A B S T R A C TThe impact of lakes in numerical weather prediction is investigated in a set of global simulations performed with the ECMWF Integrated Forecasting System (IFS). A Fresh shallow-water Lake model (FLake) is introduced allowing the coupling of both resolved and subgrid lakes (those that occupy less than 50% of a grid-box) to the IFS atmospheric model. Global fields for the lake ancillary conditions (namely lake cover and lake depth), as well as initial conditions for the lake physical state, have been derived to initialise the forecast experiments. The procedure for initialising the lake variables is described and verified with particular emphasis on the importance of surface water temperature and freezing conditions. The response of short-range near surface temperature to the representation of lakes is examined in a set of forecast experiments covering one full year. It is shown that the impact of subgrid lakes is beneficial, reducing forecast error over the Northern territories of Canada and over Scandinavia particularly in spring and summer seasons. This is mainly attributed to the lake thermal effect, which delays the temperature response to seasonal radiation forcing.

Abstract. The quality control and monitoring of surface freshwaters is crucial, since some of these water masses constitute essential renewable water resources for a variety of purposes. In addition, changes in the surface water composition may affect the physical properties of lake water, such as temperature, which in turn may impact the interactions of the water surface with the lower atmosphere.The use of satellite remote sensing to estimate the water turbidity of Alqueva reservoir, located in the south of Portugal, is explored. A validation study of the satellite derived water leaving spectral reflectance is firstly presented, using data taken during three field campaigns carried out during 2010 and early 2011. Secondly, an empirical algorithm to estimate lake water surface turbidity from the combination of in situ and satellite measurements is proposed. Finally, the importance of water turbidity on the surface energy balance is tested in the form of a study of the sensitivity of a lake model to the extinction coefficient of water (estimated from turbidity), showing that this is an important parameter that affects the lake surface temperature.

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The study of lake-atmosphere interactions was the main purpose of a 2014 summer experiment at Alqueva reservoir in Portugal. Near-surface fluxes of momentum, heat and mass [water vapour (H 2 O) and carbon dioxide (CO 2 )] were obtained with the new Campbell Scientific's IRGASON Integrated Open-Path CO 2 /H 2 O Gas Analyser and 3D Sonic Anemometer between 2 June and 2 October. On average, the reservoir was releasing energy in the form of sensible and latent heat flux during the study period. At the end of the 75 d, the total evaporation was estimated as 490.26 mm. A high correlation was found between the latent heat flux and the wind speed (R = 0.97). The temperature gradient between air and water was positive between 12 and 21 UTC, causing a negative sensible heat flux, and negative during the rest of the day, triggering a positive sensible heat flux. The reservoir acted as a sink of atmospheric CO 2 with an average rate of −0.026 mg m −2 s −1 . However, at a daily scale we found an unexpected uptake between 0 and 9 UTC and almost null flux between 13 and 19 UTC. Potential reasons for this result are further discussed. The net radiation was recorded for the same period and water column heat storage was estimated using water temperature profiles. The energy balance closure for the analysed period was 81%. In-water solar spectral downwelling irradiance profiles were measured with a new device allowing measurements independent of the solar zenith angle, which enabled the computation of the attenuation coefficient of light in the water column. The average attenuation coefficient for the photosynthetically active radiation spectral region varied from 0.849 ± 0.025 m −1 on 30 July to 1.459 ± 0.007 m −1 on 25 September.

During the 2017 record-breaking burning season in Canada / United States, intense wild fires raged during the first week of September in the Pacific northwestern region (British Columbia, Alberta, Washington, Oregon, Idaho, Montana and northern California) burning mostly temperate coniferous forests. The heavy loads of smoke particles emitted in the atmosphere reached the Iberian Peninsula (IP) a few days later on 7 and 8 September. Satellite imagery allows to identify two main smoke clouds emitted during two different periods that were injected and transported in the atmosphere at several altitude levels. Columnar properties on 7 and 8 September at two Aerosol Robotic Network (AERONET) mid-altitude, background sites in northern and southern Spain are: aerosol optical depth (AOD) at 440 nm up to 0.62, Ångström exponent of 1.6-1.7, large dominance of small particles (fine mode fraction > 0.88), low absorption AOD at 440 nm (<0.008) and large single scattering albedo at 440 nm (>0.98). Profiles from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) show the presence of smoke particles in the stratosphere during the transport, whereas the smoke is only observed in the troposphere at its arrival over the IP. Portuguese and Spanish ground lidar stations from the European Aerosol Research Lidar Network / Aerosols, Clouds, and Trace gases Research InfraStructure Network (EARLINET/ACTRIS) and the Micro-Pulse Lidar NETwork (MPLNET) revealsmoke plumes with different properties: particle depolarization ratio and color ratio, respectively, of 0.05 and 2.5 in the mid troposphere (5 -9 km) and of 0.10 and 3.0 in the upper troposphere (10 -13 km). In the mid troposphere the particle depolarization ratio does not seem time-dependent during the transport whereas the color ratio seems to increase (larger particles sediment first). To analyze the horizontal and vertical transport of the smoke from its origin to the IP, particle dispersion modelling is performed with the Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT) parameterized with satellite-derived biomass burning emission estimates from the Global Fire Assimilation System (GFAS) of the Copernicus Atmosphere Monitoring Service (CAMS). Three compounds are simulated: carbon monoxide, black carbon and organic carbon. The results show that the first smoke plume which travels slowly reaches rapidly (~1 day) the upper troposphere and lower stratosphere (UTLS) but also shows evidence of large scale horizontal dispersion, while the second plume, entrained by strong subtropical jets, reaches the upper troposphere much slower (~2.5 days). Observations and dispersion modelling all together suggest that particle depolarization properties are enhanced during their vertical transport from the mid to the upper troposphere.Keywords. Time-space monitoring, ground-based and space-borne lidars, long-range transport of smoke plume, injection of particles up to the upper troposphere, particle dispersion model, smoke particle absorption and depolarization propert...

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Abstract. Alqueva reservoir located in southeast of Portugal has a surface area of 250 km2 and total capacity of 4150 hm3. Since 2006 the water quality of this reservoir is explored by the authors using remote sensing techniques. First using MERIS multi-spectral radiometer on-board of ENVISAT-1 and presently with MSI multi-spectral radiometer on-board SENTINEL-2. The existence of two satellites (A and B) equipped with MSI enable the area to be revisited, under the same viewing conditions, every 2–3 days. Since 2017 the multidisciplinary project ALOP (ALentejo Observation and Prediction systems) expands the team knowledge about the physical and bio-chemical properties of the reservoir. This project includes an integrated field campaign at different experimental sites in the reservoir and its shores, at least until September 2018. Previous algorithms developed by the team for MERIS are tested with the new MSI instrument for water turbidity, chlorophyll a concentration and density of cyanobacteria. Results from micro-algae bloom occurred in late summer/early autumn 2017 on the reservoir are presented, showing the capabilities of MSI sensor for detection and high resolution mapping over the reservoir. The results are compared with in situ sampling and laboratorial analysis of chlorophyll a associated with the bloom.