Statistical Characteristics and Formation Mechanisms of Night Warming Events at Yunding Winter Olympic Stadium in Chongli
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摘要: 本文利用2018年11月至2019年3月、2019年11月至2020年3月期间的自动站资料，对发生在河北崇礼云顶冬奥赛场的夜间增温事件进行了统计分析，并基于地基微波辐射计、激光测风雷达、风廓线仪以及NCEP/NCAR逐6小时再分析资料探讨了夜间增温事件可能的形成机制。研究得出：云顶赛场11月至次年3月，夜间增温事件的发生概率高达76.9%，揭示了冬季夜间增温在云顶赛场是一种常见现象，同时增温次数和增温幅度均随站点海拔高度增加而减小。云顶赛场夜间增温的形成机制可归为四类，分别为垂直风切变造成的逆温层混合增温、焚风增温、整层下沉增温、中低层暖平流增温。其中第二、三、四类增温过程中，增温开始前谷内存在逆温时，谷底增温幅度可能会明显大于山顶，从而导致增温幅度随高度增加而减小。此外，山顶仅受第三类和第四类形成机制影响，而四类增温机制均可引发山谷增温事件，这也是增温事件发生频次随高度升高而明显减少的原因。Abstract: Based on the observed data from automated weather stations during November 2018–March 2019 and November 2019–March 2020 at the Yunding Winter Olympic Stadium in Chongli, Hebei Province, nocturnal warming events at the stadium are statistically analyzed in this paper. Several possible formation mechanisms for these events are then discussed based on microwave radiometer, three-dimensional laser radar and the wind profiler data, and reanalysis data from NCEP/NACR. The results show that the occurrence probability of nocturnal warming events in Yunding Stadium reaches 76.9% from November to the following March, indicating that such warming events are a common phenomenon there. The frequency and amplitude of the warming decrease with increasing altitude. The triggering mechanisms of nocturnal warming events at Yunding Stadium can be classified into four categories: (1) mixed warming in the inversion layer caused by vertical wind shears, (2) Foehn-type warming, (3) whole-layer subsidence warming, and (4) warm advection in the mid and low levels. During the warming process of the second through fourth types, the warming amplitude at the bottom of the valley may be significantly larger than that at the top of the mountain when there is an initial temperature inversion in the valley. In this scenario, warming amplitude decreases with increasing altitude. The warming at the top of the mountain is only affected by the third and fourth types of formation mechanisms, while all four types can trigger warming events in the valley. This explains why the occurrence frequency of warming events decreases with increasing altitude.
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Key words:
- Night warming events /
- Formation mechanisms /
- Foehn warming
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图 1 云顶赛场9个站点分布。红色数字1~6为1~6号自动气象站，“T”为山顶站，“M”为山腰站，“B”为山底站，“R”为微波辐射计，“L”为三维激光雷达，短黑线为雪上技巧赛道，长黑线为坡面障碍技巧赛道
Figure 1. Site distribution of 9 stations at the Genting venue. 1–6 red numbers are automated weather station Nos. 1–6. “T” is hilltop station, “M” is the middle station, B is the bottom station, “R” is microwave radiometer, L is 3D LiDAR, the short black line is Mogul venue, and the long black line is Slopestyle venue
图 2 云顶赛场山底站增温事件个例。Ts为起始温度，Tm为峰值温度，Te为结束温度
Figure 2. Nocturnal warming case at the bottom station at Genting venue. Ts is the temperature at the beginning of warming, Tm is the temperature at the peak time, and Te is the temperature at the end of the warming
图 3 （a）夜间增温起始时刻对应的增温次数；（b）不同增温幅度对应的增温次数；（c）不同增温持续时长对应的增温次数；（d）不同增温持续时长对应的平均增温强度
Figure 3. (a) Warming numbers at different warming start times; (b) warming number under different warming ranges; (c) warming number under different warming durations; (d) average warming magnitude under different warming durations
图 4 （a）云顶各自动气象站（AWS）增温事件总数（蓝色），2°C以上增温事件次数（浅红色），1°C～2°C增温事件次数（绿色）；（b）云顶各站最大增温幅度
Figure 4. (a) Total number of warming events (blue), above 2°C (light red), 1°C–2°C (green) at each automated weather station(AWS) at Genting venue; (b) maximum warming amplitude at each station at Genting venue
图 5 云顶9站增温阶段相对于增温开始前1小时内的（a）平均风速变化（单位：m s−1）和（b）平均露点变化（单位：°C）
Figure 5. The change of (a) the average wind speed (units: m s−1) and (b) dew point temperature (units: °C) of 9 stations at the warming stage compared to within 1 h of the start of warming at Genting venue
图 6 2020年2月8日20时（a）500 hPa风场（单位：m s−1）和温度场（单位：°C），（b）沿41°N局地温度变化平流项和垂直运动项之和的纬向—垂直分布（单位：10−4 K s−1）。黑色三角形表示赛场所在位置
Figure 6. (a) 500 hPa wind field (units: m s−1) and temperature field (units: °C), (b) zonal–vertical distribution of sum of advection and vertical transportation of local temperature change (units: 10−4 K s−1) along 41°N at 2000 BJT on February 8 2020. The black triangle indicates the position of the stadium
图 7 2020年2月8日18:00至9日00:00，1号站（红色实线）、山底站（蓝色实线）（a）温度（T）变化曲线，（b）滤波温度（FT）变化曲线；8日19:00至9日00:00，1号站（红色实线）、山底站（蓝色实线）（c）风速（WS）变化曲线，（d）滤波风速（FWS）变化曲线；（e）8日19:00至9日00:00，1号站与山底站之间空气层的滤波垂直风切变（FWSH）变化曲线
Figure 7. Curves of (a) temperature (T) and (b) filtered temperature (FT) of station 1 (red solid line) and bottom station (blue solid line) from 1800 BJT on February 8 to 0000 BJT on February 9 2020; curves of (c) wind speed (WS) and (d) filtered wind speed (FWS) at station 1 (red solid line) and bottom station (blue solid line) from 1900 BJT on February 8 to 0000 BJT on February 9 2020; (e) filtered wind shear (FWSH) curve of the air layer between station 1 and bottom station from 1900 BJT on February 8 to 0000 BJT on February 9 2020
图 8 2020年2月（a）9日00:00～06:00，1号站（红色实线）、山底站（蓝色实线）温度变化；（b）9日01:30激光雷达径向速度（西北方向300度），黄色区域为地形；（c）9日03:00地面风场（黑色箭头，单位：m s−1）、位温（红色数字，单位：K）和地形高度分布（填色，单位：m）；（d）位温梯度廓线（红色实线为8日20:00，黑色实线为9日02:00，蓝色实线为9日08:00）；（e）Scorer数廓线（黑色实线为9日02:00，蓝色实线为9日08:00）
Figure 8. (a) The change of temperature at station 1 (red solid line) and bottom station (blue solid line) from 0000 BJT to 0600 BJT on February 9 2020; (b) LiDAR radial velocity (300° northwest) at 0130 BJT on February 9 2020, yellow area is terrain; (c) distributions of ground wind (black arrow, units: m s−1), potential temperature (red digits, units: K) and terrain height(shaded, units: m) at 0300 BJT on February 9 2020; (d) potential temperature gradient profile (red solid line: 2000 BJT on February 8 2020, black solid line: 0200 BJT on February 9 2020, blue solid line: 0800 BJT on February 9 2020); (e) scorer number profile (black solid line: 0200 BJT on February 9 2020, blue solid line: 0800 BJT on February 9 2020)
图 9 2020年2月（a）9日00:00～06:00 1号站（红色实线）、山底站（蓝色实线）风速变化；（b）山谷中平均弗劳德数（Frm）时间序列
Figure 9. (a) The change of wind speed at station 1 (red solid line) and bottom station (blue solid line) from 0000 BJT to 0600 BJT on February 9 2020; (b) time series of mean Froude number (Frm) in the valley
图 10 2019年3月（a）7日00:00～06:00温度（T，上图）和露点温度（DPT，下图）的时间序列（红色实线代表1号站，黑色实线代表2号站，蓝色实线代表山底站）；（b）7日00:01～08:01位于北坡中段的微波辐射计反演温度垂直廓线演变（单位：°C）； 7日02时沿41°N（c）局地温度变化垂直运动项（单位：10−4K s−1），（d）局地温度变化垂直运动项与温度平流项之和（单位：10−4K s−1）的纬向－垂直分布；（e）7日00:00~08:00赛场附近风廓线仪垂直速度廓线演变（单位：m s−1）；（f）7日00:00~06:00 1号站（红色实线），2号站（黑色实线），山底站（蓝色实线）位温（θ，上图）、山谷中平均弗劳德数（Frm，下图）时间序列。（c）和（d）中黑色三角形表示赛场所在位置
Figure 10. (a) Time series of temperature (T, above) and dew point temperature (DPT, below) (red solid line is station 1, black solid line is station 2, blue solid line is the bottom station) from 0000 BJT to 0600 BJT on March 7 2019; (b) vertical temperature profile retrieved from microwave radiometer located in the middle part of the north slope (units: °C) from 0001 BJT to 0801 BJT on March 7 2019; zonal－vertical distribution of vertical transmission term of (c) local temperature change (units: 10−4 K s−1), (d) sum of vertical transmission term and temperature advection of local temperature change (units: 10−4 K s−1) along 41°N at 0200 BJT on March 7 2019; (e) evolution of vertical velocity profile of wind profile radar near Genting venue (units: m s−1) from 0000 BJT to 0800 BJT on March 7 2019; (f) time series of potential temperature (θ, above) at station 1 (red solid line), station 2 (black solid line) and bottom station (blue solid line), and mean Froude number (Frm, below) in the valley from 0000 BJT to 0600 BJT on March 7 2019. The black triangles indicate the position of the stadium in (c) and (d)
图 11 2019年2月（a）2日00:00～06:00温度（T，上图）、露点温度（DPT，下图）的时间序列（红色实线代表1号站，黑色实线代表2号站，蓝色实线代表山底站）；（b）2日00:02～08:02位于北坡中段的微波辐射计反演水汽密度垂直廓线演变（单位：g m−3 ）；（c）2日00:00～06:00风速（上图，红色实线代表1号站，黑色实线代表2号站，蓝色实线代表山底站）、风矢量（下图）时间序列；（d）2日02时沿41°N局地温度变化垂直运动项与温度平流项之和（单位：×10−4 K s−1）的纬向－垂直分布，黑色三角形表示赛场所在位置；（e）2日02时 地面风场（黑色箭头，单位：m s−1）、温度（红色数字，单位：°C）和地形高度（填色，单位：m）分布
Figure 11. (a) Time series of temperature (T, above) and dew point temperature (DPT, below) (red solid line is station 1, black solid line is station 2, blue solid line is the bottom station) from 0000 BJT to 0600 BJT on February 2 2019; (b) vertical water vapor density profile retrieved from microwave radiometer located in the middle part of the north slope (units: g m−3) from 0002 BJT to 0802 BJT on February 2 2019; (c) time series of wind speed (above, red solid line is station 1, black solid line is station 2, blue solid line is the bottom station), wind vector (below) from 0000 BJT to 0600 BJT on February 2 2019; (d) zonal－vertical distribution of sum of vertical transport term and advection term of the local temperature change along 41
$ ° $ °N at 0200 BJT on February 2 2019 (units:×10−4 K s−1),the black triangle indicates the position of the stadium; (e) distribution of ground wind (black arrow, units: m s−1) , temperature (red digit, units: °C) and and terrain height(shaded, units: m) at 0200 BJT on February 2 2019 -
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