Sensitivity Simulations Research Articles

Anatomy of a Summertime Convective Event over the Arabian Region

Abstract This study investigates the structure and evolution of a summertime convective event that occurred on 14 July 2015 over the Arabian region. We use the WRF Model with 1-km horizontal grid spacing and test three PBL parameterizations: the Mellor–Yamada–Nakanishi–Niino (MYNN) scheme; the Asymmetrical Convective Model, version 2, (ACM2) scheme; and the quasi-normal scale-elimination (QNSE) scheme. Convection initiates near the Al Hajar Mountains of northern Oman at around 1100 local time (LT; 0700 UTC) and propagates northwestward. A nonorographic convective band along the west coast of the United Arab Emirates (UAE) develops after 1500 LT as a result of the convergence of cold pools with the sea breeze from the Arabian Gulf. The model simulation employing the QNSE scheme simulates the convection initiation and propagation well. Although the MYNN and ACM2 simulations show convective initiation near the Al Hajar Mountains, they fail to simulate the development of the convective band along the UAE west coast. The MYNN run simulates colder near-surface temperatures and a weaker sea breeze, whereas the ACM2 run simulates a stronger sea breeze but a drier lower troposphere. Sensitivity simulations using horizontal grid spacings of 9 and 3 km show that lower-resolution runs develop broader convective structures and weaker cold pools and horizontal wind divergence, affecting the development of convection along the west coast of the UAE. The 1-km run using the QNSE PBL scheme realistically captures the sequence of events that leads to the moist convection over the UAE and adjacent mountains.

Simulation of Pulverized Coal Combustion Process Considering Turbulence-Radiation Interaction.

In this paper, the combustion process of a 350 MW opposite pulverized coal combustion boiler is studied using a combined field test and numerical simulation. Considering the turbulence-radiation interaction (TRI) effect caused by turbulent particle pulsation during the combustion process, the TRI model is modified by introducing optical factors. The interaction between the optical thickness and the radiation pulsation of pulverized coal particles during the combustion process is studied to learn the influences of turbulent particle combustion on radiative heat transfer. According to the analysis of the TRI influence on pulverized coal combustion, the temperature of the cross section decreases with TRI. Compared with the traditional radiation model calculation, the time-average temperature of the cross section is reduced by 49.85 K, and the deviation from the experimental data is reduced by 1.54%. It is proved that the temperature distribution in the furnace considering TRI is closer to reality. In the numerical simulation of the TRI sensitivity to the optical thickness of the particles, it is found that with TRI, the increase of optical thickness will strengthen the effect of turbulent kinetic energy in the combustion area. Due to the increase in particle density, the content of the main radiation medium produced by combustion, H2O and CO2, increases and the radiation effect in the furnace is enhanced. In the fire area with dense particles, the average temperature of the cross section increases by 28 K. Hence, the change in optical thickness causes the change of TRI parameters, and the TRI effect becomes more significant with the increase of particle load.

Non-local integral-type damage combined to mean-field homogenization methods for composites and its parallel implementation

Modern lightweight materials are often decomposed into several distinct materials, e.g. a matrix material and some reinforcements. A manufacturing process for these materials often induces eigenstrains, both reversible and non reversible. This could lead to an initial damage of a composite material, and eventually result into fracture of the structure. This contribution deals with non-local integral-type damage of composites subjected to eigenstrains. It is well known that local damage models lead to mesh sensitive simulation results. To avoid this effect, non-local integral-type regularization of equivalent strains and damage variables are exploited. Effective macroscopic properties are obtained using mean-field homogenization methods. A regularization in each material phase within the framework of an iterative Newton–Raphson procedure leads to the update of a non-local tangent stiffness matrix at each equilibrium iteration. To reduce the computational time parallel non-local assembly and averaging procedures are introduced. In this regard, the performance of different representations of dynamic sparse matrices and the scalability of the parallel implementation are investigated. Various microstructural morphologies are distinguished in representative examples to show the capability of the proposed work. Furthermore, the transition from damage to fracture is performed by aid of an element deletion method. To achieve the best compromise between memory consumption and speed over a range of non-zero entries, an array of flatmaps should be used. It is shown that the introduced parallel algorithms enable a drastic reduction of computational time. Moreover, it is illustrated that for various volume fractions of an inclusion a mesh sensitivity is clearly reduced.

Influences of Urbanization on an Afternoon Heavy Rainfall Event over the Yangtze River Delta Region

Abstract An afternoon heavy rainfall event occurred over coastal Nantong, an area of 70–100 km downstream from the Shanghai–Suzhou–Wuxi–Changzhou city belt over the Yangtze River Delta, under the influences of weak southwesterly monsoonal flows and lake/sea breezes on 26 July 2018. An observational analysis shows the emergence of pronounced urban heat island (UHI) effects along the city belt during the late morning hours. A series of nested-grid cloud-permitting model simulations with the finest grid spacing of 1 km are performed to examine the impacts of urbanization on convection initiation (CI) and the subsequent heavy rainfall event. Results reveal the generation of lake breezes and warm anomalies in the planetary boundary layer along the city belt and low-level convergence, thereby inducing upward motion for CI. The southwesterly flows of the monsoonal warm–moist air, enhanced by the UHI effects along the city belt, allow the development of convective cells along the city belt, some of which merge with convective clusters during their downstream propagation, and the ultimate generation of several distinct heavy rainfall centers by local convective clusters over coastal Nantong where atmospheric columns are more moist and potentially unstable under the influences of sea breezes. Sensitivity simulations show small contribution of Nantong’s UHI effects to the heavy rainfall event. The above findings help elucidate how the UHI effects could assist the CI in a weak-gradient environment, and explain why urbanization can contribute to increased downwind mean and extreme precipitation under the influences of favorable regional forcing conditions. Significance Statement The urban heat island (UHI) effects tend to produce more rainfall on its downwind side than that on the other sides, but alone could hardly account for the generation of heavy rainfall. This study examines the influences of the UHI effects associated with a city belt over the Yangtze River Delta on generating an afternoon heavy rainfall event over coastal Nantong that is 70–100 km downwind from the city belt. Results show (i) the downwind advection of the UHI effects; (ii) the initiation of convective storms along the city belt, and their subsequent downstream propagation, leading to the generation of heavy rainfall over Nantong; and (iii) an important role of sea breezes in generating the heavy rainfall event.

Weakening of the Summer Monsoon Over the Past 150 Years Shown by a Tree‐Ring Record From Shandong, Eastern China, and the Potential Role of North Atlantic Climate

AbstractThe causes of the decreased intensity of the East Asian summer monsoon (EASM) over the past 150 years are still not fully understood, although several studies have linked the monsoon weakening to the warming of tropical oceans. Here, we use pine tree‐rings to reconstruct the precipitation total for April–August from 1810 to 2018, in south‐central Shandong Province, in the EASM region. The reconstruction accounts for 41.8% of the instrumental precipitation variance during 1965–2018. The EASM precipitation reconstruction shows extreme pluvial conditions in 1832, 1833, 1886, and 1998, and extreme droughts in 1878, 1901, and 1910, which correspond precisely to extreme climatic events recorded in historical documents. The reconstructed precipitation reveals a drying trend since the 1870s, which matches well with the decreasing trend of the EASM inferred from stalagmite oxygen isotope (δ18O) records and climate simulations. The trend of decreasing precipitation since the 1870s, indicated by our reconstruction, is significantly correlated with the spring sea surface temperature (SST) of the North Atlantic Ocean, which suggests that the EASM weakening was linked to North Atlantic SST variations during the past 150 years. This potential role of North Atlantic SST variability is supported by climate sensitivity simulations of the Community Earth System Model. North Atlantic SST variability induces two teleconnections of Rossby‐like wave propagation from the North Atlantic into East Asia, resulting in anomalous precipitation in this region.

Heavy snowfall event over the Swiss Alps: did wind shear impact secondary ice production?

Abstract. The change in wind direction and speed with height, referred to as vertical wind shear, causes enhanced turbulence in the atmosphere. As a result, there are enhanced interactions between ice particles that break up during collisions in clouds which could cause heavy snowfall. For example, intense dual-polarization Doppler signatures in conjunction with strong vertical wind shear were observed by an X-band weather radar during a wintertime high-intensity precipitation event over the Swiss Alps. An enhancement of differential phase shift (Kdp>1∘ km−1) around −15 ∘C suggested that a large population of oblate ice particles was present in the atmosphere. Here, we show that ice–graupel collisions are a likely origin of this population, probably enhanced by turbulence. We perform sensitivity simulations that include ice–graupel collisions of a cold frontal passage to investigate whether these simulations can capture the event better and whether the vertical wind shear had an impact on the secondary ice production (SIP) rate. The simulations are conducted with the Consortium for Small-scale Modeling (COSMO), at a 1 km horizontal grid spacing in the Davos region in Switzerland. The rime-splintering simulations could not reproduce the high ice crystal number concentrations, produced too large ice particles and therefore overestimated the radar reflectivity. The collisional-breakup simulations reproduced both the measured horizontal reflectivity and the ground-based observations of hydrometeor number concentration more accurately (∼20 L−1). During 14:30–15:45 UTC the vertical wind shear strengthened by 60 % within the region favorable for SIP. Calculation of the mutual information between the SIP rate and vertical wind shear and updraft velocity suggests that the SIP rate is best predicted by the vertical wind shear rather than the updraft velocity. The ice–graupel simulations were insensitive to the parameters in the model that control the size threshold for the conversion from ice to graupel and snow to graupel.

Impact of changes in refractive indices of secondary organic aerosols on precipitation over China during 1980–2019

Secondary organic aerosols (SOAs), which include both colorless and colored carbonaceous aerosols, represent a major type of aerosol globally. Previous studies have reported that colored aerosols drive the well-known precipitation changes over southern China called the south-flood north-drought (SFND). Considering the highest concentration of SOA in China, SOAs can cause fluctuations in the precipitation system over China. However, studies on the climatic effects of SOAs over East Asia are scarce owing to the chemical complexity of SOAs and high computational cost. Therefore, to investigate the effect of SOAs on the precipitation change over China, we implemented an SOA scheme using empirical parameters in the chemistry-climate model. We performed a control and two sensitivity simulations depending on the difference in refractive indices of SOAs to elucidate the effects of light absorption by SOAs on precipitation. Our results suggest that strong light absorption by SOAs strengthens the convective precipitation over southern China following the enhancement of atmospheric stability with a secondary circulation effect. However, the surface temperature changes caused by SOAs shift the jet core if weak light absorption by SOAs is assumed, causing a strong downdraft in the mid-troposphere and decreasing humidity over south-eastern China. Therefore, precipitation was significantly reduced over southern China. Our results show that light-absorbing SOAs have had a significant impact on precipitation in southern China for the past few decades. Furthermore, the apparent difference in mechanisms of precipitation change between strong and weak light absorption by SOAs suggests the importance of choosing suitable refractive indices for SOAs in the climate–atmospheric chemistry model.

Implementation of HONO into the chemistry–climate model CHASER (V4.0): roles in tropospheric chemistry

Abstract. Nitrous acid (HONO) is an important atmospheric gas given its contribution to the cycles of NOx and HOx, but its role in global atmospheric photochemistry is not fully understood. This study implemented three pathways of HONO formation in the chemistry–climate model CHASER (MIROC-ESM) to explore three physical phenomena: gas-phase kinetic reactions (GRs), direct emission (EM), and heterogeneous reactions on cloud and aerosol particles (HRs). We evaluated the simulations by the atmospheric aircraft-based measurements from EMeRGe-Asia-2018 (Effect of Megacities on the Transport and Transformation of Pollutants on the Regional to Global Scales), ATom-1 (atmospheric tomography), observations from the ship R/V Mirai, EANET (Acid Deposition Monitoring Network in eastern Asia)/EMEP (European Monitoring and Evaluation Programme) ground-based stationary observations, and the OMI (Ozone Monitoring Instrument). We showed that the inclusion of the HONO chemistry in the modelling process reduced the model bias against the measurements for PM2.5, NO3-/HNO3, NO2, OH, HO2, O3, and CO, especially in the lower troposphere and the North Pacific (NP) region. We found that the retrieved global abundance of tropospheric HONO was 1.4 TgN. Of the three source pathways, HRs and EM contributed 63 % and 26 % to the net HONO production, respectively. We also observed that reactions on the aerosol surfaces contributed larger amounts of HONO (51 %) than those on the cloud surfaces (12 %). The model exhibited significant negative biases for daytime HONO in the Asian off-the-coast region, compared with the airborne measurements by EMeRGe-Asia-2018, indicating the existence of unknown daytime HONO sources. Strengthening of aerosol uptake of NO2 near the surface and in the middle troposphere, cloud uptake, and direct HONO emission were all potential yet-unknown HONO sources. The most promising daytime source for HONO found in this study was the combination of enhanced aerosol uptake of NO2 and surface-catalysed HNO3 photolysis (maxST+JANO3-B case), which could also remedy the model bias for NO2 and O3 during EMeRGe. We also found that the simulated HONO abundance and its impact on NOx–O3 chemistry were sensitive to the yield of the heterogeneous conversion of NO2 to HONO (vs. HNO3). Inclusion of HONO reduced global tropospheric NOx (NO + NO2) levels by 20.4 %, thereby weakening the tropospheric oxidizing capacity (OH, O3) occurring for NOx-deficit environments (remote regions and upper altitudes), which in turn increased CH4 lifetime (13 %) and tropospheric CO abundance (8 %). The calculated reduction effect on the global ozone level reduced the model overestimates for tropospheric column ozone against OMI spaceborne observations for a large portion of the North Hemisphere. HRs on the surfaces of cloud particles, which have been neglected in previous modelling studies, were the main drivers of these impacts. This effect was particularly salient for the substantial reductions of levels of OH (40 %–67 %) and O3 (30 %–45 %) in the NP region during summer, given the significant reduction of the NOx level (50 %–95 %). In contrast, HRs on aerosol surfaces in China (Beijing) enhanced OH and O3 winter mean levels by 600 %–1700 % and 10 %–33 %, respectively, with regards to their minima in winter. Furthermore, sensitivity simulations revealed that the heterogeneous formation of HONO from NO2 and heterogenous photolysis of HNO3 coincided in the real atmosphere. Nevertheless, the global effects calculated in the combined case (enhancing aerosol uptakes of NO2 and implementing heterogeneous photolysis of HNO3), which most captured the measured daytime HONO level, still reduced the global tropospheric oxidizing capacity. Overall, our findings suggest that a global model that does not consider HONO heterogeneous mechanisms (especially photochemical heterogeneous formations) may erroneously predict the effect of HONO in remote areas and polluted regions.

Modeling the impact of combined use of COVID Alert SA app and vaccination to curb COVID-19 infections in South Africa.

The unanticipated continued deep-rooted trend of the Severe Acute Respiratory Syndrome Corona-virus-2 the originator pathogen of the COVID-19 persists posing concurrent anxiety globally. More effort is affixed in the scientific arena via continuous investigations in a prolific effort to understand the transmission dynamics and control measures in eradication of the epidemic. Both pharmaceutical and non-pharmaceutical containment measure protocols have been assimilated in this effort. In this study, we develop a modified SEIR deterministic model that factors in alternative-amalgamation of use of COVID Alert SA app and vaccination against the COVID-19 to the Republic of South Africa's general public in an endeavor to discontinue the chain of spread for the pandemic. We analyze the key properties of the model not limited to positivity, boundedness, and stability. We authenticate the model by fitting it to the Republic of South Africa's cumulative COVID-19 cases reported data utilizing the Maximum Likelihood Estimation algorithm implemented in fitR package. Sensitivity analysis and simulations for the model reveal that simultaneously-gradually increased implementation of the COVID Alert SA app use and vaccination against COVID-19 to the public substantially accelerate reduction in the plateau number of COVID-19 infections across all the observed vaccine efficacy scenarios. More fundamentally, it is discovered that implementing at least 12% app use (mainly for the susceptible population not vaccinated) with simultaneous vaccination of over 12% of the susceptible population majorly not using the app using a vaccine of at least 50% efficacy would be sufficient in eradicating the pandemic over relatively shorter time span.

Soil moisture-constrained East Asian Monsoon meridional patterns over China from observations

As an internal forcing of the earth climate system, soil moisture (SM) significantly influences the water and energy cycle by controlling evapotranspiration and terrestrial solar energy. The current study used observed precipitation, remotely sensed SM, and reanalysis of atmosphere and land parameters to assess the East Asian Monsoon (EAM) precipitation variability due to meridional SM oscillations across China. A generalized linear method, namely coupled manifold technique (CMT) for assessing the reciprocal forcing between two climate fields and numerical simulations are applied to SM and EAM precipitation. We find that the EAM precipitation interannual variability between north and south China significantly correlates with SM meridional oscillation. The CMT results further showed that SM forcing has a significant (99% confidence) influence on the EAM precipitation explaining about 0.40 of the variance ratio in north and south China. The EAM and SM composite analysis show that the wetter (drier) north (south) oscillates the EAM precipitation over the north (south) of China and vice versa due to SM thermal controls. We then used control and sensitivity simulations with SM observations to further validate the findings implying that SM can potentially improve the interannual EAM forecast skills. The model results show that a wetter (drier) north (south) results in negative (positive) sensible heat (latent heat) anomalies that impact the boundary layer and propagate to change the meridional atmospheric heating profile. When positive (negative) SM anomalies exist over northern (southern) China, the zonal easterlies and extratropical westerlies move to north China causing above-normal precipitation that descends into southern China, suppressing subtropical westerlies and precipitation in southern China. On the contrary, a dry (wet) north (south) favors intensified subtropical westerlies and precipitation in southern China. The findings have dire implications for the water and energy cycle of the region in the projected wetting and drying patterns of the north (south).

Validation and optimization of the epithermal neutron flux detector using the 71Ga(n,γ)72Ga reaction

An intense epithermal neutron flux is necessary for boron neutron capture therapy (BNCT), a promising technique for the treatment of malignant tumors. The epithermal neutron flux is an essential characteristic of the BNCT neutron beam and its measurement is directly related to the reliability of the treatment planning system. Such a tool could be a cylindrical activation detector using 71Ga(n,γ)72Ga reaction. This paper describes a detector made in the likeness of the previously proposed one and presents the results of numerical simulation of the detector sensitivity and its experimental use. The paper notes the difference between the simulated sensitivity of the detector and the sensitivity of the previously proposed one and makes assumptions about the reason for this difference. The work also proposes an improvement of the detector, which allows not only to reduce the contribution of fast neutrons to the detector sensitivity, but also to provide a new opportunity to refine the spectrum of neutrons that are most effective for the treatment of deep-seated tumors.

Tracking Urban Footprint on Extreme Precipitation in an African Megacity

Abstract This study contributes to the body of current knowledge about the urban effect on extreme precipitation (EP) by investigating the city–EP interaction over Lagos, Nigeria. This is a unique, first-time study that adds a “missing piece” of this information about the African continent to the comprehensive global urban precipitation “puzzle.” The convection-permitting Weather Research and Forecasting (WRF) Model is employed within an ensemble simulation framework using combinations of different physical schemes and boundary/initial conditions to detect the urban signal on an extreme rainfall event that occurred on 30 May 2006. WRF simulations are verified against satellite-estimated and in situ observations, and the results from the best-performing ensemble members are used for analysis. The results show that the control simulation with urban representation generated 20%–30% more rainfall over the urban area than the nonurban sensitivity simulation, in which the city is replaced by forest. Physical mechanisms behind the differences were revealed. We found that the urbanization in Lagos reduced evapotranspiration, resulting in the increase of sensible heating (by 75 W m−2). This further enhances the urban heat-island effect (+1.5 K of air surface temperature), facilitating horizontal convergence and boosting daytime sea breeze. As a result, more moisture is transported from the southern sea area to inland areas; the moisture then converges over Lagos city, creating favorable conditions for enhancing convection and extreme-rainfall-generating processes.

Climate Variations in the Past 250 Million Years and Contributing Factors

AbstractWe simulate climate variations in the past 250 million years (Myr), using the fully coupled Community Earth System Model version 1.2.2 (CESM1.2.2) with the Community Atmosphere Model version 4 (CAM4). Three groups of simulations are performed, each including 26 simulations, with a 10‐million‐year interval. The Control group is constrained by paleogeography, increasing solar radiation, and reconstructed global mean surface temperatures (GMSTs) by tuning CO2 concentrations. No ice sheets are prescribed for all simulations except for the pre‐industrial (PI) simulation in which modern geography, ice sheets and vegetation are used. Simulated zonal mean surface temperatures are always higher than those of proxy reconstructions in the tropics, but lower than those of proxy reconstructions at middle latitudes. The relative importance of individual contributing factors for surface temperature variations in the past 250 Myr is diagnosed, using the energy‐balance analysis. Results show that greenhouse gases are the major driver in regulating GMST variations, with a maximum contribution of 12.2°C. Varying surface albedo contributes to GMST variations by 3.3°C. Increasing solar radiation leads to GMST increases by 1.5°C. Cloud radiative effects have relatively weak impacts on GMST variations, less than ±0.8°C. For comparison, two groups of sensitivity simulations are performed. One group has the CO2 concentration fixed at 10 times the PI value, and the other group has fixed CO2 concentration of 10 times the PI value and fixed solar radiation at the present‐day value, showing that varying both paleogeography and solar constant and varying paleogeography alone result in GMST changes by 7.3°C and 5.6°C, respectively.

The Effects of Trash, Residential Biofuel, and Open Biomass Burning Emissions on Local and Transported PM2.5 and Its Attributed Mortality in Africa.

Long-term exposure to ambient fine particulate matter (PM2.5) is the second leading risk factor of premature death in Sub-Saharan Africa. We use GEOS-Chem to quantify the effects of (a) trash burning, (b) residential solid-fuel burning, and (c) open biomass burning (BB) (i.e., landscape fires) on ambient PM2.5 and PM2.5-attributable mortality in Africa. Using a series of sensitivity simulations, we excluded each of the three combustion sources in each of five African regions. We estimate that in 2017 emissions from these three combustion sources within Africa increased global ambient PM2.5 by 2%, leading to 203,000 (95% confidence interval: 133,000-259,000) premature mortalities yr-1 globally and 167,000 premature mortalities yr-1 in Africa. BB contributes more ambient PM2.5-related premature mortalities per year (63%) than residential solid-fuel burning (29%) and trash burning (8%). Open BB in Central Africa leads to the largest number of PM2.5-attributed mortalities inside the region, while trash burning in North Africa and residential solid-fuel burning in West Africa contribute the most regional mortalities for each source. Overall, Africa has a unique ambient air pollution profile because natural sources, such as windblown dust and BB, contribute strongly to ambient PM2.5 levels and PM2.5-related mortality. Air pollution policies may need to focus on taking preventative measures to avoid exposure to ambient PM2.5 from these less-controllable sources.

Summertime ozone pollution in China affected by stratospheric quasi-biennial oscillation

Abstract. In recent years, the near-surface ozone (O3) level has been rising fast in China, with increasing damage to human health and ecosystems. In this study, the impact of stratospheric quasi-biennial oscillation (QBO) on interannual variations in summertime tropospheric O3 over China is investigated based on GEOS-Chem model simulations and satellite retrievals. QBO has a significant positive correlation with near-surface O3 concentrations over central China (92.5–112.5∘ E, 26–38∘ N) when the sea surface temperature (SST) over the eastern tropical Pacific is warmer than normal, with a correlation coefficient of 0.53, but QBO has no significant effect on O3 under the cold SST anomaly. Compared to the easterly phase of QBO, the near-surface O3 concentrations have an increase of up to 3 ppb (5 % relative to the average) over central China during its westerly phase under the warm SST anomaly. O3 also increases above the surface and up to the upper troposphere, with a maximum increase of 2–3 ppb (3 %–5 %) in 850–500 hPa over central China when comparing westerly phase to easterly phase. Process-based analysis and sensitivity simulations suggest that the O3 increase over central China is mainly attributed to the anomalous downward transport of O3 during the westerly phase of QBO when a warm SST anomaly occurs in the eastern tropical Pacific, while the local chemical reactions and horizontal transport processes partly offset the O3 increase. This work suggests a potentially important role of QBO and the related vertical transport process in affecting near-surface O3 air quality, with an indication for O3 pollution prediction and prevention.

New Approaches to Project Risk Assessment Utilizing the Monte Carlo Method

An environment of turbulence in the market in recent years and increasing inflation, mainly as a result of the post-COVID period and the ongoing military operation in Ukraine, represents a significant financial risk factor for many companies, which has a negative impact on managerial decisions. A lot of enterprises are forced to look for ways to effectively assess the riskiness of the projects that they would like to implement in the future. The aim of the article is to present a new approach for companies with which to assess the riskiness of projects. The basis of this is the use of the new Crystal Ball software tool and the effective application of the Monte Carlo method. The article deals with the current issues of investment and financial planning, which are the basic pillars for effective management decisions with the goal of sustainability. The article has verified a methodology that allows companies to make effective investment decisions based on assessing the level of risk. For practical application, the Monte Carlo method was chosen, as it uses sensitivity analysis and simulations, which were evaluated for two types of projects. Both simulations were primarily carried out based on a deterministic approach through traditional mathematical models. Subsequently, stochastic modeling was performed using the Crystal Ball software tool. As a result of the sensitivity analysis, two tornado graphs were created, which display risk factors according to the degree of their influence on the criterion value. The output of this article is the presentation of these new approaches for financial decision-making within companies.

Diagnosing Near-Surface Model Errors with Candidate Physics Parameterization Schemes for the Multiphysics Rapid Refresh Forecast System (RRFS) Ensemble during Winter over the Northeastern United States and Southern Great Plains

Abstract During the winter of 2020/21 an ensemble of FV3-LAM forecasts was produced over the contiguous United States for the Winter Weather Experiment using five physics suites. These forecasts are evaluated with the goal of optimizing physics parameterizations within the future operational Rapid Refresh Forecast System (RRFS) in the Unified Forecast System (UFS) realm and for selecting suitable physics suites for a multiphysics RRFS ensemble. The five physics suites have different combinations of land surface models (LSMs), planetary boundary layer (PBL) parameterizations, and surface layer schemes, chosen from those used in current and possible future operational systems and likely to be supported in the operational UFS. Full-season evaluation reveals a persistent near-surface cold bias in the U.S. Northeast from one suite and a nighttime warm bias in the southern Great Plains in another suite, while other suites have smaller biases. A representative case is chosen to diagnose the cause for each of these biases using sensitivity simulations with different physics combinations or modified parameters and verified with additional mesonet observations. The cold bias in the Northeast is attributed to aspects of the Noah-MP LSM over snow cover, where Noah-MP simulates lower soil water content, and thus lower thermal conductivity than other LSMs, leading to less upward ground heat flux during nighttime and consequently lower surface temperature. The nighttime warm bias found in the southern Great Plains is attributed to overestimation of vertical mixing in the K-profile-based eddy-diffusivity mass-flux (K-EDMF) PBL scheme and insufficient land–atmospheric coupling from the GFS surface layer scheme over short vegetation. A few key parameters driving these systematic biases are identified.

Instability Mechanism and Control Method of Surrounding Rock of Water-Rich Roadway Roof

Surrounding rock properties and occurrence stability of a coal seam roof are prerequisites for ensuring the safe and efficient operation of mines. In this study, the mechanisms and control of weakened water-rich roadway roof slabs were investigated regarding the engineering background of water-rich roadway roof slab destabilization in a coal mine in the western Qingyang mining area. The spatial and temporal evolution law of rock deformation and damage of such roadways during excavation were determined through field measurements. First, we tested the strength of the roof slab surrounding rock in water-rich roadways with different water contents and concluded that the primary and excavation-disturbing fissures of the coal-sedimentary rock body are the external conditions for the occurrence of water–rock interaction in water-rich coal seam roadways. Moreover, the rock mechanical damage phenomenon exhibited by clay minerals in contact with water is the key factor leading to the destabilization of the water-rich roof slab’s surrounding rock. Second, a technical approach for controlling the stability of the surrounding rock by adjusting the form of the roadway section and optimizing the support parameters was proposed, and the distribution law of the surrounding rock stress field and displacement field of each section was revealed via numerical calculation. It is considered that adjustment of the stress and displacement control of the surrounding rock of the roadway is more favorable for the straight wall circular arch section. Based on the results of the sensitive orthogonal numerical simulation test, the technical parameters and scheme of the roadway support optimization were proposed. Finally, the research results were applied in the field, and the deformations of the top and bottom slab and the two ribs of the roadway after optimizing the section and support parameters were calculated as 61% and 34% lower, respectively, than those before optimization, indicating that the proposed approach can effectively control the deformation of the water-rich roadway’s surrounding rock and achieve more economic and effective stability control of this type of roadway. The research results provide new ideas and methods for controlling the surrounding rock of water-rich soft rock roadways in the western mining areas of China, which has broad application value and prospects.

Aerosol sensitivity simulations over East Asia in a convection-permitting climate model

Aerosol sensitivity simulations over East Asia in a convection-permitting climate model

How do Cl concentrations matter for the simulation of CH4 and δ13C(CH4) and estimation of the CH4 budget through atmospheric inversions?

Abstract. Atmospheric methane (CH4) concentrations have been rising since 2007 due to an imbalance between CH4 sources and sinks. The CH4 budget is generally estimated through top-down approaches using chemistry transport models (CTMs) and CH4 observations as constraints. The atmospheric isotopic CH4 composition, δ13C(CH4), can also provide additional constraints and helps to discriminate between emission categories. Nevertheless, to be able to use the information contained in these observations, the models must correctly account for processes influencing δ13C(CH4). The oxidation by chlorine (Cl) likely contributes less than 5 % to the total oxidation of atmospheric CH4. However, the large kinetic isotope effect of the Cl sink produces a large fractionation of 13C, compared with 12C in atmospheric CH4, and thus may strongly influence δ13C(CH4). When integrating the Cl sink in their setup to constrain the CH4 budget, which is not yet standard, atmospheric inversions prescribe different Cl fields, therefore leading to discrepancies between flux estimates. To quantify the influence of the Cl concentrations on CH4, δ13C(CH4), and CH4 budget estimates, we perform sensitivity simulations using four different Cl fields. We also test removing the tropospheric and the entire Cl sink. We find that the Cl fields tested here are responsible for between 0.3 % and 8.5 % of the total chemical CH4 sink in the troposphere and between 1.0 % and 1.6 % in the stratosphere. Prescribing these different Cl amounts in atmospheric inversions can lead to differences of up to 53.8 Tg CH4 yr−1 in global CH4 emissions and of up to 4.7 ‰ in the globally averaged isotopic signature of the CH4 source δ13C(CH4)source), although these differences are much smaller if only recent Cl fields are used. More specifically, each increase by 1000 molec.cm-3 in the mean tropospheric Cl concentration would result in an adjustment by +11.7 Tg CH4 yr−1, for global CH4 emissions, and −1.0 ‰, for the globally averaged δ13C(CH4)source. Our study also shows that the CH4 seasonal cycle amplitude is modified by less than 1 %–2 %, but the δ13C(CH4) seasonal cycle amplitude can be significantly modified by up to 10 %–20 %, depending on the latitude. In an atmospheric inversion performed with isotopic constraints, this influence can result in significant differences in the posterior source mixture. For example, the contribution from wetland emissions to the total emissions can be modified by about 0.8 % to adjust the globally averaged δ13C(CH4)source, corresponding to a 15 Tg CH4 yr−1 change. This adjustment is small compared to the current wetland source uncertainty, albeit far from negligible. Finally, tested Cl concentrations have a large influence on the simulated δ13C(CH4) vertical profiles above 30 km and a very small impact on the simulated CH4 vertical profiles. Overall, our model captures the observed CH4 and δ13C(CH4) vertical profiles well, especially in the troposphere, and it is difficult to prefer one Cl field over another based uniquely on the available observations of the vertical profiles.