
Vertical Distribution ◽  
Biomass Burning ◽  
Vertical Profile ◽  
Mass Concentration ◽  
Maximum Height ◽  
Free Troposphere ◽  
Tethered Balloon

&lt;p&gt;Black carbon (BC) can change the energy budget of the earth system by strongly absorbing solar radiation: both suspended in the atmosphere, incorporated into cloud droplets, or deposited onto high-albedo surfaces. BC&amp;#8217;s direct radiative forcing is highly dependent on its vertical distribution. However, due to large variabilities and the small number of vertical profile measurements, there is still large uncertainty in this forcing value. Moreover, the vertical profile of BC and its relative elevation to clouds determine BC&amp;#8217;s lifetime in the atmosphere and its transport and removal processes. In November-December 2017, a series of tethered balloon flights was launched at the Southeast Tibet Observation and Research Station for the Alpine Environment of the Chinese Academy of Sciences. A cylindrical balloon with a diameter of 7.9 m and maximum volume of 1250 m&lt;sup&gt;3&lt;/sup&gt; was used. A 7-channel Aethalometer was installed in the gondola attached to the balloon, together with several other instruments including a GPS for altitude, and sensors for temperature and relative humidity. The airborne Aethalometer measured BC mass concentration (ng/m&lt;sup&gt;3&lt;/sup&gt;) on a on a 1-second timebase at 7 wavelengths ranging from 370 nm to 950 nm. Meanwhile, another Aethalometer was used to monitor BC mass concentration near the surface, at a height of about 10 m above the ground. From the tethered balloon flights, we derived three profiles designated as &amp;#8216;F1&amp;#8217;, &amp;#8216;F3-ASC&amp;#8217;, and &amp;#8216;F3-DES&amp;#8217;. The maximum height for the F1 flight was 500 m a.g.l., namely 3800 m a.s.l.; while the maximum height for the F3 flight was 1950 m a.g.l., namely 5250 m a.s.l. Based on the potential temperature and relative humidity data, the profiles were divided into three layers: the stable boundary layer (SBL), the residual layer (RL), and the free troposphere (FT). The vertical distribution of BC shows a prominent peak within the SBL. The mean BC concentration in SBL (1000&amp;#177;750 ng/m&lt;sup&gt;3&lt;/sup&gt;) was one order of magnitude higher than in RL and FT, which were 140&amp;#177;40 ng/m&lt;sup&gt;3&lt;/sup&gt; and 120&amp;#177;40 ng/m&lt;sup&gt;3&lt;/sup&gt;, respectively. The BC concentration measured in the present study in FT over the southeastern Tibetan Plateau is comparable to measurements in Arctic regions, but lower than values in South Asia. Analysis of the wavelength dependence of the data yields an estimate of the biomass burning contribution. This showed a maximum value in SBL of 44&amp;#177;37%, and was 16&amp;#177;6% in RL and 13&amp;#177;5% in FT. Analysis of 24-hour isentropic back trajectories showed that BC in SBL and RL was dominated by local sources, while in the FT, BC is mainly influenced by mid- to long-distant transport by the westerlies. In addition, analysis of the variations of BC concentration and biomass burning contribution on a high-resolution time scale showed that BC concentrations and the nature of their sources are largely influenced by air mass origins and transport. To our knowledge, this is the first ever in situ measurement of BC concentration over the Tibetan Plateau in the atmospheric boundary layer and free troposphere up to 5000 m a.s.l.&lt;/p&gt;

scholarly journals Parameterizing radiative transfer to convert MAX-DOAS dSCDs into near-surface box averaged mixing ratios and vertical profiles

2012 ◽  
Vol 5 (5) ◽  
pp. 7641-7673 ◽  
Author(s):  
R. Sinreich ◽  
A. Merten ◽  
L. Molina ◽  
R. Volkamer
Keyword(s):  
Boundary Layer ◽  
Radiative Transfer ◽  
Mexico City ◽  
Vertical Gradient ◽  
Trace Gas ◽  
Optical Absorption Spectroscopy ◽  
Transfer Model ◽  
Model Calculations ◽  
Near Surface ◽  
Mixing Ratios

Abstract. We present a novel parameterization method to convert Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) differential Slant Column Densities (dSCDs) into near-surface box averaged volume mixing ratios. The approach is applicable inside the planetary boundary layer under conditions with significant aerosol load, does not require a-priori assumptions about the trace gas vertical distribution and builds on the increased sensitivity of MAX-DOAS near the instrument altitude. It parameterizes radiative transfer model calculations and significantly reduces the computational effort. The biggest benefit of this method is that the retrieval of an aerosol profile, which usually is necessary for deriving a trace gas concentration from MAX-DOAS dSCDs, is not needed. The method is applied to NO2 MAX-DOAS dSCDs recorded during the Mexico City Metropolitan Area 2006 (MCMA-2006) measurement campaign. The retrieved volume mixing ratios of two elevation angles (1° and 3°) are compared to volume mixing ratios measured by two long-path (LP)-DOAS instruments located at the same site. Measurements are found to agree well during times when vertical mixing is expected to be strong. However, inhomogeneities in the air mass above Mexico City can be detected by exploiting the different horizontal and vertical dimensions probed by MAX-DOAS measurements at different elevation angles, and by LP-DOAS. In particular, a vertical gradient in NO2 close to the ground can be observed in the afternoon, and is attributed to reduced mixing coupled with near surface emission. The existence of a vertical gradient in the lower 250 m during parts of the day shows the general challenge of sampling the boundary layer in a representative way and emphasizes the need of vertically resolved measurements.

scholarly journals Determination of tropospheric vertical columns of NO<sub>2</sub> and aerosol optical properties in a rural setting using MAX-DOAS

2011 ◽  
Vol 11 (23) ◽  
pp. 12475-12498 ◽  
Author(s):  
J. D. Halla ◽  
T. Wagner ◽  
S. Beirle ◽  
J. R. Brook ◽  
K. L. Hayden ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Radiative Transfer ◽  
Urban Areas ◽  
Source Region ◽  
Time Of Day ◽  
Rural Setting ◽  
Radiative Transfer Model ◽  
Optical Absorption Spectroscopy ◽  
Transfer Model ◽  
Vertical Column

Abstract. Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements were performed in a rural location of southwestern Ontario during the Border Air Quality and Meteorology Study. Slant column densities (SCDs) of NO2 and O4 were determined using the standard DOAS technique. Using a radiative transfer model and the O4 SCDs, aerosol optical depths were determined for clear sky conditions and compared to OMI, MODIS, AERONET, and local PM2.5 measurements. This aerosol information was input to a radiative transfer model to calculate NO2 air mass factors, which were fit to the measured NO2 SCDs to determine tropospheric vertical column densities (VCDs) of NO2. The method of determining NO2 VCDs in this way was validated for the first time by comparison to composite VCDs derived from aircraft and ground-based measurements of NO2. The new VCDs were compared to VCDs of NO2 determined via retrievals from the satellite instruments SCIAMACHY and OMI, for overlapping time periods. The satellite-derived VCDs were higher, with a mean bias of +0.5–0.9×1015 molec cm−2. This last finding is different from previous studies whereby MAX-DOAS geometric VCDs were higher than satellite determinations, albeit for urban areas with higher VCDs. An effective boundary layer height, BLHeff, is defined as the ratio of the tropospheric VCD and the ground level concentration of NO2. Variations of BLHeff can be linked to time of day, source region, stability of the atmosphere, and the presence or absence of elevated NOx sources. In particular, a case study is shown where a high VCD and BLHeff were observed when an elevated industrial plume of NOx and SO2 was fumigated to the surface as a lake breeze impacted the measurement site. High BLHeff values (~1.9 km) were observed during a regional smog event when high winds from the SW and high convection promoted mixing throughout the boundary layer. During this event, the regional line flux of NO2 through the region was estimated to be greater than 112 kg NO2 km−1 h−1.

scholarly journals Parameterizing radiative transfer to convert MAX-DOAS dSCDs into near-surface box-averaged mixing ratios

2013 ◽  
Vol 6 (6) ◽  
pp. 1521-1532 ◽  
Author(s):  
R. Sinreich ◽  
A. Merten ◽  
L. Molina ◽  
R. Volkamer
Keyword(s):  
Boundary Layer ◽  
Radiative Transfer ◽  
Mexico City ◽  
Vertical Gradient ◽  
Radiative Transfer Model ◽  
Optical Absorption Spectroscopy ◽  
Transfer Model ◽  
Model Calculations ◽  
Near Surface ◽  
Mixing Ratios

Abstract. We present a novel parameterization method to convert multi-axis differential optical absorption spectroscopy (MAX-DOAS) differential slant column densities (dSCDs) into near-surface box-averaged volume mixing ratios. The approach is applicable inside the planetary boundary layer under conditions with significant aerosol load, and builds on the increased sensitivity of MAX-DOAS near the instrument altitude. It parameterizes radiative transfer model calculations and significantly reduces the computational effort, while retrieving ~ 1 degree of freedom. The biggest benefit of this method is that the retrieval of an aerosol profile, which usually is necessary for deriving a trace gas concentration from MAX-DOAS dSCDs, is not needed. The method is applied to NO2 MAX-DOAS dSCDs recorded during the Mexico City Metropolitan Area 2006 (MCMA-2006) measurement campaign. The retrieved volume mixing ratios of two elevation angles (1° and 3°) are compared to volume mixing ratios measured by two long-path (LP)-DOAS instruments located at the same site. Measurements are found to agree well during times when vertical mixing is expected to be strong. However, inhomogeneities in the air mass above Mexico City can be detected by exploiting the different horizontal and vertical dimensions probed by the MAX-DOAS and LP-DOAS instruments. In particular, a vertical gradient in NO2 close to the ground can be observed in the afternoon, and is attributed to reduced mixing coupled with near-surface emission inside street canyons. The existence of a vertical gradient in the lower 250 m during parts of the day shows the general challenge of sampling the boundary layer in a representative way, and emphasizes the need of vertically resolved measurements.

scholarly journals DOAS measurements of formaldehyde and glyoxal above a South-East Asian tropical rainforest

2012 ◽  
Vol 12 (2) ◽  
pp. 5903-5937 ◽  
Author(s):  
S. M. MacDonald ◽  
H. Oetjen ◽  
A. S. Mahajan ◽  
L. K. Whalley ◽  
P. M. Edwards ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Tropical Rainforest ◽  
East Asian ◽  
Lower Troposphere ◽  
Oxidation Products ◽  
Optical Absorption Spectroscopy ◽  
Forest Environment ◽  
Important Conclusion ◽  
Measured Ratio ◽  
High Concentrations

Abstract. Tropical rainforests act as a huge contributor to the global emissions of biogenic volatile organic compounds (BVOCs). Measurements of their oxidation products, such as formaldehyde (HCHO) and glyoxal (CHOCHO), provide useful indicators of fast photochemistry occurring in the lower troposphere. However, measurements of these species in tropical forest locations are extremely limited. To redress this, HCHO and CHOCHO were measured using the long-path (LP) and multi-axis (MAX) differential optical absorption spectroscopy (DOAS) techniques above the rainforest canopy in Borneo during two campaigns in spring and summer 2008, as part of the Oxidant and Particle Photochemical Processes above a South-East Asian tropical rainforest (OP3) project. The results were compared with concurrent measurements of hydroxyl radical (OH), isoprene (C5H8) (which was the dominant organic species emitted in this forest environment), and various meteorological parameters. Formaldehyde was observed at a maximum concentration of 4.5 ppb and glyoxal at a maximum of 1.6 ppb, significantly higher than previous measurements in rural locations. A 1-D chemistry model was then used to assess the diurnal evolution of formaldehyde and glyoxal throughout the boundary layer. The results, which compare well with the LP-DOAS and MAX-DOAS observations, suggest that the majority of the glyoxal and formaldehyde is confined to the first 500 m of the boundary layer, and that the measured ratio of these species is reproduced using currently accepted product yields for the oxidation of isoprene by OH. An important conclusion is that the measured levels of glyoxal are consistent with the surprisingly high concentrations of OH measured in this environment.

scholarly journals Constraints on global aerosol number concentration, SO<sub>2</sub> and condensation sink in UKESM1 using ATom measurements

2021 ◽  
Vol 21 (6) ◽  
pp. 4979-5014
Author(s):  
Ananth Ranjithkumar ◽  
Hamish Gordon ◽  
Christina Williamson ◽  
Andrew Rollins ◽  
Kirsty Pringle ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Vertical Profile ◽  
Dimethyl Sulfide ◽  
Dominant Role ◽  
Model Performance ◽  
Lower Troposphere ◽  
Cloud Droplet ◽  
Number Concentration ◽  
Atmospheric Processes ◽  
Condensation Sink

Abstract. Understanding the vertical distribution of aerosol helps to reduce the uncertainty in the aerosol life cycle and therefore in the estimation of the direct and indirect aerosol forcing. To improve our understanding, we use measurements from four deployments of the Atmospheric Tomography (ATom) field campaign (ATom1–4) which systematically sampled aerosol and trace gases over the Pacific and Atlantic oceans with near pole-to-pole coverage. We evaluate the UK Earth System Model (UKESM1) against ATom observations in terms of joint biases in the vertical profile of three variables related to new particle formation: total particle number concentration (NTotal), sulfur dioxide (SO2) mixing ratio and the condensation sink. The NTotal, SO2 and condensation sink are interdependent quantities and have a controlling influence on the vertical profile of each other; therefore, analysing them simultaneously helps to avoid getting the right answer for the wrong reasons. The simulated condensation sink in the baseline model is within a factor of 2 of observations, but the NTotal and SO2 show much larger biases mainly in the tropics and high latitudes. We performed a series of model sensitivity tests to identify atmospheric processes that have the strongest influence on overall model performance. The perturbations take the form of global scaling factors or improvements to the representation of atmospheric processes in the model, for example by adding a new boundary layer nucleation scheme. In the boundary layer (below 1 km altitude) and lower troposphere (1–4 km), inclusion of a boundary layer nucleation scheme (Metzger et al., 2010) is critical to obtaining better agreement with observations. However, in the mid (4–8 km) and upper troposphere (> 8 km), sub-3 nm particle growth, pH of cloud droplets, dimethyl sulfide (DMS) emissions, upper-tropospheric nucleation rate, SO2 gas-scavenging rate and cloud erosion rate play a more dominant role. We find that perturbations to boundary layer nucleation, sub-3 nm growth, cloud droplet pH and DMS emissions reduce the boundary layer and upper tropospheric model bias simultaneously. In a combined simulation with all four perturbations, the SO2 and condensation sink profiles are in much better agreement with observations, but the NTotal profile still shows large deviations, which suggests a possible structural issue with how nucleation or gas/particle transport or aerosol scavenging is handled in the model. These perturbations are well-motivated in that they improve the physical basis of the model and are suitable for implementation in future versions of UKESM.

scholarly journals Constraints on global aerosol number concentration, SO<sub>2</sub> and condensation sink in UKESM1 using ATom measurements

2020 ◽  
Author(s):  
Ananth Ranjithkumar ◽  
Hamish Gordon ◽  
Christina Williamson ◽  
Andrew Rollins ◽  
Kirsty J. Pringle ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Vertical Profile ◽  
Dominant Role ◽  
Model Performance ◽  
Lower Troposphere ◽  
Number Concentration ◽  
Sampled Data ◽  
Upper Troposphere ◽  
Atmospheric Processes ◽  
Condensation Sink

Abstract. Understanding the vertical distribution of aerosol helps to reduce the uncertainty in the aerosol lifecycle and therefore in the estimation of the direct and indirect aerosol forcing. To improve our understanding, we use measurements from four deployments of the Atmospheric Tomography (ATom) field campaign (ATom1-4) which systematically sampled data over the Pacific and Atlantic Oceans with near pole-to-pole coverage. We evaluate the UK Earth system model (UKESM1) against ATom observations in terms of joint biases in the vertical profile of three variables related to new particle formation: total particle number concentration (NTotal), sulphur dioxide (SO2) mixing ratio and the condensation sink. The NTotal, SO2 and condensation sink are interdependent quantities and have a controlling influence on the vertical profile of each other. Improving only one of these quantities in comparison with observations can lead to a misleading impression that overall model performance has improved. Analysing NTotal, SO2 and condensation sink simultaneously helps reduce the probability of getting the right answer for the wrong reasons. The model's condensation sink is within a factor of 2 of observations, but the NTotal and SO2 shows larger biases mainly in the tropics and high latitudes. Algorithmic improvements to the model and perturbations to key atmospheric processes help reduce tropospheric model biases consistently. We performed a series of model sensitivity tests to identify atmospheric processes that have the strongest influence on overall model performance (NTotal, SO2 and condensation sink simultaneously). In the boundary layer (which we define in this study as below 1 km altitude) and lower troposphere (1–4 km) inclusion of a boundary layer nucleation scheme (Metzger et al., 2010), which is switched off in the default version of UKESM, is critical to obtaining better agreement with observations. However, in the mid (4–8 km) and upper troposphere (> 8 km), sub-3 nm particle growth, pH of cloud droplets, DMS emissions, upper tropospheric nucleation rate, SO2 gas scavenging rate and cloud erosion rate are found to play a more dominant role. Analysing the data with altitude, we find that perturbations to boundary layer nucleation, sub 3 nm growth, cloud droplet pH and DMS emissions reduces the boundary layer and upper tropospheric model bias. We performed a combined simulation with all 4 perturbations included and found that the model's NTotal, SO2 and condensation sink biases were reduced in most cases (up to a 50 % reduction) in both the boundary layer and upper troposphere simultaneously. These perturbations are well-motivated in that they improve the physical basis of the model and are suitable for implementation in future versions of UKESM.

scholarly journals First retrieval of tropospheric aerosol profiles using MAX-DOAS and comparison with lidar and sky radiometer measurements

2008 ◽  
Vol 8 (2) ◽  
pp. 341-350 ◽  
Author(s):  
H. Irie ◽  
Y. Kanaya ◽  
H. Akimoto ◽  
H. Iwabuchi ◽  
A. Shimizu ◽  
...  
Keyword(s):  
Optical Absorption ◽  
Vertical Profile ◽  
Lower Troposphere ◽  
Optimal Estimation ◽  
Estimation Methods ◽  
Optical Absorption Spectroscopy ◽  
Lidar Data ◽  
Aerosol Extinction ◽  
Tropospheric Aerosol ◽  
Aerosol Extinction Coefficient

Abstract. Ground-based Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements were performed at Tsukuba, Japan (36.1° N, 140.1° E), in November–December 2006. By analyzing the measured spectra of scattered sunlight with DOAS and optimal estimation methods, we first retrieve the aerosol optical depth (τ) and the vertical profile of the aerosol extinction coefficient (k) at 476 nm in the lower troposphere. These retrieved quantities are characterized through comparisons with coincident lidar and sky radiometer measurements. The retrieved k values for layers of 0–1 and 1–2 km agree with lidar data to within 30% and 60%, respectively, for most cases, including partly cloudy conditions. Results similar to k at 0–1 km are obtained for the retrieved τ values, demonstrating that MAX-DOAS provides a new, unique aerosol dataset in the lower troposphere.

scholarly journals Performance of MAX-DOAS measurements of aerosols at Tsukuba, Japan: a comparison with lidar and sky radiometer measurements

2007 ◽  
Vol 7 (4) ◽  
pp. 9769-9793 ◽  
Author(s):  
H. Irie ◽  
Y. Kanaya ◽  
H. Akimoto ◽  
H. Iwabuchi ◽  
A. Shimizu ◽  
...  
Keyword(s):  
Optical Absorption ◽  
Extinction Coefficient ◽  
Vertical Profile ◽  
Lower Troposphere ◽  
Optimal Estimation ◽  
Estimation Methods ◽  
Optical Absorption Spectroscopy ◽  
Lidar Data ◽  
Aerosol Extinction ◽  
Aerosol Extinction Coefficient

Abstract. Ground-based Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements were performed at Tsukuba, Japan (36.1° N, 140.1° E), in November–December 2006. The measured spectra of scattered sunlight are analyzed by DOAS and optimal estimation methods to retrieve the aerosol optical depth (τ) and the vertical profile of the aerosol extinction coefficient (σ) at 476 nm in the lower troposphere. We characterize these retrieved quantities through comparisons with coincident lidar and sky radiometer measurements. The retrieved σ values for layers of 0–1 and 1–2 km agree with lidar data to within 30% and 60%, respectively, for most cases, including partly cloudy conditions. Results similar to σ at 0–1 km are obtained for the retrieved τ values, demonstrating that MAX-DOAS provides the new, unique aerosol dataset in the lower troposphere.

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