Snowmelt Research Articles

Climate-Driven Changes in Annual Flow Patterns: A Comprehensive Analysis of the Buktyrma River (Kazakhstan)

This article examines and calculates the annual flows of rivers in the Buktyrma River basin in connection with changing climatic conditions affecting runoff formation. An analysis of climatic characteristics, based on data from meteorological stations of the hydrometeorological service of Kazakhstan, indicates intense warming and a moderate increase in annual precipitation since the early 1980s. The more intense melting of high-mountain snow and glaciers has led to a reduction in glaciated areas. Alongside the noted trend of increasing precipitation, this melting contributes to an increase in surface runoff. According to Global Land Ice Measurements from Space data, there has been a reduction in the area of glaciers in the river basin and a complete disappearance of glaciers in the Sarymsakty River basin. Studying long-term water-flow data in the basin has helped identify periods with consistent patterns. These periods are characterized by different values of probability-distribution-curve parameters. An assessment of the homogeneity of the identified periods of runoff series over the past decades, using known parametric criteria, confirmed the reliability of the calculated values of annual runoff. The observed increase in the norm, depending on elevation, glacier presence, and the spatial orientation of watershed ridges, ranges from 5% to 52%. The observed trends in changes in climatic characteristics and runoff indicators of the rivers in the basin support water-management planning in this region. This includes using the approximation of empirical river-supply curves, which can aid in assessing the calculated hydrological characteristics.

Coping with unpredictable environments: fine-tune foraging microhabitat use in relation to prey availability in an alpine species.

Microhabitat utilisation holds a pivotal role in shaping a species' ecological dynamics and stands as a crucial concern for effective conservation strategies. Despite its critical importance, microhabitat use has frequently been addressed as static, centering on microhabitat preference. Yet, a dynamic microhabitat use that allows individuals to adjust to fine-scale spatio-temporal prey fluctuations, becomes imperative for species thriving in challenging environments. High-elevation ecosystems, marked by brief growing seasons and distinct abiotic processes like snowmelt, winds, and solar radiation, feature an ephemeral distribution of key resources. To better understand species' strategies in coping with these rapidly changing environments, we delved into the foraging behaviour of the white-winged snowfinch Montifringilla nivalis, an emblematic high-elevation passerine. Through studying microhabitat preferences during breeding while assessing invertebrate prey availability, we unveiled a highly flexible microhabitat use process. Notably, snowfinches exhibited specific microhabitat preferences, favoring grass and melting snow margins, while also responding to local invertebrate availability. This behaviour was particularly evident in snow-associated microhabitats and less pronounced amid tall grass. Moreover, our investigation underscored snowfinches' fidelity to foraging sites, with over half located within 10m of previous spots. This consistent useprevailed in snow-associated microhabitats and high-prey-density zones. These findingsprovide the first evidence of dynamic microhabitat use in high-elevation ecosystems and offer further insights into the crucial role of microhabitats for climate-sensitive species. They call for multi-faceted conservation strategies that go beyond identifying and protecting optimal thermal buffering areas in the face of global warming to also encompass locations hosting high invertebrate densities.

Dynamic Snow Melting Process and Its Driving Factors in Northern Grasslands

Hourly automatic snow depth stations have enhanced insights into the dynamics and spatial variability of daily snowmelt. From 2021 to 2022, we gathered hourly snow depth measurements from six Hulun Buir grassland stations. Our analysis shed light on the dynamics of snowmelt and the key drivers in this northern region. We found that in northern China’s mid-high latitude grasslands, winter snow cover persists for about 80 to 134 days. The transition to the melting phase in early March spans 5 to 12 days, with continuous and rapid phases. Snow under 3 cm quickly collapses. If the average temperature from 10:00 to 18:00 exceeds 0 °C, complete melting occurs within 36 h. Daily snow melting sees initial stability, swift decline, and gradual reduction, peaking between 11:00 and 14:00. Finally, thermal conditions primarily drive snow melt dynamics, with 14:00 ground temperature being pivotal. These findings shed light on snow dynamics and key factors in the mid-high latitude grasslands of northern China.

South and Southeast Asia controls black carbon characteristics of Meili Snow Mountains in southeast Tibetan Plateau

South and Southeast Asia (SSA) emitted black carbon (BC) exerts potential effects on glacier and snow melting and regional climate change in the Tibetan Plateau. In this study, online BC measurements were conducted for 1 year at a remote village located at the terminus of the Mingyong Glacier below the Meili Snow Mountains. The Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) was used to investigate the contribution and potential effect of SSA-emitted BC. In addition, variations in the light absorption characteristics of BC and brown carbon (BrC) were examined. The results indicated that the annual mean concentration of BC was 415 ± 372 ngm−3, with the highest concentration observed in April (monthly mean: 930 ± 484 ngm−3). BC exhibited a similar diurnal variation throughout the year, with two peaks observed in the morning (from 8:00 to 9:00 AM) and in the afternoon (from 4:00 to 5:00 PM), with even lower values at nighttime. At a short wavelength of 370 nm, the absorption coefficient (babs) reached its maximum value, and the majority of babs values were < 20 Mm−1, indicating that the atmosphere was not overloaded with BC. At the same wavelength, BrC substantially contributed to babs, with an annual mean of 25.2 % ± 12.8 %. SSA was the largest contributor of BC (annual mean: 51.1 %) in the study area, particularly in spring (65.6 %). However, its contributions reached 20.2 % in summer, indicating non-negligible emissions from activities in other regions. In the atmosphere, the SSA BC-induced radiative forcing (RF) over the study region was positive. While at the near surface, the RF exhibited a significant seasonal variation, with the larger RF values occurring in winter and spring. Overall, our findings highlight the importance of controlling BC emissions from SSA to protect the Tibetan Plateau against pollution-related glacier and snow cover melting.

Study on the effect of self-melting snow materials on the properties of asphalt mixture

Adding self-melting snow material to asphalt pavement can improve driving safety in winter weather. Self-melting materials can melt the snow on the road surface, without too much negative impact on asphalt pavement. Two commonly used self-melting snow materials are particle type and powder type. Through indoor experiments, the effects of two self-melting snow materials on the high-temperature performance, low-temperature performance, water stability, and anti-stripping performance of asphalt mixtures are compared. The experiment shows that these self-melting snow materials have little effect on the high-temperature and low-temperature performance of the asphalt mixture, and the low-temperature performance of the mixture decreased after freeze-thaw environment. After freeze-thaw cycle or immersion, the snow melt components in the mixture gradually precipitate, leading to the water stability and anti-spalling performance.

Characteristics of glacier ice melt runoff in three sub-basins in Urumqi River basin, eastern Tien Shan

Study regionThe Urumqi River basin located in eastern Tien Shan in Central Aisa Study focusGlacier runoff plays a pivotal role in water resources and stabilizing streamflow in mountainous regions. To assess the characteristics of glacier ice melt runoff in sub-basins within a single basin, three sub-basins with glacier ratios varying from 4% to 46% in the Urumqi River basin are investigated. Through the simulation by HBV light model on the basis of the observed meteorological and hydrological data. The characteristics and behaviour of glacier ice melt runoff in the three sub-basins are analysed. New hydrological insights for the regionIt was found that both the contribution ratios of ice melt runoff and glacier runoff increase linearly with the increasing glacier ratio for the three catchments, rather than logarithmically or exponentially as observed in previous studies. This is due to the relatively high contributions of ice melt and glacier runoff to river flow in a catchment characterized by high elevation and extensive glacier coverage (Catchment 1), resulting from the coincidence of summer precipitation maxima with snow and ice melt in this region. The coefficient of variations (CV) of river flow tends to decrease with the decreasing glacier ratio in sub-basins in the Urumqi River basin, indicating that river flow becomes more stable as it flows farther from the headwater in the Urumqi River basin. The lowest glacierized Catchment 3 exhibited the minimum CV value, demonstrating a stable outflow.

Enabling Advanced Snow Physics Within Land Surface Models Through an Interoperable Model‐Physics Coupling Framework

AbstractAccurate estimation of snow accumulation and melt is a critical part of decision‐making in snow‐dominated watersheds. In this study, we demonstrate a flexible methodology to couple a detailed snow model, Crocus, separately to two different land surface models (LSMs), Noah‐MP and Noah. The original LSMs and the coupled models (Noah‐MP‐Crocus and Noah‐Crocus) are used to simulate snow depth, snow water equivalent, and other water and energy states and fluxes. The results of simulations are compared against a wide range of independent gridded and point scale reference data sets. Our results show that coupling the detailed snow model, Crocus, with the LSMs improves the snow depth and snow water equivalent relative to independent observations. Overall, larger improvements are obtained with coupling Crocus to the Noah LSM, with the coupled Noah‐Crocus configuration reducing the RMSE and bias of snow depth from 2% to 12% and 57% to 75%, respectively, relative to Snow Data Assimilation System (SNODAS) and snow product from the University of Arizona. On the other hand, smaller improvements are obtained by coupling Crocus with Noah‐MP. The Coupled Noah‐MP‐Crocus reduces the snow depth bias but slightly degrades the RMSE of snow depth and snow water equivalent. The corresponding impacts in other water budget terms such as evapotranspiration, soil moisture, and streamflow, however, are mixed, pointing to the significant need to improve the coupling assumptions of these processes within land models. Overall, the interoperable coupling framework demonstrated here offers the opportunity to include more detailed snow physics and processes, and to advance data assimilation systems through improved exploitation of information from snow remote sensing instruments.

Hydrological regimes and evaporative flux partitioning at the climatic ends of high mountain Asia

Abstract High elevation headwater catchments are complex hydrological systems that seasonally buffer water and release it in the form of snow and ice melt, modulating downstream runoff regimes and water availability. In High Mountain Asia (HMA), where a wide range of climates from semi-arid to monsoonal exist, the importance of the cryospheric contributions to the water budget varies with the amount and seasonal distribution of precipitation. Losses due to evapotranspiration and sublimation are to date largely unquantified components of the water budget in such catchments, although they can be comparable in magnitude to glacier melt contributions to streamflow. Here, we simulate the hydrology of three high elevation headwater catchments in distinct climates in HMA over 10 years using an ecohydrological model geared towards high-mountain areas including snow and glaciers, forced with reanalysis data. Our results show that evapotranspiration and sublimation together are most important at the semi-arid site, Kyzylsu, on the northernmost slopes of the Pamir mountain range. Here, the evaporative loss amounts to 28% of the water throughput, which we define as the total water added to, or removed from the water balance within a year. In comparison, evaporative losses are 19% at the Central Himalayan site Langtang and 13% at the wettest site, 24 K, on the Southeastern Tibetan Plateau. At the three sites, respectively, sublimation removes 15%, 13% and 6% of snowfall, while evapotranspiration removes the equivalent of 76%, 28% and 19% of rainfall. In absolute terms, and across a comparable elevation range, the highest ET flux is 413 mm yr−1 at 24 K, while the highest sublimation flux is 91 mm yr−1 at Kyzylsu. During warm and dry years, glacier melt was found to only partially compensate for the annual supply deficit.

Mammal-bearing Pleistocene deposits, Vranić, southwestern Pannonian Basin System

Vranić site is a sand quarry that is located on the southern foothills of Papuk Mountain. From bottom to top of the succession, three sedimentary units have been recognized as: Unit 1 containing massive sand with scattered gravel-sized clasts, marl cobbles and boulders, and abundant marine mammal and fish fossils; Unit 2 consisting of sand intercalated with silt, clay and gravel, which may be horizontally bedded; and Unit 3, which is an erosionally-based lenticular matrix to clast-supported structureless gravel. The basal part of Unit 1 shows numerous reworked skeletal remains of Miocene marine mammals. Cosmogenic radionuclides constrain the age of burial of Unit 1 to 895 ± 211 ka, while the source area of Unit 1 had a quick denudation.The massive sands deposited on the slopes of Papuk Mountain were vulnerable to erosion due to the absence of clay. Heavy rainfall or water from snow melting created flash floods that infiltrated the sands, thereby causing slope destabilization and deformation. This process led to slumps that were transformed into a sandy debris flow. This sediment was probably deposited during the interglacial marine isotope age (MIS) 21 period when the scarce vegetation and a warmer climate favored the melting of permafrost ice and consequently triggered slope movements during MIS 22. The reworked skeletal material sampled at the Vranić site comprises fossilized fish along with mammal bones and teeth. Thus, the Vranić site represents an important site for cetacean fossil remains and serves as an important data source for marine life in the Central Paratethys.

Variations of the Oxygen Isotopic Composition of the Yauza River within the City of Moscow in 2019–2021 under the Effect of Snow Melting and Heavy Rains

Variations of the Oxygen Isotopic Composition of the Yauza River within the City of Moscow in 2019–2021 under the Effect of Snow Melting and Heavy Rains

The image of the taiga in the ballads of Leonid Zaval’nyuk

The article is devoted to the study of the ballad genre in the lyrics of the poet Leonid Zaval’nyuk (1930-2010). The study focuses on the analysis of “The Taiga Ballad” and “The Ballad of Melting Snow,” which were included in the collection “Beyond the Receding Horizon” (1956). These ballads open and end the ballad cycle, consisting of five works. The plot of both ballads develops in the artistic space of the taiga, which becomes a place of moral testing for the heroes. Leonid Zaval’nyuk was the first to introduce the image of the taiga into the ballad. The decanonisation of the ballad genre occurs in the 19th century. Leonid Zaval’nyuk’s works not only preserve ballad traditions (third-person narration, appeal to archetypal plots, mixing Christian and pagan beliefs, personification of natural forces, the special role of the season and time of day in the development of the plot), but also the evolution of the genre takes place (refusal of the mystical component, increasing the realism of the narrative, first-person narration). The decanonisation of the ballad genre occurs in the 19th century. Leonid Zaval’nyuk turned to the ballad genre throughout his entire career. The motif of moral testing became one of the leading ones for the poet.

Modification and Validation of the Soil–Snow Module in the INM RAS Climate Model

This paper describes the modification of a simple land snow cover module of the INM RAS climate model. The possible liquid water and refreezing of meltwater in the snow layer are taken into account by the proposed parameterization. This is particularly important for modelling the transition season, as this phenomenon is mainly observed during the formation and melting of the snow cover when the surface temperature fluctuates around 0 °C. The snow density evolution simulation is also added. This parameterization is implemented in the INM-CM snow module and verified on observation data using the ESM-SnowMIP-like protocol. As a result, the INM-CM mean climate snow melt periods are refined, particularly in middle and high latitudes. The snow-covered area according to the model is also improved. In the future, a modified version of the land snow module can be used, coupled with a snow albedo model that takes into account snow metamorphism. This module can also be applied to sea ice snow.

Discrete element analysis of heating transfer characteristics of airport pavements by using electro thermal method for snow melting and deicing

This study presents a discrete element investigation on the internal temperature change characteristic and heat transfer efficiency in airport concrete pavement by using the carbon fiber electrothermal method for snow melting and deicing. A discrete element model for snow melting and deicing of airport concrete pavement by using the carbon fiber electrothermal method was generated. The temperature evolution on the surface of the pavement was captured and compared with the indoor experimental results. The numerical simulation results were in good agreement with the experimental results, which verified the applicability of the numerical model. On this basis, the effects of the heating temperature and heating paths on the internal heat conduction and temperature field distribution were investigated. The results showed that the temperature of the pavement surface and the temperature rise gradient are linearly related to the temperature of the carbon fiber heating wire. The initial heating time has little influence on the temperature rise path of the road surface layer after stopping heating and reheating. The temperature of the road surface layer rises slowly after the heating is stopped, and then decreases linearly at a rate of 0.4 °C/h not corresponding to the initial heating time.

Relative contribution from different water sources to supraglacial runoff in western Himalaya

Conservative tracers are often used in mixing models to estimate the contribution from different end-members to proglacial streams. The supraglacial runoff generated below the equilibrium line represents a combination of snow and ice melt, and rainfall, since additional mixing from englacial and subglacial drainage is not possible. Thus, supraglacial runoff offers a reliable proxy for the seasonal variations in end-member contribution to glacier-fed streams.In this study, we used stable water isotopes (δ18O, δD and d-excess) to estimate the seasonal variations in end-member contributions to the supraglacial runoff with a novel mixing model. During the early, mid, and late summer 2016, we collected and analysed the supraglacial runoff and its potential water sources: rain, ice, and snow. Accounting for fractionation processes occurring from solid to liquid phases, we calculated the isotopic signatures of the snowmelt and the ice melt. Based on our models, the supraglacial runoff was mainly composed of snowmelt (68.1 ± 7.9 %), followed by rainwater (16.6 ± 6.4 %) and ice melt (15.3 ± 6.1 %). Our results partially agree with those from a numerical glacio-hydrological based model estimates on the outflow of the same glacier. We discuss the slight discrepancies of the two modelling frameworks, and attribute them to the hydrological relevance of the subglacial aquifer system.

Perennial snow and ice cover change from 2001 to 2021 in the Hindu-Kush Himalayan region derived from the Landsat analysis-ready data

The changing climate directly affects spatial and temporal patterns of snow and ice cover globally and in the Hindu-Kush Himalayan (HKH) region. In the HKH, around 3.3 billion people across 11 countries depend on water originating from mountain glaciers and snowfields, and melting snow cover has a direct impact on their livelihood and well-being. Various studies have shown that the snow and ice cover in the HKH is declining at an alarming rate but have been limited in geographic, spatial and temporal scales. Here, we employed the Global Land Analysis and Discovery analysis ready Landsat time-series data (GLAD ARD) to map changes in perennial snow and ice between 2001 and 2021 at five-year epochs using decision tree ensemble models. These maps were used to create a stratified sampling design for reference data collection to estimate area and map accuracy. All five-year epoch maps have user's accuracies above 90% and producer's accuracies above 91%. Our sample data analysis showed that one-eighth of the extent of perennial snow and ice in the HKH, totalling 15,770 km2 (CI ± 3195 km2), disappeared over the last two decades with 105,935 km2 (CI ± 3396 km2) remaining in 2021. From map-based estimates, the largest decline of perennial snow and ice cover among the mountain ranges was found in the Himalayas with an estimated reduction of 5741 km2. Among HKH countries, China had the largest area of perennial snow and ice reduction of 10,654 km2, Nepal had the highest net perennial snow and ice reduction rate (31%). Among the river basins, the maximum net loss of perennial snow and ice cover between 2001 and 2021 was in the Indus (24.8%), followed by Brahmaputra (18.3%), and Tarim (15.7%). Our results confirm wide-spread loss of perennial snow and ice across the HKH region and provide both regionally consistent maps with derived area estimates at landform, national and basin-levels and methodology to continue monitoring snow and ice melt.

Mapping proglacial headwater streams in High Mountain Asia using PlanetScope imagery

Headwater streams transport nutrients, sediment, and mineral-rich groundwater downstream. In High Mountain Asia (HMA), headwater streams also funnel glacier and snow melt to sustain continuous water supply for the downstream region. These channels remain poorly mapped because of their inaccessibility and because they are smaller than the resolution of Landsat (30 m) and Sentinel-2 (10 m). In this study, we assessed the ability of 3 m resolution PlanetScope imagery to detect the proglacial headwaters downstream of all high-altitude glaciers larger than 5 km2 in HMA. We created 3000 manually labeled image tiles to train and evaluate computer vision (CV) against techniques common in the hydrologic remote sensing literature, specifically normalized difference water index (NDWI) thresholding and random forests (RF). Results indicate that CV best detects the headwater streams with >0.60 F1-scores, nearly 0.20 points higher than RF and 0.45 points higher than thresholding. We also assessed how errors in CV propagate to derived hydrologic information, exemplified by the biogeochemically critical measurement of stream surface area. We found that CV classifications produced surface areas with 0.98 R2, 0.01 km2 MAE, and 0.02 km2 RMSE against manually labeled surface areas. We also observed the best CV performance during the spring season with 30% more skillful classification performance than in summer and fall. Our results prove the ability of PlanetScope imagery to detect and map headwater streams accurately and at scale, and that classification errors stemming from the imagery or the CV methods do not greatly impair our ability to quantify stream surface area meaningful for biogeochemical exchange and hydrology studies.

Managed aquifer recharge as a strategy to redistribute excess surface flow to baseflow in snowmelt hydrologic regimes

Water management in snowmelt hydrologic regimes, characterized by large annual fluctuations in stream flow driven by seasonal snow melt, faces the challenge of highly variable supply that often does not align with timing of demand. Climate change may exacerbate management challenges by significantly reducing snowpack or shifting snow melt earlier. Here, managed aquifer recharge (MAR) is evaluated as a potential strategy to reallocate excess early-season stream flow to time periods when less surface water is available. This strategy differs from traditional MAR, where the goal is to minimize loss to surface water. We assess how to site MAR operations such that groundwater recharge flows back to the surface water system in a lagged manor to benefit water management objectives, which we term “enhanced baseflow.” We use a regional groundwater model for the Treasure Valley aquifer located in southwestern Idaho, United States to demonstrate a generalizable approach using regional groundwater models as tools to identify favorable baseflow enhancement locations. Hypothetical MAR is simulated at 197 candidate locations, which are then evaluated for how effectively they meet potential management objectives. In addition to demonstrating the modeling and evaluation approach, we discuss lessons learned from applying a pre-existing regional groundwater model to MAR for enhanced baseflow and also describe important considerations, such as the physical and institutional availability of surface flows and specific management objectives, when assessing regional and site-specific suitability of MAR for enhanced baseflow as a potential management strategy.

Analysis and Improvement of the Application of Playground Sports Posture Detection Technology in Physical Education Teaching and Training

INTORDUCTION: The goal of human posture detection technology applied in the field of sports is to realise the indexing of sports norms, to provide scientific guidance for training and teaching, which is of great significance to improve the quality of sports.OBJECITVES: Aiming at the problems of incomplete features, low accuracy and low real-time performance of sports posture detection and recognition methods.METHODS: In this paper, a method of sports pose detection based on snow melting heuristic optimisation algorithm of deep limit learning machine network is proposed. Firstly, by analyzing the process of motion pose detection, extracting the feature coordinates of Blaze-Pose and Blaze-Hands key nodes, and constructing the motion pose detection recognition system; then, optimizing the parameters of the deep extreme learning machine network through the snow-melt optimization algorithm, and constructing the motion pose detection recognition model; finally, through simulation experiments and analysis, the accuracy of the proposed method's motion pose detection recognition can reach 95% and the recognition time is less than 0.01 s.RESULTS: The results show that the proposed method improves the recognition accuracy precision, robustness and real-time performance.CONCLUSION: The problem of poor generalisation, low accuracy and insufficient real-time performance of the recognition application of the motion pose detection and recognition method is solved.

Genetic mechanism of geothermal water in the sandstone reservoir of western Sichuan, SW China: Evidence from hydrochemistry and δD − δ18O isotopes

Geothermal energy is the vital clean and renewable energy in the world. In China, most of high−temperature sedimentary − type geothermal waters are developed in western Sichuan, such as geothermal springs in the Litang county. In this study, hydrochemistry and δD − δ18O isotopes were investigated to clarify the genetic mechanism of high−temperature sedimentary − type geothermal waters in the Litang county. The self-organized map and Piper diagram showed three hydrochemical types of geothermal waters: (1) HCO3 − SO4 − Na, (2) HCO3 − Na with low Cl− concentration, (3) HCO3 − Na with high Cl− concentration. Cluster 1 geothermal water of Na − HCO3 − SO4 was dominated by dissolution of silicate and sulfate minerals. Cluster 2 geothermal water of HCO3 − Na with low Cl− concentration was affected by dissolution of silicate and CO2 degassing and mixed by large amounts of shallow cold water. Cluster 3 geothermal water of HCO3 − Na with high Cl− concentration was affected by dissolution of sandstone silicate and CO2 degassing and mixed by less shallow cold water. The recharge elevation of geothermal water in Litang ranges from 4799 to 4972 m, with an average of 4915 m. This suggests that the recharge sources of geothermal water are snow melt water and magmatic water. Cluster 3 geothermal water displayed the largest contribution of magmatic water. The temperature of HCO3 − SO4 − Na geothermal water after mixing is 92−102 °C, with an average of 97 °C; the initial temperature of HCO3 − Na with low Cl− geothermal water is 60−72 °C, with an average of 65 °C; the initial temperature of HCO3 − Na with high Cl− geothermal water is 74−91 °C, with an average of 81 °C. The temperature of geothermal water after mixing is Class 1 > Class 3 > Class 2. From the perspective of reservoir temperature, the Class 3 of geothermal water had the highest values, followed by Class 1 and Class 2 of geothermal water. From the perspective of cold − water mixing ratio, Class 2 and Class 3 of geothermal water had a similar mixing ratio, slightly higher than that of Class 1 of geothermal water. Therefore, the class 3 geothermal water with HCO3 − Na with high Cl− concentration possess the great potential for exploitation.

Raindrop Size Distributions Simulated Using a Bin Microphysics Scheme: Different Biases in Stratiform and Convective Rain From an Extratropical Cyclone

AbstractBin microphysics schemes prognose the raindrop size distribution (RSD), which can be directly evaluated through comparison with disdrometer observations. This evaluation will provide implications on the reliability of simulated cloud microphysics by bin microphysics schemes. In this study, the RSDs of a precipitation event associated with an extratropical cyclone passing South Korea are simulated using a bin microphysics scheme and compared with those observed by a ground‐based disdrometer. The simulated mean RSD overall agrees with the observation. However, notable overestimations appear in the large‐ (3.3–4.3 mm) and small‐ (0.56–1.88 mm) diameter ranges, which respectively stem from the biases in two different time periods, one dominated by stratiform rain and the other largely involved with convective rain. In the stratiform‐rain‐dominated period, the melting of snow is the largest contributor to RSDs. The overestimation in the large‐diameter range in this period can be associated with overly active ice–ice collection at upper levels, which generates a local maximum in RSD at the diameter of 3.3 mm that is not seen in the observed RSDs. In the convective‐rain‐involved period, the warm‐rain collision–coalescence is the largest contributor to RSDs. The overestimation in the small‐diameter range and underestimation in the large‐diameter range imply that the collisional growth of raindrops is represented to be weaker than that in reality. The findings in this study suggest that the RSDs simulated using a bin microphysics scheme can have some systematic biases associated with misrepresentation of some microphysical processes.