The northern Eurasia is a region heavily affected by the Arctic polar vortex (APV). Understanding the vegetation responses to anomalous APV in this region is important for dealing with climate change. In this study, we investigated the impacts and mechanism of the anomalous APV phases on the vegetation dynamics in the northern Eurasia. The larger and smaller APV phases correspond to almost opposite atmospheric circulation patterns which result in opposite vegetation responses. The decreased (increased) solar radiation, the enhanced (weakened) northerly winds, together with the decreased (increased) water vapor divergence, caused the decreasing (increasing) of the air temperature, increasing (decreasing) of the precipitation and soil moisture in the study area during the larger (smaller) APV phase. The response of vegetation growth to the APV depends on climate change and vegetation sensitivity to it. In most parts of the study area, vegetation growth was positively associated with air temperature, and hence, vegetation was suppressed (promoted) during the larger (smaller) APV phase. In the northeast of the Caspian Sea (NCS), vegetation growth was sensitive to precipitation. Therefore, the increased (decreased) soil moisture in summer and autumn were responsible for the promoted (suppressed) vegetation growth during the larger (smaller) APV phase.
In this study, we investigated the spatiotemporal variations of border-crossing dust events (DEs), including floating, blowing dust, and dust storms between Mongolia (MG) and Inner Mongolia (IM), China using the ground-based observations from 91 synoptic stations across the Mongolian Plateau during 1977-2018. We defined the intensity of DEs (progressive and recessive) depending on the dust impact area (number of stations affected by dust) by dividing them into three categories: DEs, transported dust events (T-DEs), and severe transported dust events (ST-DEs). The results revealed that during 1977-2018, the frequency of DEs in MG was two times higher than in IM. Simultaneously, the frequency of DEs (dominated by dust storms) increased in MG, whereas IM experienced a decrease in DEs (prevalent types of blowing dust). The T-DEs occurred 2.4 times higher than the ST-DEs over Mongolian Plateau. For the border-crossing DEs, transported dust storms were the dominant type. During 1977-1999, approximately 86% of DEs in IM originated from MG; however, this was decreased to 60% in the 2000s (2000-2018). The intensity of the border-crossing DEs originated from MGand the recessive T-DEs increased significantly since the 2000s, which were more significant than the progressive type.
Tropical cyclone track forecast experiments were conducted using the National Centers for Environmental Prediction Global Forecast System with the initial conditions from three numerical weather prediction centers, to distinguish between tropical cyclone track forecast errors attributable to the initial state uncertainty and those attributable to the model imperfection. The average position error was reduced by replacing the initial conditions from the European Centre for Medium-range Weather Forecasts. The northward recurvature of Lupit (2009) was not reproduced with initial conditions from the Japan Meteorological Agency. It was consistent with the preceding study, indicating sensitivity to the initial state. The sensitivity to the model and the initial state was obtained. For Parma (2009), as opposed to the conclusion of the previous study, where Parma was discovered to be insensitive to the initial state, and the error was assumed to come from the model difference. Insensitivity to the initial vortex structures in the predicted tracks for Parma indicates that the error in the steering flow formed by the environmental field around tropical cyclone contributes to the northward bias.
In October of 2019, Typhoon Hagibis brought abundant rainfall to eastern Japan that caused flooding of the Chikuma River in the northern region of Nagano prefecture. This study simulated the effects of changes in the elevation of the model terrain every 100 or 300 m with a regional meteorological model to understand the cause of the heavy precipitation that accompanied the typhoon in Nagano prefecture and the influence of the heights of mountains on the amount of rainfall. The model reproduced the typhoon track and spatiotemporal distribution of heavy precipitation. Mountains in the northern region of Nagano Prefecture contributed to the heavy precipitation, which increased at an approximately constant rate of 4.4 mm per 100 m increase of elevation. However, the rate of increase was especially large at elevations of 900-1200 m. The correlation of precipitation with topographic height was not as strong in the south as in the north, but the rate of variation was also anomalously high at elevations of 900-1200 m. These elevations roughly corresponded to the level of free convection or to elevations between the level of free convection and the lifted condensation level around the typhoon track.