# Energetics of Boreal Wintertime Blocking Highs around the Ural Mountains

## 北半球冬季乌拉尔山阻塞高压的能量学特征

• Corresponding author: Ning SHI, shining@nuist.edu.cn
• Funds:

Supported by the National Natural Science Foundation of China (42088101, 42025502, 41575057, and 41975063) and Qing Lan Project of Jiangsu Province, China

• doi: 10.1007/s13351-022-1069-7
• Based on the daily Japanese 55-yr reanalysis data, this study analyzes the maintenance mechanism for 53 boreal winter blocking highs around the Ural Mountains (UBHs) during 1958–2018 based on the atmospheric energy budget equations. After decomposing the circulation into background flow, low-frequency anomalies, and high-frequency eddies, it was found that the interaction between the background flow and low-frequency anomalies is conducive to the maintenance of the UBHs. Due to the southwestward gradient in the climatological mean air temperature over the Eurasian continent, it is easy for the air temperature anomalies as well as the wind velocity anomalies in the middle and lower troposphere induced by the UBHs to facilitate the positive conversion of baroclinic energy associated with the background flow into the UBHs. Likewise, the conversion of barotropic energy associated with the background flow is also evident in the upper troposphere, in which the climatological mean westerlies have evident southward gradient to the northwest of Lake Baikal and southwestward gradient over Barents Sea. Note that the conversion of baroclinic energy associated with the background flow is dominant throughout the lifecycle of UBHs, acting as the major contributor to the maintenance of the UBHs. Although transient eddies facilitate maintenance of the UBHs via positive conversion of barotropic energy in the middle and upper troposphere, they hinder the maintenance of UBHs via negative conversion of baroclinic energy in the lower troposphere. The diabatic heating anomalies tend to counteract the local air temperature anomalies in the middle and lower troposphere, which damps the available potential energy of UBHs and acts as a negative contributor to the UBHs.
本文利用日本逐日再分析资料，通过能量收支方程，分析了1958-2018年乌拉尔山附近53个冬季阻塞高压（简称乌阻）的维持机制。在将环流分解为背景场、低频异常和高频瞬变涡动后，本文发现背景场与低频异常场的相互作用有利于乌阻的维持。由于欧亚大陆上的气候平均气温场存在西南向梯度，由乌阻引起的对流层中低层的气温异常和风速异常容易促进与背景场有关的斜压能量向乌阻的转换。类似的是，与背景场有关的正压能量的转换在对流层上层也很明显，这与气候平均西风带在贝加尔湖西北部有明显的向南梯度和巴伦支海有明显的西南向梯度有关。值得注意的是，与背景场有关的斜压能量的转换在乌阻的整个生命史中占主导地位，它是乌阻维持的主要贡献者。高频瞬变涡动虽然通过正压能量的转换促进了乌阻在对流层中上层的维持，但它们通过斜压能量的阻碍着乌阻在对流层低层的维持。与背景场的正贡献相反，非绝热加热对乌阻的维持起着负贡献。非绝热加热异常有抵消对流层中低层局地气温异常的作用，抑制乌阻的有效位能。
• Fig. 1.  Composite evolution of 53 UBHs: Z500 anomalies (left) and T2m anomalies (right). From top to bottom are day −6, −4, −2, 0, 2, 4, and 6. Contour intervals are 40 gpm for Z500 anomalies and 1 K for T2m anomalies. Solid lines indicate the positive anomalies, and dashed lines the negative anomalies. Zero lines are omitted. Bold contours in (a–g) represent +40 gpm of Z500 anomalies. Shading denotes the statistically significant region at the $\alpha _{{\text{FDR}}} = 0.05$ significance level based on the two-tailed Student’s t test. Threshold values for the significance level $p_{{\text{FDR}}}^*$ are 0.005 and 0.004 for the composites of Z500 anomalies and T2m anomalies.

Fig. 2.  As in Fig. 1, but for vertical cross-sections of (a, c) height anomalies and (b, d) air temperature anomalies on day 0. (a) and (b) are along 65°N, and (c) and (d) are along 60°E.

Fig. 3.  Evolution of KE (first column), change of KE (∆KE; second column), APE (third column), and change of APE (∆APE; fourth column) for the 53 composite UBHs. All terms are averaged from surface ground to 100 hPa. The ∆KE and ∆APE are calculated through the centered difference. From top to bottom are day −6, −4, −2, 0, 2, 4, and 6. Contour intervals are 10 m2 s−2 for KE and APE, and 10 m2 s−2 day−1 for their changes.

Fig. 4.  Daily change (m2 s−2 day−1) of the primary terms in Eqs. (2) and (3) for the composite UBHs. All terms are averaged from surface ground to 100 hPa and area-weighted averaged over (a–b) the UB region in which the amplitude of the height anomalies is larger than +40 gpm, and (c–d) the region 20°–90°N, 0°–120°E.

Fig. 5.  Tendency (m2 s−2 day−1) of total energy (∆KE + ∆APE) and each term in Eqs. (2) and (3) for the composite UBHs. First column shows the results averaged from day −6 to day 6, second column from day −6 to day −3, third column from day −2 to day 2, and last column from day 3 to day 6. All terms are averaged from surface ground to 100 hPa and area-weighted averaged over (a–d) the UB region in which the amplitude of the height anomalies is larger than +40 gpm, and (e–h) the region 20°–90°N, 0°–120°E.

Fig. 6.  Vertical profile of the primary terms (10−5 m2 s−3) in Eqs. (2) and (3) for the composite UBHs. These terms are obtained by averaging temporally from day −6 to day 6 and area-weighted averaging over (a) UB region (bounded by +40 gpm contours of height anomalies) and (b) 20°–90°N, 0°–120°E.

Fig. 7.  (a) Extraction of barotropic energy from background flow (CKcli) at 250 hPa (shading) averaged from day −6 to day 6. (b) CKcli_x and (c) CKcli_y are the zonal and meridional components of CKcli, respectively. (d) Extraction of the baroclinic energy from the background flow (CPcli) at 500-hPa level (shading). (e) CPcli_x and (f) CPcli_y are the zonal and meridional components of CPcli, respectively. (g–i) As in (d–f), but at 1000 hPa. Shading interval is 2 × 10−4 m2 s−3. Black contours in (a) represent the climatological-mean zonal wind at 250 hPa (contoured every 4 m s−1, beginning at 4 m s−1) in boreal winter, and in (d) and (g) represent the climatological-mean air temperature (contoured every 4 K, beginning at 234 and 250 K). Arrows in (a–c) are $\boldsymbol{E}$ (m2 s−2) at 250-hPa level, and (d–f) anomalous temperature flux $( - u'T', - v'T')$ (K m s−1) at the corresponding level. Red contours represent +40 gpm of composite height anomalies at the corresponding level to indicate the region where the strong anticyclonic circulation anomalies anchor.

Fig. 8.  As in Fig. 7, but for the generation of APE by anomalous diabatic heating (GPQ) at (a) 700 hPa and (b) 1000 hPa. Contour interval is 2 × 10−4 m2 s−3.

Fig. 9.  (a) Anomalous diabatic heating at 700 hPa which is the sum of five anomalous diabatic heating rate terms. (b) Anomalous large-scale condensation heating rate at 700 hPa. (c) Same as (a), but at 950 hPa. (d) Anomalous longwave radiation heating rate and (e) anomalous vertical diffusion heating rate at 950 hPa. (f–h) Same as (c–e), but at 1000 hPa. Red solid lines represent positive anomalies, and blue dashed lines negative anomalies. Units: K day−1. Shading denotes the statistically significant region at $\alpha _{{\text{FDR}}} = 0.05$ significance level based on the two-tailed Student’s t test.

Fig. 10.  Schematic diagram for the primary energy conversions among different circulation components. The directions of arrows indicate the directions of the energy conversion, while the thickness of the arrows indicate qualitatively the amplitude of the energy conversion. The solid and dashed arrows represent the conversions of APE and KE, respectively. The terms in the energy budget equations which are associated with the primary energy conversions are shown in the brackets.

Fig. 11.  Tendency (m2 s−2) of total energy (∆KE + ∆APE) and each term in Eqs. (2) and (3) for the composite blocking highs over the North Atlantic. All terms are averaged temporally from day −6 to day 6 and spatially from surface ground to 100 hPa and area-weighted averaged over (a) the region with the amplitude of the height anomalies larger than +40 gpm, and (b) the North Atlantic (20°–90°N, 80°W–40°E).

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###### 通讯作者: 陈斌, bchen63@163.com
• 1.

沈阳化工大学材料科学与工程学院 沈阳 110142

## Energetics of Boreal Wintertime Blocking Highs around the Ural Mountains

###### Corresponding author: Ning SHI, shining@nuist.edu.cn;
• 1. Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Key Laboratory of Meteorological Disaster, Ministry of Education, Nanjing University of Information Science & Technology, Nanjing 210044
• 2. College of Atmospheric Science, Nanjing University of Information Science & Technology, Nanjing 210044
• 3. Tibet Institute of Plateau Atmospheric and Environmental Sciences, Tibet Meteorological Bureau, Lhasa 850000
Funds: Supported by the National Natural Science Foundation of China (42088101, 42025502, 41575057, and 41975063) and Qing Lan Project of Jiangsu Province, China

Abstract: Based on the daily Japanese 55-yr reanalysis data, this study analyzes the maintenance mechanism for 53 boreal winter blocking highs around the Ural Mountains (UBHs) during 1958–2018 based on the atmospheric energy budget equations. After decomposing the circulation into background flow, low-frequency anomalies, and high-frequency eddies, it was found that the interaction between the background flow and low-frequency anomalies is conducive to the maintenance of the UBHs. Due to the southwestward gradient in the climatological mean air temperature over the Eurasian continent, it is easy for the air temperature anomalies as well as the wind velocity anomalies in the middle and lower troposphere induced by the UBHs to facilitate the positive conversion of baroclinic energy associated with the background flow into the UBHs. Likewise, the conversion of barotropic energy associated with the background flow is also evident in the upper troposphere, in which the climatological mean westerlies have evident southward gradient to the northwest of Lake Baikal and southwestward gradient over Barents Sea. Note that the conversion of baroclinic energy associated with the background flow is dominant throughout the lifecycle of UBHs, acting as the major contributor to the maintenance of the UBHs. Although transient eddies facilitate maintenance of the UBHs via positive conversion of barotropic energy in the middle and upper troposphere, they hinder the maintenance of UBHs via negative conversion of baroclinic energy in the lower troposphere. The diabatic heating anomalies tend to counteract the local air temperature anomalies in the middle and lower troposphere, which damps the available potential energy of UBHs and acts as a negative contributor to the UBHs.

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