Seamless Detection of Cutoff Low and Preexisting Trough

<p><strong>Cutoff lows are cyclones existing in the upper troposphere developing from precursory preexisting troughs. We introduce a new method to seamlessly detect cutoff lows and even preexisting troughs aiming to improve lead time of meso scale disturbances like tornadoes. The method is based on a geometric character; in this method, a slope defined as the tangential line from a minimum point of each height depression is measured on an isobaric surface. This slope evaluates an intensity and horizontal extension (radius) of each depression. Adopting a mathematical assumption, we successfully achieved to make an algorithm to separate the depression and the local background flow. To remove the background flow enables us to detect both cutoff lows and preexisting troughs seamlessly in reanalysis height fields. So, our method would allow the life cycle to be illustrated continuously from the birth of the cutoff low, that is, from the precursory preexisting trough, and is expected to contribute to the improvement of the lead time for predicting severe weathers. Some further application examples, including tornado accompanying cases, and even for blocking highs, would be shown.</strong></p>

The occurrence of heat waves in Europe and their circulation conditions

The objective of the paper was to characterize the occurrence of heat waves in Europe between 1976 and 2015 and to determine circulation conditions causing their occurrence. The heat waves were recognized as a sequence of at least 5 consecutive hot days. The hot day was defined as a day on which daily maximum air temperature was higher than 95th percentile of all the values in the analyzed period. The conducted research showed an increase in the number of heat waves and their duration in the analyzed period. The longest heat wave occurred in 2010, in Moscow, which lasted 45 days. The most intense changes were observed in the eastern and south-eastern regions. The occurrence of heat waves was mainly connected with positive anomalies of atmospheric pressure at sea level, geopotential height of 500 hPa, and temperature on isobaric surface 850 hPa.

Warm Waves in North-Western Spitsbergen

In this study, weather conditions causing warm waves in north-western Spitsbergen, exemplified by Ny-Ålesund station, were analyzed. Between 1981 and 2010, 536 days with the maximum temperature exceeding 8.3°C (the value of 95 percentile) were selected. 37 warm waves, which altogether lasted 268 days, were identified. A typical feature of pressure pattern causing warm waves was the appearance of positive anomalies of both the sea level pressure and the height of isobaric surface 500 hPa in the Euro-Atlantic sector of the Arctic. This indicates a presence of high-pressure systems in this region. Extremely warm days appeared more often with the circulation from the eastern than the western sector. Longer and warmer heat waves occurring in the last decade of the analyzed period may be considered as a sign of climate warming, which has a significant impact on environment, i.e. reduction in area and thickness of glaciers, reduction of permafrost and snow cover, changes in biodiversity, etc. The increase in the air temperature and more fre-quent occurrence of heat waves may encourage development of tourism in polar areas, po-tentially causing further changes in the environment.

Airborne Measurements of Coastal Jet Transition around Point Conception, California

Low-level winds along the Californian coast during spring and early summer are typically strong and contained within the cool, well-mixed marine boundary layer (MBL). A temperature inversion separates the MBL from the warmer free troposphere. This setup is often represented by a two-layer shallow-water system with a lateral boundary. Near a prominent point such as Point Conception, California, the fast-moving MBL flow is supercritical and can exhibit distinct features including a compression bulge and an expansion fan. Measurements from the University of Wyoming King Air research aircraft on 19 May 2012 during the Precision Atmospheric MBL Experiment (PreAMBLE) captured wind in excess of 14 m s−1 off of Point Conception under clear skies and wind ~2 m s−1 east of San Miguel in the California Bight. A compression bulge was identified upwind of Point Conception. When the flow rounds the point, the MBL undergoes a near collapse and there is a spike in MBL height embedded in the general decrease of MBL height with greater turbulence just downwind that is associated with greater mixing through the inversion layer. Lidar and in situ measurements reveal that transport of continental aerosol is present near the pronounced MBL height change and that there is a complex vertical structure within the Santa Barbara Channel. Horizontal pressure gradients are obtained by measuring the slope of an isobaric surface. Observations of wind and pressure perturbations are able to be linked through a simple Bernoulli relationship. Variation of MBL depth explains most, but not all of the variation of the isobaric surface.

Research on Automobile Aerodynamic Drag Reduction Based on Isobaric Surface of a Blunt Body

This paper focuses on a new method of aerodynamic drag reduction. In this paper numerical simulation method is adopted to investigate the relationship between the aerodynamic drag characteristics of a blunt body and the distribution of total pressure around the body. The study shows that when the shape of a blunt body is modified to be close to its isobaric surface, the pressure drag of the body can be reduced largely while the viscous drag increases slightly, and the summary of the drag gets lower as a result. This conclusion will have profound guiding significance in the aerodynamic shape designing and the aerodynamic drag reduction of an automobile.