An integrated chemistry–climate model (RegCM4-CHEM) simulates present-day climate, ozone and tropospheric aerosols over Egypt with a focus on northern Africa and the Greater Cairo (GC) region. The ...densely populated GC region is known for its severe air quality issues driven by high levels of anthropogenic pollution in conjunction with natural sources such as dust, and agricultural burning events. We find that current global emission inventories underestimate key pollutants such as nitrogen oxides and anthropogenic aerosol species. In the GC region, average ground-based observations of the daily July maximum nitrogen dioxide (NO₂) are 40 to 60 parts per billion by volume (ppbv) and are about 10 ppbv higher than modeled estimates, likely due to model grid cell resolution, improper boundary layer representation, and poor emissions inventories. Observed July daily maximum ozone concentrations range from 30 ppbv (winter) to 90 ppbv (summer). The model reproduces the seasonal cycle fairly well, but modeled July ozone is underestimated by approximately 10 ppbv and exhibits little interannual variability. For aerosols, springtime dust events dominate the seasonal aerosol cycle. The chemistry— climate model captures the springtime peak aerosol optical depth (AOD) of 0.7 to 1 but is slightly greater than satellite-derived AOD. Observed AOD decreases in the summer and increases again in the fall due to agricultural burning events in the Nile Delta; however, the model underestimates this observed AOD peak in fall, as standard emissions inventories underestimate the extent of this burning and the resulting aerosol emissions. Our comparison of modeled gas and particulate phase atmospheric chemistry in the GC region indicates that improved emissions inventories of mobile sources and other anthropogenic activities, specifically NOₓ and organic aerosols, are needed to improve air quality simulations in this region.
Atmospheric turbidity conditions were monitored during the period 1989–1995 in rural and urban sites in Egypt. The rural site (Aswan) is in the south region of Egypt (desert climate), while the urban ...site is greater Cairo (Cairo and its surroundings). The measurements were used to recover the aerosol optical depth, Linke turbidity factor, and Angstrom turbidity indices, from the total direct solar radiation measurements and knowledge of the atmospheric ozone and water vapor content.
Solar direct radiation measurements were carried out with an Eppley pyrheliometer, following World Meteorological Organization recommendations, improving on previous work that made use of Voltz sun photometers. An examination of the methodologies for calculating aerosol optical depth and comparisons to observations suggests that the Davies–Hay method is superior to the method of Unsworth–Monteith.
A comparison of the seasonal cycle of aerosol optical characteristics at both sites showed: aerosol of photochemical origin in the summer; a significant impact of temperature, relative humidity and dust storms in the autumn; low values of aerosol optical characteristics in the winter (due to precipitative removal as well as relative humidity-impacted deposition); and high values in the spring resulting from seasonal dust storms.
An examination of the inter-annual variability of the global direct solar radiation and the anomalous aerosol optical depth at both rural and urban sites showed the signature of both the El-Chichon and Mt. Pinatubo eruptions. The Pinatubo eruption was studied in detail: anomalously high aerosol optical depth (AOD) values and low global direct radiation was observed in mid-1991 over Cairo (AOD average: 0.04) and early 1992 over Aswan (AOD average: 0.039). The annual behavior of the Angstrom turbidity coefficient and Linke turbidity factor recorded maximum values (0.27 and 7.0, respectively) over Cairo in late 1991/early 1992, with maximum values over Aswan being (0.18 and 5.57, respectively) in late 1991.
We investigate the effect of the shortwave radiative forcing of Saharan dust on the West African monsoon with a regional climate model interactively coupled to a dust model. Toward this purpose we ...intercompare sets of 38 summer monsoon season simulations (1969–2006) with and without dust effects over a domain encompassing most of the African continent and adjacent regions. We find that the main effect of the dust radiative shortwave forcing is to reduce precipitation over the Sahel region. This is in response to cooling over the Sahara, which decreases the meridional gradient of moist static energy and results in a weakening of the monsoon energy pump. The dust effects also cause a strengthening of the southern branch of the African Easterly Jet and a weakening of Tropical Easterly Jet. Over the Sahel the dust forcing causes climate response patterns that are similar to those found during dry years over the Sahel, which suggests that Saharan dust feedbacks might have a role in maintaining drought events over the region. Overall, the inclusion of dust also tends to improve the model simulation of the West African monsoon, as well as African and Tropical Easterly jets. This work focuses on climatic feedback associated to shortwave radiation forcing and should be further completed by the study of dust effect on long‐wave radiation.
In an effort to improve our understanding of aerosol impacts on climate, we implement a desert dust module within a regional climate model (RegCM). The dust module includes emission, transport, ...gravitational settling, wet and dry removal and calculations of dust optical properties. The coupled RegCM-dust model is used to simulate two dust episodes observed over the Sahara region (a northeastern Africa dust outbreak, and a west Africa-Atlantic dust outbreak observed during the SHADE "Saharan Dust Experiment"), as well as a three month simulation over an extended domain covering the Africa-Europe sector. Comparisons with satellite and local aerosol optical depth measurements shows that the model captures the main spatial (both horizontal and vertical) and temporal features of the dust distribution. The main model deficiency occurs in the representation of certain dynamical patterns observed during the SHADE case which is associated with an active easterly wave that contributed to the generation of the dust outbreak. The model appears suitable to conduct long term simulations of the effects of Saharan dust on African and European climate.
The ICTP regional climate model (RegCM3) coupled with a desert dust aerosol model is used to simulate the net radiative forcing (short-wave and long-wave) and related climate effects of dust aerosols ...over East Asia. Two sets of experiments are completed and intercompared, one without (Exp. 1) and one with (Exp. 2) the radiative effects of dust aerosols. The experiments encompass the main dust producing months, February through May, for 10 years (1997–2006), and the simulation results are evaluated against ground station and satellite data. The model captures the basic observed climatology over the area of interest. The spatial and temporal variations of near surface concentration, mass load, optical depth and emission of dust aerosols from the main source regions are reproduced by model. The main model deficiency is an overestimate of dust amounts over the source regions and an underestimate downwind of these source areas, which indicates an underestimate of dust dispersal. Over the desert source regions, the net TOA radiative forcing is positive, while it is small over the other regions as a result of high surface albedo values which reduce the short-wave radiative forcing. The net surface radiative fluxes are decreased by dust and this causes a surface cooling locally up to −1°C. The inclusion of net (short-wave and long-wave) dust radiative forcing leads to a reduction of dust emission in the East Asia source regions, which is mainly caused by an increase in local stability and a corresponding decrease in dust lifting. Our results indicate that dust effects should be included in the assessment of climate change over East Asia.
The impact of climate change on surface ozone over Europe was studied using four offline regional chemistry transport models (CTMs) and one online regional integrated climate-chemistry model (CCM), ...driven by the same global projection of future climate under the SRES A1B scenario. Anthropogenic emissions of ozone precursors from RCP4.5 for year 2000 were used for simulations of both present and future periods in order to isolate the impact of climate change and to assess the robustness of the results across the different models. The sensitivity of the simulated surface ozone to changes in climate between the periods 2000–2009 and 2040–2049 differs by a factor of two between the models, but the general pattern of change with an increase in southern Europe is similar across different models. Emissions of isoprene differ substantially between different CTMs ranging from 1.6 to 8.0 Tg yr−1 for the current climate, partly due to differences in horizontal resolution of meteorological input data. Also the simulated change in total isoprene emissions varies substantially across models explaining part of the different climate response on surface ozone. Ensemble mean changes in summer mean ozone and mean of daily maximum ozone are close to 1 ppb(v) in parts of the land area in southern Europe. Corresponding changes of 95-percentiles of hourly ozone are close to 2 ppb(v) in the same region. In northern Europe ensemble mean for mean and daily maximum show negative changes while there are no negative changes for the higher percentiles indicating that climate impacts on O3 could be especially important in connection with extreme summer events.
Post-translational modifications (PTMs) allot versatility to the biological functions of highly conserved proteins. Recently, modifications to non-histone proteins such as methylation, acetylation, ...phosphorylation, glycosylation, ubiquitination, and many more have been linked to the regulation of pivotal pathways related to cellular response and stability. Due to the roles these dynamic modifications assume, their dysregulation has been associated with cancer and many other important diseases such as inflammatory disorders and neurodegenerative diseases. For this reason, we present a review and perspective on important post-translational modifications on non-histone proteins, with emphasis on their roles in diseases and small molecule inhibitors developed to target PTM writers. Certain PTMs' contribution to epigenetics has been extensively expounded; yet more efforts will be needed to systematically dissect their roles on non-histone proteins, especially for their relationships with nononcological diseases. Finally, current research approaches for PTM study will be discussed and compared, including limitations and possible improvements.
Two 12-year simulations were conducted with the RegCM4 model to study how different hydrology schemes can affect the terrestrial hydrology cycle, the surface energy balance, and the regional climate ...of Africa and in particular tropical Africa. One simulation used the default TOP hydrology scheme in the CLM4.5 land surface model; the other used the variable infiltration capacity (VIC) hydrology model coupled to CLM4.5. The results show that the VIC scheme has a lower soil infiltration rate and hence lower surface soil moisture (10 cm in this study) relative to the default TOP scheme. This leads to a different partitioning of terms in the surface energy balance, with low evapotranspiration and high sensible heat flux, resulting in a net warming effect. The VIC simulation also has low relative humidity due to the low evapotranspiration rate. The low infiltration rate of the VIC hydrology also results in accumulation of moisture on the soil surface. In addition, the VIC scheme generates more precipitation, especially in the summer (JJA) season. Thus, the hydrology parameterization can affect not just the terrestrial hydrology cycle but also energy balance partitioning and hence the surface climate. Moreover, the VIC simulation has smaller biases in the surface energy flux and other surface climate variables in comparison with the default CLM4.5 run. We conclude that the VIC land surface hydrology scheme succeeds in controlling the infiltration rate, the surface soil moisture, and hence total evapotranspiration, which improves the surface energy balance and hence produces a better surface climate. Thus, we recommend the VIC hydrology scheme for future climate studies over Africa.
Recycling/valorization of solid-wastes in the cleaner production of building materials not only strongly contributes to the environmental protection from pollutants, but it is regarded as an ideal ...solution in the conservation of naturally-occurring resources that are used in the construction sector. Accordingly, this work aims at eco-sustainable recycling concrete waste (CoW) and hazardous lead-bearing sludge (LBS) in the cleaner production of alkali-activated cementitious materials. The activation of powdered-CoW with different sodium hydroxide (NaOH) contents yields hardened materials, with modest compressive strengths, in which pirssonite is the dominant binding phase as confirmed by X-ray diffractogram, thermal analyses, infrared spectroscopy, and scanning electron microscopy. These materials demonstrate low stability in humidity-rich-environment as a significant regression in their mechanical properties was recorded after 30-days of curing. The use of sodium silicate (Na2SiO3) as alternative to NaOH represents two synergistic positive effects, which are working together, including the enhancement of mechanical properties and stability of the hardened materials at the long term of curing. The positive impact of Na2SiO3 is mainly originated from the formation silicate-rich strength-giving-phases with higher binding capacity and stability compared to pirssonite-phase. LBS was beneficially used as an alternative silicate source to avoid the negative impact of Na2SiO3 on environment. The incorporation of 10 wt % LBS in NaOH–CoW system has resulted in the creation of hardened material with mechanical properties superior to Na2SiO3–CoW one, notably long run stability. The high Pb-immobilization, stability, and acceptable compressive strength are the dominant parameters which directly reflect on the safe and benefit use of NaOH–CoW/LBS10 composite as building brick.
•The alkali-activation was used to valorize concrete waste in building brick making.•Pirssonite causes low stability of NaOH-activated concrete waste in humidity.•The use of Na2SiO3 as main activator led to the retardation of pirssonite formation.•Pb-rich-sludge acts as a good silicate source with lower environmental impact.•All hardened materials having 10 wt % Pb-rich-sludge can be safely used.
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