An integrated approach toward the incorporation of clouds in the temperature retrievals from microwave measurements

In this paper, we address the characterization of clouds and its inclusion in microwave retrievals in order to study its effect on tropospheric temperature profiles measured by TEMPERA radiometer. TEMPERA is the first ground-based microwave radiometer that makes it possible to obtain temperature profiles in the troposphere and stratosphere at the same time. In order to characterize the clouds a multi-instrumental approach has been adopted. Cloud base altitudes were detected using ceilometer measurements while the integrated liquid water was measured by TROWARA radiometer. Both instruments are co-located with TEMPERA in Bern (Switzerland). Using this information and a constant Liquid Water Content value inside the cloud a liquid profile is provided to characterize the clouds in the inversion algorithm. Microwave temperature profiles have been obtained incorporating this water liquid profile in the inversion algorithm and also without considering the clouds, in order to assess its effect on the retrievals. The results have been compared with the temperature profiles from radiosondes which are launched twice a day at the aerological station of MeteoSwiss in Payerne (40 km W of Bern). Almost 1 year of data have been analysed and 60 non-precipitating cloud cases were studied. The statistical analysis carried out over all the cases evidenced that temperature retrievals improved in most of the cases when clouds were incorporated in the inversion algorithm

Intercomparison of stratospheric temperature profiles from a ground-based microwave radiometer with other techniques

In this work the stratospheric performance of a relatively new microwave temperature radiometer (TEMPERA) has been evaluated. With this goal in mind, almost 3 years of temperature measurements (January 2014–September 2016) from the TEMPERA radiometer were intercompared with simultaneous measurements from other techniques: radiosondes, MLS satellite and Rayleigh lidar. This intercomparison campaign was carried out at the aerological station of MeteoSwiss at Payerne (Switzerland). In addition, the temperature profiles from TEMPERA were used to validate the temperature outputs from the SD-WACCM model. The results showed in general a very good agreement between TEMPERA and the different instruments and the model, with a high correlation (higher than 0.9) in the temperature evolution at different altitudes between TEMPERA and the different data sets. An annual pattern was observed in the stratospheric temperature with generally higher temperatures in summer than in winter and with a higher variability during winter. A clear change in the tendency of the temperature deviations was detected in summer 2015, which was due to the repair of an attenuator in the TEMPERA spectrometer. The mean and the standard deviations of the temperature differences between TEMPERA and the different measurements were calculated for two periods (before and after the repair) in order to quantify the accuracy and precision of this radiometer over the campaign period. The results showed absolute biases and standard deviations lower than 2 K for most of the altitudes. In addition, comparisons proved the good performance of TEMPERA in measuring the temperature in the stratosphere

Spatiotemporal changes in aerosol properties by hygroscopic growth and impacts on radiative forcing and heating rates during DISCOVER-AQ 2011

This research has been supported by the H2020 Marie Sklodowska-Curie Actions (grant no. 778349), the Spanish Ministry of Economy and Competitiveness (RTI2018101154.A.I00), and by the Russian Science Foundation (project 2117-00114, entitled Development of lidar retrieval algorithms).This work focuses on the characterization of vertically resolved aerosol hygroscopicity properties and their direct radiative effects through a unique combination of ground-based and airborne remote sensing measurements during the Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) 2011 field campaign in the Baltimore-Washington DC metropolitan area. To that end, we combined aerosol measurements from a multiwavelength Raman lidar located at NASA Goddard Space Flight Center and the airborne NASA Langley High Spectral Resolution Lidar-1 (HSRL-1) lidar system. In situ measurements aboard the P-3B airplane and ground-based Aerosol Robotic Network - Distributed Regional Aerosol Gridded Observational Network (AERONET-DRAGON) served to validate and complement quantifications of aerosol hygroscopicity from lidar measurements and also to extend the study both temporally and spatially. The focus here is on 22 and 29 July 2011, which were very humid days and characterized by a stable atmosphere and increasing relative humidity with height in the planetary boundary layer (PBL). Combined lidar and radiosonde (temperature and water vapor mixing ratio) measurements allowed the retrieval of the Hanel hygroscopic growth factor which agreed with that obtained from airborne in situ measurements and also explained the significant increase of extinction and backscattering with height. Airborne measurements also confirmed aerosol hygroscopicity throughout the entire day in the PBL and identified sulfates and water-soluble organic carbon as the main species of aerosol particles. The combined Raman and HSRL-1 measurements permitted the inversion for aerosol microphysical properties revealing an increase of particle radius with altitude consistent with hygroscopic growth. Aerosol hygroscopicity pattern served as a possible explanation of aerosol optical depth increases during the day, particularly for fine-mode particles. Lidar measurements were used as input to the libRadtran radiative transfer code to obtain vertically resolved aerosol radiative effects and heating rates under dry and humid conditions, and the results reveal that aerosol hygroscopicity is responsible for larger cooling effects in the shortwave range (7-10 W m(-2) depending on aerosol load) near the ground, while heating rates produced a warming of 0.12 K d(-1) near the top of PBL where aerosol hygroscopic growth was highest.H2020 Marie Sklodowska-Curie Actions 778349Spanish Ministry of Economy and Competitiveness RTI2018101154.A.I00Russian Science Foundation (RSF) 2117-0011

Long-term observations minus background monitoring of ground-based brightness temperatures from a microwave radiometer network

Abstract. Ground-based microwave radiometers (MWRs) offer the capability to provide continuous, high-temporal-resolution observations of the atmospheric thermodynamic state in the planetary boundary layer (PBL) with low maintenance. This makes MWR an ideal instrument to supplement radiosonde and satellite observations when initializing numerical weather prediction (NWP) models through data assimilation. State-of-the-art data assimilation systems (e.g. variational schemes) require an accurate representation of the differences between model (background) and observations, which are then weighted by their respective errors to provide the best analysis of the true atmospheric state. In this perspective, one source of information is contained in the statistics of the differences between observations and their background counterparts (O–B). Monitoring of O–B statistics is crucial to detect and remove systematic errors coming from the measurements, the observation operator, and/or the NWP model. This work illustrates a 1-year O–B analysis for MWR observations in clear-sky conditions for an European-wide network of six MWRs. Observations include MWR brightness temperatures (TB) measured by the two most common types of MWR instruments. Background profiles are extracted from the French convective-scale model AROME-France before being converted into TB. The observation operator used to map atmospheric profiles into TB is the fast radiative transfer model RTTOV-gb. It is shown that O–B monitoring can effectively detect instrument malfunctions. O–B statistics (bias, standard deviation, and root mean square) for water vapour channels (22.24–30.0 GHz) are quite consistent for all the instrumental sites, decreasing from the 22.24 GHz line centre ( ∼  2–2.5 K) towards the high-frequency wing ( ∼  0.8–1.3 K). Statistics for zenith and lower-elevation observations show a similar trend, though values increase with increasing air mass. O–B statistics for temperature channels show different behaviour for relatively transparent (51–53 GHz) and opaque channels (54–58 GHz). Opaque channels show lower uncertainties (< 0.8–0.9 K) and little variation with elevation angle. Transparent channels show larger biases ( ∼  2–3 K) with relatively low standard deviations ( ∼  1–1.5 K). The observations minus analysis TB statistics are similar to the O–B statistics, suggesting a possible improvement to be expected by assimilating MWR TB into NWP models. Lastly, the O–B TB differences have been evaluated to verify the normal-distribution hypothesis underlying variational and ensemble Kalman filter-based DA systems. Absolute values of excess kurtosis and skewness are generally within 1 and 0.5, respectively, for all instrumental sites, demonstrating O–B normal distribution for most of the channels and elevations angles

Monitoring of the Eyjafjallajökull volcanic aerosol plume over the Iberian Peninsula by means of four EARLINET lidar stations

Lidar and sun-photometer measurements were performed intensively over the Iberian Peninsula (IP) during the eruption of the Eyjafjallajökull volcano (Iceland) in April–May 2010. The volcanic plume reached all the IP stations for the first time on 5 May 2010. A thorough study of the event was conducted for the period 5–8 May. Firstly, the spatial and temporal evolution of the plume was described by means of lidar and sun-photometer measurements supported with backtrajectories. The volcanic aerosol layers observed over the IP were rather thin (<1000 m) with a top height up to 11–12 km. However, in some cases at the beginning of the period the thickness of those layers reached several kilometers in Évora and Madrid. The optical thicknesses associated to those layers were rather low (between 0.013 and 0.020 in average over the whole period), with peak values near 0.10 detected on 7 May. Secondly, the volcanic aerosols were characterized in terms of extinction and backscatter coefficients, lidar ratios, Ångström exponents and linear particle depolarization ratio. Lidar ratios at different sites varied between 30 and 50 sr without a marked spectral dependency. Similar extinction-related Ångström exponents varying between 0.6 and 0.8 were observed at different sites. The temporal evolution of the backscatter-related Ångström exponents points out a possible decrease of the volcanic particle size as the plume moved from west to east. Particle depolarization ratios on the order of 0.06–0.08 confirmed the coexistence of both ash and non-ash particles. Additionally, profiles of mass concentration were obtained with a method using the opposite depolarizing effects of ash particles (strongly depolarizing), non-ash particles (very weakly depolarizing), and sun-photometer observations. In Granada the ash mass concentration was found to be approximately 1.5 times higher than that of non-ash particles, and probably did not exceed the value of 200 μg m−3 during the whole event.This work is supported by the 7th Framework Programme project Aerosols, Clouds, and Trace Gases Research Infrastructure Network (ACTRIS) (grant agreement no. 262254); by the MICINN (Spanish Ministry of Science and Innovation) and FEDER funds under the project TEC2009-09106/TEC and UNPC10-4E-442, and the Complementary Actions CGL2010- 09225-E and CGL2011-13580-E/CLI; by the Spanish Ministry of Education under the project PR2011-0358. It has also been supported by FCT (Fundac˜ao para a Ciˆencia e a Tecnologia) through the National Re-equipment Program REDE/1527/RNG/2007. Jana Preißler was funded by FCT (grant SFRH/BD/47521/2008). Juan Luis Guerrero-Rascado was partially funded by FCT (grant SFRH/BPD/63090/2009) and by the Spanish Ministry of Education (grant EX2009-0700)

Inter-relations of precipitation, aerosols, and clouds over Andalusia, southern Spain, revealed by the Andalusian Global ObseRvatory of the Atmosphere (AGORA)

The south-central interior of Andalusia experiences intricate precipitation patterns as a result of its semi-arid Mediterranean climate and the impact of Saharan dust and human-made pollutants. The primary aim of this study is to monitor the inter-relations between various factors, such as aerosols, clouds, and meteorological variables, and precipitation systems in Granada using ground-based remote sensing and in situ instruments including a microwave radiometer, ceilometer, cloud radar, nephelometer, and weather station. Over an 11-year period, we detected rain events using a physical retrieval method that employed microwave radiometer measurements. A composite analysis was applied to them to construct a climatology of the temporal evolution of precipitation. It was found that convective rain is the dominant precipitation type in Granada, accounting for 68 % of the rain events. The height of the cloud base is mainly distributed at an altitude of 2 to 7 km. Integrated water vapor (IWV) and integrated cloud liquid water (ILW) increase rapidly before the onset of rain. Aerosol scattering at the surface level and hence the aerosol concentration are reduced during rain, and the predominant mean size distribution of aerosol particles before, during, and after rain is almost the same. A meteorological environment favorable for virga formation is observed in Granada. The surface weather station detected rainfall later than the microwave radiometer, indicating virga according to ceilometer and cloud radar data. We used 889 rain-day events identified by weather station data to determine precipitation intensity classes and found that light rain is the main precipitation intensity class in Granada, accounting for 72 % of the rain-day events. This can be a result of the high tropospheric temperature induced by the Andalusian climate and the reduction of cloud droplet size by the high availability of aerosol particles in the urban atmosphere. This study provides evidence that aerosols, clouds, and meteorological variables have a combined impact on precipitation which can be considered for water resource management and improving rain forecasting accuracy.</p

Monitoring of the Eyjafjalla volcanic plume at four lidar stations over the Iberian Peninsula: 6 to 8 May 2010

Lidar measurements were performed in the framework of the EARLINET and SPALINET networks during the eruption of Eyjafjalla volcano (Iceland) since 14 April 2010. The profiles of the aerosol optical properties, namely backscatter and extinction coefficients, lidar ratio and Angström exponent, show the presence of volcanic aerosol layers over all SPALINET stations since 5 May. The volcanic particles were monitored both within the planetary boundary layer and in decoupled layers up to 8 km agl over the Iberian Peninsula. This is the first time that the spatial and temporal distributions of volcanic aerosols have been studied with active remote sensing techniques over the Iberian Peninsula.Postprint (published version

An overview of the ciao multiparadigm language and program development environment and its design philosophy

We describe some of the novel aspects and motivations behind the design and implementation of the Ciao multiparadigm programming system. An important aspect of Ciao is that it provides the programmer with a large number of useful features from different programming paradigms and styles, and that the use of each of these features can be turned on and off at will for each program module. Thus, a given module may be using e.g. higher order functions and constraints, while another module may be using objects, predicates, and concurrency. Furthermore, the language is designed to be extensible in a simple and modular way. Another important aspect of Ciao is its programming environment, which provides a powerful preprocessor (with an associated assertion language) capable of statically finding non-trivial bugs, verifying that programs comply with specifications, and performing many types of program optimizations. Such optimizations produce code that is highly competitive with other dynamic languages or, when the highest levéis of optimization are used, even that of static languages, all while retaining the interactive development environment of a dynamic language. The environment also includes a powerful auto-documenter. The paper provides an informal overview of the language and program development environment. It aims at illustrating the design philosophy rather than at being exhaustive, which would be impossible in the format of a paper, pointing instead to the existing literature on the system

Stratospheric AOD after the 2011 eruption of Nabro volcano measured by lidars over the Northern Hemisphere

International audienceNabro volcano (13.37°N, 41.70°E) in Eritrea erupted on 13 June 2011 generating a layer of sulfate aerosols that persisted in the stratosphere for months. For the first time we report on ground-based lidar observations of the same event from every continent in the Northern Hemisphere, taking advantage of the synergy between global lidar networks such as EARLINET, MPLNET and NDACC with independent lidar groups and satellite CALIPSO to track the evolution of the stratospheric aerosol layer in various parts of the globe. The globally averaged aerosol optical depth (AOD) due to the stratospheric volcanic aerosol layers was of the order of 0.018 ± 0.009 at 532 nm, ranging from 0.003 to 0.04. Compared to the total column AOD from the available collocated AERONET stations, the stratospheric contribution varied from 2% to 23% at 532 nm