Summer Afternoon Research Articles

Don't Mess With Texas Solar

2020 was the year of the unexpected, but one constant in the energy industry remained the exponential growth of solar generation in Texas, which largely continued its expansion as predicted. Electric Reliability Council of Texas’s (“ERCOT”) 2019 State of the Grid Report noted that installed solar generation capacity in ERCOT stood at 2,281 megawatts (MW) at year-end 2019, with over 67,000 MW of further solar capacity under study, exceeding even the amount of wind generation capacity under study. By July 2020, installed capacity of solar generation increased by almost 1 gigawatt (GW) to a total of 3,275 MW, representing approximately 2.2% of generating capacity in ERCOT. Solar accounted for 43% of new installed capacity in 2020, the largest share among generation types. The Solar Energy Industries Association (“SEIA”) ranked Texas fifth among the states in installed solar generation capacity in 2019, but based on its high growth rate, Texas is projected to be second only to California within the next five years. Abundant land and consistent sun make Texas an obvious candidate for significant solar generation investment, but ERCOT’s energy-only market makes solar generation with its nonexistent fuel costs especially competitive. Adjustments to the Operating Reserve Demand Curve in 2019 by the Public Utility Commission of Texas have also increased scarcity pricing and made returns more lucrative for a resource that is at its apex when demand is highest on hot, sunny summer afternoons. As this Article was being finalized for publication, the ramifications to the electric power industry in Texas of Winter Storm Uri are not yet clear. However, a preliminary assessment by Pecan Street highlighted the benefits of solar generation in a such a crisis and may spur further interest both at the generation side and behind-the-meter.

Summer afternoon precipitation associated with wind convergence near the Himalayan glacier fronts

Little is known about the effects of glacier-air interactions on the Himalayan glacier mass balance. Until this knowledge gap is filled, a reliable projection of the future changes in the Himalayan glaciers is hardly possible. Here, we describe the drying effect of the katabatic winds on the up-valley summer monsoon flows by creating favorable conditions for local convergence-induced precipitation to occur near the glacier fronts. We postulate that this retarding effect on the up-valley monsoon flows results in a negative feedback mechanism mediated by glacier-air interactions, in which glacial retreat pushes precipitation upwards as the down-valley katabatic winds weaken, resulting in greater local precipitation and enhanced snow accumulation across the upper parts of the Himalayan glaciers. Our analyses are based on the exclusive data recorded in the Khumbu valley and the Langtang valley in the Nepalese Himalayas. These data revealed higher afternoon precipitation in summer associated with surface wind convergence near the glacier fronts and a sharp decrease in the temperature lapse rate over the glacier surfaces. The principle of the observed phenomena was proven by our high-resolution modeling sensitive experiment, which involved two simulations, one with the present glaciers and the other without. This numerical experiment also supports the proposed negative feedback. Furthermore, we report a low deuterium excess near the glacier fronts, indicating below-cloud re-evaporation facilitated by the local convergence induced by the dry katabatic winds. Our study suggests that current models may overestimate the retreat of Himalayan glaciers because they have completely ignored the glacier-air interactions.

Study on the Influence of Mounting Dimensions of PV Array on Module Temperature in Open-Joint Photovoltaic Ventilated Double-Skin Façades

In building integrated photovoltaics (PV), it is important to solve the heat dissipation problem of PV modules. In this paper, the computational fluid dynamics (CFD) method is used to simulate the flow field around the open-joint photovoltaic ventilated double-skin façades (OJ-PV-DSF) to study the influence of the mounting dimensions (MD) of a PV array on the module temperature. The typical summer afternoon meteorological parameters, such as the total radiation (715.4 W/m2), the outdoor temperature (33.1 °C), and the wind speed (2.0 m/s), etc., are taken as input parameters. With the DO (discrete ordinates) model and the RNG (renormalization-group) k − ε model, a steady state calculation is carried out to simulate the flow of air in and around the cavity under the coupling of hot pressure and wind pressure, thereby obtaining the temperature distribution of the PV array and the wall. In addition, the simulation results are compared with the onsite experimental data and thermal imaging to verify the accuracy of the CFD model. Then three MD of the open joints are discussed. The results show that when the a value (represents the distance between PV modules and wall) changes from 0.05 to 0.15, the temperature drop of the PV module is the most obvious, reaching 2.0 K. When the b value (representing the distance between two adjacent PV modules in the vertical direction) changes from 0 to 0.1, the temperature drop of the PV module is most obvious, reaching 1 K. When the c value (represents the distance between two adjacent PV modules in the horizontal direction) changes from 0 to 0.1, the temperature of the PV module is lowered by 0.8 K. Thus, a = 0.1–0.15, b = 0.1 and c = 0.1 are recommended for engineering applications to effectively reduce the module temperature.

Bean Soup

Bean Soup

Probing Covert Progressions

Probing Covert Progressions

The “urban meteorology island”: a multi-model ensemble analysis

Abstract. Cities and urban areas are well-known for their impact on meteorological variables and thereby modification of the local climate. Our study aims to generalize the urban-induced changes in specific meteorological variables by introducing a single phenomenon – the urban meteorology island (UMI). A wide ensemble of 24 model simulations with the Weather Research and Forecasting (WRF) regional climate model and the Regional Climate Model (RegCM) on a European domain with 9 km horizontal resolution were performed to investigate various urban-induced modifications as individual components of the UMI. The results show that such an approach is meaningful, because in nearly all meteorological variables considered, statistically significant changes occur in cities. Besides previously documented urban-induced changes in temperature, wind speed and boundary-layer height, the study is also focused on changes in cloud cover, precipitation and humidity. An increase in cloud cover in cities, together with a higher amount of sub-grid-scale precipitation, is detected on summer afternoons. Specific humidity is significantly lower in cities. Further, the study shows that different models and parameterizations can have a strong impact on discussed components of the UMI. Multi-layer urban schemes with anthropogenic heat considered increase winter temperatures by more than 2 ∘C and reduce wind speed more strongly than other urban models. The selection of the planetary-boundary-layer scheme also influences the urban wind speed reduction, as well as the boundary-layer height, to the greatest extent. Finally, urban changes in cloud cover and precipitation are mostly sensitive to the parameterization of convection.

Why Are There More Summer Afternoon Low Clouds Over the Tibetan Plateau Compared to Eastern China?

AbstractIn this study, we analyze the relationships between summer afternoon low cloud cover and environmental conditions over the Tibetan Plateau (TP). Using in situ measurements, satellite data, and reanalysis, and based on theoretical analysis, we find that there is stronger thermal turbulence, lower temperature, and higher frequency of low cloud formation for the same surface relative humidity over the eastern and central TP compared with eastern China. With the same sensible heat flux, decreased air density enhances buoyancy flux, which increases the planetary boundary layer height and moisture vertical transport. At the same time, with the same near‐surface relative humidity, lower temperature over the TP decreases the lifting condensation level, which increases the probability of the air parcel reaching this level. Compared to the low‐elevation region in eastern China, these two mechanisms enhance low cloud occurrence in the afternoon over the TP.

Establishing an Intelligent Laundry Drying Rack Using System Innovation Theory

Laundry drying is a daily chore that every family endures. In Taiwan it is worse as the available area is limited, urban areas are densely populated, the winters are wet, and thunderstorms often occur on summer afternoons. Improving on the traditional laundry drying rack could make it an indispensable part of modern life improving the quality of life for everyone. This study uses TRIZ to improve the traditional bamboo design. First, this study collects and analyses literature related to the traditional bamboo design. Second, it then utilizes a contradiction matrix, 39 engineering parameters, and 40 invention principles in TRIZ to find the places that need to be improved and subsequently improves them. Finally, an intelligent laundry drying rack was created using sensors to detect light and rain. These synchronously trigger the control circuit, and drive the motor, so that the laundry is smoothly moved inside from outside, making laundry drying more convenient and safer.

Modeling the Effects of Lakes in the Tibetan Plateau on Diurnal Variations of Regional Climate and Their Seasonality

AbstractIn this study, we investigated the effects of lakes in the Tibetan Plateau (TP) on diurnal variations of local climate and their seasonal changes by using the Weather Research and Forecasting (WRF) Model coupled with a one-dimensional physically based lake model. We conducted WRF simulations for the TP over 2000–10, and the model showed excellent performance in simulating near-surface air temperature, precipitation, lake surface temperature, and lake-region precipitation when compared to observations. We carried out additional WRF simulations where all the TP lakes were replaced with the nearest land-use types. The differences between these two sets of simulations were analyzed to quantify the effects of the TP lakes on the local climate. Our results indicate that the strongest lake-induced cooling occurred during the spring daytime, while the most significant warming occurred during the fall nighttime. The cooling and warming effects of the lakes further inhibited precipitation during summer afternoons and evenings and motivated it during fall early mornings, respectively. This study lays a solid foundation for further exploration of the role of TP lakes in climate systems at different time scales.

Urban Heat Implications from Parking, Roads, and Cars: a Case Study of Metro Phoenix

ABSTRACT To understand the transportation sector’s role on influencing and mitigating heat in cities, this research quantifies added heat from pavement infrastructure and vehicle travel in the hot and automobile dependent metropolitan Phoenix, Arizona. Construction of a one-dimensional heat transfer model for local weather conditions and pavement design is combined with vehicle travel densities to simulate spatiotemporal sensible heat flux magnitudes. In metro Phoenix, sensible heat from pavements and vehicles is comprised of 67% from roadways, 29% from parking, and 3.9% vehicles. Concrete and asphalt pavement emit 15% and 37% more sensible heat compared to the bare ground, respectively. Added sensible heat from pavement peaks during summer afternoons when heat emissions relative to the ground are 26% and 46% greater for concrete and asphalt. Results indicate pavement infrastructure contributes significantly to Phoenix’s urban heat balance, and areas surrounding busy vehicle corridors may be undesirable for outdoor activities during summer rush hours.

Dust devils on Mars

Whirlwinds, familiar on Earth, can be informative probes of the Martian surface environment.

Surficial fractures in the Navajo sandstone, south‐western USA: the roles of thermal cycles, rainstorms, granular disintegration, and iterative cracking

AbstractDeep (> 5 m) sheeting fractures in the Navajo sandstone are evident at numerous sites in southern Utah and derive from tectonic stresses. Strong diurnal thermal cycles are, however, the likely triggers for shallow (< 0.3 m) sheeting fractures. Data from subsurface thermal sensors reveal that large temperature differences between sensors at 2 and 15 cm depth on clear summer afternoons are as great as those that trigger sheeting fractures in exposed California granite. Extensive polygonal patterns in the Navajo sandstone are composed of surface‐perpendicular fractures and were produced by contractile stresses. Numerous studies have shown that porewater diminishes the tensile strength of sandstone. Based on our thermal records, we propose that cooling during monsoonal rainstorms triggers polygonal fracturing of temporarily weakened rock. On steep outcrops, polygonal patterns are rectilinear and orthogonal, with T‐vertices. Lower‐angle slopes host hexagonal patterns (defined by the dominance of Y‐vertices). Intermediate patterns with rectangles and hexagons of similar scale are common. We posit that outcropping fractures are advancing downward by iterative steps, and that hexagons on sandstone surfaces (like prismatic columns of basalt) have evolved from ancestral orthogonal polygons of similar scale. In lava flows, fractures elongate intermittently as they follow a steep thermal gradient (the source of stress) as it rapidly moves through the rock mass. In our model, a steep, surficial thermal gradient descends through unfractured sandstone, but at the slow pace of granular disintegration. Through time, as the friable rock on stable slopes erodes, iterative cracking advances into new space. Hexagonal patterns form as new fractures, imperfectly guided by the older ones, propagate in new directions, and vertices drift into a configuration that minimizes the ratio of fracture length to polygon area. © 2020 John Wiley & Sons, Ltd.

PM2.5 and O3 pollution during 2015–2019 over 367 Chinese cities: Spatiotemporal variations, meteorological and topographical impacts

The strict Clean Air Action Plan has been in place by central and local government in China since 2013 to alleviate haze pollution. In response to implementation of the Plan, daytime PM2.5 (particulate matter with aerodynamic diameter less than 2.5 μm) showed significant downward trends from 2015 to 2019, with the largest reduction during spring and winter in the North China Plain. Unlike PM2.5, O3 (ozone) showed a general increasing trend, reaching 29.7 μg m−3 on summer afternoons. Increased O3 and reduced PM2.5 simultaneously occurred in more than half of Chinese cities, increasing to approximately three-fourths in summer. Declining trends in both PM2.5 and O3 occurred in only a few cities, varying from 19.1% of cities in summer to 33.7% in fall. Meteorological variables helped to decrease PM2.5 and O3 in some cities and increase PM2.5 and O3 in others, which is closely related to terrain. High wind speed and 24 h changing pressure favored PM2.5 dispersion and dilution, especially in winter in southern China. However, O3 was mainly affected by 24 h maximum temperature over most cities. Soil temperature was found to be a key factor modulating air pollution. Its impact on PM2.5 concentrations depended largely on soil depth and seasons; spring and fall soil temperature at 80 cm below the surface had largely negative impacts. Compared with PM2.5, O3 was more significantly affected by soil temperature, with the largest impact at 20 cm below the surface and with less seasonal variation.

A mechanistic investigation of the oasis effect in the Zhangye cropland in semiarid western China

Providing mechanistic explanations for oasis cold island effect trends expands current understanding of how land use change affects local climate in semi-arid regions globally. Data from Zhangye, Gansu, China in 2013 were used to evaluate intrinsic biophysical mechanism (IBPM) theory's ability to model the oasis effect. The land-surface temperature oasis effect is observed most intensely in summer afternoon (average difference −12.66 ± 6.6 K at 13:30 between oasis and desert sites). Observed land-surface temperature oasis effects result from differences in surface albedo, Bowen ratio, soil heat flux and air temperature. The Bowen ratio change is the strongest predictor of land-surface temperature oasis effect, with a nearly 1:1 relationship to the observed land-surface oasis effect in summer (R2 = 0.6). The IBPM theory accurately predicts oasis effects for 66% of summer daylight hours, with an average RSME of 4.72 K. Correlation analysis is performed to evaluate the impacts of meteorological conditions on observed oasis effects, showing that higher windspeed and greater atmospheric clarity produce stronger land-surface temperature oasis effects. In summer, this relationship is strongest, with an R2 value of 0.65 and RSME of 3.77. This research has implications for evaluating temperature impacts of land use change in semi-arid regions globally.

Design of Electricity Demand-Response Programs

During a heat wave in a summer afternoon, a utility firm may face unusually high demand and procurement cost for electricity. Under such conditions, a demand-response event occurs and the firm asks residential customers to reduce their demand. Such a demand-response program not only reduces the firm's procurement cost, but can also be environmentally beneficial by reducing generation from emissions-intensive power plants. In a demand-response program, a utility firm pays a rebate to customers for each unit of their demand reduction — the difference between a customer's demand and consumption. However, the demand reduction cannot be directly measured because the firm cannot observe the customer's demand, but only its consumption. Accordingly, a utility firm estimates the demand reduction by subtracting the consumption from a baseline, which is typically set as a customer's average historical demand. In this paper, we first investigate how the existence of a baseline influences a customer's demand reduction decision and when it leads to under- or over-estimation of the actual demand reduction. We then analyze how a utility firm should adjust the baseline from the customer's average demand. We find that it should inflate (deflate) the baseline if the cost difference between event and non-event periods is large (small), even though this may lead to greater overestimation (underestimation) of the customer's demand reduction. Interestingly, we show that inflation of the baseline, which one would expect makes reducing demand more attractive for a customer, can actually lead to a smaller demand reduction, resulting in higher emissions.

基于微波辐射计RPG-HATPRO的夏季午后强对流个例分析

基于微波辐射计RPG-HATPRO的夏季午后强对流个例分析

Leaving the Gay Place: Billy Lee Brammer and the Great Society

Leaving the Gay Place: Billy Lee Brammer and the Great Society

Analysis of a Haze Event over Nanjing, China Based on Multi-Source Data

We analyzed a June 2018 Nanjing, China haze event using ground-based and spaceborne sensors, combined with sounding and HYSPLIT backward trajectory data, with the ground-based and spaceborne sensor data exhibiting good consistency. Water vapor content showed significant positive correlation with AOD (aerosol optical depth), and AOD measured in urban and industrial areas was much higher compared to other similar zones. The afternoon convection caused the aerosol uplift during the haze event. Higher aerosol concentration was detected below 2 km. Due to the summer afternoon convective movement, pollutants at high altitude were dominated by small particles, while the overall pollutant mix was dominated by mixed aerosols. During a stable period over June 11–18, a single, near-surface inversion layer, and occasional two inversion layers, stopped pollutant dispersal, with only very stable ocean air mass transport in the southeast direction available. The Air Quality Index drop which took place during June 28–30 was caused by two inversion layers, combined with the immigration of pollutants from inland air masses.

An evaluation of the ability of the Ozone Monitoring Instrument (OMI) to observe boundary layer ozone pollution across China: application to 2005–2017 ozone trends

Abstract. Nadir-viewing satellite observations of tropospheric ozone in the UV have been shown to have some sensitivity to boundary layer ozone pollution episodes, but so far they have not yet been compared to surface ozone observations collected by large-scale monitoring networks. Here we use 2013–2017 surface ozone data from China's new Ministry of Ecology and Environment (MEE) network of ∼ 1000 sites, together with vertical profiles from ozonesondes and aircraft, to quantify the ability of tropospheric ozone retrievals from the Ozone Monitoring Instrument (OMI) and to detect boundary layer ozone pollution in China. We focus on summer when ozone pollution in China is most severe and when OMI has the strongest sensitivity. After subtracting the Pacific background, we find that the 2013–2017 mean OMI ozone enhancements over eastern China have strong spatial correlation with the corresponding multiyear means in the surface afternoon observations (R=0.73), and that OMI can estimate these multiyear means in summer afternoon surface ozone with a precision of 8 ppb. The OMI data show significantly higher values on observed surface ozone episode days (>82 ppb) than on non-episode days. Day-to-day correlations with surface ozone are much weaker due to OMI noise and are stronger for sites in southern China (<34∘ N; R=0.3–0.6) than in northern China (R=0.1–0.3) because of weaker retrieval sensitivity and larger upper tropospheric variability in the north. Ozonesonde data show that much of the variability of OMI ozone over southern China in summer is driven by the boundary layer. Comparison of 2005–2009 and 2013–2017 OMI data indicates that mean summer afternoon surface ozone in southern China (including urban and rural regions) has increased by 3.5±3.0 ppb over the 8-year period and that the number of episode days per summer has increased by 2.2±0.4 (as diagnosed by an extreme value model), generally consistent with the few long-term surface records. Ozone increases have been particularly large in the Yangtze River Delta and in the Hubei, Guangxi and Hainan provinces.

Total solar eclipse effects on evapotranspiration captured by groundwater fluctuations in a Southern Appalachian fen

AbstractSolar eclipses provide opportunities to observe unusual natural phenomena. This paper presents data showing that diurnal groundwater fluctuations were briefly interrupted in a Southern Appalachian fen following a total solar eclipse on August 21, 2017. Groundwater levels, which were rapidly declining in the middle of a summer afternoon, nearly stabilized following totality. This anomaly in the water‐level record was caused by reduced evapotranspiration (ET). ET was significantly lower (36% ± 11%, p < 0.02) over a 45‐min time period following the eclipse when compared with other days within the study period, although the effects were short lived and did not have a significant impact on the daily total ET (p > 0.05). These findings may prompt evaluation of existing groundwater records along the path of totality from past eclipses or plan for studies ahead of future eclipses.