In-situ testing study on convection and temperature characteristics of a new crushed-rock slope embankment design in a permafrost region

For the purpose of enhancing air convection and controlling solar radiation, a new crushed-rock slope embankment design combined with a sun-shade measure is proposed. A newly designed embankment was constructed in the Tuotuohe section of the Qinghai-Tibet Railway and a field-testing experiment was carried out to determine its convection and temperature characteristics. The results show that distinct air convection occurred in the crushed-rock layer of the new embankment, especially in cold seasons, which was enhanced when it flowed upwards along the slope. This preliminarily indicated that the new design of the embankment slope was good for reinforcing air convection in the crushed-rock layer. The frequent fluctuations of the convection speed and the environmental wind speed were in good agreement, suggesting that the convection in the crushed rock primarily came from the ambient wind. It was also preliminarily determined that the new embankment had a better cooling effect and sun-shade effect for decreasing the temperature of the embankment slope compared with a traditional crushed-rock slope embankment, and the mean temperature difference between them was up to 1.7 °C. The mean annual temperature at the bottom boundary of the crushed-rock layer was obviously lower than that at the top boundary, and heat flux calculation showed that the shallow soil beneath the embankment slope was weakly releasing heat, all of which indicated that the new embankment slope design was beneficial to the thermal stability of the embankment. This study is helpful in providing some references for improved engineering design and maintenance of roadbeds in permafrost regions.

Some Characteristics of Cumulus Convection over the Tibetan Plateau

The diagnostic model of the cumulus convection proposed by Yanai et al. (1973) was applied to the atmosphere over the Tibetan Plateau, and used to estimate the vertical mass flux, entrainment and detrainment, excess temperature and moisture, liquid water content, and condensation and precipitation rates of highland cloud clusters. The results illustrated that in clouds over the Tibetan Plateau, the water vapor condensation rate, liquid water content, and efficiency of the rain generation process are less than those in the tropics (represented by the Marshall Islands region). Therefore, the condensational latent heat released over the Tibetan Plateau, overall, is much smaller than that in the tropics. The water vapor and liquid water detrainment from shallow nonprecipitating cumulus clouds, and their entrainment into deep cumulus clouds, serve as a growing mechanism for the deep precipitating cumulus towers over the Tibetan Plateau. It should be noted that there is a stronger detrainment of liquid water from cumulus clouds and a stronger re-evaporation rate in environment. The process of the condensation-detrainment-re-evaporation-cnlrainmcnt is repeatedly in progress. It would play an important role in maintaining of cumulus convection on the condition that the supply of moisture is not plentiful over the Tibetan Plateau.The analyses also showed that the cloud mass flux Mc over the Tibetan Plateau is less, and the large-scale average upward motion is much less than those over the Marshall Islands. Stronger compensating downward motion in the cloud environment over the Tibetan Plateau, responsible for the area's strong environmental heating rate Was revealed, and would link to the stability of the South Asian High in summer.

Analysis on Climatic and Synoptic Characteristics of Thunderstorm Gale Weather in Jiangsu

By using observation and sounding data at 68 artificial observatories of Jiangsu Province during 2009- 2013,thunderstorm gale weather and its climatic characteristics in Jiangsu were conducted statistics. The characteristics of some instability indexes and strong convection parameters were analyzed,and environmental parameters of dry and wet thunderstorm gales were contrasted. Results showed that thunderstorm gale in Jiangsu had the characteristics of high occurrence frequency,local feature and stronger intensity. It was mostly accompanied by precipitation,and had obvious seasonal and daily change characteristics. Synoptics analysis showed that temperature-humidity profile characteristics before thunderstorm gale appeared in Jiangsu mainly had four types： bell mouth type,inverted V type,dry unstable type and wet unstable type. Before thunderstorm gale occurred,atmospheric instability was stronger,and some strong convection parameters all had certain instructions. But the forecasts of some thunderstorm gale processes were easy to be missed by only considering CAPE. Environmental condition difference of generating dry and wet thunderstorm gale was that instability of dry thunderstorm gale was stronger than that of wet thunderstorm gale. Before dry thunderstorm gale occurred,environmental temperature at middle-low layer was lower; lapse rate was larger; humidity was small. Before wet thunderstorm gale occurred,environmental temperature was higher; lapse rate was small; humidity was large. At dynamic structure,vertical wind shear at 0- 6 km of dry thunderstorm gale was significantly stronger than that of wet thunderstorm gale.