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A negative shortwave cloud feedback associated with higher extratropical liquid water content in mixedphase clouds is a common feature of global warming simulations, and multiple mechanisms have been hypothesized. A set of process-level experiments performed with an idealized global climate model (a dynamical core with passive water and cloud tracers and full Rotstayn—Klein single-moment microphysics) show that the common picture of the liquid water path (LWP) feedback in mixed-phase clouds being controlled by the amount of ice susceptible to phase change is not robust. Dynamic condensate processes—rather than static phase partitioning—directly change with warming, with varied impacts on liquid and ice amounts. Here, three principal mechanisms are responsible for the LWP response, namely higher adiabatic cloud water content, weaker liquid-to-ice conversion through the Bergeron—Findeisen process, and faster melting of ice and snow to rain. Only melting is accompanied by a substantial loss of ice, while the adiabatic cloud water content increase gives rise to a net increase in ice water path (IWP) such that total cloud water also increases without an accompanying decrease in precipitation efficiency. Perturbed parameter experiments with a wide range of climatological LWP and IWP demonstrate a strong dependence of the LWP feedback on the climatological LWP and independence from the climatological IWP and supercooled liquid fraction. This idealized setup allows for a clean isolation of mechanisms and paints a more nuanced picture of the extratropical mixed-phase cloud water feedback than simple phase change.

The chemical composition of cloud water can be used to infer the sources of particles upon which cloud droplets and ice crystals have formed. In order to obtain cloud water for analysis of chemical composition for elevated clouds in the pristine high Arctic, balloon-borne active cloud water sampling systems are the optimal approach. However, such systems have not been feasible to deploy previously due to their weight and the challenging environmental conditions. We have taken advantage of recent developments in battery technology to develop a miniaturised cloud water sampler for balloon-borne collection of cloud water. Our sampler is a bulk sampler with a cloud drop cutoff diameter of approximately 8 µm and an estimated collection efficiency of 70%. The sampler was heated to prevent excessive ice accumulation and was able to operate for several hours under the extreme conditions encountered in the high Arctic. We have tested and deployed the new sampler on a tethered balloon during the Microbiology-Ocean-Cloud-Coupling in the High Arctic (MOCCHA) campaign in August and September 2018 close to the North pole. The sampler was able to successfully retrieve cloud water samples that were analysed to determine their chemical composition as well as their ice-nucleating activity. Given the pristine conditions found in the high Arctic we have placed significant emphasis on the development of a suitable cleaning procedure to minimise background contamination by the sampler itself.

In order to explore the possible impact of topography on precipitation between the eastern and western sides of the Liupan Mountains (LMs) in the northwest region of China, the differences in distribution characteristics of total column water vapor (TCWV), total column cloud water (TCCW), and total precipitation (TP) were studied by using the 40-year hourly data of the fifth generation reanalysis (ERA5) from the European Centre for Medium-Range Weather Forecasts (ECMWF). The results showed the following: (1) The TCCW and TP on the eastern and western sides of the LMs decrease gradually from south to north, following a southwestward bias along the latitude. The high values of the TCCW and TP are predominantly concentrated in the period from July to September. The greatest difference between the two sides occurs in September, with the eastern side exhibiting 15% and 18% higher values compared to the western side, respectively. (2) Both the TCCW and TP exhibit distinct diurnal distribution patterns. The high values on the eastern side persist for a longer duration throughout the day compared to the western side, and they occur in more consecutive months. There is a certain correlation between the steepness of the eastern slope and the gentle gradient of the western slope. Additionally, the occurrence of these high values in the afternoon is earlier on the eastern side compared to the western side. (3) The monthly mean TP is significantly linearly correlated with the TCWV and TCCW, with slightly higher coefficients for the western side compared to the eastern side. This relationship is closely related to the topography of the mountain range. The regression equation provides a quantitative tool for predicting the monthly mean TP in the LM region and serves as a reference basis for the development of cloud water resources in the area.

The evaluation of cloud distribution, properties, and their interaction with the radiation (longwave and shortwave) is of utmost importance for the proper assessment of future climate. Therefore, this study focuses on the Coupled Model Inter-Comparison Project Phase-6 (CMIP6) historical and future projections using the Shared Socio-Economic Pathways (SSPs) low- (ssp1–2.6), moderate- (ssp2–4.5), and high-emission (ssp5–8.5) scenarios along the South Asian region. For this purpose, a multi-model ensemble mean approach is employed to analyze the future projections in the low-, mid-, and high-emission scenarios. The cloud water content and cloud ice content in the CMIP6 models show an increase in upper and lower troposphere simultaneously in future projections as compared to ERA5 and historical projections. The longwave and shortwave cloud radiative effects at the top of the atmosphere are examined, as they offer a global perspective on radiation changes that influence atmospheric circulation and climate variability. The longwave cloud radiative effect (44.14 W/m2) and the shortwave cloud radiative effect (−73.43 W/m2) likely indicate an increase in cloud albedo. Similarly, there is an expansion of Hadley circulation (intensified subsidence) towards poleward, indicating the shifting of subtropical high-pressure zones, which can influence regional monsoon dynamics and cloud distributions. The impact of future projections on the tropospheric temperature (200–600 hPa) is studied, which seems to become more concentrated along the Tibetan Plateau in the moderate- and high-emission scenarios. This increase in the tropospheric temperature at 200–600 hPa reduces atmospheric stability, allowing stronger convection. Hence, the strengthening of convective activities may be favorable in future climate conditions. Thus, the correct representation of the model physics, cloud-radiative feedback, and the large-scale circulation that drives the Indian Summer Monsoon (ISM) is of critical importance in Coupled General Circulation Models (GCMs).

Weather and climate models are challenged by uncertainties and biases in simulating Southern Ocean (SO) radiative fluxes that trace to a poor understanding of cloud, aerosol, precipitation, and radiative processes, and their interactions. Projects between 2016 and 2018 used in situ probes, radar, lidar, and other instruments to make comprehensive measurements of thermodynamics, surface radiation, cloud, precipitation, aerosol, cloud condensation nuclei (CCN), and ice nucleating particles over the SO cold waters, and in ubiquitous liquid and mixed-phase clouds common to this pristine environment. Data including soundings were collected from the NSF–NCAR G-V aircraft flying north–south gradients south of Tasmania, at Macquarie Island, and on the R/V Investigator and RSV Aurora Australis. Synergistically these data characterize boundary layer and free troposphere environmental properties, and represent the most comprehensive data of this type available south of the oceanic polar front, in the cold sector of SO cyclones, and across seasons. Results show largely pristine environments with numerous small and few large aerosols above cloud, suggesting new particle formation and limited long-range transport from continents, high variability in CCN and cloud droplet concentrations, and ubiquitous supercooled water in thin, multilayered clouds, often with small-scale generating cells near cloud top. These observations demonstrate how cloud properties depend on aerosols while highlighting the importance of dynamics and turbulence that likely drive heterogeneity of cloud phase. Satellite retrievals confirmed low clouds were responsible for radiation biases. The combination of models and observations is examining how aerosols and meteorology couple to control SO water and energy budgets.

This paper presents a method for cloud water path retrieval from daytime MSU-GS measurements onboard the Russian hydrometeorological satellite Arktika-M 1. The technique is based on the physical principles of the interaction of electromagnetic radiation with cloud particles at wavelengths of 0.55 and 4.0 μm. Cloud water path estimates obtained from the MSU-GS radiometer are compared with similar estimates from the AMSU/MHS and AHI radiometer data. Based on the results of the comparison, the required estimates of the cloud water path of drop clouds are within the permissible limits of the measurement error, not exceeding 50 g/m 2 . At the same time, due to its design features, the MSU-GS radiometer does not allow retrieving the cloud water path of ice clouds with the required accuracy. On average, the cloud water path estimate of ice clouds according to the MSU-GS data is underestimated by 110 g/m 2 , and the root-mean-square error is 158 g/m 2 , when compared to the AHI radiometer data. The estimates of the cloud water path are introduced into the geographic information system Arktika-M, which provides access to the Arktika-M 1 data and the results of their thematic processing in a near real time mode.

Based on a cloud water resources (CWR) diagnostic dataset with a 1° × 1° resolution over China from 2000 to 2019, this study systematically analyzes the spatiotemporal patterns of CWR in the complex terrain of the North China Region. The results indicate the following: (1) CWR-related physical quantities exhibit significant seasonal differences, with most being highest in summer and lowest in winter; water vapor convergence is strongest in summer and weakest in autumn, while hydrometeor convergence is smallest in summer and largest in winter; and the water surplus (precipitation minus evaporation) is minimal and negative in spring, indicating severe spring drought. (2) At the annual scale, precipitation is highly correlated with cloud condensation (r > 0.99), and CWR variation is primarily controlled by hydrometeor influx (r > 0.99). (3) The regional annual CWR and precipitation increase at rates of 34.8 mm/10 years and 49.2 mm/10 years, respectively, but exhibit seasonal asynchrony—CWR increases in all four seasons, while precipitation shows a slight decreasing trend in winter. (4) Spatially, CWR show a pattern of “more in the south and north, less in the central region; more in the east, less in the west,” with significant increases in the central–southern parts (southern Shanxi and Hebei, Beijing, and Tianjin). (5) Empirical orthogonal function (EOF) analysis reveals two dominant modes of CWR anomalies: a “region-wide consistent pattern” and a “north–south out-of-phase dipole pattern,” the latter being related to terrain-induced differences in water vapor transport and uplift condensation. The results statistically elucidate the distribution patterns of CWR under the influence of complex topography in NCR, providing a scientific reference for the development and utilization of regional CWR.

Satellite observations are used to deduce the relationship between cloud water and precipitation water for low-latitude shallow marine clouds. The specific sensors that facilitate the analysis are the collocatedCloudSatprofiling radar and the Moderate Resolution Imaging Spectroradiometer (MODIS). The separation of the cloud water and precipitation water signals relies on the relative insensitivity of MODIS to the presence of precipitation water in conjunction with estimates of the path-integrated attenuation of theCloudSatradar beam while explicitly accounting for the effect of precipitation water on the observed MODIS optical depth. Variations in the precipitation water path are shown to be associated with both the cloud water path and the cloud effective radius, suggesting both macrophysical and microphysical controls on the production of precipitation water. The method outlined here is used to place broad bounds on the mean relationship between the precipitation water path and the cloud water path in shallow marine clouds, given certain clearly stated assumptions. The ratio of precipitation water to cloud water is shown to increase from zero at low cloud water path values to roughly 0.5 at 500 g m−2of cloud water. The retrieval results further show that the median influence of precipitation on the observed optical depth increases monotonically with optical depth varying between 1% and 5% at 500 g m−2of cloud water with the source of the uncertainty deriving from the assumption of the nature of the precipitation drop size distribution.

Observations from a series of frontal and postfrontal storms during the Colorado Airborne Multiphase Cloud Study (CAMPS) are combined to show transitions in cloud dynamics and microphysical statistics over a mountain range. During 10 flights in 2010 and 2011, along-wind, across-ridge transects over the Colorado Park Range are performed to statistically characterize air motion and microphysical conditions and their variability. Composite transect statistics show median vertical winds to be mostly upward windward of the ridge axis, and that cloud water concentration (CWC) and ice-particle number concentration are greatest near the ridge. Mixed-phase clouds were found throughout the study area, but increase in frequency by 70% relative to other cloud types in the vicinity of the range. Compared to ice-only clouds, mixed-phase clouds are associated with greater near-ridge increases in CWC and preferentially occur in regions with greater vertical wind variability or updrafts. Strong leeside reductions in CWC, the abundance of mixed-phase clouds, and number concentration of ice particles reflect the dominance of precipitation and particle mass loss processes, rather than cloud growth processes, downwind from the topographic barrier. On days in which the air column stability does not support lee subsidence, this spatial configuration is markedly different, with both ice- and liquid-water-bearing clouds appearing near the ridgeline and extending downwind. A case study from 9 January 2011 highlights mixed-phase regions in trapped lee waves, and in a near-ridgetop layer with evidence of low-altitude ice particle growth.

Cloud water is an important geophysical quantity that connects the hydrological and radiation characteristics of climate systems and plays an essential role in the global circulation of the atmosphere, water, and energy. However, compared to the contribution of water vapor to precipitation, the understanding of cloud-precipitation transformation and its climate feedback mechanism remains limited. Based on precipitation and temperature datasets of the National Meteorological Observatory and MODIS (Moderate Resolution Imaging Spectroradiometer) satellite remote sensing products, the evolution characteristics of cloud water resources in China over the last twenty years of the 21st century were evaluated. Significant decreasing trends of −3.3 and −4.89 g/m2 decade−1 were found for both the liquid and ice water path. In humid areas with high precipitation, the cloud water path decreased fast. In semiarid areas with an annual precipitation ranging from 500–800 mm, the decreasing trend of the cloud water path was the lowest. The cloud-water period was calculated to represent the relative changes in clouds and precipitation. The national average cloud-water period in China is approximately 12.4 h, with obvious seasonal changes. Over the last 20 years, the cloud water path in dry regions decreased more slowly than that in wet regions, and the cloud-precipitation efficiency significantly increased, which narrowed the climate difference between the dry and wet regions. Finally, the mechanism of the cloud-water period evolution in the different regions were examined from the perspectives of the dynamic and thermal contributions, respectively. Due to the overall low upward moisture flux (UMF) in the dry region, the response of the cloud-water period to the lower tropospheric stability (LTS) mainly first increased and then decreased, which was the opposite in the wet region. The increase in cloud-precipitation efficiency in the dry region of Northwest China is accompanied by a continuous decrease in LTS. The different configurations of regional UMF and LTS play a crucial role in the evolution of cloud-precipitation, which can be used as a diagnostic basis to predict changes in the precipitation intensity to a certain extent.