Simulation of Snowstorm over the Yellow Sea Using a Mesoscale Coupled Model (original) (raw)
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2018
A sea-effect snowfall accumulated a national record-breaking snowdrift of 73 cm in Merikarvia, on the west coast of Finland, in less than one day on 8 January 2016. A good understanding of such heavy sea-effect snowfalls in the present climate is essential if we want to assess the probability of their occurrence and intensity in the future. Since very few in situ observations were made of the Merikarvia snowfall event in the sea area where the convection cells developed, we investigated the case with an ERA5 reanalysis, the Global Navigation Satellite System (GNSS), and the numerical weather prediction model HARMONIE, using weather radar information as a reference. We aimed to study the feasibility of the reanalysis and GNSS methods for investigating the basic characteristics of the snowband. In addition, we examined whether the assimilation of observed radar reflectivities could improve the HARMONIE simulations. In addition to snowfall patterns, the vertical structure of the atmosp...
A Numerical Modeling Study of Mesoscale Cyclogenesis to the East of the Korean Peninsula
Monthly Weather Review, 1998
Numerical simulations and the analysis of observational data are employed to understand the mesoscale cyclogenesis in a polar airstream that occurred over the sea to the east of the Korean peninsula on 28-29 January 1995. The observational analysis shows that a mesoscale low develops over the southeastern East Sea (Japan Sea) on 29 January 1995. Satellite imagery also indicates that a meso--scale vortex forms on the lee side of the northern Korean mountain complex (KMC), which is located in the northern Korean peninsula, and that a meso-␣-scale cyclone develops over the southeastern East Sea at a later time. The mesoscale cyclone forms in the lower troposphere with strong baroclinicity and cyclonic circulation under the influence of an upper-level synoptic-scale cold vortex.
The major research advances of mesoscale weather dynamics in China since 2003
Advances in Atmospheric Sciences, 2007
This paper reviews the main theoretical progress of mesoscale weather dynamics since 2003, including: (1) The dynamic mechanisms of balanced and unbalanced flow are applied to study the genesis and development problems of mesoscale circulation. The symmetric instability and transverse-wave instability are analyzed in line and vortex atmosphere convection, and further research has been done on nonlinear convective symmetric instability. The interaction between forced convection and unstable convection and the wave characteristics of mesoscale motion are also discussed. (2) Intermediate atmosphere dynamic boundary layer models are developed. The complicated nonlinear interaction is analyzed theoretically between the atmospheric boundary layer and the free atmosphere. The structure of the topography boundary layer, atmospheric frontogenesis, the structure and circulation of the low-level front and other boundary layer dynamic problems are discussed. (3) The formation and development of meso-β-scale rainstorms under the background of the East-Asia atmosphere circulation are diagnosed with the variation of MPV (moist potential vorticity) anomalies. And some physical vectors are modified and applied in the moist atmosphere.
THE MAJOR ADVANCES IN MESOSCALE ATMOSPHERIC DYNAMIC RESEARCH OF CHINA SINCE 2003
2006
This paper reviews the main theoretical progress of mesoscale weather dynamics since 2003, including: (1) The dynamic mechanisms of balanced and unbalanced flow are applied to study the genesis and development problems of mesoscale circulation. The symmetric instability and transverse-wave instability are analyzed in line and vortex atmosphere convection, and further research has been done on nonlinear convective symmetric instability. The interaction between forced convection and unstable convection and the wave characteristics of mesoscale motion are also discussed. (2) Intermediate atmosphere dynamic boundary layer models are developed. The complicated nonlinear interaction is analyzed theoretically between the atmospheric boundary layer and the free atmosphere. The structure of the topography boundary layer, atmospheric frontogenesis, the structure and circulation of the low-level front and other boundary layer dynamic problems are discussed. (3) The formation and development of meso-β-scale rainstorms under the background of the East-Asia atmosphere circulation are diagnosed with the variation of MPV (moist potential vorticity) anomalies. And some physical vectors are modified and applied in the moist atmosphere.
Combined Effects of Blocking and AO on a Prolonged Snowstorm in Jeju Island
An analysis of the snowstorm that occurred during January 23-25, 2016 in Jeju Island is presented. This event was considered part of the snowfall pattern that rarely occurs at Jeju Island due to the mild marine climate. In terms of diabatic heating, there are two factors encompassing convection and large-scale condensation. One heating factor was the convective instability due to cold advection at the upper level that was 1.7 times stronger than the continuous cold advection at the lower level. The other heating factor was the latent heat emitted by cloud developed by the instability. In the context of large-scale environment, the result of vertical temperature differential was due to the transition to the strong negative Arctic Oscillation (AO) in January 2016. Under the negative AO phase, blocking tilted to the southeast, compared to normal, occurred in the upper layers. Simultaneously, a trough with a core temperature of −45°C was rapidly induced over the Korean Peninsula. In this study, the snowstorm occurred with a sea surface temperature 1-2 K higher than normal over the Yellow Sea, and cold advection to lower layers was persistent. Therefore, the snowstorm has not been resolved through consideration of the local instability. A maximum of 12 cm of fresh snow cover was recorded during this snowstorm, which persisted for 3 days due to the impact on its large-scale environment, which generated a strong vertical cold advection differential through the occurrence blocking during January 19-24, 2016, under the strong negative AO phase.
Terrestrial, Atmospheric and Oceanic Sciences, 2014
We examined the sensitivity of simulated snowfall to prescribed sea surface temperature (SST) data using the Weather Research and Forecasting (WRF) model and the Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) SST dataset for the Korean Peninsula. The OSTIA data were initially compared with in situ buoy measurements from three coastal sites in the Yellow Sea and was shown to be in good agreement with the in situ data with root mean square errors of 0.14-0.17 K for the daily mean values. Next, we conducted several WRF simulations, including a baseline simulation with the OSTIA data and sensitivity simulations with a temporally and spatially varying SST. The simulations were run for the Yellow Sea during December 2012 when a severe snowfall occurred in Korea. The baseline model generally captured the observed spatial and temporal variations of snowfall, surface air temperature and surface pressure in Korea. The sensitivity simulations with an increased and decreased SST resulted in a variation of +0.8/-0.7 K for the surface air temperature, ±0.6 hPa for the surface pressure, and ±0.3 m s-1 for the surface wind speed, in relation to the baseline simulation. The SST deviation affected the precipitation variability with changes of ±9% for snowfall and ±18% for rainfall, indicating considerable model sensitivity to SST perturbations. The change in the meteorological variables of the upper layer induced by the SST perturbations showed a symmetrical structure with respect to warmer and colder SST. Nevertheless, ice represented a nonlinear combination of the results at the low and mid-levels.
Intense sea-effect snowfall case on the western coast of Finland
Advances in Science and Research, 2017
A new national daily snowfall record was measured in Finland on 8 January 2016 when it snowed 73 cm (31 mm as liquid water) in less than a day in Merikarvia on the western coast of Finland. The area of the most intense snowfall was very small, which is common in convective precipitation. In this work we used hourly weather radar images to identify the sea-effect snowfall case and to qualitatively estimate the performance of HARMONIE, a non-hydrostatic convection-permitting weather prediction model, in simulating the spatial and temporal evolution of the snowbands. The model simulation, including data assimilation, was run at 2.5 km horizontal resolution and 65 levels in vertical. HARMONIE was found to capture the overall sea-effect snowfall situation quite well, as both the timing and the location of the most intense snowstorm were properly simulated. Based on our preliminary analysis, the snowband case was triggered by atmospheric instability above the mostly ice-free sea and a low-level convergence zone almost perpendicular to the coastline. The simulated convective available potential energy (CAPE) reached a value of 87 J kg −1 near the site of the observed snowfall record.
Mesoscale Band Formation in Three Major Northeastern United States Snowstorms
Weather and Forecasting, 1999
The National Centers for Environmental Prediction's 29-km version Meso Eta Model and Weather Surveillance Radar-1988 Doppler base reflectivity data were used to diagnose intense mesoscale snowbands in three northeastern United States snowstorms. Snowfall rates within these snowbands were extreme and, in one case, were close to 15 cm (6 in.) per hour. The heaviest total snowfall with each snowstorm was largely associated with the positioning of these mesoscale snowbands. Each snowstorm exhibited strong midlevel frontogenesis in conjunction with a deep layer of negative equivalent potential vorticity (EPV). The frontogenesis and negative EPV were found in the deformation zone, north of the developing midlevel cyclone. Cross-sectional analyses (oriented perpendicular to the isotherms) indicated that the mesoscale snowbands formed in close correlation to the intense midlevel frontogenesis and deep layer of negative EPV. It was found that the EPV was significantly reduced on the warm side of the midlevel frontogenetic region as midlevel dry air, associated with a midlevel dry tongue jet, overlaid a low-level moisture-laden easterly jet, north of each low-level cyclone. The continual reduction of EPV on the warm side of the frontogenetic region is postulated to have created the deep layer of negative EPV in the warm advection zone of each cyclone. The negative EPV was mainly associated with conditional symmetric instability (CSI). Each case exhibited a much smaller region of conditional instability (CI) on the warm side of the frontogenesis maximum for a short period of time. The CSI and, to a lesser extent, CI are postulated to have been released as air parcels ascended the moist isentropes, north of the warm front, upon reaching saturation. This likely was a major factor in the mesoscale band formation and heavy snowfall with each snowstorm. The results indicate that model frontogenesis and EPV fields can be used to predict the potential development of mesoscale snowbands. When a deep layer of negative EPV and strong midlevel frontogenesis are forecast by the models, forecasters can anticipate the regions where mesoscale snowbands may form. Inspection of saturation equivalent potential temperature in conjunction with EPV is suggested to determine whether CI is present in a negative EPV region. If CI is present in addition to CSI, then upright convection may dominate over slantwise convection leading to heavier snowfall rates. The region where the frontogenesis and negative EPV are forecast to persist the longest (usually left of the 700-hPa low track) is where the heaviest storm total snowfall will occur. Once mesoscale bands are detected on radar, accurate short-term forecasts of areas that will receive heavy snowfall can be made.
Intercomparison of oceanic and atmospheric forced and coupled mesoscale simulations
Annales Geophysicae, 1999
A mesoscale non-hydrostatic atmospheric model has been coupled with a mesoscale oceanic model. The case study is a four-day simulation of a strong storm event observed during the SEMAPHORE experiment over a 500´500 km 2 domain. This domain encompasses a thermohaline front associated with the Azores current. In order to analyze the eect of mesoscale coupling, three simulations are compared: the ®rst one with the atmospheric model forced by realistic sea surface temperature analyses; the second one with the ocean model forced by atmospheric ®elds, derived from weather forecast re-analyses; the third one with the models being coupled. For these three simulations the surface¯uxes were computed with the same bulk parametrization. All three simulations succeed well in representing the main oceanic or atmospheric features observed during the storm. Comparison of surface ®elds with in situ observations reveals that the winds of the ®ne mesh atmospheric model are more realistic than those of the weather forecast re-analyses. The low-level winds simulated with the atmospheric model in the forced and coupled simulations are appreciably stronger than the re-analyzed winds. They also generate stronger uxes. The coupled simulation has the strongest surface heat¯uxes: the dierence in the net heat budget with the oceanic forced simulation reaches on average 50 Wm A2 over the simulation period. Sea surface-temperature cooling is too weak in both simulations, but is improved in the coupled run and matches better the cooling observed with drifters. The spatial distributions of sea surface-temperature cooling and surface¯uxes are strongly inhomogeneous over the simulation domain. The amplitude of the¯ux variation is maximum in the coupled run. Moreover the weak correlation between the cooling and heat¯ux patterns indicates that the surface¯uxes are not responsible for the whole cooling and suggests that the response of the ocean mixed layer to the atmosphere is highly non-local and enhanced in the coupled simulation.
Atmosphere
This study aimed to determine the atmospheric conditions in which sea-effect snow (SES) and non-SES events occurred in a meso-scale structure. All snow events between 2009 and 2018 were found by examining the aviation reports at two international airports in Istanbul, Turkey. Then, threshold values and threshold intervals were presented for SES and non-SES events on the basis of many meteorological parameters (e.g., air temperature, dew point, relative humidity, heat fluxes, sea surface temperature (SST)). In addition, an algorithm was created for operational prediction of SES events at both airports. The most important parameter that distinguished SES events from NON-SES events was the temperature difference between sea surface (SS) and upper-atmosphere air parcel. Accordingly, sensible and latent heat fluxes had similarly higher values in SES events on average. Although the wind directions were mostly northerly in both event types, low wind shear in the layer between the SS and su...