Tie Yuan

Comprehensive Pattern of Deep Convective Systems over the Tibetan Plateau-South Asian Monsoon Region Based on TRMM Data

AbstractDiurnal and seasonal variation, intensity, and structure of deep convective systems (DCSs; with 20-dBZ echo tops exceeding 14 km) over the Tibetan Plateau–South Asian monsoon region from the Tibetan Plateau (TP) to the ocean are investigated using 14 yr of Tropical Rainfall Measuring Mission (TRMM) data. Four unique regions characterized by different orography are selected for comparison, including the TP, the southern Himalayan front (SHF), the South Asian subcontinent (SAS), and the ocean. DCSs and intense DCSs (IDCSs; with 40-dBZ echo tops exceeding 10 km) occur more frequently over the continent than over the ocean. About 23% of total DCSs develop into IDCSs in the SHF, followed by the TP (21%) and the SAS (15%), with the least over the ocean (2%). The average 20-dBZ echo-top height of IDCSs exceeds 16 km and 9% of them even exceed 18 km. DCSs and IDCSs are the most frequent over the SHF, especially in the westernmost SHF, where the intensity—in terms of strong radar echo-top (viz., 40 dBZ) he...

Regional distribution and diurnal variation of deep convective systems over the Asian monsoon region

Using 12 years of data from the Tropical Rainfall Measuring Mission (TRMM)-based Precipitation Radar (PR), spatial and diurnal variations of deep convective systems (DCSs) over the Asian monsoon region are analyzed. The DCSs are defined by a 20 dBZ echo top extending 14 km. The spatial distribution of DCSs genesis is also discussed, with reference to the National Centers for Environmental Prediction (NCEP) reanalysis data. The results show that DCSs occur mainly over land. They concentrate in south of 20°N during the pre-monsoon season, and then move distinctly to mid-latitude regions, with the most active region on the south slope of the Himalayas during monsoon season. DCSs over the Tibetan Plateau are more frequent than those in central-eastern China, but smaller in horizontal scale and weaker in convective intensity. DCSs in central-eastern China have more robust updrafts and generate more lightning flashes than in other Asian monsoon regions. The horizontal scale of DCSs over the ocean is larger than that over the other regions, and the corresponding minimum infrared (IR) brightness temperature is lower, whereas the convective intensity is weaker. Continental DCSs are more common from noon through midnight, and DCSs over the Tibetan Plateau are more frequently from noon through evening. Oceanic DCSs frequency has a weaker diurnal cycle with dawn maximum, and diurnal variation of DCSs over the tropical maritime continent is consistent with that over the continent.

A Review of Atmospheric Electricity Research in China

The importance of atmospheric electricity research has been increasingly recognized in recent decades. Research on atmospheric electricity has been actively conducted since the 1980s in China. Lightning physics and its effects, as important branches of atmospheric electricity, have received more attention because of their significance both in scientific research and lightning protection applications. This paper reviews atmospheric electricity research based primarily on ground-based field experiments at different regions in China in the last decade. The results described in this review include physics and effects of lightning, rocket-triggered lightning and its physical processes of discharge, thunderstorm electricity on the Tibetan Plateau and its surrounding areas, lightning activity associated with severe convective storms, the effect and response of lightning to climate change, numerical simulation of thunderstorm electrification and lightning discharge, lightning detection and location techniques, and transient luminous events above thunderstorms.

Meteorological Regimes of the Most Intense Convective Systems along the Southern Himalayan Front

AbstractBased on 16 years of Tropical Rainfall Measuring Mission (TRMM) data and NCEP Climate Forecast System Reanalysis data, the most intense convective systems (ICSs) along the southern Himalayan front (SHF) are studied using the multivariate techniques of principal component analysis in T mode and k-means cluster analysis. Three clusters, classified according to the near-surface fields of wind, specific humidity, convective available potential energy, and convective inhibition, correspond to the premonsoon (March–May), the establishment of the monsoon (late May–early June), and the Indian summer monsoon itself (June–September), respectively. The location of ICSs along the SHF is closely related to the establishment of the transport passage from the eastern SHF to the northwestern SHF along the Himalayas. During the premonsoon, the southwesterly wind is weak and moist air from the Bay of Bengal is transported to the eastern SHF, where ICSs are densely distributed. The oceanic southwesterly wind is enha...

Observation of ground potential rise caused by artificially-triggered lightning

Comparative analysis was made between the ground potential rise resulted from an artificially-triggered flash, the channel base current and close magnetic fields. The results indicated that the current peaks of the two strokes in artificially-triggered flash were 41.6 and 29.6 kA. The inferred currents, based on the close magnetic fields, were about 39.8 and 29.1 kA, in agreement with the measured ones. The ground potential rises caused by the two return strokes were about 302.8 and 141.3 kV, respectively. The downtime and half-peak width of the ground potential rise were much longer than that of the corresponding value of the channel base current. Moreover, characteristics of the ground potential rise were studied by using ATP simulation.

Fast electric field change pulses location technique

Using both fast and slow electric field change sensors and field mill, multi-station observations on lightning flashes in Chinese Inland Plateau was conducted during the summer of 2004. All of the stations were synchronized by GPS with a time-resolution of ±50 ns. Using the different time of arrival (DTOA), a lightning radiation location technique, based on the fast electric field change sensor, was developed. Radiation pulses in the five intra-cloud (IC) lightning discharges which occurred on 20th August and cloud-to-ground (CG) lightning discharges which occurred on 16th July were analyzed. The results indicated that the technique developed could effectively locate the lightning radiation sources. Furthermore, the lightning discharges were compared with the Doppler radar data. Results showed that the radiation sources were well associated with the storm development.