17 research outputs found
Assessment of Trends and Uncertainties in the Atmospheric Boundary Layer Height Estimated Using Radiosounding Observations over Europe
Trends in atmospheric boundary layer height may represent an indication of climate changes. The related modified interaction between the surface and free atmosphere affects both thermodynamics variables and dilution of chemical constituents. Boundary layer is also a major player in various feedback mechanisms of interest for climate models. This paper investigates trends in the nocturnal and convective boundary layer height at mid-latitudes in Europe using radiosounding profiles from the Integrated Global Radiosounding Archive (IGRA). Atmospheric data from the European Centre for Medium-Range Weather Forecasts (ECMWF) ReAnalysis v5 (ERA5) and from the GCOS Reference Upper-Air Network (GRUAN) Lindenberg station are used as intercomparison datasets for the study of structural and parametric uncertainties in the trend analysis. Trends are calculated after the removal of the lag-1 autocorrelation term for each time series. The study confirms the large differences reported in literature between the boundary layer height estimates obtained with the two different algorithms used for IGRA and ERA5 data: ERA5 shows a density distribution with median values of 350 m and 1150 m for the night and the daytime data, respectively, while the corresponding IGRA median values are of 1150 m and 1750 m. An overall good agreement between the estimated trends is found for nighttime data, while daytime ERA5 boundary layer height estimates over Europe are characterized by a lower spatial homogeneity than IGRA. Parametric uncertainties due to missing data in both the time and space domain are also investigated: the former is not exceeding 1.5 m, while the latter are within 10 m during night and 17 m during the day. Recommendations on dataset filtering based on time series completeness are provided. Finally, the comparison between the Lindenberg data as processed at high-resolution by GRUAN and as provided to IGRA at a lower resolution, shows the significant impact of using high-resolution data in the determination of the boundary layer height, with differences from about 200 m to 450 m for both night and day, as well as a large deviation in the estimated trend
Fully Dynamic High–Resolution Model for Dispersion of Icelandic Airborne Mineral Dust
Icelandic topsoil sediments, as confirmed by numerous scientific studies, represent the largest and the most important European source of mineral dust. Strong winds, connected with the intensive cyclonic circulation in the North Atlantic, induce intense emissions of mineral dust from local sources all year and carry away these fine aerosol particles for thousands of kilometers. Various impacts of airborne mineral dust particles on local air quality, human health, transportation, climate and marine ecosystems motivated us to design a fully dynamic coupled atmosphere–dust numerical modelling system in order to simulate, predict and quantify the Icelandic mineral dust process including: local measurements and source specification over Iceland. In this study, we used the Dust Regional Atmospheric Model (DREAM) with improved Icelandic high resolution dust source specification and implemented spatially variable particle size distribution, variable snow cover and soil wetness. Three case studies of intense short- and long-range transport were selected to evaluate the model performance. Results demonstrated the model’s capability to forecast major transport features, such as timing, and horizontal and vertical distribution of the processes. This modelling system can be used as an operational forecasting system, but also as a reliable tool for assessing climate and environmental Icelandic dust impacts. © 2022 by the authors
Statistical harmonization and uncertainty assessment in the comparison of satellite and radiosonde climate variables
Satellite product validation is a key to ensure the delivery of quality products for climate and weather applications. To do this, a fundamental step is the comparison with other instruments, such as radiosonde. This is especially true for essential climate variables such as temperature and humidity.Thanks to a functional data representation, this paper uses a likelihood-based approach that exploits the measurement uncertainties in a natural way. In particular, the comparison of temperature and humidity radiosonde measurements collected within the network of the Universal Rawinsonde Observation Program (RAOB) and the corresponding atmospheric profiles derived from the infrared atmospheric sounding interferometer aboard MetOp-A and MetOp-B satellites is developed with the aim of understanding the vertical smoothing mismatch uncertainty.Moreover, conventional RAOB functional data representation is assessed by means of a comparison with radiosonde reference measurements given by the Global Climate Observing System (GCOS) Reference Upper-Air Network (GRUAN), which provides high-resolution fully traceable radio-sounding profiles. In this way, the uncertainty related to coarse vertical resolution, or sparseness, of the conventional RAOB is assessed.It has been found that the uncertainty of vertical smoothing mismatch averaged along the profile is 0.50 K for temperature and 0.16 g/kg for water-vapor mixing ratio. Moreover, the uncertainty related to RAOB sparseness, averaged along the profile, is 0.29 K for temperature and 0.13 g/kg for water-vapor mixing ratio
Ceilometer Aerosol Profiling versus Raman Lidar in the Frame of Interact Campaign of Actris
In this paper, multi-wavelength Raman lidar measurements are used to investigate the capability of ceilometers to provide reliable information about atmospheric aerosol properties through the INTERACT (INTERcomparison of Aerosol and Cloud Tracking) campaign carried out at the CNR-IMAA Atmospheric Observatory (760 m a.s.l., 40.60 N, 15.72 E), in the framework of ACTRIS (Aerosol Clouds Trace gases Research InfraStructure) FP7 project. This work is the first time that three different commercial ceilometers with an advanced Raman lidar are compared over a period of six month. The comparison of the attenuated backscatter coefficient profiles from a multi-wavelength Raman lidar and three ceilometers (CHM15k, CS135s, CT25K) reveals differences due to the expected discrepancy in the SNR but also due to effect of changes in the ambient temperature on the stability of ceilometer calibration over short and mid-term. Technological improvements of ceilometers towards their operational use in the monitoring of the atmospheric aerosol in the low and free troposphere are likely needed
Ceilometer Aerosol Profiling versus Raman Lidar in the Frame of Interact Campaign of Actris
In this paper, multi-wavelength Raman lidar measurements are used to investigate the capability of ceilometers to provide reliable information about atmospheric aerosol properties through the INTERACT (INTERcomparison of Aerosol and Cloud Tracking) campaign carried out at the CNR-IMAA Atmospheric Observatory (760 m a.s.l., 40.60 N, 15.72 E), in the framework of ACTRIS (Aerosol Clouds Trace gases Research InfraStructure) FP7 project. This work is the first time that three different commercial ceilometers with an advanced Raman lidar are compared over a period of six month. The comparison of the attenuated backscatter coefficient profiles from a multi-wavelength Raman lidar and three ceilometers (CHM15k, CS135s, CT25K) reveals differences due to the expected discrepancy in the SNR but also due to effect of changes in the ambient temperature on the stability of ceilometer calibration over short and mid-term. Technological improvements of ceilometers towards their operational use in the monitoring of the atmospheric aerosol in the low and free troposphere are likely needed
Quantifying the value of redundant measurements at GCOS Reference Upper-Air Network sites
The potential for measurement redundancy to reduce uncertainty in atmospheric
variables has not been investigated comprehensively for climate observations.
We evaluated the usefulness of entropy and mutual correlation concepts, as
defined in information theory, for quantifying random uncertainty and
redundancy in time series of the integrated water vapour (IWV) and water vapour
mixing ratio profiles provided by five highly instrumented GRUAN (GCOS,
Global Climate Observing System, Reference Upper-Air Network) stations in
2010–2012. Results show that the random uncertainties on the IWV measured
with radiosondes, global positioning system, microwave and infrared
radiometers, and Raman lidar measurements differed by less than 8%.
Comparisons of time series of IWV content from ground-based remote sensing
instruments with in situ soundings showed that microwave radiometers have the
highest redundancy with the IWV time series measured by radiosondes and
therefore the highest potential to reduce the random uncertainty of the
radiosondes time series. Moreover, the random uncertainty of a time series
from one instrument can be reduced by ~ 60% by constraining the
measurements with those from another instrument. The best reduction of random
uncertainty is achieved by conditioning Raman lidar measurements with
microwave radiometer measurements. Specific instruments are recommended for
atmospheric water vapour measurements at GRUAN sites. This approach can be
applied to the study of redundant measurements for other climate variables
Cloud ice caused by atmospheric mineral dust – Part 1: Parameterization of ice nuclei concentration in the NMME-DREAM model
Dust aerosols are very efficient ice nuclei, important for heterogeneous
cloud glaciation even in regions distant from desert sources. A new
generation of ice nucleation parameterizations, including dust as an ice
nucleation agent, opens the way towards a more accurate treatment of cold
cloud formation in atmospheric models. Using such parameterizations, we have
developed a regional dust-atmospheric modelling system capable of predicting,
in real time, dust-induced ice nucleation. We executed the model with the
added ice nucleation component over the Mediterranean region, exposed to
moderate Saharan dust transport, over two periods lasting 15 and 9Â days,
respectively. The model results were compared against satellite and
ground-based cloud-ice-related measurements, provided by SEVIRI (Spinning
Enhanced Visible and InfraRed Imager) and the CNR-IMAA Atmospheric
Observatory (CIAO) in Potenza, southern Italy. The predicted ice nuclei
concentration showed a reasonable level of agreement when compared against
the observed spatial and temporal patterns of cloud ice water. The developed
methodology permits the use of ice nuclei as input into the cloud
microphysics schemes of atmospheric models, assuming that this approach
could improve the predictions of cloud formation and associated
precipitation
Intercomparison of aerosol measurements performed with multi-wavelength Raman lidars, automatic lidars and ceilometers in the framework of INTERACT-II campaign
Following the previous efforts of INTERACT (INTERcomparison of Aerosol and
Cloud Tracking), the INTERACT-II campaign used multi-wavelength Raman lidar
measurements to assess the performance of an automatic compact micro-pulse
lidar (MiniMPL) and two ceilometers (CL51 and CS135) in providing reliable
information about optical and geometric atmospheric aerosol properties. The
campaign took place at the CNR-IMAA Atmospheric Observatory
(760 m a. s. l. ; 40.60° N, 15.72° E) in the
framework of ACTRIS-2 (Aerosol Clouds Trace gases Research InfraStructure)
H2020 project. Co-located simultaneous measurements involving a MiniMPL, two
ceilometers and two EARLINET multi-wavelength Raman lidars were performed
from July to December 2016. The intercomparison highlighted that the MiniMPL
range-corrected signals (RCSs) show, on average, a fractional difference with
respect to those of CNR-IMAA Atmospheric Observatory (CIAO) lidars ranging
from 5 to 15 % below 2.0 km a.s.l. (above sea level), largely
due to the use of an inaccurate overlap correction, and smaller than 5 %
in the free troposphere. For the CL51, the attenuated backscatter values have
an average fractional difference with respect to CIAO
lidars  <  20–30 % below 3 km and larger above. The
variability of the CL51 calibration constant is within ±46 %. For the
CS135, the performance is similar to the CL51 below 2.0 km a. s. l. ,
while in the region above 3 km a. s. l.  the differences are about
±40 %. The variability of the CS135 normalization constant is within
±47 %.Finally, additional tests performed during the campaign using the CHM15k
ceilometer operated at CIAO showed the clear need to investigate the CHM15k
historical dataset (2010–2016) to evaluate potential effects of ceilometer
laser fluctuations on calibration stability. The number of laser pulses shows
an average variability of 10 % with respect to the nominal power which
conforms to the ceilometer specifications. Nevertheless, laser pulses
variability follows seasonal behavior with an increase in the number of laser
pulses in summer and a decrease in winter. This contributes to explain the
dependency of the ceilometer calibration constant on the environmental
temperature hypothesized during INTERACT
The lesson learnt during interact - I and INTERACT - II actris measurement campaigns
The INTERACT-II (INTERcomparison of Aerosol and Cloud Tracking) campaign, performed at the CNR-IMAA Atmospheric Observatory (760 m a.s.l., 40.60° N, 15.72° E), aims to evaluate the performances of commercial automatic lidars and ceilometers for atmospheric aerosol profiling, through the comparison with Potenza EARLINET (European Aerosol Research Lidar NETwork) lidars. The results of the campaign and the overall lesson learnt within INTERACT-I and INTERACT-II ACTRIS campaigns will be presented