Column Model Simulations Research Articles

North American Monsoon Impacts Southern California's Coastal Low Clouds

AbstractLow‐level stratiform clouds modulate California's coastal climate during the warm season. Previous work describing the seasonal and daily variability of coastal low cloudiness (CLC) suggests that in July, August, and September southern California's CLC is under the influence of an additional driver, which has less impact in northern California. In this work, we introduce the link in which free‐tropospheric moisture dictated by North American Monsoon (NAM) processes can impact southern California CLC. We use in situ and remote sensing observations, as well as reanalysis and single column model simulations to identify and investigate this previously missing component. We find that monsoonal moisture advected by southeasterly flow from the core NAM region into southern California reduces CLC by diminishing cloud‐top longwave cooling. To add to an already complex brew of known factors influencing coastal cloudiness, another one is hereby introduced and should be accounted for in future work.

Surface Energy Fluxes and Temperatures at Jezero Crater, Mars

AbstractDiurnal ground surface and air temperatures (Tg, Ta) and the five major surface energy budget fluxes are displayed as derived from M2020 mission observations and from column model simulations in two extreme cases (low and high diurnal Tg‐variation) along the Perseverance rover track in the Jezero crater. In both cases the fluxes and Tg are well modeled when using diurnally variable apparent ground thermal inertia I derived via a Fourier series method from the hourly observations. Hence the measurements, the diagnostic method and the model results are consistent with high‐ and low‐I nonhomogeneous terrain in the field‐of‐view (FOV) of the thermal infrared and solar sensors. In contrast less extreme values of I consistent with THEMIS retrievals are necessary for good simulations of observed Ta. We deduce that the measured Tg for the small ∼3 m2 FOV may not always be representative for the larger region around the rover, which controls the near‐surface atmospheric temperature profile.

Surface energy budget at Curiosity through observations and column modeling

Diurnal ground surface temperatures (Tg) and the five major terms of the surface energy budget (SEB) are displayed from hourly Mars Science Laboratory observations and from column model simulations in four contrasting cases along the Curiosity traverse. Tg and the SEB terms are otherwise well simulated on regolith near the landing spot and on rocky Pahrump Hills, but the residual in observation-based SEB (~downwelling longwave radiation) shows unexplained peaks in the morning and evening and simultaneously model-Tg is too cold. Enhanced or diurnally variable crater dust does not help but diurnally variable soil thermal inertia (suggested by Fourier analysis of observed Tg) reduces both defects at both sites. Sand on the steep Namib dune is instead homogeneous, defects here being reduced by taking into account slope effects. Regolith at the 2018 dust storm site appears inhomogeneous, with the SEB terms and Tg relatively well simulated even in this case of extremely heavy dust load.

Co-transport of biogenic nano-hydroxyapatite and Pb(II) in saturated sand columns: Controlling factors and stochastic modeling

Biogenic nano-hydroxyapatite (bio-nHAP) has recently gained great interest in many domains, especially in the remediation of heavy metal-contaminated soil, due to its high reactivity, low cost, and eco-friendly nature. The co-transport and reaction of bio-nHAP with Pb(II) in saturated porous media, however, are not well understood. This work investigated the effects of ionic strength (IS), ionic composition (IC), dissolved organic matter (DOM), and flow velocity on transport-reaction dynamics of Pb(II) and bio-nHAP by combining column breakthrough experiments and model simulations. Results showed that the mobility of Pb(II) was significantly enhanced with increasing IS/IC but less affected by flow velocity during the transport-reaction process of bio-nHAP and Pb(II) in the saturated sand column; while the transport of bio-nHAP was restricted by increasing IS/IC but facilitated by increasing velocity. IC, IS, and velocity only slightly affected the reaction kinetics between Pb(II) and bio-nHAP, likely due to the fast reaction rate between Pb(II) and bio-nHAP and precipitation of pyromorphite. The transport dynamics of bio-nHAP and Pb(II) were significantly changed by DOM, and this effect depended strongly on the type of DOM with different molecular weights. Breakthrough curves of Pb(II) and bio-nHAP exhibited apparent “anomalous”, sub-diffusive transport behaviors, which could be well quantified by a novel tempered fractional derivative bimolecular reaction equation (T-FBRE). Our findings highlighted the accurate simulation of the co-transport and reaction of bio-nHAP with Pb(II) using T-FBRE and had a great benefit for risk assessment and remediation strategy development for Pb(II) contaminated soil.

Water vapor adsorption on Mars

Near-surface air moisture observations from Phoenix and Curiosity display diurnal adsorption, which appears insensitive to mineralogy of regolith. To study this, adsorptive column model simulations are made for midsummer at Phoenix, validated against recalibrated TECP water vapor pressures p. Two standard-form (= obeying the van't Hoff equilibrium law) adsorption isotherms with quite different specific surface areas As do produce nearly identical and good matches with the observed p, whereas a widely used non-standard isotherm fails. When made standard, it also produces good results. Adsorbed amounts differ in the three good simulations but their surface fluxes and surface vapor concentrations are nevertheless nearly identical. Properties of regolith except enthalpy are shown to disappear in the model's adsorption term, explaining insensitivity to As. The van't Hoff plot of observed ln p vs. model's 1/Tg during adsorption and desorption suggests enthalpy of about 22 kJ/mol. Enthalpies of the three standard-form isotherms are close to this, explaining their excellent match with each other and with observations. Hence the low-pressure water vapor adsorption to martian regolith appears essentially nonspecific and is associated with low enthalpy, as is typical for physisorption in general.

Collisional growth in a particle-based cloud microphysical model: insights from column model simulations using LCM1D (v1.0)

Abstract. Lagrangian cloud models (LCMs) are considered the future of cloud microphysical modelling. Compared to bulk models, however, LCMs are computationally expensive due to the typically high number of simulation particles (SIPs) necessary to represent microphysical processes such as collisional growth of hydrometeors successfully. In this study, the representation of collisional growth is explored in one-dimensional column simulations, allowing for the explicit consideration of sedimentation, complementing the authors' previous study on zero-dimensional collection in a single grid box. Two variants of the Lagrangian probabilistic all-or-nothing (AON) collection algorithm are tested that mainly differ in the assumed spatial distribution of the droplet ensemble: the first variant assumes the droplet ensemble to be well-mixed in a predefined three-dimensional grid box (WM3D), while the second variant considers the (sub-grid) vertical position of the SIPs, reducing the well-mixed assumption to a two-dimensional, horizontal plane (WM2D). Since the number of calculations in AON depends quadratically on the number of SIPs, an established approach is tested that reduces the number of calculations to a linear dependence (so-called linear sampling). All variants are compared to established Eulerian bin model solutions. Generally, all methods approach the same solutions and agree well if the methods are applied with sufficiently high resolution (foremost is the number of SIPs, and to a lesser extent time step and vertical grid spacing). Converging results were found for fairly large time steps, larger than those typically used in the numerical solution of diffusional growth. The dependence on the vertical grid spacing can be reduced if AON-WM2D is applied. The study also shows that AON-WM3D simulations with linear sampling, a common speed-up measure, converge only slightly slower compared to simulations with a quadratic SIP sampling. Hence, AON with linear sampling is the preferred choice when computation time is a limiting factor. Most importantly, the study highlights that results generally require a smaller number of SIPs per grid box for convergence than previous one-dimensional box simulations indicated. The reason is the ability of sedimenting SIPs to interact with a larger ensemble of particles when they are not restricted to a single grid box. Since sedimentation is considered in most commonly applied three-dimensional models, the results indicate smaller computational requirements for successful simulations, encouraging a wider use of LCMs in the future.

Single Column Model Simulations of Icing Conditions in Northern Sweden: Sensitivity to Surface Model Land Use Representation

In-cloud ice mass accretion on wind turbines is a common challenge that is faced by energy companies operating in cold climates. On-shore wind farms in Scandinavia are often located in regions near patches of forest, the heterogeneity length scales of which are often less than the resolution of many numerical weather prediction (NWP) models. The representation of these forests—including the cloud water response to surface roughness and albedo effects that are related to them—must therefore be parameterized in NWP models used as meteorological input in ice prediction systems, resulting in an uncertainty that is poorly understood and, to the present date, not quantified. The sensitivity of ice accretion forecasts to the subgrid representation of forests is examined in this study. A single column version of the HARMONIE-AROME three-dimensional (3D) NWP model is used to determine the sensitivity of the forecast of ice accretion on wind turbines to the subgrid forest fraction. Single column simulations of a variety of icing cases at a location in northern Sweden were examined in order to investigate the impact of vegetation cover on ice accretion in varying levels of solar insolation and wind magnitudes. In mid-winter cases, the wind speed response to surface roughness was the primary driver of the vegetation effect on ice accretion. In autumn cases, the cloud water response to surface albedo effects plays a secondary role in the impact of in-cloud ice accretion, with the wind response to surface roughness remaining the primary driver for the surface vegetation impact on icing. Two different surface boundary layer (SBL) forest canopy subgrid parameterizations were tested in this study that feature different methods for calculating near-surface profiles of wind, temperature, and moisture, with the ice mass accretion again following the wind response to surface vegetation between both of these schemes.

A multiphase CMAQ version 5.0 adjoint.

We present the development of a multiphase adjoint for the Community Multiscale Air Quality (CMAQ) model, a widely used chemical transport model. The adjoint model provides location- and time-specific gradients that can be used in various applications such as backward sensitivity analysis, source attribution, optimal pollution control, data assimilation, and inverse modeling. The science processes of the CMAQ model include gas-phase chemistry, aerosol dynamics and thermodynamics, cloud chemistry and dynamics, diffusion, and advection. Discrete adjoints are implemented for all the science processes, with an additional continuous adjoint for advection. The development of discrete adjoints is assisted with algorithmic differentiation (AD) tools. Particularly, the Kinetic PreProcessor (KPP) is implemented for gas-phase and aqueous chemistry, and two different automatic differentiation tools are used for other processes such as clouds, aerosols, diffusion, and advection. The continuous adjoint of advection is developed manually. For adjoint validation, the brute-force or finite-difference method (FDM) is implemented process by process with box- or column-model simulations. Due to the inherent limitations of the FDM caused by numerical round-off errors, the complex variable method (CVM) is adopted where necessary. The adjoint model often shows better agreement with the CVM than with the FDM. The adjoints of all science processes compare favorably with the FDM and CVM. In an example application of the full multiphase adjoint model, we provide the first estimates of how emissions of particulate matter (PM2.5) affect public health across the US.

Humidity observations and column simulations for a warm period at the Mars Phoenix lander site: Constraining the adsorptive properties of regolith

Two recalibrated sets of Phoenix (PHX) near-surface TECP air humidity measurements were compared with results from adsorptive single column model simulations during a warm clear-sky polar midsummer period, PHX sols 50–60. The model's 2 m temperatures were close to the observed values. Relative humidity (RH) is very low during the day but at night RH at 2 m reaches nearly 100% by the Zent et al. (2016) recalibration (Z), and 60–70% by the Fischer et al. (2019) recalibration (F). Model values of RH2m are close to Z and F at night and to F during the day. All three imply low water vapor pressures near the surface at night, 0.03–0.05 Pa, with a rapid increase each morning to 0.3–1 Pa and a decrease in the evening by both F and the model simulation. The model's daily adsorbed and desorbed water is in balance for regolith porosity of 16% (instead of 35% for lower latitudes). The depleted layer of nighttime air moisture extends to only about 200 m above the surface; hence the model's precipitable water content stays around the observed ~30 μm throughout the sol. The model's moisture cycle is not sensitive to tortuosity of the regolith but the in-pore molecular diffusivity should be at least 5 cm2/s for fair agreement with the observations. In the adsorption experiments there is no fog and just a hint of ground frost, as observed during this period. Strong night frosts appear if adsorption is made weak or absent in the model.

Curiosity observations and column model integrations for a martian global dust event

The Curiosity observations of surface pressure, optical thickness (τ), and Mars Year 32 water column values (PWC) were used to force adsorptive column model simulations around the MY34 strong dust event. Hourly ground (Tg) and air temperatures and water vapor mixing ratios were used for model validation. The diurnal amplitude of Tg drops from 90 K to 30 K during thick dust (τ up to 7–8.5), then increases back to 90 K in the pace of τ decreasing back to seasonal average values. The model mimics the very large and rapid temperature changes quite well, strong dust downward IR emission being the dominant term in the surface heat budget during thick dust. Sensitivity tests indicate that the thick dust tends to show more solar forward scatter initially, consistent with larger particles. Water vapor mixing ratios are lower than normal before and after the event but a lot higher during it. The required local PWC at Gale is 2–3 μm lower than during the low-dust MY32 before and after the dust event, but about 7–8 μm higher during the peak of it.

Formation of Arctic Stratocumuli Through Atmospheric Radiative Cooling

AbstractStratocumulus clouds are important to the Arctic climate because they are prevalent and exert a strong radiative forcing on the surface. However, relatively little is known about how stratocumulus clouds form in the Arctic. In this study, radiative transfer calculations are used to show that the timescale over which stably stratified Arctic temperature and water vapor profiles cool to saturation is less than typical residence times for individual air parcels in the Arctic. This result is consistent with previous studies in suggesting that elevated stratocumulus can form naturally through clear‐sky radiative cooling during all seasons, without assistance from frontal lifting or other atmospheric forcing. Single column model simulations of the cloud formation process, after radiative cooling has resulted in saturation in a stably stratified profile, suggest that stratocumulus cloud properties are sensitive to the characteristics of the environment in which the formation process takes place. For example, sensitivity tests suggest that clouds may attain liquid water paths of over 50 g/m2 if they form in moist environments but may become locked in a low‐liquid water path quasi steady state or dissipate within hours if they form in dry environments. A potential consequence of these sensitivities is that when an Arctic stratocumulus layer forms by radiative cooling, it is more likely to become optically thick, optically thin, or dissipate than it is to obtain an intermediate optical thickness. This could help explain why the cloudy and radiatively clear atmospheric states are so prevalent across the Arctic.

Water vapor mixing ratios and air temperatures for three martian years from Curiosity

The Mars Science Laboratory (MSL) Rover Environmental Monitoring Station humidity instrument (REMS-H) onboard the Curiosity rover is measuring daily minimum water vapor mixing ratios (min vmr), the respective pre-dawn air temperatures (T), and vmr at 2200LT. These are displayed for nearly three martian years (sols 10–2003) and compared with adsorptive column model simulations. The model was initialized with MSL-observed local column water contents, optical depths and surface pressures from sols 230–1291, assuming the same annual cycle outside this period.The first two and a half MSL years present rather similar annual cycles in the REMS-H data, whereas from about sol 1800 onward the min vmr and T suddenly increase and the 2200LT vmr values get closer to the min vmr, indicating less depletion of water vapor during the nights. Model experiments with typical regolith (ground thermal inertia of 300 SI units and porosity of 30% for adsorption) match the observed min vmr and T relatively well for the first 2.5 years. However, from about sol 1800 onward, when Curiosity started to climb onto Mt. Sharp, simulations with higher thermal inertia of about 400 SI units and very low porosity of ~0.3%, suggesting exposed bedrock, provide a far better fit. Some other periods of bedrock- and dune-dominated ground can be detected from the REMS-H vmr and air-T data along the Curiosity traverse.

Transport of multi-walled carbon nanotubes stabilized by carboxymethyl cellulose and starch in saturated porous media: Influences of electrolyte, clay and humic acid

This study investigated the transport behaviors of carboxymethyl cellulose (CMC) and starch stabilized multi-walled carbon nanotubes (MWNTs) through a saturated quartz sand column in the presence of electrolytes, model clays, and natural organic matter (humic acid) through column breakthrough experiments and model simulations. Both stabilizers, CMC and starch, greatly enhanced the breakthrough of MWNTs, with a full breakthrough plateau (C/C0) ranging from 0.69 to 0.90 at ionic strength from 0.3 to 10mM. Between the two stabilizers, CMC was more effective in resisting particle deposition, and thus CMC-stabilized MWNTs were more transportable through the medium. While non-stabilized MWNTs were much less transportable and were vulnerable to electrolyte effects (especially Ca2+), the stabilized counterparts were much more resistant to the coagulation effects of electrolytes. The presence of colloidal clay particles showed contrasting effects on the transport of bare and stabilized MWNTs. The full breakthrough C/C0 of bare MWNTs was suppressed by kaolinite and montmorillonite particles from 0.33 to <0.15 with 5mg/L clay, indicating that the presence of both clays enhanced the aggregation and deposition of MWNTs. However, kaolinite particles facilitated the transport of stabilized-MWNTs, while montmorillonite weakened the breakthrough of stabilized MWNTs. Humic acid had less effect on the mobility of stabilized-MWNTs than that of bare MWNTs. The advection-dispersion transport model incorporated with the filtration theory was able to simulate the breakthrough curves and quantitatively interpret the particle deposition. The results can facilitate our understanding of fate and transport of stabilized carbon nanotubes in the environment.

Durability of organobentonite-amended liner for decelerating chloroform transport

Chloroform is added to landfill for suppressing methane generation, which however may transport through landfill liners and lead to contamination of groundwater. To decelerate chloroform transport, the enhanced sorption ability of clay liners following organobentonite addition was tested. In this study, we used batch sorption to evaluate sorption capacity of chloroform to organobentonite, followed by column tests and model simulations for assessing durability of different liners. Results show that adding 10% CTMAB-bentonite (organobentonite synthesized using cetyltrimethylammonium bromide) increased the duration of a bentonite liner by 88.5%. CTMAB-bentonite consistently showed the highest sorption capacity (Qm) among six typical organobentonites under various environmental conditions. The removal rate of chloroform by CTMAB-bentonite was 3.6–23 times higher than that by natural soils. According to the results derived by model simulation, a 70-cm 10% CTMAB-bentonite liner exhibited much better durability than a 100-cm compact clay liner (CCL) and natural bentonite liner evidenced by the delayed and lower peak of eluent concentration. A minimum thickness of 65.8 cm of the 10% CTMAB-bentonite liner could completely sorb the chloroform in a 100-m-high landfill. The 10% CTMAB-bentonite liner exhibiting much better durability has the promise for reducing environmental risk of chloroform in landfill.

The diurnal water cycle at Curiosity: Role of exchange with the regolith

Hourly temperatures T, relative humidities RH and mass mixing ratios of moisture q at 1.6m derived from the Mars Science Laboratory REMS-H and REMS-P measurements are shown for MSL sols 15–17 (Curiosity at Bradbury) and 80–82 (Curiosity at Rocknest). They are compared to column model simulations with and without adsorption to porous regolith. The observed mixing ratio is small at night (10–30ppmm). It increases rapidly to 50–80ppmm after sunrise and decreases slowly during the evening. The model gives a good account of the observed T and, with adsorption and realistic precipitable water content (PWC), reproduces the diurnal cycles of both RH and q relatively well. The suggested regolith thermal inertia is 300tiu and porosity 35–40% for both sites. According to the simulations moisture is adsorbed and diffused to the cooling regolith in the evening from the lowest very stable air layer. It is then desorbed in the morning from the rapidly warming regolith and mixed throughout the growing convective boundary layer. Estimates of PWC based on night-time near-surface moistures (assuming an even distribution with height) might therefore be on the low side in areas of porous adsorbing regolith.

Mars Science Laboratory diurnal moisture observations and column simulations

Hourly observations of air temperature and relative humidity at 1.6 m height from the surface (T 1.6 m, RH 1.6 m) measured by the Mars Science Laboratory (MSL) Rover Environmental Monitoring Station relative humidity (REMS-H) device are shown for MSL solar days 15–17 and 80–82, augmented with column model simulations. The diurnal range of T 1.6 m was 197–268 K in the first period, RH 1.6 m being small (<1%) in daytime but increasing to 45–49% by sunrise. During the warmer second period the T 1.6 m range was 201–275 K with RH 1.6 m only up to 16% in the morning. The modeled temperatures were quite close to those observed when the local albedo was set to 0.15 and thermal inertia to 300 tiu. The modeled RH 1.6 m was close to that observed when the well-mixed boundary layer values (0–4 km) of the mass mixing ratio q were 28–30 ppmm (suggesting a precipitable water content (PWC) of ~5.5 µm) during the first period and 12 ppmm (PWC of ~2 µm) during the second period. The REMS-H observations indicate systematic diurnal variation in the near-surface mixing ratio.

Sensitivity of cirrus and mixed-phase clouds to the ice nuclei spectra in McRAS-AC: single column model simulations

Abstract. The salient features of mixed-phase and ice clouds in a GCM cloud scheme are examined using the ice nucleation parameterizations of Liu and Penner (LP) and Barahona and Nenes (BN). The performance of both parameterizations was assessed in the GEOS-5 AGCM using the McRAS-AC cloud microphysics framework in single column mode. Four dimensional assimilated data from the intensive observation period of ARM TWP-ICE campaign was used to drive the fluxes and lateral forcing. Simulation experiments were established to test the impact of each parameterization in the resulting cloud fields. Three commonly used IN spectra were utilized in the BN parameterization to describe the availability of IN for heterogeneous ice nucleation. The results showed large similarities in the cirrus cloud regime between all the schemes tested, in which ice crystal concentrations were within a factor of 10 regardless of the parameterization used. In mixed-phase clouds there were some persistent differences in cloud particle number concentration and size, as well as in cloud fraction, ice water mixing ratio, and ice water path. Contact freezing in the simulated mixed-phase clouds contributed to the effective transfer of liquid to ice, so that on average, the clouds were fully glaciated at T 260 K, irrespective of the ice nucleation parameterization used. Comparison of simulated ice water path to available satellite derived observations were also performed, finding that all the schemes tested with the BN parameterization predicted average values of IWP within ±15% of the observations.

A Method for Increasing the Turbulent Kinetic Energy in the Mellor–Yamada–Janjić Boundary-Layer Parametrization

A method for enhancing the calculation of turbulent kinetic energy in the Mellor–Yamada–Janjic planetary boundary-layer parametrization in the Weather Research and Forecasting numerical model is presented. This requires some unconventional selections for the closure constants and an additional stability dependent surface length scale. Single column model and three-dimensional model simulations are presented showing a similar performance with the existing boundary-layer parametrization, but with a more realistic magnitude of turbulence intensity closer to the surface with respect to observations. The intended application is an enhanced calculation of turbulence intensity for the purposes of a more accurate wind-energy forecast.

Assessing the performance of a prognostic and a diagnostic cloud scheme using single column model simulations of TWP–ICE

AbstractSingle column model simulations using the UK Met Office Unified Model, as used in the Australian Community Climate Earth System Simulator, are presented for the Tropical Warm Pool–International Cloud Experiment (TWP–ICE) field study. Two formulations for the representation of clouds are compared with the extensive observations taken during the campaign, giving insight into the ability of the model to simulate tropical cloud systems. During the active monsoon phase the modelled cloud cover has a stronger dependence on relative humidity than the observations. Observed ice cloud properties during the suppressed monsoon period show that the ice water content is significantly underestimated in the simulations. The profiles of modelled ice fall speeds are faster than those observed in the levels above 12 km, implying that the observations have smaller sized particles in larger concentrations than the models. Both simulations show similar errors in the diurnal cycle of relative humidity during the active monsoon phase, suggesting that the error is less sensitive to the choice of cloud scheme and rather is driven by the convection scheme. However, during the times of suppressed convection the relative humidity error is different between the simulations, with congestus convection drying the environment too much, particularly in the prognostic cloud‐scheme simulation. This result shows that the choice of cloud scheme and the way that the cloud and convection schemes interact plays a role in the temperature and moisture errors during the suppressed monsoon phase, which will impact the three‐dimensional model simulations of tropical variability. Copyright © 2011 Royal Meteorological Society

Particle concentration and flux dynamics in the atmospheric boundary layer as the indicator of formation mechanism

Abstract. We carried out column model simulations to study particle fluxes and deposition and to evaluate different particle formation mechanisms at a boreal forest site in Finland. We show that kinetic nucleation of sulphuric acid cannot be responsible for new particle formation alone as the simulated vertical profile of particle number concentration does not correspond to observations. Instead organic induced nucleation leads to good agreement confirming the relevance of the aerosol formation mechanism including organic compounds emitted by the biosphere. The simulation of aerosol concentration within the atmospheric boundary layer during nucleation event days shows a highly dynamical picture, where particle formation is coupled with chemistry and turbulent transport. We have demonstrated the suitability of our turbulent mixing scheme in reproducing the most important characteristics of particle dynamics within the boundary layer. Deposition and particle flux simulations show that deposition affects noticeably only the smallest particles in the lowest part of the atmospheric boundary layer.