Abstract
In summer 2002, abnormally high-temperature events and associated low soil moisture conditions were observed in Northeast Eurasia. In this study, two regional climate model experiments, one with and the other without soil moisture–atmosphere interaction, were conducted to investigate the role of soil moisture in surface air temperature and precipitation in Northeast Eurasia utilizing the Weather Research and Forecasting (WRF) model. In the experiment without interaction, satellite-based soil moisture was prescribed. Under the persistent mid-tropospheric ridge pattern with prolonged clear skies, both experiments captured the magnitude of the extreme surface air temperature events. A comparison of the model experiments demonstrated that the mid-tropospheric ridge pattern was intensified by dry soil moisture conditions that further increase the surface air temperature. The temporal variability of surface air temperature for the experiments with and without soil moisture–atmosphere interaction reveals the strong coupling of soil moisture to surface air temperature in June–August, raising the possibility that extreme hot temperature events in Northeast Eurasia were strengthened by the soil moisture anomaly. These results also indicate that the impact of soil moisture–atmosphere coupling on surface air temperature varies spatially and temporally, having higher importance for the predictability of extreme high-temperature events in Northeast Eurasia during mid-summer. This also suggests that the performance of the land surface model in simulating appropriate land–atmosphere coupling intensity is a key to evaluating the impact of climate change on extreme heat events in this region.
Highlights
The global mean surface air temperature (SAT) has been increasing steadily since the middle of the 1950s (Hartmann et al 2013)
A mid-tropospheric circulation analysis using the ECMWF reanalysis (ERA)-Interim reanalysis shows that Heat wave (HW) over Northeast Eurasia were triggered by mid-latitude wave trains
Numerical experiments with (CSM) and without (PSM) Soil moisture (SM)–atmosphere interaction were conducted to study the importance of land–atmosphere interaction during the strong HW events in 2002
Summary
The global mean surface air temperature (SAT) has been increasing steadily since the middle of the 1950s (Hartmann et al 2013). In America, Europe, Australia, and Asia, the number of extreme-temperature-related weather events has increased as mean SAT has increased since 1950 (Seneviratne et al 2012). Record-breaking extreme high-temperature events that occurred recently in Europe and North America have focused attention on the. A persistent anticyclonic circulation and blocking are the important atmospheric forcing conditions that cause hot weather events such as heat waves (HWs) in the mid-latitude regions (Dole et al 2011; Schubert et al 2014). In the 2000s, the mid-tropospheric ridge pattern was dominant during June–July–August (JJA) in Northeast Eurasia, providing favorable conditions for HWs (Erdenebat and Sato 2016). Soil moisture (SM) in JJA had declined in this region due to the lack of precipitation, and this possibly intensified the land–atmosphere interaction (Erdenebat and Sato 2016)
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