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Boreal wintertime planetary-scale atmospheric circulations and their possible consequences to widespread fog occurrences over the Indo-Gangetic Plains (IGP) region of the Himalayan valley are investigated in this study. Among the different fog types, radiation fog type seen at night or early morning hours favored by large-scale subsidence aloft and strong near-surface inversion is focused in this study. A composite analysis reveals that upper air circulation associated with 105 fog days over the IGP region show a trail linked to circulation anomalies over the Eurasian continents and the Arctic Circle. The findings suggest that there is a footprint of the Arctic Oscillation (AO) and conventional Eurasian (EU) circulation patterns linked to anticyclonic circulation aloft over the IGP region. Although widespread IGP fog occurrences under the large-scale subsidence environment are seen to occur during both phases of AO, the negative AO phase (high pressure environment over the Arctic Circle) portends a greater likelihood for fog occurrences in the IGP region. A coupling of positive mid-tropospheric height anomalies over western Eurasia and the anticyclonic circulation anomalies over the IGP region is evident during the IGP fog periods concomitant with EU positive (height excess over Siberia) phase. Further, anomalous circulation over the IGP region during the fog periods appears to rely more on the strength of the AO negative phase than the circulation strengths over Eurasia. On the contrary, the Eurasian circulation largely appears to influence the subsidence aloft over the IGP region irrespective of the strength of the AO positive phase. It is also noted that upper-air circulation during non-foggy periods over the IGP region has conformity with positive AO phase and rapidly progressing EU pattern. These planetary-scale teleconnection pathways offer new dynamical insights into comprehending widespread IGP fog scenario, which have been hitherto perceived mostly from a regional context.

This book introduces unmanned aircraft systems traffic management (UTM) and how this new paradigm in traffic management integrates unmanned aircraft operations into national airspace systems. Exploring how UTM is expected to operate, including possible architectures for UTM implementations, and UTM services, including flight planning, strategic coordination, and conformance monitoring, Unmanned Aircraft Systems Traffic Management: UTM considers the boundaries of UTM and how it is expected to interlace with tactical coordination systems to maintain airspace safety. The book also presents the work of the global ecosystem of players advancing UTM, including relevant standards development organizations (SDOs), and considers UTM governance paradigms and challenges. FEATURES Describes UTM concept of operations (ConOps) and global variations in architectures Explores envisioned UTM services, including flight planning, strategic coordination, conformance monitoring, contingency management, constraints and geo-awareness, and remote identification Highlights cybersecurity standards development and awareness Covers approaches to the approval, management, and oversight of UTM components and ecosystem Considers the future of UTM and potential barriers to its success, international coordination, and regulatory reform This book is an essential, in-depth, annotated resource for developers, unmanned aircraft system operators, pilots, policy makers, researchers, and academics engaged in unmanned systems, transportation management, and the future of aviation.

Amplified and persistent ridges in western North America are recurring features associated with drought conditions in California. The recent drought event (2012–2016) lasted through both La Niña and El Niño episodes, suggesting additional climate drivers are important in addition to the commonly perceived El Niño‐Southern Oscillation. Diagnostic analyses presented here suggest that, while the Pacific North American (PNA) and North Pacific Oscillation (NPO) do not directly cause drought in California, the relationships between them and with the upper air circulation pattern do modulate the spatial drought pattern. The positive PNA relative circulation leads drier northern California, and (‐NPO) relative circulation leads southern California to be drier. The types of drought in this region emerge mostly from the combination of two PNA and NPO relative oceanic and atmospheric oscillations. At present, climate model projections do not indicate any significant change in these particular drought‐modulating processes.

Mountains are key features of the Earth’s surface and host a substantial proportion of the world’s species. However, the links between the evolution and distribution of biodiversity and the formation of mountains remain poorly understood. Here, we integrate multiple datasets to assess the relationships between species richness in mountains, geology and climate at global and regional scales. Specifically, we analyse how erosion, relief, soil and climate relate to the geographical distribution of terrestrial tetrapods, which include amphibians, birds and mammals. We find that centres of species richness correlate with areas of high temperatures, annual rainfall and topographic relief, supporting previous studies. We unveil additional links between mountain-building processes and biodiversity: species richness correlates with erosion rates and heterogeneity of soil types, with a varying response across continents. These additional links are prominent but under-explored, and probably relate to the interplay between surface uplift, climate change and atmospheric circulation through time. They are also influenced by the location and orientation of mountain ranges in relation to air circulation patterns, and how species diversification, dispersal and refugia respond to climate change. A better understanding of biosphere–lithosphere interactions is needed to understand the patterns and evolution of mountain biodiversity across space and time.

A reliable projection of precipitation over the Tibetan Plateau (TP) is crucial for climate adaptation activities in this climate‐sensitive region, but existing studies show a large spread in magnitude. Based on Coupled Model Intercomparison Project Phase 6 models, we investigate the TP summer precipitation projection and understand the sources of uncertainty. The results show that the TP exhibits a profound wetting trend throughout the 21st century, with precipitation increasing by 0.64 ± 0.06 mm day−1 during 2050–2099 under the SSP5–8.5 scenario. The moisture budget analysis indicates that the thermodynamical response to global warming determines the precipitation increase. However, both the thermodynamical and dynamical components contribute to the uncertainty of precipitation projection. The inter‐model spread of the thermodynamic term arises from divergent global mean warming, which is closely related to model climate sensitivity. The uncertainty of the dynamic component is driven by model‐dependent circulation changes induced by different equatorial Pacific warming rates. Plain Language Summary The precipitation over the Tibetan Plateau (TP) is crucial for local and downstream ecosystems, influencing millions of people. An accurate projection of future precipitation change is a prerequisite for climate change adaptation activities. Current existing studies show a large spread in the future changes of precipitation over the TP, but the reasons remain inconclusive. Here, we unravel the diversity of climate models in the precipitation projection over the TP by quantifying the contributions of the thermodynamical process related to global warming and the dynamical process related to atmospheric circulation change. While the enhancement of precipitation in the multi‐model ensemble mean is dominated by the thermodynamical response, both the thermodynamical and dynamical components are found to be responsible for the uncertainty of precipitation projection. The thermodynamical uncertainty is due to divergent global mean warming, which is closely associated with climate sensitivity, implying that models projecting a warmer climate also tend to project a stronger thermodynamical change. The uncertainty of the dynamic component is driven by air circulation changes induced by the equatorial Pacific warming pattern, which further affects the water vapor transport to the TP. Key Points Future projection of the Tibetan Plateau (TP) summer precipitation exhibits a large inter‐model spread in the magnitude of moistening trend The uncertainty of precipitation projection arises from both the thermodynamical and dynamical process The thermodynamical uncertainty is related to climate sensitivity, while the dynamical spread is driven by the equatorial Pacific warming

Background: Since the dawn of cities, the built environment has both affected infectious disease transmission and evolved in response to infectious diseases. COVID-19 illustrates both dynamics. The pandemic presented an opportunity to implement health promotion and disease prevention strategies in numerous elements of the built environment. Objectives: This commentary aims to identify features of the built environment that affect the risk of COVID-19 as well as to identify elements of the pandemic response with implications for the built environment (and, therefore, for long-term public health). Discussion: Built environment risk factors for COVID-19 transmission include crowding, poverty, and racism (as they manifest in housing and neighborhood features), poor indoor air circulation, and ambient air pollution. Potential long-term implications of COVID-19 for the built environment include changes in building design, increased teleworking, reconfigured streets, changing modes of travel, provision of parks and green-space, and population shifts out of urban centers. Although it is too early to predict with confidence which of these responses may persist, identifying and monitoring them can help health professionals, architects, urban planners, and decision makers, as well as members of the public, optimize healthy built environments during and after recovery from the pandemic.

With the rapid advance in urbanization, land use and anthropogenic heat (AH) dictated by human activities significantly modify the urban climate and in turn the air quality. Focusing on the Yangtze River Delta (YRD) region, a highly urbanized coastal area with severe ozone (O3) pollution, we estimate the impacts of land use and AH on meteorology and O3 using the Weather Research and Forecasting model coupled to Chemistry (WRF-Chem). These results enhance our understanding of the formation of O3 pollution in rapidly developing city clusters with place-specific topography, as most of our results can be supported by previous studies conducted in other regions around the world. Regional O3 pollution episodes occurred frequently (∼ 26 times per year) in the YRD from 2015 to 2019. These O3 pollution episodes are usually in calm conditions characterized by high temperature (over 20 ∘C), low relative humidity (less than 80 %), light wind (less than 3 m s−1) and shallow cloud cover (less than 5 okta). In this case, O3 pollution belts tend to appear in the converging airflows associated with the sea and the lake breezes. On the other hand, rapid urbanization has significantly changed land use and AH in this region, which subsequently affects meteorology and O3 concentration. The largest change in land use comes from urban expansion, which causes an increase in 2 m temperature (T2) by a maximum of 3 ∘C, an increase in planetary boundary layer height (PBLH) by a maximum of 500 m, a decrease in 10 m wind speed (WS10) by a maximum of 1.5 m s−1 and an increase in surface O3 by a maximum of 20 µg m−3. With regard to the sea and lake breezes, the expansion of coastal cities, like Shanghai, can enhance the sea breeze circulation by ∼ 1 m s−1. During the advance of the sea breeze front inland, the updraft induced by the front causes strong vertical mixing of O3. However, once the sea breeze is fully developed in the afternoon (∼ 17:00 LT), further progression inland will stall. Then O3 removal by the low sea breeze will be weakened, and surface O3 can be 10 µg m−3 higher in the case with cities than in the case with no cities. The expansion of lakeside cities, such as Wuxi and Suzhou, can extend the lifetime of lake breezes from noon to afternoon. Since the offshore flow of the lake breeze transports high O3 from the land to the lake, the onshore flow brings high O3 back to the land. Surface O3 in lakeside cities can increase by as much as 30 µg m−3. Compared to land use, the effects of AH are relatively small. The changes mainly appear in and around cities where AH fluxes are large. There are increases in T2, PBLH, WS10 and surface O3 when AH fluxes are taken into account, with increments of approximately 0.2 ∘C, 75 m, 0.3 m s−1 and 4 µg m−3, respectively. AH contributes largely to the urban environment, altering meteorological factors, O3 concentration and urban breeze circulation, but its effect on the sea and the lake breezes seems to be limited.

Changes in land cover and aerosols resulting from urbanization may impact convective clouds and precipitation. Here we investigate how Houston urbanization can modify sea-breeze-induced convective cloud and precipitation through the urban land effect and anthropogenic aerosol effect. The simulations are carried out with the Chemistry version of the Weather Research and Forecasting model (WRF-Chem), which is coupled with spectral-bin microphysics (SBM) and the multilayer urban model with a building energy model (BEM-BEP). We find that Houston urbanization (the joint effect of both urban land and anthropogenic aerosols) notably enhances storm intensity (by ∼ 75 % in maximum vertical velocity) and precipitation intensity (up to 45 %), with the anthropogenic aerosol effect more significant than the urban land effect. Urban land effect modifies convective evolution: speed up the transition from the warm cloud to mixed-phase cloud, thus initiating surface rain earlier but slowing down the convective cell dissipation, all of which result from urban heating-induced stronger sea-breeze circulation. The anthropogenic aerosol effect becomes evident after the cloud evolves into the mixed-phase cloud, accelerating the development of storm from the mixed-phase cloud to deep cloud by ∼ 40 min. Through aerosol–cloud interaction (ACI), aerosols boost convective intensity and precipitation mainly by activating numerous ultrafine particles at the mixed-phase and deep cloud stages. This work shows the importance of considering both the urban land and anthropogenic aerosol effects for understanding urbanization effects on convective clouds and precipitation.