Mean Surface Pressure Research Articles

Study on cross effect of mesh and turbulence model on separated flow prediction using a tandem cylinder case

Abstract Low dissipative separated flow prediction is still a great challenge in aeronautics engineering. An open-source CFD code named SU2 is employed to study the cross effect of mesh as well as turbulence model on the numerical resolution of separated flow for a tandem cylinder case. Firstly, a nonlinear variation of the numerical resolution for the separated flow is found by comparing the mean surface pressure distribution, mean streamwise velocity profile, the instantaneous vorticity magnitude as well as the aerodynamic forces on the rear cylinder. The resolution of separated flow from the medium mesh is the best compared to those getting from the coarse and fine mesh. Secondly, the reason causing the nonlinear variation of flow resolution is analyzed considering the influence of spatial discretization error and turbulent viscosity locally. A finer mesh would lead to a low spatial discretization error and then a high turbulent viscosity and then causes nonlinear variation of flow resolution. Finally, the existence of a “density boundary” of the mesh is proposed which could balance the spatial precision as well as turbulent viscosity and achieve the prediction of separated flow with a good resolution employing the RANS method.

New multivariate models for the estimation of earth’s albedo and its variation with meteorological parameters over Kano, Nigeria

The study of what happens to sunlight as it goes through the atmosphere is vital to many fields of science because over time, reflection, scattering, and absorption in the atmosphere have changed the amount of solar radiation that reaches the Earth's surface. This study examined the variation in albedo over Kano, situated in the Sahelian climatic zone of Nigeria. The study's data, which covered the years 1984–2022, totaled thirty-nine, was obtained from the National Aeronautics and Space Administration (NASA). Utilizing monthly average daily measured meteorological data on global solar radiation, wind speed, mean temperature, surface pressure, and relative humidity, eleven models of three categories based on two, three, and four variable regression models were developed. Five validation indicators were used to verify the regression models: the t-test, coefficient of determination (R2), mean percentage error (MPE), root mean square error (RMSE), and mean bias error (MBE). The developed models that were considered most appropriate for estimating surface albedo were ranked; the three-variable regression model ALB7, which included the wind speed, relative humidity, and mean temperature, outperformed the previously employed generalized method from literature in estimating surface albedo over Kano. The variation of measured albedo with meteorological parameters depicts a direct relationship for clearness index and wind speed; an inverse relationship was observed for surface pressure. Mean temperature and surface pressure exhibit an inverse relationship during the wet season and vice versa for the dry season.

Experimental and numerical study of wind effect on an ultra‐thin concrete triangular plan shell structure

AbstractSelf‐supporting concrete shell structures are highly efficient in distributing loads, which can result in very reduced thicknesses (ultra‐thin), giving them remarkable slenderness. Due to their geometric complexity, it is difficult to predict how they interact with wind action. The main aim of the present study is to assess the mean surface pressure coefficient distribution in a shell with a triangular plan shape and three supports for different angles of wind incidence. To determine the distribution of surface pressure coefficients and lift and drag force coefficients, an experimental study was carried out in a wind tunnel, and a numerical simulation study was performed through computational fluid dynamics. The experimental and numerical results were analyzed and compared, and making it possible to identify the most critical surface zones and wind incidences when the shell is under the wind action.

Energy Gain Kernel for Climate Feedbacks. Part I: Formulation and Physical Understanding

Abstract This paper introduces a climate feedback kernel, referred to as the “energy gain kernel” (EGK). EGK allows for separating the net longwave radiative energy perturbations given by a Planck feedback matrix explicitly into thermal energy emission perturbations of individual layers and thermal radiative energy flux convergence perturbations at individual layers resulting from the coupled atmosphere–surface temperature changes in response to the unit forcing in individual layers. The former is represented by the diagonal matrix of a Planck feedback matrix and the latter by EGK. Elements of EGK are all positive, representing amplified energy perturbations at a layer where forcing is imposed and energy gained at other layers, both of which are achieved through radiative thermal coupling within an atmosphere–surface column. Applying EGK to input energy perturbations, whether external or internal due to responses of nontemperature feedback processes to external energy perturbations, such as water vapor and albedo feedbacks, yields their total energy perturbations amplified through radiative thermal coupling within an atmosphere–surface column. As the strength of EGK depends exclusively on climate mean states, it offers a solution for effectively and objectively separating control climate state information from climate perturbations for climate feedback studies. Given that an EGK comprises critical climate mean state information on mean temperature, water vapor, clouds, and surface pressure, we envision that the diversity of EGK across different climate models could provide insight into the inquiry of why, under the same anthropogenic greenhouse gas increase scenario, different models yield varying degrees of global mean surface warming. Significance Statement The wide range of 2.5°–4.0°C in global warming projections by climate models hinders our ability to predict its impacts. The newly introduced energy gain kernel (EGK) provides critical information for climate mean infrared opacity, which is collectively determined by climate mean temperature, water vapor, clouds, and surface pressure fields. EGK is directly derived from physical principles without additional definition. EGK captures the temperature feedback’s amplification of energy perturbations initiated from both external forcing and internal nontemperature feedback processes. EGK allows for disentangling positive and negative aspects of temperature feedback, rectifying the common misconception in existing temperature kernels that portray temperature feedback as predominantly negative. The diversity of EGK across different climate models may help explain their varying global warming degrees.

The dominant modes of recent sea level variability from 1993 to 2020 in the China Seas

A better understanding of internal climatic variability is essential for estimating and predicting regional sea level rise in the coming decades. Based on the satellite altimeter data, the cyclostationary empirical orthogonal function (CSEOF) analysis is used to extract and examine the seasonal signal, trend, El Niño-Southern Oscillation (ENSO)-related, and low-frequency mode of sea level anomaly in the China Seas from 1993 to 2020. The interannual changes in the annual cycle of sea level were significantly influenced by the mean surface pressure and the 10-m zonal wind component. Furthermore, strong El Niño events (1997/1998) can significantly affect seasonal fluctuations through precipitation and runoff. By recombining the loading vector and principal component time series of the trend mode, we estimate the sea level trends to be about 3.63 ± 0.37 mm/yr. The South China Sea, followed by the Yellow Sea, is where ENSO's effects on sea level fluctuations are most noticeable. The 2015–2016 El Niño, which was a combination of the Central Pacific (CP) ENSO Eastern Pacific (EP) ENSO, had average sea levels that were much lower than those of the 1997–1998 (CP ENSO) and 2009–2010 (CP ENSO). The Pacific Decadal Oscillation (PDO) can significantly affect the low frequency mode, but other sources also contribute to this mode. The South China Sea, especially to the west of Luzon Island, exhibits the highest level of variability in the low-frequency mode. Finally, our work shows that, in contrast to global or oceanic scales, regional CSEOF analysis does, in fact, capture regional sea level variability more accurately and detailed.

The delivery of water ice to the Martian surface by passive degassing

Passive degassing, or volatile release from persistent, non-eruptive volcanic activity, may have contributed significantly to the Martian ice budget over the planet's history by providing a pathway for volatile species, such as water vapor, to outgas from the interior into the atmosphere and accumulate on the surface. Passive degassing from Martian volcanoes can result in ice accumulations in unusual locations (e.g., outside of the typical cold traps like the Tharsis Rise and polar ice caps). Such locally derived water could cover the volcanic source in an ice-rich veneer that may later serve as a source of ice for subsequent interactions between impactors or lava. Using the Laboratoire de Météorologie Dynamique Generic Planetary Climate Model, we model the spatial distribution of ice that results from passive degassing from five major Martian volcanic centers, Cerberus Fossae, Apollinaris Mons, Elysium Mons, Hadriacus Mons, and Pityusa Patera, and assess the sensitivity of these results to a range of volcanic, atmospheric, orbital, environmental, and numerical parameters. Previous studies have placed estimates on the amount of water released from volcanic outgassing (e.g., Carr, 1987; Craddock and Greeley, 2009; Grott et al., 2011; Carr and Head, 2015), but this is the first study to track the water released from specific volcanoes and to determine the spatial distribution of resulting ice deposits. We find that volcanic variables, such as mass flux and duration of degassing, primarily drive the thickness of volcanogenic ice fields –– higher mass fluxes create the thickest ice deposits (up to ∼210 mm around the volcanic center for a mass flux 106 kg s−1) and durations of >6 months are required for ice to reach near-global distributions. Ice accumulation around the degassing source is maximized if the latitude of passive degassing occurs near the south pole (i.e., Pityusa Patera) due to its exposure to circulation patterns that promote ice deposition in that region. Changes in the season, dust visible optical depth, and eccentricity can also impact the thickness of ice, with ice accumulation around the volcanic source being maximized in the spring, with higher dust visible optical depths, and when the eccentricity is low, due to more favorable temperatures and atmospheric circulation. Variances in the obliquity can also influence ice fields by modulating which latitudes receive more surface ice accumulation. The amount of activated cloud condensation nuclei (CCN) in the atmosphere has a lesser impact on the thickness and spatial distribution of ice fields than other parameters, with lower amounts of CCN leading to narrower, but slightly thicker deposits compared to higher amounts of CCN. The mean surface pressure and longitude of perihelion both affect the timing of ice fields. The surface pressure influences how long water lingers in the atmosphere before depositing to the surface, while the longitude of perihelion controls the time of year in which the thickest ice deposits accumulate around the degassing source. Ice fields are highly sensitive to the model resolution. Higher model resolutions allow for a more detailed representation of physical processes, such as cloud formation and ice deposition, while lower resolution model runs provide a more approximate guide to the representation of these processes and may underestimate surface ice thicknesses around the degassing source. The thickest deposits of ice form around the source of passive degassing, but later migrates and restabilizes in cold traps after degassing has ceased, unless it is protected against sublimation by the deposition of dust or pyroclastic material. Assuming the ice is protected, recurrent episodes of passive degassing could have facilitated the gradual accumulation of ice deposits several meters thick over time.

Global Surface Pressure Pattern for a Compressible Elliptical Cavity Flow Using Pressure-Sensitive Paint

The flow field in a cavity depends on the properties of the upstream boundary layer and the cavity geometry. Comprehensive studies for rectangular cavities have been conducted. This experimental study determines the global surface pressure pattern for elliptical cavities (eccentricities of 0, 0.66 and 0.87) in a naturally developed turbulent boundary layer using pressure-sensitive paint. The ratio between the length (major axis) and the depth is 4.43–21.5, and the freestream Mach number is 0.83. The mean surface pressure distribution of an elliptical cavity resembles that of a rectangular cavity. A change in the value of eccentricity (wall curvature) affects the region for an adverse pressure gradient in an open cavity, an extension of the plateau in a transitional–closed cavity and flow expansion near the front and rear edges. The boundaries between an open, transitional and closed cavities vary.

Evaluating the potential footprints of land use and land cover and climate dynamics on atmospheric pollution in Pakistan

Evaluating the potential impacts of land use and land cover change (LULCC) and climate change on air pollution is crucial to unravel the driving forces and mechanisms behind changes in air quality. A multi-faceted approach was adopted, including a land change model (LCM) and Mann–Kendall (MK) test, to evaluate the transition of land cover type, changes in climate, and atmospheric pollutants during 2004–2021 in Pakistan. Moreover, a multiscale geographically weighted regression (MGWR) model and a mathematical model were used to assess the potential contribution of LULCC and climate dynamics to atmospheric pollution. It was revealed that during 2004, croplands covered an area of 9.72 × 104 mile2, accounting for 38% of the total area. However, the area of the croplands increased to 10.1 × 104 mile2, accounting for 40% of the total area in 2021. The MK test showed that the north and west–south regions significantly experienced air pollution, with the increasing trend for nitrogen dioxide (NO2) and sulfur dioxide (SO2) being 0.89× 1015 molecules/cm2 per year and 0.54 DU/year, respectively. For climate variability, mean precipitation (Precp) and mean surface pressure (SP) showed a prominent increasing trend, with a maximum value of 1 mm/year and 0.01 Kpa/year, respectively. The mean temperature maximum (Tmax) showed an increasing and decreasing trend, with the highest value of 0.28°C/year and 0.08°C/year, respectively. In the context of contribution, the conversion of cropland to grasslands increased the trend for SO2 concentrations. The highest increasing trend of 1.5 DU for ozone (O3) was found due to conversion of grasslands to shrublands. Additionally, regional climate played a significant role in making air pollution stagnant across the country. Precp and wind speed (WS) contributed significantly in escalating NO2 concentrations in Pakistan, while Precp contributed most (0.004 DU) to increasing SO2 concentrations. For O3, the most influential climate factor was Precp. These results on a long-term temporal scale demonstrated how maintaining climate variability through comprehensive land use management can help improve ambient air quality in Pakistan.

Turbulent flow in an I–L junction: Impacts of the pipe diameter ratio

Pipeline junction plays a pivotal role in fluid mixing for biomedical, chemical, and industrial processes. This study introduces an I–L junction for pipeline systems, fostering concurrent flow between branch-pipe injection and the main pipe bulk flow. In contrast to the conventional T-junction with perpendicular injection, the I–L design demonstrates high potential in mitigating vibration-induced fatigue risks, given an optimal branch-to-main pipe diameter ratio, rd. Using unsteady Reynolds-averaged Navier–Stokes equations, the study assesses fluid mixing across a broad range of rd (1/12–1/2.5). The streamline geometry undergoes a transition from well-defined symmetric vortices to unsteady oscillations when the pipe diameters diverge beyond 1/4, arising from vortex shedding in the wake of the branch pipe. Despite the conventional T-junction showing a more homogeneous velocity distribution in the streamwise direction, its turbulent kinetic energy (TKE, both modeled and calculated from the resolved-scale velocities) near the junction is an order of magnitude larger, implying high overall inhomogeneity in the flow. The TKE decays rapidly to an equivalent level compared to the proposed I–L junction approaching discharge, indicating that the peaking of TKE in the T-junction does not significantly contribute to enhanced fluid mixing. Conversely, it can likely result in harmful vibrations inside the pipeline. While the turbulence statistics remain qualitatively unchanged for rd<1/4, an enlarged discrepancy in pipe diameters beyond rd<1/6 yields more favorable mean surface pressure coefficient, CP¯. The results provide insights into pipeline design, recommending an optimal pipe diameter ratio for enhanced mixing of successively collected fluids while retaining improved system reliability.

Anticipating Surface Mean Pressure Coefficient on Inner Surface of C-Shaped Irregular Buildings Using Artificial Intelligence Methodology

Anticipating Surface Mean Pressure Coefficient on Inner Surface of C-Shaped Irregular Buildings Using Artificial Intelligence Methodology

Estimation and Correlation of Surface Water Vapour Density in Benin, Nigeria

The present study investigated the monthly average daily mean temperature, relative humidity, surface pressure, cloud cover, and sunshine hours associated with monthly variations in surface water vapour density (SWVD) for the period extending from 1979 to 2016 for Benin (Latitude 6.320N, Longitude 5.100E). The daily variation of SWVD for the dry season (November to March) and rainy season (April to October) for the year 2014 was examined. Statistical indices of coefficient of determination (R2), mean bias error (MBE), root mean square error (RMSE), mean percentage error (MPE), Nash-Sutcliffe equation (NSE), and index of agreement (IA) were used to compare and evaluate the generated two variable SWVD-based models. The findings revealed that the level of SWVD varied throughout the investigation period on each day of the month. The SWVD is higher during the wet season than it is during the dry season, based to the monthly average daily values. The average SWVD was found to be at its highest point in the month of August during the rainy season and its lowest point in the month of December during the dry season (21.1448 gm-3). The greatest amount of SWVD was observed on 23rd May, 2014 with 27.5731gm-3 and the lowest on 26th December, 2014 with 9.6567 gm-3. Pressure and precipitable water vapour are related to each other using a multivariate correlation regression model that was constructed with R2 = 100%, MBE = -0.0204 gm-3, RMSE = 0.0206 gm-3, MPE = 0.1105 %, NSE = 99.9897% and IA = 99.9974% was better appropriate for SWVD estimation with the best fitting and therefore can be used for estimating SWVD in Benin.

Estimation of Surface Water Vapour Density and its Variation with other Meteorological Parameters over Akure, Nigeria

In this paper, the monthly variation of Surface Water Vapour Density (SWVD) with meteorological parameters of monthly average daily mean temperature, relative humidity, surface pressure, cloud cover and sunshine hours during the period of thirty-eight (38) years (1979 - 2016) for Akure (Latitude 7.280N, Longitude 5.300E, 375m above sea level) were investigated. The daily variation of surface water vapour density for the two distinct seasons considering two typical months in each during the period of year 2014 was examined. The results showed fluctuation in the amount of surface water vapour density in each day of the month for the period under investigation. The monthly average daily values indicated that the surface water vapour densities are greater during the rainy season than in the dry season. It was observed that the maximum average value of surface water vapour density of 20.1019 gm-3 occurred in the month of September during the rainy season and minimum value of 15.5110 gm-3 in the month of January during the dry season. The highest value of surface water vapour density was observed on the 4th of June, 2014 with 26.3320 gm-3 and the lowest on the 31st day of December, 2014 with 6.0276 gm-3. The comparison assessment of the developed two variable SWVD based models was carried out using statistical indices of coefficient of determination (R2), Mean Bias Error (MBE), Root Mean Square Error (RMSE), Mean Percentage Error (MPE), Nash – Sutcliffe Equation (NSE) and Index of Agreement (IA). The developed multivariate correlation regression model that relates pressure and precipitable water vapour with R2 = 100%, MBE = -0.0177, RMSE = 0.0179, MPE = 0.1034, NSE = 99.9956% and IA = 99.9989% was found more suitable for surface water vapour density estimation with good fitting and therefore can be used for estimating surface water vapour density in Akure.

Impact of a new clinical mattress solution on interface pressure and comfort during supine lying.

Effective pressure management for individuals is critical for hospital and community-based care, to prevent the occurrence of pressure ulcers. This study explores the impact of a new mattress and topper solution on interface pressure and comfort during supine lying. In this quantitative, healthy cohort study, patient-surface interface pressures were calculated for three mattresses (a standard hospital mattress, a new mattress solution (Levitex Foams Ltd., UK) and a dynamic air flow mattress) with and without an innovative topper solution (Levitex Foams Ltd., UK). Subjective comfort, contact surface area, peak and mean pressure and peak pressure index (head, sacrum, heels) were calculated for all mattress conditions for a 21-minute period. A total of 27 healthy volunteers took part in this study. The new mattress solution decreased peak pressure significantly compared with the hospital and air mattresses (p<0.04). Lower peak pressures were observed for the hospital mattress compared with the dynamic air flow mattress. The new mattress solution improved comfort and significantly lowered (>30%; p≤0.005) heel and head pressure compared with the other surfaces. Both hospital and air mattresses significantly reduced pressure and improved comfort with the addition of the new topper solution (p<0.05). The new mattress solution used in this study offers a potentially improved pressure management solution for individuals. Implementation of the topper may also help to improve pressure management when used with existing standard or dynamic air flow mattresses.

A Critical Comparison of DNS Versus RANS Model Results on an HPT Blade for a Small Engine

In this work, we present preliminary Direct Numerical Simulation (DNS) results of compressible flow past a High-Pressure Turbine (HPT) blade of an experimental Small Turbofan Engine (STFE) designed by Defence Research and Development Organisation (DRDO), Gas Turbine Research Establishment (GTRE) [1, 2]. These DNS results are then compared with the results obtained by two well-known industry standard RANS models, namely the Realizable k-e (RKE) and the Shear Stress Transport (SST) models along with a hybrid LES-RANS (LNS) model. All the simulations are carried out at inlet Reynolds number of 152,000 (based on chord length of the blade), and inlet Mach number of 0.16 with zero degree of angle of incidence. DNS results are obtained with approximately 94 and 129 million mesh cells. For RANS and LNS calculations, we have used 0.16 and 3.54 million mesh cells respectively. Surface pressure distributions obtained from DNS are closer to experimental values compared to RANS and LNS. Also, DNS predicts flow separation near the trailing edge when a grid is refined from 94 x 106 to 129 x 106 cells, whereas present RANS and LNS simulations fail to capture separation. Interestingly, mean surface pressure obtained from DNS with two different mesh sizes vary mostly near the separation and trailing edge region, where the experimental data points are not available.

Relationship between iliopsoas muscle surface pressure and implant alignment after total hip arthroplasty: a cadaveric study

Iliopsoas impingement after total hip arthroplasty is caused by the implant irritating the iliopsoas muscle, but changes in the iliopsoas muscle have not been quantitatively evaluated. This study assessed changes in the surface pressure of the iliopsoas muscle when the implant alignment was varied. Total hip arthroplasty was performed in 10 fresh-frozen cadaveric hips. We evaluated the maximum and mean surface pressure of the iliopsoas muscle with the hip in 20° and 10° extension, the neutral position, and 10° flexion when the anterior cup protrusion length (ACPL), stem version, and stem offset were varied. When the ACPL was changed to 0, 3, and 6 mm in 20° extension, the maximum surface pressure was significantly increased for ACPL of 6 mm compared with 0 mm. Decreased stem anteversion resulted in a significant reduction in both the maximum and mean surface pressure compared with native anteversion from 20° extension to the neutral position. Increased stem offset resulted in significant increases in the maximum and mean surface pressure of the iliopsoas muscle compared with decreased stem offset in 20° extension. Not only large ACPL but also changes in stem version and offset affected the maximum surface pressure of the iliopsoas muscle.

Effect of Plate Distance on Steady and Unsteady Characteristics of Impinging Rectangular Jet

Acoustic and unsteady characteristics of a rectangular jet impinging on a flat plate were investigated. Experiments were performed at the nozzle pressure ratio of 2 for the impingement distances , 4, 8, and 12. The mean and unsteady flow properties of the impinging jet were studied using the steady and unsteady pressures on the impinging surface, time-resolved schlieren images, and acoustic measurements at different directivity angles. Mean schlieren images elucidate the flow features including redirected flow, and the plate shock for the impingement distance . The mean surface pressures show unidentical pressure profiles in the and planes. The pressure profile in the plane is found to be identical to the free-jet case. Proper orthogonal decomposition performed on the time-resolved schlieren images shows that the impinging jet is dominated by the flapping instability mode for a given range of impingement distances. Flow features such as plate shock and the redirected flow were assessed using proper orthogonal decomposition and time-resolved schlieren images. Synchronized acoustic and unsteady pressure measurements reveal the coupling between the upstream acoustic waves and the unsteadiness arising from the impinging surface.

Experimental Characterization of an Axisymmetric Transonic Separated Flow for Computational Fluid Dynamics Validation

An experimental characterization of transonic, turbulent, separated flow generated by an axisymmetric model is presented, with intent for use as a computational validation case. The model is a scaled version of a geometry inspired by Bachalo and Johnson (“Transonic, Turbulent Boundary-Layer Separation Generated on an Axisymmetric Flow Model,” AIAA Journal, Vol. 24, No. 3, 1986, pp. 437–442), consisting of a circular bump on a constant-diameter cylinder aligned with the flow. The Mach 0.875 flow is turbulent approaching the bump and becomes locally supersonic at the apex. This leads to a shock-wave/boundary-layer interaction, a separation bubble, and unsteady flow reattachment downstream. Tunnel boundary conditions are characterized, and mean surface pressure, mean skin friction, and both mean and fluctuating velocity fields are measured throughout the interaction region. Uncertainty estimates are provided for all measurements. The degree of flow axisymmetry and evidence of relaminarization are discussed, and a comparison is made to historical data.

Separation Control for a Transonic Convex Corner Flow Using Ramp-Type Vortex Generators

A flap can be used to control wing camber and as a high-lift device. A convex corner is a simplified model of the upper surface of a flap. At transonic speeds, shock-induced boundary layer separation (SIBLS) occurs at greater freestream Mach numbers and deflection angles. This results in energy losses and a reduction in aerodynamic performance. This study installs ramp-type vortex generators (VGs) upstream of a convex corner, and the effect of the height of the VG on SIBLS is determined. As the height of the VG increases, the magnitude of the mean surface pressure upstream of the corner increases and downstream expansion decreases, which results in a reduction in lift. A reduction in peak surface pressure fluctuations, the separation length, and the frequency of shock oscillation is also determined. For flow control and lift enhancement, micro-VGs are more effective.

Estimation and variation of saturation mixing ratio and mixing ratio over Potiskum, Nigeria

In this study, the monthly average mean temperature, relative humidity and surface pressure data obtained from the European Centre for Medium-Range Weather Forecasts (ECMWF) for a period of thirty-eight (1979 – 2016) years was employed to estimate the saturation mixing ratio and mixing ratio for Potiskum located in the Sahelian climatic zone of Nigeria. The monthly variation of saturation mixing ratio and mixing ratio with the meteorological parameters during the period under focused was investigated. The results revealed that the maximum and minimum values of saturation mixing ratio were found in the months of May and December with 31.7067 g kg-1 and 17.5980 g kg-1, respectively. The maximum and minimum values of saturation mixing ratio were found in the months of September and February with 20.6797 g kg-1 and 4.1153 g kg-1, respectively. The results showed that high values of mixing ratio were observed during the rainy season and low values during the dry season. The monthly variation of saturation mixing ratio with mean temperature and the monthly variation of mixing ratio with relative humidity depicts direct relationship. The monthly variation of saturation mixing ratio with atmospheric pressure and relative humidity and the monthly variation of mixing ratio with mean temperature and atmospheric pressure varies differently.

Comparison between CMIP5 and CMIP6 Models over MENA Region Using Historical Simulations and Future Projections

The study evaluated the ability of 11 global climate models of the latest two versions of the Coupled Model Intercomparison Project (CMIP5 and CMIP6) to simulate observed (1965–2005) rainfall, maximum (Tmax) and minimum (Tmin) temperatures, mean eastward (uas) and northward (vas) wind speed, and mean surface pressure. It also evaluated relative uncertainty in projections of climate variables using those two CMIPs. The European reanalysis (ERA5) data were used as the reference to evaluate the performance of the GCMs and their mean and median multimodel ensembles (MME). The study revealed less bias in CMIP6 GCMs than CMIP5 GCMs in simulating most climate variables. The biases in rainfall, Tmax, Tmin, uas, vas, and surface pressure were −55 mm, 0.28 °C, −0.11 °C, −0.25 m/s, −0.06 m/s, and −0.038 Kpa for CMIP6 compared to −65 mm, 0.07 °C, −0.87 °C, −0.41 m/s, −0.05 m/s, and 0.063 Kpa for CMIP5. The uncertainty in CMIP6 projections of rainfall, Tmax, Tmin, uas, vas, and wind speed was relative more narrow than those for CMIP5. The projections showed a higher increase in Tmin than Tmax by 0.64 °C, especially in the central region. Besides, rainfall in most parts of MENA would increase; however, it might decrease by 50 mm in the coastal regions. The study revealed the better ability of CMIP6 GCMs for a wide range of climatic studies.