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1.
It is well known that when the Siberian High expands to the western part of the East Sea (Japan Sea), the distribution of snowfall amount is mainly controlled by the topography. Therefore, the maximum area of the precipitation is typically located over the slopes and near the summit of the Taebaek Mountains (called Type A). However, sometimes there were snowfall maxima near the Yeongdong coastal area of Korea rather than the neighboring mountains (called Type B) for some events. Two heavy snowfall events of 20–21 January 2008 of Type A (named by Event A) and of 13 January 2008 of Type B (named by Event B) were selected to understand the differences in the locations of snowfall maxima in the Yeongdong region of Korea. To do so, we investigated the differences between the two events in the movement of the air parcels leading to the understanding of the heavy snowfall mechanism using 3-dimensional trajectory analyses which applied the Weather Research and Forecasting (WRF) high resolution output as 3-dimensional meteorological fields. In this study, an upward motion under the influence of the northeasterly wind was observed along the slope of the mountains during Event A. In contrast, there was a strong downward motion along the slope of the mountains under the influence of the northwesterly wind while the parcels were reaching Gangneung (GN, hereafter) during the snowfall period of Event B. Furthermore, during Event B, the convergence of the parcels different in potential temperature and mixing ratio, yielded a favorable condition for forming a coastal front (discontinuity zone) around the Yeongdong coastal area. This lead to heavy snowfall over GN in the coastal plain region rather than in Daegwallyeong (DG, hereafter) near the summit of the Taebaek Mountains, which differs from the snowfall distribution of Event A. 相似文献
2.
A 24-h simulation with the Advanced Regional Prediction System (ARPS) nonhydrostatic model is performed for the heavy snowfall event of 3–4 February 1998 along the eastern coast of Korean Peninsula; the results are used to understand the snowfall process, including why the precipitation maxima formed along the Yeongdong coastal region rather than over the mountain slope and ridge top during. The numerical simulation with a 4-km horizontal grid spacing and 43 levels reproduces very well the narrow snowband located off the eastern Korean coast, away from, instead of over, the Yeongdong coastal mountain range. The general evolution of the snowband agrees quite well with radar observations, while the water-equivalent precipitation amount agrees reasonably well with radar precipitation estimate. The simulation results clearly show that the snow band developed due to the lifting by a coastal front that developed because of the damming of cold air against the eastern slope of the coastal mountain range. The damming was enhanced by the advection of cold air by a low-level mountain-parallel jet from the north, formed due to geostrophic adjustment as the on-shore upslope air was decelerated by the mountain blocking. As the onshore flow weakened later due to synoptic-scale flow pattern change, the cold front propagated off shore and the precipitation dissipated. 相似文献
3.
Yoo-Jun Kim Byung-Gon Kim Jae-Kwan Shim Byoung-Choel Choi 《Asia-Pacific Journal of Atmospheric Sciences》2018,54(3):499-510
The Yeongdong region of the Korean Peninsula is vulnerable to high-impact weather events, because of its complicated geographical characteristics and East Sea effect, such that heavy snowfall episodes have frequently occurred in winter. Snow crystal play an important role in cloud and precipitation physics because it is an essential element for improvement of numerical model, and remote sensing retrieval such as radar and satellite. In this study, the high-temporal resolution (3-hourly) dataset of radiosonde soundings and snow particle photographs during the intensive observation period for 2013–2016 has been used to understand characteristics of snow particles for the different meteorological conditions in the Yeongdong region. We also attempt to simulate two episodes that occurred on 23–24 February and 13–14 December 2016; one has a single-layered cloud and the other has two-layered cloud structure. This study demonstrates that the rimed particles in the first period tend to shift to aggregates of dendrites with the decrease of 850-hPa temperature. In general, the low-level clouds in the Yeongdong region are observed along with the distinctive wind shear and strong inversion in equivalent potential temperature around 2 ~ 3 km above the sea level. The simulation successfully represents the variations of the characteristics of snow particles as well as different cloud structure for both episodes. The observation and model simulations clearly suggest that snow particles primarily depend on the 850-hPa temperature. 相似文献
4.
A coupled mesoscale atmospheric-land surface model is used to simulate a twelve-day heavy precipitation event in California. In addition to the temporal variation of the large-scale flow, local topography played a crucial role in the simulated precipitation and land-surface snow budget through orographically-generated vertical motion and a decrease of atmospheric temperature with increasing altitude. The observed and simulated heavy precipitation occurred at locations where orographic lifting is strong: western slopes of the Sierra Nevada Mountains and the Coastal Range. Due to rainshadow effects, the Central Valley area, which is located at the lee side of the Coastal Range, received only a small amount of precipitation. The snowline appeared at altitudes as low as 750 m above sea level, and most of the precipitation above the 1.8 km level was snow. Maximum rainfall was located near the 1 km elevation along the western slope of the Sierra-Nevada while snowfall maxima appeared along the ridge of the Sierra Nevada Mountains. Snow accumulation was also strongly dependent upon surface elevations. The simulation suggested that over 75% of the fresh snowfall during the study period was added to the existing snow cover at elevations above 1.5 km while much of the snowfall over lower elevations melted. 相似文献
5.
利用激光雨滴谱仪资料、地面观测资料、合肥双偏振雷达资料和欧洲中心ERA5再分析资料，对2022年1月26日发生在江淮之间一次短时强降雪天气过程中滴谱变化和雷达回波特征进行分析，并探讨雨雪相态变化的成因，结果表明：（1）本次江淮之间突发的强降雪过程中，雨雪转换迅速，降水相态变化时间提前于地面温度变化，合肥地区温度变化明显强于周边地区。（2）此次短时强降雪发生在锋生强迫过程形成的高架雷暴中，强烈的上升运动、降水粒子的融化和蒸发引起温度负变化，导致降温过程自上而下产生，表现为地面温度下降落后于雨雪相态的变化。（3）降雪过程先后出现降雨、雨夹雪、纯雪3个阶段，雨（雪）滴谱的时间演变特征变化明显；转雪后降水粒子的下落末速度降低、粒径增大、滴谱明显变宽。（4）雷达观测显示此次降雪回波顶高度较高，超过6.5km，低空1km有强度超过50dBZ强反射率因子带并延伸到地面。反射率因子、相关系数（CC）和降水粒子产品（HCL）在降雪过程的发展中有明显特征。 相似文献
6.
Hyoung-Gu Nam Byung-Gon Kim Sang-Ok Han Chulkyu Lee Seoung-Soo Lee 《Asia-Pacific Journal of Atmospheric Sciences》2014,50(4):541-552
Characteristics of snowfall episodes have been investigated for the past ten years in order to study its association with lowlevel stability and air-sea temperature difference over the East Sea. In general, the selected snowfall episodes have similar synoptic setting such as the Siberian High extended to northern Japan along with the Low passing by the southern Korean Peninsula, eventually resulting in the easterly flow in the Yeongdong region. Especially in the heavy snowfall episodes, convective unstable layers have been identified over the East sea due to relatively warm sea surface temperature (SST) about 8～10°C and specifically cold pool around 1～2 km above the surface level (ASL), which can be derived from Regional Data Assimilation and Prediction System (RDAPS), but that have not been clearly exhibited in the weak snowfall episodes. The basic mechanism to initiate snowfall around Yeongdong seems to be similar to that of lake-effect snowstorms around Great Lakes in the United States (Kristovich et al., 2003). Difference of equivalent potential temperature (θ e ) between 850 hPa and surface as well as difference between air and sea temperatures altogether gradually began to increase in the pre-snowfall period and reached their maximum values in the course of the period, whose air (850 hPa) — sea temperature difference and snowfall intensity in case of the heavy snowfall episodes are almost larger than 20°C and 6 tims greater than the weak snowfall episodes, respectively. Interestingly, snowfall appeared to begin in case of an air-sea temperature difference exceeding over 15°C. The current analysis is overall consistent with the previous finding (Lee et al., 2012) that an instabilityinduced moisture supply to the lower atmosphere from the East sea, being cooled and saturated in the lower layer, so to speak, East Sea-Effect Snowfall (SES), would make a low-level ice cloud which eventually moves inland by the easterly flow. In addition, a longlasting synoptic characteristics and convergence-induced invigoration also appear to play the important roles in the severe snowstorms. Improvements in our understanding of mesoscale sea-effect snowstorms require detailed in-situ and remote sensing observations over and around East Sea since observations of the concurrent thermodynamic and microphysical characteristics have not been available there and this study emphasizes the importance of low level stability as quantitative estimation of moist static energy generation over the East Sea. 相似文献
7.
Yoo-Jun KIM So-Ra IN Hae-Min KIM Jin-Hwa LEE Kyu Rang KIM Seungbum KIM Byung-Gon KIM 《大气科学进展》2021,38(3):413-429
This study investigates the characteristics of cold clouds and snowfall in both the Yeongdong coastal and mountainous regions under different meteorological conditions based on the integration of numerical modeling and three-hourly rawinsonde observations with snow crystal photographs for a snowfall event that occurred on 29?30 January 2016.We found that rimed particles predominantly observed turned into dendrite particles in the latter period of the episode when the 850 hPa temperature decreased at the coastal site,whereas the snow crystal habits at the mountainous site were largely needle or rimed needle.Rawinsonde soundings showed a well-defined,two-layered cloud structure along with distinctive wind-directional shear,and an inversion in the equivalent potential temperature above the low-level cloud layer.The first experiment with a decrease in lower-layer temperature showed that the low-level cloud thickness was reduced to less than 1.5 km,and the accumulated precipitation was decreased by 87%compared with the control experiment.The difference in precipitation amount between the single-layered experiment and control experiment(two-layered)was not so significant to attribute it to the effect of the seeder?feeder mechanism.The precipitation in the last experiment by weakening winddirectional shear was increased by 1.4 times greater than the control experiment specifically at the coastal site,with graupel particles accounting for the highest proportion(~62%).The current results would improve snowfall forecasts in complicated geographical environments such as Yeongdong in terms of snow crystal habit as well as snowfall amount in both time and space domains. 相似文献
8.
以NCEP资料为初始场和侧边界条件,利用WRF模式对东、西天山地形对2015年12月9—12日大暴雪影响进行敏感性试验,从降水强度和分布等方面对比分析模拟结果,探讨地形在暴雪过程中的作用,对成因进行初步研究分析,结果表明:(1)此次强降雪发生是高空西南急流抽吸、低层风切变及风速辐合、偏北风与地形强迫抬升、地面冷锋移动缓慢等共同造成的。(2)此次暴雪天气过程,地形对强降雪的落区、强度影响很大,东、西天山高度与强降雪强度正相关,东、西天山高度降低、强降雪落区沿环流方向移动。(3)地形动力强迫整体上增强次级环流圈。近地面上升速度中心出现在迎风坡山脚至山腰区域,并向两侧递减,与此次大暴雪中心落区以及乌鲁木齐附近测站降雪量分布吻合,东、西天山地形高度降低50%,近地面上升速度中心值减少30%。地形强迫东、西天山峡谷近地面生成辐合中心和辐合线,辐合中心强度与地形高度正相关。(4)地形强迫抬升有加强水汽辐合汇聚的作用,东、西天山地形高度降低50%,水汽通量与水汽通量散度减少30%。 相似文献
9.
The southwestern coast of the Caspian Sea often experiences heavy snowfall during winter season due to the lake effect. The accurate estimation of snowfall in this region is still a challenge for weather forecasters. This study attempts to investigate the simulation of lake-effect snow (LES) event occurring along the southwest coastline of the Caspian Sea from 31 January to 4 February 2014 using Weather Research and Forecasting (WRF) model. The study evaluates the sensitivity of four microphysics (WSM6, Goddard, Morrison, and Thompson) schemes and two planetary boundary layer (PBL) schemes (the Yonsei University (YSU) and the Mellor-Yamada-Janjic (MYJ)), yielding eight distinct combinations. The results indicated that all the simulations overestimated the precipitation. However, the best configurations for estimation of precipitation and snow in terms of their spatiotemporal variation were the Morrison-MYJ and the Goddard-MYJ, respectively. Analyses of the vertical profiles of hydrometeor species showed that the combination of Goddard and MYJ schemes created more snow and graupel than the other configurations. Although the combination of WSM-MYJ schemes revealed the least bias, it was not appropriate for the prediction of snow. A comparison of the two boundary layer schemes showed that the MYJ scheme simulated better intensity and distribution of precipitation than the YSU scheme compared to observations. Also, the maximum radar reflectivity of the model output was useful for identifying the location of maximum precipitation. 相似文献
10.
利用1961—2017年中国地面观测站日降水资料、全球大气多要素和海表温度月资料,分析华南区域持续性强降水过程的气候特征,诊断并比较与华南前汛期、后汛期区域持续性强降水年际变化相关的大气环流和海表温度异常特征。结果表明,3—12月华南都可能出现持续性强降水过程,其中汛期4—9月的占了94.4%。伴随着区域持续性强降水的年际变化,华南本地垂直上升运动显著异常是前汛期和后汛期的共同点,但前汛期、后汛期在华南及周边环流异常、水汽输送来源以及海温异常分布等方面都存在一定差异。在前汛期华南区域持续性强降水偏重年,赤道西太平洋区域海温偏低,由于大气罗斯贝波响应使西太平洋副热带高压偏强,热带西太平洋向华南区域水汽输送加强,从而有利于区域持续性强降水偏重。后汛期华南区域持续性强降水偏重年的海温异常分布是赤道中东太平洋区域正异常、东印度洋至西太平洋暖池区负异常,海温异常通过西北太平洋副热带高压、南海热带季风强度、水汽输送和垂直环流等多方面,导致后汛期区域持续性强降水偏重。 相似文献
11.
利用1961—2019年冬季北疆45个国家站逐日降水观测资料,采用统计分析方法,对不同等级降雪的气候变化特征进行了分析。结果表明:近59 a北疆降雪日数、降雪量、降雪强度分别以0.41 d/10 a、3.13 mm/10 a、0.15(mm·d~(-1))/10 a的速率增加,其中降雪量对全年降水量的贡献以1.3%/10 a的速率增长。降雪日数、降雪量主要表现为中雪和大雪的增加,降雪强度主要表现为暴雪强度的增加。小雪对降雪日数、降雪量的贡献呈减少趋势,其余等级为增加趋势,以中雪降雪日和大雪降雪量的贡献最为明显。北疆降雪日数仅在1月表现为减少趋势,主要是小雪日数显著减少;冬季各月降雪量均表现为增加趋势,主要是中雪和大雪降雪量显著增加。21世纪前10 a是降雪日数和降雪量最多的时期,20世纪60年代和21世纪10年代是降雪日数较少的时期。北疆降雪量在1985年发生突变,突变后年平均降雪量增加了12.4 mm。对比丰雪年和枯雪年,丰雪年降雪量偏多主要是小雪以上等级降雪日数的增多。 相似文献
12.
切比雪夫多项式在模式地形平滑中的应用研究 总被引：1，自引：0，他引：1
利用切比雪夫多项式展开滤波方法获得较为平滑的模式地形,并对2008年7月20～22日四川省一次大暴雨过程进行了数值模拟,通过地形敏感性试验讨论了地形对暴雨的影响作用以及平滑地形对GRAPES模式的适用性。结果表明,切比雪夫多项式展开滤波方案选取高阶截断项数,促使模式地形更为平滑,地形高度变化使得垂直速度发生变化,进而引起降水变化,上升运动强度增强(或减弱)引起该区域内雨强增强(或减弱)。2008年7月2～28日连续26天的试验表明,切比雪夫多项式展开滤波方案对GRAPES模式中的小雨和中雨预报有改善作用,对大雨和暴雨改善较小。总体来看,切比雪夫多项式在地形平滑中对降水预报有正的效果。 相似文献
13.
中国东部北方地区冬季降雪的时空特征及其与全球异常海温的联系 总被引：2，自引：0，他引：2
基于中国东部北方地区279个气象台站1961-2008年的观测资料,以及1°×1°的全球海表温度资料,运用主成分分析、小波分析、相关分析等方法探讨中国东部北方地区冬季降雪的时空特征及同期全球海温与其的相关性。研究发现：中国东部北方区域（以下简称研究区）冬季降雪量存在2-3a、7-8a的高频振荡周期,及一个准16a的年代际尺度的低频振荡周期。在1961-2008年间,研究区域冬季降雪量总体呈现上升趋势,特别是45°N以北的研究区北部区域冬季降雪量在48年问增加显著,而45°N以南的研究区南部区域冬季降雪量变化并不明显。分析发现,位于北大西洋上30°-50°N,10°-40°W海区的海温与研究区域降雪的第一、二特征向量均为显著的正相关,研究区北部冬季降雪量与海温关系密切,南部区域冬季降雪量与全球海温的相关性不明显,海温变暖可能是导致研究区北部降雪显著增加的重要因素。 相似文献
14.
基于1970—2019年内蒙古大兴安岭林区11个气象站逐日降水量和温度资料, 提取降雪数据, 采用趋势分析法、距平法、M-K突变法、滑动t检验法等, 分析了大兴安岭林区降雪的时空变化特征。结果表明: 大兴安岭林区总降雪量和各等级降雪量均呈增加趋势, 其中小雪和暴雪的降雪量增加趋势较小; 小雪和中雪量在21世纪00年代达到最大值, 大雪和暴雪量在21世纪10年代达到最大值; 各等级降雪量对总降水量的贡献率为小雪>中雪>大雪>暴雪; 各等级降雪量年内月变化均呈M型分布, 总降雪量高峰出现在11月; 总降雪量在1995年有显著突变, 小雪、中雪、大雪、暴雪降雪量无显著突变年份。空间上总降雪量和各等级降雪量(除暴雪外)大体呈北多南少、西多东少的变化趋势。大兴安岭林区降雪初始日呈延后趋势, 终止日呈提前趋势, 雪季长度呈每10 a缩短2.3 d的趋势。 相似文献
15.
利用常规观测资料、NCEP再分析资料、多普勒雷达资料等对2015年2月25日辽宁东南部一次强降雪过程进行分析。结果表明：此次强降雪过程发生在低空切变线东侧暖湿区对应高空急流出口区左侧的辐散区内,有强的水汽辐合中心;地面偏南气流受山前地形抬升作用在强降水区形成风向辐合和850 hPa以下急流中心,是造成强降雪的主要原因之一;暴雪过程开始前6 h出现温度平流随高度减小的配置,假相当位温空间分布上锋区的形成,有利于不稳定层结的建立;8～12 h前正涡度平流、中低层风向辐合带、近地面冷空气层的建立以及次级环流的形成加强了上升运动,对强降雪预报具有很好的指示作用;在降水相态是雨或雨夫雪时,雷达回波最大强度达到40～45 dBZ,而强降雪时回波强度为20～25 dBZ;当大连本站850 hPa温度以及1 000 hPa与850 hPa两层等压面之间的厚度处于雨雪转换临界值时,大连南部为雨或雨夹雪,北部为雪,此时出现强降雪,回波高度基本在6 km以下,最强回波25～35 dBZ维持在1 km以下,近地层为弱偏北风,与其上的西南风在边界层形成切变层,将暖湿气流抬升,为强降水提供动力条件。 相似文献
16.
利用常规观测、自动站逐时降水量、乌鲁木齐市风廓线雷达及ECMWF1°×1°再分析等资料,对2018年10月17—18日乌鲁木齐雨夹雪转大暴雪过程进行分析。结果表明,大暴雪是在低空西北气流与中高层西南急流叠加并维持的有利环流背景下,由700～850 hPa风切变、风速辐合、地面冷锋及地形强迫抬升等多尺度系统共同作用造成的。强降雪时雷达探测高度维持较高达7500 m,随着降雪结束探测高度明显降低。水平风场表明低空西北急流与中高层偏南急流形成的垂直风切变廓线的维持,是强降雪持续的动力条件。大气折射率结构常数C_n~2、垂直速度的大小与雨雪的开始、结束时间有较好的对应关系,且低层较强偏北风与C_n~2大值区相对应,降雪时低层垂直速度为0.8～1.2 m·s~(-1),雨或雨夹雪时垂直速度为1.8～2.5 m·s~(-1)。因此,水平风向风速、C_n~2和垂直速度的垂直变化对暴雪短临预报有很好的参考价值。 相似文献
17.
2020年1月5日07时至6日04时（北京时,下同）华北中部出现一次回流暴雪天气,过程最大降雪量15.5 mm。文中应用ERA5再分析和多种高分辨率观测资料分析了此次暴雪的大尺度天气背景和本地动、热力状况,探讨了暴雪落区、强度演变和降雪微物理特征及成因。结果表明,受河套地区地面倒槽和东北平原高压影响,900 hPa以下东北气流（被称为“回流”）自东北平原经渤海抵达华北平原,早于降雪7 h开始影响华北中部,受太行山阻挡在华北平原形成浅薄的近地面中尺度辐合线,对应暴雪落区;暴雪落区位于500 hPa高空槽前、700 hPa南北走向切变线东侧,850 hPa受西南低涡外围东南气流影响。降雪前1 h石家庄市观测到800 m以下转为东北风,1 km以下气温迅速下降至?5—?1℃,形成“冷垫”;暴雪区上空700 hPa附近低空急流较降雪早2 h出现,随后急流变厚、向下伸展至2 km高度,其下部暖湿空气沿“冷垫”爬升触发降雪,急流风速增至极值（19 m/s）和急流指数达峰值（约8）与大于1 mm/h强降雪时段重合,此时700 hPa上下为上升运动和水汽输送的大值中心。本次降雪粒子直径多为0.35—0.55 mm,降雪强度与粒子数浓度呈线性正相关;降雪云层位于1.3—5.5 km高度,大致以3 km （约?10℃）为分界线,下层为冰雪混合层,上层为冰雪层,冰雪层相对湿度与地面雪花粒子浓度及降雪强度呈正相关。基于雨滴谱仪探测资料反演的地面反射率因子与降雪强度拟合关系为Z=149.85R1.14。 相似文献
18.
Influence of SST biases on future climate change projections 总被引：1，自引：0，他引：1
We use a quantile-based bias correction technique and a multi-member ensemble of the atmospheric component of NCAR CCSM3 (CAM3) simulations to investigate the influence of sea surface temperature (SST) biases on future climate change projections. The simulations, which cover 1977?C1999 in the historical period and 2077?C2099 in the future (A1B) period, use the CCSM3-generated SSTs as prescribed boundary conditions. Bias correction is applied to the monthly time-series of SSTs so that the simulated changes in SST mean and variability are preserved. Our comparison of CAM3 simulations with and without SST correction shows that the SST biases affect the precipitation distribution in CAM3 over many regions by introducing errors in atmospheric moisture content and upper-level (lower-level) divergence (convergence). Also, bias correction leads to significantly different precipitation and surface temperature changes over many oceanic and terrestrial regions (predominantly in the tropics) in response to the future anthropogenic increases in greenhouse forcing. The differences in the precipitation response from SST bias correction occur both in the mean and the percent change, and are independent of the ocean?Catmosphere coupling. Many of these differences are comparable to or larger than the spread of future precipitation changes across the CMIP3 ensemble. Such biases can affect the simulated terrestrial feedbacks and thermohaline circulations in coupled climate model integrations through changes in the hydrological cycle and ocean salinity. Moreover, biases in CCSM3-generated SSTs are generally similar to the biases in CMIP3 ensemble mean SSTs, suggesting that other GCMs may display a similar sensitivity of projected climate change to SST errors. These results help to quantify the influence of climate model biases on the simulated climate change, and therefore should inform the effort to further develop approaches for reliable climate change projection. 相似文献
19.
The sensitivity of the Late Saalian (140?ka) and LGM (21?ka) Eurasian ice sheets to sea surface conditions 总被引：1，自引：1，他引：0
Florence Colleoni Johan Liakka Gerhard Krinner Martin Jakobsson Simona Masina Vincent Peyaud 《Climate Dynamics》2011,37(3-4):531-553
This work focuses on the Late Saalian (140?ka) Eurasian ice sheets?? surface mass balance (SMB) sensitivity to changes in sea surface temperatures (SST). An Atmospheric General Circulation Model (AGCM), forced with two preexisting Last Glacial Maximum (LGM, 21?ka) SST reconstructions, is used to compute climate at 140 and 21?ka (reference glaciation). Contrary to the LGM, the ablation almost stopped at 140?ka due to the climatic cooling effect from the large ice sheet topography. Late Saalian SST are simulated using an AGCM coupled with a mixed layer ocean. Compared to the LGM, these 140?ka SST show an inter-hemispheric asymmetry caused by the larger ice-albedo feedback, cooling climate. The resulting Late Saalian ice sheet SMB is smaller due to the extensive simulated sea ice reducing the precipitation. In conclusion, SST are important for the stability and growth of the Late Saalian Eurasian ice sheet. 相似文献