The formation of ice in clouds is an important process in mixed-phase clouds, and the radiative properties and dynamical developments of clouds strong…The formation of ice in clouds is an important process in mixed-phase clouds, and the radiative properties and dynamical developments of clouds strongly depend on their partitioning between the liquid and ice phases. In this study, we investigated the sensitivities of the cloud phase to the ice-nucleating particle (INP) concentration and thermodynamics. Moreover, passive satellite retrieval algorithms and cloud products were evaluated to identify whether they could detect cloud microphysical and thermodynamical perturbations. Experiments were conducted using the ICOsahedral Nonhydrostatic (ICON) model at the convection-permitting resolution of about 1.2 km on a domain covering significant parts of central Europe, and they were compared to two different retrieval products based on Spinning Enhanced Visible and InfraRed Imager (SEVIRI) measurements. We selected a day with multiple isolated deep convective clouds, reaching a homogeneous freezing temperature at the cloud top. The simulated cloud liquid pixel fractions were found to decrease with increasing INP concentration, both within clouds and at the cloud top. The decrease in the cloud liquid pixel fraction was not monotonic and was stronger in high-INP cases. Cloud-top glaciation temperatures shifted toward warmer temperatures with an increasing INP concentration by as much as 8 ∘C. Moreover, the impact of the INP concentration on cloud-phase partitioning was more pronounced at the cloud top than within the cloud. Furthermore, initial and lateral boundary temperature fields were perturbed with increasing and decreasing temperature increments from 0 to ±3 and ±5 K between 3 and 12 km, respectively. Perturbing the initial thermodynamic state was also found to systematically affect the cloud-phase distribution. However, the simulated cloud-top liquid pixel fraction, diagnosed using radiative transfer simulations as input to a satellite forward operator and two different satellite remote-sensing retrieval algorithms, deviated from one of the satellite products regardless of perturbations in the INP concentration or the initial thermodynamic state for warmer subzero temperatures while agreeing with the other retrieval scheme much better, in particular for the high-INP and high-CAPE (convective available potential energy) scenarios. Perturbing the initial thermodynamic state, which artificially increases the instability of the mid- and upper-troposphere, brought the simulated cloud-top liquid pixel fraction closer to the satellite observations, especially in the warmer mixed-phase temperature range.more
Regional hydrological cycle responding to rising temperatures can have significant influences on society and human activities. We suggest a new perspe…Regional hydrological cycle responding to rising temperatures can have significant influences on society and human activities. We suggest a new perspective on East Asia’s enhanced precipitation amount that emphasizes the role of Siberian surface warming. Increased vegetation greenness in late spring and early summer in eastern Siberia, which may be a response to global warming, acts to warm the surface by reducing the surface albedo with an increase in net absorbed shortwave radiation. Subsequently, eastern Siberia warming leads to the strengthening of anti-cyclonic atmospheric circulation over inner East Asia as well as the subtropical western North Pacific high via thermal forcing and the enhanced land-sea thermal contrast, respectively. Consequently, the anticyclonic circulation over inner East Asia transports much drier and cooler air to southern East Asia. This leads to favorable conditions for increased precipitation in combination with an increased tropical moisture flux from the subtropical western North Pacific high. Therefore, continuous Siberian vegetation growth has a potential influence on the future precipitation amount in the subtropics through vegetation–atmosphere coupled processes.more
Abstract. Long-term gridded precipitation products are crucial for several
applications in hydrology, agriculture and climate sciences. Currently
avai…Abstract. Long-term gridded precipitation products are crucial for several
applications in hydrology, agriculture and climate sciences. Currently
available precipitation products suffer from space and time inconsistency
due to the non-uniform density of ground networks and the difficulties in
merging multiple satellite sensors. The recent “bottom-up” approach that
exploits satellite soil moisture observations for estimating rainfall
through the SM2RAIN (Soil Moisture to Rain) algorithm is suited to build a consistent rainfall data
record as a single polar orbiting satellite sensor is used. Here we exploit the Advanced SCATterometer (ASCAT) on board three Meteorological Operational (MetOp)
satellites, launched in 2006, 2012, and 2018, as part of the European Organisation for the Exploitation of
Meteorological Satellites (EUMETSAT) Polar
System programme. The continuity of the scatterometer sensor is ensured
until the mid-2040s through the MetOp Second Generation Programme. Therefore, by
applying the SM2RAIN algorithm to ASCAT soil moisture observations, a long-term
rainfall data record will be obtained, starting in 2007 and lasting until the mid-2040s. The
paper describes the recent improvements in data pre-processing, SM2RAIN
algorithm formulation, and data post-processing for obtaining the
SM2RAIN–ASCAT quasi-global (only over land) daily rainfall data record at a
12.5 km spatial sampling from 2007 to 2018. The quality of the SM2RAIN–ASCAT data record
is assessed on a regional scale through comparison with high-quality
ground networks in Europe, the United States, India, and Australia. Moreover, an
assessment on a global scale is provided by using the triple-collocation (TC)
technique allowing us also to compare these data with the latest, fifth-generation European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis
(ERA5), the Early Run version of the Integrated Multi-Satellite Retrievals
for Global Precipitation Measurement (IMERG), and the gauge-based Global
Precipitation Climatology Centre (GPCC) products. Results show that the SM2RAIN–ASCAT rainfall data record performs relatively
well at both a regional and global scale, mainly in terms of root mean square
error (RMSE) when compared to other products. Specifically, the SM2RAIN–ASCAT data
record provides performance better than IMERG and GPCC in data-scarce
regions of the world, such as Africa and South America. In these areas, we
expect larger benefits in using SM2RAIN–ASCAT for hydrological and
agricultural applications. The limitations of the SM2RAIN–ASCAT data record consist
of the underestimation of peak rainfall events and the presence of
spurious rainfall events due to high-frequency soil moisture fluctuations
that might be corrected in the future with more advanced bias correction
techniques. The SM2RAIN–ASCAT data record is freely available at
https://doi.org/10.5281/zenodo.3405563 (Brocca et al., 2019) (recently extended to the end of
August 2019).more
Photosynthetically active radiation (PAR) is the 400–700 nm portion of the solar radiation spectrum that photoautotrophic organisms including plants, …Photosynthetically active radiation (PAR) is the 400–700 nm portion of the solar radiation spectrum that photoautotrophic organisms including plants, algae, and cyanobacteria use for photosynthesis. PAR is a key variable in global ecosystem and Earth system modeling, playing a prominent role in carbon and water cycling. Alongside air temperature, water availability, and atmospheric CO2 concentration, PAR controls photosynthesis and consequently biomass productivity in general. The management of agricultural and horticultural crops, forests, grasslands, and even grasses at sports venues is a non-exhaustive list of applications for which an accurate knowledge of the PAR resource is desirable. Modern agrivoltaic systems also require a good knowledge of PAR in conjunction with the variables needed to monitor the co-located photovoltaic system. In situ quality-controlled PAR sensors provide high-quality information for specific locations. However, due to associated installation and maintenance costs, such high-quality data are relatively scarce and generally extend over a restricted and sometimes non-continuous period. Numerous studies have already demonstrated the potential offered by surface radiation estimates based on satellite information as reliable alternatives to in situ measurements. The accuracy of these estimations is site-dependent and is related, for example, to the local climate, landscape, and viewing angle of the satellite. To assess the accuracy of PAR satellite models, we inter-compared 11 methods for estimating 30 min surface PAR based on satellite-derived estimations at 33 ground-based station locations over several climate regions in Europe, Africa, and South America. Averaged across stations, the results showed average relative biases (relative to the measurement mean) across methods of 1 to 20%, an average relative standard deviation of 25 to 30%, an average relative root mean square error of 25% to 35% and a correlation coefficient always above 0.95 for all methods. Improved performance was seen for all methods at relatively cloud-free sites, and quality degraded towards the edge of the Meteosat Second Generation viewing area. A good compromise between computational time, memory allocation, and performance was achieved for most locations using the Jacovides coefficient applied to the global horizontal irradiance from HelioClim-3 or the CAMS Radiation Service. In conclusion, satellite estimations can provide a reliable alternative estimation of ground-based PAR for most applications.more
The present work investigated the performance of an isotropic (Liu–Jordan, L–J) and an anisotropic (Hay) model in assessing the solar energy potential…The present work investigated the performance of an isotropic (Liu–Jordan, L–J) and an anisotropic (Hay) model in assessing the solar energy potential of Saudi Arabia. Three types of solar collectors were considered: with southward fixed-tilt (mode (i)), with fixed-tilt tracking the Sun (mode (ii)), and with varying-tilt tracking the Sun (mode (iii)). This was the first time such a study was conducted for Saudi Arabia. The average annual difference between anisotropic (Hay) and isotropic (L–J) estimates is least ≈38 kWhm−2 year−1 over Saudi Arabia for mode (i), and therefore, the L–J model can be used effectively. In modes (ii) and (iii), the difference is greater (≈197 and ≈226 kWhm−2 year−1, respectively). It is, then, up to the solar energy engineer to decide which model is to be used, but it is recommended that the Hay model be utilised for mode-(iii) solar collectors. These results fill a research gap about the suitability of models in practice. An interesting feature for the ratio of the annual mean solar energy yield of Hay over L–J as function of the latitude, φ, and the ground albedo, ρr, is the formation of a “well” for 29° ≤ φ ≤ 31° and 1.15 ≤ ρr ≤ 1.more
Sixteen years (July 2003–July 2019) of ground-based measurements of total ozone in the urban environment of Athens, Greece, are analyzed in this work.…Sixteen years (July 2003–July 2019) of ground-based measurements of total ozone in the urban environment of Athens, Greece, are analyzed in this work. Measurements were acquired with a single Brewer monochromator operating on the roof of the Biomedical Research Foundation of the Academy of Athens since July 2003. We estimate a 16-year climatological mean of total ozone in Athens of about 322 DU, with no significant change since 2003. Ozone data from the Brewer spectrophotometer were compared with TOMS, OMI, and GOME-2A satellite retrievals. The results reveal excellent correlations between the ground-based and satellite ozone measurements greater than 0.9. The variability of total ozone over Athens related to the seasonal cycle, the quasi biennial oscillation (QBO), the El Nino Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO), the 11-year solar cycle, and tropopause pressure variability is presented.more
A smart and decentralized electrical system, powered by grid-connected renewable energy (RE) with a reliable storage system, has the potential to chan…A smart and decentralized electrical system, powered by grid-connected renewable energy (RE) with a reliable storage system, has the potential to change the future socio-economic dynamics. Climate change may, however, affect the potential of RE and its related technologies. This study investigated the impact of climate change on photovoltaic cells’ temperature response and energy potential under two CO2 emission scenarios, RCP2.6 and 8.5, for the near future (2024–2040) and mid-century (2041–2065) in Togo. An integrated Regional Climate Model version 4 (RegCM4) from the CORDEX-CORE initiative datasets has been used as input. The latter platform recorded various weather variables, such as solar irradiance, air temperature, wind speed and direction, and relative humidity. Results showed that PV cells’ temperature would likely rise over all five regions in the country and may trigger a decline in the PV potential under RCP2.6 and 8.5. However, the magnitude of the induced change, caused by the changing climate, depended on two major factors: (1) the PV technology and (2) geographical position. Results also revealed that these dissimilarities were more pronounced under RCP8.5 with the amorphous technology. It was further found that, nationally, the average cell temperature would have risen by 1 °C and 1.82 °C under RCP2.6 and 8.5, in that order, during the 2024–2065 period for a-Si technology. Finally, the PV potential would likely decrease, on average, by 0.23% for RCP2.6 and 0.4% for RCP8.5 for a-Si technology.more