Search Results (5)

Multilayer clouds, comprising vertically stacked cloud layers with distinct microphysical characteristics, constitute a critical yet complex atmospheric phenomenon influencing regional to global climate patterns. Advances in observational techniques, particularly the application of high-resolution humidity vertical profiling via radiosondes, have significantly enhanced multilayer cloud detection capabilities. Multilayer clouds are widely distributed around the world, showing significant regional differences. Many studies have been carried out on the formation mechanism of multilayer clouds, and observational evidence indicates a close relationship between multilayer cloud development and water vapor supply, updraft, atmospheric circulation, as well as wind shear; however, a unified and comprehensive theoretical framework has not yet been constructed to fully explain the underlying mechanism. In addition, the unique vertical structure of multilayer clouds exhibits different climate effects when compared with single-layer clouds, affecting global climate patterns by regulating precipitation processes and radiative energy budgets. This article reviews the research progress related to multilayer cloud observations and their climate effects and looks forward to the research that needs to be carried out in the future. Full article

Heavy rainfall not only affects urban infrastructure, it also impacts environmental changes, and which then influence the sustainability of development and ecology. Therefore, researching and forecasting heavy rainfall to prevent disaster-related damages is essential. A high-resolution numerical simulation was carried out for a heavy rainfall case in Zhengzhou, Henan Province, China, from 19–20 July 2021. The analysis of weather conditions revealed that the main cause of heavy rainfall in Zhengzhou was the supersaturation and condensation of water vapor, resulting from the invasion of dry and cold air from the upper and middle atmospheric layers. This weather condition is ideally suited for applying generalized potential temperature that is informed by the non-uniform saturation theory. Based on this, the new scheme revised the cloud microphysical scheme of the cloud water condensation parameterization process by substituting generalized potential temperature. The characteristics of the mesoscale environment and water condensates were comparatively analyzed between the original and the new scheme. Then, the quantitative mass budget and latent heat budget related to microphysical conversions were comparatively calculated over Zhengzhou. Furthermore, the possible two-scheme mechanisms through which the cloud microphysics processes affected the rainfall were investigated and discussed. It was found that: (1) The new scheme, which takes into account generalized potential temperature, produced precipitation fields more in line with observations and simulated stronger hourly precipitation compared to the original scheme. (2) The conversions of snow were the main source of microphysical processes that produced precipitation and released latent heat due to the dry and cold air invasion. (3) Given that the condensation of water vapor was hypothesized to occur at 70% relative humidity (RH) or above, rather than the original 100% RH, the new scheme simulated more supercooled water and ice-phase particles than the original scheme. This enhancement, in turn, intensified convective development owing to positive feedback within the cloud microphysics processes and cloud environment, ultimately leading to the simulation of more intense hourly precipitation. Full article

The water vapor-related microphysical processes (WVRMPs) in cloud microphysics schemes are crucial to the formation and dissipation of clouds, which have a significant impact on the quantitative precipitation forecasting of numerical weather prediction models. In this study, a well physics-based parallel-split transition approach (PSTA) to compute the WVRMPs from the same temperature and humidity state is developed and compared with the original sequential-update transition approach (SUTA) in a double-moment cloud microphysics scheme. Case study and batch experiments were carried out to investigate their different impacts on the clouds and precipitation simulated by the Global/Regional Assimilation and Prediction System (GRAPES) regional 3 km high-resolution model of the China Meteorological Administration (CMA), named CMA-MESO. The results show that the PSTA experiment tends to simulate a narrower and more concentrated precipitation area with a higher-intensity center compared to those of the SUTA experiment, which is more consistent with the observations. In the cold region, the net transition rates of WVRMPs from the PSTA experiment with more ice-phase hydrometeors are higher than those from the SUTA experiment. While in the warm region, the condensation and evaporation rates with violent fluctuation simulated by the SUTA are significantly larger than those from the PSTA experiment, resulting in less precipitation. The batch experiments indicate that the equitable threat scores (ETSs) of 24-h precipitation simulated by the PSTA are just slightly better than those of the SUTA, yet its ETSs of 48-h precipitation have been systematically improved for all magnitude levels against the SUTA. It is demonstrated that more attention should be paid to the reasonable treatments of the WVRMPs in developing cloud microphysics schemes. Full article

Using the Weather Research and Forecasting model with chemistry module (WRF-Chem), Typhoon Nida (2016) was simulated to investigate the effects of anthropogenic gaseous emissions on the vortex system. Based on the Multi-resolution Emission Inventory for China (MEIC), three certain experiments were conducted: one with base-level emission intensity (CTRL), one with one-tenth the emission of ${\mathrm{SO}}_2$ (SO2_C), and one with one-tenth the emission of ${\mathrm{NH}}_3$ (NH3_C). Results show that the simulations reasonably reproduced the typhoon’s track and intensity, which were slightly sensitive to the anthropogenic gaseous emissions. When the typhoon was located over the ocean, a prolonged duration of raindrop growth and more precipitation occurred in CTRL run. The strongest updraft in CTRL is attributed to the maximum latent heating through water vapor condensation. During the landfalling period, larger (smaller) differential reflectivities in the main-core of the vortex were produced in NH3_C (SO2_C) run. Such opposite changes of raindrop size distributions may lead to stronger (weaker) rainfall intensity, and the ice-related microphysical processes and the relative humidity in low troposphere were two possible influential factors. Moreover, additional ten-member ensemble results in which white noise perturbations were added to the potential temperature field, indicated that the uncertainty of thermodynamic field in the current numerical model should not be ignored when exploring the impacts of aerosol on the microphysics and TC precipitation. Full article

This work presents a selective overview of natural fogs in terms of fog types, forms and states of occurrence, physical, micro-physical, chemical and dynamic properties, basic characterizing parameters, etc. In focus are related achievements and contributions reported mainly during the last decade and a half, as a result of both laboratory studies and field observations. Processes of homogeneous and heterogeneous nucleation are analyzed in the aspects of condensation, nuclei diversity and specifics, as related to the activation, growth and deposition of fog droplets. The effect is highlighted of the water vapor’s partial pressure on the surface tension of the liquid water–air interface and the freezing point of the water droplets. Some problems and aspects of fog modeling, parameterization, and forecasting are outlined and discussed on the examples of newly developed relevant 1D/3D theoretical models. Important issues of fog impacts on the air quality, ecosystems, water basins, societal life, and human health are also addressed and discussed, particularly in cases of anthropogenically modified (chemical, radioactive, etc.) fogs. In view of reducing the possible negative effects of fogs, conclusions are drawn concerning the new demands and challenges to fog characterization imposed by the changing natural and social environment and the needs for new data on and approaches to more adequate observations of fog-related events. Full article