scholarly journals Impact of aerosols and clouds on decadal trends in all-sky solar radiation over the Netherlands (1966–2015)

2017 ◽  
Vol 17 (13) ◽  
pp. 8081-8100 ◽  
Author(s):  
Reinout Boers ◽  
Theo Brandsma ◽  
A. Pier Siebesma
Keyword(s):  
The Netherlands ◽  
Cloud Amount ◽  
Functional Expression ◽  
Shortwave Radiation ◽  
Cloud Base ◽  
Data Set ◽  
Clear Sky ◽  
Radiation Data ◽  
Hourly Data ◽  
The Difference

Abstract. A 50-year hourly data set of global shortwave radiation, cloudiness and visibility over the Netherlands was used to quantify the contribution of aerosols and clouds to the trend in yearly-averaged all-sky radiation (1.81 ± 1.07 W m−2 decade−1). Yearly-averaged clear-sky and cloud-base radiation data show large year-to-year fluctuations caused by yearly changes in the occurrence of clear and cloudy periods and cannot be used for trend analysis. Therefore, proxy clear-sky and cloud-base radiations were computed. In a proxy analysis hourly radiation data falling within a fractional cloudiness value are fitted by monotonic increasing functions of solar zenith angle and summed over all zenith angles occurring in a single year to produce an average. Stable trends can then be computed from the proxy radiation data. A functional expression is derived whereby the trend in proxy all-sky radiation is a linear combination of trends in fractional cloudiness, proxy clear-sky radiation and proxy cloud-base radiation. Trends (per decade) in fractional cloudiness, proxy clear-sky and proxy cloud-base radiation were, respectively, 0.0097 ± 0.0062, 2.78 ± 0.50 and 3.43 ± 1.17 W m−2. To add up to the all-sky radiation the three trends have weight factors, namely the difference between the mean cloud-base and clear-sky radiation, the clear-sky fraction and the fractional cloudiness, respectively. Our analysis clearly demonstrates that all three components contribute significantly to the observed trend in all-sky radiation. Radiative transfer calculations using the aerosol optical thickness derived from visibility observations indicate that aerosol–radiation interaction (ARI) is a strong candidate to explain the upward trend in the clear-sky radiation. Aerosol–cloud interaction (ACI) may have some impact on cloud-base radiation, but it is suggested that decadal changes in cloud thickness and synoptic-scale changes in cloud amount also play an important role.

scholarly journals Impact of aerosols and clouds on decadal trends in all-sky solar radiation over the Netherlands (1966–2015)

2017 ◽  
Author(s):  
Reinout Boers ◽  
Theo Brandsma ◽  
A. Pier Siebesma
Keyword(s):  
Solar Radiation ◽  
The Netherlands ◽  
Cloud Amount ◽  
Shortwave Radiation ◽  
Cloud Base ◽  
Synoptic Scale ◽  
Upward Trend ◽  
Clear Sky ◽  
Strong Candidate ◽  
Cloud Thickness

Abstract. A 50-year hourly dataset of global shortwave radiation, cloudiness and visibility over the Netherlands was used to quantify the contribution of aerosols and clouds to trends in all-sky radiation. The trend in all-sky radiation was expressed as a linear combination of trends in fractional cloudiness, clear-sky radiation and cloud-base radiation (radiation emanating from the bottom of clouds). All three trends were derived from the data records. The results indicate that trends in all three components contribute significantly to the observed trend in all-sky radiation. Trends (per decade) in fractional cloudiness, all-sky, clear-sky and cloud-base radiation were respectively 0.0097 ± 0.0062, 1.81 ± 1.07 W m−2, 2.78 ± 0.50 W m−2, and 3.43 ± 1.17 W m−2. Radiative transfer calculations using the aerosol optical thickness derived from visibility observations indicate that Aerosol Radiation Interaction (ARI) is a strong candidate to explain the upward trend in the clear-sky radiation. Aerosol Cloud Interaction (ACI) may have some impact on cloud-base radiation, but it is suggested that decadal changes in cloud thickness and synoptic scale changes in cloud amount also play an important role.

Longwave Radiation Corrections for the OMNI Buoy Network

2021 ◽  
Keyword(s):  
Indian Ocean ◽  
Longwave Radiation ◽  
Field Measurements ◽  
North Indian Ocean ◽  
Shortwave Radiation ◽  
Data Logger ◽  
Clear Sky ◽  
The Difference ◽  
Radiation Measurements ◽  
Moored Buoy

Abstract The inception of a moored buoy network in the northern Indian Ocean in 1997 paved the way for systematic collection of longterm time series observations of meteorological and oceanographic parameters. This buoy network was revamped in 2011 with OMNI (Ocean Moored buoy Network for north Indian Ocean) buoys fitted with additional sensors to better quantify the air-sea fluxes. An inter-comparison of OMNI buoy measurements with the nearby WHOI mooring during the year 2015 revealed an overestimation of downwelling longwave radiation (LWR↓). Analysis of the OMNI and WHOI radiation sensors at a test station at NIOT during 2019 revealed that the accurate and stable amplification of the thermopile voltage records along with the customized data logger in the WHOI system results in better estimations of LWR↓. The offset in NIOT measured LWR↓ is estimated firstly by segregating the LWR↓ during clear sky conditions identified using the downwelling shortwave radiation measurements from the same test station, and secondly, finding the offset by taking the difference with expected theoretical clear sky LWR↓. The corrected LWR↓ exhibited good agreement with that of collocated WHOI measurements, with a correlation of 0.93. This method is applied to the OMNI field measurements and again compared with the nearby WHOI mooring measurements, exhibiting a better correlation of 0.95. This work has led to the revamping of radiation measurements in OMNI buoys and provides a reliable method to correct past measurements and improve estimation of air-sea fluxes in the Indian Ocean.

scholarly journals The effect of South American biomass burning aerosol emissions on the regional climate

2018 ◽  
Vol 18 (8) ◽  
pp. 5321-5342 ◽  
Author(s):  
Gillian D. Thornhill ◽  
Claire L. Ryder ◽  
Eleanor J. Highwood ◽  
Len C. Shaffrey ◽  
Ben T. Johnson
Keyword(s):  
Biomass Burning ◽  
Cloud Cover ◽  
Regional Climate ◽  
Shortwave Radiation ◽  
South American ◽  
The South ◽  
Clear Sky ◽  
Peak Biomass ◽  
Biomass Burning Aerosol ◽  
The Difference

Abstract. The impact of biomass burning aerosol (BBA) on the regional climate in South America is assessed using 30-year simulations with a global atmosphere-only configuration of the Met Office Unified Model. We compare two simulations of high and low emissions of biomass burning aerosol based on realistic interannual variability. The aerosol scheme in the model has hygroscopic growth and optical properties for BBA informed by recent observations, including those from the recent South American Biomass Burning Analysis (SAMBBA) intensive aircraft observations made during September 2012. We find that the difference in the September (peak biomass emissions month) BBA optical depth between a simulation with high emissions and a simulation with low emissions corresponds well to the difference in the BBA emissions between the two simulations, with a 71.6 % reduction from high to low emissions for both the BBA emissions and the BB AOD in the region with maximum emissions (defined by a box of extent 5–25∘ S, 40–70∘ W, used for calculating mean values given below). The cloud cover at all altitudes in the region of greatest BBA difference is reduced as a result of the semi-direct effect, by heating of the atmosphere by the BBA and changes in the atmospheric stability and surface fluxes. Within the BBA layer the cloud is reduced by burn-off, while the higher cloud changes appear to be responding to stability changes. The boundary layer is reduced in height and stabilized by increased BBA, resulting in reduced deep convection and reduced cloud cover at heights of 9–14 km, above the layer of BBA. Despite the decrease in cloud fraction, September downwelling clear-sky and all-sky shortwave radiation at the surface is reduced for higher emissions by 13.77 ± 0.39 W m−2 (clear-sky) and 7.37 ± 2.29 W m−2 (all-sky), whilst the upwelling shortwave radiation at the top of atmosphere is increased in clear sky by 3.32 ± 0.09 W m−2, but decreased by -1.36±1.67 W m−2 when cloud changes are included. Shortwave heating rates increase in the aerosol layer by 18 % in the high emissions case. The mean surface temperature is reduced by 0.14 ± 0.24 ∘C and mean precipitation is reduced by 14.5 % in the peak biomass region due to both changes in cloud cover and cloud microphysical properties. If the increase in BBA occurs in a particularly dry year, the resulting reduction in precipitation may exacerbate the drought. The position of the South Atlantic high pressure is slightly altered by the presence of increased BBA, and the strength of the southward low-level jet to the east of the Andes is increased. There is some evidence that some impacts of increased BBA persist through the transition into the monsoon, particularly in precipitation, but the differences are only statistically significant in some small regions in November. This study therefore provides an insight into how variability in deforestation, realized through variability in biomass burning emissions, may contribute to the South American climate, and consequently on the possible impacts of future changes in BBA emissions.

scholarly journals Evaluation of Parameterizations of Incoming Longwave Radiation in the High-Mountain Region of the Tibetan Plateau

2017 ◽  
Vol 56 (4) ◽  
pp. 833-848 ◽  
Author(s):  
Meilin Zhu ◽  
Tandong Yao ◽  
Wei Yang ◽  
Baiqing Xu ◽  
Xiaojun Wang
Keyword(s):  
Tibetan Plateau ◽  
Longwave Radiation ◽  
Cloud Base ◽  
High Mountain ◽  
The Tibetan Plateau ◽  
Mountain Regions ◽  
Local Conditions ◽  
Clear Sky ◽  
The Difference ◽  
Study Sites

AbstractAccurate evaluations of incoming longwave radiation (Lin) parameterization have practical implications for glacier and river runoff changes in high-mountain regions of the Tibetan Plateau (TP). To identify potential means of accurately predicting spatiotemporal variations in Lin, 13 clear-sky parameterizations combined with 10 cloud corrections for all-sky atmospheric emissivity were evaluated at five sites in high-mountain regions of the TP through temporal and spatial parameter transfer tests. Most locally calibrated parameterizations for clear-sky and all-sky conditions performed well when applied to the calibration site. The best parameterization at five sites is Dilley and O’Brien’s A model combined with Sicart et al.’s A for cloud-correction-incorporated relative humidity. The performance of parameter transferability in time is better than that in space for the same all-sky parameterizations. The performance of parameter transferability in space presents spatial discrepancies. In addition, all all-sky parameterizations show a decrease in performance with increasing altitude regardless of whether the parameters of all-sky parameterizations were recalibrated by local conditions or transferred from other study sites. This may be attributable to the difference between screen-level air temperature and the effective atmospheric boundary layer temperature and to different cloud-base heights. Nevertheless, such worse performance at higher altitudes is likely to change because of terrain, underlying surfaces, and wind systems, among other factors. The study also describes possible spatial characteristics of Lin and its driving factors by reviewing the few studies about Lin for the mountain regions of the TP.

scholarly journals Illustrating the benefit of using hourly monitoring data on secondary inorganic aerosol and its precursors for model evaluation

2010 ◽  
Vol 10 (5) ◽  
pp. 12341-12370 ◽  
Author(s):  
M. Schaap ◽  
R. P. Otjes ◽  
E. P. Weijers
Keyword(s):  
The Netherlands ◽  
Ammonium Nitrate ◽  
Model Evaluation ◽  
Base Line ◽  
Ambient Conditions ◽  
Night Time ◽  
Data Set ◽  
Free Data ◽  
Hourly Data ◽  
Inorganic Aerosol

Abstract. Secondary inorganic aerosol, most notably ammonium nitrate and ammonium sulphate, is an important contributor to ambient particulate mass and provides a means for long range transport of acidifying components. The modelling of the formation and fate of these components is challenging. Especially, the formation of the semi-volatile ammonium nitrate is strongly dependent on ambient conditions and the precursor concentrations. For the first time an hourly artefact free data set from the MARGA instrument is available for the period of a full year (1 August 2007 to 1 August 2008) at Cabauw, the Netherlands. This data set is used to verify the results of the LOTOS-EUROS model. The comparison showed that the model underestimates the SIA levels. Closer inspection revealed that base line values appear well estimated for ammonium and sulphate and that the underestimation predominantly takes place at the peak concentrations. For nitrate the variability towards high concentrations is much better captured, however, a systematic relative underestimation was found. The model is able to reproduce many features of the intra-day variability observed for SIA. Although the model captures the seasonal and average diurnal variation of the SIA components, the modelled variability for the nitrate precursor gas nitric acid is much too large. It was found that the thermodynamic equilibrium module produces a too stable ammonium nitrate in winter and during night time in summer, whereas during the daytime in summer it is too unstable. We recommend to improve the model by verification of the equilibrium module, inclusion of coarse mode nitrate and to address the processes concerning SIA formation combined with a detailed analysis of the data set at hand. The benefit of the hourly data with both particulate and gas phase concentrations is illustrated and a continuation of these measurements may prove to be very useful in future model evaluation and improvement studies. Based on our findings we propose to implement a monitoring strategy using three levels of detail within the Netherlands.

scholarly journals Illustrating the benefit of using hourly monitoring data on secondary inorganic aerosol and its precursors for model evaluation

2011 ◽  
Vol 11 (21) ◽  
pp. 11041-11053 ◽  
Author(s):  
M. Schaap ◽  
R. P. Otjes ◽  
E. P. Weijers
Keyword(s):  
The Netherlands ◽  
Ammonium Nitrate ◽  
Model Evaluation ◽  
Base Line ◽  
Ambient Conditions ◽  
Night Time ◽  
Data Set ◽  
Free Data ◽  
Hourly Data ◽  
Inorganic Aerosol

Abstract. Secondary inorganic aerosol, most notably ammonium nitrate and ammonium sulphate, is an important contributor to ambient particulate mass and provides a means for long range transport of acidifying components. The modelling of the formation and fate of these components is challenging. Especially, the formation of the semi-volatile ammonium nitrate is strongly dependent on ambient conditions and the precursor concentrations. For the first time an hourly artefact free data set from the MARGA instrument is available for the period of a full year (1 August 2007 to 1 August 2008) at Cabauw, the Netherlands. This data set is used to verify the results of the LOTOS-EUROS model. The comparison showed that the model underestimates the SIA levels. Closer inspection revealed that base line values appear well estimated for ammonium and sulphate and that the underestimation predominantly takes place at the peak concentrations. For nitrate the variability towards high concentrations is much better captured, however, a systematic relative underestimation was found. The model is able to reproduce many features of the intra-day variability observed for SIA. Although the model captures the seasonal and average diurnal variation of the SIA components, the modelled variability for the nitrate precursor gas nitric acid is much too large. It was found that the thermodynamic equilibrium module produces a too stable ammonium nitrate in winter and during night time in summer, whereas during the daytime in summer it is too unstable. We recommend to improve the model by verification of the equilibrium module, inclusion of coarse mode nitrate and to address the processes concerning SIA formation combined with a detailed analysis of the data set at hand. The benefit of the hourly data with both particulate and gas phase concentrations is illustrated and a continuation of these measurements may prove to be very useful in future model evaluation and improvement studies. Based on our findings we propose to implement a monitoring strategy using three levels of detail within the Netherlands.

scholarly journals The Effect of South American Biomass Burning Aerosol Emissions on the Regional Climate

2017 ◽  
Author(s):  
Gillian D. Thornhill ◽  
Claire L. Ryder ◽  
Eleanor J. Highwood ◽  
Len C. Shaffrey ◽  
Ben T. Johnson
Keyword(s):  
Biomass Burning ◽  
Cloud Cover ◽  
Regional Climate ◽  
Shortwave Radiation ◽  
South American ◽  
The South ◽  
Clear Sky ◽  
Peak Biomass ◽  
Biomass Burning Aerosol ◽  
The Difference

Abstract. The impact of biomass burning aerosol (BBA) on the regional climate in South America is assessed using 30 year simulations with a global atmosphere-only configuration of the Met Office Unified Model. We compare two simulations of high and low emissions of biomass burning aerosol based on realistic interannual variability. The aerosol scheme in the model has hygroscopic growth and optical properties for BBA informed by recent observations, including those from the recent South American Biomass Burning Analysis (SAMBBA) intensive aircraft observations made during September 2012. We find that the difference in the September (peak biomass emissions month) BBA optical depth between a simulation with high emissions and a simulation with low emissions corresponds well to the difference in the BBA emissions between the two simulations, with a 70 % reduction from high to low emissions for both the BBA emissions and the BB AOD in the region with maximum emissions (defined by a box of extent 5–25° S, 40–70° W, used for calculating mean values given below). The cloud cover at all altitudes in the region of greatest BBA difference is reduced as a result of the semi-direct effect, by heating of the atmosphere by the BBA and changes in the atmospheric stability and surface fluxes. Within the BBA layer the cloud is reduced by burn-off, while the higher cloud changes appear to be responding to stability changes. The boundary layer is reduced in height and stabilised by increased BBA, resulting in reduced deep convection and reduced cloud cover at heights of 9–14 km, above the layer of BBA. Despite the decrease in cloud fraction, September downwelling clear-sky and all-sky shortwave radiation at the surface is reduced for higher emissions (by 13.79 W m−2 clear-sky, 7.42 W m−2 all-sky) whilst the upwelling shortwave radiation at the top of atmosphere is increased in clear sky by 3.33 W m−2, but decreased by −1.32 W m−2 when cloud changes are included. Shortwave heating rates increase in the aerosol layer by 18 % in the high emissions case. The mean surface temperature is reduced by 0.14 °C and mean precipitation is reduced by 15 % in the peak biomass region due to both changes in cloud cover and cloud microphysical properties. If the increase in BBA occurs in a particularly dry year, the resulting reduction in precipitation may exacerbate the drought. The position of the South Atlantic High pressure is slightly altered by the presence of increased BBA and the strength of the southward low level jet to the east of the Andes is increased. There is some evidence that some impacts of increased BBA persist through the transition into the monsoon, particularly in precipitation, but the differences are only statistically significant in some small regions in November. This study therefore provides an insight into how variability in deforestation and biomass burning emissions may contribute to the South American climate, and consequently on the possible impacts of future changes in BBA emissions.

Difference Fourier Analysis of Glucose Embedded and Frozen Hydrated Purple Membrane

1982 ◽  
Vol 40 ◽  
pp. 74-75
Author(s):  
Jules S. Jaffe ◽  
Robert M. Glaeser
Keyword(s):  
Purple Membrane ◽  
Data Set ◽  
High Resolution Data ◽  
X Ray ◽  
X Ray Crystallography ◽  
Fourier Techniques ◽  
Versus Protein ◽  
The Difference ◽  
Difference Fourier ◽  
Ideal Method

Although difference Fourier techniques are standard in X-ray crystallography it has only been very recently that electron crystallographers have been able to take advantage of this method. We have combined a high resolution data set for frozen glucose embedded Purple Membrane (PM) with a data set collected from PM prepared in the frozen hydrated state in order to visualize any differences in structure due to the different methods of preparation. The increased contrast between protein-ice versus protein-glucose may prove to be an advantage of the frozen hydrated technique for visualizing those parts of bacteriorhodopsin that are embedded in glucose. In addition, surface groups of the protein may be disordered in glucose and ordered in the frozen state. The sensitivity of the difference Fourier technique to small changes in structure provides an ideal method for testing this hypothesis.

Evaluation of net shortwave radiation over China with a regional climate model

2020 ◽  
Vol 80 (2) ◽  
pp. 147-163
Author(s):  
X Liu ◽  
Y Kang ◽  
Q Liu ◽  
Z Guo ◽  
Y Chen ◽  
...  
Keyword(s):  
Regional Climate Model ◽  
Climate Model ◽  
Regional Climate ◽  
Radiant Energy ◽  
Energy System ◽  
Radiation Budget ◽  
Shortwave Radiation ◽  
Monsoon Region ◽  
Clear Sky ◽  
Sky Conditions

The regional climate model RegCM version 4.6, developed by the European Centre for Medium-Range Weather Forecasts Reanalysis, was used to simulate the radiation budget over China. Clouds and the Earth’s Radiant Energy System (CERES) satellite data were utilized to evaluate the simulation results based on 4 radiative components: net shortwave (NSW) radiation at the surface of the earth and top of the atmosphere (TOA) under all-sky and clear-sky conditions. The performance of the model for low-value areas of NSW was superior to that for high-value areas. NSW at the surface and TOA under all-sky conditions was significantly underestimated; the spatial distribution of the bias was negative in the north and positive in the south, bounded by 25°N for the annual and seasonal averaged difference maps. Compared with the all-sky condition, the simulation effect under clear-sky conditions was significantly better, which indicates that the cloud fraction is the key factor affecting the accuracy of the simulation. In particular, the bias of the TOA NSW under the clear-sky condition was <±10 W m-2 in the eastern areas. The performance of the model was better over the eastern monsoon region in winter and autumn for surface NSW under clear-sky conditions, which may be related to different levels of air pollution during each season. Among the 3 areas, the regional average biases overall were largest (negative) over the Qinghai-Tibet alpine region and smallest over the eastern monsoon region.

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