Abstract This study investigates the mechanism behind the recent boreal summer circulation trend pattern and associated high surface temperature anomalies over the Russian Far East. This circulation pattern includes a prominent anticyclone over the Kamchatka Peninsula where heat extremes have been trending upward. Observational analysis and numerical model simulations indicate that latent heating anomalies centered over Yakutia, west of Kamchatka Peninsula, can excite this anticyclone and the downstream circulation trend pattern. However, this anticyclone alone is insufficient for generating the anomalously high temperature over the region. Instead, the high temperature emerges when there is an upstream precursor that resembles the Eurasian circulation trend pattern. Warm advection by this upstream circulation initiates a positive temperature anomaly over the Russian Far East, one week prior to the onset of the anticyclone in this region. As this anticyclone develops, the temperature anomalies further intensify by adiabatic warming and shortwave radiative heating. If upstream circulation anomalies are opposite to those of the Eurasian trend pattern, the initial temperature over the Russian Far East is anomalously negative. As a result, the adiabatic warming and shortwave radiative heating within this anticyclonic region are unable to bring the temperature to an extreme condition. These findings indicate that the temperature extremes over the Russian Far East are contributed by a combination of remote and local circulation forcings and provide insights into subseasonal forecasts of heat waves over this region.
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The Role of Latent Heating Anomalies in Exciting the Summertime Eurasian Circulation Trend Pattern and High Surface Temperature
Dynamical mechanisms for the summer Eurasian circulation trend pattern are investigated by analyzing reanalysis data and conducting numerical model simulations. The daily circulations that resemble the Eurasian circulation trend pattern are identified and categorized into two groups based on surface warming signal over central and eastern Europe. In the group with large warm anomaly, the upper-level circulation takes on a wave packet form over Eurasia, and there are enhanced latent heating anomalies centered over the North Sea and suppressed latent heating anomalies over the Caspian Sea. The numerical model calculations indicate that these latent heating anomalies can excite an upper-level circulation response that resembles the Eurasian circulation trend pattern. Additional analysis indicates that trends of these two latent heating centers contribute to the long-term circulation trend. In the weak warm anomaly group, the circulation pattern takes on a circumglobal teleconnection (CGT) pattern, and there is no heating signal that reinforces the circulation. These results indicate that not all CGT-like patterns excite temperature anomalies that are persistent and in phase with the trend pattern, and that quasi-stationary forcings, such as the latent heating anomalies, play an important role in driving the boreal summer circulation anomaly that accompanies the strong and persistent surface temperature signal.
more » « less- Award ID(s):
- 1948667
- NSF-PAR ID:
- 10363293
- Publisher / Repository:
- American Meteorological Society
- Date Published:
- Journal Name:
- Journal of Climate
- Volume:
- 35
- Issue:
- 2
- ISSN:
- 0894-8755
- Page Range / eLocation ID:
- p. 801-814
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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